xvEPA
United States
Environmental Protection
Agency
Policy, Planning,
And Evaluation
(PM-221)
21P-2003.1
December 1990
Policy Options For
Stabilizing Global Climate
Report To Congress
Main Report
1 yf; Printed on Recycled Paper
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POLICY OPTIONS FOR STABILIZING GLOBAL CLIMATE
REPORT TO CONGRESS
Editors: Daniel A. Lashof and Dennis A. Tirpak
United States Environmental Protection Agency
Office of Policy, Planning and Evaluation
December 1990
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This document has been reviewed in accordance with the U.S.
Environmental Protection Agency's and the Office of Management and
Budget's peer and administrative review policies and approved for
publication. Mention of trade names or commercial products does not
constitute endorsement or recommendation for use.
Publisher's Note:
Policy Options for Stabilizing Global Climate. Report to Congress has been
published in three parts:
21 P-2003.1 MAIN REPORT (includes Executive Summary)
21 P-2003.2 EXECUTIVE SUMMARY
21 P-2003.3 TECHNICAL APPENDICES
Those who wish to order the Main Report or Technical Appendices should
inquire at the address below:
Publications Requests
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401 M Street. S.W.
Washington. D.C. 20460
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TABLE OF CONTENTS
Foreword xxiii
Acknowledgements xxv
EXECUTIVE SUMMARY
ABSTRACT 1
INTRODUCTION 2
Purpose of This Study 2
Scope of This Study 2
Current Policy Developments 4
Limitations 4
HUMAN IMPACT ON THE CLIMATE SYSTEM 5
The Greenhouse Gas Buildup 5
The Impact of Greenhouse Gases on Global Climate 8
Natural Climate Variability 10
SCENARIOS FOR POLICY ANALYSIS 10
Defining Scenarios 10
Scenarios with Unimpeded Emissions Growth 12
The Impact of Policy Choices 14
Accelerated Emissions Scenario 14
Scenarios with Stabilizing Policies 19
TECHNOLOGICAL OPTIONS FOR REDUCING GREENHOUSE GAS EMISSIONS 28
Improve Energy Efficiency 30
Improved Transportation Efficiency 30
Other Efficiency Gains ' 30
Carbon Fee 31
Increase Use of Non-Fossil Energy Sources 31
Nuclear Power 31
Solar Technologies 33
Hydro and Geothermal Energy 33
Commercialized Biomass 33
Reduce Emissions from Fossil Fuels 33
Greater Use of Natural Gas 34
Emission Controls 34
Reduce Emissions from Non-Energy Sources 34
CFC Phaseout 34
Reforestation 35
Agriculture, Landfills, and Cement 35
A WIDE RANGE OF POLICY CHOICES FOR THE SHORT AND LONG TERM 37
The Tuning of Policy Responses 38
The Need for an International Response 41
NOTES 44
REFERENCES 44
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CHAPTER I
INTRODUCTION
THE GREENHOUSE EFFECT AND GLOBAL CLIMATE CHANGE 1-1
CONGRESSIONAL REQUEST FOR REPORTS 1-1
Goals of this Study 1-2
Report Format 1-2
THE GREENHOUSE GASES 1-5
Carbon Dioxide 1-5
Methane 1-5
Nitrous Oxide 1-8
Chlorofluorocarbons 1-8
Other Gases Influencing Composition 1-8
PREVIOUS STUDIES 1-8
Estimates of the Climatic Effects of Greenhouse Gas Buildup 1-8
Studies of Future CO2 Emissions 1-9
Studies of the Combined Effects of Greenhouse Gas Buildup Ml
Major Uncertainties 1-12
Conclusions From Previous Studies 1-12
CURRENT DOMESTIC AND INTERNATIONAL ACnVITIES - 1-14
Domestic Research and Policy Activities 1-14
International Activities 1-15
NOTES 1-16
REFERENCES 1-16
CHAPTER II
GREENHOUSE GAS TRENDS
FINDINGS II-l
INTRODUCTION II-2
CARBON DIOXIDE II-2
Concentration History and Geographic Distribution II-2
Mauna Loa II-4
Ice-core Data II-4
GMCC Network II-5
Sources and Sinks II-8
Fossil Carbon Dioxide II-8
Biospheric Cycle II-8
Ocean Uptake < 11-10
Chemical and Radiative Properties/Interactions 11-11
METHANE 11-14
Concentration History and Geographic Distribution 11-14
Sources and Sinks 11-14
Chemical and Radiative Properties/Interactions 11-18
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NITROUS OXIDE 11-18
Concentration History and Geographic Distribution 11-18
Sources and Sinks 11-20
Chemical and Radiative Properties/Interactions 11-21
CHLOROFLUOROCARBONS 11-22
Concentration History and Geographic Distribution 11-22
Sources and Sinks 11-22
Chemical and Radiative Properties/Interactions 11-23
OZONE 11-23
Concentration History and Geographic Distribution 11-23
Tropospheric Ozone 11-23
Stratospheric Ozone 11-25
Sources and Sinks 11-25
Chemical and Radiative Properties/Interactions 11-26
OTHER FACTORS AFFECTING COMPOSITION II-26
Global Tropospheric Chemistry 11-27
The Hydroxyl Radical H-27
Carbon Monoxide 11-27
Nitrogen Oxides 11-28
Stratospheric Ozone and Circulation 11-28
CONCLUSION '. " 11-28
ADDENDUM TO CHAPTER II: RADIATIVE FORCING DIFFERENCES
AMONG THE GREENHOUSE GASES 11-36
NOTES II-40
REFERENCES H-40
CHAPTER IH
CLIMATE CHANGE PROCESSES
FINDINGS III-l
INTRODUCTION III-2
CLIMATE CHANGE IN CONTEXT III-3
CLIMATE FORCINGS HI-6
Solar Luminosity HI-6
Orbital Parameters HI-6
Volcanoes IH-6
Surface Properties IH-7
The Role of Greenhouse Gases HI-7
Internal Variations III-7
PHYSICAL CLIMATE FEEDBACKS HI-7
Water Vapor III-9
Snow and Ice III-9
Clouds III-9
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BIOGEOCHEMICAL CLIMATE FEEDBACKS III-9
Release of Methane Hydrates III-ll
Oceanic Change III-ll
Ocean Chemistry III-ll
Ocean Mixing 111-13
Ocean Biology and Circulation 111-13
Changes in Terrestrial Biota HI-13
Vegetation Albedo 111-13
Carbon Storage 111-14
Other Terrestrial Biotic Emissions 111-14
Summary 111-14
EQUILIBRIUM CLIMATE SENSITIVITY 111-15
THE RATE OF CLIMATE CHANGE 111-17
CONCLUSION 111-19
NOTES 111-19
REFERENCES 111-19
CHAPTER IV
HUMAN ACTIVITIES AFFECTING
TRACE GASES AND CLIMATE
FINDINGS IV-1
INTRODUCTION IV-3
HISTORICAL OVERVIEW OF POPULATION TRENDS IV-3
Global Population Trends IV-3
Population Trends by Region IV-3
Industrialized Countries IV-7
Developing Countries IV-7
ENERGY CONSUMPTION IV-8
History of Fossil-Fuel Use . IV-8
Current Energy-Use Patterns and Greenhouse Gas Emissions IV-12
Emissions by Sector IV-12
Fuel Production and Conversion IV-17
Future Trends IV-17
The Fossil-Fuel Supply IV-19
Future Energy Demand IV-19
INDUSTRIAL PROCESSES IV-19
Chlorofluorocarbons, Halons, and Chlorocarbons IV-22
Historical Development and Uses IV-22
The Montreal Protocol IV-27
Landfill Waste Disposal IV-27
Cement Manufacture IV-28
LAND-USE CHANGE IV-28
Deforestation IV-32
Biomass Burning IV-32
Wetland Loss IV-35
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AGRICULTURAL ACTIVITIES IV-35
Enteric Fermentation In Domestic Animals IV-38
Rice Cultivation IV-38
Use of Nitrogenous Fertilizer IV-42
IMPACT OF CLIMATE CHANGE ON ANTHROPOGENIC EMISSIONS IV-42
NOTES IV-45
REFERENCES IV-46
CHAPTER V
TECHNICAL OPTIONS FOR REDUCING GREENHOUSE GAS EMISSIONS
FINDINGS V-l
INTRODUCTION V-5
The Role of Long-Term and Short-Term Options V-5
The Economics of Control Options V-6
Worldwide Emissions and Control Techniques V-6
Organization of this Chapter V-8
Limitations -. V-10
PART ONE: ENERGY SERVICES V-12
TRANSPORTATION SECTOR V-14
Near-Term Technical Potential in the Transportation Sector V-14
Near-Term Technical Options: Industrialized Countries V-1S
Increase Fuel Efficiency V-15
Alternative Fuels V-25
Strengthen Vehicle Emissions Controls V-26
Enhance Urban Planning and Promote Mass Transit V-27
Near-Term Technical Options: Developing Countries V-27
Increase Fuel Efficiency V-28
Alleviate Congestion and Improve Roads V-29
Promote and Develop Alternative Modes of Transportation V-29
Use Alternative Fuels V-30
Near-Term Technical Options: USSR and Eastern Europe V-30
Long-Term Potential in the Transportation Sector V-31
Urban Planning and Mass Transit V-31
Alternative Fuels V-31
Emerging Technologies V-32
RESIDENTIAL/COMMERCIAL SECTOR V-33
Near-Term Technical Options: Industrialized Countries V-35
Improve Space Conditioning V-35
Use Energy-Efficient Lighting V-41
Use Energy-Efficient Appliances V-41
Near-Term Technical Options: Developing Countries V-44
More Efficient Use ofFuelwood V-44
Use Alternative Fuels V-45
Retrofit Existing Buildings V-46
Build New Energy-Efficient Homes and Commercial Buildings V-46
Near-Term Technical Options: USSR and Eastern Europe , V-46
Long-Term Potential in the Residential/Commercial Sector V-47
be
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INDUSTRIAL SECTOR V-48
Near-Term Technical Options: Industrialized Countries V-50
Accelerate Efficiency Improvements in Energy-Intensive
Industries V-50
Aggressively Pursue Efficiency Improvements in
Other Industries V 51
Increase Cogeneration V-51
Near-Term Technical Options: Developing Countries V-52
Practice Technological Leapfrogging V-52
Develop and Use Alternative Fuels V-53
Increase Industrial Retrofit Programs V-53
Use Energy-Efficient Agricultural Practices V-54
Near-Term Technical Options: USSR and Eastern Europe V-54
Encourage Structural Change V-54
Other Emission Reduction Options V-56
Long-Term Potential in the Industrial Sector V-58
Structural Shifts V-58
Advanced Process Technologies V-58
Non-fossil Energy V-59
PART TWO: ENERGY SUPPLY V-60
FOSSIL-FUEL OPTIONS V-60
Refurbish Existing Powerpiants V-62
Pursue Clean Coal Technologies V-62
Increase Use of Cogeneration V-63
Substitute Natural Gas for Coal V-63
Natural Gas Use At Existing Powerpiants V-63
Advanced Gas-Fired Combustion Technologies V-64
Factors Affecting Use of Natural Gas V-64
Methods of Increasing Gas Resources V-67
Employ Emissions Control Technologies V-67
NOX Controls V-68
CO2 Controls V-68
Consider Emerging Electricity Generation Technologies V-70
Fuel Cells V-70
Magnetohydrodynamics V-70
BIOMASS OPTIONS V-70
Improve Efficiency of Direct Firing Methods V-71
Improve Efficiency of Charcoal Production V-71
Promote Anaerobic Digestion Technology V-73
Promote Use of Gasification V-73
Improve Technologies to Convert Biomass to Liquid Fuels V-74
Methanol from Biomass V-74
Ethanolfrom Biomass V-74
Biomass Oils as Fuel V-76
SOLAR ENERGY OPTIONS V-76
Promote Solar Thermal Technology V-76
Parabolic Troughs V-77
Parabolic Dishes V-77
Central Receivers V-77
Solar Ponds V-77
Improve Solar Photovoltaic Technology V-77
Crystalline Cells V-80
Thin-Film Technologies V-80
Multi-Junction Technologies V-81
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ADDITIONAL PRIMARY RENEWABLE ENERGY OPTIONS V-81
Expand Hydroelectric Generating Capacity V-81
Industrialized Countries V-81
USSR and Eastern Europe V-82
Developing Countries V-82
Reduce Cost of Wind Energy V-83
Exploit Geothermal Energy Potential V-83
Research Potential for Ocean Energy V-85
NUCLEAR POWER OPTIONS V-85
Enhance Safety and Cost Effectiveness of Nuclear Fission Technology V-85
Promote Research and Development of Nuclear Fusion Technology V-90
ELECTRICAL SYSTEM OPERATION V-91
Reduce Energy Losses During Transmission and Distribution V-91
Enhance Storage Technologies V-92
Pumped Storage V-92
Batteries V-92
Compressed Air Storage V-93
Superconducting Magnetic Energy Storage V-93
HYDROGEN OPTIONS V-93
PART THREE: INDUSTRY V-95
CFCs AND RELATED COMPOUNDS V-95
Expand the Use of Chemical Substitutes V-97
Employ Engineering Controls V-97
Use Substitutes for CFC-Produced Materials V-98
METHANE EMISSIONS FROM LANDFILLS V-99
Increase Methane Recovery V-99
Employ Recycling and Resource Recovery V-100
Reduce Demand for Cement V-101
PART IV: FORESTRY V-102
FOREST DISTURBANCE AND CARBON EMISSIONS V-102
DEFORESTATION V-103
TECHNICAL CONTROL OPTIONS V-108
Forestry Strategy I: Reduce Sources of Greenhouse Gases V-113
Option 1: Substitute Sustainable Agriculture for
Swidden Forest Practices V-113
Option 2: Reduce the Frequency, Interval, and Scale
of Forest and Savannah Consumed by Biomass
Burning as a Management Practice V-121
Option 3: Reduce Demand For Other Land Uses That
Have Deforestation as a Byproduct V-121
Option 4: Increase Conversion Efficiencies of
Technologies That Use Fuelwood V-122
Option 5: Decrease Production of Disposable Forest Products V-123
Forestry Strategy II: Maintain Existing Sinks of Greenhouse Gases V-124
Option 1: Conserve Standing Primary and Old-Growth
Forests as Stocks of Biomass Offering a
Stream of Economic Benefits V-124
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Option 2: Slow Deforestation by Introducing Natural
Forest Management of Little-Disturbed and
Secondary Tropical Forests V-124
Option 3: Conserve Tropical Forests by Developing
Markets and Extractive Reserves for Non-Timber Products V-125
Option 4: Improve Forest Harvesting Efficiency V-126
Option 5: Prevent Loss of Soil Carbon Stocks by Slowing Erosion
in Forest Systems During Harvest and from Overgrazing
by Livestock V-126
Forestry Strategy III: Expand Sinks of Greenhouse Gases V-126
Option 1: Increase Forest Productivity: Manage Temperate
Natural Forests for Higher Yields V-126
Option 2: Increase Forest Productivity: Plantation Forests V-130
Option 3: Expand Current Tree Planting Programs in the
Temperate Zone V-132
Option 4: Reforest Surplus Agricultural Lands V-132
Option 5: Reforest Urban Areas V-138
Option 6: Pursue Afforestation for Highway Corridors V-140
Option 7: Reforest Tropical Countries V-140
Option 8: Restore Degraded Lands V-142
Option 9: Increase Soil Carbon Storage by Leaving Slash
After Harvest and Expanding Agroforestry V-142
Obstacles to Large-Scale Reforestation in Industrialized Countries V-145
Obstacles to Reforestation in Developing Countries V-146
Comparison of Selected Forestry Technical Control Options V-148
PART FIVE: AGRICULTURE V-152
RICE CULTIVATION V-152
Existing Technologies and Management Practices Affecting
Methane Production V-154
Nature of Rice Production System V-154
Fertilization With Organic Matter V-154
Disposition of Crop Residues V-154
Type of Rice Variety Planted V-154
Fertilizer Use V-155
Emerging Technologies V-155
Research Needs and Economic Considerations V-157
NITROGENOUS FERTILIZER USE AND SOIL EMISSIONS V-157
Existing Technologies and Management Practices Affecting
Production of Nitrous Oxide V-158
Type of Fertilizer V-158
Fertilizer Application Rate V-158
Crop Type V-158
Timing of Fertilizer Application V-158
Placement of Fertilizer V-159
Water Management V-159
Tillage Practices and Herbicide Use V-159
Legumes as a Nitrogen Source V-159
Technologies that Improve Fertilization Efficiency V-159
Nitrification Inhibitors V-159
Reduced Release Rate V-159
Coatings V-159
Emerging Technologies V-159
Alternative Agricultural Systems V-160
Alternative Agriculture and Nitrous Oxide V-160
Sustainable Agriculture and Land Conversion V-160
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Research Needs and Economic Considerations . V-161
ENTERIC FERMENTATION IN DOMESTIC ANIMALS V-161
Management Practices Affecting Methane Emissions from Livestock V-162
Livestock System Productivity V-164
Diet V-164
Nutritional Supplements V-164
Feed Additives V-165
Methane from Manure V-165
Emerging Technologies V-166
Research Needs and Economic Considerations V-166
NOTES V-167
REFERENCES V-167
CHAPTER VI
THINKING ABOUT THE FUTURE
FINDINGS VI-1
INTRODUCTION VI-2
APPROACH TO ANALYZING FUTURE EMISSIONS VI-2
Production VI-3
Consumption VI-5
SCENARIOS FOR POLICY ANALYSIS VI-7
Scenarios with Unimpeded Emissions Growth VI-10
Scenarios with Stabilizing Policies and Accelerated Emissions VI-10
ANALYTICAL FRAMEWORK VI-15
Energy Module VI-15
Industry Module VI-18
Agriculture Module VI-18
Land-Use and Natural Source Module VI-18
Ocean Module VI-18
Atmospheric Composition and Temperature Module VI-18
Assumptions VI-19
Population Growth Rates VI-19
Economic Growth Rates VI-19
Oil Prices VI-19
Limitations VI-19
SCENARIO RESULTS VI-20
Energy Production and Use VI-20
End-Use Consumption VI-21
Primary Energy Supply VI-23
Greenhouse Gas Emissions From Energy Production and Use VI-27
Comparison to Previous Studies VI-29
Industrial Processes VI-36
Halocarbon Emissions VI-36
Emissions From Landfills and Cement VI-38
Changes in Land Use VI-38
Agricultural Activities VI-39
Total Emissions VI-41
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Atmospheric Concentrations ' . . VI-47
Global Temperature Increases VI-49
Comparison with General Circulation Model Results VI-54
Relative Effectiveness of Selected Strategies VI-54
SENSITIVITY ANALYSES VI-62
Assumptions About the Magnitude and Timing of Global Climate
Stabilization Strategies VI-62
No Participation by the Developing Countries VI-62
Delay in Adoption of Policies VI-63
Assumptions Affecting Rates of Technological Change VI-65
Availability of Non-Fossil Technologies VI-65
Assumptions About Climate Sensitivity and Timing VI-67
Sensitivity of the Climate System VI-67
Rate of Heat Diffusion VI-67
Biogeochemical Feedbacks VI-70
Ocean Circulation . VI-70
Methane Feedbacks VI-70
Combined Feedbacks VI-73
CONCLUSIONS VI-73
NOTES VI-76
REFERENCES VI-76
CHAPTER VII
POLICY OPTIONS
FINDINGS VII-1
INTRODUCTION VII-3
GOALS VIM
CRITERIA FOR SELECTING POLICY OPTIONS VII-4
COMPLEMENTARY STRATEGIES TO REDUCE GREENHOUSE GAS EMISSIONS .. . VII-6
The Cost Issue VII-8
IMPLICATIONS OF POLICY CHOICES AND TIMING VII-9
IMPORTANCE AND IMPLICATIONS OF A LONG-TERM PERSPECTIVE VII-10
INTERNALIZING THE COST OF CLIMATE CHANGE RISKS VII-13
Evidence of Market Response to Economic Incentives: Energy Pricing VII-13
Financial Mechanisms to Promote Energy Efficiency VII-16
Creating Markets for Conservation VII-18
Limits to Price-Oriented Policies VII-19
REGULATIONS AND STANDARDS VII-22
Existing Regulations that Restrict Greenhouse Gas Emissions VII-22
Regulation of Chlorofluorocarbons VII-22
Energy Efficiency Standards VII-23
Air Pollution Regulations VII-25
Solid Waste Management VII-26
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Utility Regulation VII-28
Existing Regulations that Encourage Emissions Reductions VII-29
Tree Planting VII-29
Other Incentives/Disincentives VII-32
RESEARCH AND DEVELOPMENT VII-32
Energy Research and Development VH-33
Global Forestry Research and Development VII-38
Research to Eliminate Emissions of CFCs VII-38
INFORMATION AND TECHNICAL ASSISTANCE PROGRAMS VII-39
CONSERVATION EFFORTS BY FEDERAL AGENCIES VII-40
STATE AND LOCAL EFFORTS VII-42
PRIVATE SECTOR EFFORTS VIMS
ADDENDUM TO CHAPTER VII: ANALYSIS OF SPECIFIC PROPOSALS
FOR REDUCING GREENHOUSE GAS EMISSIONS VII-47
POTENTIAL OPTIONS TO REDUCE GREENHOUSE GAS EMISSIONS VII-47
Tree Planting VII-47
U.S. DOE Energy Efficiency Initiatives VII-47
U.S. DOE Renewable Energy Initiatives VII-48
U.S. DOE Appliance Standards VII-48
Clean Air Act Provisions VII-48
Landfill Regulations VII-49
Montreal Protocol and CFC Phaseout VII-49
How These Options May Reduce Emissions to Current Levels VII-49
ADDITIONAL POLICY OPTIONS VII-49
Tax Initiatives VII-52
Transportation Taxes VII-52
Carbon Taxes VII-52
Non-Tax Initiatives VII-52
Tighter Landfill Regulations VII-52
Increase in Tree Planting VII-52
Implications of Additional Policy Initiatives VII-52
IMPLICATIONS IF ONLY CO2 IS CONSIDERED VII-54
NOTES VII-56
REFERENCES VII-57
CHAPTER VIII
INTERNATIONAL COOPERATION TO REDUCE GREENHOUSE GAS EMISSIONS
FINDINGS VIII-1
INTRODUCTION VIII-2
THE CONTEXT FOR POLICIES INFLUENCING GREENHOUSE GAS
EMISSIONS IN DEVELOPING COUNTRIES VIII-2
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Economic Development and Energy Use VIII-4
Oil Imports, Capital Shortages, and Energy Efficiency VIII-8
Greenhouse Gas Emissions and Technology Transfer VIII-11
STRATEGIES FOR REDUCING GREENHOUSE GAS EMISSIONS VIII-11
International Lending and Bilateral Aid VIII-13
U.S. Bilateral Assistance Programs VIII-13
Policies and Programs of Multilateral Development Banks VIII-15
New Directions VIII-20
REDUCING GREENHOUSE GAS EMISSIONS IN THE USSR
AND EASTERN EUROPE VIII-20
U.S. LEADERSHIP TO PROMOTE INTERNATIONAL COOPERATION VIII-22
Restricting CFCs to Protect the Ozone Layer VIII-22
International Efforts to Halt Tropical Deforestation VIII-23
Ongoing Efforts Toward International Cooperation VIII-24
CONCLUSION VIII-27
NOTES VIII-28
REFERENCES VIII-28
APPENDICES
APPENDIX A: MODEL DESCRIPTIONS
APPENDIX B: IMPLEMENTATION OF THE SCENARIOS
APPENDIX C: SENSnTVITY ANALYSES
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LIST OF FIGURES
EXECUTIVE SUMMARY
1 Concentration of CO2 at Mauna Loa Observatory and CO2 Emissions
From Fossil-Fuel Combustion 3
2 Greenhouse Gas Contributions to Global Warming .. . 6
3 Impact of CO2 Emissions Reductions on Atmospheric Concentrations 9
4 Atmospheric Concentrations 16
5 Realized Warming: No Response Scenarios 17
6 Accelerated Emissions Cases: Percent Increase in Equilibrium
Warming Commitment 20
7 Stabilizing Policy Strategies: Decrease in Equilibrium Warming
Commitment 23
8 Rapid Reduction Strategies: Additional Decrease in Equilibrium
Warming Commitment 25
9 Realized Warming: No Response and Stabilizing Policy Scenarios 27
10 Primary Energy Supply by Type 32
11 Increase in Realized Warming Due to Global Delay in Policy Options 40
12 Share of Greenhouse Gas Emissions by Region 42
13 Increase in Realized Warming When Developing Countries
Do Not Participate 43
CHAPTER I
1-1 Concentration of CO2 at Mauna Loa Observatory and CO2 Emissions
From Fossil-Fuel Combustion 1-6
1-2 Impact of CO2 Emissions Reductions on Atmospheric Concentrations 1-7
CHAPTER H
2-1 Greenhouse Gas Contributions to Global Wanning II-3
2-2 Carbon Dioxide Concentration II-6
2-3 CO2 Atmospheric Concentrations by Latitude II-7
2-4 The Carbon Cycle II-9
2-5 Gas Absorption Bands 11-12
2-6 Methane Concentration H-15
2-7 Current Emissions of Methane by Source II-16
2-8 Nitrous Oxide Concentration 11-19
2-9 Temperature Profile and Ozone Distribution in the Atmosphere 11-24
2-10 Contribution to Radiative Forcing 11-37
CHAPTER III
3-1 Surface Air Temperature HI-4
3-2 Oxygen Isotope Record From Ice Cores in Greenland III-5
3-3 Carbon Dioxide and Temperature Records From Antarctic Ice Core IH-5
3-4 Oxygen Isotope Record From Deep Sea Sediment Cores IH-5
3-5 Global Energy Balance III-8
3-6 Equilibrium Temperature Changes From Double CO2 HI-10
3-7 Greenhouse Gas Feedback Processes IH-12
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CHAPTER IV
4-1 Regional Contribution to Greenhouse Forcing, 1980s IV-4
4-2 Regional Population Growth, 1750-1985 IV-5
4-3 Global Energy Demand by Type, 1950-1985 IV-9
4-4 CO2 Emissions Due to Fossil-Fuel Combustion IV-10
4-5 Global Commercial Energy Demand by Region IV-11
4-6 1985 Sectoral Energy Demand by Region IV-13
4-7 Potential Future Energy Demand IV-21
4-8 Historical Production of CFC-11 and CFC-12 IV-24
4-9 CFC-11 and CFC-12 Production/Use for Various Countries IV-26
4-10 CO2 Emissions From Cement Production, 1950-1985 IV-30
4-11 Cement Production in Selected Countries, 1951-1985 IV-31
4-12 Net Release of Carbon From Tropical Deforestation, 1980 IV-33
4-13 Wetland Area and Associated Methane Emissions IV-37
4-14 Trends in Domestic Animal Populations, 1890-1985 IV-39
4-15 Rough Rice Production, 1984 IV-40
4-16 Rice Area Harvested, 1984 IV-41
4-17 Nitrogen Fertilizer Consumption, 1984/1985 IV-44
CHAPTER V
5-1 Current Contribution to Global Warming V-7
5-2 Global Energy Use by End Use V-13
5-3 Components of Transportation Energy Use in the OECD, 1985 V-16
5-4 U.S. Residential/Commercial Energy Use V-34
5-5 Average Efficiency of Powerplams Using Fossil Fuel, 1951-1987 V-61
5-6 Strategies for Improving Efficiency of Biomass Use V-72
5-7 Basic Solar Thermal Technologies V-78
5-8 Photovoltaic Electricity Costs V-79
5-9 Capital Costs for Nuclear Power V-89
5-10 Industrial Process Contribution to Global Warming V-96
5-11 Movement of Tropical Forest Lands Among Stages of
Deforestation and Potential Response Options V-106
5-12 Estimates of Annual Deforestation, 1981-1985 and Most Recent V-109
5-13 Cost Curves for Potential Large-Scale Afforestation in the U.S V-137
5-14 Alley Cropping in Machakos, Kenya V-144
5-15 Contribution of Agricultural Practices to Global Warming V-153
CHAPTER VI
6-1 Total U.S. Energy Consumption per GNP Dollar, 1900-1985 VI-4
6-2 U.S. Consumption of Basic Materials VI-6
6-3 Population by Region VI-12
6-4 Actual and Projected U.S. Coal Production VI-14
6-5 Structure of the Atmospheric Stabilization Framework VI-16
6-6 Geopolitical Region of Climate Analysis VI-17
6-7 End-Use Energy Demand by Region VI-22
6-8 Primary Energy Supply by Type VI-24
6-9 Share of Primary Energy Supply by Type VI-25
6-10 Energy Demand for Synthetic Fuel Production VI-26
6-11 Emissions of Major CFCs VI-37
6-12 CO2 Emissions from Tropical Deforestation VI-40
6-13 CO2 Emissions by Type VI-44
6-14 CO2 Emissions by Regions VI-45
6-15 CH4 Emissions by Type VI-46
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6-16 Atmospheric Concentrations VI-48
6-17 Realized and Equilibrium Wanning VI-52
6-18 Relative Contribution to Warming, 1985 to 2100 VI-55
6-19 Stabilizing Policy Strategies: Decrease in Equilibrium
Warming Commitment VI-56
6-20 . Rapid Reduction Strategies: Additional Decrease in Equilibrium
Wanning Commitment VI-58
6-21 Accelerated Emissions Cases: Percent Increase in Equilibrium
Warming Commitment VI-60
6-22 Increase in Realized Warming When Developing Countries
Do Not Participate VI-64
6-23 Increase in Realized Warming Due to Global Delay in Policy Options VI-66
6-24 Availability of Non-Fossil Energy Options VI-68
6-25 Impact of Climate Sensitivity on Realized Warming VI-69
6-26 Increase in Realized Warming Due to Rate of Ocean Heat Uptake VI-71
6-27 Increase in Realized Wanning Due to Change in Ocean Circulation VI-72
6-28 Increase in Realized Warming Due to Methane Feedbacks VI-74
6-29 Increase in Realized Warming Due to Change in Combined Feedbacks VI-75
CHAPTER VII
7-1 U.S. Energy Consumption by Fuel Share VII-11
7-2 Atmospheric Response to Emissions Cutoff VII-12
7-3 Energy Intensity Reduction, 1973-1985 • VII-14
7-4 U.S. Electricity Demand and Price VII-17
7-5 Cost of Driving Versus Automotive Fuel Economy VII-21
7-6 U.S. Carbon Monoxide Emissions VII-27
7-7 Changes in U.S. Renewable Energy R&D Priorities Over Time VII-35
7-8 Cost of Potential Residential Conservation in Michigan by 2000 VII-44
CHAPTER VIII
8-1 Greenhouse Gas Emissions by Region VIII-3
xix
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LIST OF TABLES
EXECUTIVE SUMMARY
1 Approximate Reductions in Anthropogenic Emissions Required to Stabilize
Atmospheric Concentrations at Current Levels 8
2 Overview of Major Scenario Assumptions 13
3 Trace Gas Emissions 15
4 Scenario Results for Realized and Equilibrium Warming 18
5 Examples of Policy Responses by the Year 2000 29
CHAPTER I
1-1 Approximate Reductions in Anthropogenic Emissions Required to Stabilize
Atmospheric Concentrations at Current Levels 1-5
CHAPTER II
2-1 Trace Gas Data 11-29
2-2 Radiative Forcing for a Uniform Increase in Trace Gases From
Current Levels 11-13
2-3 Global Warming Potential for Key Greenhouse Gases 11-38
CHAPTER IV
4-1 Regional Demographic Indicators IV-6
4-2 Emission Rate Differences by Sector IV-14
4-3 End-Use Energy Consumption Patterns for the Residential/Commercial
Sectors IV-16
4-4 Carbon Dioxide Emission Rates for Conventional and Synthetic Fuels IV-18
4-5 Estimates of Global Fossil-Fuel Resources IV-20
4-6 Major Halocarbons: Statistics and Uses IV-23
4-7 Estimated 1985 World Use of Potential Ozone-Depleting Substances IV-25
4-8 Refuse Generation Rates in Selected Cities IV-29
4-9 Land Use: 1950-1980 IV-34
4-10 Summary Data on Area and Biomass Burned IV-36
4-11 Nitrous Oxide Emissions by Fertilizer Type IV-43
CHAPTER V
5-1 Key Technical Options by Region and Time Horizon V-9
5-2 High Fuel Economy Prototype Vehicles V-17
5-3 Actual Fuel Efficiency for New Passenger Cars V-19
5-4 Summary of Energy Consumption and Conservation Potential With
Major Residential Equipment V-43
5-5 Reduction of Energy Intensity in the U.S. Basic Materials
Industries V-49
5-6 Energy Intensities of Selected Economies V-55
5-7 Innovation in Steel Production Technology, Selected Countries V-57
5-8 Total U.S. Gas Reserves and Resources V-66
5-9 CO2 Scrubber Costs Compared to SO2 Scrubber Costs V-69
5-10 Estimates of Worldwide Geothermal Electric Power Capacity Potential V-84
5-11 Capacity of Direct Use Geothermal Plants in Operation -1984 V-86
xx
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5-12 Geothermal Powerplants On-Line as of 1985 V-87
5-13 Estimates of Release of Carbon to Atmosphere from Top 10
Deforestation Countries, 1980 and 1989 V-104
5-14 Recent Estimate of CO2 Emissions from Biomass Burning in Amazonia V-107
5-15 Summary of Major Forestry Sector Strategies for Stabilizing
Global Climate V-110
5-16 Potential Forestry Strategies and Technical Options to Slow
Climate Change V-114
5-17 Comparison of Land Required for Sustainable Versus Swidden
Agricultural Practices V-118
5-18 Potential Carbon Fixation and Biomass Production Benefits from
Representative Agroforestry Systems V-119
5-19 Assessment of Potential Reductions in Greenhouse Gases from
Large-Scale Substitution of Agroforestry for Traditional Swidden
and Monocultural Agriculture V-120
5-20 Value of One Hectare of Standing Forest in Amazonian Peru Under
Alternative Land Uses V-127
5-21 Effects of Adaptive Forest Management Activities on Production of
Merchantable Volume for a Northern Hardwood Forest Under
Two Climate Change Assumptions V-129
5-22 Productivity Increases Attributable to Intensive Plantation
Management V-133
5-23 Summary of Major Tree Planting Programs in the U.S V-134
5-24 Estimates of CRP Program Acreage Necessary to Offset CO2
Production from New Fossil Fuel-Fired Electric Plants, 1987-%,
by Tree Species or Forest Type V-136
5-25 Estimates of Forest Acreage Required to Offset Various CO2
Emissions Goals V-139
5-26 Costs of Afforestation: Stand Establishment and Initial Maintenance V-147
5-27 Comparison of Selected Forest Sector Control Options: Preliminary
Estimates V-149
5-28 Overview of Three Social Forestry Projects Proposed to Offset CO2
Emissions of a 180-MW Electric Plant in Connecticut V-151
5-29 Water Regime and Modern Variety Adoption for Rice Production in
Selected Asian Countries V-156
5-30 Average Meat Yield Per Animal V-163
CHAPTER VI
6-1 Overview of Major Scenario Assumptions VI-8
6-2 Economic Growth Assumptions VI-11
6-3 Key Global Indicators VI-28
6-4 Comparison of No Response Scenarios and NEPP VI-30
6-5 Comparison of Stabilizing Policy Scenarios and ESW VI-31
6-6 Summary of Various Primary Energy Forecasts for the Year 2050 VI-33
6-7 Comparison of Energy-Related Trace-Gas Emissions Scenarios VI-35
6-8 Trace Gas Emissions VI-42
6-9 Comparison of Estimates of Trace-Gas Concentrations in
2030 and 2050 VI-50
6-10 Scenario Results for Realized and Equilibrium Warming VI-53
CHAPTER VII
7-1 Energy Intensity of Selected National Economies, 1973-85 VII-15
7-2 Payback Periods in Year for Appliances, 1972-1980 VII-20
7-3 Comparison of Energy Efficiencies of Regulated Appliances VII-24
xxi
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7-4 Cogeneration Facilities VII-30
7-5 Erodible Acreage Available to Offset CO2 Emissions from
Electricity Production VII-31
7-6 Government Efficiency Research and Development Budgets in OECD Member
Countries, 1986 VII-34
7-7 Additional Energy Technology R&D Expenditures Needed to be Prepared to
Control CO2 Emissions VII-37
7-8 Federal Energy Expenditures and Cost Avoidance, FY 1985-FY 1987 VII-41
7-9 Emissions Reductions from Current Policy Initiatives by 2000 VII-50
7-10 Emission Estimates for 1987 and 2000 VII-51
7-11 Emission Reductions from Potential Tax Initiatives for the Year 2000 VII-53
CHAPTER VIII
8-1 1985 Population and Energy Use Data from Selected Countries VIII-5
8-2 Efficiency of Energy Use in Developing Countries: 1984-1985 VIII-6
8-3 Potential for Electricity Conservation in Brazil VIII-8
8-4 Net Oil Imports and Their Relation to Export Earnings for Selected
Developing Countries, 1973-1984 VIII-9
8-5 Annual Investment in Energy Supply as a Percent of Annual Total
Public Investment (Early 1980s) VIII-10
8-6 World Bank Estimate of Capital Requirements for Commercial Energy in
Developing Countries, 1982-1992 VIII-10
8-7 U.S. AID Forestry Expenditures by Region VIII-14
8-8 Gross Disbursements of Development Banks in Forestry Projects in
1986-1988 VIII-16
8-9 World Bank Energy Sector Loans in 1987 VIII-16
8-10 Energy-Related Expenditures of Multilateral and Bilateral Aid Institutions .... VIII-18
8-11 World Bank Energy Conservation Projects: Energy Sector Management
Assistance Program (ESMAP) Eerngy Efficiency Initiatvies VIII-19
8-12 Energy Use in the Soviet Union and Eastern Europe VIII-21
8-13 Countries Responsible for Largest Share of Tropical Forest Deforestation VIII-25
xxii
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FOREWORD
I am pleased to transmit the attached Policy Options for
Stabilizing Global Climate, the second of two reports on global
climate change prepared in response to a Congressional ,request in
the Fiscal Year 1987 Continuing Resolution Authority. The first
report assessed the potential health and environmental effects of
climate change on the U.S. This report examines a range of
possible response options and estimates their potential for
reducing or limiting emissions of greenhouse gases on a global
scale.
The magnitude of the effort required to produce this report
was greater than many had anticipated. The lead authors and many
other contributors have nevertheless created an impressive and
scholarly work that sprovides a valuable foundation for the
additional research and analysis that will be needed for
determining future policy actions. I would like to congratulate
all those involved.
The report is one of the first to take a comprehensive and
global approach, covering all sectors and all greenhouse gases, in
the analysis of policy options for reducing greenhouse"gases. It
carefully describes the types of gases involved, their physical
sources, and the level of emissions by source as well as geographic
location. Based on a wide range of policy options, from energy
efficiency to new methods of rice cultivation, it presents possible
future scenarios of greenhouse gas emissions to the year 2100
depending on the level of response as well as many other
independent factors.
The results demonstrate that greenhouse gas emissions can be
effectively reduced. However, the report acknowledges that the
actual size of these reductions will depend upon a great many
factors, not the least of which are the accuracy of the data and
the inherent limitations of the models employed in the analysis.
Economic growth, population growth, and the extent to which
countries respond to climate change are among the many other
uncertainties.
Another key limitation of the report is that comprehensive
estimates of the costs of achieving these reductions are not
provided. This was a conscious decision based on the time and
resources available for preparing the report, as well as the
interest of several groups in undertaking their own cost analyses.
Cost assessments have been conducted over the last year, both
within EPA and among other agencies. Additional studies are
underway that will improve our information on this important topic.
Since the final draft report was released approximately a year
ago it has undergone a thorough and rigorous review. Several
additional reports on responses to global climate change have also
been issued which have provided a further basis for judging the
ndii
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quality and thoroughness of the report. These include reports by
the Intergovernmental Panel on Climate Change, the Office of
Technology Assessment, the National Research Council, and others.
Remarkably, the final report has required only relatively minor
improvements to meet the standards set by our reviewers as well as
other experts studying the issue.
I believe this is not only due to the excellent effort devoted
to the preparation of this report, but it is also a reflection of
the broad consensus that exists concerning the nature and potential
of the options we have for addressing the problem of global climate
change.
Unfortunately, there is no silver bullet among them. Choosing
among the wide range of options is thus going to be the toughest
challenge we now face.
Assistant Administrator
Office of Policy, Planning and Evaluation
xriv
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ACKNOWLEDGEMENTS
This report would not have been possible without the tireless efforts of the primary chapter authors:
Executive Summary Daniel Lashof
Dennis Tirpak
Chapter I. Introduction Joel Scheraga
Irving Mintzer
Chapter II. Greenhouse Gas Trends Inez Fung
Michael Prather
Chapter III. Climate Change Processes Daniel Lashof
Alan Robock
Chapter IV. Human Activities Affecting Trace Gases and Climate Barbara Braatz
Craig Ebert
Chapter V. Technical Options for Reducing Greenhouse Gas Emissions Paul Schwengels
(Energy Services)
Barry Solomon (Energy Services and Supply)
Craig Ebert (Energy Supply)
Joel Scheraga (Energy Supply)
Michael Adler (Renewable Energy)
Dilip Ahuja (Biomass)
John Wells (Haolocarbons)
Stephen Seidel (CFCs)
Kenneth Andrasko (Forestry)
Lauretta Burke (Agriculture)
Chapter VI. Thinking About the Future Daniel Lashof
Leon Schipper
Barry Solomon
Chapter VII. Policy Options Alan Miller
Chapter VIII. International Cooperation to Reduce Greenhouse Gas Emissions Alan Miller
Jayant Sathaye
Appendix A. Model Descriptions William Pepper
Parvadha Suntharalingam
Appendix B. Implementation of the Scenarios Craig Ebert
Appendix C. Sensitivity Analyses Craig Ebert
Parvadha Suntharalingam
XXV
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Model integration was coordinated by William Pepper and Craig Ebert, with assistance from Rossana
Florez. Models and/or analysis were prepared by Irving Mintzer; Jayant Sathaye, Andrea Ketoff, Leon
Schipper, and Sharad Lele; Klaus Frohberg and Phil Vande Kamp; Richard Houghton; Berrien Moore, Chris
Ringo, and William Emmanuel; Michael Prather; Ivar Isaksen, Terje Berntsen, and Sverre Solberg; and Anne
Thompson.
Document integration was coordinated by Craig Ebert and Barbara Braatz. Editorial assistance was
proved by Susan MacMillan. Technical, graphics, and typing assistance was provided by Julie Anderson,
Patricia Baldridge, Karen Borza, Margo Brown, Donald Devost, Courtney Dinsmore, Katie Donaldson, Michael
Green, Amy Kim, Judy Koput, Cheryl LaBrecque, Nathaniel Watkins, Cynthia Whitfield, Donna Whitlock,
and Karen Zambri.
Literally hundreds of other people have contributed to this report, including the organizers and
attendants at four workshops sponsored by the U.S. Environmental Protection Agency to gather information
and ideas, and dozens of formal and informal reviewers. We would like to thank this legion for their interest
in this project and apologize for not doing so individually. Particularly important comments were provided
by, among other, Thomas Bath, Deborah Bleviss, Gary Breitenbeck, William Chandler, Jim Elkins, Robert
Friedman, Howard Geller, James Hansen, Ned Helm, Tony Janetos, Stan Johnson, Julian Jones, Michael
Kavanaugh, Andrew Lacis, Michael MacCracken, Elaine Matthews, Chris Neme, William Nordhaus, Steven
Piccot, Steven Plotkin, Marc Ross, Stephen Schneider, Paul Steele, Pieter Tans, Thomas Wigley, Edward
Williams, and Robert Williams.
This word was conducted within U.S. EPA's Office of Policy Analysis, directed by Richard
Morgenstern, within the Office of Policy, Planning and Evaluation, administered by Linda Fisher. Technical
support was provided by the Office of Research and Development, administered by Eric Brethauer.
xxvi
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EXECUTIVE SUMMARY
ABSTRACT
The composition of Earth's atmosphere
is changing. The concentration of carbon
dioxide, the most important greenhouse gas
accumulating in the atmosphere, has risen
25% since pre-industrial times. Significant
increases in the concentrations of methane,
chlorofluorocarbons, and nitrous oxide have
also been observed. Present emission trends
would lead to a continuing buildup of these
gases in the atmosphere. Although there is a
good deal of uncertainty about the timing,
magnitude, and regional distribution of climate
change that would occur if these trends are
not reversed, significant global warming over
the next century - from 0.2 to 0.5 degrees C
per decade ~ is predicted by global climate
computer models.
Drastic cuts in emissions would be
required to stabilize atmospheric composition.
Because greenhouse gases, once emitted,
remain in the atmosphere for decades to
centuries, stabilizing emissions at current
levels would allow the greenhouse effect to
continue to intensify for more than a century.
Emissions of carbon dioxide might have to be
reduced by 50-80% to hold its concentration
constant.
While it is not possible to stabilize
greenhouse gas concentrations immediately,
world-wide implementation of measures to
reduce emissions would decrease the risks of
global wanning, regardless of uncertainties
about the response of the climate system.
Scenario analyses indicate that if no policies to
limit greenhouse gas emissions were
undertaken, the equivalent of a doubling of
carbon dioxide would occur between 2030 and
2040, and the Earth might be committed to a
global wanning of 2-4°C (3-7°F) by 2025 and
3-6°C (4-10°F) by 2050. Early application of
existing and emerging technologies designed
to, among other things, increase the efficiency
of energy use, expand the use of non-fossil
energy sources, reverse deforestation, and
phase out chlorofluorocarbons could reduce
the global warming commitment in 2025 by
about one-fourth, and the rate of climate
change during the next century by at least
60%. A global commitment to rapidly
reducing greenhouse gas emissions might be
able to stabilize the concentrations of these
gases by the middle of the next century,
perhaps limiting global warming to less than
2°C (3°F). The economic and technological
analyses needed to determine the specific
actions that would achieve such a large
reduction at minimum cost have not yet been
done. The economic feasibilities, costs,
benefits, and other social and economic
implications of such actions are not known.
This study identifies a wide range of potential
options and actions which appear promising
based on available technical information.
Further detailed study is required to determine
the effectiveness and economic implications of
each option.
There is a wide range of policy choices
available that have the technical potential to
reduce greenhouse gas emissions. Many also
appear to be consistent with other economic,
development, environmental, and social goals.
Any effective strategy will require a variety of
policies aimed at reducing emissions from
many sources and obtaining the cooperation of
many countries. Although a full assessment of
the costs and benefits of each option has not
been conducted, a number of potential actions
or policies geared toward increasing energy
efficiency, accelerating research and
development, and reversing deforestation
would have important benefits in addition to
reducing greenhouse gas emissions. Decisions
on the timing of U.S. policy responses should
be based on a consideration of the multiple
benefits and costs that might result from each
policy, the additional commitment to warming
caused by delaying action, and the role that
U.S. leadership could play in promoting
international cooperation to limit changes in
climate variables to acceptable levels.
Much of the report's discussion
necessarily cites information derived from U.S.
experience and data because of the limitations
of information about other regions. However,
the report's discussion of emissions, potential
response options, and their implications is
from a world-wide perspective. Because of
limitations in our knowledge, particularly
about economic factors in many regions
outside of the U.S., the report's findings and
conclusions must be viewed as indicative and
preliminary.
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Policy Options for Stabilizing Global Climate
INTRODUCTION
The composition of the Earth's
atmosphere is changing (see Figure 1).
Although the specific rate and magnitude of
future climate change are hard to predict, in
the absence of policy responses the observed
trends and projected increases in the
atmospheric concentrations of greenhouse
gases are likely to significantly alter the global
climate during the next century. "Greenhouse"
gases (carbon dioxide, methane, chlorofluoro-
carbons, and nitrous oxide, among others) in
the atmosphere absorb heat that radiates from
the Earth's surface and emit some of this heat
downward, wanning the climate. Without this
"greenhouse effect," the Earth would be about
30°C (60°F) colder than it is today. Human
activities are now increasing the atmospheric
concentrations of greenhouse gases on a global
basis, thus intensifying the greenhouse effect.
The rate of greenhouse gas buildup during the
next century will depend heavily on future
patterns of economic and technological
development, which are, in turn, influenced by
policies of local, state, national, and
international institutions.
Purpose of This Study
To better define the potential effects of
global climate change and identify the options
that are available to limit human-caused
climate change, Congress asked the U.S.
Environmental Protection Agency (U.S. EPA)
to undertake two studies. Congress directed
that in one of these studies U.S. EPA focus on
"the potential health and environmental effects
of climate change." A companion report, The
Potential Effects of Global Climate Change on
the United States (Smith and Tirpak, 1989),
responds to that request. The second request
was that U.S. EPA undertake --
An examination of policy options
that if implemented would stabilize
current levels of atmospheric
greenhouse gas concentrations. This
study should address the need for
and implications of significant
changes in energy policy, including
energy efficiency and development of
alternatives to fossil fuels; reductions
in the use of CFCs; ways to reduce
other greenhouse gases such as
methane and nitrous oxide; as well
as the potential for and effects of
reducing deforestation and
increasing reforestation efforts.
This study responds to that request by
examining the impact of a wide variety of
policy options under a range of possible
economic and technologic developments. The
analysis shows that while it is not possible to
stabilize greenhouse gas concentrations
immediately, a global commitment to rapidly
reduce greenhouse gas emissions might be able
to stabilize their concentrations by the middle
of the next century and even reduce
concentrations toward current levels by the
end of the next century. While humans may
have already committed the earth to significant
climate change during the next century, efforts
undertaken now to limit the buildup of
greenhouse gases in the atmosphere can
dramatically reduce the rate and ultimate
magnitude of such change.
Scope of This Study
The scope of this study is necessarily
global and the time horizon is more than a
century. To address this complex problem the
Agency enlisted the help of leading experts in
the governmental, non-governmental, and
academic research communities. Five work-
shops, which were attended by over 300
people, were held to gather information and
ideas about factors affecting atmospheric
composition and about response options
related to greenhouse gas emissions from
agricultural and forestry practices, industrial
processes, and energy consumption and supply,
as well as the extent to which developing
countries may be contributing to potential
global wanning. Experts at NASA, the U.S.
Department of Energy (U.S. DOE), and the
U.S. Department of Agriculture (U.S. DOA)
contributed to this effort.
Based on the outcome of this
information-gathering process, U.S. EPA
developed an integrated analytical framework
to organize the data and assumptions required
to calculate (1) emissions of radiatively and
chemically active gases, (2) concentrations of
greenhouse gases, and (3) changes in global
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Executive Summary
FIGURE I
CONCENTRATION OF CO2 AT MAUNA LOA OBSERVATORY
AND C02 EMISSIONS FROM FOSSIL-FUEL COMBUSTION
(a)
o
0
a
o>
4*
<5
a.
360
350
340
330
n
£
o
c 320
o
O
cT
o
(b)
310
6
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Policy Options for Stabilizing Global Climate
temperatures. This framework is highly
simplified, as its primary purpose is to rapidly
scan a broad range of policy options in order
to test their general effectiveness in reducing
atmospheric concentrations of greenhouse
gases. This analysis represents the first
attempt to quantify the relationship between
certain underlying forces (e.g., population
growth, economic growth, and technological
change) and emissions of all of the important
greenhouse gases. By using this framework we
were able to estimate how assumed changes in
these underlying forces would affect the
composition of the atmosphere and global
temperatures. It should be kept in mind that
the uncertainties in deriving temperature
changes from changes in greenhouse gas
concentrations are substantial. In constructing
this framework, we used the results of more
sophisticated models of individual components
as a basis for our analysis (see Appendix A for
more discussion of this framework). While we
believe that this framework generally reflects
the current state of scientific knowledge, there
are important limitations.
Current Policy Developments
The primary objective of this report is
to begin discussion of policies that could be
adopted by the global community to respond
to climate change concerns. We have not
specifically focused on policies for the United
States, but current developments in U. S.
policy are an important part of the background
information for readers of this report.
Since this study was completed, many
countries have already made commitments to
goals or actions that help to reduce net
greenhouse gas emissions. In the United
States the focus has been on actions that also
have benefits for reasons other than climate
change. Because of these other benefits, such
actions can be justified despite the very
substantial scientific and economic
uncertainties associated with climate change
issues.
The 1990 Clean Air Act Amendments
contain provisions to attain and maintain
National Ambient Air Quality Standards by
regulating emissions of volatile organic
compounds, nitrogen oxides, and carbon
monoxide. The Amendments will not only
produce cleaner air, but also significantly affect
greenhouse gases or their precursors. Major
reductions of sulfur dioxide to 10 million tons
below 1980 levels and of nitrogen oxides to 2
million tons below projected year 2000 levels
will reduce greenhouse gas emissions by
greatly encouraging energy efficiency. Phasing
out CFCs, carbon tetrachloride, methyl
chloroform, and hydrochlorofluorocarbons
(HCFCs) in accordance with the Montreal
Protocol and the Clean Air Act will
substantially reduce emissions of greenhouse
gases as well as protect the stratospheric ozone
layer.
The President's proposed program for
planting a billion trees a year will produce
substantial benefits for wildlife, soil
conservation, and energy saving, as well as
directly take up CO2 from the atmosphere.
The increase in the Federal gasoline tax
enacted in the Budget Reconciliation Act of
1990 will reduce emissions by encouraging
energy efficiency in road transportation.
Increased funding requested in the FY 1991
budget for research and development in solar
and renewable energy and energy conservation
will be important in identifying and developing
technologies and practices that will allow us to
meet our energy needs in environmentally
efficient ways. New energy saving appliance
standards promulgated by the Department of
Energy will increase energy conservation and
reduce demand.
The U. S. has committed to specific
policy actions without specifying the future
level of aggregate emissions that will be
realized. Several other countries have
committed to quantitative, aggregate, future
emission goals but have not specified the
policy actions that will ensure achievement of
those goals. The U. S. actions may have
effects on emissions as substantial as the target
emissions levels being promised for future
achievement by a number of other countries.
Limitations
' The analytical framework used in this
report attempts to incorporate some
representation of the major processes that will
influence the rate and magnitude of
greenhouse warming during the next century
within a structure that is reasonably
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Executive Summary
transparent and easy to manipulate. In so
doing we recognize a number of major
limitations.
• Because of the scope of the analysis, it
was not possible to come up with
comprehensive estimates of the costs or
benefits associated with each policy option.
We have instead relied on available
engineering cost estimates and judgment to
select options that appear to be the most
attractive. Subsequent studies, currently under
way, will provide more detailed economic
analysis for the next few decades on a country-
by-country basis. In particular i there are
serious limitations in economic activity, cost,
and emission factor data for regions1 outside of
the U.S., particularly for the developing
countries. Thus, the implications of each
policy option for such regions are preliminary
and uncertain. The policy options presented
herein should therefore be viewed as examples
of what could be done to reduce the buildup of
greenhouse gases, not as recommendations of
what should be done.
• Forecasting rates of economic growth
and technological change over decadal time
periods is difficult, if not inherently
impossible. For this reason, the scenarios of
this report should not be viewed as forecasts
or predictions. While we believe that the
scenarios presented in this report provide a
useful basis for analyzing policy options, our
alternative assumptions may not adequately
reflect the plausible range of possibilities. For
example, we have assumed that aggregate
economic growth rates will generally decline
over time from the levels assumed for 1985-
2000; this may not be the case. Similarly,
assumed improvements in energy-consuming
and -producing technology in the No Response
and/or the Stabilizing Policy scenarios (see
Table 2 for a description) may prove to be too
optimistic or pessimistic.
• The use of simplified models also
implies that some potentially important
processes and interactions cannot be
accounted for. These include the
macroeconomic implications of the projected
changes in climate and the options designed to
limit these changes. Similarly, capital markets
are not explicitly considered. This is
particularly significant with regard to
developing countries, as it is unclear if they
will be able to obtain the capital needed to
develop the energy supplies assumed in some
of the scenarios. Additionally, the simplified
atmospheric chemistry and ocean models
employed may not adequately reflect the
underlying processes, particularly as climate
changes. Similarly, the parametric model used
to relate global temperature increases to
concentrations of greenhouse gases may not be
valid for extrapolations beyond 6°C.
• Behavioral changes that might be
stimulated by climate change, by policies, or by
individual choices to limit climate change also
have not been considered. Individual
decisionmakers will take actions to adapt to
any changes in climatic conditions. The
nature, costs, and benefits of these actions and
behavioral changes are not adequately defined
and understood. For example, future
population levels will have an -important
impact on greenhouse gas emissions, but
reduced rates of population growth have not
been analyzed as a policy response.
HUMAN IMPACT ON THE
CLIMATE SYSTEM
The Greenhouse Gas Buildup
Many greenhouse gases are currently
accumulating in the atmosphere. The most
important, in terms of past and current
contribution to radiative forcing, is carbon
dioxide (COj), followed by methane (CH4),
chlorofluorocarbons (CFCs), and nitrous oxide
(N2O) (see Figure 2 and Box 1). Carbon
dioxide, a fundamental product of burning
fossil fuels (coal, oil, and gas), is also released
as a result of deforestation. There are many
sources of methane, including rice cultivation,
enteric fermentation in animals, releases
during coal mining and natural gas production
and distribution, waste decomposition in
landfills, as well as many natural sources.
CFCs, however, are produced only by the
chemical industry. The sources of nitrous
oxide are not well characterized, but most are
probably related to soil processes; the most
important anthropogenic sources are fertilizer
use and various land-use changes such as
deforestation and savanna burning.
Greenhouse gases of natural origin include
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Policy Options for Stabilizing Global Climate
FIGURE 2
GREENHOUSE GAS CONTRIBUTIONS TO GLOBAL WARMING
Other (8%)
CFC-11&-12
(8%)
CFC-11&-12
(14%)
Figure 2. Based on estimates of the increase in the concentration of each gas during the specified
period. Other includes additional CFCs, halons, changes in ozone, and changes in stratospheric water
vapor. The other category is quite uncertain. (Sources: 1880-1980: Ramanathan et al., 1985; 1980s:
Hansen et al., 1988.)
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Executive Summary
Box 1. Concept of Global Warming Potential
Throughout this Report, relative contributions to climate change by greenhouse gas
are calculated based on changes in atmospheric concentrations of each gas. These
concentration changes alter the radiative balance of the climate system. The scientific
community has in the past calculated contributions to radiative forcing using estimated
changes in atmospheric concentrations over some time interval (e.g., 10 years); this approach
is reflected in the left-hand figure below (and also in Figure 2) based on Hansen et al.
(1988). When discussing the various greenhouse gases in a policy context, however, there
is often a need for policymakers to have some simple means of estimating the relative
impacts of emissions of each greenhouse gas to affect radiative forcing, and hence climate,
without the complex, time-consuming task of determining the impacts on atmospheric
concentrations. Since this Report was first prepared, several researchers have developed
indices that translate the level of emissions of the various greenhouse gases into a common
metric in order to compare the climate-forcing effects of the gases. The index has been
called the Global Warming Potential (GWP), and is defined as the time integrated
commitment to climate forcing from the instantaneous release of 1 kilogram of a trace gas
expressed relative to that from 1 kilogram of carbon dioxide. For purposes of illustrating
this concept, we have used the GWP methodology developed by the Intergovernmental
Panel on Climate Change for an integration period of 100 years (IPCC, 1990) to express
1985 emissions on a CO2-equivalent basis in order to compare the results to the
methodology used by Hansen et al. (1988); see right-hand figure below. These two
approaches produce very different results since Hansen et al. (1988) base their approach on
the radiative forcing effects of estimated changes in atmospheric concentrations from 1980-90,
while the use of GWPs measures the radiative forcing effects of emissions for a single year
(Le., 1985) over a 100-year time frame (see Addendum to Chapter II for a complete
discussion of this concept). This report uses the Hansen et al. (1988) methodology when
discussing relative current contributions of different gases and source categories. Use of the
IPCC or other alternative integrating methodologies would change the values of these shares
somewhat.
CONTRIBUTION TO RADIATIVE FORCING
By Greenhouse Gas By Greenhouse Gas
Concentrations Emissions on a CO2-Equivalent Basis
Oth»r(10%)
CH4(19%r
1980s 1985
* GWP values 6om IPCC <199Q) wew wwi and apptied to jk>baiemissk>B estimates from
the RCW scenario.
-------
Policy Options for Stabilizing Global Climate
water vapor and all of those listed above
except the chlorofluorocarbons.
Stabilizing emissions of greenhouse
gases at current levels will not stabilize
concentrations. Once emitted, greenhouse
gases remain in the atmosphere for decades to
centuries. As a result, if emissions remained
constant at 1985 levels, the greenhouse effect
would continue to intensify for more than a
century. Carbon dioxide concentrations might
reach 440-500 parts per million (ppm) by 2100,
compared with about 350 ppm today, and
about 290 ppm 100 years ago (see Figure 3).
Nitrous oxide concentrations would probably
increase by about 20%; methane
concentrations might remain roughly constant.
Drastic cuts in emissions would be
required to stabilize atmospheric
composition. This assertion is based on the
fact that these gases remain in the atmosphere
for a very long time and. that constant
emissions at current levels would lead to a
continuing increase in concentrations.
Emissions of CO2, for example, would have to
be reduced by 50-80% to stabilize atmospheric
concentrations (see Table 1). Even if all
anthropogenic emissions (i.e., emissions caused
by human activities) of CO2, CFCs, and N2O
were eliminated, the concentrations of these
gases would remain elevated for decades. It
would take more than 50 years, and possibly
more than a century, following a cut-off in
CO2 emissions for the oceans and other sinks
to absorb enough carbon to reduce the
atmospheric concentration of CO2 halfway
toward its pre-industrial value.
The Impact of Greenhouse Gases
on Global Climate
Uncertainties about the impact of the
greenhouse gas buildup on global climate
abound. These uncertainties are not about
whether the greenhouse effect is real or
whether increased greenhouse gas
concentrations will raise global temperatures.
Rather, the uncertainties concern the ultimate
magnitude and timing of warming and the
implications of that warming for the Earth's
climate system, environment, and economies.
TABLE 1
Approximate Reductions in
Anthropogenic Emissions Required to
Stabilize Atmospheric
Concentrations at Current Levels
GAS
REDUCTION
REQUIRED
Carbon Dioxide 50-80%
Methane 10-20%
Nitrous Oxide 80-85%
Chlorofluorocarbons 75-100%
Carbon Monoxide (CO) Freeze
Oxides of Nitrogen (NOX) Freeze
The magnitude of future global wanning
will depend, in part, on how geophysical and
biological feedbacks enhance or reduce the
warming caused by the additional infrared
radiation absorbed by increasing concen-
trations of greenhouse gases. The ultimate
global average temperature increase that can
be expected from a specific increase in the
concentrations of greenhouse gases can be
called the "climate sensitivity." This parameter
provides a convenient index for the magnitude
of climate change that would be associated
with different scenarios of greenhouse gas
buildup. (In this report we use a doubling of
the concentration of CO2 from pre-industrial
levels, or the equivalent from increases in the
concentrations of a number of greenhouse
gases, as the benchmark case.)
Estimating the impact of increasing
greenhouse gas concentrations on global
climate has been a focus of research within the
atmospheric science community for more than
a decade. This research shows that:
• If nothing else changed in the Earth's
climate system except a doubling of CO2 (or
the equivalent in other greenhouse gases),
average global temperature would rise 1.2-
-------
Executive Summary
FIGURE 3
IMPACT OF C02 EMISSIONS REDUCTIONS
ON ATMOSPHERIC CONCENTRATIONS
500
475
450
425 -
&
• 400
375 -
350 -j
325
1985 2000
2100
Figure 3. The response of atmospheric CO2 concentrations to arbitrary emissions scenarios, based
on two one-dimensional models of ocean CO2 uptake. The emissions scenarios are relative to
estimated 1985 levels of 5.9 billion tons of carbon per year. (Sources: Hansen et al., 1984; Lashof,
1989; Siegenthaler, 1983.)
-------
Policy Options for Stabilizing Global Climate
• Increased global temperatures would
raise atmospheric levels of water vapor and
change the vertical temperature profile, raising
the ultimate global warming caused by a
doubling of CO2. Changes in snow and ice
cover are also expected to enhance warming.
There is strong consensus that if nothing other
than these factors changed in the Earth's
climate system, the global temperature would
rise by 2-4°C.
• The impact of changes in clouds on
global warming is highly uncertain. General
circulation models now generally project that
the global warming from doubling CO2 could
cause changes in clouds that would either
enhance this wanning or diminish it somewhat.
• A variety of other geophysical and
biogenic feedbacks exist that have generally
been neglected in global climate models. For
example, future global warming has the
potential to increase emissions of carbon from
northern latitude reservoirs in the form of
both methane and carbon dioxide, and to alter
uptake of CO2 by the biosphere and the
oceans. Modeling analyses attempting to
incorporate feedbacks result in a wider range
of possible warming, i.e., 1.5 to 5.5° C, for an
initial doubling of CO2.
Global warming of just a few degrees
would represent an enormous change in
climate. The difference in mean annual
temperature between Boston and Washington
is only 3.38C, and the difference between
Chicago and Atlanta is 6.7°C. The total global
wanning since the peak of the last ice age,
18,000 years ago, was only about 5°C. That
change transformed the landscape of North
America, shifting the Atlantic ocean inland by
about one hundred miles, creating the Great
Lakes, and changing the composition of forests
throughout the continent.
The potential future impacts of climate
change are difficult to predict and are beyond
the scope of this report. Although global
temperature change is used as an indicator of
climate change throughout this report, it is
important to bear in mind that regional
changes in temperature, precipitation, storm
frequency, and other variables will determine
the environmental and economic impacts of
climate change. Predictions of such regional
changes in climate are highly uncertain at this
time.
Sensitivity analyses can be undertaken to
estimate potential impacts, as was done in the
companion volume, The Potential Effects of
Global Climate Change on the United States.
The collective findings of that study suggest
that the climatic changes associated with a
global warming of roughly 2-4°C would result
in
a world different from the world
that exists today. . . . Global
climate change could have
significant implications for natural
ecosystems; for where and how we
farm; for the availability of water
to irrigate crops, produce power,
and support shipping; for how we
live in our cities; for the wetlands
that spawn our fish; for the
beaches we use for recreation; and
for all levels of government and
industry (Smith and Tirpak, 1989,
p. xxx).
Natural Climate Variability
Because of long-period couplings
between different components of the climate
system, for example, between ocean and
atmosphere, the Earth's climate would still
vary without being perturbed by any external
influences. This natural variability could act
to add to, or subtract from, any human-made
warming. Natural emissions and variations
contribute significantly to climate change.
Climate variations from glacial to interglacial
periods have been caused naturally.
Controlling anthropogenic greenhouse gas
emissions will not prevent natural climate
change.
SCENARIOS FOR POLICY
ANALYSIS
Defining Scenarios
Defining scenarios that encompass more
than a century is a daunting task. While this
is an eternity for most economists and
planners, it is but a moment for geologists.
And indeed, decisions made in the next few
10
-------
Executive Summary
decades, about how buildings are constructed,
electricity is generated, and cities are laid out,
for example, will have an impact on the
climate in 2100 and beyond. Decisions about
what kinds of automobiles and other industrial
products to produce and how to produce them
will also have a profound impact. These
choices, which will affect the amount and type
of fuel we use to travel, to heat and light our
homes and offices, and to run our factories,
will influence the magnitude of greenhouse gas
emissions for many years.
To explore the climatic implications of
such policy and investment decisions; we have
constructed six scenarios of future patterns of
economic development, population growth,
and technological change. These scenarios
stan with alternative assumptions about the
rate of economic growth and policies that
influence emissions, such as those affecting
levels of future energy demand, land-clearing
rates, CFC production, etc. These scenarios
are intended to be internally consistent
pictures of how the world may evolve in the
future. They are not forecasts and they do not
bracket the full range of possible futures.
Instead, they were chosen to provide a basis
for evaluating strategies for stabilizing the
atmosphere in the context of distinctly
different, but plausible, conditions.
Specifically, the policy scenarios
discussed in this report are meant to stimulate
further study. They do not constitute
conclusions about what would be the most
feasible and cost-effective strategies or plans
for responding to climate change and should
not be interpreted as such. What they do
show is that no single measure or limited set
of a few measures would be an adequate
response to climate change. They also show
that there are a great many potential options,
each one of which alone would have only a
modest impact. Finally, they show that much
more work is needed to evaluate the physical,
social, and economic implications of each
policy option and to identify the least socially
and economically disruptive approaches.
Deciding on an overall climate change
response strategy will be extremely difficult
taking into account all of the unknowns and
uncertainties. The need for world-wide
cooperation in a strategy complicates the
policy-making problem. However, the U.S.
has many potential options from which, if their
implications are well understood, it can
develop a response that is likely to be both
feasible and effective. It is already proceeding
in this manner by immediately implementing a
series of actions that can be justified for other
reasons or by their benefits even in the face of
the uncertainties. However, there are
uncertainties even about how far those actions
which the U.S. is already taking should be
pursued. Not all levels of energy efficiency,
tree planting, or increased levels of R & D are
likely to produce benefits in excess of their
costs. All countries in their specific economic
contexts need to consider the costs, benefits,
and uncertainties of taking various actions.
It should be noted that these scenarios
have not been updated to reflect the current
status of the Montreal Protocol as
strengthened by the London Agreement to
completely phase out CFCs, halons, carbon
tetrachloride, and methyl chloroform, and to
encourage limits on HCFCs.
Two scenarios explore alternative
pictures of how the world may evolve in the
future assuming that policy choices allow
unimpeded growth in emissions of greenhouse
gases (these are referred to as the "No
Response" scenarios). One of these scenarios,
called a Rapidly Changing World (RCW),
assumes rapid economic growth and techno-
logical change; the other, called the Slowly
Changing World (SCW), represents a more
pessimistic view of the evolution of the world's
economies. A variant of the RCW scenario,
Rapidly Changing World with Accelerated
Emissions (RCWA), assumes that efficiency
improvements occur more gradually and that
policies tend to favor increased greenhouse gas
emissions. Two additional scenarios (referred
to as the "Stabilizing Policy" scenarios) stan
with the same economic and demographic
assumptions as the RCW and SCW, but
assume a world in which nations have adopted
policies to limit anthropogenic emissions of
greenhouse gases. These scenarios are called
the Slowly Changing World with Stabilizing
Policies (SCWP) and the Rapidly Changing
World with Stabilizing Policies (RCWP). In
addition, a variant of the RCWP assumes
more Rapid Reductions in greenhouse gas
emissions (RCWR). In all of the scenarios it
11
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Policy Options for Stabilizing Global Climate
is assumed that the ' key national and
international political institutions evolve
gradually, with no major upheavals. An
overview of the scenario assumptions is
provided in Table 2.
The analysis for this study included a
detailed examination of energy demand for the
year 2025. We chose this date because,
although substantial change will have occurred
by then, some currently existing infrastructure
will still be in place and much of the
technology to be deployed over this period is
already under development. Scenarios
extending beyond this date are speculative, but
they are included because they are necessary to
evaluate the full implications of more
immediate decisions and because greenhouse
gases affect warming for many decades.
Projections to 2100 are based on the patterns
and relationships established between 1985
and 2025. The six scenarios analyzed in this
study were developed using the Atmospheric
Stabilization Framework. This analytical
framework was constructed for the purpose of
evaluating the impact of all anthropogenic
activities on the level of greenhouse gas
emissions, and consequently, on the rate and
magnitude of global climate change. For a
description of this Framework, the reader is
referred to Chapter VI and Appendix A.
It should be understood that the
discussions of climate change in Chapter 3 and
the discussions of the climate changes
associated with the various scenarios are
subject to great scientific uncertainties. The
general circulation models, which are the basis
for simulating climate changes, while among
the most sophisticated tools available, are
relatively simple compared to the feedback
mechanisms and processes that operate in the
real atmosphere/oceans system. The model
physics grossly oversimplify the real world.
The models do not yet adequately describe the
present climate and, thus, projections must be
viewed with extreme caution.
Scenarios with Unimpeded
Emissions Growth
In "A Slowly Changing World" (SCW)
we consider the possibility that the recent
experience of modest growth will continue
indefinitely, with no concerted policy response
to the risk of climate change. Per capita
income in developing regions that have very
high population growth is stagnant for several
decades, and shows modest increases
elsewhere. Economic growth rates per capita
increase slightly over time in all developing
regions as population growth rates gradually
decline. The population engaged in traditional
agriculture continues to increase, as does
speculative land clearing and demand for
fuelwood. These factors lead to accelerated
deforestation until tropical forests are virtually
eliminated toward the middle of the next
century. Because of slack demand, real energy
prices increase slowly. Productivity in industry
and agriculture improves at only a moderate
rate. Correspondingly, the energy efficiency of
buildings, vehicles, and consumer products
improves at a slow rate.
In "A Rapidly Changing World" (RCW)
rapid economic growth and technological
change occur with little attention given to the
global environment. Per capita income rises
rapidly in most regions and consumers demand
more energy services, which puts upward
pressure on energy prices. The number of cars
increases rapidly in developing countries, and
air travel increases rapidly in industrialized
countries. Energy efficiency is not much of a
consideration in consumer choices, as income
increases faster than real energy prices, but
efficiency increases do occur as a result of
technological improvements. Correspondingly,
we assume that there is a high rate of
innovation in industry and that capital
equipment turns over rapidly, thereby
accelerating reductions in energy required per
unit of industrial output. An increasing share
of energy is consumed in the form of
electricity, which is produced mostly from coal.
The fraction of global economic output
produced in the developing countries increases
dramatically as services become more
important in industrialized countries and as
industries such as steel, aluminum, and auto-
making grow in developing countries.
Population growth rates decline more rapidly
than in the Slowly Changing World scenario as
educational and income levels rise.
Deforestation continues at about current rates,
spurred by land speculation and commercial
logging, despite reduced rates of population
growth. Note that the SCW and RCW
scenarios are not bounding cases with respect
12
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Executive Summary
TABLE 2
Overview of Major Scenario Assumptions
Slowly Changing World
Slow GNP Growth
Continued Rapid Population Growth
Minimal Energy Price Increases
Slow Technological Change
Carbon-Intensive Fuel Mix
Increasing Deforestation
Montreal Protocol/Low Participation
Rapidly Changing World
Rapid GNP Growth
Moderated Population Growth
Modest Energy Price Increases
Rapid Technological Improvements
Very Carbon-Intensive Fuel Mix
Moderate Deforestation
Montreal Protocol/High Participation
Slowly Changing World
with Stabilizing Policies
Slow GNP Growth
Continued Rapid Population Growth
Minimal Energy Price Increases/Taxes
Rapid Efficiency Improvements
Moderate Solar/Biomass Penetration
Rapid Reforestation
CFC Phaseout
Rapidly Changing World
with Stabilizing Policies
Rapid GNP Growth
Moderated Population Growth.
Modest Energy Price Increases/Taxes
Very Rapid Efficiency Improvements
Rapid Solar/Biomass Penetration
Rapid Reforestation
CFC Phaseout
Rapidly Changing World
with Accelerated Emissions
High CFC Emissions
Cheap Coal
Cheap Synfuets
High Oil and Gas Prices
Slow Efficiency Improvements
High Deforestation
High-Cost Solar
High-Cost Nuclear
Rapidly Changing World
with Rapid Emissions Reductions
Carbon Fee
High MPG Cars
High Efficiency Buildings
High Efficiency Powerplants
High Biomass Penetration
Rapid Reforestation
13
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Policy Options for Stabilizing Global Climate
to emissions, rather the assumptions are
intended to be logically related, and therefore,
have partially offsetting implications.
Without stabilizing policies, rapid
greenhouse gas buildup and global warming
are likely. The two worlds described above
lead to significant increases in emissions of
carbon dioxide and other trace gases (see
Table 3) and in atmospheric concentrations of
the greenhouse gases (see Figure 4). CO2
concentrations reach twice their pre-industrial
levels in about 2080 in the SCW scenario. In
the RCW this level is reached by 2055, and
concentrations more than three times pre-
industrial values are reached by 2100. When
all the trace gases are considered, an increase
in the greenhouse effect equivalent to that
which would occur from a doubling of CO2
concentrations is reached by 2040 in the SCW
and by 2030 in the RCW. By 2100 the total
radiative forcing is equivalent to a tripling of
CO2 in the SCW and a factor of 5 increase in
the RCW. These results are in good
agreement with those of recent studies that
have made less formal estimates based
primarily on current trends in concentrations
and/or emissions. A notable exception are the
results for CFCs. The June 1990 London
Amendments will result in even lower concen-
trations of CFCs. However, because the
London Amendments were adopted after this
analysis, they are not included in the scenarios.
Even a Slowly Changing World would
produce a 2-3°C temperature increase
during the next century. In the SCW
scenario, realized global wanning would
increase by 1.0-1.5°C between 2000 and 2050
and by 2-3°C from 2000 to 2100 (temperature
ranges are based on a climate sensitivity of 2-
4°C unless otherwise noted; see Box 2 and
Figure 5). The maximum realized rate of
change associated with this scenario is 0.2-
0.3°C per decade, which occurs sometime in
the middle of the next century. The total
equilibrium warming commitment is
substantially higher, reaching 3->6°C by 2100
relative to pre-industrial levels (see Table 4).1
The "equilibrium wanning commitment"
is the warming that would eventually result
from a given atmospheric composition
assuming that it were to remain fixed at that
level. Because the oceans adjust thermally
over many years, it takes years or decades to
reach the equilibrium warming. "Realized
warming" is that portion of the equilibrium
warming that has been reached at any point in
time (see Box 2).
Higher rates of economic growth are
certainly the goal of most governments and
could lead to higher rates of climate change as
illustrated by the RCW scenario. The rate of
change during the next century would be more
than 50% greater than in the SCW: in the
RCW, realized global warming increases by
1.3-2.0°C between 2000 and 2050, and by 3-5°C
between 2000 and 2100. The total equilibrium
wanning commitment reaches 5->6°C by 2100.
In this case the maximum realized rate of
change is 0.4-0.6°C per decade, which occurs
sometime between 2070 and 2100.
The Impact of Policy Choices
Government policies, if applied
globally, could significantly increase or
decrease future warming. The wanning
suggested by the Slowly Changing and Rapidly
Changing World cases is not inevitable; it is
the result of the public and private choices
implicit in these scenarios. While some future
warming probably is locked in, the range of
possible future commitments to warming is
enormous.
Accelerated Emissions Scenario
Decisions that will be made in the near
future may lead to increased emissions if there
is no clear policy goal to reduce them. This
potential is illustrated by a series of tests that
were conducted to examine the effect of
accelerated emissions on equilibrium warming
commitment. Starting with the RCW scenario,
eight key parameters were varied as proxies for
recently-proposed policies that have the
potential to significantly increase greenhouse
gas emissions (e.g., accelerated development of
synfuels) or the possible consequences of
government inaction or failure (e.g., high use
of CFCs and deforestation).
14
-------
Executive Summary
TABLE 3
Trace Gas Emissions
CO, (Pg C)'
sew
RCW
RCWA
SCWP
RCWP
RCWR
N20 (Tg N)b
sew
RCW
RCWA
SCWP
RCWP
RCWR
CH4 (Tg CH4)
sew
RCW
RCWA
SCWP
RCWP
RCWR
NO,(TgN)
sew
RCW
RCWA
SCWP
RCWP
RCWR
CO (Tg C)
sew
RCW
RCWA
SCWP
RCWP
RCWR
CFC-12 (Gg)°- d
sew
RCW
RCWA
SCWP
RCWP
RCWR
HCFC-22 (Gg)d
sew
RCW
RCWA
SCWP
RCWP
RCWR
1985
6.0
6.0
6.0
6.0
6.0
6.0
12.5
12.5
12.5
1Z5
12.5
12.5
510
510
510
510
510
510
54
54
54
54
54
54
500
500
500
500
500
500
365
365
365
365
365
365
74
74
74
74
74
74
2025
9.6
12.4
21.9
. 5.2
5.4
2.1
16.5
16.1
18.5
13.1
13.3
13.1
690
730
910
540
560
520
71
79
105
48
56
53
830
720
980
290
290
270
395
450
860
50
85
85
405
830
830
405
830
830
2100
10.7
26.1
54.8
2.6
5.3
0.8
15.6
18.1
22.0
12.8
12.6
12.5
830
1,130
1,580
480
525
460
69
122
187
45
49
48
620
1,190
1,120
250
230
240
425
520
1,485
70
90
90
880
3,125
3,125
880
3,125
3,125
* Pg C = Petagrams of carbon; 1 Petagram = 10 grams.
* Tg N = Teragrams of nitrogen; 1 Tcragram = 10" grams.
c Gg = gigagram; 1 gigagram = 10* grams.
d These scenarios were produced prior to the negotiations for the London Amendments to the Montreal Protocol. The CFC
phaseout policy assumed in these policy scenarios is similar overall to, but somewhat more stringent than, the London
Amendments.
15
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Policy Options for Stabilizing Global Climate
1800
1600
1400
1200
1000
aoo
600
400 -
200 -
0
eoo
460
400
360
300
260
FIGURE 4
ATMOSPHERIC CONCENTRATIONS
(3.0 Degree Celsius Climate Sensitivity)
CARBON DIOXIDE
METHANE
/
.-
RCWA
6000
6000
MOW |4000
tCW 3000
RCWP
6CWP
MCWM 2000
1000
RCWA
new
sew
NITROUS OXIDE
CHLOROFLUOROCARBONS
10000
RCWff
SCWP
RCWR
RCWA
RCWA
RCW
1006 XOOO 2026 206«
YMT
1076 2106
1666 2060
210*
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Executive Summary
FIGURE 5
REALIZED WARMING
NO RESPONSE SCENARIOS
(Based on 2.0 - 4.0 Degree Sensitivity)
1985 2000
2025 2050
Year
2075 2100
Figure 5. Shaded areas represent the range based on an equilibrium climate sensitivity of 2-4°C to
a doubling of CO2.
17
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Policy Options for Stabilizing Global Climate
TABLE 4
Scenario Results For Realized And Equilibrium Wanning
Realized Warming - 2°C Sensitivity
sew
RCW
RCWA
SCWP
RCWP
RCWR
Realized Warming - 4°C Sensitivity
sew
RCW
RCWA
SCWP
RCWP
RCWR
Equilibrium Warming Commitment
sew
RCW
RCWA
SCWP
RCWP
RCWR
Equilibrium Warming Commitment
sew
RCW
RCWA
SCWP
RCWP
RCWR
1985
0.5
0.5
0.5
0.5
0.5
0.5
1985
0.7
0.7
0.7
0.7
0.7
0.7
- 2°C Sensitivity 1985
0.7
0.7
0.7
0.7
0.7
0.7
- 4°C Sensitivity 1985
1.5
1.5
1.5
1.5
1.5
1.5
2000
0.7
0.7
0.7
0.7
0.7
0.7
2000
1.0
1.0
1.1
1.0
1.0
1.0
2000
1.1
1.1
1.1
1.0
1.0
1.0
2000
2.2
2.2
2.3
2.0
2.0
2.0
2025
1.2
1.3
1.5
0.9
1.0
0.9
2025
1.8
1.9
2.1
1.4
1.5
1.4
2025
1.7
1.9
2.4
1.3
1.3
1.2
2025
3.5
3.8
4.7
2.5
2.6
2.3
2050
1.7
2.0
2.8
1.1
1.2
0.9
2050
2.6
3.0
4.2
1.7
1.9
1.5
2050
2.3
2.9
4.3
1.4
1.5
1.1
2050
4.7
5.8
>6.0*
2.7
3.1
2.1
2075
2.2
2.9
4.5
1.2
1.4
0.9
2075
3.4
4.4
>6.0*
1.9
2.2
1.5
2075
2.8
4.0
>6.0*
1.4
1.7
1.0
2075
5.7
>6.0*
>6.0*
2.8
3.4
1.9
2100
2.6
3.8
>6.0*
1.2
1.5
0.8
2100
4.2
6.0
>6.0*
2.1
2.5
1.4
2100
3.3
5.1
>6.0*
1.4
1.8
0.9
2100
>6.0*
>6.0*
>6.0*
2.8
3.7
1.7
* Estimates of equilibrium warming commitments greater than 6°C represent extrapolations beyond
the range tested in most climate models, and this wanning may not be fully realized because the
strength of some positive feedback mechanisms may decline as the Earth warms. These estimates are
represented by >6°C.
18
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Executive Summary
Box 2. Equilibrium and Realized Warming
Equilibrium Warming Commitment
The equilibrium warming commitment for any given year is the temperature increase that
would Occur in equilibrium if the atmospheric composition was fixed in that year. This
temperature may not be realized for several decades, and may not be realized at all if
greenhouse gas concentrations fall.
Realized Warming
Because the oceans have a large heat capacity the temperature change realized in the
atmosphere lags considerably behind the equilibrium level (the difference between the
equilibrium warming and the realized wanning in any given year is called the unrealized
warming). Realized wanning has been estimated with a simple model of ocean heat uptake.
Climate Sensitivity
Because the response of the climate system to changes in greenhouse gas concentrations is
quite uncertain due to the role of clouds and other processes, we also consider a range of
"climate sensitivities.* Climate sensitivity is defined as the equilibrium warming commitment
due to a doubling of the concentration of carbon dioxide from pre-industrial levels. Given a
particular emissions scenario and climate sensitivity, the realized wanning is much more
uncertain than the equilibrium warming commitment because the effective heat storage capacity
of the oceans is not known. On the other hand, because the amount of unrealized wanning
increases with increasing climate sensitivity, fora given scenario, realized warming depends less
on climate sensitivity than does equilibrium warming commitment.
Figure 6 illustrates the results of these
tests as compared with the RCW scenario.
The results are illustrated in terms of the
incremental effect of each outcome on the
equilibrium warming commitment in 2050 and
2100. As Figure 6 shows, the measures that
amplify the warming to the greatest extent are
those that reduce the rate of efficiency
improvement (historically, energy efficiency
has improved about l-2%#ear), reduce the
cost of synfuels, and increase the assumed rate
of growth in CFC production and use.
Policies leading to accelerated deforestation
would have a large impact in the near term,
but a relatively small impact in 2100.
The impact of all of these policies in
combination is quite dramatic. In this case,
emissions of CO2 would be nearly five times
pre-industrial levels. The rate of warming
during the next century would be over 60%
higher than in the RCW scenario.
Scenarios with Stabilizing Policies
Three scenarios were constructed to
explore the impact of policy choices aimed at
reducing the risk of global warming. The
Slowly Changing World with Stabilizing
Policies, the Rapidly Changing World with
Stabilizing Policies, and the Rapidly Changing
World with Rapid Reductions start with the
same economic and demographic assumptions
used in the SCW and RCW scenarios,
respectively, but assume that government
leadership is provided to ensure that a wide
range of measures to reduce greenhouse gas
emissions are implemented beginning in the
1990s.
19
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Policy Options for Stabilizing Global Climate
FIGURE 6
ACCELERATED EMISSIONS CASES:
PERCENT INCREASE IN EQUILIBRIUM WARMING COMMITMENT
1. High CFC Emissions"
2. Cheap Coal
3. Cheap Synfuels
4. High OH & Gas Prices
5. Slow Efficiency
Improvements*
6. High Deforestation'
7. High-Cost Solar
8. High-Cost Nuclear
Accelerated Emissions
(Combination of 1-8?
Percent Relative to RCW
-5 0 10 20 30 40 50 60 70
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Executive Summary
FIGURE 6 - NOTES
Impact Of Accelerated Emissions Policies On Global Warming
* Assumes a low level of participation in and compliance with the Montreal Protocol, excluding the London
Amendments, which were adopted after these scenarios were completed. The assumptions used in this case are
similar to those used in the "Low Case" analysis described in the U.S. EPA's Regulatory Impact Assessment report,
i.e., about 75% participation among developed countries and 40% among developing countries. In the RCW case
the U.S. was assumed to participate 100%, other developed countries 94%, and developing countries 65%.
b Assumes that advances in the technology of coal extraction and transport rapidly reduce the market price of coal
at the burner tip. In the RCW scenario, the economic efficiency of coal supply is assumed to improve at a rate of
approximately 0.5% per year. In this case, it is assumed to improve at a rate of 1% per year.
c Assumes that the price of synthetic oil and gas could be reduced by 50% and commercialization rapidly accelerated
relative to the RCW case.
d Assumes that OPEC (or some other political entity) could control production levels and thus raise the border
prices of oil and gas. To simulate this effect, oil and gas resources were shifted to higher points on the regional
supply curves. In addition, extraction costs for oil in each resource grade were increased relative to the assumptions
in the RCW case. In 2025 these assumptions increased oil prices about Si/barrel and gas prices about
S0.25/thousand cubic feet.
" Assumes that technical gains in the engineering efficiency of energy use occur only half as rapidly as assumed in
the RCW case. In the RCW case it is assumed that efficiency improves at rates of approximately 1-2% per year
(approximately equal to historical rates). In the Slow Improvement case the assumed rates were reduced to only
0.5-1.0% per year. The lower rate of improvement is similar to the assumptions in recent projections for the U.S.
DOE's National Energy Policy Plan.
f Assumes annual deforestation increases at a rate equal to the rate of growth in population. In the RCW case the
rate of deforestation increases at a slower rate, reaching 15 million hectares/year in 2097 compared to 34 million
hectares/year by 2047 in the RCWA case.
8 Assumes that the cost of solar energy precludes the possibility of its making any significant contribution to global
energy supply. In the RCW case costs approached 8.5 cents/kwh after 2050.
b Assumes that the cost of electricity from fission electric systems becomes so high that their contribution to global
energy supply is permanently limited. In this case, an environmental tax of about 6 cents/kwh (1988S) on the price
of electricity supplied by nuclear powerplants was phased in by 2050. In the RCW case nuclear costs were assumed
to be 6.1 cents/kwh in 1985.
' All of the above assumptions were combined in one scenario. The result is not equal to the sum of the wanning
in the RCW and the eight individual cases because of interactions among the assumptions.
21
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Policy Options for Stabilizing Global Climate
No single activity is the dominant
source of greenhouse gases; therefore, no
single measure can stabilize global climate.
Many individual components, each having
a modest impact on greenhouse gas
emissions, can have a dramatic impact on
the rate of climate change when combined.
The Stabilizing Policy scenarios therefore
assume that many policy initiatives are
undertaken simultaneously. These scenarios
assume that policies to promote energy
efficiency in all sectors succeed in substantially
reducing energy demand relative to the No
Response scenarios (which already assume
substantial efficiency improvements).
Research and development investments in
non-fossil energy supply options such as
photovoltaics (solar cells), biomass-derived
fuels and electricity (fuels made from plant
material), and advanced nuclear reactors are
assumed to make these options available and
begin to become competitive by 2000. As a
result, non-fossil energy sources meet a
substantial fraction of total demand in later
periods. There is considerable uncertainty as
to whether these sources could actually be
available on a competitive basis by the year
2000. In addition, whether these technologies
would be economically attractive in the
quantities projected in future scenario years is
quite uncertain. The existing protocol to
reduce CFC and halon emissions is assumed to
be strengthened, leading to a phaseout of fully-
halogenated compounds and a freeze on
methyl chloroform. (The London Amendments
to the Montreal Protocol, adopted after this
analysis was completed, call for the complete
phaseout of CFCs, halons, carbon
tetrachloride, methyl chloroform, and
encourage limits on HCFCs.) A global effort
to reverse deforestation transforms the
biosphere from a source to a sink for carbon
by 2000, and technological innovation and
controls reduce agricultural, industrial, and
transportation emissions. The impact of
these measures on wanning commitment in
2050 and 2100 is illustrated in Figures 7 and 8.
The results of this analysis suggest that
accelerated energy efficiency improvements,
reforestation, modernization of biomass use,
and carbon emissions fees could have the
largest near-term impact on the rate of climate
change. In the long run, advances in solar
technology and biomass plantations also play
an essential role. These conclusions are based
upon the assumptions made in these scenarios
about these technologies and about competing
technologies, such as nuclear fission. How
sensitive they may be to variations in the
assumptions, particularly to differences
reflecting economic differences between the
industrialized countries and the developing
countries, is not fully understood. While the
same general emissions reduction strategies
are assumed in both the SCWP and RCWP
cases, the degree and rate of improvement are
greater in the RCWP scenario because
technological innovation and capital stock
replacement occur at a faster pace.
The policies considered in these
scenarios do not require fundamental changes
in lifestyles. For example, energy use in
buildings is greatly reduced in the Stabilizing
Policy scenarios relative to the No Response
scenarios, but the floor space available per
person and the amenity levels provided are
assumed to be the same. Similarly, while
automobile fuel efficiency is assumed to be
much higher, restrictions on automobile
ownership are not considered. The potential
impact of policies on personal decisions that
directly change lifestyles has not been
examined.
It should be kept in mind that these
Stabilizing Policy scenarios incorporate
assessments of the technical feasibility of the
measures included and general judgments
about their likely economic character.
Analyses of economic feasibility, market
penetration, costs, benefits, and other
socioeconomic implications have not been
systematically completed. Knowledge is
particularly lacking about these socioeconomic
aspects under developing country conditions
where scarcity of capital and of trained
technical people could complicate efforts to
implement these measures.
These policy assumptions result in a
substantial reduction in the rate of greenhouse
gas buildup, but not an immediate stabilization
of the atmosphere (see Figure 9). In the
RCWP scenario global CO2 emissions decline
about 10% by 2025 and remain roughly
constant thereafter. This result implies
substantial reductions in emissions from
22
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Executive Summary
FIGURE 7
STABILIZING POLICY STRATEGIES:
DECREASE IN EQUILIBRIUM WARMING COMMITMENT
1. Improved Transportation
Efficiency*
2. Other Efficiency Gains"
3. Carbon Fee
4. Cheaper Nuclear
Power d
5. Solar Technologies*
6. Commercialized Biomass'
7. Natural Gas Incentives9
8. Emission Controls
9. CFC Phaseout*
10. Reforestation'
11. Agriculture, Landfills,
and Cementk
RCWP (Simultaneous i
Implementation of 1-11)
Percent Reduction Relative to RCW
64%
10 15
Percent
25
Figure 7. The impact of individual measures on the equilibrium warming commitment in the RCW
scenario. The simultaneous implementation of all the measures represents the RCWP scenario.
23
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Policy Options for Stabilizing Global Climate
FIGURE 7 -- NOTES
Impact Of Stabilizing Policies On Global Warming
a The average efficiency of cars and light trucks in the U.S. reaches 30 mpg (7.8 liters/100 km) by 2000; new cars achieve 40
mpg (5.9 liters/100 km). Global fleet-average automobile efficiency reaches 43 mpg by 2025 (5.5 liters/100 km). In the RCW
case global vehicle efficiencies for cars and light trucks achieve 30 mpg by 2025.
b The rates of energy efficiency improvements in the residential, commercial, and industrial sectors are increased about 0.3-0.8
percentage points annually from 1985 to 2025 compared to the RCW and about 0.2-0.3 percentage points annually from 2025-
2100. In the RCW case energy efficiency improvements averaged about 1-2% annually from 1985-2025, and less than 1% after
2025.
c Emissions fees are placed on fossil fuels in proportion to carbon content. Fees were placed only on production; maximum
production fees (1988$) are $1.00/GJ for coal (about $25Aon), S0.80/GJ for oil (about SS/barrel), and S0.54/GJ for natural gas
(about SO.SSAhousand cubic feet). These fees increase linearly from zero, with the maximum production fee charged by 2025.
In the RCW case no emission fees were assumed.
d Assumes that technological improvements in nuclear powerplam design reduce costs by about 0.6 cents/kwh (1988$) by 2050.
In the RCW case we assumed that nuclear costs in 1985 were 6.1 cents/kwh (1988$).
' Assumes that low-cost solar technology is available by 2025 at costs as low as 6.0 cents/kwh. In the RCW case these costs
approached 8.5 cents/kwh, but these levels were not achieved until after 2050.
f Assumes the cost of producing and converting biomass to modern fuels reaches S4.35/GJ (1988$) for gas (about $4.70Ahousand
cubic feet) and S6.00/GJ (1988$) for liquids (about S36/barrel) by 2025, with biomass penetrating more quickly than in the RCW
case due to more land committed to production. The maximum amount of liquid or gaseous fuel available from biomass (i.e.,
after conversion losses) is 205 EJ. In the RCW case these prices were not attained until 2035, and biomass energy penetrates
slowly because research and development is slow and because land is committed slowly to biomass energy production.
8 Assumes that economic incentives for gas use for electricity generation increase the gas share by 5% in 2000 (thereby reducing
prices about 1.6%) and 10% in 2025 (thereby reducing prices about 3.1%). Gas consumption for electricity generation was
about 21 EJ in the RCW case.
b Assumes more stringent NOX and CO controls on mobile and stationary sources, including all gasoline vehicles using three-way
catalysts, in OECD countries by 2000, and in the rest of the world by 2025 (new light-duty vehicles in the rest of the world use
oxidation catalysts from 2000 to 2025). In the RCW case only the U.S. adopts three-way catalysts (by 1985); the OECD
countries adopt oxidation catalysts by 2000, and the rest of the world does not add any controls. From 2000 to 2025
conventional coal boilers used for electricity generation are retrofit with low NO, burners, with 85% retrofit in the developed
countries and 40% in developing countries; starting in 2000 all new combustors used for electricity generation and all new
industrial boilers require selective catalytic reduction in the developed countries and low NO, burners in the developing
countries, and after 2025 all new combustors of these types require selective catalytic reduction. Other new industrial non-boiler
combustors such as kilns and dryers require low NO, burners after 2000. In the RCW case no additional controls are assumed.
1 A 100% phaseout of CFCs by 2003 and a freeze on methyl chloroform is imposed. There is 100% participation by
industrialized countries and 94% participation by developing countries. In the RCW scenario we assumed compliance with the
Montreal Protocol, which called for a 50% reduction in the use of the major CFCs. Note the London Amendments to the
Montreal Protocol, calling for a phaseout of CFCs, batons, carbon tetrachtoride, methyl chloroform, and encouraging limits on
HCFCs, are not reflected in the scenario; these Amendments were negotiated after this analysis was completed.
i The terrestrial biosphere becomes a net sink for carbon by 2000 through a rapid reduction in deforestation and a linear
increase in the area of reforested land and biomass plantations. Net CO2 uptake by 2025 is 0.7 Pg C. In the RCW case, the
rate of deforestation continues to increase very gradually, reaching 15 Mha/yr in 2097.
k Assumes that research and improved agricultural practices result in an annual 0.5% decline in the emissions from rice
production, enteric fermentation, and fertilizer use. CH4 emissions from landfills are assumed to decline at an annual rate of
2% in developed countries because of policies aimed at reducing solid waste and increasing landfill gas recovery, while emissions
in developing countries continue to grow until 2025 and then remain Oat due to incorporation of the same policies.
Technological improvements reduce demand for cement by 25%. In the RCW case no emission rate changes were assumed
for agricultural practices. CH4 emissions from landfills were assumed to remain constant in developed countries and increase
as the population grew in developing countries.
1 Impact on global warming when all the above measures are implemented simultaneously. The sum of each individual reduction
in warming is not precisely equal to the difference between the RCW and RCWP cases because not all the strategies are strictly
additive.
24
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Executive Summary
FIGURE 8
RAPID REDUCTION STRATEGIES:
ADDITIONAL DECREASE IN EQUILIBRIUM WARMING COMMITMENT
1. Carbon Fee
2. High MPG Cars
3. High Efficiency
Buildings'
4. High Efficiency
Powerplants"
5. High Biomass
6. Rapid Reforestation
Rapid Reduction *
(Implementation
of 1-6)
Additional Percent Relative to RCW
Figure 8. The impact of additional measures applied to the RCWP scenario expressed as percent
change relative to the equilibrium wanning commitment in the RCW scenario. The simultaneous
implementation of all the measures in combination with the measures in the RCWP scenarios
represents the Rapid Reduction scenario.
25
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Policy Options for Stabilizing Global Climate
FIGURE 8 -- NOTES
Impact Of Rapid Reduction Policies On Global Warming
a High carbon emissions fees are imposed on the production of fossil fuels in proportion to the CO2 emissions
potential. In this case, fees of about S4.00/GJ were imposed on coal (SlOO/ton), S3.20/GJ on oil (S19/barrel), and
S2.15/GJ on natural gas (S2.00/mcf). These fee levels are specified in 1988$ and are phased in over the period
between 1985 and 2025. No fees were assumed in the RCW case.
b Assumes that the average efficiency of new cars in the U.S. reaches 50 mpg (4.7 liters/100 km) in 2000 and that
global fleet-average auto efficiencies reach 65 mpg (3.6 liters/100 km) in 2025 and 100 mpg (2.4 liters/100 km) in
2050. Comparable assumptions for the RCWP case were 40,50, and 75 mpg for 2000,2025, and 2050, respectively.
c Assumes that the rate of technical efficiency improvement in the residential and commercial sectors improves
substantially beyond that assumed in the RCWP case. In this case, the rate of efficiency improvement in the
residential and commercial sectors is increased so that a net gain in efficiency of 50% relative to the RCWP case
is achieved in all regions. In the RCWP case rates of efficiency improvement averaged 1.5-3.0% per year from
1985-2025.
d Assumes that by 2050 average powerplant conversion efficiency improves by 50% relative to 1985. In this case,
the design efficiencies of all types of generating plants improve significantly. For example, by 2025 new oil-fired
generating stations achieve an average conversion efficiency roughly equivalent to 5% greater than that achieved
by combined-cycle units today. In the RCW case new oil-fired units achieve an average conversion efficiency equal
to combined-cycle units today.
e The availability of commercial biomass was doubled relative to the assumptions in the RCWP case. In this case
the rate of increase in biomass productivity is assumed to be at the high end of the range suggested by the U.S.
DOE Biofuels Program. Conversion costs were assumed to fall by one-third relative to the assumptions in the
RCWP case.
f A rapid rate of global reforestation is assumed. In this case deforestation is halted by 2000 and the biota become
a net sink for CO2 at a rate of about 1 Pg C per year by 2025, about twice the level of carbon storage assumed in
the RCWP case.
g Impact on warming when all of the above measures are implemented simultaneously. The impact is much less
than the sum of the individual components because many of the measures are not additive.
26
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Executive Summary
FIGURE 9
REALIZED WARMING:
NO RESPONSE AND STABILIZING POLICY SCENARIOS
(Based on 2.0 - 4.0 Degree Sensitivity)
Slowly Changing World
Rapidly Changing World
1985 2000 2026 2060 2076 2100
1t«6 2000 2026 2060 2076 2100
Figure 9. Shaded areas represent the range based on an equilibrium climate sensitivity to doubling
CO2 of 2-4°C.
27
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Policy Options for Stabilizing Global Climate
industrialized countries, however. U. S.
emissions, for example, fall 40% by 2025.
Carbon dioxide concentrations increase
gradually throughout the time frame of the
analysis despite roughly constant emissions (as
discussed above). Total radiative forcing is
close to being stabilized by 2100, but the level
is equivalent to almost a doubling of pre-
industrial CO2 concentrations in the RCWP
and to a 65% increase in the SCWP.
The rate of climate change in the
SCWP and RCWP scenarios is at least 60%
less than in the corresponding worlds
without policy responses, but the risk of
substantial climate change is still significant.
The rate of global temperature increase during
the next century in these scenarios is 0.5-1.5°C,
while the maximum rate of change is less than
0.2°C per decade between 2000 and 2025. This
represents much more gradual change than in
the No Response scenarios, but it does not
ensure that the rate of warming will remain
below 0.1°C per decade. Some experts have
suggested that this rate of change represents
the maximum to which many species of plants
and animals could adapt. Total equilibrium
warming commitment could exceed 3.5°C by
2100 in the RCWP case. Given the possibility
that the climate sensitivity could be higher and
that there could be large positive
biogeochemical feedbacks that are not
included in these calculations, there is a
possibility that these scenarios could lead to
extremely rapid climate change. It is also
possible that the policies assumed in these
scenarios could limit climate change to about
1°C if the true climate sensitivity of the Earth
is low.
Only the most aggressive policy case
reverses the greenhouse gas buildup early in
the 21st century. The economic feasibility,
costs, benefits, and other socioeconomic
implications of such policies have not been
determined at this time. The Rapid
Reduction scenario explores the impact of
policies that effect a rapid transition away
from fossil fuels. In the Rapid Reduction
scenario net global CO2 emissions decline
nearly 15% by 2000 and 65% by 2025. U.S.
emissions decline 20% by 2000 and 50% by
2025. The atmospheric concentration of CO2
peaks below 400 ppm around 2025, and total
greenhouse forcing peaks at an equivalent CO2
concentration of less than 450 ppm. After this
point, equivalent CO2 concentrations decline
until by 2100 they are about equal to current
levels of atmospheric greenhouse gas
concentrations (on a CO2-equivalent basis). It
is this level of concentration, and the policy
options necessary to achieve this level, that
Congress specifically requested U.S. EPA to
evaluate. Despite declining concentrations,
however, temperatures continue to rise to
about 2050, peaking at 0.9-1.5°C above pre-
industrial levels. In this case the maximum
rate of change is 0.09-0.16°C per decade
between 2000 and 2025, but the average rate
of change over the next century is much less
than O.rC per decade. The measures that
reduce the warming to the greatest extent in
the Rapid Reduction case relative to the
RCWP case are those that impose stiff carbon
fees on the production of fossil fuels, improve
the energy efficiency of buildings, and increase
the assumed level of renewable resource
availability. Options for phasing in carbon
fees so as to minimize impacts on the global
economy require additional analysis.
To reduce the amount of global
warming to the rates projected in the RCWP
and Rapid Reduction cases, Table 5 lists
several policies that might have to be adopted
by 2000 to begin reducing greenhouse gas
emissions. These examples are meant to
illustrate potential policy responses; a variety
of policy combinations might achieve the
reductions in global wanning estimated in each
case.
TECHNOLOGICAL OPTIONS
FOR REDUCING GREENHOUSE
GAS EMISSIONS
There is a wide variety of available, or
potentially available, options to reduce
greenhouse gas emissions that it is believed
would not unduly interfere with meeting
growing demands for goods and services. The
current status and potential of these options
are briefly reviewed below. In most cases, the
costs and benefits of these options for
responding to climate change cannot be fully
quantified at this time, both because of
scientific uncertainties about climate change
itself and because of many economic
28
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Executive Summary
TABLE 5
Examples Of Potential Policy Responses By The Year 2000
RCWP Case
• Research on energy efficiency and non-fossil-fuel technology is accelerated
• New automobiles in the U.S. average 40 mpg
• New automobiles in the OECD use three-way catalytic converters to reduce CO and NO^ the rest of world
uses an oxidation catalyst
• Average space-heating requirements of new single-family homes are 50% below 1980 new home average
• Net global deforestation stops
• CFCs are phased out; production of methyl chloroform is frozen
• Fossil fuels are subject to emission fees that are set according to carbon content -- J I0/ton on coal, S2/barrel
on oil, S0.20/thousand cubic feet on natural gas
• Accelerated research and development into solar photovoltaic technology allows solar power to compete with
oil and natural gas (U.S. DOE long-term policy goals)
• Available municipal solid waste and agricultural wastes are convened to useful energy
• Accelerated research on biomass energy plantations increases current productivity by 65% (to 25 dry
tons/hectare annually) •
RCWRCase
• Research on energy efficiency and non-fossil-fuel technology is accelerated
• New automobiles in the U.S. average 50 mpg
• Major retrofit initiatives reduce energy use in existing commercial buildings by 40%
• Average space-heating requirements of new single-family homes are 90% below 1980 new home average
• Global deforestation stops; major reforestation programs are undertaken
• CFCs are phased out; production of methyl chloroform is frozen
• Fossil fuels are subject to emission fees that are set according to carbon content - S38Aon on coal, S7/barrel
on oil, $0.75/thousand cubic feet on natural gas
• Commercialization incentives lead to significant market penetration for solar technologies
• 250 million hectares globally are committed to biomass energy plantations, i.e., 5% of forest and woodland
area
29
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Policy Options for Stabilizing Global Climate
uncertainties about the potential options
themselves.
Improve Energy Efficiency
The introduction of technologies and
practices that use less energy to accomplish
a given task would have the largest impact
on global warming in the near term. Both
industrialized and developing countries can
significantly improve energy efficiency.
Although per capita energy consumption is
very low in developing countries, there is a
large potential to increase efficiency because
energy use per unit of GNP is often extremely
high. Indeed, the imperative for energy
efficiency may be even stronger in developing
countries to the extent that expending scarce
capital on expanding energy supply systems can
be avoided. Many of the technical options
described below may be directly applicable in
developing as well as industrialized countries,
but alternative approaches suited to available
resources will also be needed. In many cases
improved management of existing facilities
could have large payoffs. We estimate that
accelerated improvements in energy efficiency
account for about 25% of the difference
between the RCWP and the RCW cases in
2050 (we note that this occurs even though
fairly rapid improvements are already assumed
in the RCW case).
Improved Transportation Efficiency
A number of known technologies have
the technical potential to increase automobile
fuel efficiency from current levels for new cars
(25-33 mpg or 9.4-7.1 liters/100 km) to
significantly higher levels. What could be
achieved in the foreseeable future without
downsizing vehicles and reducing safety and
other desirable characteristics is uncertain.
Given the currently available technical options
and their likely costs of implementation, a
fleet average new car economy level of 40 mpg
by the year 2000 could require size and
performance reductions. The RCWP scenario
assumes that new cars in the industrialized
countries achieve an average of 50 mpg (4.7
liters/100 km) in 2025 and 75 mpg (3.1
liters/100 km) in 2050 (somewhat lower rates
of efficiency improvement are assumed in the
SCWP scenario). In addition, major fuel
efficiency improvements in diesel trucks and
aircraft are possible. The Rapid Reduction
case assumes more aggressive measures to
improve efficiency.
Other Efficiency Gains
More efficient building shells, lighting,
heating and cooling equipment, and appliances
are currently commercially available. The
most efficient new homes currently being built
use only 30% as much heating energy per unit
of floor area as the average existing house in
the United States. Advanced prototypes and
design calculations indicate that it is
technically possible to build new homes that
use only 10% of current average energy
requirements. The economic feasibility, the
likely market penetration, and the costs of
implementing such technological options are
uncertain. About 20% of U.S. electricity is
consumed for lighting, mainly in residential
and commercial buildings. A combination of
currently available advanced technology and
careful design has been shown to cost-
effectively reduce energy requirements for
lighting by more than 75%. The RCWP
scenario assumes that the average reduction in
energy use per unit of residential and
commercial floor space by 2025 in the U.S. is
as much as 75% for fuel and 50% for
electricity. Smaller improvements are assumed
in other regions and in the SCWP scenario.
Advanced industrial processes currently
available can significantly reduce the energy
required to produce basic materials -
especially if these processes are used in
combination with recycling. For example,
estimates of the reductions in energy intensity
of U.S. steel production that are technically
feasible range from 20 to 50 percent. How
much of these savings would be economically
feasible and at what cost is unknown. Electric
motors are estimated to account for about
70% of US. industrial electricity use. Several
case studies show that improved motors and
motor controls now commercially available
could reduce energy consumption by electric
motors at least 15% relative to current
averages.
While the promise of technically feasible
efficiency gains is great, the uncertainties
about the rate and scale of implementation of
30
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Executive Summary
such measures are also great. Many of these
gains would depend, in the U.S. and other
developed countries, upon the rates at which
the existing capital stock is replaced by new,
more efficient capital equipment and facilities.
Such rates depend upon a host of economic
and other factors that are difficult to assess:
the rates at which potential users learn about
new technologies, the age and value of existing
equipment and facilities, the availability and
cost of credit, the degree that existing capital
capacity is utilized, and so forth. For these
reasons, market penetration rates of new
technologies, and how such rates might be
accelerated, are very uncertain.
Carbon Fee \
One way to provide a market signal that
CO 2 emissions have environmental
consequences is to apply a "carbon1' fee to the
price of fossil fuels that is proportional to the
carbon content of the fuel. Fees could be used
in conjunction with performance standards and
other strategies to encourage energy
conservation and investments in energy-
efficient technology. A carbon fee would also
affect the relative prices of fossil and non-
fossil energy sources and the relative prices
among the fossil fuels, reinforcing the policies
discussed in the following sections. The
revenues from such a fee could be used to
reduce other taxes, reduce the national debt,
and/or support other national goals. To be
least disruptive, revenues would need to be
offset by reductions in other taxes. Further
analysis is required to determine these impacts
on the economy. In particular, the full social
costs and benefits of substantial reductions in
an energy option, such as coal use, due to high
carbon fees or to command-and-control
regulations, have not been evaluated.
Given the scientific and economic
uncertainties about the changes in climate that
are likely to result from given changes in
greenhouse gas concentrations, and the net
costs to society of such climate changes,
appropriate levels for setting greenhouse gas
fees are unknown.
If greenhouse gas fees and other
controls on emissions are not established on a
comparable basis world-wide, the problem of
emissions-intensive activities migrating to
countries where fees were lower or controls
less stringent could occur, thereby reducing the
net effectiveness of the fees or controls.
Increase Use of Non-Fossil Energy
Sources
There is a critical need for research
on non-fossil energy technologies. The
development of attractive non-fossil energy
sources is critical to the success of any climate
stabilization strategy over the long term.
Under the assumptions of this report's
scenarios, increased penetration of solar and
advanced biomass technologies contribute little
to reduced warming in 2025, but they are
responsible for 24% of the difference between
the RCWP and the RCW case in 2050, and
over 25% of this difference in 2100. Figure 10
shows the relative contribution to primary
energy supply of each fossil and non-fossil fuel
under each of our scenarios. The exact mix of
non-fossil energy supply technologies assumed
in the policy scenarios is rather arbitrary, but
makes little difference to greenhouse gas
emissions. Some particularly promising non-
fossil technologies are described below.
Nuclear Power
Nuclear fission produces about 5% of
global primary energy supplies and its share
has been growing. High cost and concerns
about safety, nuclear proliferation, and
radioactive waste disposal, however, have
brought new orders for nuclear powerplants to
a halt in many countries. Advanced designs, in
particular the Modular High Temperature
Gas-cooled Reactor, have recently been
proposed in an attempt to overcome some of
these problems. The role of nuclear power
could be significantly expanded in the future if
these efforts are successful and public
confidence in this energy source is restored.
Nuclear power's contribution to primary
energy supply in the SCWP case increases to
less than 7% in 2050 and to 8% in 2100 and
in the RCWP case to 10% in 2050 and 18% in
2100. It is possible that the nuclear
contribution could be substantially greater, if
concerns about safety, nuclear proliferation,
and waste disposal could be adequately dealt
with and if costs could be reduced by moving
toward the manufacture of standardized
31
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Policy Options for Stabilizing Global Climate
1500
FIGURE 10
PRIMARY ENERGY SUPPLY BY TYPE
1600
!••• 2000 2026 20«0 2076 2100 1986 2000 2026 2060 2076 2100
Y»«r YMT
Not*: FuN «c«l» !• douM^ for MM RCWA ea»».
32
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Executive Summary
powerplants and away from the construction of
one-of-a-kind facilities.
Solar Technologies
There is a range of solar technologies
currently available or under development that
could increase the use of solar energy. Direct
use of solar thermal energy, either passively or
in active systems, is already commercial for
many water- and space-heating applications.
In some locations wind energy systems are also
currently commercial for some applications.
In recent years engineering advances have
resulted in significant cost reductions and
performance improvements. Solar
photovoltaic (PV) cells are currently
competitive for many remote power generation
needs, especially in developing countries.
Dramatic progress has been made recently in
reducing the costs of producing PV systems,
particularly with thin-film amorphous silicon
technology. If current research and
manufacturing development efforts reach their
objectives, PV could play a major role in
meeting energy needs in the next century. The
degree to which these objectives, particularly
cost reduction, could be achieved by specific
times and the size of the future contribution
are, of course, uncertain. In the SCWP
scenario solar sources of electricity are
equivalent to 6% of primary energy supply
from 2050 onward. A larger contribution is
envisioned in the RCWP scenario: 10% in
2050, increasing to over 13% in 2100.
Hydro and Geothermal Energy
Other renewable resources can also
increase their contribution to total energy
supplies. Hydroelectric power is already
contributing the equivalent of about 7% of
global primary energy production, and
geothermal power is making a small (less than
1%) but important contribution. There is
potential to expand the contribution of these
sources, although good hydro and geothermal
sites are limited and environmental and social
impacts of large-scale projects must be
considered carefully.' Significant questions
concerning the economics of remaining
available sites, and the likely environmental
constraints on these sites, have not been
analyzed in detail. Hydroelectric and
geothermal power expands to nearly 13% of
global primary energy production in the SCWP
scenario, but increases only to about 9% in the
RCWP case (this relatively smaller
contribution is due to the higher level of
energy production; i.e., the absolute amount is
higher, but the percentage is lower).
Commercialized Biomass
Biomass is currently being extensively
utilized, accounting for roughly 10% of global
energy consumption, primarily in traditional
applications (e.g., cooking), which are not
included in most official accounts of
commercial energy use. Current and emerging
technologies could vastly improve the
efficiency of biomass use. In the near term
there is substantial potential for obtaining
more useful energy from municipal and
agricultural wastes. More advanced
technologies for producing, collecting, and
converting biomass to gaseous and liquid fuels
and electricity could become economically
competitive within a decade. The prospects
for integrating biomass gasification with
advanced combustion turbines is particularly
promising. While the technical potential for
commercialized biomass is highly promising,
important questions remain about the scale
and degree of the economic potential. In
particular, the availability of productive land
that could be devoted to growing biomass fuels
needs further study. Furthermore,
environmental and societal impacts related to
large-scale biomass use, which would have to
be addressed, include competition with food
production, ecological impacts, and emissions
of volatile organic compounds. In the SCWP
scenario biomass energy supplies 32% of
primary energy needs in 2050 and 48% in
2100. Biomass supplies about 32% of primary
energy by 2050 and 32% by 2100 in the RCWP
scenario.
Reduce Emissions from Fossil
Fuels
Inherent to the burning of fossil fuels is
the generation of large amounts of CO2.
Although it is technically possible to scrub
CO2 out of central station powerplants, it is
estimated that this would probably at least
double the cost of power generation, and an
-------
Policy Options for Stabilizing Global Climate
environmentally acceptable method of disposal
has not been demonstrated. All fossil fuels
are not created equally, however. Burning
coal produces about twice as much CO2 per
unit of energy released as does natural gas; the
amount of CO2 produced by oil is about 80%
of the amount produced by coal.
Furthermore, oil and gas have the potential to
be used much more efficiently than coal in
power generation, substantially increasing their
CO2 advantage. Thus fuel switching among
fossil fuels can significantly reduce CO2
emissions. Similarly, non-CO2 emissions from
fossil-fuel burning can be controlled, resulting
in significant impacts on greenhouse gas
concentrations. Also, when new fossil-fuel
facilities need to be built, emissions can be
minimized by installing the most efficient
technologies, such as the use of Integrated
Gasification/Combined Cycle (IGCC) systems
for new coal-fired generation requirements.
The potential timing and market
penetration of more efficient fossil-fuel-fired
technologies are uncertain, particularly in the
developing countries, where most of the
growth in emissions is likely to take place.
The potential impact of these technologies is
significant, but their cost effectiveness is very
uncertain.
Greater Use of Natural Gas
Because of its inherent CO2 advantage
over other fossil fuels, increased use of natural
gas could significantly reduce total emissions.
Two important considerations should be kept
in mind, however. First, natural gas is a finite
resource. Increased use of natural gas during
the next few decades could provide an
essential bridge as non-fossil energy sources
are further developed, but unless a transition
toward reduced dependence on fossil fuels is
accomplished, reduced availability of natural
gas in later periods could offset the gains from
using gas in earlier periods. Second, natural
gas is primarily methane, which is itself a
powerful greenhouse gas. If a substantial
amount of methane reaches the atmosphere
through leaky transmission or distribution
pipes, the advantage of natural gas can be
significantly reduced or offset.
Emission Controls
Emissions of CO contribute to elevating
methane concentrations, and NOX emissions
contribute to tropospheric ozone formation,
both of which are important greenhouse gases.
Thus, more stringent and comprehensive
controls on CO and NOX, such as three-way
catalysts on automobiles and low-NOx burners
on boilers and kilns, would reduce greenhouse
gas concentrations as well.
Reduce Emissions from Non-
Energy Sources
CFC Phaseout
Halocarbons (which include CFCs and
halons) are potent stratospheric ozone
depleters as well as greenhouse gases.
Concern over their role as a threat to the
ozone layer led in September 1987 to "The
Montreal Protocol on Substances That
Deplete the Ozone Layer" (or the Montreal
Protocol). The Montreal Protocol came into
force on January 1,1989, and has been ratified
by 68 countries, representing just over 90% of
current world consumption of these chemicals
(as of February 1, 1991). The London
Amendments to the Protocol, which call for
the phaseout of CFCs, halons, carbon
tetrachloride, and methyl chloroform, and
encourages limits of HCFCs, were adopted in
June 1990. These amendments were adopted
after this analysis was completed.
Further reductions in CFCs are
needed to slow the buildup of atmospheric
concentrations. The major provisions of the
Montreal Protocol include a 50% reduction
from 1986 levels in the use of CFC-11, -12,
-113, -114, and -115 by 1998; a freeze on the
use of Halon 1211, 1301, and 2402 at 1986
levels starting in approximately 1992; and a
delay of up to 10 years in compliance with the
Protocol for developing countries with low
levels of use per capita. As a result of this
historic agreement, the very high growth rates
in CFC concentrations assumed in some
previous studies are unlikely to occur.
However, because of the long atmospheric
34
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Executive Summary
lifetimes of CFCs, the probability that not all
countries will participate in the agreement,
and the provision for increased use in
developing countries, CFC concentrations will
still rise significantly in the future unless the
Protocol is strengthened (see Figure 4). An
international meeting to discuss strengthening
of the Protocol was held in June 1990 in
London, England. The Amendments to the
Protocol adopted in London were similar to,
but not as stringent as, the phaseout assumed
in this analysis.
Promising chemical substitutes,
engineering controls, and process modifi-
cations that could eliminate most uses of
CFCs have now been identified. In the policy
scenarios we assume that the use of CFCs and
halons is phased out and that emissions of
methyl chloroform are frozen (no additional
growth in CFC substitutes is assumed as a
result of the phaseout beyond the levels
assumed under the Protocol). Even under
these assumptions total weighted halocarbon
concentrations increase significantly from 1985
levels, in part because the chemical substitutes
contribute significantly to greenhouse forcing,
although the final concentrations are about
one-third of the level in the corresponding No
Response scenarios. The greenhouse forcing
potential of CFC substitutes will have to be
carefully evaluated to improve estimates of
their potential role in climate change. In our
analysis, phasing out CFCs was responsible for
9% of the decrease in wanning in the RCWP
in 2050 relative to the RCW.
Reforestation
Deforestation and biomass burning are
significant sources of CO2, CO, CH4, NO,p and
N2O. The world's total forest and woodland
acreage has been reduced by about 15% since
1850, primarily to accommodate the expansion
of cultivated lands. It is generally estimated
that approximately 11 million hectares (Mha)
of tropical forests are currently lost each year,
while only 1.1 Mha are reforested per year.
Generally, temperate and boreal forests appear
to be in equilibrium. Estimates of net
emissions of CO2 to the atmosphere due to
changes in land use (deforestation,
reforestation, logging, and changes in
agricultural area) in 1980 range from
approximately 10-30% of annual
anthropogenic CO2 emissions to the
atmosphere.
Reversing deforestation offers one of
the most attractive policy responses to
potential climate change. Although a vast
area of land would have to be involved to
make a significant contribution to reducing net
CO2 emissions, preliminary estimates suggest
that the cost of absorbed or conserved carbon
could be low in comparison to other options,
at least initially. How rapidly reforestation
costs would increase as lands with increasingly
high productivity in other uses were
transferred to forest use is not well
understood. The areas of land that would be
feasible and economic to transfer to forest use
are also not well defined. Furthermore, a
reforestation strategy could offer a stream of
valuable ecological and economic benefits in
addition to reducing CO2 concentrations, such
as production of forest products, maintenance
of biodiversity, watershed protection, nonpoint
pollution reduction, and recreation. Devising
successful forestry programs presents unique
challenges to scientists and policymakers
because of the vast and heterogeneous
landscape, uncertain ownership, lack of data,
and the need for more research and field trials.
Investments that would be small by the
standards of the energy industry, however,
could make an enormous impact on forestry.
In the Stabilizing Policy scenarios it is
assumed that by 2000 the biosphere is
transformed from a source to a sink for
carbon. A combination of policies succeed in
stopping deforestation by 2025, while up to
one billion hectares of land is reforested by
2100 (some of this land is devoted to biomass
energy plantations as discussed above). This
assumed area of reforestation could exceed the
area of the United States. Whether or not
this much land could be made available on a
global basis for reforestation, given the needs
for uses for subsistence and commercial
agriculture, has not been determined.
Reforestation accounts for almost one-fifth of
the decrease in wanning by 2050 in the RCWP
versus the RCW scenarios.
Agriculture, Landfills, and Cement
Domestic animals, rice cultivation, and
use of nitrogenous fertilizers are significant
35
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Policy Options for Stabilizing Global Climate
sources of greenhouse gases. Methane is
produced as a by-product of digestive
processes in herbivores, particularly ruminants
(e.g., cattle, dairy cows, sheep, buffalo, and
goats). Globally, domestic animals
(predominantly cattle) are responsible for
about 15% of total methane emissions. The
gas is also produced by anaerobic decom-
position in flooded rice fields and escapes to
the atmosphere largely by transport through
the rice plants. The amount of CH4 released
to the atmosphere is a complex function of
rice species, number and duration of harvests,
temperature, irrigation practices, crop residue
management, and fertilizer use. Rice fields are
estimated to contribute approximately 10-30%
of the global emissions. Nitrous oxide is
released through microbial processes in soils,
both through denitrification and nitrification.
The use of nitrogenous fertilizer enhances
N2O emissions since some of the applied N is
converted to N2O and released to the
atmosphere. The amount of N2O released
varies a great deal depending on rainfall,
temperature, the type of fertilizer applied,
mode of application, and soil conditions. A
preliminary estimate suggests that this source
produces 1-20% of global N2O emissions.
Future research and technological
changes could reduce agricultural emissions,
In the policy scenarios we do not assume
changes in the demand for agricultural
commodities, but rather changes in production
systems that could reduce greenhouse gas
emissions per unit of product. Although the
impact of specific approaches cannot be
quantified at present, a number of techniques,
such as feed additives for cattle, changes in
water management in rice production, and
fertilizer coatings, have been identified for
reducing methane and nitrous oxide emissions
from agricultural sources. The extent to which
these options are implemented depends on
further research and demonstrations. For
simplicity we have assumed that methane
emissions per unit of rice, meat, and milk
production decrease by 0.5% per year
(emissions from animals not used in
commercial meat or milk production are
assumed to be constant). Emissions of nitrous
oxide per unit of nitrogen fertilizer applied are
also assumed to decrease by 0.5% per year for
each fertilizer type. In addition, we assume
that after 2000 there is a shift away from those
types of fertilizers with the highest emissions.
Under these assumptions agricultural
emissions are substantially lowered in the
policy scenarios relative to the No Response
scenarios, although absolute emissions do not
decline.
Landfills represent a potentially
controllable source of methane. Waste
disposal in landfills and open dumps generates
methane when decomposition of the organic
material becomes anaerobic; approximately
80% of urban solid wastes is currently
disposed in one of these ways. Most of the
decomposition in landfills and some of the
decomposition in open pits is anaerobic.
Annual methane emissions from landfills and
open pits represent about 10% of total
methane emissions.
Landfilling can be expected to increase
dramatically in developing countries as
population growth, urbanization, and
economic growth all imply increased disposal
of municipal solid waste. The result is a three
and fivefold increase in methane emissions
from landfills in the SCW and RCW scenarios,
respectively. The Stabilizing Policy scenarios
assume that gas recovery systems, recycling,
and waste reduction policies will be adopted,
resulting in roughly constant global emissions
from landfills.
Carbon dioxide is emitted in the
calcining phase of the cement-making process
when calcium carbonate (CaCO3) is converted
to lime (CaO). For every ton of cement
produced 0.14 tons of carbon are emitted as
CO2 from this reaction. World cement
production increased from 130 million tons in
1950 to about one billion tons currently.
Thus, current CO2 emissions from calcining
are 0.14 billion tons of carbon (0.14 Pg C), or
more than 2% of total CO2 emissions. In the
Stabilizing Policy scenarios, advanced materials
are assumed to reduce the demand for cement
relative to the No Response scenarios, but
emissions still grow significantly.
Reduced emissions from agriculture,
landfills, and cement manufacture account for
12% of the reduced warming in the RCWP in
2050 relative to the RCW scenario.
36
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Executive Summary
A WIDE RANGE OF POLICY
CHOICES FOR THE SHORT
AND LONG TERM
The prospect of global climate change
presents policymakers with a unique challenge.
The scale of the problem is unprecedented in
both space and time. Many choices are
available and the consequences of these
choices will be profound.
A wide range of policy choices is
available for reducing greenhouse gas
emissions. There is an important distinction
between short-term and long-term policy
options. In the short term, the most effective
means of reducing emissions is through
strategies that rely on pricing and regulation.
There is a wide range of potential policy
choices that may make sense despite the
scientific and economic uncertainties. In the
long term, policies to increase research and
development of new technologies, to enhance
markets through information programs and
other means, and other actions making it
possible to achieve world-wide economic
growth while limiting emissions growth will be
essential for long-term effects on the climate
change problem.
• The most direct means of allowing
markets to incorporate the risk of climate
change is to ensure that the prices of fossil
fuels and other sources of greenhouse gases
reflect their full social costs. It may be
necessary to impose emission fees on these
sources according to their relative contribution
to global wanning in order to accomplish this
goal. Unfortunately, the costs and benefits of
global wanning are not fully known, and,
therefore, the fees that would correspond to
charging full social costs can not now be
determined. Better information would be
needed as a basis for establishing levels of fees.
Fees would also raise revenues that could
finance other programs or offset other taxes.
The degree to which such fees are accepted
will vary among countries, but acceptability
would be enhanced if fees were equitably
structured. The impact of fees on the global
economy would depend on the size of the fees,
how they were phased in, and how the
revenues were used, among other factors. The
effectiveness of fees in reducing world-wide
greenhouse gas emissions would depend on the
degree to which they are applied consistently
throughout the world and therefore avoid
encouraging emissions-intensive activities to
relocate to low fee areas. These issues require
additional analysis.
• Regulatory programs would be a
necessary complement if pricing strategies
were not effective or had undesirable impacts.
In the U.S., greenhouse gas emissions are
influenced by existing federal regulatory
programs to control air pollution, increase
energy efficiency, and recycle solid waste.
Reducing greenhouse gas emissions could be
incorporated into the goals of these programs.
New programs could focus directly on reducing
greenhouse gas emissions through
requirements such as emissions offsets (e.g.,
tree planting), performance standards, or
marketable permits. Different kinds of
regulatory approaches would have different
degrees of efficiency and costs, differences in
treating greenhouse gases in a comprehensive
fashion, and differences in how they permit
those regulated to make cost-optimal
decisions. A full understanding of these
differences and of the inherent advantages of
using automatic market mechanisms to
encourage environmentally sound behavior is
needed, particularly with respect to regulatory
approaches in countries with limited
experience in market-oriented environmental
regulation. Regulatory approaches, like other
policies, would also have to deal with the need
to avoid encouraging emissions-intensive
activities to relocate to areas of less stringent
regulation.
• State and local government policies in
such areas as utility regulation, building codes,
waste management, transportation planning,
and urban forestry could make an important
contribution to reducing greenhouse gas
emissions.
• Voluntary private efforts to reduce
greenhouse gas emissions have already
provided significant precedents for wider
action and could play a larger role in the
future.
• Over the long term, other policies will
be needed to reduce emissions and can
complement pricing and regulatory strategies.
37
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Policy Options for Stabilizing Global Climate
Other policy options include redirecting
research and development priorities in favor of
technologies that could reduce greenhouse gas
emissions, implementing information programs
to enhance awareness of the problems and
solutions, and making selective use of
government procurement to promote markets
for technological alternatives.
• The United States is implementing a
number of actions (described above) that can
be justified because they produce benefits that
are not subject to the uncertainties associated
with climate change. Further study will most
likely identify additional actions that fall into
that category. At some point it may be
desirable to consider actions that can not be
justified by their non-climate benefits, but
must depend for justification on the benefits
from reducing the degree of climate change.
It will be important, at that time, to have a
full understanding of the economic, social, and
other implications of such actions so that
decisions despite the uncertainties will be
based on the best information that can be
developed. Some of the types of action that
will need to be considered and some of the
questions that will need to be addressed are
discussed throughout this report.
• A number of other countries have made
public commitments to take actions to reduce
their greenhouse gas emissions by similar or
greater proportions. While such actions will
somewhat delay the increasing concentrations
of greenhouse gases, the problem of achieving
economic growth and improved well-being in
the developing world while avoiding or
limiting the emissions increases from such
growth remains a key, unsolved problem.
Several studies have been conducted
that identify the wide range of policy choices
that are available for reducing emissions. For
example, see A Compendium of Options for
Government Policy to Encourage Private Sector
Responses to Potential Climate Change (U.S.
DOE, 1989), the National Energy Strategy
(NES) which is currently under development
by the U.S. DOE and other agencies within
the Federal government, and Box 3 (which is
an illustrative analysis based on preliminary
estimates of the impacts of the policies
discussed in Box 3).
The Timing of Policy Responses
The costs and benefits of actions taken
to reduce greenhouse gas emissions are
difficult to evaluate because of the many
uncertainties associated with estimates of the
magnitude, timing, and consequences of global
climate change, as well as the difficulty of
assessing the net social costs of strategies that
involve widespread and long-term shifts in
technological development. Given this
situation it may be prudent to delay some
costly actions to reduce greenhouse gas
concentrations until the magnitude of the
problem and the costs of responses are better
established. The potential benefits of delay,
however, must be balanced against the
potential increased risks.
The models indicate that delaying the
policy response to the greenhouse gas
buildup would substantially increase the
global commitment to future warming. For
this reason, the U.S. is taking a number of
policy actions (described earlier) that will
produce a substantial response to the
greenhouse gas buildup, particularly actions
that can be justified for reasons not subject to
the scientific and economic uncertainties about
climate change. Analytical efforts to date have
not been able to determine the appropriate
level of trade-off between accepting additional
costs associated with additional climate change
and incurring additional costs to avoid that
additional climate change. The Stabilizing
Policy cases and the Rapid Reduction case
both assume that immediate action is taken to
begin reducing the rate of greenhouse gas
buildup. The impact of delay was investigated
by assuming that industrialized countries do
not respond until 2010 and that developing
countries wait until 2025. Once action is
initiated, policies are assumed to be
implemented at roughly the same rates as in
the Stabilizing Policy cases. The result would
be a significant increase in global wanning (see
Figure 11): the equilibrium warming
commitment in 2050 would increase by about
40-50% relative to the scenarios that assume
policy implementation beginning in 1990. It is
clear that many nations are already taking or
publicly committed to taking actions that are
not reflected in this scenario. For example,
the U.S. has committed to a number of policy
38
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Executive Summary
Box 3. Illustrative Analysis of Current U.S. Policy Initiatives
Several policy initiatives are currently under discussion or have been approved that could
reduce the U.S. contribution to greenhouse gas emissions. These initiatives cover a wide range
of activities that emit different types of greenhouse gases. Several examples of these initiatives
include: (1) a recently-proposed reforestation program to plant one billion trees per year that
would sequester carbon as the trees matured; (2) a total pbaseout of the major CFCs and
related chemicals that deplete the stratospheric ozone layer; (3) new landfill regulations that
would restrict the amount of CH4 emissions from decomposing wastes; and (4) several
initiatives that would reduce the amount of energy consumed and thereby reduce CO2
emissions, including revisions to the Clean Air Act to control acid rain and develop less
polluting transportation fuels and proposals by the U.S. DOE to adopt more efficient appliance
standards, improve lighting in Federal and commercial buildings, promote state least-cost utility
planning, obtain U.S. HUD adoption of U.S. DOE building standards, and expand use of
hydroelectric power and the transfer of photovoltaic technology.
These specific policy initiatives are used here as examples of the types of emission
reduction policies that can be justified for reasons other than climate change- The options
included are those for which estimates of emissions were readily available. Many other
potential options exist which have not been systematically evaluated. As an illustration of the
potential for reducing emissions, however, we have combined the emission reductions from all
of the initiatives mentioned above into a single estimate using the concept of Global Warming
Potentials (GWP) discussed in Box 1 and the Addendum to Chapter II to convert the emission
reductions estimated from each initiative to a CO2-equivalent basis (expressed as carbon). The
impact of these proposed initiatives on estimated U.S. greenhouse gas emissions is summarized
in the figure below, which indicates that this illustrative package of proposed initiatives could
reduce total U.S. greenhouse gas emissions about 13% below projected levels for the year 2000
to a level about 7% lower than estimated 1987 emissions on a CO2-equivalent basis. If only
CO2 emissions are considered, however, the percentage reduction is substantially less - about
4% below projected 2000 emissions. Estimated redactions when only CO2 is considered are
much lower than reductions that consider all gases on a CO2-equivalent basis because the
largest source of emission reductions -- CFCs as a result of the London Amendments to the
Montreal Protocol and 1990 Clean Air Act Amendments -- is not included. For a complete
discussion of these results, see the Addendum to Chapter VII.
3.0
~ 2.5
OJ2.0
0 ° 1 n
5 xi ••**
OQ.5
0
U.S. GREENHOUSE GAS EMISSIONS
(Carbon-Equivalent Basis)
CFCs
co
m
VOCs
•§ CH4
K3 co,
1987 Baseline 2000 Baseline 2000 with Policy
Emissions Emissions Options Package
39
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Policy Options for Stabilizing Global Climate
FIGURE 11
INCREASE IN REALIZED WARMING
DUE TO GLOBAL DELAY IN POLICY OPTIONS
(Based on 3.0 Degree Sensitivity)
Slowly Changing World
Rapidly Changing World
s -
1»88 2000 2026 2060 2076 2100
RCW
RCWP with
Global Delay
RCWP
1M6 2000 202* 2060 2076 2100
Y«*r
Figure 11. Assumes that industrialized countries delay action until 2010 and that developing countries
delay action until 2025. Once action is initiated, policies are assumed to be implemented at roughly
the same rate as in the Stabilizing Policy cases.
40
-------
Executive Summary
measures that will mitigate emissions.
Although this delay scenario clearly does not
correspond to currently planned actions, the
basic point illustrated is still valid.
Policy development and imple-
mentation can be a lengthy process,
particularly at the international level Any
decision to respond to the greenhouse gas
buildup cannot be fully translated immediately
into action. Roughly a decade was required
for the process that led to international
agreement to reduce emissions of CFCs,
embodied in the Montreal Protocol, and it will
take another decade to implement the agreed-
upon reductions. Agreements to reduce other
greenhouse gas emissions could take much
longer to achieve and implement.
The development of technologies to
reduce greenhouse gas emissions will take
many years. The majority of emissions are
associated with activities that are fundamental
to the global economy (transportation, heating
and cooling of buildings, industrial production,
land clearing, etc.); thus, reducing emissions by
curtailing these activities would be highly
disruptive and undesirable. While this report
has identified a large menu of promising
technologies that can meet our needs for
goods and services while generating much
lower emissions of greenhouse gases, many
require additional research and development
to become economically competitive. The
time required to bring innovative technologies
to market is unpredictable, but the process
usually takes many years. And once a
technology is cost-effective, it may take years
before it achieves a large market share and
decades more for the existing capital stock to
be replaced. Depending on the sector, it may
take 20-50 years or more to substantially alter
the technological base of industrial societies,
and the cost of reducing emissions could rise
dramatically as the time allowed for achieving
these reductions is decreased. While the rate
of change in rapidly developing countries can
be higher and may be influenced by
government policies, once industrial
infrastructure is built, it will be many years
before it is replaced.
The Need for an International
Response
If limiting U.S. and global emissions
of greenhouse gases is desired, government
action will be necessary. Throughout the
world, market prices of energy from fossil
fuels, products made with CFCs, forest and
agricultural products, and other commodities
responsible for greenhouse gas emissions do
not reflect the risks of climate change. As a
result, increases in population and economic
activity will cause emissions to grow in the
absence of countervailing government policies.
The risk of substantial warming is
unavoidable if developing countries do not
participate in stabilizing strategies.
Increasing the availability of energy services is
a high priority for developing countries
attempting' to meet basic human needs.
Increased energy use in developing countries
could lead to dramatic increases in greenhouse
gas emissions unless stabilizing policies are
adopted. The share of greenhouse gas
emissions arising from developing countries
(weighted by their estimated impact on global
wanning) increases from about 40% currently
to 50% by 2025 and almost 60% by 2100 in
the RCW scenario; the developing countries'
contribution to greenhouse gas emissions also
rises to about 50% in the SCW (see Figure
12). We examined the implications for global
warming if industrialized countries adopted
climate stabilizing policies without the
participation of developing countries.
Assuming that policies adopted in
industrialized countries have some impact even
in developing countries that do not participate
in an international agreement, equilibrium
warming commitment in 2050 is about 40%
higher than in the Stabilizing Policy cases (see
Figure 13). This implies that action by
industrialized countries on their own can
significantly slow the rate and magnitude of
climate change, but that without the
participation of the developing countries, the
risk of substantial global wanning is
unavoidable. Even if developing countries
participate, the degree to which it will be
possible, at any point in time, to avoid
41
-------
Policy Options for Stabilizing Global Climate
FIGURE 12
SHARE OF GREENHOUSE GAS EMISSIONS BY REGION
100
sew
100
80 -
60
SCWP
20
Other
Developing
CP A*l«
USSR*
CP Europe
United State*
United SUte«
0 MWifmiHiit un iitiiiiiiiii.i^^BaKMHiifiiwa 0
19852000 2025 2050 2075 2100 19852000 2028 2050 2075 2100
Year Year
See Appendix B for further discussion of these scenarios.
42
-------
Executive Summary
FIGURE 13
INCREASE IN REALIZED WARMING
WHEN DEVELOPING COUNTRIES DO NOT PARTICIPATE
(Based on 3.0 Degree Sensitivity)
Slowly Changing World
Rapidly Changing World
o 3
8CW
SCWPwIth
NoPartMpaHon
by Developing
Countrlo*
tCWP
RCW
RCWP with
No Participation
by Dovotopbig
Countries
RCWP
IMS 2000
2026 2060
Year
2078
2100
1M0 2000
2026 2060
Year
2076
2100
Figure 13. Assumes that industrialized countries follow the Stabilizing Policies scenarios while
developing countries follow the No Response scenarios, except that there is some transfer of low-
emissions technology to developing countries despite their failure to adopt stabilizing policies.
43
-------
Policy Options for Stabilizing Global Climate
emissions increases in developing countries
that would otherwise accompany economic
growth is unknown.
Although most of the costs and
benefits of responding to climate change
cannot be quantified at this time, some
potential actions would have other benefits.
Benefits could include reductions in
conventional pollutants, increased energy
security, and reductions in the balance of
payments deficit, as well as reduced risk of
warming. Similarly, reversing deforestation
has a wide range of benefits, including
maintenance of biological diversity, reduction
in soil erosion and reservoir siltation, and
local climatic amelioration. The phaseout of
production of CFCs, halons, carbon
tetrachloride, and methyl chloroform under
the Montreal Protocol will be most significant
in reducing the risk of stratospheric ozone
depletion and will also make an important
contribution to reducing the risk of climate
change. The U.S. is taking, or is committed to
taking, a number of other actions that have
benefits other than those related to climate
change. In total, these U.S. actions are
estimated to have significant effects on U.S.
emissions of greenhouse gases. Some of the
options discussed here, such as reduced
agricultural emissions, improved biomass
production, and heavy reliance on photo-
voltaics, would require further research and
development to ensure their availability.
Relatively small investments in such research
could yield important payoffs.
NOTES
1. Estimates of equilibrium wanning
commitments greater than 6°C represent
extrapolations beyond the range tested in most
climate models, and this warming may not be
fully realized because the strength of some
positive feedback mechanisms may decline as
the Earth warms. These estimates are
represented by >6°C.
REFERENCES
Conway, T.J., P. Tans, L.S. Waterman, K.W.
Thoning, K.A. Masarie, and R.H. Gammon.
1988. Atmospheric carbon dioxide
measurements in the remote global
troposphere. 1981 - 1984. Tellus 40:81-115.
Hansen, J., I. Fung, A Lacis, D. Rind, S.
Lebedeff, R. Ruedy, and G. Russell. 1988.
Global climate changes as forecast by Goddard
Institute of Space Studies Three-Dimensional
Model. Journal of Geophysical Research
93:9341-9364.
Hansen, J., A. Lacis, D. Rind, G. Russell, P.
Stone, I. Fung, R. Ruedy, and J. Lerner. 1984.
Analysis of feedback mechanisms. In Hansen,
J., and T. Takahashi, eds. Climate Processes
and Climate Sensitivity. Geophysical
Monograph 29, Maurice Ewing Volume 5.
American Geophysical Union, Washington,
D.C. 130-163.
IPCC (Intergovernmental Panel on Climate
Change). 1990. Scientific Assessment of
Climate Change. Draft Report of Working
Group I. April 30.
Keeling, CD. 1983. The global carbon cycle:
What we know and could know from
atmospheric, biospheric, and oceanic
observations. In Proceedings of the CO2
Research Conference: Carbon Dioxide, Science
and Consensus. March 19-23, 1982, Berkeley
Springs, West Virginia. DOE CONF-820970,
U.S. DOE, Washington, D.C. II.3-II.62.
Komhyr, W.D., R.H. Gammon, T.B. Harris,
L.S. Waterman, T.J. Conway, W.R. Taylor, and
K.W. Thoning. 1985. Global atmospheric CO2
distribution and variations from 1968-1982
NOAA/GMCC CO2 flask sample data. Journal
of Geophysical Research 90:5567-55%.
Lashof, D. 1989. The dynamic greenhouse:
feedback processes that may influence future
concentrations of atmospheric trace gases and
climate change. Climatic Change 14:213-242.
44
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Executive Summary
NOAA (National Oceanographic and
Atmospheric Administration). 1987.
Geophysical Monitoring for Climatic Change
No. 15, Summary Report 1986. Schnell, R.C.,
ed. U.S. Department of Commerce, NOAA
Environmental Research Laboratories,
Boulder. 155 pp.
Ramanathan, V., R.J. Cicerone, H.B. Singh,
and J.T. Kiehl. 1985. Trace gas trends and
their potential role in climate change. Journal
of Geophysical Research 90:5547-5566.
Rotty, R.M. 1987. A look at 1983 CO2
emissions from fossil fuels (with preliminary
data for 1984). Tellus 393:203-208.
Siegenthaler, U. 1983. Uptake of excess CO2
by an outcrop-diffusion model of the ocean.
Journal of Geophysical Research 88:3599-3608.
Smith, J. and D. Tirpak, eds. 1989. The
Potential Effects of Global Climate Change on
the United States. U.S. Environmental
Protection Agency, Washington, D.C.
U.S. DOE (U.S. Department of Energy). 1989.
A Compendium of Options for Governmental
Policy to Encourage Private Sector Responses to
Potential Climate Change, Report to the
Congress of the United States. U.S. DOE/EH-
0102, Washington, D.C.
45
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CHAPTER I
INTRODUCTION
THE GREENHOUSE EFFECT AND
GLOBAL CLIMATE CHANGE
The greenhouse effect is a natural
phenomenon that plays a central role in
determining the Earth's climate. Sunlight
passes through the atmosphere and warms the
Earth's surface. The Earth then radiates
infrared energy, some of which escapes back
into space. But certain gases (known as
greenhouse gases) that occur naturally in the
atmosphere absorb most of the infrared
radiation and emit some of this energy back
toward the Earth, warming the surface. This
effect is, to a great extent, responsible for
making the Earth conducive to life. In its
absence, the Earth would be approximately
30°C colder.
Concerns about the greenhouse effect
arise because anthropogenic emissions of
greenhouse gases may further warm the
Earth.1 Greenhouse gases - primarily carbon
dioxide (CO2), methane (CH4), nitrous oxide
(N2O), chlorofluorocarbons (CFCs), and
tropospheric ozone (O3) - are produced as by-
products of human activities. When these
gases are emitted into the atmosphere and
their concentrations increase, the greenhouse
effect is compounded. The result is an
increase in mean global temperatures.
There is scientific consensus that
increases in greenhouse gas emissions will
result in climate change (Bolin et al., 1986;
NAS, 1979, 1983, 1987; WMO, 1985).
However, considerable uncertainty exists with
regard to the ultimate magnitude of the
wanning, its timing, and the regional patterns
of change. In addition, there is great
uncertainty about changes in climate variability
and regional impacts. Nonetheless, there is a
growing political consensus that greenhouse
gas emissions must be reduced. As stated by
the major industrial nations (the "G-7"
countries) at the Paris summit in July 1989:
"We strongly advocate common efforts to limit
emissions of carbon dioxide and other
greenhouse gases which threaten to induce
climate change, endangering the environment
and ultimately the economy." (Economic
Declaration from Summit of the Arch, July 16,
1989, Paris, France).
CONGRESSIONAL REQUEST FOR
REPORTS
The United States Environmental
Protection Agency (U.S. EPA) has studied the
effects of global warming for several years.
The goal of its efforts has been to use the best
available information and models to assess the
effects of climatic change and to evaluate
policy strategies for both limiting and adapting
to such change.
In 1986, Congress asked U.S. EPA to
develop two reports on global wanning.
Congress directed U.S. EPA to include in one
of these studies:
An examination of policy options
that if implemented would stabilize
current levels of atmospheric
greenhouse gas concentrations.
This study should address the need
for and implications of significant
changes in energy policy, including
energy efficiency and development
of alternatives to fossil fuels;
reductions in the use of CFCs;
ways to reduce other greenhouse
gases such as methane and nitrous
oxide; as well as the potential for
and effects of reducing
deforestation and increasing
reforestation efforts.
These issues are the focus of this report
This report differs from most previous
studies of the climate change issue in that it
is primarily a policy assessment Although
some aspects of the relevant scientific issues
are reviewed, this document is not intended as
a comprehensive scientific assessment A
recent review of the state of the science is
contained in the U.S. Department of Energy's
State of the Ait series (MacCracken and
Luther, 1985a, 198Sb; Strain and Cure, 1985;
Trabalka, 1985).
M
-------
Policy Options for Stabilizing Global Climate
Congress also asked U.S. EPA 10
prepare a companion report on the health and
environmental effects of climate change in the
U.S., which would examine the impact of
climate change on agriculture, forests, and
water resources, as well as on other ecosystems
and society. In response to the latter request,
U.S. EPA produced its report entitled, The
Potential Effects of Global Climate Change on
the United States (Smith and Tirpak, 1989).
That report provides insights into the ranges
of possible future effects that may occur under
alternative climate change scenarios, and
establishes qualitative sensitivities of different
environmental systems and processes to
changes in climate. The report also examines
potential changes in hydrology, agriculture,
forestry, and infrastructure in the Southeast,
Great Lakes, California, and Great Plains
regions of the United States.
Goals of this Study
Congress presented U.S. EPA with a
very challenging task. From a policy
perspective, it is not enough to know how
emissions would have to change from current
levels in order to stabilize the atmosphere.
Instead, policy options must be evaluated in
the context of expected economic and
technological development and the
uncertainties that prevent us from knowing
precisely how a given level of emissions will
affect the rate and magnitude of climate
change. It is also necessary for the scope of
this study to be global and the time horizon to
be more than a century, because of the long
lags built into both the economic and climatic
systems (we chose 1985-2100 as the time frame
for the analysis). We do not attempt
predictions with such a scope, but scenarios
are useful to explore policy options.
Based on these considerations U.S. EPA
established four major goals:
• To assemble data on global trends in
emissions and concentrations of all major
greenhouse gases and activities that affect
these gases.
• To develop an integrated analytical
framework to study how different assumptions
about the global economy and the climate
system could influence future greenhouse gas
concentrations and global temperatures.
• To identify promising technologies and
practices that could limit greenhouse gas
emissions.
• To identify policy options that could
influence future greenhouse gas concentrations
and global warming.
To achieve these goals U.S. EPA
conducted an extensive literature review and
data gathering process. The Agency held
several informal panel meetings and enlisted
the help of leading experts in the
governmental, non-governmental, and
academic research communities. U.S. EPA
also conducted five workshops, which were
attended by over three hundred people, to
gather information and ideas regarding factors
affecting atmospheric composition and options
related to greenhouse gas emissions from
agriculture and land-use change, electric
utilities, end uses of energy, and developing
countries. Experts in NASA, the Department
of Energy, and the Department of Agriculture
were actively engaged. A draft of this report
was produced in February 1989 and was
reviewed by U.S. EPA's Science Advisory
Board, other federal agencies, and a wide
variety of individuals and organizations from
outside the government. This final report has
greatly benefitted from this review process, but
U.S. EPA assumes responsibility for the
content of this document.
Report Format
The structure of this report is designed
to answer the following questions in turn:
What is the greenhouse effect? What evidence
is there that the greenhouse effect is
increasing? How will the Earth's climate
respond to changes in greenhouse gas
concentrations? What activities are
responsible for the greenhouse gas emissions?
What technologies are available for limiting
greenhouse gas emissions? How might
emissions and climate change in the future?
And what domestic and international policy
options, if implemented, would help to
stabilize global climate?
This chapter provides a general
introduction to the climate change issue and
reviews selected previous studies. Chapter II
discusses the greenhouse gases, their sources
and sinks, chemical properties, current
1-2
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Chapter I: Introduction
CLIMATE CHANGE TERMINOLOGY
An attempt has been made throughout this report to avoid technical jargon, yet the use of
some specialized terminology is inevitable. The specialized terms used in this Report are
defined below.
Climate System
The interactive components of our planet which determine the climate. This includes the
atmosphere, oceans, land surface, sea ice, snow, glaciers, and the biosphere. Climate change
can be measured in terms of any part of the system, but it is most convenient to use surface
air temperature as a measure of climate, since it is the parameter for which we have the best
record and it is most directly relevant to the component of the biosphere that we know best
-- humans.
Radiative Forcing (also called "external forcing* "farting," or 'perturbation')
A change imposed on the climate system (as opposed to generated by the internal dynamics
of the climate system) that modifies the radiative balance of the climate system. Examples
include: changes in the output of the son or the orbit of the Earth about the sun, increased
concentrations of particles in the atmosphere due to volcanoes or human activity, and increased
concentrations of greenhouse gases in the atmosphere due to human activity. Radiative forcing
is often specified as the net change in energy flax at the tropopause (W/m2) or the equilibrium
change in surface temperature in the absence of feedbacks ^C).
Climate Feedbacks
Processes that alter the response of die climate system to radiative forcings. We distinguish
between physical climate feedbacks and biogeochemical climate feedbacks. Physical climate
feedbacks are processes of the atmosphere, ocean, and Ian4 surface, such as increases in water
vapor, changes in cloudiness, and decreases in land- and sea-ice accompanying global warming.
Biogeochemical feedbacks involve changes in global biology and chemistry, such as the effect
of changes in ocean circulation on carbon dioxide concentrations and changes in albedo from
shifts in ecosystems. The impact of climate feedbacks is generally measured in terms of their
effect on climate sensitivity. Positive feedbacks increase climate sensitivity, while negative
feedbacks reduce it.
Climate Sensitivity (or equitibritm sensitivity)
The ultimate change in climate that can be expected from a given radiative forcing. Climate
sensitivity is generally measured las the change in global average surface air temperature when
equilibrium between incoming and outgoing radiation is re-established following a change in
radiative forcing. A common benchmark, which we use in this report, is the equilibrium
temperature increase associated with a doubling of the concentration of carbon dioxide from
pie-industrial levels. The National Academy of Sciences has estimated that this sensitivity is
in the range of 1-5-4.5'C, with a recent analysts suggesting 1.5-5.5°C; a reasonable central
uncertainty range is 2-4°C
1-3
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Policy Options for Stabilizing Global Climate
CLIMATE CHANGE TERMINOLOGY
(continued)
Transient Response
The time-dependent response of climate to radiative forcing. Climate responds gradually to
changes in radiative forcing, primarily because of the heat capacity of the oceans. The transient
mode is characterized by an imbalance between incoming and outgoing radiation. Given the
changing concentrations of greenhouse gases, the Earth's climate will be in a transient mode
for the foreseeable future. Most general circulation models (see below), however, have so far
examined equilibrium conditions because transient effects are much more difficult to analyze.
Albedo
The fraction of incoming solar radiation that is reflected back into space.
Flux
Flow per unit time per unit area. The flow can be of energy /e.g., watts per square meter
[W/m2]) or mass (e.g., grams per square meter per day [g ore**}).
General Circulation Model (GCM)
A computer model of the Earth's climate based on equations that describe, among other things,
the conservation of energy, momentum, and mass, and which explicitly calculates the
distribution of wind, temperature, precipitation and other climatic variables. Such models are
applied to the atmosphere, to the oceans, or to both coupled together.
Solar Luminosity, Solar Constant
Solar luminosity is the total amount of energy emitted by the sun. The so-called "solar
constant" is the average amount of energy received at the top of the Earth's atmosphere at the
mean Earth-sun distance; this amount varies with changes in solar luminosity.
Troposphere, Tropopause, Stratosphere
The troposphere is the lower atmosphere, from the ground to an altitude of about 8 kilometers
(km) at the poles, 12 km in mid latitudes and 18 km in the tropics. The tropopause marks the
top of the troposphere; temperature decreases with altitude below the tropopause and increases
with altitude above the tropopause to the lop of the stratosphere. The stratosphere extends
from the tropopause to about 50 km. The troposphere and stratosphere together contain more
than 99.9% of the mass of the atmosphere.
1-4
-------
Chapter I: Introduction
atmospheric concentrations and distributions,
and related uncertainties. Chapter III relates
the greenhouse gases to the process of climate
change. Once this link is made, Chapter IV
examines those human activities that affect
trace-gas emissions and ultimately influence
climate change. Chapter V gives a detailed
description of existing and emerging
technologies that should be considered in the
formulation of a comprehensive strategy for
mitigating global wanning. Chapter VI
discusses the scenarios developed for this
report to assist us in thinking about possible
future emissions and climate change, both with
current policies and with policies that could
decrease or increase future greenhouse gas
emissions. Chapter VII outlines domestic
policy options, and the concluding chapter
(Chapter VIII) discusses international
mechanisms for responding to climate change.
Three appendices provide additional detail on
the analysis for interested readers. Appendix
A describes the modelling framework used to
develop the scenarios presented in Chapter VI.
Appendix B provides additional details on how
each of the scenarios was implemented.
Appendix C presents the results of many
sensitivity analyses that explore in detail how
alternative assumptions on key parameters
could affect the rate and magnitude of global
climate change presented in Chapter VI.
THE GREENHOUSE GASES
Once emitted, greenhouse gases remain
in the atmosphere for decades to centuries.
As a result, if emissions remained constant at
1985 levels, the greenhouse effect would
continue to intensify for more than a century.
Carbon dioxide concentrations would reach
440-500 parts per million by volume (ppm) by
2100, compared with about 350 ppm today,
and about 290 ppm 100 years ago. CFC
concentrations would increase by more than a
factor of three from current levels, while
nitrous oxide concentrations would increase by
about 20%; and methane concentrations might
remain roughly constant. Indeed, in many
cases drastic cuts in emissions would be
required to stabilize atmospheric composition.
Carbon Dioxide
Carbon dioxide is the most abundant
and single most important greenhouse gas in
the atmosphere. Its concentration has
increased by about 25% since the industrial
revolution. Detailed measurements since 1958
show an increase from 315 to 351 ppm (see
Figure 1-1). These data clearly demonstrate
that human activities are now of such a
magnitude as to produce global consequences.
Current emissions are estimated at 5.5 billion
tons of carbon (Pg C) from fossil-fuel
combustion and 0.4-2.6 Pg C from
deforestation.2 Most of this CO2 remains in
the atmosphere or is absorbed by the ocean.
Even though only about half of current
emissions remain in the atmosphere, currently
available models of CO2 uptake by the ocean
suggest that substantially more than a 50% cut
in emissions is required to stabilize
concentrations at current levels (see Table 1-1;
Figure 1-2).
TABLE 1-1
Approximate Reductions in
Anthropogenic Emissions
Required to Stabilize Atmospheric
Concentrations at Current Levels
GAS
REDUCTION
REQUIRED
Carbon Dioxide 50-80%
Methane 10-20%
Nitrous Oxide 80-85%
Chlorofluorocarbons 75-100%
Carbon Monoxide (CO) Freeze
Nitrogen Oxide (NOX) Freeze
Methane
The concentration of methane has more
than doubled during the last three centuries.
Methane, which is currently increasing at a
rate of 1% per year, is responsible for about
20% of current increases in the greenhouse
effect. Of the major greenhouse gases, only
CH4 concentrations can be stabilized with
modest cuts in anthropogenic emissions: a 10-
20% cut would suffice to stabilize
concentrations at current levels due to
methane's relatively short atmospheric lifetime
(assuming that the lifetime remains constant,
which may require that hydrocarbon and
carbon monoxide emissions be stabilized).
1-5
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Policy Options for Stabilizing Global Climate
FIGURE l-l
CONCENTRATION OF CO2 AT MAUNA LOA OBSERVATORY
AND C02 EMISSIONS FROM FOSSIL-FUEL COMBUSTION
(a) 2
o
Q.
W
<5
&
o>
o
o
o
o"
o
360
350
340
330
320
310
(b) c e
X
O
\
w
i
8
ui
1958 1962 1966
1970 1974
Y»»r
1978 1982 1986 1989
Figure 1-1. a) Monthly concentrations of atmospheric CO, at MaunaLoa Observatory, Hawaii. The
yearly oscillation is explained mainly by the annual cycle or photosynthesis and respiration of plants
in the northern hemisphere. (Sources: Keeling, 1983, personal communication; Komhyr et aL, 1985;
NOAA, 1987; Conway et aL, 1988.) b) Annual emissions of CO2, in units of carbon, due to fossil-
fuel combustion. (Sources: Rotty, 1987; Rotty, personal communication.)
The steadily increasing concentration of atmospheric CO, at Mauna Loa since the 1950s is
caused primarily by the CO2 inputs from fossil-fuel combustion. Note that CO2 concentrations have
continued to increase since 1979, despite relatively constant emissions; this is because emissions have
remained substantially larger than net removal.
1-6
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Chapter I: Introduction
FIGURE 1-2
IMPACT OF CO2 EMISSIONS REDUCTIONS
ON ATMOSPHERIC CONCENTRATIONS
500
475 -
450 -
o
= 425 -
.
a
400 -
375 -
350 -A
325
1985 2000
2100
Figure 1-2. The response of atmospheric CO2 concentrations to arbitrary emissions scenarios based
on two one-dimensional models of ocean CO2 uptake. See Chapter VI for a description of scenarios
and models. (Sources: Hansen et aL, 1984; Lashof, 1989; Siegenthaler, 1983).
1-7
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Policy Options for Stabilizing Global Climate
Nitrous Oxide
The concentration of nitrous oxide has
increased by 5-10% since pre-industrial times.
Nitrous oxide is currently increasing at a rate
of 0.25% per year, which represents an
imbalance of about 30% between sources and
sinks. Assuming that the observed increase in
N2O concentrations is due to anthropogenic
sources and that natural emissions have not
changed, then an 80-85% cut in anthropogenic
emissions would be required to stabilize N2O
at current levels.
Chlorofluorocarbons
Chlorofluorocarbons were introduced
into the atmosphere for the first time during
this century. The most common species are
CFC-12 (CF2C12) and CFC-11 (CFC13), which
had atmospheric concentrations in 1986 of 392
and 226 parts per trillion by volume (ppt),
respectively. While these concentrations are
tiny compared with that of CO2, each
additional CFC molecule has about 15,000
times more impact on climate, and CFCs are
increasing very rapidly -- about 4% per year
since 1978. A focus of attention because of
their potential to deplete stratospheric ozone,
the increasing concentrations of CFCs also
account for about 20% of current increases in
the greenhouse effect. For CFC-11 and CFC-
12, cuts of 75% and 85%, respectively, of
current global emissions would be required to
stabilize concentrations. However, in order to
stabilize stratospheric chlorine levels - of
particular concern for stratospheric ozone
depletion -- a 100% phaseout of fully-
halogenated compounds (those that do not
contain hydrogen) and a freeze on the use of
methyl chloroform would be required.
Other Gases Influencing Composition
Emissions of carbon monoxide (CO),
nitrogen oxides (NOX), and other species, in
addition to the greenhouse gases just
described, are also changing the chemistry of
the atmosphere. This change in atmospheric
chemistry alters the distribution of ozone and
the oxidizing power of the atmosphere,
changing the atmospheric lifetimes of the
greenhouse gases. If the concentrations of the
long-lived gases were stabilized, it might only
be necessary to freeze emissions of the short-
lived gases at current levels to stabilize
atmospheric composition.
PREVIOUS STUDIES
Evidence that the composition of the
atmosphere is changing has led to a series of
studies analyzing the potential magnitude of
future greenhouse gas emissions. A few of
these studies have carried the analysis further,
making projections of the timing and severity
of future global warming. The first generation
of these studies focused principally on energy
use and CO2 emissions (see, e.g., NAS, 1979;
Clark et al., 1982; IIASA, 1983; Nordhaus and
Yohe, 1983; Rose et al., 1983; Seidel and
Keyes, 1983; Edmonds and Reilly, 1983b, 1984;
Legasov et al. 1984; Goldemberg et al., 1985,
1987; and Keepin et al., 1986). Subsequent
studies have recognized that other radiatively-
active trace gases significantly amplify the
effects of CO2 (see, e.g., Lacis et al., 1981;
Ramanathan et al., 1985; Dickinson and
Cicerone, 1986; WMO, 1985; and Mintzer,
1987). In the following sections, some of the
most important of these earlier analyses are
reviewed in order to provide a basis for
comparison with this study.
Estimates of the Climatic Effects of
Greenhouse Gas Buildup
The first serious analysis of the effect of
increasing CO2 concentrations on global
warming was conducted by the Swedish
chemist Svante Arrhennius (1896).
Arrhennius, concerned about the rapidly
increasing rate of fossil-fuel use in Europe,
recognized that the resulting increase in the
atmospheric concentration of CO2 would alter
the thermal balance of the atmosphere. Using
a simplified, one-dimensional model,
Arrhennius estimated that if the atmospheric
concentration of CO2 doubled, the surface of
the planet would warm by about 5°C. (The
expected equilibrium climate change associated
with a doubling of CO2 has become a
benchmark. That is, many studies examine the
consequences of greenhouse gas increases with
a total warming effect equivalent to that from
a doubling of the concentration of CO2.)
In 1979, a study by the U.S. National
Academy of Sciences (NAS) evaluated the
impact on global climate of doubling the
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Chapter I: Introduction
concentration of CO2 relative to the pre-
industrial atmosphere (NAS, 1979). The NAS
study concluded that the planet's surface
would most likely be 1.5-4.5°C wanner under
such conditions. Subsequent re-evaluations by
NAS (1983, 1987) as well as the "State-of-the-
Art" report issued by the U.S. Department of
Energy (U.S. DOE) (MacCracken and Luther,
1985a) have reaffirmed this estimate.
Recent work by Dickinson (1986)
suggests that the effects of a greenhouse gas
buildup radiatively equivalent to doubling the
pre-industrial concentration of CO2 might
warm the planet to a greater extent than had
previously been expected. Focusing on the
uncertainties in current understanding of
atmospheric feedback processes, Dickinson
estimated that the warming effect of such a
buildup was likely to be between 1.5° and
5.5°C. Dickinson's "best guess" was that the
actual equilibrium warming would be between
2.5° and 4.5°C.
Studies of Future CO2 Emissions
For the next eighty years after
Arrhennius issued his warning, little attention
was paid to the potential global consequences
of fossil-fuel combustion. By the mid-1970s,
measurements of atmospheric CO2
concentrations at Mauna Loa begun by
Keeling during the International Geophysical
Year (1957-1958) provided indisputable
evidence of a long-term increasing trend (see
Figure 1-1), while the oil embargo of 1973 and
the nuclear power debate focused attention on
future energy supplies. Increasing interest was
placed on the problems of projecting future
global energy use and on estimating the
resulting CO2 emissions.
A major international study of future
energy use was conducted by the International
Institute for Applied Systems Analysis (IIASA,
1981, 1983). Employing an international
group of almost 200 scientists, the IIASA team
developed a set of computer models to
estimate regional economic growth, energy
demand, energy supply, and future CO2
emissions. Although the models were never
completely integrated, the first phase of the
IIASA study produced two complete scenarios
of global energy use. The IIASA low scenario
generated CO2 emissions of about 10
petagrams of carbon per year (Pg C/yr) in
2030. The IIASA high scenario projected
emissions of about 17 Pg C/yr in 2030. In the
second phase of the IIASA study a third
scenario was outlined, emphasizing increased
use of natural gas. In this third scenario, CO2
emissions in 2030 were only about 9.4 Pg Qyrt
In 1983 Edmonds and Reilly, two U.S.
economists, developed a detailed partial
equilibrium model to investigate the effects of
alternative energy policies and their
implications for future CO2 emissions
(Edmonds and Reilly, 1983a). This model
disaggregates the world into nine geopolitical
regions. It offers a highly detailed picture of
the supply side of the world's commercial
energy business but only limited detail on the
demand side. It considers nine primary and
four secondary forms of commercial energy
(including biomass grown on plantations) but
ignores non-commercial uses of biomass for
fuel. Using explicit assumptions about
regional population changes and economic
growth and combining them with assumptions
about technological change and the costs of
extracting various grades of fuel resources in
each region, the model calculates supply and
demand schedules for each type of fuel.
For their first major report, Edmonds
and Reilly (1983b) developed a Base Case
energy future for the period 1975 to 2050. In
this scenario, CO2 emissions in 2050 were
approximately 26.3 Pg C/yr. The authors
generated several other scenarios in this study
that reflected the effect of various taxes
imposed on fuel supply and use. These taxes
reduced CO2 emissions by varying amounts,
with emissions in some scenarios falling as low
as 15.7 Pg C/yr in 2050. In 1984 Edmonds and
Reilly produced a new set of scenarios for U.S.
DOE by varying other key parameters in the
model (Edmonds and Reilly, 1984). In these
new scenarios, CO, emissions in 2050 vary
from about 7 to 47 Pg C/yr, with a new "Base
Case" value of about 15 Pg C/yr. The principal
force contributing to the difference between
the results of the two studies conducted by
Edmonds and Reilly is the higher coal price
applied in the second study.
A number of other studies have used
the Edmonds-Reilly (E-R) model to project
future energy use and CO2 emissions. The
most important of these were studies
conducted by the U.S. EPA (Seidel and Keyes,
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Policy Options for Stabilizing Global Climate
1983) and Rose et al. (1983). The U.S. EPA
study used the E-R model to generate 13
scenarios for the period 1975-2100, which were
used as a basis for investigating whether
actions taken now to reduce fossil-fuel
consumption could significantly delay a future
global warming. Six baseline and seven policy-
driven scenarios were investigated in this
study. The scenarios generated in the U.S.
EPA study projected CO2 emissions in 2050 at
levels of 10-18 Pg C/yr. The authors
concluded from these scenarios that the timing
of a 2°C wanning is not very sensitive to the
effects of the energy policies they tested.
Rose and his colleagues at the
Massachusetts Institute of Technology (MIT)
also used the E-R model to study the effect of
various energy policy options on the timing
and extent of future CO2 emissions (Rose et
al., 1983). Eleven scenarios were investigated,
covering the period from 1975 to 2050 and
incorporating a much wider range of
assumptions and policies than those tested in
the U.S. EPA study. Rose et al. studied the
effects of increased energy efficiency, increased
fossil-fuel prices, higher nuclear energy supply
costs, a moratorium on building nuclear
plants, lower photovoltaic costs, higher oil
prices, and a cutoff of oil imports from the
Middle East. The MIT study went beyond the
E-R model results to provide detailed
estimates of the materials required for
construction and operation of energy facilities
in each scenario. In the MIT scenarios,
emissions of CO2 in 2050 ranged from less
than 3 to about 15 Pg C/yr. The most
important new conclusion of Rose et al. was
that a feasible "option space exists in which
the CO2/climate problem is much ameliorated"
through energy policy choices and
improvements in technology.
In 1983 the National Academy of
Sciences completed a Congressionally-
mandated study to evaluate, among other
things, the effects of fossil-fuel development
activities authorized by the Energy Security
Act of 1980 (NAS, 1983). One of the chapters
in this study, authored by energy economists
Nordhaus and Yohe, used a compact model of
global economic growth and energy use to
analyze CO2 emissions between 1975 and 2100
(Nordhaus and Yohe, 1983). Unlike the
partial equilibrium approach employed in the
E-R model, the Nordhaus and Yohe (N-Y)
model used a generalized Cobb-Douglas
production function to estimate future energy
demand. In this approach global GNP is
estimated us a function of assumptions about
average rates of change in labor productivity,
population, and energy consumption.
Demand for energy is separated into two
categories, fossil and non-fossil. Projections of
CO2 emissions (based on the weighted average
release rate from fossil fuels) were used as
inputs to a simple airborne fraction model of
the carbon cycle.
The N-Y analysis used an approach
called "probabilistic scenario analysis" to
evaluate the effects on CO2 emissions of
alternative assumptions used in the model.
The results of 1000 cases were examined. The
CO2 emissions trajectories in these cases were
presented as percentiles in the overall
distribution among the 1000 scenarios. Using
this approach to uncertainty analysis,
Nordhaus and Yohe concluded that the 50th
percentile for carbon emissions in 2050 was
approximately 15 Pg C/yr. The 95th percentile
case suggested that emissions in 2050 would
likely be less than 26 Pg C/yr, while the 5th
percentile case indicated that emissions would
likely be greater than 5 Pg C/yr.
The probabilistic approach was
subsequently applied to the more detailed
E-R model using Monte Carlo analysis
(Edmonds et al., 1986; Reilly et al., 1987).
The results of this analysis suggest a larger
total range of uncertainty and a substantially
lower median emissions estimate compared
with the Nordhaus and Yohe (1983) results.
When the likely correlations between model
parameters are taken into account, Edmonds
et al. obtain emissions of 7.7 Pg C/yr in 2050
for the 50th percentile case with 5th and 95th
percentile bounds of 2.3 and 58.1 Pg C/yr,
respectively. Note that the median result is
about half of the Base Case scenario obtained
in earlier analysis by Edmonds and Reilly
(1984).
In 1984 Legasov et al. published one of
a continuing series of Soviet analyses of future
global energy use and its environmental
implications. Legasov et al. analyzed two
scenarios in which energy demand reaches 6
and 20 kilowatts per capita by the end of the
next century. Annual per capita energy
consumption is treated as a logistic function,
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Chapter I: Introduction
approaching these levels asymptotically in
2100. Assuming a global population of 10
billion persons, the minimal variant implies a
global energy demand of 60 terawatts (TW),
about six times the current level by 2100.
CO2 emissions in this scenario follow a bell-
shaped trajectory, peaking at about 13.3 Pg
C/yr in 2050.
Goldemberg and his colleagues have
used a completely different approach to
projecting future energy use and its
consequences for CO2 emissions (Goldemberg
et al., 1985, 1987, 1988). The Goldemberg et
al. analysis is based on an end-use-oriented
approach to evaluating the demand for energy
services, rather than the availability of energy
supply. Based on detailed studies of energy
demand in four countries (U.S., Sweden, India,
and Brazil), Goldemberg and his colleagues
developed a scenario of future energy
requirements in both industrialized and
developing countries. Although the study does
not represent a forecast of future energy
demand, it provides an "existence proof,"
demonstrating the feasibility of a world
economy that continues to grow while
consuming much less energy than it would if
historical trends continue.
Emphasizing the potential to improve
the efficiency of energy supply and use, per
capita energy demand in the industrialized
countries is cut by 50% in the Goldemberg et
al. scenarios. During the same 40-year period,
per capita demand for energy in the
developing countries grows by about 10%, with
commercial fuels displacing traditional biomass
fuels at a rapid and increasing rate. Global
energy demand remains essentially constant in
the base case with CO2 emissions in 2020 of
5.9 Pg C/yr, only about 5% higher than today's
level.
A limitation of the Goldemberg et al.
studies is that the impact of market
imperfections and the rate of capital stock
turnover are not fully addressed.
Nonetheless, these studies, along with the
Rose et al. analysis, demonstrate that
economic growth can be decoupled from
increases in CO2 emissions. Experience
over the last 15 years in the U.S., Western
Europe, and Japan suggests that this
conclusion is correct.
A study by Keepin et al. (1986) reviewed
and re-evaluated the range of previous energy
and CO2 projections, including those
summarized here. It concluded that the
feasible range for future energy in 2050 was
somewhere between about 10 and 35 TW, with
CO2 emissions between 2 and 20 Pg C/yr,
Studies of the Combined Effects of
Greenhouse Gas Buildup
In the last few years a number of
analysts have investigated the combined effects
on global surface temperature of a buildup of
CO2 and other trace gases. Preliminary
analysis of the impact of concentration
increases during the 1970s was presented by
Lacis et al. (1981), and estimates of future
impacts were included in Seidel and Keyes
(1983). A seminal article by Ramanathan et
al. (1985) focused attention on the subject.
This study used a one-dimensional radiative-
convective model to estimate the impact of a
continuation of current trends in the buildup
of more than two dozen radiatively active trace
gases between 1980 and 2030. Ramanathan
and his colleagues calculated an expected value
for the equilibrium warming of about 1.5°C
over this period, with a little less than half of
that amount due to the buildup of CO2 alone.
(The Ramanathan et al. analysis included the
effects of water-vapor feedback, but not the
other known feedback mechanisms; see
CHAPTER III.) The most important
conclusion of the analysis by Ramanathan et
al. is that if current trends continue and
uncertainties in the future emissions
projections are accounted for, the warming
effects of the non-CO2 trace gases will amplify
the warming due to the buildup of CO2 alone
by a factor of between 1.5 and 3.
In 1986, Dickinson and Cicerone
extended the work of Ramanathan et al. to
evaluate a range of trace-gas scenarios
covering the period from 1985 to 2050. Using
the radiative-convective model developed by
Ramanathan et al., and considering a range of
emissions growth rates for the most important
greenhouse gases, Dickinson and Cicerone
(1986) estimated that equilibrium global
average surface temperatures would rise at
least 1°C and possibly more than 5°C by 2050,
when the full range of atmospheric feedback
processes was considered.
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Policy Options for Stabilizing Global Climate
Each of the analyses described above
was based on the assumption that historical
trends in the growth of greenhouse gas
emissions continue for the next 40-50 years.
Mintzer (1987) has developed a model to
consider the alternative: that policy and
investment choices made in the next several
decades will substantially alter the growth rates
of future emissions. Mintzer's analysis uses a
composite tool called the Model of Warming
Commitment to link future rates of economic
growth to the increasing atmospheric
concentrations of carbon dioxide, nitrous
oxide, chlorofluorocarbons, methane, and
tropospheric ozone. The results are reported
as the date of atmospheric commitment to a
warming equivalent to doubling pre-industrial
CO2 concentrations and as the magnitude of
warming commitment in 2075.
Mintzer's initial analysis considered four
policy-driven global scenarios, including a Base
Case representing a continuation of current
trends. All four scenarios support a global
population of about 10 billion people and the
same levels of regional economic growth.
Most recent analyses, including the ones cited
above and Mintzer's Base Case, indicate that
a continuation of current trends would lead to
a warming commitment equivalent to doubling
the pre-industrial concentration of CO2 by
about 2030. In Mintzer's Base Case, by 2075,
the planet is committed to an eventual
warming of about 3-9°C. Alternatively, in the
High Emissions case, policies that increase
coal use, spur deforestation, extend the use of
the most dangerous CFCs, and limit
improvements in energy efficiency will
accelerate the onset of the "doubled CO2
equivalent" atmosphere to about 2010 and
commit the planet to a warming of about 5-
15°C in 2075. By contrast, in Mintzer's Slow
Buildup scenario, a wanning associated with
the doubled CO2 equivalent atmosphere is
postponed beyond the end of the simulation
period in 2075. In the Slow Buildup scenario
this level of risk reduction is achieved by
aggressively pursuing policies to increase
energy efficiency, limit tropical deforestation,
reduce the use of the most dangerous CFCs,
and shift the fuel mix from carbon-intensive
fuels like coal to hydrogen-intensive fuels like
natural gas, and ultimately, to energy sources
that emit no CO2.
More recently, Rotmans et al. (1988)
used a framework similar to the Model of
Warming Commitment to develop scenarios of
greenhouse warming based on alternative
policy assumptions. Also, Rotmans and
Eggink (1988) have analyzed the role of
methane in greenhouse warming.
Major Uncertainties
Major uncertainties underlie many
aspects of our understanding of the climate
change problem, including both scientific and
socioeconomic parameters. The physical
uncertainties include uptake of heat and CO2
by the ocean and any other sinks, geophysical
and biogeochemical feedback mechanisms, and
natural rates of emission of the greenhouse
gases. The social and economic uncertainties
include population growth, GNP growth,
structural changes in economic systems, rates
of technological change, future reliance on
fossil fuels, and future compliance with the
Montreal Protocol. Future rates of
greenhouse gas emissions cannot be predicted
with certainty. Future emissions rates will be
determined by the emerging pattern of human
industrial and agricultural activities as well as
by the effects of feedback processes in the
Earth's biogeophysical system whose details
are not well understood at the present time.
All existing climate models encompass
large uncertainties that limit the accuracy of
the models and the level of geographic detail
that can be considered. Even the best general
circulation models (GCMs) are limited by the
assumptions necessarily made about the
influence of clouds, vegetation, ice and snow,
soil moisture, and terrain, all of which affect
the energy balance of the Earth's surface. Two
of the largest uncertainties involve our limited
understanding of the roles that clouds and the
ocean play in the climate system.
Conclusions From Previous Studies
Despite the significant uncertainties that
underlie our understanding of climate change,
several important conclusions emerge from the
existing literature. First, emissions of a
number of other trace gases will amplify the
future wanning effect of any further buildup in
the atmospheric concentration of CO2.
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Chapter I: Introduction
Second, it is too late to prevent all future
global warming. Trace gases released over the
last century have already committed the planet
to an ultimate warming (of 1-2°C) that may be
greater than any other in the period of written
human history. Finally, policy choices and
investment decisions made during the next
decade that are designed to increase the
efficiency of energy use and shift the fuel mix
away from fossil fuels could slow the rate of
buildup sufficiently to avoid the most
catastrophic potential impacts of rapid climate
change. Alternatively, decisions to rapidly
expand the use of coal, extend the use of the
most dangerous CFCs, and rapidly destroy the
remaining tropical forests could "push up the
calendar," accelerating the onset of a
dangerous global wanning.
The rate at which climate may change
must be of particular concern to policymakers.
The temperature increases resulting from
doubling the concentration of CO2 that are
predicted by most GCMs are comparable to
the increase that has occurred since the last
ice age. The difference is that the period of
time within which this increase could happen
is much shorter. Atmospheric scientists
predict that within approximately 100 years we
could experience temperature increases
equivalent to those that have occurred over
the past 18,000 years (about 5°C; see
CHAPTER III). It is not clear that our
ecosystems and economic systems will be able
to adjust to such a rapid change in global
mean temperatures. Increases in world
population, coupled with limited
environmental and agricultural resources,
increase the vulnerability of social systems to
climatic change.
The potential impacts of climatic change
are highly uncertain and are beyond the scope
of this report. They are addressed in the
companion volume, The Potential Effects of
Global Climate Change on the United States
(Smith and Tirpak, 1989). The collective
findings of this study suggest that the climatic
changes associated with a global warming of
roughly 2-4°C would result in
a world different from the world
that exists today. Global climate
change could have significant
implications for natural
ecosystems; for where and how we
farm; for the availability of water
to irrigate crops, produce power,
and support shipping; for how we
live in our cities; for the wetlands
that spawn our fish; for the
beaches we use for recreation; and
for all levels of government and
industry.
Although sensitivities were identified in this
report, detailed regional predictions of climate
change cannot be made at this time. Thus,
potential responses to the greenhouse gas
buildup must be viewed in the context of risk
management or insurance-buying.
A second major concern is that the
greenhouse gases have very long lifetimes once
they are introduced into the atmosphere.
Although there is a substantial lag between the
time a greenhouse gas is introduced into the
atmosphere and when its full impact on
climate is realized, once the gases are in the
atmosphere they will remain there for a long
time. The longer the delay before mitigating
action is taken, the larger will be the
commitment to further global warming.
Policymakers must determine how best
to minimize the costs of global wanning to the
peoples of the world and the damage to
ecosystems. But global warming is a complex
problem for which there is no single, simple
solution. No single policy initiative will
completely mitigate man-made climate change.
The sources, sectors, and countries
contributing to the emissions of greenhouse
gases are numerous (see CHAPTER IV).
Compounding the difficulty of
identifying solutions to the greenhouse
problem is that the greenhouse gases do not
all have the same forcing effect on global
temperatures. In fact, CO2 is the least
effective absorbent of infrared radiation of all
of the greenhouse gases per additional
molecule added to the atmosphere. Because
the combined effect of the other greenhouse
gases is comparable to the effect of CO2,
mitigatory policies cannot be directed solely at
reducing CO? emissions. The sources of
methane, CFCs, nitrous oxide, and other gases
must therefore be carefully considered.
As we explore the options for limiting
greenhouse gas emissions in this report, it is
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Policy Options for Stabilizing Global Climate
important to remember two salient points: (1)
global warming is an international problem
whose solution will require extensive
cooperation between both industrialized and
developing countries; and (2) no single
economic sector can be held entirely
responsible for the greenhouse effect. In
focusing on strategies to stabilize climate in
this Report, we recognize that the optimal mix
of adaptation and prevention is uncertain.
The Earth is already committed to some
degree of climate change, so adaptation to
some level of change is essential. Adaptation
strategies can be adopted unilaterally, and the
costs will be spread out into the future when
countries may be better able to afford them.
Imposing climate change on our grandchildren,
however, raises serious concerns regarding
intergenerational equity. And the highest
rates of potential change may be considered
unacceptable, requiring some degree of
prevention. Stabilizing strategies would
require global cooperation of an
unprecedented nature and could be costly for
some countries. The activities responsible for
greenhouse gas emissions are economically
valuable, the distribution of emissions is large,
and the responsible countries reflect diverse
economies and a variety of interests. At the
same time, there are policies that can reduce
greenhouse gas emissions while promoting
other environmental, economic, and social
goals.
CURRENT DOMESTIC AND
INTERNATIONAL ACTIVITIES
Subsequent to the Congressional request
to produce this report and the companion
document on potential effects of climate
change, there have been a wide variety of new
domestic and international initiatives related
to climate change.
Domestic Research and Policy Activities
The Global Climate Protection Act of
1987 requires that:
The President, through the
Environmental Protection Agency,
shall be responsible for developing
and proposing to Congress a
coordinated national policy on
global climate change.
This Act is a very broad mandate that requires
close cooperation between U.S. EPA and
other agencies (including NASA, NOAA, the
Corps of Engineers, and the Departments of
Energy, Agriculture, and the Interior, the
National Climate Program Office, and the
Domestic Policy Council).
The Global Climate Protection Act also
requires that the Secretary of State and the
U.S. EPA Administrator jointly submit, by the
end of 1989, a report analyzing current
international scientific understanding of the
greenhouse effect, assessing U.S. efforts to
gain international cooperation in limiting
global climate change, and describing the U.S.
strategy for seeking further international
cooperation to limit global climate change.
This report, along with those being developed
by other federal agencies, will provide a
foundation upon which a national policy can
be formulated.
During 1989, several states passed
legislation or signed executive orders
specifically addressing global warming. The
most common approach has been the creation
of procedures to study the feasibility of
reducing greenhouse gas emissions by a
specific amount by some target date. In
Oregon, a bill passed in July requires a state
strategy to reduce greenhouse emissions 20%
from 1988 levels by 2005. In Vermont, an
executive order calls for a similar plan to
reduce both greenhouse gas emissions and acid
rain precursors by 15% below current levels by
the year 2000; additional restrictions on CFCs
were adopted by the legislature. A New York
executive order accompanying release of a
state energy plan in September set a goal of
reducing CO2 emissions 20% by 2008. A
study of how to achieve that goal will be
conducted jointly by the Energy Office,
Department of Environmental Conservation,
and the Public Service Commission for
presentation to the Governor by April 30,
1990. A New Jersey executive order on global
warming requires state agencies to purchase
the most energy efficient equipment available
"where such equipment or techniques will
result in lower costs over the lifetime of the
equipment." In Missouri, the state legislature
created a commission to study the effects of
ozone depletion and global wanning on the
state and to identify means of reducing the
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Chapter I: Introduction
state's emissions; findings and recommen-
dations are due in late spring 1990.
International Activities
The greenhouse gas problem is an
international issue. In order to respond
effectively to this problem, the nations of the
world must act in concert. Several
international organizations have recognized
the need for multilateral cooperation and have
become involved with the global climate
change issue. The United Nations
Environment Programme (UNEP) is
responsible for conducting climate impact
assessments. The World Meteorological
Organization (WMO) is supporting research
on and monitoring of atmospheric and physical
sciences. The International Council of
Scientific Unions (ICSU) is developing an
international geosphere-biosphere program.
The U.S. government is supporting
the Intergovernmental Panel on Climate
Change (IPCC) established under the
auspices of UNEP and WMO. The IPCC,
which held its first meeting in November
1988, will help ensure an orderly
international effort in responding to the
threat of global climate change. At its first
meeting the IPCC established three working
groups: the first, to assess the state of
scientific knowledge on the issue, is chaired
by the United Kingdom; the second, to
assess the potential social and economic
effects from a warming, is chaired by the
Soviet Union; and the third, to examine
possible response strategies, including
options for limiting emissions and adapting
to change, is chaired by the United States.
An interim report by the IPCC summarizing
its key findings was reviewed at the Second
World Climate Conference in November
1990.
The U.S. government has also taken a
more active role in international discussions
on climate change. At the Malta Summit in
December 1989, President Bush offered (1) to
convene an international meeting at the White
House in the spring of 1990 for top level
scientific, environmental, and economic
officials to discuss global climate change
issues, and (2) to host a conference to
negotiate a framework treaty on global climate
change.
The White House Conference on
Science and Economics Research Related to
Global Change was held in Washington in
April of 1990, stressing the need for enhanced
levels of cooperation with respect to the
science and impacts of climate change and the
economic implications of possible response
strategies. The U.S.-hosted international
meeting to begin the negotiations for a
framework convention on climate change was
held in the Washington area in February,
1991.
International concern over the impacts
of climate change was also reflected by the
major industrialized countries at the annual
Economic Summit held in Paris, France. The
G-7 countries not only endorsed efforts to
limit greenhouse gases, but also stated that
"... a framework or umbrella convention on
climate change to set out general principles or
guidelines is urgently required to mobilize and
rationalize the efforts made by the
international community" (Economic
Declaration, Summit of the Arch, July 16,
1989). The call for an international
framework convention on climate has also
been endorsed by the Ministerial Conference
on Atmospheric Pollution and Climatic
Change held in the Netherlands (November
1989), the 15th session of the UNEP
Governing Council, and the XLI session of the
WMO Executive Council.
The Economic Summit of the G-7
countries in Houston in July 1990 reiterated
support for the negotiation of a framework
convention on climate change. The Summit
also stated that the G-7 countries are ready to
begin negotiations on a global forest
convention or agreement, which is needed to
curb deforestation, protect biodiversity,
stimulate positive forestry actions, and address
threats to the world's forests. While such a
convention is needed for reasons other than
climate change, it would also have climate
change benefits.
In addition, several countries have held
or plan to hold international conferences on
global climate change and are analyzing
domestic policy options. These include
Canada, The Federal Republic of Germany,
the United Kingdom, Italy, Japan, India,
Egypt, and the Netherlands.
1-15
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Policy Options for Stabilizing Global Climate
The global warming issue is an
international concern. In order to develop a
responsible program, the U.S. government
must consider the feasibility of achieving both
domestic and international acceptance and
implementation of policy initiatives.
Otherwise, the effectiveness of programs
instituted by any one country could be
compromised by the lack of participation by
other countries. International collaboration
must be pursued.
NOTES
1. Anthropogenic means resulting from
human activities. Thus, by anthropogenic
emissions we mean those emissions caused by
man's activities, as opposed to those resulting
from natural causes.
2. One billion tons of carbon = 1015 grams of
carbon = 1 petagram of carbon (Pg C).
3. 1 terawatt = 1012 watts = 31.5xl018 joules
per year = 31.5 exajoules (EJ) per year = 29.9
Quadrillion British Thermal Units (Quads) per
year.
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Clark, W.C., K.H., Cook, G., Marland, AM.
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Dickinson, R. 1986. The climate system and
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Goldemberg, J., T.B. Johansson, AK.N.
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What we know and could know from
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Komhyr, W.D., R.H. Gammon, T.B. Harris,
L.S. Waterman, T.J. Conway, W.R. Taylor, and
K.W. Thoning. 1985. Global atmospheric CO2
distribution and variations from 1968-1982
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S. Lebedeff. 1981. Greenhouse effect of trace
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Lashof, D. 1989. The dynamic greenhouse:
Feedback processes that may influence future
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climatic change. Climatic Change 14:213-242.
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Chernoplyokov. 1984. The influence of
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MacCracken, M. C, and F. M. Luther, eds.
1985a. Projecting the Climatic Effects of
Increasing Carbon Dioxide. U.S. Department of
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MacCracken, M.C., and P.M. Luther, eds.
1985b. Detecting the Effects of Increasing
Carbon Dioxide. U.S. Department of Energy,
Washington, D.C.
Mintzer, I.M. 1987. A Matter of Degrees: The
Potential for Controlling the Greenhouse Effect.
World Resources Institute, Washington, D.C.
NAS (National Academy of Sciences). 1979.
Carbon Dioxide and Climate: A Scientific
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NAS (National Academy of Sciences). 1983.
Changing Climate. National Academy Press,
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Current Issues in Atmospheric Change. National
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NOAA (National Oceanographic and
Atmospheric Administration). 1987.
Geophysical Monitoring for Climatic Change
No. 15, Summary Report 1986. Schnell, R.C.,
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Nordhaus, W.D., and G. Yohe. 1983. Future
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Ramanathan, V., R.J. Cicerone, H.B. Singh,
and J.T. Kiehl. 1985. Trace gas trends and
their potential role in climate change. Journal
of Geophysical Research 90:5557-5566.
Reilly, J., J. Edmonds, R. Gardner, and A.
Brenkeri. 1987. Uncertainty analysis of the
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Global Energy Futures and CO^-Induced
Climate Change. MITEL 83-015. Prepared for
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of the greenhouse effect: The Dutch
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Rotmans, J., and E. Eggink. 1988. Methane as
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Public Health and Environmental protection,
Bilthoven, The Netherlands.
Rotty, R.M. 1987. A look at 1983 CO2
emissions from fossil fuels (with preliminary
data for 1984). Tellus 398:203-208.
Seidel, S., and D. Keyes. 1983. Can We Delay
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Siegenthaler, U. 1983. Uptake of excess CO2
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Potential Effects of Global Climate Change on
the United States. U.S. Environmental
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Strain, B.R., and J.D. Cure, eds. 1985. Direct
Effects of Increasing Carbon Dioxide on
Vegetation. U.S. Department of Energy,
Washington, D.C.
Trabalka, J.R., ed. 1985. Atmospheric Carbon
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WMO, Geneva. 392+ pp.
1-18
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CHAPTER II
GREENHOUSE GAS TRENDS
FINDINGS
The composition of the atmosphere is
changing as a result of human activities.
Increases in the concentrations of carbon
dioxide (CO2), methane (CH4), nitrous oxide
(N2O), and chlorofluorocarbons (CFCs) are
wefl documented. In addition, tropospheric
(lower atmospheric) chemistry and
stratospheric (upper atmospheric) chemistry
are being modified as a result of the addition
into the atmosphere of these gases as well as
emissions of carbon monoxide, nitrogen oxides,
and other compounds. Specifically, we find
that:
• The concentration of carbon dioxide in
the atmosphere has increased by 25% since the
industrial revolution. Detailed measurements
since 1958 show an increase of about 35 parts
per million by volume. Both land clearing and
fossil-fuel combustion have contributed to this
rise, but the fossil-fuel source has dominated
in recent years. Carbon dioxide is increasing
at a rate of about 0.4% per year and is
responsible for about half of the current
increases in the greenhouse effect. Only 50-
60% of the fossil-fuel CO2 remains in the
atmosphere. The total net uptake of CO2 by
the oceans and the net uptake/release of CO2
by the terrestrial biosphere cannot be precisely
determined at this time.
• The concentration of methane has more
than doubled during the last three centuries.
There is considerable uncertainty about the
total emissions from specific sources of
methane, but the observed increase is probably
due to increases in a number of sources as
well as to changes in tropospheric chemistry.
Agricultural sources, particularly rice
cultivation and animal husbandry, have
probably been the most significant
contributors to historical increases in
concentrations. There is the potential,
however, for rapid growth in emissions from
landfills, coal seams, permafrost, natural gas
exploration and pipeline leakage, and biomass
burning associated with future forest clearing.
Methane is increasing at a rate of ~1% per
year and is responsible for about 20% of the
current increases in the greenhouse effect. Per
molecule in the atmosphere, CH4 is about 20
times more powerful than CO2 at current
concentrations.
• The concentration of nitrous oxide has
increased by 5-10% since pre-industrial times.
The cause of this increase is highly uncertain,
but it appears that the use of nitrogenous
fertilizer, as well as the activities of land
clearing, biomass burning, and fossil-fuel
combustion have all contributed. Nitrous
oxide, which is about 200 times more powerful
on a per molecule basis than CO2 as a
greenhouse gas, can also contribute to
stratospheric ozone depletion. Nitrous oxide
is currently increasing at a rate of about 0.2-
0.3% per year, which represents an imbalance
between sources and sinks of about 30%.
Nitrous oxide is responsible for about 5% of
the current increases in the greenhouse effect.
• CFCs were introduced into the
atmosphere for the first time during this
century; the most abundant species are CFC-
12 and CFC-11, which had atmospheric
concentrations in 1986 of 392 and 226 parts
per trillion by volume, respectively. While
these concentrations are tiny compared with
that of CO2, these compounds are about
15,000 times more powerful, on a per molecule
basis, than carbon dioxide as a greenhouse gas
and are increasing very rapidly - about 5%
per year from 1978 to 1983. Of major concern
because of their potential to deplete
stratospheric ozone, the CFCs also represent
about 20% of the current increases in the
greenhouse effect.
• The chemistry of the atmosphere is
changing as a result of emissions of carbon
monoxide, nitrogen oxides, and volatile organic
compounds, among other species, and because
of changes in the greenhouse gases just
described. This change in atmospheric
chemistry alters the amount and distribution of
ozone and the oxidizing power of the
atmosphere, which changes the lifetimes of
CH4 and other greenhouse gases. Changes in
global ozone, both stratospheric and
tropospheric, are quite uncertain and may have
contributed to an increase or decrease in the
warming commitment during the last decade.
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Policy Options for Stabilizing Global Climate
INTRODUCTION
The composition of the Earth's
atmosphere is changing. Detailed background
atmospheric concentration measurements of
trace gases combined with analyses of ancient
air trapped in Antarctic and Greenland ice
now give a compelling picture, not only of
recent trends, but also of major changes that
have occurred since pre-industrial times.
Mounting evidence that the atmosphere is
changing has increased the urgency to
understand the processes that control
atmospheric composition and the significance
of the changes that are taking place. In this
chapter we examine what is known and not
known about the gases expected to be most
important in altering climate during the
coming decades. For each gas, we present
data regarding its concentration history and
geographic distribution, its sources and sinks,
and its chemical and radiative interactions in
the atmosphere. This information is
summarized in Table 2-1, which appears at the
end of this chapter.
The concentrations of a number of
greenhouse gases have already increased
substantially over pre-industrial levels. The
estimated relative radiative forcing from the
major gases (excluding water vapor and
clouds) is illustrated in Figure 2-1 for the
period 1880-1980 and for the expected
concentration changes during the 1980s (see
ADDENDUM TO CHAPTER II). Carbon
dioxide (CO2) accounted for about two-thirds
of the total forcing over the last century, but
its relative importance has declined to about
half the total in recent years because of the
more rapid growth in other gases during the
last few decades (see CHAPTER IV).
Particularly important has been the recent
growth in concentrations of chlorofluoro-
carbons (CFCs). Methane (CH4) has
remained the second most important
greenhouse gas, responsible for 15-20% of the
forcing. With the recent signing of the
Montreal Protocol on Substances that Deplete
the Ozone Layer and the subsequent London
Amendments, growth in CFC concentrations is
likely to be substantially restrained compared
with what has been assumed until recently
(e.g., Ramanathan et al., 1985; see CHAPTERS
IV and V). The relative importance of CO2 is
therefore likely to increase again in the future
unless these emissions are also restricted (see
CHAPTER VI).
The radiative impact of greenhouse
gases is characterized here in terms of the
effect of concentration changes on surface
temperatures in the absence of climate
feedbacks. Climate feedbacks are defined and
discussed in Chapter III, where the climatic
effects of changes in greenhouse gases are put
into the broader context of other factors that
influence climate. The human activities that
are apparently responsible for the
concentration trends documented in this
chapter are described in Chapter IV.
CARBON DIOXIDE
Concentration History and Geographic
Distribution
Carbon dioxide is the most abundant
and single most important greenhouse gas
(other than water vapor) in the atmosphere.
Its role in the radiative balance and its
potential for altering the climate of the Earth
have been recognized for over a hundred years.
Chemical measurements of atmospheric CO2
were made in the 19th century at a few
locations (see Fraser, Elliott et al., 1986; From
and Keeling, 1986). However, the modern
high-precision record of CO2 in the
atmosphere did not begin until 1958, the
International Geophysical Year (IGY), when
C.D. Keeling of Scripps Institution of
Oceanography pioneered measurements of
CO2 using an infrared gas analyzer at Mauna
Loa Observatory (MLO) in Hawaii and at the
South Pole. Since 1974, background
measurements of atmospheric CO2 have been
made continuously at four stations (Pt.
Barrow, Alaska; Mauna Loa, Hawaii;
American Samoa; and the South Pole) as part
of the Geophysical Monitoring for Climatic
Change (GMCC) program of the National
Oceanic and Atmospheric Administration
(NOAA), U.S. Department of Commerce. In
addition to the continuous monitoring
stations, NOAA/GMCC also operates a
cooperative sampling network. Flask samples
of air are collected weekly from these sites and
shipped to the GMCC facility in Boulder,
Colorado, for analysis. The sampling network
began before 1970 at a few initial sites,
expanded to a network of 15 stations in 1979,
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Chapter II: Greenhouse Gas Trends
FIGURE 2-1
GREENHOUSE GAS CONTRIBUTIONS TO GLOBAL WARMING
Other (8%)
CFC-11&-12
(8%)
(3%)
CFC-11&-12
(14%)
CH4
(15%)
Figure 2-1. Based on estimates of the increase in concentration of each gas during the specified
period. The "Other" category includes other halons, tropospheric ozone, and stratospheric water
vapor. The contribution to warming of the "Other" category is highly uncertain. (Sources: 1880-1980:
Ramanathan et al., 1985; 1980s: Hansen et al, 1988.)
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Policy Options for Stabilizing Global Climate
and, as of 1986, consisted of ~26 stations
(Komhyr et al., 1985; Gammon et al., 1986;
Conway et al., 1988). In addition to the U.S.
programs, surface measurements of
atmospheric CO2 around the globe are made
by many countries, including Australia,
Canada, France, Italy, Japan, New Zealand,
Spain, West Germany, and Switzerland.
Mauna Loa
The MLO CO2 record is shown in
Figure 1-1 in Chapter I. CO2 steadily
increased from 315 parts per million by
volume (ppm) in 1958 to 351 ppm in 1988.
This corresponds to an increase at the rate of
0.36% per year, or a mean increase of 1.1 ±0.2
ppm per year. From 1958 to 1988, CO2 at
Mauna Loa increased by 36 ppm; over the
same period, fossil-fuel combustion (shown
also in Figure 1-1) was a source of 123
petagrams (Pg)1 of carbon (C) as CO2 to the
atmosphere, which is equivalent to 59 ppm of
CO2. The apparent fraction of the fossil-fuel
sources of CO2 that remained in the
atmosphere during this period is thus 57%.
Because other net sources of CO2, particularly
deforestation (see below), may have been
important during this period, the actual
fraction of anthropogenic (induced by human
activities) carbon emissions remaining in the
atmosphere is uncertain.
The apparent airborne fraction of CO2
has not remained constant. Averaged over
1959-1975, the fraction was 54.7%, while that
for 1975-1988 was 61.3% (Keeling, 1989).
This increase could signal either enhanced
CO2 release from deforestation or reduced
capacity of the land-ocean system to absorb
excess CO2. It could also signal a positive
feedback between greenhouse wanning and the
natural carbon cycling on land and at sea.
Because of the implications for accelerated
greenhouse warming, understanding the
increase in the airborne fraction of CO2 must
be of highest priority.
Superimposed on the increasing secular
trend of atmospheric CO2 are regular seasonal
oscillations: the concentration peaks in
May/June, decreases steadily through the
summer, and reaches a minimum in
September/October. The seasonal
peak-to-trough amplitude is —5.8 ppm. The
seasonal cycle of CO2 at Mauna Loa and at
other northern hemispheric locations is caused
primarily by the natural dynamics of the
terrestrial biosphere: there is net removal of
CO2 from the atmosphere via photosynthesis
during the growing season, and net return of
CO2 to the atmosphere via respiration and
decomposition processes during the rest of the
year.
Despite its regular appearance, there are
interannual variations in the CO2
concentration measured at MLO. Annual
mean concentration changes do not remain
uniform throughout the duration of the record
but have large fluctuations around the mean
(Keeling, 1983). These excursions of
atmospheric CO2 from the mean generally
occur during El Nino-Southern Oscillation
events, where the large-scale perturbations of
atmospheric temperature, precipitation, and
other circulation statistics also alter the
biological, chemical, and physical aspects of
carbon cycling among the atmosphere, land,
and ocean reservoirs. More recently, Keeling
et al. (1989) have also found an 11-year cycle
in CO2, which correlates with the 11-year cycle
found in the surface air temperature record
compiled by Hansen and Lebedeff (1987).
These excursions highlight the possibility of
climatic feedbacks in the carbon cycle; they do
not mask the increasing secular trend, which
mainly reflects the trend in fossil-fuel
combustion.
The seasonal amplitude also does not
remain constant and has a ±10% variation
about the mean. Recent analysis reveals a
statistically significant positive trend in the
seasonal amplitude between 1976 and 1986
(Bacastow et al., 1985; Enting, 1987). The
causes of this amplitude trend have not been
unambiguously identified; hypotheses involve
shifts in the seasonaliry of photosynthesis and
respiration, faster cycling of carbon as a result
of climatic warming, and the direct effects of
CO2 on plants (also referred to as the CO2
fertilization effect).
Ice-core Data
Bubbles in natural ice contain samples
of ancient air. Analysis by gas
chromatography and laser infrared
spectroscopy of gases occluded in gas bubbles
in polar ice has provided a unique
reconstruction of atmospheric CO2 history
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Chapter II: Greenhouse Gas Trends
prior to the modern high-precision
instrumental record (Oeschger and Stauffer,
1986). Deep ice cores have been drilled from
many locations in both Greenland and
Antarctica.
From the ice-core data, it is deduced
that in pre-industrial times (i.e., before about
1800), the CO2 concentration was 285 ±10
ppm and has increased at an accelerating rate
since the industrial era (Neftel et al., 1985;
Raynaud and Barnola, 1985; Pearman et al.,
1986) (see Figure 2-2). The ice-core data
reveal the possible existence of natural
fluctuations on the order of ±10 ppm
occurring at decadal time scales during the last
few thousand years (Delmas et al., 1980;
Neftel et al., 1982; Stauffer et al., 1985;
Raynaud and Barnola, 1985; Oeschger and
Stauffer, 1986).
Recent analysis of the 2083-meter-deep
ice core from Vostok, East Antarctica,
provides for the first time information on CO2
variations in the last 160,000 years (Barnola et
al., 1987; see Figure 3-3 in CHAPTER III).
Large CO2 changes were associated with the
transitions' between glacial and interglacial
conditions. CO2 concentrations were low
(—200 ppm) during the two glaciations and
high (—285 ppm) during the two major warm
periods. The Vostok ice-core data also
emphasize that current levels of atmospheric
CO2 are higher than they have ever been in
the past 160,000 years. The CO2 increase
since 1958 is larger than the natural CO2
fluctuations seen in the Greenland and
Antarctic ice-core record.
The variation of CO2 over this record is
approximately in step with the surrogate
temperature record deduced from the same ice
core (Jouzel et al., 1987), confirming the role
of CO2 in influencing the radiation balance of
the earth.
GMCC Network
The CO2 concentrations from the ~25
globally distributed sites in the NOAA/GMCC
cooperative flask sampling network have been
reviewed in Komhyr et al. (1985) and Conway
et al. (1988). The distribution for 1981-1985
is shown in Figure 2-3. There are large-scale,
coherent, temporal and spatial variations of
CO2 in the atmosphere. Concentrations of
CO2 at all the stations are increasing at the
rate of —1.5 ppm per year (ppm/yr), similar to
the rate of increase at Mauna Loa.
Annually averaged CO2 concentrations
are higher in the Northern Hemisphere than
in the Southern Hemisphere. The
interhemispheric difference was —1 ppm in the
1960s and is —3.0 ppm now, reflecting the
Northern Hemisphere mid-latitude source
(about 90%) of fossil-fuel CO2. This gradient
has remained approximately constant in the
past decade. Also evident in the north-south
distribution of atmospheric CO2 is the relative
maximum of —1 ppm in the equatorial
regions, caused mainly by the outgassing of
CO2 from the supersaturated surface waters of
the equatorial oceans. Although tropical
deforestation may also contribute to the
equatorial maximum in atmospheric CO2,
models of the global carbon cycle suggest
that the observations are inconsistent with
a net deforestation source greater than
approximately 1.5 Pg C/yr (Pearman et al.,
1983; Keeling and Heimann, 1986; Tans et al.,
1989).
There is a coherent seasonal cycle at all
the observing stations: the Northern
Hemisphere cycles resemble that at Mauna
Loa. The seasonal amplitude is largest, —16
ppm, at Pt. Barrow, Alaska, and decreases
toward the equator to ~6 ppm at Mauna Loa
(see Figure 2-3). The CO2 concentration is
flat through the year in the equatorial region
and is of opposite seasonality in the Southern
Hemisphere. The seasonal cycle in the
Northern Hemisphere is caused primarily by
seasonal exchanges with the terrestrial
biosphere (Fung et al., 1987; Pearman and
Hyson, 1986), while in the Southern
Hemisphere, oceanic and terrestrial exchanges
are equally important in determining the
seasonal oscillations in the atmosphere
(Pearman and Hyson, 1986). The CO2
seasonal cycle shows a consistent amplitude
increase with time for some sites (Cleveland et
al., 1983; Thompson et al., 1986).
The geographical variations of CO2
growth rates at the GMCC sites show more
clearly the El Nino perturbations, as noted
already in the Mauna Loa data. For example,
the El Nino-caused cessation of upwelling that
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Policy Options for Stabilizing Global Climate
FIGURE 2-2
CARBON DIOXIDE CONCENTRATION
(Parts per Million)
en
i
o-
0>
CSJ
r--
CM
1720
T 1—
1760
1800
1840
1880
1920
1960
2000
Y«ar
Figure 2-2. The history of atmospheric CO2 presented here is based on ice-core measurements (open
spaces, closed triangles) and atmospheric measurements (crosses). The data show that CO2 began to
increase in the 1800s, probably due to the conversion of forests to agricultural land. The rapid rise
since the 1950s, due primarily to fossil-fuel combustion, is at a rate unprecedented in the ice-core
record. (Sources: Neftel et al., 1985; Friedli et al., 1986; Keeling, pers. communication; all cited in
Siegenthaler and Oeschger, 1987.)
II-6
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Chapter II: Greenhouse Gas Trends
FIGURE 2-3
C02 ATMOSPHERIC CONCENTRATIONS BY LATITUDE
Figure 2-3. The distribution of CO2 by latitude from 1981-1985 shows that CO2 is increasing globally.
Superimposed on the increasing trend are coherent seasonal oscillations reflective of seasonal
dynamics of terrestrial vegetation. The seasonal cycle is strongest at high northern latitudes, and is
weak and of opposite phase in the Southern Hemisphere, reflecting the distribution of terrestrial
vegetation. The data are from the NOAA/GMCC flask sampling network. (Sources: Komhyr et
al, 1985; NOAA, 1987; Conway et al., 1988.)
n-7
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Policy Options for Stabilizing Global Climate
resulted in the devastation of the fishing
industry' and marine wildlife in the eastern
equatorial Pacific is also evidenced by reduced
outgassing of CO2 to the atmosphere (Feely et
al., 1987) and a concomitant decrease in the
global CO2 growth rate (Conway et al., 1988).
These variations in the growth rate contain
information about the response of the carbon
system to climatic perturbations, some of
which are currently under investigation.
Sources and Sinks
The atmosphere exchanges CO2 with the
terrestrial biosphere and with the oceans.
Averaged over decades, sources must
approximately equal sinks if the system is to
remain in quasi-steady state; however, the
individual flux in each direction may be large
(50-100 Pg C/yr). The fluxes of carbon to the
atmosphere associated with anthropogenic
activities are roughly ten times smaller than
the natural fluxes of carbon. However, the
anthropogenic fluxes are unidirectional and
thus are net sources of carbon to the
atmosphere (see Figure 2-4).
Fossil Carbon Dioxide
The combustion of fossil fuels, in liquid,
solid, and gas forms, is the major
anthropogenic source of CO2 10 the
atmosphere. A recent documentation and
summary of the fossil-fuel source of CO2 is
given by Rotty (1987a, 1987b). In 1985, about
5.2 Pg C were released in the form of CO2 as
a result of fossil-fuel combustion. Of this, the
U.S., USSR, and China contributed 23%, 19%,
and 10%, respectively (Rotty, pers.
communication). The emissions for 1987 were
5.5 Pg C. The history and mix of activities and
fuels giving rise to these emissions are
discussed in detail in Chapter IV.
Biospheric Cycle
The terrestrial biosphere absorbs CO2
from the atmosphere via photosynthesis on the
order of 80 Pg C/yr. Approximately the same
amount is returned to the atmosphere annually
via autotrophic and heterotrophic respiration
and decomposition processes. While the net
exchange of the unperturbed biosphere is close
to zero over a period of one year, the seasonal
asynchronicity of the exchange gives rise to the
regular oscillations seen in the atmospheric
CO2 records.
In general, the conversion of forests to
pastures and agriculture is a net source of CO2
to the atmosphere. CO2 is released as a result
of burning and decay of dead plant matter and
oxidation of soil organic matter. The amount
of this release exceeds the amount of CO2
absorbed as a result of regrowth of live
vegetation and accumulation of soil organic
matter. Recently, Houghton et al. (1987) and
Detwiler and Hall (1988) estimated a net
source of 0.4-2.6 Pg C/yr to the atmosphere
from land-use changes. Deforestation in the
tropics accounted for nearly all the flux. In
temperate and boreal regions the carbon
absorbed from the atmosphere via regrowth of
forests is countered by the carbon released by
the oxidation of wood products; the result is a
net release to the atmosphere of 0.1 Pg C/yr
(Melillo et al., 1988). The regional and
temporal patterns and causes of deforestation
are taken up in Chapter IV.
Natural changes in terrestrial biospheric
dynamics may result from climate warming
and/or from increased CO2 concentrations in
the atmosphere. The possibility of such
natural changes is suggested by the increasing
amplitude of CO2 oscillations in the
atmosphere (Bacastow et al., 1985; Cleveland
et al., 1983; Thompson et al. 1986; Enting,
1987), The amplitude change may signal a
tendency towards a biospheric sink of CO2, as
photosynthesis responds to increasing
temperatures and CO2 concentrations
(Pearman and Hyson, 1981; D'Arrigo et al.,
1987; Kohlmaier et al., 1987). The amplitude
change can also mean increased sources via
respiration and decay, which are strongly
temperature-dependent processes (Houghton,
1987). Several recent modeling studies (see
section below) have inferred, from north-south
profiles of atmospheric CO2, that vegetation
and soils in temperate latitudes in the
northern hemisphere have acted as a net sink
for excess CO2 from fossil-fuel burning.
Because growth and decay cycles are intimately
linked, it is difficult to tell whether
atmosphere-biosphere interactions will act as
a positive or a negative feedback without
further theoretical and field studies (see
BIOGEOCHEMICAL CLIMATE FEEDBACKS
in CHAPTER III).
II-8
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Chapter II: Greenhouse Gas Trends
FIGURE 2-4
(a)
THE CARBON CYCLE
ATMOSPHERE:770
SEDIMENTS:
organic C: 12,000,000
limestone: 50,000,000
FOSSIL FUEU50OO
(b)
BIOSPHERE:
living plants: 800
young soils: 1500
old soils; 1500
5.5 r
60
100
Figure 2-4. (a) Major reservoirs of the global carbon cycle. Reservoirs (or stocks) are in Pg C (b)
Fluxes of carbon are in Pg C/yr. (Source: Adapted from Keeling, 1983.)
II-9
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Policy Options for Stabilizing Global Climate
Ocean Uptake
The exchange of CO2 across the air-sea
interface depends on the degree of CO2
supersaturation in the surface waters of the
oceans and the rate at which CO2 is
transferred across the interface itself. Because
of the very nature of shipboard measurements,
data on oceanic CO2 partial pressure (pCO2)
are sparse, both spatially and temporally.
Most of the data have come from
oceanographic research programs, mainly
Scripps Institution of Oceanography in the
1960s (Keeling, 1968), Geochemical Sections
(GEOSECS) in the 1970s (Takahashi et al.,
1980, 1981), Transient Tracers in the Oceans
(TTO) in the early 1980s (Brewer et al., 1986),
and more recently from NOAA survey cruises
and from ships of opportunity.
Depending on the regional interplay
among temperature, carbon supply from
upwelling, and carbon consumption by
biological activities, the seasonal cycle of CO2
in surface water may peak at different times of
the year in different oceanic regions (Peng et
al., 1987; Takahashi et al., 1986, 1988). This
makes it extremely difficult to interpret the
sparse oceanic carbon data in the context of
the global carbon cycle. The interpretation is
aided by data from carbon-14 and other
transient tracers in the ocean.
Based on the available data and an
understanding of carbon dynamics in the
ocean, it is estimated that on an annual basis
about 100 Pg C/yr is exchanged between the
atmosphere and the ocean. This exchange
results in a net outgassing of approximately 1
Pg Cfyr from the equatorial oceans and a net
absorption of about the same amount by the
mid to high latitude oceans.
Superimposed on this exchange of 100
Pg C/yr in either direction is the penetration
of fossil-fuel CO2 into the oceans. The
capacity of the ocean to take up the excess
CO2 has been postulated by many authors
(e.g., Oeschger et al., 1975; Broecker et al.,
1979). Because of the variability of the
oceanic carbon system and the precision of
ocean carbon measurements, the oceanic
signature of fossil-fuel CO2 has not been
demonstrated unambiguously from direct
measurements. A particular difficulty is the
lack of baseline or historical data of oceanic
CO2 from which to estimate changes. As
water masses in the ocean interior move
primarily along constant density (isopycnal)
contours, concentration differences between
the ocean surface and interior locations along
the same isopycnal have been used to infer the
anthropogenic CO2 signal (Brewer, 1978;
Chen, 1982a, 1982b). Considerable
controversy exists about this procedure, as
mixing and biological processes also alter CO2
concentrations; correction schemes for these
other processes remain problematic due to
insufficient data (Broecker et al., 1982; Shiller,
1981, 1982; Chen et al., 1982). Takahashi et
al. (1983) have demonstrated that in the
Atlantic, the partial pressure of CO2 in the
ocean (pCO2) increased by 8 ±8
microatmospheres (/tatm) from 1958 to the
mid 1970s.
The expectation of fossil-fuel uptake by
the oceans is encouraged by observations of
anthropogenic tracers penetrating gradually
into the oceanic thermocline. These tracers
include tritium and carbon-14, by-products of
nuclear testing in the 1960s, and CFCs, recent
man-made compounds. The magnitude of the
fossil-fuel uptake is estimated using numerical
models calibrated by these tracers. These
models range in complexity from simple one-
dimensional box-diffusion models to three-
dimensional general circulation models of the
ocean (Siegenthaler, 1983; Maier-Reimer and
Hasselman, 1987; Peng, 1986; JOds and
Siegenthaler, 1989; Sarmiento et al., 1989).
The magnitude of the uptake varies depending
on the model architecture and the tracer used
to calibrate the model, but does not exceed
~35% of the fossil-fuel source. This
percentage is considerably less than that
required by the CO2 budget, i.e. —45% of the
fossil-fuel source plus 100% of the release
from deforestation.
It is generally assumed that the major
sink for anthropogenic CO2 is the large
expanse of southern oceans where there are
strong winds and cold waters. A recent study
(Tans et al., 1990), using the north-south
profile of CO2 in the atmosphere to constrain
11-10
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Chapter II: Greenhouse Gas Trends
THE RADIATIVE EFFECTS
OF GREENHOUSE GASES
The radiative effects of greenhouse
gases have received a great deal of
attention over the last decade. Recent
reviews are given by Dickinson and
Cicerone (1986) and Ramanathan et al.
(1987). In the absence of an
atmosphere the Earth would radiate
energy to space as a black body with a
temperature of about 250K (-23°C).
Figure 2-5 shows the actual emissions,
indicating the absorption bands of the
major greenhouse gases. Not shown is
water vapor, which has continuous
absorption throughout this spectral
range and dominates all other gases at
wavelengths <8 micrometers (nm) and
>18 nia (Dickinson and Cicerone,
1986). The 15 mti band of CO2
dominates absorption in the spectral
range from 12 to 18 nm, and its
absorption in the other parts of the
spectrum amounts to 15% or less of its
impact in this region.
The shaded region in Figure 2-5,
between about 7 and 13 «im> is called
the atmospheric window because it is
relatively transparent to outgoing
radiation: 70-90% of the radiation
emitted by the surface and clouds in
these wavelengths escapes to space
(Ramanathan et al., 1987). Many trace
gases happen to have absorption bands
in this window region and are therefore
very effective greenhouse absorbers. For
example, CFC-11 and CFC-12 are about
15,000 times more effective than CO2
per incremental increase in
concentration (see Table 2-2).
the budget, argues that the CO2 sink must be
predominately in the northern hemisphere.
Because the northern oceans are better
surveyed and are observed to be only a small
sink for CO2 (Takahashi et al., 1989), Tans et
al. hypothesize that there must be a significant
land sink to balance the CO2 budget and
match the north-south gradient. The need for
a land sink for anthropogenic CO2 has long
been suggested by the ocean models. This
hypothesis has since been supported by several
independent studies (Enting and Mansbridge,
1989; Etcheto et al., 1989).
Chemical and Radiative Properties/
Interactions
Carbon dioxide is chemically inert in the
atmosphere, but it has a very important impact
on the Earth's radiation budget and hence on
climate and the chemistry of the atmosphere.
After water vapor, CO2 is the most abundant
and most significant infrared (IR) absorbing
gas in the atmosphere. As discussed in
Chapter III, the Earth's climate is determined
by the point at which incoming solar (short-
wave) radiation is balanced by IR (long-wave)
emissions to space from the warm surface and
atmosphere. Increasing the concentration of
CO2 and other greenhouse gases in the
atmosphere elevates the average surface
temperature required to achieve this balance.
Doubling the atmospheric CO2 concentration
from 315 to 630 ppm would produce a
radiative forcing (the equilibrium surface
temperature increase in the absence of climate
feedbacks) of 1.2-1.3°C. At current
concentrations CO2 already absorbs most of
the radiation emitted from the Earth's surface
in the wavelengths where it is active. As a
result, each additional molecule of CO2 added
to the atmosphere has a smaller effect than
the previous one. Hence, radiative forcing
scales logarithmically, rather than linearly, with
increases in the concentration of atmospheric
CO2. For example, a 50 ppm increase in CO2
from 350 to 400 ppm yields a radiative forcing
of 0.23°C, while the same increment from 550
to 600 ppm yields a radiative forcing of only
0.16°C. Despite the reduced greenhouse
effectiveness of each molecule of CO2 as
concentrations increase, CO2 will remain the
dominant greenhouse gas in the future,
responsible for 50% or more of the increased
greenhouse effect during the next century for
plausible scenarios of future trace gas
emissions (Hansen et al., 1988; see CHAPTER
VI).
11-11
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Policy Options for Stabilizing Global Climate
FIGURE 2-5
Gas Absorption Bands
emission
wavelength 5
7.5
10 12.5 15 17.5 20
Figure 2-5. Infrared (long-wave) emissions to space from the Earth. Many of the absorption bands
of the greenhouse gases fall within the atmospheric window — a region of the spectrum, between 7
and 13 nm, in which there is little else to prevent radiation from the Earth escaping directly into
space. (Source: UNEP, 1987.)
11-12
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Chapter II: Greenhouse Gas Trends
TABLE 2-2
Radiative Forcing for a Uniform
Increase in Trace Gases From Current Levels
Compound
CO2
CH4
N20
CFC-11
CFC-12
CFC-13
Halon 1301
F-116
CC14
CHC13
F-14
HCFC-22
CH2C12
CH3CQ3
C2H2
SO2
Radiative Forcing
(No Feedbacks)
(°C/ppb)
.000005
.0001
.001
.07
.08
.10
.10
.08
.05
.04
.04
.03
.02
.01
.01
.01
Radiative Forcing
Relative to CO2
1
20
200
14,000
16,000
20,000
20,000
16,000
10,000
8,000
8,000
6,000
4,000
2,000
2,000
2,000
Source: Adapted from Ramanathan et al., 1985.
n-o
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Policy Options for Stabilizing Global Climate
METHANE
Concentration History and Geographic
Distribution
High-precision atmospheric measure-
ments of CH4 have been made in the past
decade at many different locations. The data
show clearly that the globally averaged
concentration of methane, 1670 parts per
billion by volume (ppb) in 1988, has been
increasing at the rate of about 14-16 ppb per
year (Blake and Rowland, 1986, 1988) (see
Figure 2-6). Since 1982, air samples from ~25
globally distributed sites of the NOAA/GMCC
cooperative network have been analyzed for
CH4 (Steele et al., 1987). In addition to flask
sampling, continuous measurements of
atmospheric CH4 are now made at Cape
Meares, Oregon (Khalil and Rasmussen,
1983); Pt. Barrow, Alaska; and Mauna Loa,
Hawaii (NOAA, 1987).
The data show that CH4, like CO2,
exhibits very coherent spatial and temporal
variations. CH4 is approximately uniform
from mid to high latitudes in the Southern
Hemisphere and increases northward. The
Northern Hemisphere average concentration is
approximately 100 ppb higher than that in the
Southern Hemisphere. The seasonal cycle in
the Southern Hemisphere (about 35 ppb peak
to peak) shows a minimum in the summer,
consistent with higher summer abundances of
the hydroxyl radical (OH) and temperature-
dependent destruction rates. In the Northern
Hemisphere, the seasonal cycle is more
complex, showing the interaction mainly
between chemical destruction and emissions
from high-latitude peat bogs.
Analysis of air bubbles in ice cores
shows that in pre-industrial years, CH4 was
~700 ppb and exhibited a 2.5 factor increase
to its present value in only the last 100 years
(Stauffer et al., 1985; Pearman et al., 1986)
(see Figure 2-6). The 2083-meter ice core
recovered by the Soviet Antarctic Expedition
at Vostok, Antarctica, shows that the CH4
concentration was as low as 340 ppb during
the penultimate ice age (—155 kyBP) and
nearly doubled to 610 ppb in the following
interglacial period (130 kyBP). The trend in
CH4 closely followed the trend in air
temperature deduced from deuterium
(Raynaud et al., 1988). These measurements
show that current concentrations of CH4, like
that of CO2, are higher than they have been in
the past 160,000 years.
Sources and Sinks
Methane is produced via anaerobic
decomposition in biological systems. It is also
a major component of natural gas and of coal
gas. While the major sources of CH4 have
been identified, their individual contributions
to the global budget are highly uncertain. A
recent review of the sources and sinks of CH4
is given by Cicerone and Oremland (1988) (see
Figure 2-7).
The major sink of CH4 is reaction with
OH radicals in the atmosphere.2 Based on
chemical considerations, it is estimated that
the global sink of methane is about 500
teragrams (Tg) CH4/yr.3 By inference, the
annual global source equals the sink plus the
annual increase, i.e., about 550 Tg CH4/yr.
Cicerone and Oremland (1988) estimate a
range of 400 to 640 Tg/yr for the annual global
source.
Estimates of methane emissions from
natural wetlands have ranged from 11-150
Tg/yr (e.g., Seiler, 1984; Khalil and Rasmussen,
1983). A recent study by Matthews and Fung
(1987) estimated that there are 530 million
hectares of natural wetlands that account for
a global emission of ~ 110 Tg CH4/yr. Of this,
about 50% of the CH4 is emitted from
productive peat bogs at high latitudes in the
Northern Hemisphere, a regional emission
that is likely to increase with greenhouse
warming. While this study has employed more
extensive field data than earlier estimates (e.g.,
Sebacher et al., 1986; Harriss et al., 1985),
uncertainties in the global estimate remain due
to the heterogeneity of natural wetlands and
their CH4 fluxes.
Rice paddies are environments very
similar to natural wetlands in terms of CH4
production and emission to the atmosphere.
In 1984, there were 148 million hectares of
rice harvest area globally, with ~50% in India
and China. Methane emission studies have
been performed in controlled mid-latitude
environments (Cicerone et al., 1983;
Holzapfel-Pschorn and Seiler, 1986). These
studies have identified the following factors,
among others, that affect CH4 fluxes to the
n-w
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Chapter II: Greenhouse Gas Trends
FIGURE 2-6
(a)
METHANE CONCENTRATION
(Parts per Million)
Atmospheric Data
1.7
i 1.6
1.5
(b)
1978 79808182838485868788
Year
ice-Cor* Data
1.4-
1.1-
1.0
0«
trM
1MO
Figure 2-6. Recent measurements of atmospheric CH4 show that CH4 has been increasing at the rate
of about 1%/yr in the last decade (upper panel). Ice-core data (lower panel) show that CH4 was
relatively constant in the 1800s, and began to increase rapidly at the beginning of the 20th century.
Like CO2, the recent trend in CH4 (shown as + + + in the lower panel) is unprecedented in the
history of CH4 from ice cores. The ice-core data are from Siple Station, Antarctica. Stars and
triangles represent results obtained from melt and dry extraction, respectively. The ellipses indicate
the uncertainties in the concentrations as well as in the mean age of the sample. (Sources: Blake and
Rowland, 1988 ~ Copyright 1988 by the AAAS; Stauffer et al., 1985 - Copyright 1985 by the AAAS.)
11-15
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Policy Options for Stabilizing Global Climate
FIGURE 2-7
CURRENT EMISSIONS OF METHANE BY SOURCE
(Teragrams)
Fossil-Fuel Production
50-95 Tg
Domestic Animal
65-100 Tg
Blomass Burning
50-100 Tg
Rice Production
60-170 Tg
Landfills
30-70 Tg
Natural Sources
115-345 Tg
Rice Production
I.India
2. China
3. Bangladesh
TOP THREE PRODUCERS
Domestic Animals Fossil-Fuel Production
I.India
2. USSR
3. Brazil
1. United States
2. USSR
3. China
Figure 2-7. Human activities in the agricultural sector (animal husbandry, rice production, and
biomass burning) and the energy sector (fossil-fuel production) are the major sources of atmospheric
CH4. Natural sources, from wetlands, oceans, and lakes, may contribute less than 25% of total
emissions. (Sources: Cicerone and Oremland, 1988; Crutzen et al., 1986; Lerner et al., 1988; United
Nations, 1987; IRRI, 1986.)
11-16
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Chapter II: Greenhouse Gas Trends
atmosphere: temperature, soil properties,
fertilizer type, and irrigation practices. These
factors make global extrapolation of CH4
emissions very difficult. Cicerone and
Oremland (1988) estimate a global emission of
60-170 Tg CH4/yr.
Methane is also produced by enteric
fermentation in animals, especially ruminants.
The amount of CH4 produced is dependent on
enteric ecology, the composition and quantity
of feed, and the energy expenditure of the
individual animal. Estimates of emission rates
range from 94 kg CH4/animal/year from West
German dairy cattle, to —35 kg
CH4/animal/year from Indian cattle fed on
kitchen refuse, to 5-8 kg CH4/animal/year from
sheep. Using these emission coefficients and
population statistics of animals in the world,
Crutzen et al. (1986) obtained a global
emission of 78 Tg CH4 for 1983. This
emission includes —5 Tg CH4 from wild
animals and < 1 Tg CH4 from humans. About
75% of the emissions are from cattle and dairy
cows. India, the USSR, Brazil, the U.S., and
China are the five major countries in terms of
CH4 emission from domestic animals (Lerner
et al., 1988).
Other natural sources of CH4 include
termites, and exchange with oceans and lakes.
The source from termites is highly uncertain
and controversial. Estimates of annual global
emissions range from close to zero (Seiler,
Conrad et al., 1984) to 20 Tg (Fraser,
Rasmussen et al., 1986), and as high as 200 Tg
CH4 (Zimmerman et al., 1982, 1984), on the
order of half the global emission. The oceanic
source is small, estimated to be 5-20 Tg
CH4/yr (Cicerone and Oremland, 1988).
There are several anthropogenic sources
of methane. Methane is produced by
incomplete combustion during biomass
burning, mainly in the tropics. The amount of
CH4 produced depends on the material burned
and the degree of combustion. Estimates
range from 50-100 Tg CH^ (see Cicerone
and Oremland, 1988). While a few studies
have attempted to understand and measure
CH4 emission during biomass burning
(Crutzen et al., 1979,1985), extrapolation to a
global estimate is difficult because of the lack
of global data on area burned, fire frequency,
and characteristics of fuels and fires. The
feasibility of monitoring fires from space
(Matson and Holben, 1987; Matson et al.,
1987) will improve this estimate significantly.
Methane is also produced in large
municipal and industrial landfills, where
biodegradable carbon in the refuse
decomposes into CO2 and CH4. As in the
case of many other CH4 sources, the fraction
of gas produced that escapes to the
atmosphere is debated. Recently, Bingemer
and Crutzen (1987) estimated that this source
produces 30-70 Tg CH4/yr. These estimates
assume that a large fraction of all organic
carbon deposited in landfills eventually is
subject to methanogenesis and subsequent
emission to the atmosphere. Cicerone and
Oremland (1988) also adopt a range of 30-70
Tg CH4/yr.
Methane is the major component
(—90%) of natural gas, and so the leakage of
natural gas from pipelines and the venting of
natural gas from oil and gas wells represent
sources of CH4 entering the atmosphere.
Although natural gas production and
consumption statistics are available globally,
the nature of this fugitive CH4 source makes
it difficult to estimate how much this source
contributes to the atmospheric abundance of
CH4. From U.S. and Canadian natural gas
statistics, it is estimated that approximately
2-2.5% of the marketable gas is unaccounted
for. Assuming that all of the unaccounted for
gas is lost to the atmosphere, 25-30 Tg CH4/yr
from line loss is obtained by global
extrapolation (Cicerone and Oremland, 1988).
An additional 15 Tg CH4/yr is released from
natural gas sources, assuming that -20% of
the gas that is vented and flared at oil and gas
wells is not combusted, escaping to the
atmosphere as CH4 (Darmstadter et al., 1987).
Together these estimates suggest a source of
up to 50 Tg CH4/yr from natural gas
production and consumption. Much of the
unaccounted for gas, however, may represent
meter discrepancies, and venting of natural gas
has been declining in recent years
(Darmstadter et al., 1987). On the other hand,
gas distribution systems outside of North
America may have much greater leak rates.
Thus a reasonable range for these sources may
be 20-50 Tg CH^/yr.
Methane is also the major component of
gas trapped in coal. The percentage of the
CH4 component increases with the age and
n-i7
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Policy Options for Stabilizing Global Climate
depth of the coal and is released to the
atmosphere during mining and processing/
crushing of coal. Globally, the amount of CH4
in coal is —0.5% of the mass of coal extracted.
This source is estimated to be 15-45 Tg CH4/yr
in 1980 (Darmstadter et al., 1987; Cicerone
and Oremland, 1988).
A highly uncertain but potentially large
source of CH4 is clathrates: stable methane
hydrates in sediments under permafrost and on
continental margins (Kvenvolden, 1988). The
magnitude of the current CH4 release from
this source is unknown. Climate warming
presents the potential for destabilization of the
hydrates and subsequent release of CH4 to the
atmosphere (see CHAPTER III).
Chemical and Radiative Properties/
Interactions
Methane is active both radiatively and
chemically in the atmosphere. At present
levels, an additional molecule of CH4 will
contribute a radiative forcing that is equivalent
to that contributed by approximately 20
molecules of CO2 (e.g., Ramanathan et al.,
1985; Donner and Ramanathan, 1980; Lacis et
al., 1981). These radiative transfer calculations
suggest that a doubling of atmospheric CH4
(1.6-3.2 ppm) will contribute a radiative
forcing of 0.16°C (Hansen et al., 1988).
The destruction rate of CH4 is
dependent on the amount of OH (and hence
water vapor) in the atmosphere as well as on
temperature. The globally averaged lifetime
(atmospheric abundance divided by destruction
rate) of CH4 is approximately 10 years, the
local lifetime being shorter in the tropics.
Using estimates of the average concentration
of atmospheric hydroxyl radicals derived from
measurements of methyl chloroform, Prinn et
al. (1987) have deduced the average
atmospheric lifetime of CH4 to be 9.6 (+2.2, -
1.5) years. The reaction between CH4 and OH
eventually produces carbon monoxide (CO);
CO itself reacts with OH, producing CO2
(Thompson and Cicerone, 1986). Thus, an
increase in the background levels of either
CH4 or CO can reduce OH and the oxidizing
power of the entire atmosphere. It is
estimated that increases in CO alone from
1960 to 1985 would have lowered OH
concentrations in the atmosphere, increased
the methane lifetime, and resulted in a 15-20%
increase in CH4 concentrations (Khalil and
Rasmussen, 1985; Levine et al., 1985;
Thompson and Cicerone, 1986).
Because of the interactions between CO,
CH4, and OH in the atmosphere, it is difficult
to predict the effects of climate change on OH
destruction of CH4, as increasing atmospheric
water vapor and increased precipitation (and
removal of OH reservoirs like nitric acid
[HNO3] and hydrogen peroxide [H2O2]) have
opposite effects on OH concentrations.
Changes in nitrogen oxides (NOX) and
tropospheric ozone (O3) also strongly affect
atmospheric OH (see below).
NITROUS OXIDE
Concentration History and Geographic
Distribution
Nitrous oxide (N2O) is present in
minute amounts in the atmosphere but it is
nonetheless of great importance. Its
concentration is three orders of magnitude less
than that of CO2, but its radiative forcing per
molecule is about 200 times greater. The first
high-precision measurements of atmospheric
N2O from the late 1970s showed
unambiguously an increasing trend in its
concentration (Weiss, 1981). Continuous
measurements at four Atmospheric Lifetime
Experiment/Global Atmospheric Gases
Experiment (ALE/GAGE) sites have been
made since 1979 (see Figure 2-8). Flask
samples of air from five sites of the
cooperative network of NOAA/GMCC are
also being analyzed for N2O (Thompson et al.,
1985; Komhyr et al., 1991).
The concentration of atmospheric N2O
was 307 ppb in 1988, and its annual growth
rate is -0.7-0.8 ppb per year, or 0.2-0.3% per
year (Prinn et al., 1990; Elkins and Rossen,
1989). The concentrations at the Northern
Hemisphere sites are 0.8-1.0 ppb higher than
those at the Southern Hemisphere sites,
suggesting the dominance of a northern source
(Elkins and Rossen, 1989; Butler et al., 1989;
Elkins et al., 1988).
Ice-core data show that the pre-
industrial concentration of N2O was 285 ±10
ppb averaged between 1600-1800 (Pearman et
al., 1986; Khalil and Rasmussen, 1987).
Unlike CO2, whose concentration began to
11-18
-------
Chapter II: Greenhouse Gas Trends
FIGURE 2-8
(a)
NITROUS OXIDE CONCENTRATION
(Parts per Billion)
Atmospheric Data
3 I 0
N -, O
508 f
a
•C 304 r
a. :
302 [
j
"* •
300 L
1979
19M
19M
(b)
Ice-Core Data
• 30O
•
ISO
' J •—--'*"
-t-TT .
t too
170O
ItOO
Y««r
Figure 2-8. Concentration of atmospheric N2O has been increasing at the rate of 0.2-0.3%/yr in the
last decade (upper panel). The ice-core record (lower panel) shows that N2O was relatively constant
from the 1600s to the beginning of the 20th century and began increasing rapidly in the last 50 years.
(Sources: Khalil and Rasmussen, pers. communication; Pearman et al., 1986 -- Reprinted by
permission from Nature, vol. 320, pp. 248-250. Copyright © 1986 Macmillan Journals Limited.)
11-19
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Policy Options for Stabilizing Global Climate
increase significantly in the 1800s, N2O
remained fairly constant until the 1900s, and
then began increasing more rapidly in the
1940s (Pearman et al., 1986; Khalil and
Rasmussen, 1987). (See the ice-core data in
Figure 2-8.) Measurements of N2O in the
Vostok ice core show lower atmospheric N2O
values of 244 ±20 ppb during the last climatic
transition (about 12,000 BC) with a slight
increase as the climate was warming up
(Zardini et al., 1989).
Sources and Sinks
While a lot of progress has been made
during the last five years in quantifying the
sources and sinks of N2O in the atmosphere,
there remain considerable uncertainties in the
global budget and in the contributions of
individual source terms. The uncertainties
arise not only because of the scarcity of
measurements of N2O fluxes, but also, as in
the case for CH4, because of the complexity of
the biogeochemical interactions and
heterogeneous landscape where N2O is
produced.
Nitrous oxide is simultaneously
produced and consumed in soils via the
metabolic pathways of denitrification,
nitrification, nitrate dissimilation, and nitrate
assimilation. These processes are affected by
various environmental parameters such as
temperature, moisture, the presence of plants,
and the characteristics and composition of the
soils (e.g., Seiler and Conrad, 1987; Sahrawat
and Keeney, 1986). The flux of N2O to the
atmosphere also depends on the location of
the N2O-producing and N2O-consuming
microorganisms and their relative activity
within the soil column (Conrad and Seiler,
1985). Because of the complexity of the N2O
production and destruction processes, and the
inherent heterogeneity of soils, it is difficult to
estimate the contribution of natural soils to
the global N2O budget. Slemr et al. (1984)
calculated N2O emissions from natural
temperate and subtropical soils to be 4.5 Tg
N/yr. Recent measurements (Livingston et
al., 1988; Matson and Vitousek, 1987) show
that N2O emission rates from tropical soils are
higher than those from temperate soils and
that a relationship exists between the N2O flux
and the rate of nutrient cycling in the tropical
forest soils. A source of 3.7 Tg N/yr is
estimated from dry and wet tropical forests
(Matson and Vitousek, 1989). Seiler and
Conrad (1987) give a very tentative estimate of
6 ±3 Tg N/yr from natural soils globally.
Measurements of supersaturation of
N2O in the oceans indicate that the oceans
contribute additional N2O to the atmosphere
(Elkins et al., 1978; Seiler and Conrad, 1981;
Weiss, 1981). Seiler and Conrad (1987)
estimated the oceanic contribution to be 2 ± 1
Tg/year. Recent oceanographic measurements
of N2O suggest that there is large variability,
both temporally and spatially, in the oceanic
flux of N2O to the atmosphere. The flux is
affected by El Nino events and differences in
ocean circulation patterns (Butler et al., 1989;
Elkins, pers. communication). Because the
oceanic reservoir of N2O is between 900 and
1100 Tg N, about one-half and two-thirds the
size of the atmospheric reservoir (Butler,
pers. communication), changes in ocean
circulation as a result of climate change may
have significant impact on the atmospheric
N2O concentrations.
Little is known about N2O emissions
from terrestrial freshwater systems.
Extrapolating from measurements in the
Netherlands and in Israel of elevated N2O
levels in aquifers contaminated by the disposal
of human or animal waste, cultivation, and
fertilization, Ronen et al. (1988) estimated a
global source 0.8-1.7 Tg N/yr from
contaminated aquifers.
Nitrous oxide is also produced during
combustion, but the importance of this source
is unclear at this time. A study of this N2O
source, reported by Hao et al. (1987), found
that the amount of N2O in flue gases was
correlated with the nitrogen content of fuels.
Using statistics on solid- and liquid-fuel
production, they estimated an emission of 3.2
Tg N2O-N in 1982. Very recent studies,
however, suggest that many of the N2O
measurements, including those of Hao et al.
(1987), may have been affected by a sampling
artifact. A reaction between water, sulfur
dioxide (SO^, and NOX generates N2O in
sample cylinders over a period of hours,
sometimes increasing N2O concentrations by
more than an order of magnitude, unless the
samples are carefully dried or N2O is
measured immediately (Muzio and Kramlich,
1988; Muzio et al., 1989; Montgomery et al.,
1989). Reanalysis of measurements made in
11-20
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Chapter II: Greenhouse Gas Trends
the U.S., excluding those that were apparently
affected by this reaction, found no significant
difference between N2O emissions from gas
and coal-fired boilers (Piccot, pen>.
communication). Recent measurements
conducted by the U.S. Environmental
Protection Agency (U.S. EPA) with an on-line
analyzer confirm this finding: in both utility
and small experimental boilers N2O
concentrations in the exhaust gases were
always less than 5 ppm and generally less than
2 ppm (Hall, pers. communication). This
suggests that the relationship between N2O
and fuel-nitrogen found by Hao et al. (1987)
may have actually been due to differences in
SO2 and NOX emissions. Emissions of N2O
do appear to vary with combustion technology.
Preliminary measurements suggest that
fluidized-bed combustors and catalyst-equipped
automobiles may have substantially elevated
N2O emissions (De Soot, pers.
communication). Total N2O emissions from
fossil-fuel combustion cannot be estimated
with any confidence at this time, but may be
less than 1 Tg N/yr (see CHAPTER VI).
The addition of nitrogenous fertilizers
to soils enhances the emission of N2O and
other nitrogen gases to the atmosphere. This
emission depends on temperature, soil
moisture, rainfall, fertilizer type, fertilizer
amount, and the way the fertilizer is applied.
It also depends on the properties of the soils
and the crops grown. The fraction of fertilizer
nitrogen lost to the atmosphere as N2O ranges
from -0.001-0.05% for nitrate, -0.01-0.1% for
ammonium fertilizers, to —0.5->5% for
anhydrous ammonia. With a global
consumption of approximately 70.5 million
tons nitrogen as nitrogenous fertilizers in
1984, an N2O contribution of 0.14-2.4 Tg N#r
is estimated. Although the amount of N2O
emissions associated with the use of
nitrogenous fertilizers is estimated to be small
compared to emissions from natural sources,
such emissions are, nonetheless, a source
subject to rapid growth.
Land-use modification in the tropics
may also contribute N2O to the atmosphere.
N2O is produced during biomass burning, but
because direct estimates of total N2O
emissions are difficult, N2O emissions are
estimated by ratios with emissions of CO, or
other nitrogen gases. Crutzen (1983)
estimated this source to be 1-2 Tg N/yr,
although the accuracy of this estimate is highly
uncertain. It may indeed be an over-estimate
and subject to the same sampling artifact as
that encountered in fossil-fuel combustion. A
reanalysis by Crutzen et al. (1989) yielded very
low estimates: 0.06-0.3 Tg N/yr from biomass
burning.
Recently, Bowden and Bormann (1986)
found enhanced N2O fluxes to the atmosphere
from cleared areas in a temperate forest and
elevated N2O concentrations in ground water
adjacent to the cut watershed. Similarly,
threefold increases in N2O fluxes were found
in pastures and forest clearings in the Amazon
(Luizao et al., 1989). Extrapolating the
Amazonian results to all deforested areas in
the globe, a source of 0.8-1.3 Tg N/yr is
estimated. In contrast, Robertson and Tiedje
(1988) postulate, on the basis of observations
in Central America, that the loss of primary
tropical rain forest may decrease the emissions
of N2O to the atmosphere if vegetation did
not return. These studies suggest that rapid
deforestation in the tropics may significantly
alter the N2O budget, although an estimate of
its contribution to the global budget has not
been attempted.
Chemical and Radiative Properties/
Interactions
Relative to CO2, N2O has a low
concentration in the atmosphere, and its rate
of increase is much smaller than that of the
other trace gases. Yet it still plays an
important role in the radiative and chemical
budgets of the atmosphere. The seemingly
small growth rate, ~0.25%/year, reflects a
large imbalance (—30%) between the sources
and sinks. The extremely long lifetime of
N2O, —160 years, means that the system has a
very long memory of its emission history.
Nitrous oxide is an effective greenhouse
gas. The radiative forcing of one molecule of
N2O is equivalent to that of about 200
molecules of CO2; an increase of 50% in N2O
and a doubling of CH4 would yield
approximately the same radiative forcing, even
though the N2O concentration is less, by a
factor of 5, than that of CH4. A 50% increase
in the current burden of N2O in the
atmosphere will yield a radiative forcing of
about 0.15°C (without any feedbacks).
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Policy Options for Stabilizing Global Climate
Nitrous oxide is not chemically reactive
in the troposphere and is destroyed in the
stratosphere by photolysis and by reaction with
atomic oxygen in the excited state (O(1D)].
The latter reaction makes N2O the dominant
precursor of odd nitrogen in the stratosphere.
Thus, the observed increase in N2O should
lead to increases in stratospheric NOX, which
would significantly alter stratospheric ozone
chemistry.
CHLOROFLUOROCARBONS
Concentration History and Geographic
Distribution
High-precisionmeasurementsofCFC-11
(CC13F) and CFC-12 (CC12F2) began in 1970
with the development of gas chromatograph
techniques using electron capture detectors
(Lovelock, 1971). Like CO2 and CH4, surface
measurements have consisted of
high-frequency observations at a few dedicated
sites as well as flask samples of air collected
from a global network of stations or from
irregular global transects.
High-frequency in situ measurements of
surface concentrations have been or are
currently being made at the five coastal/island
ALE/GAGE stations (Cunnold et al., 1986;
Prinn et al., 1983; Rasmussen and Khalil,
1986; Simmonds et al., 1987). In addition,
analysis of CFC concentrations in the flask
samples of air collected at the NOAA/GMCC
globally distributed network of sites have
begun at the GMCC facility in Boulder
(Thompson et al., 1985; NOAA, 1987).
CFC-12 is the most abundant
chlorofluorocarbon in the atmosphere. Its
average tropospheric concentration in 1986
was 392 parts per trillion by volume (ppt),
corresponding to a total burden of about 8.1
Tg. Its concentration rose rapidly in the 1970s
and is currently increasing at about 4%/yr.
With a total burden of about 5.2 Tg,
CFC-11 is the second most abundant
chlorofluorocarbon in the atmosphere. Its
average concentration in 1986 was 226 ppt,
and is also increasing currently at 4%/yr.
Other important sources of atmospheric
chlorine include methyl chloride (CH3C1, the
major natural source of stratospheric chlorine)
at a concentration of 600 ppt (no measured
trend); methyl chloroform (CH3CC13) at 125
ppt in 1986, increasing at ~5%/yr; carbon
tetrachloride (CC14), at about 100 ppt,
increasing at 1%/yr; HCFC-22 (formerly
denoted CFC-22; CHC1F2), at ~80 ppt in
1986, increasing at 7%/yr, and CFC-113
(C^Cl^) at 30-70 ppt in 1986, increasing at
greater than 10%/yr (Prinn, 1988).
Bromocarbons that are moderately long-
lived in the troposphere supply bromine to the
stratosphere where it plays an important role
in ozone destruction, especially with high
levels of active chlorine such as are associated
with the Antarctic ozone hole. Methyl
bromide (CH3Br, 15 ppt in 1985) is natural,
with some industrial sources, and is the major
source of stratospheric bromine. The halons
1211 (CBrClF2) and 1301 (CBrF3) currently
are small sources (—2 ppt each) but are
growing rapidly (> 10%/yr).
Sources and Sinks
CFCs are solely a product of the
chemical industry. CFC-11 is used in blowing
plastic foams and in aerosol cans. CFC-12 is
used primarily in refrigeration and aerosol
cans. Comprehensive data on production of
CFC-11 and CFC-12 are published by the
Fluorocarbon Program Panel (FPP) of the
Chemical Manufacturers Association (CMA).
The peak year for CFC-11 and -12 production
by reporting companies was 1974, in which a
total of 812.5 gigagrams (Gg) of CFC-11 plus
CFC-12 was produced.4 Annual CFC
production decreased somewhat following a
ban on "non-essential" aerosol uses in the
United States, Canada, and Sweden. Non-
aerosol uses have continued to increase, as has
CFC-113, and the total has risen rapidly in
recent years, with estimated global production
of CFCs -11, -12, and -113 in 1985 at about
950 Gg. Of this total about 70% was
consumed by the U.S., the European
Economic Community, and Japan (see Figure
4-9 in CHAPTER IV).
The CMA data do not cover the USSR.
The FPP has estimated Soviet production;
however, these estimates are considered
unreliable. Data for China and the countries
of Eastern Europe are lacking entirely,
rendering modest uncertainties (~15%) in the
magnitude of world emissions for CFC-12 and
11-22
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Chapter II: Greenhouse Gas Trends
smaller uncertainties for those of CFC-11.
Cunnold et al. (1986) and Fraser et al. (1983)
have found that the measured trend of CFC-11
and CFC-12 concentrations is relatively
consistent with the CMA estimates of CFC-11
release but not CFC-12 release, which suggests
that the USSR and Eastern Europe contribute
a substantial amount to CFC-12 emissions.
Methyl chloroform (CH3CC13) is widely
used in the manufacturing industry as a solvent
for degreasing, CFC-113 is used in the
electronics industry, mainly for circuit board
cleaning, and HCFC-22 is used mainly in
refrigeration. The sources of these gases have
been estimated in various studies, but a survey
of sources for CFC-113 and HCFC-22 -
equivalent to that conducted for CFC-11 and
CFC-12 - has not been done. A survey of
methyl chloroform has been published recently
(Midgley, 1989).
Fully halogenated CFCs (those that
contain no hydrogen) are destroyed almost
solely by photolysis in the stratosphere. The
atmospheric lifetimes of CFCs estimated from
the ALE/GAGE analyses are llltS2 years for
CFC-12, 74 T$ years for CFC-11, and
approximately 40 years for carbon
tetrachloride. Compounds containing
hydrogen (HCFCs) react with OH in the
troposphere, have lifetimes on the order of 20
years or less, and pose less threat to the ozone
layer because their concentrations do not build
up to as large values as would equivalent
CFCs. The ALE/GAGE lifetime for CH3CC13
is 6.3tJ;» years (Prinn et al., 1990), and the
corresponding lifetime for HCFC-22 is 15
years. All of these species can contribute to
the stratospheric burden of chlorine, but the
longer-lived CFCs can accumulate, reaching
higher concentrations before a steady state
balance is achieved.
Chemical and Radiative Properties/
Interactions
CFCs absorb infrared radiation in the
window region of the atmospheric spectrum
(see Figure 2-5). Although CFCs are present
in minute amounts (ppt) in the atmosphere,
together they are one of the dominant
greenhouse gases. At present they have the
highest annual fractional increase of all the
greenhouse gases (~4-10%/yr). Furthermore,
the radiative forcing due to each additional
molecule of CFC is equivalent to that due to
about 15,000 molecules of CO2, and at present
levels, this radiative forcing would increase
linearly with added CFC molecules
(Ramanathan et al., 1987). A 2 ppb increase
in both CFC-11 and CFC-12 would contribute
a radiative forcing of 0.3°C, equivalent to that
from a 65 ppm increase in CO2. In the 1980s,
CFC-11 and CFC-12 together contributed
about 15% of the increase in global
greenhouse forcing.
The dissociation products of
halocarbons are the dominant sources of
chlorine and bromine for the stratosphere
(WMO, 1985). These elements are major
components in the catalytic cycles that control
ozone abundance. Trends for the major
halocarbon reservoirs in the stratosphere (HC1
and HF) have been observed from the ground
and in latitudinal surveys with aircraft. Within
the limits of observational uncertainties, the
estimated trends in these species are consistent
with trends in the source gases themselves.
OZONE
Concentration History and Geographic
Distribution
Ozone is both produced and destroyed
in situ in the atmosphere. While the other
trace gases are relatively well-mixed vertically,
the non-uniform vertical distribution of O3 in
the atmosphere is of prime importance in
determining its radiative and chemical effects
(see Figure 2-9). We often focus separately on
stratospheric and tropospheric ozone.
Stratospheric O3 represents the majority of the
total and controls the absorption of solar
ultraviolet radiation. Tropospheric O3 plays
an important role in air quality and could
contribute to major greenhouse forcing.
Tropospheric Ozone
Ozone sondes from a diverse and
globally distributed network provide our only
record of possible trends in tropospheric O3.
A review of ozone sonde and surface data have
been given by Logan (1985), Tiao et al. (1986),
and more recently by Crutzen (1988). Since
the 1970s, surface O3 concentrations are
measured routinely at the four continuous
monitoring stations operated by NOAA/
GMCC: Pt. Barrow, Alaska; Mauna Lao,
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Policy Options for Stabilizing Global Climate
FIGURE 2-9
OZONE CONCENTRATION (cm
10'° 10" 10"
140
120 -
TEMPERATURE PROFILE
AND OZONE
DISTRIBUTION IN
THE ATMOSPHERE
to
so
30
20
10
RADIATIVE FORCIHG
rrariciL SIMITHITT
-0.01
-0.00 0.01
DEC/DU OZONE CHANCE
0.02 !
100
200
300
400
500
TEMFtHATUMe IK)
Figure 2-9. On the left, temperature profile and ozone distribution in the atmosphere. On the right,
sensitivity of global surface temperature to changes in vertical ozone distribution. Ozone increases
in Region I (below ~30 km) and ozone decreases in Region II (above —30 km) warm the surface
temperature. The results are from a 1-D radiative transfer model in which 10 Dobson unit ozone
increments are added to each layer. The heavy solid line is a least square fit to step-wise calculations.
(Sources: Watson et aL, 1986; Lacis et aL, 1990 -- Copyright 1990 by the American Geophysical
Union.)
11-24
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Chapter II: Greenhouse Gas Trends
Hawaii; American Samoa; and the South
Pole (see e.g., NOAA, 1987). NOAA/GMCC
also participates in international cooperative
ozone sonde profiling activities. Because of
the reactivity of O3 near the surface and its
short lifetime in the planetary boundary layer,
surface measurements are not representative of
the average troposphere.
The O3 data taken near populated and
industrial regions in the 1930s to the 1950s
generally show an annually averaged
concentration of 10-20 ppb at the surface, with
a seasonal cycle that peaked in summer. The
data show a generally increasing trend,
especially in the summer, in surface
concentrations of O3 at sites in western
Europe, the U.S., and northern Japan. For
example, a factor of 2 increase, from ~30 ppb
in 1933 to ~60 ppb in the 1980s, is found in
the summer concentrations in south Germany
and Switzerland. Similarly, summertime
concentrations of O3 at the surface in rural
areas in the eastern U.S. have increased by
20-100% since the 1940s (Logan, 1985). The
surface O3 trend is 1%/yr or more at those
sites in close proximity to population and
industrial centers. At Pt. Barrow and at
Mauna Loa, geographically removed from but
still under the influence of urban centers,
surface O3 was about 25 ppb in 1986 with
summer values of 35-40 ppb. A small positive
trend (0.7 ±0.5%/yr) is detected at these two
sites from 1973-1986.
Analysis of the ozone sonde data at
these populated sites shows a small but
significant positive trend in mid-tropospheric
ozone. In general, the mid-tropospheric trends
are smaller than those at the surface of the
same O3 profile, and trends in the upper
troposphere and lower stratosphere are
negative, —0.5%/yr.
At remote locations, surface O3 exhibits
a behavior very different from that near
populated and industrial regions. At remote
sites in the Canadian Arctic and in Tasmania,
Australia, for example, the seasonal cycle of
surface O3 has a minimum, rather than a
maximum, in summer or autumn. Surface O3
at the South Pole was 20 ppb in 1986, similar
to that measured in Western Europe in the
1930s. Also, unlike populated sites in the
Northern Hemisphere, O3 at remote sites in
the Northern Hemisphere exhibits no
significant trends near the surface, but
significant positive trends at 700 millibars
(mb) and 500 mb. Mid-tropospheric O3 at
Resolute, Canada (75°N), for example, is
found to be increasing at 1%/yr, while there is
a negative trend in the lower stratosphere. In
the Southern Hemisphere, however, there
appear to be no significant trends in surface or
mid-tropospheric O3, although O3 in the lower
stratosphere has clearly decreased and the
seasonal cycle at the South Pole has doubled
in amplitude.
Stratospheric Ozone
The recent record of O3 concentrations
in the upper atmosphere has been reviewed by
a NASA panel of experts (International Ozone
Trends Panel, see Executive Summary in
Watson et al., 1988). They report a
statistically significant decrease in the total
column abundance of O3 above the known
natural variations using ground-based Dobson
instruments from 1969 to 1986 at mid and
high northern latitudes during winter.
Satellite data, calibrated by coincident Dobson
measurements, show a decrease of about 2-3%
from October 1978 (solar maximum) to
October 1985 (solar minimum) in the column
O3 concentrations between 53°S and 53°N.
The cause of this decrease over such a short
record has not been identified but may be due
to increases in chlorine, the decline in solar
activity, or the global impact of the Antarctic
ozone hole. The observations of stratospheric
O3 in the Northern Hemisphere indicate that
O3 abundances have declined over the past 20
years. The small decreases (1-2%), if any, in
the summer months are consistent with the
predicted change due to increasing CFCs.
However, the measured ozone loss poleward of
40°N in winter is greater (by a factor of 2-3)
than that predicted by theory (Watson et al.,
1988; Rowland, 1989). This unexplained
depletion of O3 in the north is not of the
same magnitude as the Antarctic ozone hole
but may be associated with the unusual
chemistry occurring over Antarctica, marking
the start of a greater global decline.
Sources and Sinks
Ozone is not emitted directly by human
activity, but its concentration in the
troposphere is strongly governed by
anthropogenic emissions of NOX and
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Policy Options for Stabilizing Global Climate
hydrocarbons, and in the stratosphere by CFCs
among others. Because of the short lifetimes
of NOX and many of the other chemical
species important in tropospheric O3
chemistry, O3 concentrations exhibit large
variability horizontally, vertically, and
temporally. Ozone's annual concentration,
seasonal cycle, and trend have different
behaviors in different parts of the globe so
that the observations from a few regions
cannot be viewed as globally representative.
Global trends in tropospheric O3 cannot be
unambiguously extracted from trends in
column O3 either. Stratospheric O3 dominates
the column abundance (90% of the total) and
its decreasing trend may obscure positive or
negative trends in tropospheric ozone. The
difficulty in determining the globally
representative trend in tropospheric O3
translates into uncertainties in the O3
contributions to the greenhouse warming.
Chemical and Radiative Properties/
Interactions
Radiative forcing of O3 is more complex
than that of the other greenhouse gases
because (1) O3 is the major source of
atmospheric heating due to ultraviolet and
visible absorption bands, in addition to being
a greenhouse gas and (2) O3 trends are not
uniform in the atmosphere -- anthropogenic
effects are expected to include upper
stratospheric losses, lower tropospheric
increases, and latitudinally dependent changes.
Radiative transfer calculations reveal
that the ozone's climate forcing changes sign
at about 25-30 km altitude (see Figure 2-9).
Ozone increases below this level lead to
surface warming because its greenhouse effect
dominates its impact on solar radiation, while
O3 added to the stratosphere above —30 km
increases stratospheric absorption of solar
energy at the expense of solar energy that
would otherwise have been absorbed at lower
altitudes. On a per molecule basis, potential
O3 changes with the largest net effect on
surface temperatures are those occurring near
the tropopause where the temperature contrast
between absorbed and emitted thermal
radiation is greatest. Ozone changes near the
surface produce little greenhouse forcing since
the thermal radiation from the surface
absorbed by ozone is nearly the same
temperature as that which is re-emitted.
While the radiative effects of O3 are
understood theoretically, quantifying surface
temperature changes due to O3 perturbations
is difficult because of the large natural
variability in tropospheric ozone and the lack
of global coverage in the observations.
Available ozone trend data are limited to
northern mid latitudes. Some of the reported
data showed decreases in O3 in the upper
troposphere and lower stratosphere. Using
these data, Lacis et al. (1990) find that during
the 1970s surface cooling resulted from these
changes and was equal in magnitude to about
half of the warming contributed by CO2
increases during the same time period. These
results differ from previous assessments (e.g.,
Ramanathan et al., 1985; Wang et al., 1988)
that were based on one-dimensional
photochemical model results which predict
ozone increases in the lower stratosphere and
upper troposphere, and thus produce surface
warming. Predictions of two-dimensional
photochemical models for increases in CFCs
suggest that ozone should decrease in the
lower stratosphere at middle and high
latitudes, but increase in the tropics (Ko et al.,
1984; WMO, 1985). This implies a strongly
latitude-dependent climate forcing for O3
distributional changes with surface cooling in
the middle and high latitudes and warming in
the tropics. However, these two-dimensional
models did not include the chlorine-catalyzed
loss associated with heterogeneous chemistry
that leads to substantial ozone loss in the
lower stratosphere (the Antarctic ozone hole).
The global nature of O3 changes in the
upper troposphere and lower stratosphere
cannot be deduced, at this point, from current
observations. This makes highly uncertain the
evaluation of O3 contributions to the global
greenhouse warming.
OTHER FACTORS AFFECTING
COMPOSITION
In addition to those greenhouse gases
cited above that have a direct impact on the
radiative balance of the Earth, we must
consider those forces that control the chemical
balance of the atmosphere, in turn controlling
the abundance of greenhouse gases. With the
exception of ozone, the greenhouse gases are
generally not very reactive in the atmosphere;
they have long chemical lifetimes, on the order
of 10 to 200 years; and they accumulate in the
11-26
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Chapter II: Greenhouse Gas Trends
atmosphere until their rate of chemical
destruction balances their emissions. The
chemistry of the stratosphere and troposphere
provides the oxidizing power to destroy the
majority of trace pollutants in the Earth's
atmosphere (a major exception is CO2, see
above). We outline below those primary and
secondary components of the Earth's
atmosphere that affect the chemically reactive
gases and note changes that may have occurred
in the recent past and those possible in the
future.
Global Tropospheric Chemistry
The Hydroxyl Radical
In the troposphere, many species are
removed in a chain of reactions beginning with
the hydroxyl radical (OH) and ending with the
deposition or rainout of a soluble compound,
or with the complete oxidation of the original
compound (i.e., net: CH4 + 2O2 -» CO2 +
2H2O). For CH4, most hydrocarbons, and
halocarbons containing a hydrogen atom (e.g.,
anthropogenic HCFCs such as CHCIF^, the
chemical lifetime will vary inversely with the
suitable average of the global OH
concentration.
The OH radicals in the troposphere are
short-lived (<1 second) and are produced by
sunlight in the presence of O3 and H2O; they
are consumed rapidly by reaction with CO,
CH4, and other hydrocarbons. Moderate
levels of nitrogen oxides (NOX: NO and NO^
can play an important role in recycling the
odd-hydrogen (HOX) from HO2 to OH, thus
building up the concentrations of OH; high
levels of NOX, however, can reduce both OH
and O3. The short lifetime of OH means that,
when we integrate the loss of even a well-
mixed gas like CH4 against consumption by
reaction with OH, we are integrating over the
myriad of conditions of the troposphere in
terms of sunlight, O3, H2O, CO, CH4, NOr
and others. These tropospheric conditions
vary over scales that range from smooth in
latitude and height to irregular in plumes
downwind from metropolitan areas. At
present we are just developing models for OH
that can describe these varied conditions and
accurately integrate the global loss of a
greenhouse gas such as CH4; shorter-lived
gases pose a greater problem.
In spite of these problems modeling the
chemically complex, heterogenous conditions
of the global troposphere, we do understand
tropospheric chemistry sufficiently to make
some simple generalizations:
• Most loss of CH4 occurs in the tropics,
particularly in marine environments remote
from the influence of urban areas and the
continental boundary layer,
• Increasing concentrations of CO and
CH4 will reduce levels of OH,
• Large scale perturbations to
tropospheric O3 and H2O (from climate
change) may have equally significant impacts
on OH concentrations,
• Changes in anthropogenic emissions of
NOX are expected to lead to significant
increases in northern hemispheric O3 and lead
to moderate increases in globally integrated
OH.
Carbon Monoxide
Carbon monoxide has a photochemical
lifetime of about one month in the tropics;
that lifetime becomes indefinitely long (and is
controlled by transport) in the winter at high
latitudes. The globally averaged destruction of
CO corresponds to an estimated lifetime of 2.5
months. Carbon monoxide is lost almost
exclusively through tropospheric reactions with
OH (and in this non-linear system, CO is also
a major sink for OH). There are some
estimates of plant/soil uptake of CO, but these
are not of major significance.
Detailed observations of CO
concentrations are available over the past
decade (Dianov-Klokov and Yurganov, 1981;
Khalil and Rasmussen, 1988) and there are
sporadic measurements since 1950 (Rinsland
and Levine, 1985). These data indicate that
CO concentrations have grown modestly, but
consistently (1-6%/yr), in the northern
mid-latitudes over the last few decades. There
is no convincing evidence for growth in the
Southern Hemisphere (Seiler, Giehl et al.,
1984; Cicerone, 1988). This pattern is
consistent with a growing anthropogenic
source, since the short lifetime precludes
significant interhemispheric transport. Since
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Policy Options for Stabilizing Global Climate
CH4 concentrations have also increased
similarly (about 1%, as noted above), we
would expect a similar change of opposite sign
in tropospheric OH.
Nitrogen Oxides
One form of odd-nitrogen, denoted as
NOX, is defined as the sum of two species, NO
+ NO2. NOX is created in lightning, in
natural fires, in fossil-fuel combustion, and in
the stratosphere from N2O. The NOX levels
over the continental boundary layer and in the
aircraft flight lanes of the Northern
Hemisphere are likely to have increased over
the last several decades. Nevertheless, the
levels of NOX in the clean marine environment
are so low that they might be accounted for
entirely by natural sources (i.e., lightning, fires,
stratospheric HNO3).
The anticipated changes in NOX levels
over limited regions of the Northern
Hemisphere are expected to have only a small
direct effect on the globally integrated OH
concentration. A more important impact of
NOX emissions is likely for tropospheric O3,
where a substantial fraction of the global
tropospheric ozone production is predicted to
take place in small regions with elevated levels
of NOX and hydrocarbons (Liu et al., 1987).
These issues are unresolved and are currently
the focus of photochemical studies with
multi-dimensional tracer models.
Stratospheric Ozone and Circulation
Some species such as N2O and CFCs do
not react with OH, and these gases are
destroyed only in the stratosphere by
short-wavelength ultraviolet light and by
reactions with the energetic state of atomic
oxygen, O(1D). For CFCs and N2O the
abundances will be perturbed by changes in
the rate of stratosphere-troposphere
circulation and changes in the stratospheric O3
that shields the solar ultraviolet radiation.
Major perturbations to stratospheric O3 and
circulation may also alter the concentrations of
tropospheric O3, since the stratosphere
represents a significant source for this gas.
Predictions have been made over the
past decade that stratospheric O3 will change
due to increasing levels of CFCs, and that the
circulation of the stratosphere may be altered
in response to changes in climate induced by
greenhouse gases. Recent detection of the
Antarctic ozone hole has dramatized the
ability of the atmosphere to change rapidly in
response to perturbations. There are currently
underway many theoretical studies of the
impact of the ozone hole on stratospheric
circulation, O3 fluxes, and the mean chemistry
of the stratosphere (e.g., N2O losses). As
discussed above, there are also indications of
a declining trend in Northern Hemisphere O3
that may be associated with "Antarctic"
chemistry. In summary, if stratospheric O3
changes in the next few decades are large, they
may lead to alterations in the lifetimes of the
long-lived greenhouse gases and also perturb
tropospheric chemistry through the supply of
O3 and through the increase in solar
ultraviolet light available to generate OH.
CONCLUSION
Anthropogenic emissions of both long-
lived greenhouse gases and short-lived highly
reactive species are altering the composition of
the atmosphere. The concentrations of CO2
and CH4 have increased dramatically since the
pre-industrial era, and CFCs have been
introduced into the atmosphere for the first
time. As a result of the rapid pace of human-
induced change, neither atmospheric
composition nor climate is currently in
equilibrium. Thus, significant global change
can be anticipated over the coming decades,
no matter what course is taken in the future.
The rate and magnitude of change, however,
are subject to human control, which serves as
the motivation for this report.
11-28
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Chapter II: Greenhouse Gas Trends
TABLE 2-1
Trace Gas Data
CO2 CARBON DIOXIDE 1012 kg C
Atmospheric Burden 720
351 ppm in 1988
Not photochemically active
Annual Trend 3.0
1.1 ±0.2 ppm/yr (0.4%/yr) since 1984
Annual Anthropogenic Sources 6-8
1. Fossil-fuel combustion S.5
4.5%/yr since 1984
2. Land-use Modification 0.4 - 2.6
3. Biosphere ~ climate feedback ?
Enhanced aerobic decomposition
of detrital material due to
more favorable climate
Annual Anthropogenic Sinks 3-5
1. Ocean <2
Ocean's capacity to absorb CO2
will be altered by changes in
temperature, salinity, and
biological activity of ocean.
2. Biosphere 0.5-4
Enhanced photosynthetic uptake of
CO2 due to more favorable climate
and/or due to CO2 fertilization
n-29
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Policy Options for Stabilizing Global Climate
TABLE 2-1 (Continued)
CH4
METHANE
109 kg CH4
Atmospheric Burden
1670 ppb in 1988 (global average)
Lifetime: 8 - 12 years
Annual Trend
14 - 16 ppb/yr (0.8-1%/yr)
Annual Sources
1. Fossil fuel
Coal mining
Natural gas drilling, venting,
processing, and transmission loss
2. Biomass burning
3. Natural wetlands
4. Rice Paddies
5. Animals — mainly ruminants
6. Termites
Population unknown
7. Oceans and freshwater lakes
8. Landfills
9. Methane hydrate destabilization
Annual Sinks
1. OH destruction
2. Dry soils
absorption by methane -
oxidizing bacteria in dry soils
4600-4800
40-46
500 ±100
15-45
25-50
50- 100
80-200
60- 170
65- 100
10- 100
5-45
20-70
0 -100 (future)
495 ±145
495 ±145
5-60
H-30
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Chapter II: Greenhouse Gas Trends
TABLE 2-1 (Continued)
N2O NITROUS OXIDE 109 kg N
Atmospheric Burden 1500
307 ppb in 1988
Lifetime: 120 - 160 years
Annual Trend 3.5 ±0.5
0.7 - 0.8 ppb/yr
0.2-0.3%/yr
Annual Sources 14 ±3 (inferred)
1. Combustion of coal and oil < 1
2. Land-use modification
Biomass burning <0.3
Forest clearings 0.8 - 1.3
3. Fertilized agricultural lands 0.2 - 2.4
4. Contaminated aquifers 0.8 - 1.7
5. Tropical and subtropical forests and woodlands 6 ±3
6. Boreal and temperate forests 0.1 - 0.5
7. Grasslands <0.1
8. Oceans 2 ±1
Annual Sinks 10.5 ±3
Stratospheric photolysis and reaction with O(1D)
n-31
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Policy Options for Stabilizing Global Climate
TABLE 2-1 (Continued)
CO CARBON MONOXIDE 109 kg CO
Atmospheric Burden 525
~ 110 ppb
(150 - 200 ppb Northern Hemisphere, 75 ppb Southern Hemisphere)
Lifetime: 0.2 year
Annual Trend 4
1 - 6%/yr Northern Hemisphere
0 - 1%/yr Southern Hemisphere
Annual Sources 3300 ±1700
1. Technological sources 640 ±200
2. Biomass burning 1000 ±600
3. CH4 oxidation 600 ±300
4. Oxidation of natural hydrocarbons (isoprenes and terpenes) 900 ±500
5. Emission by plants 75 ±25
6. Production by soils 17 ±15
7. Ocean 100 ±90
Annual Sinks 2500 ±750
1. Soil uptake 390 ±140
2. Photochemistry 2000 ±600
3. Flux into stratosphere 110 ±30
11-32
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Chapter II: Greenhouse Gas Trends
TABLE 2-1 (Continued)
NOX NITROGEN OXIDES 109 kg N
NOX = NO + NO2
nitric nitrogen
oxide dioxide
NO = NOX + HNO2 -I- HNO3 4- HO2NO2 + NO3 + 2N2O5 + PAN + Paniculate Nitrate
Atmospheric Burden -- large variability; lifetime 1-2 days in summer ?
Marine air 4 ppt (NO)
Continental air
non-urban sites 2-12 ppb
U.S. & European cities 70 - 150 ppb
(100 ppt = 240 x 109kgN)
Annual Trend ?
Annual Sources - Spatially and temporally concentrated sources 25 - 99
1. Combustion of coal, oil and gas 14 - 28
2. Biomass burning 4 - 24
3. Lightning 2 - 20
4. Oxidation of ammonia 1-10
5. Emission from soils (mostly NO) 4 - 16
6. Input from stratosphere (by reaction of O(JD) with N2O) — 0.5
Sinks 24 - 64
1. Wet deposition (precipitation scavenging)
ocean 4 -12
continents 8 - 30
2. Dry deposition 12-22
11-33
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Policy Options for Stabilizing Global Climate
TABLE 2-1 (Continued)
Chemical Name
Formula
CCIjF CFC-11
CCljF, CFC-12
CHC1F, HCFC-22
CCI2FCCIF2 CFC-113
CH,CC13 Methyl
chloroform
CC14 Carbon
tetra-
chloride
CHjCl Methyl
chloride
CBrCIF2 Halon 1211
(BCF)
Concentration
(Ppt)
226 ( 1986)
392(1986)
-80(1985)
30-70 (1986)
(calibration
uncertain)
125 (1986)
75-100 (1986)
(calibration
uncertain)
-600(1986)
-2(1986)
(calibration
uncertain)
Annual Global Prod.
Trend (10* kg)
+4% 350 (1986)
(CMA rep. co.'s
only)
+4% 480 (1986)
(CMA reporting
co.'s plus USSR
estimate)
~+7% 206 (1984)
(1986) 163 (1981)
102 (1977)
+ 11% 138-141 (1984)
91 (1979)
79 (1978)
70 (1977)
~5% ~580 (1985)
(1986)
+ 1% -1000 (1985)
atmospheric
emissions
80-110
? (2000-5000 total,
based on OH);
500 industrial
>10% 5-10 (est. from obs.
(1985) of atm. increase)
Sources
Rigid and flexible foam;
Aerosol propellant
Refrigerant;
Rigid and flexible foam;
Aerosol propellant
Refrigerant; Production of
teflon polymers
(fluoropolymers)
Electronics solvent
Industrial degreasing of
metallic or metaplastic
pieces; Cold cleaning;
Solvent of adhesives,
varnishes, and paints
Chemical intermediate in
CFC-11, -12 production;
Declining use as:
Solvent in chemical &
pharmaceutical processes
and as grain fumigant
Burning Vegetation;
Release from oceans
High-tech fire
extinguisher (portable)
Sinks
Removal in
stratosphere
Removal in
stratosphere
Removal by
OH in
troposphere
Removal in
stratosphere
Removal by
OH in
troposphere
Stratospheric
photolysis
Removal by
OH in
troposphere
Photolysis in
stratosphere
and upper
troposphere
Lifetime
(years)
74*31
-17
(60)
111*222
-44
(120)
15
90
6±1
~40
-1.5
25
11-34
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Chapter II: Greenhouse Gas Trends
TABLE 2-1 (Continued)
Chemical Name
Formula
CBrF_, Halon 1301
(CFjBr)
CCIF3 CFC-13
CCIF,CC1F, CFC-114
C2C1F5 CFC-115
C2F6 CFC-116
CH3Br Methyl
bromide
CHBr3 Bromoform
C^t-j Ethylene
dibromide
(EDB)
CHJI Methyl
iodide
Concentration Annual Global Prod.
(ppt) Trend (10* kg)
-2(1986) >10% 7-8(1984)
(calibration
uncertain)
-3.4(1980) ~5%
(avg. of
5 sites)
5 (1985) ? 13-14 (1985)
Constant at 13
from 1979-84
4 (1985) ? ?
-4(1980) — ?
15 (1985) small ?
-2(1984) ? ?
highly variable
-1(1984) ? ?
~1(1981) — ?
Sources
High-tech fire extinguisher
(built-in systems)
?
Aerosol propellant;
Refrigerant; Production
of CFC-115
?
?
Leaded motor fuel;
Fumigation 50% natural
(anthropogenic sources
probably declining)
Mainly natural (oceans)
Evaporation of leaded
gasoline; Fumigation;
Anthropogenic sources
probably declining
Sinks
Photolysis in
stratosphere
Removal in
stratosphere
Removal in
stratosphere
Removal in
stratosphere
Removal in
mesosphere
and above
Removal by
OH in
troposphere
Removal by
OH in
troposphere,
photolysis
Removal by
OH in
troposphere
Removal by
OH in
troposphere
Lifetime
(years)
110
400
200
400
>500
~1.5
(2.3)
Short-lived
~1
Very
short-lived
Sources: Adapted from Seiler and Conrad, 1987; WMO, 1990.
n-as
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Policy Options for Stabilizing Global Climate
ADDENDUM TO CHAPTER II: RADIATIVE
FORCING DIFFERENCES AMONG THE
GREENHOUSE GASES
Throughout this Report the relative
contributions of greenhouse gases to climate
change are measured based on changes in
atmospheric concentrations of each gas; these
concentration changes alter the radiative
balance of the climate system. The radiative
forcing implied by a change in the atmospheric
concentration of a gas depends on several
factors, including the absorptive strength of
the gas within the infrared spectrum, its decay
profile, and the relative concentrations of all
gases in the atmosphere, among other factors.
The scientific community has typically
measured contributions to radiative forcing
using estimated changes in atmospheric
concentrations. For example, based on the
work by Hansen et al. (1988), the relative
contributions by greenhouse gas to radiative
forcing during the 1980s are summarized in
Figure 2-10a.
The relative contributions in Figure 2-
lOa are based on changes in atmospheric
composition over the period. These changes
are of primary scientific concern since they
affect the radiative balance of the atmosphere
and hence, the rate and magnitude of climate
change. When discussing greenhouse gases in
a policy context, however, it is useful to have
some means of estimating the relative effects
of emissions of each greenhouse gas on
radiative forcing of the atmosphere over some
future time horizon, without performing the
complex and time-consuming task of
calculating and integrating changes in
atmospheric composition over the period. In
short, the need is for an index that translates
the level of emissions of various gases into a
common metric in order to compare the
climate forcing effects without directly
calculating the changes in atmospheric
concentrations.
A number of approaches, called Global
Warming Potential (GWP) indices, have been
developed over the past year. These indices
account for direct effects due to growing
concentrations of carbon dioxide (CO2),
methane (CH4), chlorofluorocarbons (CFCs),
and nitrous oxide (N2O). They also estimate
indirect effects on radiative forcing due to
emissions which are not themselves
greenhouse gases, but lead to chemical
reactions that create or alter greenhouse gases.
These emissions include carbon monoxide
(CO), nitrogen oxides (NOX), and volatile
organic compounds (VOC), all of which
contribute to formation of tropospheric ozone,
which is a greenhouse gas.
In this study we follow the methodology
used by the Intergovernmental Panel on
Climate Change (IPCC, 1990). However, there
is no universally accepted methodology for
combining all the relevant factors into a single
global warming potential for greenhouse gas
emissions. In addition to the IPCC, there are
several other noteworthy attempts to define a
concept of global warming potential, including
Lashof and Ahuja (1990), Rodhe (1990),
Derwent (1990), WRI (1990), and Nordhaus
(unpublished).
The concept of global warming potential
developed by the IPCC is based on a
comparison of the radiative forcing effect of
the concurrent emission into the atmosphere
of an equal quantity of CO2 and another
greenhouse gas. Each gas has a different
instantaneous radiative forcing effect. In
addition, the atmospheric concentration
attributable to a specific quantity of each gas
declines with time. In general, other
greenhouse gases have a much stronger
instantaneous radiative effect than does CO2;
however, CO2 has a longer atmospheric
lifetime and a slower decay rate than most
other greenhouse gases. Atmospheric
concentrations of certain greenhouse gases
may decline due to atmospheric chemical
processes, which in turn create other
greenhouse gases or contribute to their
creation or longevity. These indirect effects
are included in the GWP of each gas.
Following this convention, the GWP is
defined as the time-integrated commitment to
climate forcing from the instantaneous release
of 1 kilogram of a trace gas expressed relative
to that from 1 kilogram of carbon dioxide.5
The magnitude of the GWP is, however,
sensitive to the time horizon over which the
analysis is conducted (i.e., the time period over
which the integral is calculated). For example,
Table 2-3 summarizes the GWPs of key
greenhouse gases assuming 20-year, 100-year,
11-36
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Chapter II: Greenhouse Gas Trends
FIGURE 2-10
CONTRIBUTION TO RADIATIVE FORCING
(a) By Greenhouse Gas
Concentrations
Other (10%)
Other CFC« (3%)
CFC-11*
-12(14%)
O (5%)
C02(49%)
(b) By Greenhouse Gas
Emissions on a C02-Equivalent Basis
Using a 100-Year Time Horizon
Other CFC» (3%)
CFC-11 *-l2(»%)
Other (3%)
CH4(18%)
C02(«2%)
1980s
1985
Sources: Hansen et al., 1988; IPCC, 1990.
H-37
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Policy Options Tor Stabilizing Global Climate
Trace Gas
Carbon Dioxide
Methane
Nitrous Oxide
CFC-11
CFC-12
HCFC-22
CFC-113
CC14
CH3CC13
CF3Br
CO
TABLE 2-3
Global Warming Potential for Key Greenhouse Gases
Lifetime
(Years)
10
150
60
130
15
90
50
6
110
Global Warming Potential
(Integration Time Horizon. Years)
20
1
63
270
4500
7100
4100
4500
1900
350
5800
7
100
1
21
290
3500
7300
1500
4200
1300
100
5800
3
500
1
9
190
1500
4500
510
2100
460
34
3200
2
a Atmospheric retention of CO2 is very complex. It is not destroyed like many other gases, but can
be transferred to other reservoirs such as the oceans or biota and then return to the atmosphere. The
IPCC used an approximate lifetime of 120 years by explicitly integrating the box diffusion model of
Siegenthaler (1983).
b Lifetime of CO was not provided, although its lifetime is generally no more than a few months.
Source: IPCC, 1990.
11-38
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Chapter II: Greenhouse Gas Trends
and 500-year time horizons. The assumed
integration period defines the time period over
which the. radiative effects of the gas are
measured. These GWPs indicate, for example,
that 1 kilogram of methane emissions is
estimated to have 21 times the impact on
radiative forcing as 1 kilogram of carbon
dioxide for a 100-year time horizon. If a 500-
year time horizon is assumed, however,
methane is estimated to have only 9 times the
impact on radiative forcing compared to an
equivalent amount of carbon dioxide. The
differences between the values for 100 years
and 500 years incorporate the differences in
atmospheric lifetime. Because methane is a
much shorter-lived gas than carbon dioxide -
10 years versus 120 years6 - its relative
contribution to global climate change will
decrease (increase) over time as the time
horizon increases (decreases).
For this discussion we will use the
GWPs presented in Table 2-3 for a mid-level
time horizon, i.e., 100 years, to convert all
greenhouse gases to a CO2-equivalent basis so
that the relative magnitudes of different
quantities of different greenhouse gases can be
readily compared. There is nothing
particularly unique about this time horizon.
Nevertheless, it is sufficiently long that many
of the atmospheric processes currently thought
to affect concentrations can be considered
without excessively weighting longer-term
impacts on atmospheric processes that are not
well understood.
Using the GWPs presented in Table 2-3,
we can estimate the relative contribution of
each greenhouse gas to global warming for any
set of greenhouse gas emission estimates. For
example, in Figure 2-10b we present the
contributions to global warming by greenhouse
gas using the global emission estimates for
each gas for the base year 1985 and the 100-
year GWPs. For purposes of comparison we
also have included the contributions to global
warming by gas for the 1980s based on
estimates of the increase in atmospheric
concentrations of each gas during the 1980s
(Figure 2-10a; also presented in the Executive
Summary and Figure 2-1 based on Hansen et
al., 1988). Conceptually, the approaches used
here are quite different. Hansen et al. (1988)
base their approach on the radiative forcing
effects of estimated differences in atmospheric
concentrations between 1980 and 1990. Since
only changes in atmospheric concentrations
are considered, Hansen's approach ignores any
portion of anthropogenic emissions that
maintains atmospheric concentrations at
previous levels, even if those levels are
elevated above pre-industrial concentrations.
The use of GWPs measures the radiative
forcing effects of emissions for a single year, in
this case, 1985, over a 100-year time frame;
this approach treats all anthropogenic
emissions as contributing to radiative forcing.
Differences occur for several other reasons,
including:
• The atmospheric concentration
changes in Hansen et al. (1988) include the
"decay" of CH4, CO, and non-methane
hydrocarbons (NMHC) to CO2 in the
atmosphere. The contribution of CO2
concentrations during the 1980s will therefore
be larger than the change due to CO2
emissions.
• Assumptions about atmospheric
lifetimes differ. For example, the IPCC
assumed CFC-11 had a lifetime of 60 years;
Hansen et al. (1988) assumed 75 years. For
CFC-12 the IPCC assumed 130 years; Hansen
et al. assumed 150 years.7 Additionally,
atmospheric lifetime assumptions are only
important to Hansen et al. to the extent they
affect the atmospheric chemistry from 1980-90.
• The time period of the analyses
differ. The GWPs are based on emission
effects over a 100-year time frame, while
Hansen et al. base their determination on the
estimated changes in atmospheric composition
over a 10-year period.
• The Hansen et al. pie chart
(Figure 2-10a) includes the impacts for
stratospheric water vapor and tropospheric
ozone directly in the "Other" category; the pie
chart using 100-year GWPs (Fig 2-10b)
includes these effects in the calculations of the
GWPs for the greenhouse gases, e.g., the GWP
for CH4 includes the effect that CH4 has on
the production of stratospheric water vapor
and tropospheric ozone.
11-39
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Policy Options for Stabilizing Global Climate
NOTES
1. peta = 1015, giga = 109, 1 ton = 106
grams. Thus, 1 petagram (Pg) = 1 gigaton
(Gt).
2. A radical is an atom or group of atoms
with at least one unpaired electron, making it
highly reactive.
3.
4.
kg-
1 Tg = 1 teragram = 10 grams.
1 Gg = 1 gigagram = 109 grams = 106
5. The discussion here focuses on the use
of Global Wanning Potentials, where all gases
are compared relative to carbon dioxide. This
approach is used since, among other things,
carbon dioxide is the largest contributor to
radiative forcing. However, there is no reason
why another gas could not be used as the
common denominator, e.g., all gases could be
expressed on a methane-equivalent basis.
6. The atmospheric lifetime of CO2 is
difficult to estimate due to the complex nature
of the carbon cycle. Carbon dioxide is not
destroyed like many other gases, but can be
transferred to other reservoirs such as the
oceans or biota and then return to the
atmosphere. The IPCC used an approximate
lifetime of 120 years by explicitly integrating
results of the box diffusion model of
Siegenthaler (1983).
7. Hansen et al. (1988) did not provide
atmospheric lifetime assumptions for all of the
greenhouse gases.
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Research 90:10529-10540.
Barnola, J.M., D. Raynaud, Y.S. Korotkevich,
and C. Lorius. 1987. Vostok ice core
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CO2. Nature 329:408-414.
Bingemer, H.G., and P.J. Crutzen. 1987. The
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Journal of Geophysical Research 92:2181-2187.
Blake, D.R., and F.S. Rowland. 1986.
World-wide increase in tropospheric methane,
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Blake, D.R., and F.S. Rowland. 1988.
Continuing worldwide increase in tropospheric
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Seiler, W., H. Giehl, E.E. Branke, and E.
Halliday. 1984. The seasonality of carbon
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Shiller, A.M. 1981. Calculating the oceanic
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Biospheric CO2 emissions during the past 200
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Stauffer, B., G. Fischer, A. Neftel, and H.
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11-49
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CHAPTER III
CLIMATE CHANGE PROCESSES
FINDINGS
• Climate exhibits natural variability on
all time scales, from seasons to millions of
years. This variability is caused by a
combination of changes in external factors,
such as solar output, and internal dynamics
and feedbacks, such as the redistribution of
heat between the atmosphere and the oceans.
• The ultimate warming that can be
expected for a given increase in greenhouse
gas concentrations is uncertain due to our
inadequate understanding of the feedback
processes of the climate system. For the
benchmark case of doubling carbon dioxide
concentrations, the National Academy of
Sciences has estimated that the equilibrium
increase in global average temperature would
most likely be in the range of 1.5-4.5°C. The
Interim Report of the Intergovernmental Panel
on Climate Change (IPCC) states:
The evidence from the modelling
studies, from observations and the
sensitivity analyses indicate that the
sensitivity of global mean surface
temperature to doubling CO2 is
unlikely to lie outside the range 1.5
to 4.5°C ... for the purpose of
illustrating the IPCC Scenarios, a
value of 2.5°C is considered to be
the "best guess" in light of current
knowledge (IPCC, 1990, p. 145).
The largest factor contributing to these ranges
is uncertainty about how clouds will respond
to climate change.
• There are varieties of geochemical and
biogenic feedbacks that have generally not
been quantified in estimating the temperature
change that could occur for any given initial
increase in greenhouse gases. In particular, the
potential of future global warming to increase
emissions of carbon from northern latitude
reservoirs in the form of both methane and
carbon dioxide (CO2), to alter uptake of CO2
by oceans, and a variety of other temperature-
dependent phenomena indicate that the true
sensitivity of the Earth's climate system to
increased greenhouse gases could exceed 5.5°C
for an initial doubling of CO2. There are
biogenic and geochemical feedbacks that could
decrease greenhouse gas concentrations --
enhanced photosynthesis due to higher CO2,
for example. Although many of these
feedback processes -- both those that might
increase and those that might decrease
greenhouse gas concentrations - are poorly
understood, it seems likely that, overall, they
will act to increase, rather than decrease,
greenhouse gas concentrations in a warmer
world.
• Uncertainties about ocean circulation
and heat uptake, and about future internal
climate oscillations and volcanic eruptions,
make it difficult to predict the time-dependent
response of climate to changes in greenhouse
gas concentrations. Because the oceans delay
the full global warming that would be
associated with any increase in greenhouse
gases, significant climatic change could
continue for decades after the composition of
the atmosphere were stabilized. The Earth is
already committed to a total warming of about
0.7-1.5°C relative to pre-industrial times
(assuming that the climate sensitivity to
doubling CO2 is 2-4°C). The Earth has
warmed by 0.3-0.7°C during the last century,
which is not inconsistent with expectations
given the uncertain delay caused by ocean heat
uptake. The temperature record over the last
century, however, cannot now be used to
confirm or refute specific model predictions.
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Policy Options for Stabilizing Global Climate
INTRODUCTION
The increasing concentrations of
greenhouse gases documented in the last
chapter are expected to alter significantly the
Earth's climate in the coming decades. The
magnitude and timing of actual climatic
change will be determined by future emissions
(see CHAPTER VI), by changes in other
climate forcings, and by the sensitivity of the
climate system to perturbations. Weather and
climate (the time-average of weather) are
determined by complex interactions between
the atmosphere, land surface, snow, sea ice,
and oceans, involving radiative and convective
exchange of energy within and among these
components. As is readily apparent, this
system exhibits considerable variability from
day to day, month to month, and year to year.
Systematic diurnal (day-night) and
seasonal variations are driven by changes in
the distribution and amount of solar energy
reaching the top of the Earth's atmosphere as
the Earth rotates on its axis and orbits around
the sun. Changes in the amount of energy
emitted by the sun, changes in the Earth's
orbit, changes in atmospheric composition
(due to volcanic eruptions and human input of
aerosols and greenhouse gases), and changes in
the earth's surface (such as deforestation) can
also affect the Earth's energy balance over the
long term. Such factors are considered
"external forcings" because they do not depend
on the state of the climate system itself.
In contrast, much of the day-to-day and
year-to-year variation results from the internal
dynamics of the climate system. For example,
the polar front may be unusually far south in
North America during a given year, producing
colder-than-normal weather in the northern
Great Plains, but there can be warmer-than-
average weather somewhere else, leaving the
global average more or less unchanged.
Similarly, upwelling of cold water off the
Pacific Coast of South America may fail for
several years. This irregularly recurring event,
referred to as El Nino, leads to various
regional weather anomalies, impacts like the
collapse of the Peruvian anchovy fishery, and
wanner global temperatures. In this case there
is a temporary net release of heat from the
ocean to the atmosphere, which is usually
followed by a reversal, sometimes referred to
as La Nina (Ken, 1988). Such variations of
the atmospheric and oceanic circulation can
produce anomalous redistributions of energy
in the climate system resulting in climate
variations with amplitudes and time scales that
may be comparable to climate changes
expected from past increases in greenhouse
gases (Lorenz, 1968; Hasselmann, 1976;
Robock, 1978; Hansen et al., 1988).
In order to determine precisely the
potential effects of the input of greenhouse
gases on future climate, it would be necessary
not only to be able to understand all the
physics of the climate system and the effects of
each potential cause of climate change, but
also to be able to predict the future changes of
these forcings. If we could do this, we could
explain past climate change and separate the
effects of greenhouse gases from the other
factors that have acted during the past 100
years for which we have instrumental
temperature records. We could also use
theoretical climate models to calculate the
future size and timing of climate changes due
to greenhouse gases. Since our measurements
of past climate are incomplete, our
understanding of the climate system is
incomplete, and some (not well known)
portion of climate change is random and
unpredictable, we can only estimate the impact
of greenhouse gas buildup within a broad
range of uncertainty.
To place in context the potential
warming due to increasing greenhouse gas
concentrations, in this chapter we discuss the
magnitude and rate of past changes in climate
and the various factors that influence climate.
Feedback mechanisms that can amplify or
lessen imposed climate changes are discussed
next. The overall sensitivity of climate to
changes in forcing is then considered, followed
by a discussion of the time-dependent response
of the Earth system. The focus is on global
temperature as an indicator for the magnitude
of climate change. Regional climate and the
potential impacts of climate change are not
discussed here, but are considered in the
companion report Potential Effects of Global
Climate Change on the United States (Smith
and Tirpak, 1989).
III-2
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Chapter III: Climate Change Processes
CLIMATE CHANGE IN CONTEXT
The most detailed information on
climate is, of course, from the modern
instrumental record, but even this data set is
quite sparse in the Southern Hemisphere and
over the oceans. Wigley et al. (1986) reviewed
a number of recent analyses, noting that
independent groups (including Hansen et al.,
1981 and Vinnikov et al., 1980; more recent
publications are Hansen and Lebedeff, 1988
and Vinnikov et al., 1987), necessarily relying
on the same basic data sources but using
different data selection and averaging
approaches, have obtained very similar results.
Given the various uncertainties due to factors
such as poor spatial coverage in some regions,
changes in the number and location of
stations, local temperature changes due to
growth of urban areas, and changes in
instrumentation, Wigley et al. conclude that
the warming since 1900 has been in the range
of 0.3-0.7°C. The most complete and up-to-
date global surface air temperature record
available (Jones and Parker, 1990) is displayed
in Figure 3-la, which shows a global wanning
of about 0.3°C from 1900 to 1940, a cooling of
about 0.1°C from 1940 to 1975, and a warming
of about 0.2°C from 1975 to 1989. The six
warmest years in the global record occurred
during the 1980s: 1980,1981,1983,1987,1988,
and 1989. The overall warming is similar in
the land-air temperature record of the
Northern and Southern Hemispheres (see
Figures 3-lb,c), though the long-term trend is
steadier in the Southern Hemisphere where
the 1940-1975 cooling is less evident. While
the gradual warming seen in Figure 3-1 during
the past century is consistent with the
increasing greenhouse gases during this period
(see CHAPTER II), the pre-1940 wanning,
which is greater than expected from increases
in greenhouse gas concentration during this
period, the large interannual variations, and
the relatively flat curve from 1940 to 1975
show that there are also other important
causes of climate change. The differences
between the two hemispheres also show that
there are regional differences in the climate
response to a global forcing (greenhouse
gases), that important other forcings (such as
large volcanic eruptions) are not global in
their effects, or that internal climate variations
produce regional differences. Data for the
United States, for example, show that it
warmed by about half as much as the globe as
a whole during the last century (Hansen et al.,
1989). Because of past and potential future
emissions of greenhouse gases (see below and
CHAPTER VI), climate changes during the
next century may be greater than the variations
shown for the past 100 years.
Recent climate variations are put in a
longer-term perspective in Figures 3-2 through
3-4. The amplitude of climate change over the
last millennium (see Figure 3-2) is similar to
what has been seen during the last century.
The Medieval Warm Epoch (800-1200 AD)
may have been restricted to the North Atlantic
Basin (Wigley et al., 1986) and in any case
appears to have been about as warm as the
present. The Little Ice Age (1430-1850;
Robock, 1979) appears to have been as cool as
the early 20th century in parts of Europe. The
peak of the most recent glaciation is generally
given as 18 thousand years before the present
(kyBP) (see Figures 3-3, 3-4) with globally
averaged temperatures about 5°C cooler than
today (Hansen et al., 1984) between 15 and 20
kyBP. Even over the 700,000-year period
illustrated in Figure 3-4 the maximum global
temperature swing appears to have been no
greater than about 5°C, with the periods of
greatest warmth being the present and the
interglacial peaks, which occurred
approximately every 100,000 years for the past
million years. The temperature change shown
in Figure 3-3 is for Antarctica and is
substantially greater than what is believed to
represent the globe as a whole. (Such high-
latitude amplification of temperature increases
is predicted for greenhouse-induced warming
in the future.) The CO2 variations are, in
general, in step with the temperature
variations deduced from deuterium variations
in the same ice core (Jouzel et al., 1987),
suggesting that CO2 was important in
amplifying the relatively weak orbital forcings
during past climate variations (Genthon et al.,
1987; see Orbital Parameters below). While
it is difficult to assign a cause for these past
changes, it is reasonable to conclude that,
given current greenhouse gas concentrations,
global temperatures will soon equal or
exceed the maximum temperatures of the past
million years.
III-3
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Policy Options for Stabilizing Global Climate
FIGURE 3-1
(a)
SURFACE AIR TEMPERATURE
(Degrees Celsius)
Global
-0.5
(b)
1860 1880 1900 1920 1940 1960 1980 2000
YMT
Northern Hemisphere
(c)
'850 1870 I8» 1910 1930 1950 1970 1990
Southern Hemisphere
-0.5
1870
1890
1910
1930
1950
1970
Figure 3-1. (a) Global surface air temperature, 1856-1989, relative to the 1951-1980 average. The
gradual wanning during this period is consistent with the increasing greenhouse gases during this
period, but the large interannual variations and the relatively flat curve from 1940 to 1975 show that
there are also other important causes of climate change. (Source: Jones and Parker, 1990 -
Copyright © 1990 by the AAAS.)
(b,c) Land surface air temperatures, 1851-1987 for the Northern Hemisphere and 1857-1987 for the
Southern Hemisphere. Note the larger interannual variability before 1900, when data coverage was
much more sparse. (Source: Jones, 1988.)
IH-4
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Chapter III: Climate Change Processes
FIGURE 3-2
O
'O
AD
Figure 3-2. Oxygen isotope (<518O) variations from ice cores in Greenland. This is an index of
Northern Hemisphere temperature, with the maximum range equal to about 1°C. (Source: record
of Dansgaard as given by Lamb, 1977.)
FIGURE 3-3
Figure 3-3. Carbon dioxide levels and temperatures over the last 160,000 years from Vostok 5 Ice
Core in Antarctica. The temperature scale is for Antarctica; the corresponding amplitude of global
temperature swings is thought to be about 5°C. (Source: Barnola et al., 1987. Reprinted by
permission from Nature, Vol. 329, pp. 408-414. Copyright © 1987 Macmillan Journals Limited.)
FIGURE 3-4
O
s
0 0
iTES 1234
11 12
13 14 15 16 17 « S 2C
100
200 300 403
AGE IN THOUSANDS OF YEARS
500
600
700
Figure 3-4. Composite 518O record of Emiliani (1978) as given by Berger (1982). This comes from
deep sea sediment cores and is an index of global temperature, with the temperature range from stage
1 (present) to stage 2 (18,000 years ago) equal to about 5°C.
III-5
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Policy Options for Stabilizing Global Climate
CLIMATE FORCINGS
The patterns of climate variations
discussed in the last section are the result of a
combination of external forcings, internal
feedbacks, and unforced internal fluctuations.
The strictly external forcings are changes in
solar output and variations in the Earth's
orbital parameters, while changes in aerosols
and greenhouse gas concentrations may be
viewed as external forcings or internal
feedbacks, depending on the time scale and
processes considered. The sensitivity of the
climate system is determined by the feedbacks
that modify the extent to which climate must
change to restore the overall energy balance of
the Earth as external forcings change.
Solar Luminosity
The solar luminosity (or total energy
output from the sun) has an obvious and
direct influence on climate by determining the
total energy reaching the top of the Earth's
atmosphere. Theories of stellar evolution
suggest that solar output was 25% lower early
in Earth history, but geologic evidence and the
fact that life was able to evolve on Earth show
that the Earth was not an inhospitable ice-
covered planet. An important part of the
explanation for this "faint young sun paradox"
now appears to be that the CO2 content of the
atmosphere was many times higher than it is
at present. The enhanced greenhouse effect
from CO2 was probably the main factor in
counteracting the lower solar luminosity (see
below). Geochemical models suggest that over
millions of years CO2 has acted as an internal
feedback that has kept the Earth's climate in
a habitable range (Walker et. al., 1981; Berner
and Lasaga, 1988; see Figure 3-3).
Solar luminosity also varies by small but
significant amounts over shorter time periods.
Various attempts have been made to explain
past climate variations by assuming a link
between solar luminosity and observed
parameters, such as sunspot activity, solar
diameter, and the umbral-penumbral ratio
(Wigley et al., 1986). Unfortunately,
measurements with sufficient precision to
detect insolation changes have only been
available since 1979 - too short a time period
to be able to definitively confirm or refute the
proposed relationships. These measurements
show a decline in solar luminosity between
1980 and 1986; whereas the most recent data
show a reversal of this trend (Willson and
Hudson 1988; Willson et al., 1986). The
luminosity data are positively correlated with
sunspot number and suggest an 11-year cycle
with an amplitude of 0.04% or 0.1 watts per
square meter (W/m2) at the top of the
atmosphere (Willson and Hudson, 1988).
Orbital Parameters
Cyclic changes in the Earth's orbital
characteristics are now widely accepted as the
dominant trigger behind the glacial/interglacial
variations evident in Figure 3-3 and extending
back to at least 1.7 million years before
present (e.g., Wigley et al., 1986; COHMAP,
1988). While causing only small changes in
the total radiation received by the Earth, the
orbital changes (known as the Milankovitch
cycles) significantly alter the latitudinal and
seasonal distribution of insolation. For
example, Northern Hemisphere summer
insolation was about 8% greater 9 kyBP than
it is now, but winter insolation was 8% lower.
Changes of this type, in combination with
internal feedbacks as discussed below, are
presumed to have determined the pattern of
glaciations and deglaciations revealed in the
geologic record. Attempts have been made to
compare model predictions with paleoclimatic
data. There has been reasonably good
agreement between the two, given specified ice
sheet extent and sea surface temperatures
(COHMAP, 1988; Hansen et al., 1984). To
the extent that the Milankovitch explanation
of ice ages is correct, one would expect the
Earth to be heading toward a new ice age over
the next 5000 years, but the very gradual
changes in orbital forcings expected in this
period will be overwhelmed if current trends
in greenhouse gas concentrations continue
(Wigley et al., 1986).
Volcanoes
Large volcanic eruptions can
significantly increase the stratospheric aerosol
concentration, increasing the planetary albedo
and reducing surface temperatures by several
tenths of one degree for several years (Hansen
et al., 1978, 1988; Robock, 1978, 1979, 1981,
1984). Because of the thermal inertia of the
climate system, discussed below, volcanoes can
III-6
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Chapter III: Climate Change Processes
even be responsible for climate changes over
decades, and in fact the warming shown in
Figure 3-1 from 1920 to 1940 may be
attributable to a period with very few volcanic
eruptions (Robock, 1979). Since large
eruptions occur fairly frequently and cannot
now be predicted, this component of climate
change will have to be considered when
searching past climate for a greenhouse signal
and when projecting future climate change.
Surface Properties
The Earth's radiative balance can also
be changed by variations of surface properties.
While interactions with the ocean, which
covers 70% of the Earth's surface, are
considered internal to the climate system and
are discussed below, land surfaces also exert a
strong influence on the climate. Human
activities, such as deforestation, not only
provide a source of carbon dioxide (CO2) and
methane (CH4) to the atmosphere, but also
change the surface albedo and moisture flux
into the atmosphere. Detailed land surface
models, incorporating the effects of plants, are
now being developed and incorporated into
general circulation model (GCM) studies of
climate change (Dickinson, 1984; Sellers et al.,
1986).
The Role of Greenhouse Gases
The greenhouse effect does not increase
the total energy received by the Earth, but it
does alter the distribution of energy in the
climate system by increasing the absorption of
infrared (IR) radiation by the atmosphere. If
the Earth had no atmosphere, its surface
temperature would be strictly determined by
the balance between solar radiation absorbed
at the surface and emitted IR. The amount of
IR emitted by any body is proportional to the
fourth power of its absolute temperature, so
that an increase in absorbed solar radiation
(due to increased solar luminosity or decreased
albedo, for example) would be balanced by a
small increase in the surface temperature,
increasing IR emissions until they are again
equal to the absorbed solar radiation. The
role of greenhouse gases can be understood by
thinking about the atmosphere as a thin layer
that absorbs some fraction of the IR emitted
by the surface (analogous to the glass in a
greenhouse). The energy absorbed by the
atmosphere is then re-emitted in all directions,
and the downward half of this energy flux
warms the surface (see Figure 3-5). Higher
concentrations of greenhouse gases increase
the IR absorption in the atmosphere, raising
surface temperatures.
Changes in the atmosphere's radiative
properties can result from external
perturbations (such as anthropogenic
emissions of CO2) or from internal
adjustments to climate change. The amount of
water vapor, the dominant greenhouse gas, is
directly determined by climate and contributes
the largest positive feedback to climate change
(Hansen et al., 1984; Dickinson, 1986).
Similarly, clouds are an internal part of the
climate system that strongly influence the
Earth's radiative balance (Ramanathan et al.,
1989). Changes in the concentrations of other
greenhouse gases may be imposed by human
activity or may result from changes in their
sources and sinks induced by climate change.
Such feedbacks are discussed below.
Internal Variations
As discussed in the introduction, even
with no changes in external forcings, climate
still exhibits variations due to internal
rearrangements of energy within the
atmosphere and between the atmosphere and
the ocean. The total amplitude and time
scales of these internal stochastic climate
variations are not well known; these variations
therefore pose an additional difficulty in
interpreting the past record and projecting the
level of future climate change.
PHYSICAL CLIMATE FEEDBACKS
Any imposed imbalance in the Earth's
radiative budget, such as discussed above, will
be translated into a changed climate through
feedback mechanisms, which can act to amplify
or decrease the initial imposed forcing. In this
section, several of these mechanisms which are
internal to the physical climate system are
discussed. The next section describes several
recently investigated mechanisms involving the
planet's biology and chemistry.
HI-7
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Policy Options for Stabilizing Global Climate
FIGURE 3-5
(a)
i
t
i
Atmos
t
1
GLOBAL ENERGY BALANCE
1 / (Watts/Square Meter)
\^_ 1 Solar | Infrared 1
^ , / ' * *
340 \ 100 90 150 86
\
\ '
i
154
I
?ph«re 30° 308
llXCO, !2XCO,
i 2 i 2 i
\ a i
\ I
\ 240 390 150 394 154
1 t f
^rr ^rr _i>~ 1X" >^
Earth's Surface ^^ ^^ ^^
'jy -'•*' V" V' j/* s
(b)
SPACE INCOMING
SOLAR OUTGOING RADIATION
RADIATION Shortwave Longwave
340 27 M 20 31 13* *•
/ / / f f f
ATMOSPHERE ^\. Back«:atter«d / / ., , ' V^,
\\\ by A,r / / Net Ebm'"lon s+C ^V,
Absorbed by J \ \ V / / Water Vapor, Emission
Water Vapor. 66^ \ \ ., / / COj.Oj by Clouds
_ _ \ Reflected / z 3
Du"'°3 \ by Clouds / Absorpt.on
\ \/ / &V Clouds i
/ \ _/*T^>-S / Water Vapor.
Absorbed by \ R.,,^ 1 "e" rlu*
Clouds \ by Surfae, Sensible
Absorbed \ / LONGWAVE RADIATION H"' F'UX
16< 390 340 24 82
OCEAN. LAND
Figure 3-5. (a) Highly simplified schematic of the global energy balance illustrating the mechanism
by which increased greenhouse gas concentrations warm the Earth's surface. The atmosphere is
treated as a thin layer that does not absorb solar radiation; the role of convective and latent heat
transfer is also neglected. Doubling the concentration of CO2 increases the absorption and emission
of infrared radiation by the atmosphere, increasing the total energy absorbed at the surface. In the
equilibrium depicted, total emissions to space remain unchanged.
(b) A more realistic schematic of the global energy balance for current conditions. (Source: adapted
from MacCracken, 1985.)
HI-8
-------
Chapter III: Climate Change Processes
By no means do we understand or even
know about all the mechanisms involved in
climate feedbacks. Figure 3-6 shows some of
the physical climate feedbacks involved in
changing surface temperature. Current state-
of-the-art climate models attempt to
incorporate most of the physical feedbacks
that have been identified, but provide a very
crude treatment for one of the most important
- changes in clouds - because of inadequate
understanding of cloud physics and because of
the small spatial scale on which clouds form
compared to the resolution of climate models
(see Clouds below).
Water Vapor
When the climate warms, the
atmosphere can hold more water vapor. The
additional water vapor, which is a greenhouse
gas, amplifies the initial warming, which in
turn results in still more evaporation from the
warmed surface. This positive feedback acts to
approximately double imposed forcings.
Snow and Ice
When climate warms, snow and ice
cover are reduced, exposing land or ocean with
a lower albedo than the snow or ice. In
addition, the albedo of the remaining snow
and ice is reduced because of meltwater
puddles and debris on the surface. This
reduced albedo causes more energy to be
absorbed at the surface, further enhancing the
warming. This albedo feedback was originally
thought to be the dominant positive feedback
effect of snow and ice, but it now appears that
the thermal inertia feedback of sea ice plays a
more important role (Manabe and Stouffer,
1980; Robock, 1983). The albedo feedback
requires that the sun be shining, and since the
maximum ice and snow extent is in the winter,
the feedback plays a small role in influencing
the albedo except in the spring, when the snow
and ice are present along with high insolation.
The thermal inertia feedback acts to
increase the thermal inertia of the oceans
when climate warms by melting sea ice,
reducing its insulating effect and increasing the
transfer of heat from the ocean to the
atmosphere at high latitudes. This effect acts
to reduce the seasonal cycle of surface
temperature and is the prime reason for the
enhancement of imposed climate change in the
polar regions in the winter (Robock, 1983). If
sea ice retained its current seasonal cycle,
there would be no preferential latitude or time
of year for climate change.
Clouds
Clouds respond directly and immediately
to changes in climate and probably represent
the most important uncertainty in determining
the sensitivity of the climate system to the
buildup of greenhouse gases. Fractional cloud
cover, cloud altitude and cloud optical depth
can all change when climate changes
(Schlesinger, 1985). It has not been possible
to determine the net effect of cloud feedbacks
because all these properties of clouds can
change simultaneously, because clouds affect
long-wave radiation, short-wave radiation, and
precipitation (which affects soil moisture and
hence albedo, thermal inertia, and moisture
flux of land), and because the net effect
depends on the location of the cloud (in three
dimensions), the underlying surface albedo,
and the time of day and year of the changes.
The current net effect of clouds is to cool the
planet, but this does not imply that changes in
clouds will decrease the impact of higher
greenhouse gas concentrations (Ramanathan
et al., 1989). Roeckner et al. (1987) and
Somerville and Remer (1984) argue that the
liquid water content of clouds will increase
with warming, substantially altering their
optical properties. A comparison of recent
results with and without cloud optical property
feedbacks shows that including this mechanism
can increase or decrease total cloud feedback,
depending on related changes in other cloud
properties (Cess et al., 1989). Overall, a
comparison of 14 GCMs found that the impact
of cloud feedback ranged from a modest
decrease in climate sensitivity (30%) to a large
increase (150%) (Cess et al., 1989).
BIOGEOCHEMICAL CLIMATE FEEDBACKS
In addition to the climatic processes
discussed above, a number of biogeochemical
feedback processes will influence future
concentrations of greenhouse gases and
climate change. Increased greenhouse gas
concentrations will alter not only the climate,
but also biogeochemical processes that affect
sources and sinks of radiatively important
III-9
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Policy Options for Stabilizing Global Climate
FIGURE 3-6
EQUILIBRIUM TEMPERATURE CHANGES FROM DOUBLED CO,
4
(Based on 1.5-5.5 Degree Sensitivity)
5.5
5.0
4.5
4.0
I 3.5
I
S 3.0
I
Q 2.5
2.0
1.5
1.0
0.5 -
0
Water
Vapor
Clouds
No
Feedbacks
AT
w
AT
AT
AT
ws
AT
w*c
Figure 3-6. Equilibrium temperature changes from doubling CO2 (AT^) inferred from a review of
the strength of individual feedback processes in various climate models. AT0 is the temperature
increase expected from doubling CO2 with no feedbacks. The subscripts w, s, and c, refer to feedbacks
due to water vapor and lapse rate, sea ice and surface albedo, and clouds, respectively. Each bar
shows the estimated two-standard deviation range of equilibrium global warming with the indicated
feedbacks included. (Source: adapted from Dickinson, 1986.)
111-10
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Chapter III: Climate Change Processes
gases. Climatically important surface
properties, such as albedo and evapo-
transpiration, will also be modified by
vegetation changes. The major biogeochemical
feedback links, illustrated in Figure 3-7, can be
categorized as follows: physical effects of
climate change, changes in marine biology, and
changes in terrestrial biology. Potential
physical effects of climate change include
release of methane hydrates and changes in
ocean chemistry, circulation, and mixing.
Changes in marine biology may alter the
pumping of CO2 from the ocean surface to
deeper waters and the abundance of biogenic
cloud condensation nuclei. Potential
biological responses on land include changes
in surface albedo, increased flux of CO2 and
CH4 from soil organic matter to the
atmosphere due to higher rates of microbial
activity, increased sequestering of CO2 by the
biosphere due to CO2 fertilization, and
changes in moisture flux to the atmosphere.
Release of Methane Hydrates
Potentially the most important
biogeochemical feedback is the release of CH4
from near-shore ocean sediments. Methane
hydrates are formed when a CH4 molecule is
included within a lattice of water molecules;
the ratio can be as small as 1:6, that is, one
methane molecule for every six water
molecules (Bell, 1982). The hydrate structure
is stable under temperature and pressure
conditions that are typically found under a
water column of a few hundred meters or
more in the Arctic and closer to a thousand
meters in warmer waters; the region where
hydrates are found can start at the sea floor
and extend up to a few hundred meters into
the sediment, depending on the geothermal
temperature gradient (Kvenvolden and
Barnard, 1984). Estimates of the total
quantity of CH4 contained in hydrates range
from 2X103 to 5xl06 petagrams (Pg)
(Kvenvolden, 1988). Given the climate change
associated with a doubling of CO2, Bell (1982;
as corrected by Revelle, 1983) estimated that
there could be a release of —120 teragrams
(Tg) CH4 per year from Arctic Ocean
sediments, and Revelle (1983) calculated
global emissions of —640 Tg CH4/yr from
continental slope hydrates. These estimates,
however, are highly uncertain both because the
total quantity of hydrates potentially subject to
destabilization is not known and because
bottom water may be insulated from surface
temperature increases throughout much of the
ocean (Kvenvolden, 1988). Nonetheless, a
very strong positive feedback from this source
cannot be excluded at this time.
Oceanic Change
The oceans are the dominant factor in
the Earth's thermal inertia to climate change
as well as the dominant sink for anthropogenic
CO2 emissions. The mixed layer
(approximately the top 75 meters) alone
contains about as much carboji (in the form of
H2CO3, HCO3', and CO3=) as does the
atmosphere (see CHAPTER II). Furthermore,
the ocean biota play an important role in
carrying carbon (as organic debris) from the
mixed layer to deeper portions of the ocean
(see, e.g., Sarmiento and Toggweiler, 1984).
Thus, changes in ocean chemistry, biology,
mixing, and large-scale circulation have the
potential to substantially alter the rate of CO2
accumulation in the atmosphere and the rate
of global warming.
Because the oceans are such an integral
part of the climate system, significant changes
in the oceans are likely to accompany a change
in climate. For example, the oceans are
responsible for about 50% of heat transport
from the equator toward the poles (Dickinson,
1986), surface mixing is driven by winds, and
deep circulation is driven by thermal and
salinity gradients. The feedbacks involving the
ocean can be divided into three categories:
the direct effect of temperature on carbonate
chemistry, reduced mixing due to increased
stability of the thermocline, and the possibility
of large-scale reorganization of ocean
circulation and biological activity.1
Ocean Chemistry
The most straightforward feedback is on
ocean carbonate chemistry. As the ocean
warms, the solubility of CO2 decreases and the
carbonate equilibrium shifts toward carbonic
acid; these effects combine to increase the
partial pressure of CO2 (pCO2) in the ocean
by 4-5%/°C for a fixed alkalinity and total
carbon content. Because the total carbon
content would only have to decrease by about
one-tenth this amount to restore pCO2 to its
111-11
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Policy Options for Stabilizing Global Climate
FIGURE 3-7
GREENHOUSE GAS FEEDBACK PROCESSES
TRACE GAS SOURCES
TRACE GAS SINKS
i
i
TRACE GAS CONCENTRATIONS
CLIMATIC CHANGE
OCEAN CIRCULATION/
OCEAN BIOLOGY
VEGETATION ALBEDO
EVAPOTRANSPIRATION
1
NATURAL ECOSYSTEM
DISTRIBUTION
i
Figure 3-7. Schematic diagram of biogeochemical feedback processes. Changes in trace gas
concentrations produce climate change, which may affect ocean CO2 uptake and the global
distribution of natural ecosystems. Changes in ecosystem distribution affect surface albedo,
evapotranspiration, the terrestrial component of the carbon cycle (both CO2 and CH4), and
agriculture. Climate change can also directly affect these properties of the biosphere through the
temperature and precipitation responses of given ecosystems. Global wanning may also lead to
methane emissions from hydrates and changes in energy use. Finally, changes in trace gas
concentrations, particularly CO2, directly affect natural and agricultural ecosystems.
111-12
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Chapter HI: Climate Change Processes
previous level, the impact of this feedback is
to increase atmospheric CO2 by about 1%/°C
for a typical scenario (Lashof, 1989; see
CHAPTER VI).
Ocean Mixing
As heat penetrates from the mixed layer
of the ocean into the thermocline, the
stratification of the ocean will increase and
mixing can be expected to decrease, resulting
in slower uptake of both CO2 and heat. This
feedback raises the surface temperature that
can be expected in any given year for two
reasons. First, the atmospheric CO2
concentration will be higher because the
oceans will take up less CO2. Second, the
realized temperature will be closer to the
equilibrium temperature due to reduced heat
transport into the deep ocean (see THE RATE
OF CLIMATE CHANGE below).
Ocean Biology and Circulation
A more speculative, but potentially
more significant, feedback involves the
possibility of large-scale changes in the
circulation of the atmosphere-ocean system as
suggested by Broecker (1987). This possibility
is illustrated by the apparently very rapid
changes in the CO2 content of the atmosphere
during glacial-interglacial transitions as
revealed by ice-core measurements (e.g., Jouzel
et al., 1987; see Figure 3-2). Only shifts in
carbon cycling in the ocean are thought to be
capable of producing such large, rapid, and
sustained changes in atmospheric CO2. A
number of papers have attempted to model
the changes in ocean circulation and/or
biological productivity required to account for
the change in pCO2, emphasizing the
importance of high-latitude processes (Kerr,
1988; Sarmiento and Toggweiler, 1984;
Siegenthaler and Wenk, 1984; Knox and
McElroy, 1984). Given that continuation of
current trends could lead during the next
century to a climate change of the same
magnitude as that which occurred between
glacial and interglacial periods, one must take
seriously the possibility of sudden changes in
ocean circulation. Should this happen, the
rate of CO2 uptake by the ocean could change
substantially. The oceans could even become
a CO2 source rather than a sink -- significantly
accelerating climate change. Such changes in
circulation could also cause abrupt changes in
climate, a scenario that conflicts with the
general assumption that the warming will be
gradual (Broecker, 1987).
A different feedback involving ocean
biology has been proposed by Charlson et al.
(1987). It is also uncertain, but potentially
significant. Dimethyl sulfide (DMS) emitted
by marine phytoplankton may act as cloud
condensation nuclei in remote marine
environments, affecting cloud reflectivity and
therefore climate (Charlson et al., 1987; Bates
et al., 1987). Climate presumably affects
biogenic DMS production but the relationship
is complex and poorly understood at this time
(Charlson et al., 1987). While this mechanism
was originally proposed as a potential negative
feedback consistent with the Gaia Hypothesis
(Lovelock, 1988; Lovelock and Margulis,
1973), ice-core data indicate that aerosol levels
were higher during the last glacial maximum,
suggesting that biogenic DMS production may
act instead as a positive feedback (Legrand et
al., 1988). This is only one possible cloud
optical property feedback (discussed above),
and the net effect cannot be determined
because other cloud properties (amount,
elevation) would also change in a complex
way.
Changes in Terrestrial Biota
The terrestrial biota interact with
climate in a wide variety of important ways
(see Figure 3-7). The most significant effects
on climate may result from large-scale
reorganization of terrestrial ecosystems as well
as the direct effects of temperature and CO2
increases on carbon storage.
Vegetation Albedo
Probably the most significant global
feedback produced by the terrestrial biota, on
a decades-to-centuries time scale, is due to
changes in surface albedo (reflectivity) as a
result of changes in the distribution of
terrestrial ecosystems. Changes in moisture
flux patterns may also be globally important if
cloud properties are affected. Dickinson and
Hanson (1984) analyzed this problem and
found that the planetary albedo was 0.0022
higher at the glacial maximum due to
differences in mean annual vegetation albedo,
111-13
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Policy Options for Stabilizing Global Climate
an increase of about 0.7% over the current
albedo of 0.3. A similar result was obtained
by Hansen. et al. (1984) using a prescriptive
scheme to relate vegetation type to climate in
GCM simulations for current and glacial
times. This feedback may be less important in
the future than it was during the last
deglaciation because of direct human effects
on the surface, such as deforestation, and
because the pattern of vegetation change will
be different.
Carbon Storage
Other significant feedbacks are related
to the role of the terrestrial biosphere as a
source and sink for CO2 and CH4. The
carbon stored in live biomass and soils is
roughly twice the amount in atmospheric CO2,
and global net primary production (NPP) by
terrestrial plants absorbs about 10% of the
carbon held in the atmosphere each year. On
average this is nearly balanced by decay of
organic matter, about 0.5-1% of which is
anaerobic and thus produces CH4 rather than
CO2. Small shifts in the balance between NPP
and respiration, and/or changes in the fraction
of NPP routed to CH4 rather than CO2, could
therefore have a substantial impact on the
overall greenhouse forcing, because CH4 has a
much larger greenhouse effect than CO2 per
molecule. Both NPP and respiration rates are
largely determined by climate, and NPP is
directly affected by the CO2 partial pressure of
the atmosphere. Thus the potential for a
substantial feedback exists.
Other Terrestrial Biotic Emissions
The biosphere also plays an important
role in emissions of various other atmospheric
trace gases that are likely to be influenced by
climate change. For example, as much as half
of nitrous oxide (N2O) emissions are
attributed to microbial processes in natural
soils (Bolle et al., 1986). Emissions of N2O
tend to be episodic, depending strongly on the
pattern of precipitation events in addition to
temperature and soil properties (Sahrawat and
Keeney, 1986). Thus, climate change could be
accompanied by significant changes in N2O
emissions, although there is not sufficient
understanding of the microbiology to predict
these changes at present. The biosphere is
also a key source of atmospheric non-methane
hydrocarbons (NMHCs), which play an
important role in global tropospheric
chemistry; the oxidation of NMHCs generates
a substantial share of global carbon monoxide
(CO) and therefore influences the
concentration of the hydroxyl radical (OH)
and the lifetime of CH4 (Mooney et al., 1987;
Thompson and Cicerone, 1986). As much as
0.5-1% of photosynthate is lost as isoprene
and terpene (Mooney et al., 1987). Lamb et
al. (1987) found that the volume of biogenic
NMHC emissions in the United States is
greater than anthropogenic emissions by about
a factor of two. The ratio for the globe is
much greater. Emissions, at least for isoprene
and a-pinene are exponentially related to
temperature (Lamb et al., 1987; Mooney et al.,
1987). The first-order impact of climate
change, then, would be to increase NMHC
emissions, producing a positive feedback
through the CO-OH-CH4 link. The actual
impact when changes in ecosystem distribution
are considered is uncertain, however, as
different species have very different emissions
(Lamb et al., 1987).
Summary
Of the feedbacks that will come into
play during the next century, the largest will
almost certainly be the physical climate
feedbacks discussed earlier (water vapor,
clouds, ice cover, and ice and snow albedo). In
comparison, each individual biogeochemical
feedback discussed here is likely to be modest.
Because feedback systems are non-linear,
however, if the physical climate feedbacks
approach the positive end of their ranges, then
the overall sensitivity of the climate system
would be substantially increased by even small
additional feedbacks. If the physical feedbacks
are weak in net, then the biogeochemical
feedbacks may be less significant. Because
both the physical and biogeochemical
feedbacks are presently so poorly understood
and because other feedbacks may be
discovered, the overall equilibrium response of
the climate system (discussed below) can only
be specified with a fairly wide range.
The perturbations to global biogeo-
chemical cycles reflected in the feedback
processes discussed here are of great
importance in their own right in addition to
whatever warming they may produce. The
m-14
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Chapter III: Climate Change Processes
vegetation albedo feedback, for example,
contributed only 0.3°C out of the 3.6°C global
cooling in the ice-age analysis of Hansen et al.
(1984), but this represented a massive change
in terrestrial ecosystems. A better assessment
of both the impact of climate change on
biogeochemical cycles and the associated
feedbacks is needed. Several aspects of the
impact cf climate change on biogeochemical
processes are discussed in the companion
report Potential Effects of Global Climate
Change on the United States (Smith and
Tirpak, 1989). A quantitative estimate of the
impact of some of the feedbacks discussed
here is presented in Chapter VI based on
incorporating them in the Atmospheric
Stabilization Framework developed for this
study.
EQUILIBRIUM CLIMATE SENSITIVITY
When any forcing, such as an increase in
the concentration of greenhouse gases, is
applied to the climate system, the climate will
start to change. Since both the imposed
forcings and the climatic response are time-
dependent, and since the climate system has
inertia due to the response times of the ocean,
the exact relationship between the timing of
the forcings and the timing of the response is
complex. In an attempt to simplify the
problem of understanding the sensitivity of the
climate system to forcings, it has become a
standard experiment to ask the question,
"What would be the change in global average
surface air temperature if the CO2
concentration in the atmosphere were doubled
from the pre-industrial level, all other climate
forcings were held constant, and the climate
became completely adjusted to the new
radiative forcing?" This quantity is called the
"equilibrium climate sensitivity to doubled
CO2" and is indicated as ATjx (see Box 3-1).
The actual path that the climate system
would take to approach the equilibrium
climate would be determined by the time
scales of the forcings and the various elements
of the climate system. This is called the
"transient response" and is discussed in the
next section. Because the climate system
response always lags the forcing, there will
always be a built-in unrealized wanning that
will occur in the future, even if there are no
further increases in the forcing. Thus, there is
certain to be some future climate response to
greenhouse gases that were put into the
atmosphere in the past, even if concentrations
were stabilized starting today. Another way of
saying this is that societal responses to the
greenhouse problem that are undertaken now
will be felt for decades in the future, and lack
of action now will similarly bequeath climate
change to future generations.
Analysis of past climate change, and
model calculations of future climate change
can both be used to determine AT2X.
Unfortunately, our knowledge of both past
climate change and the responsible forcings
are too poor to reliably determine AT2X from
past data. Wigley and Raper (1987) estimate
that if all of the warming of the past 100 years
was due to greenhouse gases, then AT2x
would be approximately 2°C. If however, one
allows for other possible forcings, natural
variability, uncertainties in ocean heat uptake
and the transient response, and for
uncertainties in pre-industrial greenhouse gas
concentrations (see below; Hansen et al., 1985;
Wigley and Schlesinger, 1985; Wigley et al.,
1986; Wigley, 1989), then the climate record of
the last 100 years is consistent with any AT^
between 0 and 6°C (Wigley, pers.
communication).
Due to the various problems with direct
empirical approaches, mathematical models of
the climate system are the primary tool for
estimating climate sensitivity. While they have
inherent errors, they can isolate the
greenhouse forcing, and many theoretical
calculations can be made to test the
importance of various assumptions and various
proposed feedback mechanisms. The simplest
climate model is the zero-dimensional global
average model described in Box 3-1. Models
that are one-dimensional in the vertical, often
called "radiative-convective" models, and that
are one-dimensional in the horizontal, often
called "energy-balance" models, are very useful
for quickly and inexpensively testing various
components of the climate system. In order to
calculate the location of future climate change,
however, and in order to incorporate all the
important physical interactions, especially with
atmospheric circulation, fully three-
dimensional GCMs are necessary. These
sophisticated models solve simultaneous
equations for the conservation of energy,
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Policy Options for Stabilizing Global Climate
BOX 3-1. Simplified Modeling Framework
The concepts discussed in this chapter can be summarized in a simple zero-dimensional
or one-box model of climate as discussed by Dickinson (1986):
(1)
C(dAT/dt) + AAT = AQ
where AQ is the climate forcing and could be due to changes in solar output, volcanoes,
surface properties, stochastic processes, or greenhouse gases (as discussed in CLIMATE
FORCINGS and BIOGEOCHEMICAL CLIMATE FEEDBACKS); AT is the change in
tropospheric/mixed-layer temperature from the pre-industrial equilibrium climate; the
factor A, called the "feedback parameter" by Dickinson, gives the change in upward
energy flux resulting from a change in surface temperature, AT, and is the net result of
all the climate feedbacks (as discussed in the section on Climate Sensitivity); t is time;
and C is the effective heat capacity of the Earth, which is determined by the rate of heat
uptake by the ocean (C must be a function of time to account for the gradual penetration
of heat into an increasing volume of the deep ocean and changing sea ice cover). In
equilibrium the first term in (1) is zero, so the equilibrium climate sensitivity is simply
given by
(2)
AT = AQ/A.
For a doubling of CO2, AQ is about 4.3 W/m2, so the range 1.5-5.5°C of AT^ discussed
above corresponds to a range of 2.9-0.8 W m"2 °C"1 in A. This conceptual model, with
AQ calculated from changes in greenhouse gases and C replaced by a diffusive model of
the ocean, is incorporated into the Integrating Framework used in the modeling exercises
for this report (see CHAPTER VI and APPENDIX A).
momentum, mass, and the equation of state on
grids with horizontal resolution ranging from
3 to 8 degrees of latitude by 3 to 10 degrees of
longitude and with varying vertical resolution.
The radiation schemes attempt to account for
the radiatively significant gases, aerosols, and
clouds. They generally use different schemes
for computing cloud height, cover, and optical
properties. The models also differ in their
treatment of ground hydrology, sea ice, surface
albedo, and diurnal and seasonal cycles
(Schlesinger and Mitchell, 1985). Perhaps the
most important differences lie in the treatment
of oceans, ranging from prescribed sea surface
temperatures, to "swamp" oceans with mixed
layer thermal capacity but no heat transport,
to mixed layers with specified heat transport,
to full oceanic GCMs.
A series of reviews by the National
Academy of Sciences (NAS, 1979, 1983,1987)
as well as the "State-of-the-Art" report of the
Department of Energy (MacCracken and
Luther, 1985) have concluded that the
equilibrium sensitivity of climate to a 2xCO2
forcing (AT^) is probably in the range of 1.5
to 4.5°C. An independent review by Dickinson
(1986) attempts to quantitatively combine the
uncertainties indicated by the range of recent
GCM results and concludes that the range
should be broadened to 1.5-5.5°C. The GCM
result of Wilson and Mitchell (1987) giving
AT?x = 5-2°c was published after all of the
reviews cited here. Dickinson's estimates of
the contributions of the individual factors to
climate sensitivity are shown in Figure 3-6.
The largest positive feedback is from changes
111-16
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Chapter HI: Climate Change Processes
in the amount and distribution of water vapor.
Substantial positive feedback may also be
contributed by changes in sea ice and surface
albedo and clouds, although the uncertainty
range includes the possibility that clouds
contribute significant negative feedback. The
differences in the strength of these feedbacks
between models is the result of different
parameterizations of the relevant processes as
well as differences in the control (lxCO2)
simulation (Cess and Potter, 1988). Even
though the exact value of AT2X is not known,
we can study the potential impact of climate
warming caused by greenhouse gases by
choosing scenarios that span the range of
theoretical calculations. Thus, we adopt 2-4°C
as a putative one-standard deviation (la)
confidence interval about the center of the
range proposed by the National Academy of
Sciences, and the range proposed by Dickinson
(1.5-5.5°C) as 2a "bounds for subsequent
modeling (see CHAPTER VI). When the
biogeochemical feedbacks discussed above are
also considered, a AT2X as great as 8-10°C
cannot be ruled out (Lashof, 1989).
THE RATE OF CLIMATE CHANGE
The Earth's surface does not
immediately come to an equilibrium following
an increase in radiative forcing. Excess
radiation captured by the Earth heats the land
surface, the ocean, and the atmosphere. The
effective heat capacity of the oceanic part of
the climate system, in particular, is enormous.
The result is that the warming realized in any
given year may be substantially less than the
warming that would occur in equilibrium if
greenhouse gas concentrations were fixed at
their levels in that year. Hundreds of years
would be required for the entire ocean to
equilibrate with the atmosphere, but only the
surface layer (about 100 m) is well mixed by
winds and therefore tightly linked to climate in
the short term. The heat capacity of the
surface layer is about one-fortieth that of the
entire ocean, and this layer by itself would
equilibrate with a response time (the time
required to reach 1 - 1/e, or 63%, of the
equilibrium response) of 2-15 years, depending
on the climate sensitivity and assumed mixed
layer depth. The equilibration time is longer
if the climate sensitivity is greater because the
feedback processes that increase climate
sensitivity respond to the realized changes in
climate, not to the initial change in forcing
(Hansen et al., 1985). When the transfer of
heat from the mixed layer into the deep ocean
is considered, it is impossible to characterize
the oceanic response with a single time
constant (Harvey and Schneider, 1985; Wigley
and Schlesinger, 1985).
While the main features of ocean
circulation and mixing, and therefore the rate
of heat and carbon uptake, have been
identified, they are not well defined or
modeled on a global scale. The theory and
modeling of ocean circulation are currently
limited by the inadequacy of the database
(Woods, 1985). The development of ocean
general circulation models (OGCMs) lags
significantly behind their atmospheric
counterparts, mainly because it is difficult and
expensive to obtain the necessary data with
sufficient temporal and spatial coverage,
because fewer scientists have addressed this
problem and because a large amount of
computer power is needed to resolve the
necessary time and space scales. Due to these
problems it may be a decade or more before
OGCMs reach the state of development
achieved by current atmospheric GCMs.
Lacking well-tested OGCMs, the main
tools used so far to investigate ocean heat
uptake have been highly parameterized
models, very similar to those used for carbon
(see CHAPTER II). These models are
calibrated with data on the penetration of
tracers such as tritium and carbon-14 (14C)
produced by atmospheric nuclear weapons
tests during the 1950s and early '60s and/or
with the steady-state profiles of various ocean
parameters, such as natural 14C and
temperature. The simplest models that yield
a plausible time-dependence for heat (and
carbon) uptake lump the entire ocean into two
compartments: A well-mixed surface layer and
a deep ocean compartment in which mixing is
parameterized as a diffusive process (Box-
Diffusion or BD model). This approach was
introduced by Oeschger et al. (1975) for
modeling carbon uptake and has been applied
to ocean heat absorption by Hansen et al.
(1985) and Wigley and Schlesinger (1985),
among others. A more elaborate version of
this model, which includes a representation of
upwelling implicitly balanced by high-latitude
bottom-water formation (Upwellmg-Diffusion
ra-n
-------
Policy Options for Stabilizing Global Climate
or UD model), has been used by Hoffert et al.
(1980), Harvey and Schneider (1985), and
Wigley and Raper (1987). The addition of an
upwefling term allows the observed mean
thermal structure of the ocean to be
approximated (Hoffert et al., 1980), but given
the highly parameterized nature of both of
these models, there is no convincing reason to
favor one approach over the other for
modeling small perturbations to heat flows.
The response time, r, of BD models is
proportional to /c(AT2x)2, where K is the
diffusion constant used to characterize deep
ocean mixing (Hansen et al., 1985; Wigley and
Schlesinger, 1985). Data on the penetration of
tracers into the ocean suggests that /c = 1-2
cm2/s (Hansen et al., 1985). Hoffert and
Flannery (1985) have argued that mixing rates
derived from tracers may be too high for heat
because mixing rates are highest along
constant density surfaces, which are nearly
parallel to ocean isotherms. On the other
hand, in a preliminary coupled GCM-OGCM
run, Bryan and Manabe (1985) found that heat
was taken up more rapidly than a passive
tracer because of reduced upward heat
convection. Using a range of 0.5-2 cm2/s for K
and the la range for AT^ given above (2-4°C)
in the equation derived by Wigley and
Schlesinger (with their recommended values
for other parameters) yields T = 6-95 years.2
Correspondingly, the warming expected by
now, based on past increases in greenhouse
gases and assuming no other climate forcings,
is roughly 40-80% of the equilibrium warming
(Wigley and Schlesinger, 1985). In other
words, even if greenhouse gas concentrations
could be fixed at today's levels, the Earth
would still be subject to significant climate
change that has yet to materialize. The large
uncertainty surrounding ocean heat uptake,
combined with uncertainty about potential
climate forcings other than those from
greenhouse gases, also implies that it is not
possible to obtain a useful constraint on AT^
from the observed temperature record as
discussed above (see also Hansen et al., 1985;
Wigley and Schlesinger, 1985).
Experiments with UD models
demonstrate the importance of the bottom-
water formation process for the rate of ocean
heat uptake. The impact of using an UD
ocean model rather than a BD ocean model is
that the heat that diffuses into the thermocline
is pushed back toward the mixed layer, which
decreases the effective heat capacity of the
ocean and the time constant for tropospheric
temperature adjustment, assuming that the
upwelling rate and the temperature at which
bottom water is formed do not change. If the
initial temperature of the downwelling water is
assumed to warm as much as the mixed layer,
however, then a UD model actually takes up
more heat in the ocean than a BD model,
leading to a larger disequilibrium between a
given radiative forcing scenario and the
expected realized warming. While there are
reasons to think that the temperature of
Antarctic bottom water will not increase as
climate changes, the temperature of north
Atlantic deep water could increase or decrease
(Harvey and Schneider, 1985). Furthermore,
there is no reason to assume that the rate of
bottom-water formation will remain constant
as climate changes. The tropospheric
temperature could even overshoot equilibrium
if the average bottom-water temperature cools
as the surface temperature warms or if the
upwelling rate increases with warming (Harvey
and Schneider, 1985). One must also
recognize the potential for sudden
reorganizations of the ocean-atmosphere
circulation system as suggested by Broecker
(1987), which could lead to discontinuous, and
perhaps unpredictable, changes in climate that
cannot be included in the models used in this
report.
Another major limitation of the BD and
UD models generally used to analyze the
climate transient problem is that they have
limited or no spatial resolution (at best
hemispheric, land-sea) and thus cannot
consider spatial heterogeneity in either the
magnitude or rate of climate change. Work at
the NASA Goddard Institute for Space Studies
(Hansen et al., 1988) has produced one of the
few three-dimensional, time-dependent
analyses of climate change that have been
published to date. This study employed three
simple, but reasonably realistic, scenarios of
future greenhouse gas concentrations and
volcanic eruptions. The results suggest that
the areas where wanning is initially most
prominent relative to interannual variability
are not necessarily those where the
equilibrium wanning is greatest. For example,
low-latitude ocean regions warm quickly
111-18
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Chapter III: Climate Change Processes
because ocean heat uptake is limited by strong
stratification in these regions. Warming is
also prominent in high-latitude ocean areas
where a large equilibrium warming is expected
due to increased thermal inertia as sea ice
melts. Global average temperatures are used
in this report as an indicator of the rate and
magnitude of global change but, as these
results emphasize, it must be recognized that
major variations among regions are a certainty.
CONCLUSION
The changing composition of the
atmosphere will in turn drive significant
changes in the Earth's climate. These changes
may have already begun, but because of the
uncertainties in temperature data sets and the
complexity of the interaction between climate
sensitivity and the transient response,
definitive predictions are subject to a good
deal of controversy at this time. Whether next
year is warmer or cooler than this year, however,
has no direct bearing on how the greenhouse
effect should be viewed. Internal fluctuations
or countervailing forcings may temporarily
mask the warming due to increasing
concentrations of greenhouse gases or make
the climate warmer than expected solely from
greenhouse warming. Therefore, to derive our
estimates of the magnitude and rate of change
that can be expected during the next century
we must continue to rely on model
calculations, which indicate that by early in the
next century the Earth could be warmer than
at any time during the last million years or
more, and that the rate of change could be
unprecedented in Earth history.
NOTES
1. The thermocline starts at the base of the
mixed layer and extends to a depth of about
1000 m. It is characterized by a rapid decrease
in temperature with increasing depth, which
inhibits mixing in the water column because
the colder deeper water is denser than the
warmer overlying water.
2. Ii is important to note that the actual
response does not correspond to exponential
decay with a single time constant, so that while
r gives the time required for one e-folding
and is a useful measure, it would not apply to
subsequent e-foldings (the time constant would
be substantially longer) and must be
interpreted with care.
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ra-23
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CHAPTER IV
HUMAN ACTIVITIES AFFECTING
TRACE GASES AND CLIMATE
FINDINGS
Various human activities affect the
Earth's climate by altering the level of trace
gases in the atmosphere. These activities
include fossil-fuel consumption; industrial
processes; land-use change, particularly
deforestation; and agricultural practices such
as waste burning, fertilizer use, rice
production, and animal husbandry. Economic
development and population growth are key
factors affecting the level of each activity.
• Population levels and growth rates have
increased tremendously over the last 200 years.
Between 1650 and 1980, the global population
doubling time shrank from 200 to 35 years. At
the beginning of this century, global
population was about 1.6 billion; in 1987, it
reached 5 billion. By the early part of the next
century total population is likely to reach 8
billion. The rate of population increase is
most acute in the developing regions,
particularly Africa and Asia where annual
rates of growth exceed 2%.
• Fossil-fuel combustion emits carbon
dioxide (CO2) and other radiatively important
gases and is the primary cause of the buildup
of greenhouse gases in the atmosphere.
Commercial energy consumption currently
accounts for more than 5 of the 6-8 billion
tons of carbon as CO2 emitted to the
atmosphere annually from anthropogenic
sources (i.e., as a result of human activities).
Between 1950 and 1986, annual global fossil-
fuel consumption grew 3.6-fold and annual
CO2 emissions grew 3.4-fold.
• Emissions of other trace gases due to
fossil-fuel consumption are more uncertain.
Approximately 0-2 million tons nitrogen as
nitrous oxide, 20 million tons nitrogen as
nitrogen oxides, and 180 million tons carbon
as carbon monoxide are emitted annually from
fossil-fuel combustion. Leaking and venting of
natural gas contributes approximately 20-50
million tons methane (CH4) annually to the
atmosphere, and coal mining contributes
approximately 25-45 million tons CH4.
• Three significant non-energy sources of
greenhouse gases are associated with industrial
activity: production and use of chlorofluoro-
carbons (CFCs), halons, and chlorocarbons;
waste disposal in landfills; and cement
manufacture. Production of CFC-11 and CFC-
12 grew 4.7-fold between 1960 and 1985.
Consumption of major CFCs and halons
reached nearly one million tons in 1985. An
international agreement (the Montreal
Protocol), however, to reduce future
production of certain CFCs and limit growth
in the production of certain halons, came into
force on January 1, 1989. The London
Amendments, negotiated in June 1990,
strengthen the Protocol by completely phasing-
out CFCs, halons, carbon tetrachloride, methyl
chloroform, and encouraging limits on HCFCs.
Anaerobic decay of organic wastes in landfills
currently contributes approximately 30-70
million tons of CH4 to the atmosphere
annually. Cement production, which has
increased sevenfold since the 1950s,
contributed approximately 134 million tons
carbon as CO2 to the atmosphere in 1985.
• Land-use change has resulted in
substantial emissions of greenhouse gases to
the atmosphere. Since 1850, approximately
15% of the world's forests have been
converted to agricultural and other land uses.
Currently, deforestation contributes between
one-tenth and one-third of the total
anthropogenic CO2 emissions to the
atmosphere, i.e., between 0.4 and 2.6 billion
tons of carbon. Between one-quarter and one-
half of the world's swamps and marshes also
have been destroyed by man. Wetlands
currently contribute approximately one-fifth of
the total CH4 emissions to the atmosphere;
continued changes to wetlands could
significantly alter the global CH4 budget.
Biomass burning, in addition to contributing
to atmospheric concentrations of CO2
contributes approximately 10-20% of total
annual CH4 emissions, 5-15% of the nitrous
oxide emissions, 10-35% of the nitrogen oxide
emissions, and 20-40% of the carbon
monoxide emissions.
IV-1
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Policy Options for Stabilizing Global Climate
• Three agricultural activities directly
result in major contributions to atmospheric
emissions of greenhouse gases: animal
husbandry, rice cultivation, and nitrogenous
fertilizer use. Domestic animals, which
produce CH4 as a by-product of enteric
fermentation, currently contribute
approximately 65-85 million tons of CH4
annually. Over the past several decades,
domestic animal populations have grown by up
to 2% annually. Methane is also produced by
anaerobic decomposition of organic material
in rice paddies. Currently, about one-fifth of
annual CH4 emissions, or between 60 and 170
million tons, comes from rice cultivation. Rice
production has grown rapidly since the mid-
1900s due to increases in crop acreage, double
cropping, and higher yields. Between 1950
and 1984 rice production increased nearly
threefold, and harvested area grew by about
70%. Use of nitrogenous fertilizers results in
nitrous oxide emissions, either directly from
the soil, or indirectly from groundwater.
Global use of organic and inorganic fertilizers
has risen markedly, and nitrogen-based
fertilizers increased their market share of total
inorganic fertilizer consumption from 28% in
1950 to 64% in 1981. Nitrogenous fertilizer
use may contribute between 0.14 and 2.4
million tons nitrogen as nitrous oxide per year
to the atmosphere.
• In addition to the human activities that
directly affect trace gas emissions, future
concentrations of greenhouse gases will be
influenced by feedback processes resulting
from humans living in a world that has
undergone climate change. Two potential
feedbacks of increased temperatures, which
may counteract each other to some extent, are
increased energy demand for air conditioning
in the summer, and decreased energy demand
for heating in the winter.
IV-2
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Chapter IV: Human Activities
INTRODUCTION
As discussed in Chapter III, the Earth's
climate has been in a constant state of change
throughout geologic time due to natural
perturbations in the global geobiosphere.
However, various human activities have the
potential to cause future global warming over
a relatively short amount of time. These
activities, which affect the Earth's climate by
altering the concentrations of trace gases in
the atmosphere, include energy consumption,
particularly fossil-fuel consumption; industrial
processes (production and use of
chlorofluorocarbons, halons, and
chlorocarbons, landfilling of wastes, and
cement manufacture); changes in land-use
patterns, particularly deforestation and
biomass burning; and agricultural practices
(waste burning, animal husbandry, rice
cultivation, and nitrogenous fertilizer use).
Population growth is an important underlying
factor affecting the level of growth in each
activity.
This chapter describes how the human
activities listed above contribute to
atmospheric change, the current pattern of
each activity, and how levels of each activity
have changed since the early part of this
century. Figure 4-1 illustrates the regional
contributions to the increase in greenhouse
forcing that occurred in the 1980s. Almost
50% of the forcing is attributable to activities
in the United States, the USSR, and the
European Economic Community (EEC). As
background to the discussion of trace-gas-
producing activities, we first provide an
overview of population trends. This historical
perspective is meant to serve as a framework
for the discussion of possible future scenarios
of trace gas emissions in Chapter VI.
HISTORICAL OVERVIEW OF
POPULATION TRENDS
One of the major factors affecting
trends in greenhouse gas emissions is the
increase in human population. As population
levels rise, increasing pressures are placed on
the environment as the larger population
strives to feed and clothe itself and achieve a
higher standard of living. Without changes in
the methods used to meet people's needs,
higher population levels invariably lead to
increased emissions of greenhouse gases.
Global Population Trends
Not only has global population grown
rapidly over the past few centuries, but the
rate of growth has also increased (see Figure
4-2). World population in the year 1 A.D.,
approximately 0.25 billion, doubled by 1650
(Wagner, 1971). By 1850 (i.e., 200 years'later),
global population had roughly doubled again
to 1.1 billion. The global population doubling
time has continued to decline - 80 years later,
in 1930, world population was 2 billion. By
1975 global population had reached 4 billion,
and according to some estimates the
population will double once again within 35
years (world population reached 5 billion in
1987). Despite recent declines in the world's
annual population growth rate (IIED and
WRI, 1987), world population is expected to
continue to grow rapidly. Several studies
estimate that world population will exceed 8
billion by 2025 (Zachariah and Vu, 1988; U.S.
Bureau of the Census, 1987). Such rapid
population growth can be expected to result in
increasing pressure on the global environment,
particularly as the burgeoning human
population strives to improve its living
standards through economic growth.
Population Trends by Region
The rapid population growth in recent
decades has not occurred uniformly around the
world (see Figure 4-2). Between 1950 and
1985, population in developed countries
increased by 41%, compared to 117% in
developing countries (IIED and WRI, 1987).
Recent trends indicate these differences will
continue: annual growth rates in the developed
countries are generally less than 1%, while
many developing countries continue to
experience rates of growth between 2 and 3%
(see Table 4-1). These higher growth rates in
the 20th century in developing countries have
been due primarily to the combined effects of
declining death rates and continued high birth
rates. Unfortunately, the countries that are
experiencing the most explosive population
growth rates are often the ones likely to suffer
the most severe environmental stresses due to
climate change and the ones least able to
adapt to or accommodate these effects.
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Policy Options for Stabilizing Global Climate
FIGURE 4-1
Regional Contribution to Greenhouse Forcing
REGIONAL CONTRIBUTION TO GREENHOUSE FORCING
1980s
(Percent)
Rest of the World (36%)
United States (21%)
Japan (4%)
USSR (12%)
India (4%)
Brazil (5%)
EEC (11%)
China (7%)
Figure 4-1. Estimated regional contribution to greenhouse forcing for the 1980s, based upon regional
shares of current levels of human activities that contribute to greenhouse gas emissions. (Sources:
U.S. EPA, 1988; United Nations, 1987; U.S. BOM, 1985; IRRI, 1986; FAO, 1986a, 1987; Bolle et al.,
1986; Rotty, 1987; Lerner et al., 1988; Seiler, 1984; WMO, 1985; Hansen et al., 1988; Houghton et
al., 1987; Matthews and Fung, 1987.)
rv-4
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Chapter IV: Human Activities
FIGURE 4-2
REGIONAL POPULATION GROWTH
1750-1985
(Billions)
4 -
3 -
5
ffl
2 \-
0
1750
North America
& Oceania
Latin America
Africa
Europe & USSR
Asia
1800 1850 1900
Year
1950 1985
Figure 4-2. Since about 1850, global population has grown at increasingly rapid rates. In 1850, the
population doubling time was approximately 200 years; by 1975, the doubling time had declined to
approximately 45 years. Most of the growth has occurred in the developing world, particularly Asia.
(Sources: Matras, 1973; Hoffman, 1987.)
IV-5
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Policy Options for Stabilizing Global Climate
TABLE 4-1
Regional Demographic Indicators
Region
North America
Europe
East Asia
Oceania
Caribbean
Southeastern Asia
Latin America
Southern Asia
Western Asia
Africa
Total Fertility3
1980-85
1.83
1.88
2.34
2.65
3.34
4.11
4.17
4.72
5.22
6.34
Infant Mortality6
1980-85
11
15
36
31
65
73
61
115
81
112
Annual Population
Growth Rate
1980-85
(percent)
0.90
0.30
1.22
1.51
1.53
2.05
2.34
2.14
2.79
2.92
World Average 3.52 60 1.67
a The total fertility rate is the average number of children that a woman bears in a lifetime.
b The infant mortality rate is the average number of infant deaths (deaths before the first birthday)
per 1000 live births.
Source: Adapted from IIED and WRI, 1987.
IV-6
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Chapter IV: Human Activities
Industrialized Countries
Population growth rates in the
industrialized countries are substantially lower
than in the developing world. For example,
while most developing countries contend with
growth rates that will double their populations
within 20-40 years, current growth rates in
North America and Europe will lead to a
doubling within about 100 years and 250 years,
respectively (IIED and WRI, 1987). This
trend toward lower growth rates is due to
many complex economic and social factors,
including the changing role of women in the
labor force, the higher economic costs of child
rearing, and the reduced need for children as
a labor pool.
Developing Countries
The highest rates of population growth
are in the developing countries: from 1950 to
1985, developing countries increased their
share of the world's population from 66.8% to
75.6% (IIED and WRI, 1987). During this
time Asia's population grew from 1.3 to 2.7
billion, Africa's from 224 to 555 million, and
Latin America from 165 to 405 million. Key
trends are summarized below.
Africa. Africa currently has the highest
fertility rates and population growth rates in
the world. Its growth rate has increased
recently: between 1955 and 1985, Africa's
average annual growth rate increased from
2.3% to 2.9%. The total fertility rate (i.e.,
average number of children that a woman
bears in a lifetime) is six or higher in 38
African countries, most of which have
experienced declining infant mortality rates
(infant deaths per thousand live births) over
the past 20 years (IIED and WRI, 1987). For
example, in Kenya, where the total fertility
rate is 7.8, the infant mortality rate fell from
112 to 91 between 1965 and 1985. Between
1965 and 1985, the crude birth rate (births per
thousand population) for Kenya grew by 4.7%,
while the crude death rate fell by 37.7%. The
average annual growth rate reached 4.1% in
the 1980s (World Bank, 1987). The United
Nations expects the African population to
continue to grow rapidly, with the average
annual growth rate increasing to 3% in 1990
(United Nations, 1986).
Asia. From 1850 to 1950, Asia
experienced the largest increase in population
in the world (Ehrlich and Ehrlich, 1972).
Rates of growth have continued at high levels
-- annual growth rates since 1960 have
exceeded 2%. These rates are likely to remain
high in several Asian countries in future years
(United Nations, 1986). For example, China
currently is the most populous country in the
world, with 22% of the world's total
population (Ignatius, 1988). Although its
strong population policy of one child per
family helped to halve the 2% annual growth
rates of the 1960s, growth rates have recently
turned upward, approaching 1.5% annually.
This trend of growth could lead to population
levels in China in excess of 1.7 billion by 2025.
India's population has also been rapidly
expanding. It is the second most populous
country in the world (United Nations, 1986),
with 765 million people as of 1985. India's
rate of growth has been relatively high this
century, although it has declined in recent
years; in 1960 its annual rate of growth was
2.3%, but has since dropped to 1.7% (IIED
and WRI, 1987). Despite this recent decline,
its population is expected to grow for many
years; for example, the United Nations
estimates that India's population will be over
1.2 billion by 2025 (United Nations, 1986).
Latin America. Latin America currently
has one of the highest population growth rates
in the world: from 1980 to 1985, the annual
rate of growth averaged 2.3% for the region
(IIED and WRI, 1987), although these rates of
growth varied substantially between countries.
Argentina, Chile, and Uruguay have the lowest
growth within Latin America, while countries
such as Bolivia, Ecuador, El Salvador,
Guatemala, Honduras, Nicaragua, Paraguay,
and Venezuela have annual population growth
rates that exceed 2.5%. Fertility rates have
been declining throughout the region due to
industrialization, urbanization, rising incomes,
and official population policies, although one
source estimates that Latin America's share of
world population will nonetheless increase
from 8.4 to 9.5% between 1985 and 2025
(IIED and WRI, 1987). The two population
projection sources used in this report (U.S.
Bureau of the Census, 1987; Zachariah and
Vu, 1988; see CHAPTER VI) project that by
IV-7
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Policy Options for Stabilizing Global Climate
2025, Latin America's share of world
population will grow to 9.1% and 8.7%,
respectively.
ENERGY CONSUMPTION
The major human activity affecting trace
gas emissions is the consumption of energy,
particularly energy from carbon-based fossil
fuels. As discussed in Chapter II, global
carbon dioxide (CO2) emissions from
anthropogenic sources currently range from 6
to 8 petagrams (Pg) of carbon (C) annually,
with commercial energy consumption
accounting for approximately 65-85% of this
total.1 Non-commercial (biomass) energy
consumption accounts for approximately 7%.
Energy consumption and production also
produce substantial amounts of other
greenhouse gases, including carbon monoxide
(CO), methane (CH4), nitrogen oxides (NOX,
i.e., nitric oxide [NO] and nitrogen dioxide
[NO2]), and nitrous oxide (N2O)/
This section explores the role of energy
consumption in climate change. We first
discuss the world's increasing reliance on fossil
fuels, the roles that fossil-fuel production (e.g.,
coal mining and oil drilling) and fossil-fuel
combustion play in the emission of trace gases
to the atmosphere, and the implications of the
continuation of current energy consumption
patterns on future global warming.
History of Fossil-Fuel Use
Prior to the discovery and development
of fossil fuels (coal, oil, and natural gas),
people relied on readily-available energy
resources such as wood and other forms of
biomass (i.e., living matter), as well as water
and wind, to satisfy their basic energy needs.
Since the beginning of the 19th century, fossil
fuels have played an increasingly important
role in the world economy, particularly for
developed countries, by providing the energy
required for industrial development, residential
and commercial heating, cooling, lighting, and
transportation services. Fossil fuels now
provide about 85% of the world's total energy
requirements. This dependence on fossil fuels
is greatest in industrialized countries, where
over 95% of all energy needs are provided by
fossil fuels, compared with about 55% in
developing countries (Hall et al., 1982).3
Global consumption of fossil fuels has
increased rapidly over the past century as
human populations and their economic
activities have grown. Since 1950, global
primary energy consumption has increased
nearly fourfold (see Figure 4-3), with energy
consumption per capita approximately
doubling. In 1985, 42% of global energy
demand was supplied by liquid fossil fuels
(primarily petroleum); solid fuels (coal)
supplied 31%, natural gas, 22%, and other
fuels combined accounted for 5% of the
market share.4 These relative proportions
have changed considerably since 1950, when
coal supplied 59% of total commercial energy
requirements, liquids, 30%, natural gas, 9%,
and other fuels, 2%.
The increase in fossil-fuel consumption
over the last century has caused a substantial
increase in the amount of CO2 emitted to the
atmosphere. Carbon dioxide emissions from
fossil fuels grew from less than 0.1 Pg C
annually in the mid-nineteenth century, to
about 5.4 Pg C in 1986 (see Figure 4-4).5
This rate of increase is about 3.6% per year
and is the major reason why atmospheric CO2
concentrations increased from about 290 ppm
in 1860 to about 348 ppm as of 1987 (Rotty,
1987). Currently fossil-fuel combustion also
contributes approximately 0-2 teragrams of
nitrogen (Tg N) as N2O, 20 Tg N as NOX and
180 Tg C as CO to the atmosphere each year.
In recent decades there has also been a
significant shift in global energy-use patterns.
In 1950, countries belonging to the
Organization for Economic Cooperation and
Development (OECD) consumed about three-
fourths of all commercial energy supplies, the
centrally-planned economies of Europe and
Asia, 19%, and developing countries, 6%
(United Nations, 1976, 1983).6 By 1985
OECD countries consumed just over one-half
of all commercial energy globally, while the
European and Asian centrally-planned
economies and the developing countries had
increased their relative shares to 32% and
15%, respectively (see Figure 4-5). Between
1950 and 1985, commercial energy use per
capita in the OECD grew from 93 to 189
gigajoules per capita (GJ/cap) (103%), in
centrally-planned economies from 16 to 59
GJ/cap (269%), and in the developing
countries from 3 to 18 GJ/cap (500%).7 The
IV-8
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Chapter IV: Human Activities
FIGURE 4-3
GLOBAL ENERGY DEMAND BY TYPE *
1950- 1985
(Exajoules/Year)
300
250 -
Other
Natural Gas
Liquid Fuels
Solid Fuels
1950 1955 1960 1965 1970 1975 1980 1985
Year
* Data Is for commercial energy only; blomaes Is not Included
Figure 4-3. Global demand for fossil fuels has more than tripled since 1950. Ibday, about 85% of
the world's energy needs are met by fossil fuels. (Sources: United Nations, 1976,1982,1983,1987.)
IV-9
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Policy Options for Stabilizing Global Climate
FIGURE 4-4
C02 EMISSIONS DUE TO FOSSIL FUEL CONSUMPTION
1860-1985
(Petagrams Carbon/Year)
6
5 -
ra
o
o
o
CO
E
D>
a
**
o
Q.
4 -
3 -
Natural Gas
Coal
1860
1985
Figure 4-4. Carbon dioxide emissions from fossil-fuel consumption have grown from less than 0.1 Pg
C in the mid-1850s to approximately 5.4 Pg C in 1986. This is the major reason why the atmospheric
concentration of CO2 increased from approximately 290 ppm in 1860 to approximately 348 ppm in
1987. (Sources: Rotty and Masters, 1985; Rotty, 1987, pers. communication.)
IV-10
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Chapter IV: Human Activities
FIGURE 4-5
GLOBAL COMMERCIAL ENERGY DEMAND BY REGION
(Exajoules/Year)
350
300 -
250 -
S 200
x
O
5 150
UJ
100 -
50
Developing
Centrally
Planned
OECD
1950 1955 1960 1965 1970 1975 1980 1985
Year
Figure 4-5. Primary energy use by region. Between 1950 and 1985, the share of global energy demand
for the OECD declined, while that for the centrally-planned and developing economies increased.
(Sources: United Nations, 1982, 1987.)
IV-11
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Policy Options for Stabilizing Global Climate
proportion of energy consumed by the OECD
is expected to decline further as the developing
world continues to experience more rapid
population growth and economic development
and, thus, significantly expands its energy
requirements (see CHAPTER VI).
Current Energy-Use Patterns and Greenhouse
Gas Emissions
The allocation of energy consumption
among end-use sectors varies considerably
from one region to the next. Figure 4-6
summarizes 1985 end-use energy demand (for
both commercial and non-commercial, or
biomass, fuels) by sector for the OECD
countries, the centrally-planned economies of
Asia and Europe (including China and the
USSR), and the developing countries.
Whereas the OECD split is approximately
one-third industrial, one-third transportation,
and one-thirdresidential/commercial, centrally-
planned economies of Asia and Europe
consume more than 50% of their energy in the
industrial sector.
These energy consumption patterns
partly reflect the basic differences in the
structure of economic activity at the current
stage of each region's economic development.
The centrally-planned economies and the
developing countries devote a greater share of
their energy requirements to the industrial
sector because they are at a stage of economic
development where energy-intensive basic
industries account for a large share of total
output, while infrastructure in the
transportation and commercial sectors has not
been extensively developed. In the OECD,
transportation consumes a larger share of total
energy compared with other regions, primarily
because of the large number of automobiles in
the OECD. For example, in the U.S. there
are 550 cars and light trucks/1000 people,
compared with 60 cars and light trucks/1000
people in the USSR, and 6 cars and light
trucks/1000 people in China. Also, biomass is
very important to the residential energy
requirements of the developing economies
compared with those of industrialized
countries; the industrial sector is the major
consumer of fossil fuels in most developing
countries.
Emissions by Sector
The differences among regions in terms
of the share of energy consumed by each
sector and the types of applications for which
the energy within each sector is used can have
a major impact on the amount and types of
greenhouse gases emitted. This section
discusses how emissions of greenhouse gases
vary as a result of differences in type of fossil
energy consumed and combustion technology
used.
Electric Utility Sector. Energy is
increasingly desired in the form of electricity.
The amount of greenhouse gases produced
from electricity generation is a function of the
type of primary energy used to produce the
electricity and the production technology. For
example, nuclear, hydroelectric, or solar
primary energy sources emit little or no
greenhouse gases, while fossil fuels generate
substantial quantities of CO2, as well as other
gases (see Table 4-2). The amount of
greenhouse gas emissions varies according to
the type of fossil fuel used because of inherent
differences in the chemical structure of the
fuels. Additionally, the level of emissions
varies as a function of production efficiency.
For example:
• Coal-fired powerplants produce about
two to three times as much CO2 as natural
gas-fired units per unit of electricity generated
(330 kg CO2/GJ for a pulverized coal wall-
fired unit compared with 120 kg CO2/GJ for a
combined cycle gas-fired unit). Oil-fired units
produce more CO2 than natural gas units
produce, but less CO2 than coal-fired units
produce. Within fuel types the emission levels
may vary. For example, when natural gas is
used as the fuel, combined cycle units produce
about 40% lower CO2 emissions than simple
cycle units (see CHAPTER V) because of the
greater generating efficiency obtained through
the use of these technologies. Similarly, coal-
fired fluidized bed units produce less NOX
emissions than do coal-fired cyclone units
because the higher operating temperatures
typical of cyclone-units are more conducive to
NOX formation.
rv-12
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Chapter IV: Human Activities
FIGURE 4-6
1985 SECTORAL ENERGY DEMAND BY REGION
COMMERCIAL AND NON-COMMERCIAL FUELS
(Exajoules)
OECD
42.6
33.4
CENTRALLY PLANNED
18.2
DEVELOPING
19.0 ^rVV^^^ 27.0
8.4
10.0
38.7
Residential/Commercial
Industrial
Transportation
Figure 4-6. End-use energy demand by sector for three global regions. While energy demand in the
OECD countries is split almost equally among the three sectors, over 50% of the energy in the
centrally-planned countries is consumed by the industrial sector, and almost 50% of the energy in the
developing countries is consumed by the residential/commercial sector. (Sources: Sathaye et al., 1988;
Mintzer, 1988.)
IV-13
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Policy Options for Stabilizing Global Climate
TABLE 4-2
Emission Rate Differences by Sector
(grams per gigajoule)*
Source
Efficiency
CO;
CO
N,O
NO,
Electric Utility (g/GJ delivered electricity)
Gas Turbine Comb. Cycle
Gas Turbine Simp. Cycle
Residual Oil Boilers
Coal - F. Bed Comb. Cycle
Coal - PC Wall Fired
Coal - PC Cyclone
Coal - Integrated Gas
42.0
26.4
32.4
35.0
31.3
31.3
27.3
Industrial (g/GJ delivered steam for boilers; energy output
Boilers
Coal-Fired
Residual Oil-Fired
Natural Gas-Fired
Kilns - Coal
Dryer - Natural Gas
Dryer - Oil
Dryer - Coal
Residential/Commercial (g/GJ energy
Wood Stoves
Coal Stoves
Distillate Oil Furnaces
Gas Heaters
Wood Boilers
Gas Boilers
Residual Oil Boilers
Coal Boilers
Transportation (g/GJ energy input)
Rail
Jet Aircraft
Ships
Light Duty Gasoline Vehicle
Light Duty Diesel Vehicle
Light Duty Compressed
N. Gas Vehicle
SO
85
85
65-75
30-65
30-65
30-65
output)
50
50
75
70
67.5
80.9
84.9
75.9
NA
NA
NA
NA
NA
NA
120,300
191,400
230,000
290,000
330,000
330,000
253,600
for others)
130,000
88,000
57,000
300,000-350,000
75,000-170,000
100,000-240,000
155,000-340,000
[150,000]
198,000
111,000
101,000
[138,000]
61,800
86,000
135,000
69,900
72,800
70,000
54,900
73,750
50,200
70
110
43
NA
42
42
222
110
17
18
75
10
15
170
17,600
3,400
17
13
280
10.6
19
244
570
120
320
10,400
340
4
13
20
2.2
1.8
2.0
2.0
NA
2.9
3.3
1.5
1
1
1
1
70
NA
7
1
21
1.4
1.8
13
13
2
20
36
2
120
20
30
44
40
45
45
51
18
16
3.5
2
NA
NA
NA
NA
NA
NA
NA
6
2.7
14
16
NA
NA
NA
0.5
20
7
400
640
590
690
1,400
2,600
760
390
180
71
500
52
160
215
190
170
65
61
47
53
183
295
1,640
290
830
400
300
140
* All emission rates are based on total molecular weight.
NA = Not Available
[ ] = No Net CO2 if based on sustainable yield
Source: Radian Corporation, 1990; except N2O data, which is based on unpublished EPA data. N2O emission
coefficients are highly uncertain and currently undergoing further testing and review.
rv-14
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Chapter IV: Human Activities
Industrial Sector. The industrial sector
includes mining, construction, and
manufacturing, which are some of the most
energy-intensive economic activities. Energy
consumption in this sector can be subdivided
into four categories:
• Boilers - Boilers produce steam for
many different purposes, including machine
drive, on-site electricity production, high-
pressure cleaning, and process requirements.
Virtually any fuel can be consumed to produce
steam (e.g., fossil fuels, biomass, hazardous
wastes, by-product wastes, etc.). In the U.S.,
boilers consume about 30% of all industrial
energy.
• Process Heat - Many industrial
processes that do not use steam require the
use of some form of heat during production.
Examples of process heat applications include
ovens, furnaces, dryers, melters, and kilns.
The degree of flexibility in fuel choice a
consumer may have depends on the process
heat application ~ some applications may use
technologies or production processes that
require a particular fuel.8 Process heat
applications consume about 40% of the energy
in the U.S. industrial sector.
• Feedstocks -- Fuels may be used as a raw
material for the production process. Examples
of such applications include the conversion of
metallurgical coal to coke for use in the
manufacture of steel, natural gas for fertilizer
production, and petroleum for asphalt. It is
usually very difficult to switch to alternative
fuels with these applications. In the U.S.,
feedstocks consume about 15% of industrial
energy.
• Other - This category consists primarily
of industrial activities requiring electricity, e.g.,
motors and lighting. These applications
account for 15% of all energy consumed by
U.S. industry.
The amount of greenhouse gas
emissions generated from industrial energy
consumption is a function of fuel type and the
process in which it is consumed (see Table 4-2
for emissions from selected industrial
applications).
Residential and Commercial Sectors. In
the residential and commercial sectors the
main end-use applications for energy are
heating, cooling, cooking, and lighting. The
form and amount of energy used to meet these
needs varies, as summarized in Table 4-3 for
the U.S. and South/Southeast Asia. In
developing countries, most of the energy in
these two sectors is consumed for cooking
purposes, with consumers relying on biomass
or kerosene for fuel. In industrialized
countries, however, space heating and water
heating consume the most energy, which is
supplied primarily by fossil fuels and, to some
extent, electricity; gas and electricity are the
primary energy forms for cooking in
industrialized countries. Because of the wide
variety of end-use applications, types of energy
consumed, and conversion efficiencies in the
residential and commercial sectors it is
difficult to generalize about emission trends in
these sectors; for illustrative purposes,
emission coefficients for several major
applications in industrialized countries are
listed in Table 4-2.
Transportation Sector. As consumers
become wealthier, the absolute quantity and
share of energy used in the transportation
sector increases. For example, as discussed
earlier, in many developing countries, such as
China, the transportation sector consumes a
much smaller portion of the country's energy
requirements than the portion consumed by
this sector in industrialized countries, such as
the United States. Energy requirements in the
transportation sector are typically met with
fossil fuels, particularly petroleum-based
products such as gasoline, diesel, or jet fuel.
For example, in 1985 countries belonging to
the OECD met 91% of their transportation
energy requirements with oil-derived products,
8% with electricity, and the remaining 1%
with natural gas and coal (OECD, 1987). As
countries become wealthier, increased use of
petroleum to meet transportation needs can
significantly increase greenhouse gas emissions
to the atmosphere (see Table 4-2).
The amount and type of greenhouse
gases emitted can also be affected by the
transportation technology. For example,
gasoline vehicles produce about 25% less CO2
on an energy input basis than do diesel
vehicles, while producing substantially more
CO. However, the CO is eventually oxidized
to CO2, so the CO2 emissions attributable to
gasoline vehicles are comparable to those of
IV-15
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Policy Options for Stabilizing Global Climate
TABLE 4-3
End-Use Energy Consumption Patterns for
the Residential/Commercial Sectors
(% of total energy)
End-Use
South/Southeast Asia
Heating
Cooling
Cooking
Lighting
TOTAL
United States
Heating
Cooling
Cooking
Lighting
Other
TOTAL
Biomass
0
0
75
0
75%
<1
0
0
0
0
<1%
Type of Energy
Fossil Fuels
16
0
3
1
20%
59
0
7
0
0
66%
Electricity
NA
NA
NA
NA
5%
8
6
3
7
10
34%
Total
NA
NA
NA
NA
100%
67
6
10
7
10
100%
Sources: Sathaye et al., 1989; Mintzer, 1988; EIA, 1987; Leon Schipper, pers. communication.
IV-16
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Chapter IV: Human Activities
diesel vehicles. Also, the efficiencies of diesel
engines are generally greater than those of
gasoline engines for a similar vehicle, implying
that diesel vehicles would actually have lower
effective CO2 emissions per mile travelled.
Similarly, vehicles powered with compressed
natural gas would emit CO2 and CO at lower
levels than would either gasoline or diesel
vehicles, although CH4 emissions might be
higher.
Fuel Production and Conversion
Significant quantities of greenhouse
gases are emitted during the production of
energy and its conversion to end-use energy
forms. Several major components of these
fuel production and conversion processes are
discussed below.
Natural Gas Flaring, Venting, and
Leaking. During the production of oil and
natural gas, some portion of natural gas, which
is mostly methane, is typically vented to the
atmosphere (as CH4) or flared (thereby
producing CO2) rather than produced for
commercial use. Venting typically occurs
during natural gas drilling and well
maintenance operations to avoid pressure
buildup, to test well drawdown, and during
required maintenance at existing production
wells. Flaring is most common in conjunction
with oil production when no market can be
found for the natural gas associated with oil
reservoirs. In some circumstances, the gas may
be vented rather than flared. The amount of
natural gas flared and vented is highly
uncertain. On average, it is estimated to be
about 2-3% of global natural gas production,
although in some regions virtually all of the
natural gas may be vented or flared, while in
other regions (like the U. S.) the total amount
flared or vented is less than 0.5% of total
production (EIA, 1986).9 Currently,
approximately 50 Tg of CO2 are released to
the atmosphere from flaring of natural gas
(Rotty, 1987)/"
10
Leaks of natural gas also occur during
the refining, transmission, and distribution of
the gas. These leaks may occur at the refinery
as the gas is cleaned for market, from the
pipeline system during transportation to the
end user, or during liquefaction and
regasification if liquified natural gas (LNG) is
produced. About 20-50 Tg of CH4 is released
to the atmosphere each year from leaking and
venting of natural gas (Crutzen, 1987;
Cicerone and Oremland, 1988).
Coal Mining. As coal forms, CH4
produced by the decomposition of organic
material becomes trapped in the coal seam.
This CH4 is released to the atmosphere during
coal extraction operations. The amount of
CH4 released by coal mining varies depending
on factors such as depth of the coal seam,
quality of the coal, and characteristics of the
geologic strata surrounding the seam. The
amount of CH4 emitted as a result of coal
mining is highly uncertain, with estimates
ranging from 25 to 45 Tg per year (Cicerone
and Oremland, 1988). If coal mining
operations intensify, the quantity of methane
released as an indirect result of mining is
expected to increase at a comparable rate.
Synthetic Fuel Production. As
conventional petroleum resources are
depleted, some of the demand for liquid (oil
and natural gas liquids) and gaseous (natural
gas) fuels may be met by synthetic fuels.
Although there is currently little synthetic fuel
produced in the world, processes have been
developed to convert relatively abundant solid
energy resources such as coal, oil shale, and
tar sands to liquid or gaseous products that
could be consumed in the same end-use
applications as conventional oil and gas.
Significant amounts of energy are
typically required to produce synthetic fuels.
The conversion process produces greenhouse
gas emissions, particularly CO2, so that the net
emissions per unit of energy for synthetic fuels
are greater than those for conventional fossil
fuels. For example, the CO2 emissions from
production and consumption of synthetic
liquid fuels from coal are about 1.8 times the
amount from conventional liquid fuels from
crude oil (Marland, 1982). Table 4-4 lists
emission rates for both conventional fossil
fuels and synthetic fuels produced from coal
and shale oil.
Future Irends
As shown in Figure 4-4, the quantity of
CO2 emitted to the atmosphere as a result of
the combustion of fossil fuels has increased
dramatically in the last century. This increase
in fossil-fuel-produced CO2 emissions is the
IV-17
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Policy Options for Stabilizing Global Climate
TABLE 4-4
Carbon Dioxide Emission Rates for Conventional
and Synthetic Fuels
Fuel
CO2 Emission Rate
(kg C/109J)
Notes
Conventional Fossil Fuels (rates for consumption)
Natural Gas 13.5-14.2
Liquid Fuels from Crude Oil 18.2-20.6
Bituminous Coal 23.7-23.9
Differences are partly attributable to
product mix, i.e., gasoline versus fuel
oil and gasoline
Synthetic Fuels (rates for production and consumption)
Shale Oil 104.3
66.4
47.6
28.4
Liquids from Coal
High Btu Gas from Coal
51.3
41.8
39.9
38.6
37.2
31.9
30.5
40.7
40.1
36.2
32.7
High temperature, 10 gal/ton shale
High temperature, 25 gal/ton shale
Modified in situ, 28 gal/ton shale
Low temperature retorting
Gasoline from methanol using Mobil
MTG process
Sasol-type technology, Eastern coal
FHP process
Exxon-Donor Solvent, Eastern coal
H-coal
Generic 75% thermal efficiency
SRC-II, liquid and gas products
Lurgi
Hygas
Generic 66% thermal efficiency
Via synthesis gas with by-product
credits
Source: Marland, 1982.
IV-18
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Chapter IV: Human Activities
main factor that has led to an increase in
atmospheric CO2 concentrations -- from about
280 parts per million by volume (ppm) in pre-
industrial periods to about 350 ppm today. As
discussed in Chapter II, future CO2
concentrations will depend on many factors,
but most important will be the rate of growth
in energy demand and the type of energy that
is consumed in order to satisfy this demand.
The Fossil-Fuel Supply
Higher levels of energy demand will
produce higher levels of greenhouse gas
emissions if the demand is satisfied with fossil
fuels. As indicated above, fossil fuels currently
supply a majority of the world's energy needs,
and it seems likely that fossil fuels will
continue to play a key role in the world's
energy supply picture for decades to come.
However, supplies of fossil fuels are not
unlimited. Resource and reserve estimates for
coal, oil, and gas are listed in Table 4-5. A
resource is any mineral supply; a reserve is a
mineral supply that is known with a high
amount of geologic certainty. A reserve may
or may not be presently economical to extract;
if not, it is likely to become economical in the
future. The estimates of the lifetimes of fossil-
fuel reserves are based on 1985 rates of
production. The lifetime estimates of fossil-
fuel resources are based on linear and
exponential extrapolations of recent energy
demand (described below). Despite
uncertainties about the size of the resource
base and the rate at which the resource base
may be depleted, it is clear from a technical
standpoint that the consumption of fossil fuels
could continue for a very long time. As will
be discussed in Chapter VI, if the world
continues to rely on fossil fuels to meet the
majority of its energy needs, the amount of
carbon emitted to the atmosphere may be
many times greater than current levels.
Future Energy Demand
The future rate of energy demand
depends on many variables, including the rate
of population growth, the rate of economic
growth, energy prices, the types of energy
services demanded by consumers, the type and
efficiency of technology used, and the type and
amount of energy supplies available (see
CHAPTER VI). Two hypothetical cases based
on crude extrapolations illustrate potential
upper and lower bounds on future energy
demand (see Figure 4-7) and the lifetime of
fossil-fuel resources (see Tkble 4-5). For
example, from 1950 to 1973, the average
annual growth rate in energy demand was
5.2%. If this rate of growth were
exponentially extrapolated to 2050, global
energy demand would be about 254 terawatts
(TW) (or equivalently about 8000 exajoules
[EJ]), almost 30 times the 1985 level.11 This
amount of energy demand could lead to an
increase in annual CO2 emissions from the
current 5.2 Pg C to about 140 Pg C in 2050,
assuming that this demand is met by
consumption of fossil fuels. Cumulative
energy demand for 1985 through 2050 based
on this extrapolation represents over five times
the amount of fossil fuels in proven reserves
and about 45% of the resource estimate. On
the other hand, the average annual growth rate
in energy demand from 1973 to 1985 was
much lower: about 2.2%. If this rate were
linearly extrapolated to 2050, global energy
demand would be about 23 TW (720 EJ) ~
almost 150% greater than the demand in 1985
- which could increase annual CO2 emissions
from fossil fuels to nearly 13 Pg C.
Cumulative energy demand for 1985 through
2050 based on the linear extrapolation
represents about 115% of proven fossil-fuel
reserves, or nearly 10% of estimated resources.
INDUSTRIAL PROCESSES
There are three significant non-energy
sources of greenhouse gases associated with
industrial activity: the use of
chlorofluorocarbons (CFCs), halons, and
chlorocarbons (collectively, halocarbons);
cement manufacture; and waste disposal in
landfills. The use of CFCs, halons, and
chlorocarbons, which are man-made chemicals
with a variety of applications, results in their
release to the atmosphere. Certain uses, such
as aerosol propellants and solvents, result in
instantaneous release (when the product is
used), while others, such as foam-blowing
agents and refrigerants, result in a delayed
release. Cement manufacture results in CO2
emissions, and waste disposal in landfills
results in CO2 and CH4 emissions, although
only the CH4 emissions are significant in terms
of the total global source.
IV-19
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Policy Options for Stabilizing Global Climate
TABLE 4-5
Estimates of Global Fossil-Fuel Resources9
(Exajoules)
Resource Lifetime (Years)
Coal
Oil
Gas
Geological
Resources
(exajoules)
315,800
12,800
10,100
Reserves
(exajoules)
20,400
4,300
3,700°
Reserves/
Resources
(%)
6
34
37
Reserves
Lifetime13
(Years)
229
41
61
Linear
Extrapolation
524
69
86
Exponential
Extrapolation
103
39
44
a Resources estimates, as of 1985, are from the World Energy Conference (1980), adjusted for global
production from 1979-85. Reserve estimates are from EIA (1986); oil and gas estimates as of January
1, 1986; and coal estimates as of 1981.
b Based on 1985 rates of production.
c Includes estimates for the Middle East and USSR.
Sources: World Energy Conference, 1980; United Nations, 1983, 1987; EIA, 1986.
IV-20
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Chapter IV: Human Activities
FIGURE 4-7
POTENTIAL FUTURE ENERGY DEMAND
(Exajoules/Year)
8000
7000
6000 -
5000 -
40OO
0
x
ID
3000 -
2000 -
1000 -
Exponential Growth
1950
1970 1990 2010
Y«ar
2030
2050
Figure 4-7. Two hypothetical cases of future energy demand. The upper case is based on an
exponential extrapolation of the average annual growth rate in energy demand between 1950 and 1973,
a period of rapid growth in demand. The lower case is based on a linear extrapolation of the average
annual growth rate in energy demand between 1973 and 1985, when the growth rate was much lower.
These two cases illustrate potential upper and lower bounds on future energy demand. (Sources for
historical data: United Nations, 1976,1982, 1983, 1987.)
IV-21
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Policy Options for Stabilizing Global Climate
Chlorofluorocarbons, Halons, and
Chlorocarbons
Historical Development and Uses
Chlorofluorocarbons are man-made
chemicals containing chlorine, fluorine, and
carbon, hence the name CFCs (HCFCs contain
hydrogen as well). Table 4-6 lists the major
CFCs with their chemical formulae. CFCs
were developed in the late 1920s in the United
States as a substitute for the toxic, flammable,
refrigerator coolants in use at that time. The
chemicals, which are noncorrosive, nontoxic,
nonflammable, and highly stable in the lower
atmosphere, provided the refrigerator industry
with a safe, efficient coolant that soon proved
to have numerous other uses as well.
Commercial development of CFCs began in
1931. During World War II, CFCs were used
as propellants in pesticides against malaria-
carrying mosquitos. Since then, CFCs have
been used as aerosol propellants in a wide
range of substances, from hairsprays to spray
paints. In the 1950s, industries began using
CFCs as blowing agents for plastic foam and
foam insulation products. Chillers, used for
cooling large commercial and industrial
buildings, as well as cold storage units for
produce and other perishable goods, became
feasible at this time with the use of CFCs.
Mobile air conditioners (in automobiles,
trucks, and buses) currently constitute the
largest single use of CFCs in the United
States. CFCs are also used in gas sterilization
of medical equipment and instruments, solvent
cleaning of manufactured parts, especially
electronic components and metal parts, and
miscellaneous other processes and products
such as liquid food freezing.
Halons, or bromofluorocarbons, are
man-made chemicals containing carbon,
fluorine, and chlorine and/or bromine (see
Table 4-6 for the chemical formulae of the
major halons in use today). These chemicals
were developed in the 1970s, and are used
primarily as fire extinguishants. Halon 1211 is
used almost exclusively for portable (i.e.,
wheeled or handheld) fire extinguishers,
particularly for situations where human
exposure to the chemical is possible, such as in
airplanes. Halon 1301 is used exclusively for
total flooding fire extinguishing systems such
as those used to protect computer centers,
document rooms, libraries, and military
installations. A summary of the end-use
applications for the major CFC and halon
compounds is shown in Table 4-6.
Chlorocarbons, man-made chemicals
containing chlorine and carbon (see Table
4-6), are used primarily as solvents and
chemical intermediates. The primary
Chlorocarbons are carbon tetrachloride and
methyl chloroform. In the United States,
carbon tetrachloride was once used extensively
as a solvent and grain fumigant, but because of
its toxicity, only small amounts of it are used
in such applications today. Its primary use in
the United States is in the manufacture of
CFC-11 and CFC-12, a process which
consumes or destroys almost all of the carbon
tetrachloride, resulting in very small emissions.
However, carbon tetrachloride is believed to
be used as a solvent in developing countries,
resulting in considerable emissions. Methyl
chloroform is used worldwide as a cleaning
solvent in two applications: 1) vapor
degreasing (the solvent is heated and the item
to be cleaned is suspended in the vapor); and
2) cold cleaning (the part to be cleaned is
submerged in a tank of solvent). Small
amounts are also used in adhesives, aerosols,
and coatings.
Production of CFCs, halons, and
Chlorocarbons has grown steadily as new uses
have developed. Production of the two largest
CFC compounds, CFC-11 and CFC-12,
increased rapidly in the 1960s and early 1970s
(see Figure 4-8). Production peaked in 1974
at 812.5 gigagrams (Gg) and then declined due
to a ban on most aerosol use in the United
States, Canada, and Sweden in the late
1970s.12 However, non-aerosol use has
continued to grow, with 1985 production of
703.2 Gg. Globally, major CFC and halon
consumption reached nearly one Tg in 1985
(see Table 4-7). Global production of carbon
tetrachloride and methyl chloroform in 1985
was estimated at nearly 1029 Gg and 545 Gg,
respectively (Hammitt et al., 1987).
Most CFC and halon consumption
occurs in the United States and other
industrialized nations. Of the 703.2 Gg of
CFC-11 and CFC-12 produced in 1985, about
70% was consumed by the U.S., the EEC, and
Japan (see Figure 4-9). Although CFC use is
concentrated in the industrialized world,
IV-22
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Chapter IV: Human Activities
TABLE 4-6
Major Halocarbons: Statistics and Uses
Chemical
Chlorofluorocarbons
CFC-11 (CC13F)
CFC-12 (CC12F2)
HCFC-22 (CHC1F2)
CFC-113 (C^CljF^
1986
Atmospheric
Concentration
(parts per Atmospheric
trillion by Lifetime
volume) (Years)
226 75 +l]
392 lll^2
80 (1985) 15
30-70 90
Current Annual
Atmospheric
Concentration
Growth Rates Major
(%/yr) Uses
4 Aerosols,
Foams
4 Aerosols, Foams,
Refrigeration
7 Refrigeration,
Fluoropolymer
production
11 Solvents
Halons (Bromofluorocarbons)
Halon 1211 (CBrClF2)
Halon 1301 (CBrF3)
Chlorocarbons
Carbon tetrachloride
(CC14)
Methyl chloroform
(CH3CC13)
-2 25
-2 110
75-100 -40
125 6±1
>10 Fire
extinguisher
>10 Fire
extinguisher
1 Production of
CFC-11 and
CFC-12
—5 Solvents
Sources: U.S. EPA, 1988; Hammitt et aL, 1987; Wuebbles, 1983; WMO, 1985.
IV-23
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Policy Options for Stabilizing Global Climate
FIGURE 4-8
HISTORICAL PRODUCTION OF CFC-11 AND CFC-12
(Gigagrams)
900
800 -
o>
700 -
600
500 -
400
300
200
100
1960 1965
Total
Non-Aerosol
* Dashed line* Indicate estimates
I I I
Aerosol
1970 1975 1980 1985
Year
Figure 4-8. While non-aerosol production of CFC-11 and CFC-12 has grown fairly steadily since 1960, aerosol
production declined in the 1970s and then leveled off in the 1980s due to a ban on most aerosol use of CFCs
in the United States, Canada, and Sweden. (Source: U.S. EPA, 1987.)
IV-24
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Chapter IV: Human Activities
TABLE 4-7
Estimated 1985 World Use of Potential
Ozone-Depleting Substances
(gigagrams)
Other
United Reporting Communist
Chemical World States Countries Countries
CFC-11 341.5 75.0 225.0 41.5
CFC-12 443.7 135.0 230.0 78.7
CFC-113 163.2 73.2 85.0 5.0
Halon 1301 10.8 5.4 5.4 0.0
Halon 1211 10.8 2.7 8.1 0.0
Carbon tetrachloride 1029.0 280.0 590.0 159.0
Methyl chloroform 544.6 270.0 186.7 87.0
Source: Hammitt et al., 1986.
IV-25
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Policy Options for Stabilizing Global Climate
FIGURE 4-9
1985 CFC-11 AND CFC-12 PRODUCTION/USE
FOR VARIOUS COUNTRIES
(Gigagrams)
240
Figure 4-9. The EEC, the United States, and Japan accounted for almost 70% of the 1985 global
production of CFC-11 and CFC-12. (Source: U.S. EPA, 1988.)
IV-26
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Chapter IV: Human Activities
consumption has also increased recently in
developing countries.
The Montreal Protocol
Concern over the effect on the Earth's
atmosphere of CFCs and related
anthropogenically-produced compounds
containing chlorine, bromine, and nitrogen
began in the 1970s. Because of their stability
(i.e., their long lifetimes; see Table 4-6), CFCs
are transported to the stratosphere where they
contribute to the destruction of ozone. Since
the early 1970s, improved understanding of
this process, accumulation of data indicating
growing atmospheric concentrations of CFCs,
and observed depletion of stratospheric ozone,
particularly in the Antarctic, have fueled
international action on this issue.
International negotiations to protect the
stratosphere began in 1981 under the auspices
of the United Nations Environment
Programme (UNEP). These negotiations
culminated in September 1987 in Montreal,
Canada, where a Diplomatic Conference was
held, resulting in an international agreement
("The Montreal Protocol on Substances That
Deplete the Ozone Layer," or the Montreal
Protocol) to begin reducing the use of CFCs
and halons (chlorocarbons were not included).
The Montreal Protocol came into force on
January 1, 1989, and has been ratified by 68
countries, representing just over 90% of
current world production of these chemicals
(as of February 1, 1991). As a result of this
historic agreement, the very high growth rates
in atmospheric CFC concentrations projected
in earlier studies (e.g., Ramanathan et al.,
1985) are not likely to occur. Nevertheless,
because of the long atmospheric lifetimes of
CFCs, their concentrations could continue to
increase for several decades (see CHAPTER
VI). In June 1990 the Protocol was
strengthened by the London Amendments
calling for a complete phase-out of CFCs,
halons, carbon tetrachloride and methyl
chloroform and a non-binding resolution to
phase out HCFCs.
Landfill Waste Disposal
Humans have generated solid wastes
since they first appeared on Earth, although
disposal of these wastes did not become a
major problem until the rise of synthetic
materials (e.g., plastics) and densely-populated
urban areas. The environment can usually
assimilate the smaller amounts of wastes
produced by rural, sparsely-settled
communities. However, because urban
populations produce such high volumes of
waste, due to both the sheer concentration of
individuals contributing to the waste stream
and the high use of heavily-packaged products,
urban waste disposal has become a formidable
task.
Approximately 80% of the municipal
solid wastes collected in urban areas around
the world is deposited in landfills or open
dumps (Bingemer and Crutzen, 1987).
Sanitary landfilling (compaction of wastes,
followed by daily capping with a layer of clean
earth), which became common in the United
States after World War II, is used primarily in
urban centers in industrialized countries.
Open pit dumping is the most common
"managed" disposal method in developing
countries (30-50% of the solid wastes
generated in cities of developing countries is
not collected [Cointreau, 1982]). Most
landfills and many open dumps develop
anaerobic conditions, resulting in decay of
organic carbon to CH4 and CO2. The amount
of CH4 resulting from anaerobic decay of
organic municipal and industrial wastes in
landfills is currently about 30-70 Tg per year
(Bingemer and Crutzen, 1987), approximately
10% of the total annual CH4 source.13
The primary variable affecting gas
generation in landfills is the composition of
the refuse. Wastes high in organic material
(e.g., food wastes, agricultural wastes, paper
products) decompose readily, while inorganics
are relatively unaffected by the decomposition
process. While agriculture is the largest single
source of solid wastes in the U.S. (Berry and
Horton, 1974), most of these wastes are not
landfilled. Increasing urbanization and
demand for "convenience" items, which
encourages marketing of single-serving and
heavily-packaged products, have resulted in
increasingly greater proportions of plastics,
glass, metals, and paper products in the waste
stream. Other factors influencing gas
generation include inclusion of sewage sludge
(which enhances gas generation), oxygen
concentration, moisture content, pH, and
available nutrients.
IV-27
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Policy Options for Stabilizing Global Climate
Disposal of municipal solid waste in
industrial nations increased by 5% per year
during the 1960s and by 2% per year in the
1970s (CEQ, 1982). Currently,'per capita
waste production in industrialized countries is
considerably larger than in developing
countries (see Table 4-8), and the largest
contribution of landfill CH4 comes from the
industrialized world (Bingemer and Crutzen,
1987). Although current rates of waste
disposal in landfills have begun to level off in
many industrialized countries, associated CH4
emissions are probably still growing because
the total quantity of waste in place is still
increasing. In the developing world, with its
high population growth rates and increasing
urbanization, municipal solid waste disposal is
projected to double by the year 2000 (Kresse
and Ringeltaube, 1982), so CH4 production
from waste dumps and/or sanitary landfills can
be expected to increase rapidly in developing
countries.
Cement Manufacture
Cement manufacture produces CO2, as
well as numerous other exhaust gases. As
demand for cement has grown over the last
century, CO2 emissions associated with this
industry have also increased. Between 1950
and 1985, CO2 emissions from cement
manufacture grew from 18 to 134 Tg C/yr (see
Figure 4-10). In recent years CO2 emissions
from cement production have grown at a faster
rate than those from fossil-fuel combustion:
in the early 1950s CO2 emitted as a result of
cement manufacture was approximately 1% of
the amount emitted from the consumption of
fossil fuels; by the early 1980s this fraction had
increased to 2.5% (Rotty, 1987).
The CO2 emissions resulting from
cement manufacture occur during the
production of clinker (round, marble-sized
particles), a material produced midway
through the process. After the raw materials
(cement rock, limestone, clay, and shale) are
quarried and crushed, they are ground and
blended to a mixture that is approximately
80% limestone by weight. The mixture is then
fed into a kiln for firing, where it is exposed to
progressively higher temperatures that cause
heating, then drying, calcining, and sintering.
Finally, the feed is heated to the point of
fusion (approximately 1595°C), and clinker is
produced. It is during the calcination process,
which occurs at approximately 900 to 1000°C,
that the limestone (CaCO3) is converted to
lime (CaO) and CO2, and the CO2 is released.
For every million' tons (Tg) of cement
produced, approximately 0.137 Tg C as CO2 is
emitted from calcining (Rotty, 1987).14 An
additional 0.165 Tg C is emitted per million
tons of cement produced from fossil fuel used
for kiln firing and electricity generation. This
CO2 is accounted for as part of industrial
energy-use emissions.
World cement production has increased
at an average annual rate of approximately 6%
since the 1950s, from 133 million tons in 1950
to 972 million tons in 1985 (U.S. BOM, 1949-
1986). Cement production growth rates in
individual countries have varied during this
period (see Figure 4-11) due to economic
fluctuations in cement's primary market, i.e.,
the construction industry, and competitive
shirts internationally among the primary
cement-producing countries. For example, in
1951 the United States produced
approximately 28% of the global total, while
by 1985 its share had shrunk to 7%.15
During the same time, the production shares
for the USSR grew from 8% to 13%, for
China, from less than 1% to 15%, and for
Japan, from 4% to 8%. Although many
national markets, except the United States',
experienced low levels of demand during the
1980s, global cement production is expected to
continue to grow faster than GNP for some
time.
LAND-USE CHANGE
Over the past few centuries, man has
significantly changed the surface of the Earth.
Forests have been cleared, wetlands have been
drained, and agricultural lands have been
expanded. All of these activities have resulted
in considerable changes in trace gas emissions
to the atmosphere. Deforestation results in a
net release of carbon from both the biota and
the soils (unless the land is reforested) as
these organic carbon pools burn or are
decomposed. Biomass burning, due to shifting
agriculture, burning of savanna, use of
industrial wood and fuelwood, and burning of
agricultural wastes, is a source of CO2, as well
as CH4, N2O, and NOr 16 Destruction of
wetlands, from either filling or dredging, can
alter the atmospheric CH4 budget, since
IV-28
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Chapter IV: Human Activities
TABLE 4-8
Refuse Generation Rates in Selected Cities
Per Capita
Waste
Generation Rate
City (kg per day)
Industrial Cities
New York, United States 1.80
Singapore 0.87
Hong Kong 0.85
Hamburg, West Germany 0.85
Rome, Italy 0.69
Developing Cities
Jakarta, Indonesia 0.60
Lahore, Pakistan 0.60
Tunis, Tbnisia 0.56
Bandung, Indonesia 0.55
Medellin, Colombia 0.54
Surabaya, Indonesia 0.52
Calcutta, India 0.51
Cairo, Egypt 0.50
Karachi, Pakistan 0.50
Manila, Philippines 0.50
Kanpur, India 0.50
Kano, Nigeria 0.46
Source: Cointreau, 1982.
IV-29
-------
Policy Options for Stabilizing Global Climate
FIGURE 4-10
i
+ A f\
IH-O
120
! 100
L.
n
e
o 80
JO
(0
O
i
2 60
O)
ra
o
t-
40
20
19
CO 2 EMISSIONS FROM CEMENT PRODUCTION
1950-1985
(Teragrams Carbon/Year)
X
J
/
/
/
/
^
/
— / —
^/
! I I I I I
50 1955 1960 1965 1970 1975 1980 19
Year
85
Figure 4-10. Carbon dioxide emissions from cement production grew from 18 to 134 Tg between 1950
and 1985, an average annual rate of growth of about 6%. (Sources: Rotty, 1987; U.S. BOM, 1949-
1986, selected years.)
IV-30
-------
Chapter IV: Human Activities
FIGURE 4-11
CEMENT PRODUCTION IN SELECTED COUNTRIES
1951-1985
(Thousand Metric Tons)
150
w
o
H
o
n
**
e
2
•o
c
a
a>
o
£
100 -
50
1951 1955 1960 1965 1970 1975 1980 1985
Year
i |
Figure 4-11. World cement production grew at an average annual rate of about 6% between 1950 and
1985. Growth has been particularly rapid in China, the U.S.S.R., and Japan. (Source: U.S. BOM,
1949-1986, selected years.)
IV-31
-------
Policy Options for Stabilizing Global Climate
anaerobic decomposition in wetlands produces
methane.
Deforestation
Estimates of net emissions of CO2 to
the atmosphere due to changes in land use
(deforestation, reforestation, logging, and
changes in agricultural area) in 1980 range
from 0.4 to 2.6 Pg C (Houghton et al., 1987;
Detwiler and Hall, 1988), which accounts for
approximately 10-30% of annual
anthropogenic CO2 emissions to the
atmosphere. Deforestation in the tropics
accounted for almost all of the flux; the carbon
budget of temperate and boreal regions of the
world has been approximately in balance in
recent years. Of the net release of carbon
from tropical deforestation, 55% was produced
by only six countries in 1980: Brazil,
Indonesia, Columbia, the Ivory Coast,
Thailand, and Laos (see Figure 4-12).
The world's forest and woodland areas
have been reduced 15% since 1850, primarily
to accommodate the expansion of cultivated
lands (IIED and WRI, 1987). The largest
changes in forest area during this period have
occurred in Africa, Asia, and Latin America.
Europe is the only region that has experienced
a net increase in forest area over this time
interval. Forest area began to increase in
Europe in the 1950s and in North America in
the 1960s (see Table 4-9). However, recent
data from the Food and Agriculture
Organization of the United Nations (FAO)
and the U.S. Forest Service indicates that net
deforestation may be occurring in the United
States -- although there are discrepancies
between the two data sets. The FAO data
indicates that between 1980 and 1985 the area
of U.S. forest and woodlands decreased by
approximately 3.8 million hectares (Mha) per
year, or 1.4% per year (FAO, 1986b).17 The
U.S. Forest Service (Alig, 1989) estimates that
between 1977 and 1987 the area of U.S. forests
decreased by approximately 0.41 Mha per year,
or 0.14% per year.
Currently, it is estimated that
approximately 11.3 Mha of tropical forests are
lost each year, while only 1.1 Mha are
reforested per year (FAO, 1985). Most of the
tropical deforestation is due to transfer of
forest land to agricultural use, through shifting
agriculture and conversion to pasture. FAO
has estimated a demand for an additional 113-
150 Mha of cultivated land for the 20-year
period between 1980 and 2000 to meet food
production needs (FAO, 1981). Most of this
land will have to come from areas that were
once forested; however, there is a large
potential to use land currently under shifting
cultivation by adapting low-input agricultural
techniques (see CHAPTER V). Fuelwood use
also contributes to deforestation, particularly
in Africa where fuelwood is a major source of
residential energy. Sixty-three percent of the
total energy consumption of developing
African countries, 17% in the Asian
countries, and 16% in the Latin American
countries, is through fuelwood burning. In the
Sudan, Senegal, and Niger, fuelwood provides
94%, 95%, and 99%, respectively, of
household energy consumption (Anderson and
Fishwick, 1984). Rapidly increasing
populations, particularly in developing nations,
will result in increasing demands on forest
lands to meet growing agricultural and energy
needs.
Biomass Burning
Biomass burning, in addition to
contributing to the atmospheric CO2 budget,
contributes approximately 10-20% of total
annual CH4 emissions, 5-15% of the N2O
emissions, 10-35% of the NOX emissions, and
20-40% of the CO emissions (Crutzen et al.,
1979; WMO, 1985; Logan, 1983; Stevens and
Engelkemeir, 1988; and Andreae et al., 1988).
These estimates are for instantaneous
emissions from combustion. Recent research
has shown that biomass burning also results in
longer-term (at least up to 6 months after the
burn) emissions of NO and N2O due to
enhancement of biogenic soil emissions
(Anderson et al., 1988). Estimates of
emissions of trace gases due to biomass
burning are very uncertain for two reasons: 1)
data on amounts and types of biomass burned
are scarce, and 2) emissions per unit of
biomass burned are highly variable.
Activities associated with biomass
burning include agriculture, colonization,
wildfires and prescribed fires, and burning of
industrial wood and fuelwood. Currently,
agricultural burning, due to shifting
agriculture, savanna burning, and burning of
agricultural wastes, is estimated to account for
over 70% of the biomass burned annually (see
IV-32
-------
Chapter IV: Human Activities
FIGURE 4-12
NET RELEASE OF CARBON FROM
TROPICAL DEFORESTATION
1980
(Teragrams Carbon)
Rest of World (516)
Peru (45)
Burma (51),
Philippines (57)
Nigeria (60)
Laos (85)'
Thailand (95)
Brazil (336)
Indonesia (192)
Ivory Coast (101)
Colombia (123)
Figure 4-12. Tropical deforestation accounts for approximately 10-30% of the annual anthropogenic
CO2 emissions to the atmosphere. Over half of the 1980 CO2 emissions from deforestation was
produced by six countries: Brazil, Indonesia, Colombia, the Ivory Coast, Thailand, and Laos. (Source:
Houghton et al., 1987.)
IV-33
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1'olicy Options for Stabilizing Global Climate
TABLE 4-9
Land Use: 1850-19803
Percentage
Change
1850 to
1850 1860 1870 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1980
Area (million hectares)
ALL TEN REGIONS
Forests and Woodlands
Grassland and Pasture
Croplands
5,919 5.898 5.869 5,833 5.793 5,749 5,696 5,634 5,553 5,455 5,345 5.219 5,103 5,007 -15
0.350 0.340 6.329 6,315 6,301 6,284 6,269 6.260 6,255 6,266 6,293 6.310 6,308 6.299 -1
538 569 608 659 712 773 842 913 999 1,085 1,169 1.278 1.396 1,501 179
Tropical Africa
Forests and Woodlands
Grassland and Pasture
Croplands
1,336 1,333 1,329 1,323 1,315 1,396 1,293 1,275 1.251 1,222 1,188 1,146 1,106 1,074 -20
1.061 1,062 1.064 1,067 1.070 1,075 1,081 1,091 1,101 1,114 1,130 1,147 1.157 1.158 9
57 58 61 64 68 73 80 88 101 118 136 161 190 222 288
North Africa and Middle East
Forests and Woodlands
Grassland and Pasture
Croplands
34 34 33 32 31 30 28 27 24 21 18 17 15 14 -60
1,119 1,119 1,118 1,117 1,116 1,115 1,113 1,112 1,108 1,103 1,097 1,085 1,073 1,060 -5
27 28 30 32 35 37 40 43 49 57 66 79 93 107 294
North America
Forests and Woodlands
Grassland and Pasture
Croplands
Latin America
Forests and Woodlands
Grassland and Pasture
Croplands
China
Forests and Woodlands
Grassland and Pasture
Croplands
South Asia
Forests and Woodlands
Grassland and Pasture
Croplands
Southeast Asia
Forests and Woodlands
Grassland and Pasture
Croplands
Europe
Forests and Woodlands
Grassland and Pasture
Croplands
USSR
Forests and Woodlands
Grassland and Pasture
Croplands
Pacific Developed Countries
Forests and Woodlands
Grassland and Pasture
Croplands
971
571
50
1,420
621
18
96
799
75
317
189
71
252
123
7
169
150
132
1,067
1,078
94
267
638
6
968
559
65
1,417
623
19
93
799
78
315
189
73
252
123
7
158
147
136
1,060
1,081
98
267
638
6
965
547
80
1,414
625
21
91
798
81
311
189
77
251
122
8
157
145
140
1,052
1,083
103
266
638
7
962
535
95
1,408
627
24
89
796
84
307
189
81
251
121
10
157
144
142
1,040
1,081
118
265
637
9
959
522
110
1,401
630
28
86
797
86
303
189
85
250
119
12
156
143
143
1,027
1,079
132
264
635
12
954
504
133
1,394
634
33
84
797
89
299
189
89
249
118
15
156
142
145
1,014
1,078
147
263
634
14
949
486
156
1,383
638
39
82
797
91
294
190
93
248
116
18
155
141
146
1,001
1,076
162
262
632
17
944
468
179
1,369
646
45
79
796
95
289
190
98
247
114
21
155
139
147
987
1,074
178
261
630
19
941
454
1%
1,348
655
57
76
7%
96
279
190
108
246
111
25
155
138
149
973
1,072
194
260
629
22
940
450
201
1,316
673
72
73
794
103
265
190
122
244
108
30
154
137
150
961
1,070
208
259
627
24
939
446
206
1,273
700
87
69
793
108
251
190
136
242
105
35
154
136
152
952
1,070
216
258
625
28
939
446
205
1,225
730
104
64
789
117
235
190
153
240
102
40
156
136
151
945
1,069
225
252
617
42
941
447
204
1,186
751
123
59
784
127
210
189
178
238
97
47
161
137
145
940
1,065
233
247
609
56
942
447
203
1,151
767
142
58
778
134
180
187
210
235
92
55
167
138
137
941
1,065
233
246
608
58
^3
-22
309
-19
23
677
-39
-3
79
-43
-1
196
-7
-25
670
4
-8
4
-12
-1
147
-8
-5
841
a These three categories refer to aggregate data from eleven categories of natural land cover. Land areas covered by snow, ice, rock, or desert are the only
categories not included here.
Source: IIED and WRI, 1987.
IV-34
-------
Chapter IV: Human Activities
Table 4-10). Biomass burning is a particularly
important source of trace gas emissions in the
tropics, where forest exploitation is
unsurpassed. Continued rapid population
growth and exploitation of forests may
substantially increase emissions from biomass
burning in the future.
Wetland Loss
Annual global emissions of CH4 from
freshwater wetlands are estimated to be 110
Tg, approximately 25% of the total annual
source of 400 to 600 Tg (Matthews and Fung,
1987). Of the approximately 530 Mha
producing this CH4, 39% is forested bog, 17%
is nonforested bog, 21% is forested swamp,
19% is nonforested swamp, and 4% is alluvial
formations.18 The bulk of the bog acreage is
located between 40°N and 70°N, while swamps
predominate between 10°N and 30°S. Alluvial
formations are concentrated between 10°N and
40°S (see Figure 4-13). Coastal saltwater and
brackish-water environments produce minor
amounts of CH4 in comparison, probably due
to the inhibitory effects of dissolved sulfate
(SO4) in the interstitial water of salt-marsh
sediments (DeLaune et al., 1983; Bartlett et
al., 1985).
The latitudinal distribution of wetland
CH4 emissions is estimated to be very similar
to the latitudinal distribution of freshwater
wetland area. About 50% of the emissions
originate between 50°N and 70°N, and about
25% between 20°N and 30°S. The source of
the high-latitude emissions is organic-rich
bogs, while most of the low-latitude emissions
come from swamps (see Figure 4-13).
Between 25 and 50% of the world's
original swamps and marshes have been
eliminated by human activities (IIED and
WRI, 1987). For centuries people have
drained and filled marshes and swamps to
create dry land for agricultural and urban
development. Wetland areas have been
converted to open water by dredging and
installation of flood-control levees, and have
been used as disposal sites for dredge
materials and solid wastes. Peat mining and
pollution from agricultural and industrial
runoff have also contributed to the destruction
of wetlands. By 1970, more than half of the
original wetland acreage in the United States
had been destroyed (IIED and WRI, 1987).
Between the mid-1950s and mid-1970s, there
was a net loss of wetlands in the United States
of approximately 4.6 Mha, 97% of which
occurred in inland freshwater areas (OTA,
1984). Agricultural conversions were
responsible for 80% of this freshwater wetland
loss.19 Wetland loss has also been extensive
in Europe and the Asia-Pacific region. For
example, approximately 40% of the coastal
wetlands of Brittany, France, have been lost in
the last 20 years, and 8100 ha of wetlands on
the east coast of England have been converted
to agricultural use since the 1950s. Large-
scale wetland losses have not been as prevalent
in the developing world, but rising populations
will result in increasing demands for
agricultural expansion. There is already
pressure to develop two large wetland systems
in Africa, the Okavango Swamps of Botswana
and the Sudd Swamps of southern Sudan, for
agricultural use (IIED and WRI, 1987).
AGRICULTURAL ACTIVITIES
Three agricultural activities contribute
directly to atmospheric emissions of
greenhouse gases: enteric fermentation in
domestic animals, rice cultivation, and use of
nitrogenous fertilizer.20 Global demand for
food and agricultural products has more than
doubled since 1950, fueled by rising
populations and incomes. Agricultural
advancements during the post-war years, such
as the "Green Revolution," brought
improvements in soil management and disease
control, new high-yielding varieties of crops,
increased application of commercial fertilizers,
and increased use of machinery. Between 1950
and 1986, world grain production increased
from 624 to 1661 million tons and average
yield more than doubled, from 1.1 to 2.3 tons
per ha (Wolf, 1987). Over this same time
interval, growth of various domestic animal
populations ranged from 20 to 150% (Crutzen
et al., 1986) and fertilizer consumption grew
approximately 750% (Herdt and Stangel,
1984). According to projections by the Food
and Agriculture Organization of the United
Nations, by the year 2000, a world population
of about 6 billion will require an agricultural
IV-35
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Policy Options for Stabilizing Global Climate
TABLE 4-10
Summary Data on Area and Biomass Burned
Activitv
Burned and/or
Cleared Area
(million ha)
Burned Biomass
(100 Tg dry matter)
Burning due to shifting agriculture
Deforestation due to population
increase and colonization
Burning of savanna and brushland
Wildfires in temperate and
boreal forests
Prescribed fires in temperate forests
Burning of industrial wood and fuelwood
Burning of agricultural wastes
TOTAL
21-62 (41)*
8.8-15.1 (12.0)
(600)
4.0-6.5 (5.4)
2.0-3.0 (2.5)
630-690 (660)
9-25 (17)
5.5-8.8 (7.2)
4.8-19(11.9)
1.9-3.2 (2.6)
0.1-0.2 (0.2)
10-11 (10.5)
17-21 (19)
48-88 (68)
* Data in parentheses represent average values.
Source: Crutzen et al., 1979.
IV-36
-------
Chapter IV: Human Activities
FIGURE 4-13
WETLAND AREA AND ASSOCIATED METHANE EMISSIONS
N
5
1400
1200 i—
1000 —
800 —
600
400 '—
200 I—
BON 70 60 60 40 30 20 10
10 20 30 40 SOS
40
30
20
10
80N 70 60 60 40 30 20 10 0 10 20 30 40 608
\/l Alluvial
•s -V'
\\i Nonf or«*t«d «w«mp
Forested swamp
Nonf or»at*d bos
Forottod bog
Figure 4-13. Estimated latitudinal distribution of wetland area (top) and associated methane
emissions (bottom). Forested and non-forested bogs located between 40° and 70°N account for
approximately 50% of the current CH4 emissions from wetlands. (Source: Matthews and Fung,
1987.)
IV-37
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Policy Options for Stabilizing Global Climate
output approximately 50 to 60% greater than
that required in 1980 (FAO, 1981).
Enteric Fermentation In Domestic Animals
Methane is produced as a by-product of
enteric fermentation in herbivores, a digestive
process by which carbohydrates are broken
down by microorganisms into simple molecules
for absorption into the bloodstream. Both
ruminant animals (e.g., cattle, dairy cows,
sheep, buffalo, and goats) and some non-
ruminant animals (e.g., pigs and horses)
produce CH4. The highest CH4 losses are
reported for ruminants (approximately 4-9% of
total energy intake), which are able to digest
cellulose due to the presence of specific
microorganisms in their digestive tracts. The
amount of CH4 that is released from both
ruminant and non-ruminant animals depends
on the type, age, and weight of the animal, the
quality and quantity of feed, and the energy
expenditure of the animal.
Of the annual global source of 400-600
Tg CH4, domestic animals contribute
approximately 65-85 Tg (Crutzen et al., 1986;
Lerner et al., 1988). Domestic animals that
produce the bulk of the CH4 are (in
decreasing order of amount produced) cattle,
dairy cows, buffalo, goats, sheep, camels, pigs,
and horses. Currently, approximately 57%
comes from cattle, and 19% from dairy cows.
Domestic animals in six countries, India, the
USSR, Brazil, the U.S., China, and Argentina,
produce over 50% of the methane by enteric
fermentation (Lerner et al., 1988).
The domestic animal population has
increased considerably during the last century.
Between the early 1940s and 1960s, increases
in global bovine and sheep populations
averaged 2% per year. Since the 1960s, the
rates of increase have slowed somewhat, to
1.2% and 0.6% per year, respectively (see
Figure 4-14). The annual increases in global
populations of pigs, buffalo, goats, and camels
since the 1960s have been comparable: 1.4%,
1%, 1.2%, and 0.5%, respectively. The horse
population declined about 0.25% per year.
For comparison, the average annual increase
in global human population since the 1960s
has been about 1.8%.
Rice Cultivation
Anaerobic decomposition of organic
material in flooded rice fields produces
methane, which escapes to the atmosphere by
ebullition (bubbling) up through the water
column, diffusion across the water/air
interface, and transport through the rice
plants. Research suggests that the amount of
CH4 released to the atmosphere is a function
of rice species, number and duration of
harvests, temperature, irrigation practices, and
fertilizer use (Holzapfel-Pschorn and Seiler,
1986; Seiler et al., 1984; Cicerone et al., 1983).
Rice cultivation has grown tremendously
since the mid-1900s, due both to increases in
crop acreage and yields.21 Between 1950 and
1984, rough rice production grew from 163 to
470 million tons, nearly a 200% increase.22
During the same time, harvested rice paddy
area increased approximately 40%, from 103 to
148 Mha, and average global yields doubled,
from 1.6 to 3.2 tons per ha (IRRI, 1986).25
Average yields higher than 5 tons per ha have
already been obtained in parts of the
developed world (FAO, 1986a). The increase
in rice production has been due both to the
"Green Revolution" of the 1960s, which
resulted in the development and dissemination
of high-yield varieties of rice and an increase
in fertilizer use, and to a significant expansion
of land area under cultivation. Methane
emissions are probably primarily a function of
area under cultivation, rather than yield,
although yield could influence emissions,
particularly if, in order to increase yield, more
organic matter is incorporated into the paddy
soil.
Over 90% of global rice acreage and
production occurs in Asia. Five Asian
countries, China, India, Indonesia, Bangladesh,
and Thailand, account for 75% of global
production and 73% of the harvested area
(IRRI, 1986; see Figures 4-15 and 4-16). Rice
fields contribute 60-170 Tg of methane per
year to the atmosphere, or approximately 20%
of the global flux (Cicerone and Oremland,
1988). This estimate is highly uncertain
because there have been no comprehensive
rice-paddy flux measurements in the major
rice-producing countries in Asia.
IV-38
-------
Chapter IV: Humnn Activities
FIGURE 4-14
TRENDS IN DOMESTIC ANIMAL POPULATIONS
1890-1985
(Millions)
1400
1200
1000
«
I
800
600
400
200
1890
Cattle
Sheep
x Goats
x !
Buffalos
Horses
Camels
1925
1945
1965
1985
Year
Figure 4-14. Global domestic animal populations have grown by about 0.5 to 2.0% per year during
the last century. Currently, domestic animals account for about 15% of the annual anthropogenic
CH4 emissions. Note: The cattle population figures include dairy cows. (Sources: Crutzen et al.,
1986; FAO, 1971, 1982, 1986a.)
IV-39
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Policy Options for Stabilizing Global Climate
FIGURE 4-15
ROUGH RICE PRODUCTION
1984
(Million Tons)
Rest of World
(75.1)
Vietnam
China
(181.0)
Burma
(14.5)
Thailand
(19.2)
Bangladesh
(21.5)
Indonesia
(37.5)
India (91.0)
Figure 4-15. Distribution of the total rough rice production of 470 million tons. Five Asian
countries, China, India, Indonesia, Bangladesh, and Thailand, accounted for approximately 75% of the
1984 global rice production. (Source: IRRI, 1986.)
IV-40
-------
Chapter IV: Human Activities
FIGURE 4-16
RICE AREA HARVESTED
1984
(Million Hectares)
Rest of World
(27.9)
India
(42.8)
Vietnam
(5.6)
Thailand
(9.7)
Indonesia
(9.7)
Bangladesh
(10.5)
China
(34.3)
Figure 4-16. Distribution of the total harvested rice paddy area of 148 Mha. Five Asian countries,
India, China, Bangladesh, Indonesia, and Thailand, accounted for 73% of the 1984 rice acreage
harvested. (Source: IRRI, 1986.)
IV-41
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Policy Options for Stabilizing Global Climate
Use of Nitrogenous Fertilizer
Nitrous oxide is released through
microbial processes in soils, both through
denitrification and nitrification. Nitrogenous
fertilizer application enhances N2O flux rates,
since some of the applied fixed N is converted
to N2O and released to the atmosphere. The
amount of N2O released depends on rainfall,
temperature, the type of fertilizer applied,
mode of application, and soil conditions.
Nitrogen is currently the most abundant
commercial fertilizer nutrient consumed
worldwide. Its dominance in the fertilizer
markets has increased steadily over the last
few decades, from 28% of total nutrients
(nitrogen, phosphorus, and potassium) in 1950
to 64% in 1981 (Herdt and Stangel, 1984).
Approximately 70.5 million tons N was
consumed worldwide in 1984/1985 in the form
of nitrogenous fertilizers (FAO, 1987). A
preliminary estimate suggests that this
produced N2O emissions of 0.14-2.4 Tg N of
the global source of approximately 8-22 Tg N
per year (Fung et al., 1988), although this
estimate is highly uncertain. Fjcperiments to
determine the fraction of fertilizer nitrogen
lost to the atmosphere as nitrous oxide have
shown a wide range of results (see Table 4-11
and CHAPTER II). Anhydrous ammonia,
which requires sophisticated equipment for
application (it is injected under pressure into
the soil), is used exclusively in the United
States. It comprises about 38% of the U.S.
nitrogenous fertilizer consumption. Urea,
which is usually broadcast as pellets by hand,
comprises about 69% and 58% of nitrogenous
fertilizer consumption in Asia and South
America, respectively.
Asia, Western Europe, Eastern Europe,
and North America consume the major share
of the world's nitrogenous fertilizers
(collectively, about 85%). China, the Soviet
Union, and the United States together account
for approximately one-half of the world's
fertilizer consumption. The twelve largest
nitrogen fertilizer consumers, all of which
consume more than one million tons N
annually, are (in decreasing order): China, the
United States, the Soviet Union, India, France,
the United Kingdom, West Germany, Canada,
Indonesia, Poland, Mexico, and Italy (see
Figure 4-17). Together, these twelve countries
account for approximately 74% of the annual
nitrogenous fertilizer consumption.
Although developed nations will
probably increase their consumption of
commercial fertilizer over the next few
decades, most of the increased demand will
occur in developing nations. The World Bank
estimates that over 90 million tons N will be
consumed in 1997/98, a 30% increase over
consumption in 1986/87. Almost 50% of the
growth between 1986/87 and 1997/98 is
expected to occur in the developing nations
(World Bank, 1988).
IMPACT OF CLIMATE CHANGE ON
ANTHROPOGENIC EMISSIONS
Climate change will affect human
activity in a myriad of ways, and thus influence
anthropogenic emissions of greenhouse gases
(see BIOGEOCHEMICAL CLIMATE
FEEDBACKS in CHAPTER III). The impact
of climate change on land-use patterns and
agricultural practices could be particularly
significant in influencing the trace gas
emissions from these sources. For example,
increases in the frequency and severity of
droughts in farm belt regions will increase
irrigation needs and associated energy
requirements, resulting in increased energy
emissions. However, the magnitude (or even
the direction) of such changes have not been
examined to date. More information is
available regarding the impact of climate
change on electric utilities (Linder et al.,
1987). A brief discussion of this subject is
presented here as an illustration of some ways
in which climate change can, in turn, influence
trace gas emissions.
Linder and Inglis (1989) estimate that
annual electricity consumption increases by 0.5
to 2.7%/°C for utilities in the United States,
depending on the local climate and the
fraction of buildings with electrical heating and
air-conditioning equipment. If climate change
leads to increases in ownership levels of this
equipment, then substantially greater
sensitivities are possible (Linder et al., 1987).
Currently, 37% of total CO2 emissions from
IV-42
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Chapter IV: Human Activities
TABLE 4-L1
Nitrous Oxide Emissions by Fertilizer Type
Fertilizer Type
Percent of Nitrogenous Fertilizer Evolved as N-,0
Anhydrous Ammonia
Ammonium Nitrate
Ammonium Type
Urea
Nitrate
0.5 to 6.84
0.04 to 1.71
0.025 to 0.1
0.067 to 0.5
0.001 to 0.50
Source: Eichner, 1988; Galbally, 1985.
IV-43
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Policy Options for Stabilizing Global Climate
FIGURE 4-17
NITROGEN FERTILIZER CONSUMPTION
1984/1985
(Million Metric Tons Nitrogen)
.3)
.5)
Poland (1.2)
Indonesia (1.3) \ Mexico (1.2)
Canada (1.:
West Germany (1.!
United Kingdom (1.6)
France (2.4)
India (5.7)
Rest of World (18.9)
Soviet Union
(10.9)
China (13.7)
United States (9.5)
Figure 4-17. Distribution of the total nitrogenous fertilizer consumption of 70.5 million tons N.
China, the United States, and the Soviet Union together accounted for just over 50% of the 1984/1985
global fertilizer consumption. Currently, 5-35% of the total anthropogenic N2O emissions is
attributed to nitrogenous fertilizer consumption. (Source: FAO, 1987.)
IV-44
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Chapter IV: Human Activities
fossil fuels are produced by electric utilities,
and this share is expected to increase in the
future (see CHAPTER VI). Applying the U.S.
average sensitivity of 1.0%/°C obtained by
Linder and Inglis (1989) to the rest of the
world implies a feedback on CO2 emissions of
0.4%/°C. This feedback would be offset to an
extent that has not been estimated by lower
fuel use for heating, but as the penetration of
air conditioning rises in developing countries
this feedback could increase.
Climate change may affect the electricity
industry from the supply side as well. When
steam is produced to generate electricity in a
powerplant, either water (usually from a
nearby reservoir or river) or air is used as a
coolant to condense the steam back into water
and start the process over again. Higher
atmospheric temperatures will result in
warming of these coolants, and reduction in
the efficiency of the powerplants. This effect
is not likely to be as significant as others,
however, since seasonal temperature changes
are already much greater than the warming
predicted for the next century (Linder et al,
1987).
More immediate and acute effects of
climate change on electric utilities are likely to
occur due to reduced availability of water.
The drought of the summer of 1988 resulted in
such low river levels in the U.S. Midwest that
some electric plants were forced to reduce
generation due to lack of cooling water. More
frequent and severe droughts would also result
in reduced hydropower for generation of
electricity. (This change would also affect
barge snipping, since many rivers would
become unnavigable, and result in increased
trace gas emissions from truck and rail
transport.)
Sea-level rise and lowered stream flows
resulting from climate change would also have
adverse effects on electric utilities. Salinities
in rivers and estuaries would increase, and
stream chemistry could change, possibly
causing the water to become too corrosive to
be used as a coolant. A few powerplants in
the United States use salt water for cooling
purposes, so the technology to adapt to more
saline coolants does exist, although the
conversion process is costly
These feedback mechanisms are likely to
have a smaller influence on future warming
than the biogeochemical feedbacks discussed in
Chapter III. The impact of climate change on
anthropogenic trace gas emissions may
nevertheless prove to be important and should
be investigated further.
NOTES
1. Anthropogenic sources of trace gases
are those resulting from human activities, e.g.,
combustion of fossil fuels. These sources are
distinguished from natural sources, since
emissions from anthropogenic sources result in
unbalanced trace gas budgets and
accumulation of gases in the atmosphere.
2. Throughout the report these gases are
often referred to as greenhouse gases, although
strictly speaking, CO and NOX are not
greenhouse gases since they do not directly
affect radiative forcing (see CHAPTER II).
However, these two gases indirectly affect
greenhouse forcing due to their chemical
interactions with other gases in the
troposphere. As a result, for simplicity, we
shall refer to them as greenhouse gases.
3. In some developing countries, the
dependence on biomass can approach 95% of
total energy requirements.
4. Non-commercial biomass estimates are
not included in these figures.
5.
In 1986 CO2 emissions from fossil fuels
were approximately 5370 million metric tons
C, or 5.37 Pg C. 1 billion metric tons = 1
" grains.
gigaton = 1 pg = 1015
6. The OECD countries include Australia,
Austria, Belgium, Canada, Denmark, Finland,
France, the German Federal Republic, Greece,
Iceland, Ireland, Italy, Japan, Luxembourg, the
Netherlands, New Zealand, Norway, Portugal,
Spain, Sweden, Switzerland, Turkey, the
United Kingdom, and the United States.
IV-45
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Policy Options for Stabilizing Global Climate
7. 1 GJ = 1 gigajoule = 109 joules. 1055
joules = 1 Btu.
8. For example, some food production
processes use natural gas because its relatively
clean-burning characteristic allows it to be
used when product contamination may be an
issue. Similarly, melters in the glass industry
are often designed to burn natural gas because
of the flame characteristics of this fuel. Use of
other fuels would tend to produce an inferior
product and likely require the redesign of
equipment.
9. U.S. regulations strictly govern the
flaring and venting of natural gas. In other
parts of the world, however, insufficient data
exists to determine whether the natural gas is
flared or vented, although safety precautions
would strongly encourage flaring rather than
venting.
10. 1 TR = 1 teragram = million metric
tons = 10 grams.
11. TW = Terawatt-years per year = 1012
watt-years per year; 1 TW = 31.53 EJ; 1 EJ =
1 Exajoule = 1018 joules; 1055 joules = 1 Btu.
12. 1 Gg = 109 grams = 106 kg.
13. This estimate does not include methane
from anaerobic decomposition of agricultural
wastes, which could be a significant quantity.
The total amount of carbon in agricultural
wastes in the United States alone is already 2.5
times larger than the 113 million metric tons
of waste carbon that are generated and
dumped in landfills worldwide (Bingemer and
Crutzen, 1987).
14. 1 ton = 1 metric ton = 1000 kg.
15. The U.S. is currently a net importer of
cement; the volume of its imports has grown,
representing only a small percentage of
consumption in the early 1980s but as much as
18% in 1986 (ITA, 1987).
16. Shifting agriculture is the practice of
clearing and planting a new area, farming it
until productivity declines, and then moving on
to a new plot to start the cycle over again. If
the land is allowed to reforest for a long
enough period of time, there are no net CO2
emissions.
17. 1 ha = 1 hectare = 2.471 acres.
18. Bogs are peat or organic-rich systems,
usually associated with waterlogging and
seasonal freeze-thaw cycles; swamps are low-
organic formations occurring most commonly
in the tropics, and alluvial formations are low-
organic riverine formations.
19. For example, drainage of prairie
potholes in Iowa to provide new farmland has
resulted in the reduction of Iowa's original
wetlands by over 98%, from 930,000 ha when
settlement began, to 10,715 ha today.
20. Emissions due to energy requirements in
agriculture, such as energy use for irrigation
equipment and other farm machinery, are
accounted for as part of industrial energy use
emissions.
21. Rice statistics are for rice grown in
flooded fields, i.e., they do not include upland
rice, since methane emissions result only from
flooded rice fields.
22. Rough rice, also called paddy rice, is
rice with the hull, or husk, attached. The hull
contributes about 20% of the weight of rough
rice. The kernel remaining after the hull is
removed is brown rice. Milling of brown rice,
which removes the bran, followed by polishing,
results in white rice.
23. Harvested area is the area under
cultivation multiplied by the number of crops
per year. For example, 1 ha that is triple-
cropped is counted as 3 ha of harvested area.
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rv-si
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CHAPTER V
TECHNICAL OPTIONS FOR REDUCING
GREENHOUSE GAS EMISSIONS
FINDINGS
• A number of technical changes which
could reduce sources of greenhouse emissions
are believed likely to be feasible at reasonable
economic costs. No single technology or
small set of technical options offers "a
solution" to greenhouse gas emissions. Only
by aggregating the effects of many technical
opportunities over a long time can significant
reductions in greenhouse gas emissions be
achieved. This chapter highlights options that
appear to be "relatively cost-effective."
Detailed analysis necessary to quantify total
costs of the measures has not been
conducted.
• Improvements in end-use energy
efficiency provide the best option for reducing
carbon dioxide (CO2) emissions over the next
few decades. Reductions in energy use would
also reduce emissions of methane (CH4),
nitrous oxide (N2O), nitrogen oxides (NOX),
and carbon monoxide (CO). Examples of
potential efficiency improvements are:
Transportation — 50 mile per
gallon automobiles are technically feasible
with currently-available technology. Further
improvements could increase fuel efficiency to
more than 80 miles per gallon. What effects
these changes would have on size, safety,
performance, cost, and other desirable product
characteristics need to be carefully considered.
In addition, major improvements in the fuel
efficiency of diesel trucks, rail transport, and
aircraft are possible.
Residential and Commercial - By
2025 accelerated improvements in building
shells, lighting, space conditioning, and
appliances could reduce energy consumption
per square foot by 75% below current levels
for residences, and by 50% for commercial
buildings. The rate at which such
improvements would find market acceptance
both in increases in the building stock and in
retrofitting or replacing the existing building
stock is dependent on a number of complex
economic factors, including the costs of such
improvements, and therefore is quite
uncertain.
Industrial Energy — Advanced
industrial processes for energy-intensive basic
materials, recycling of used basic materials
(i.e., steel, aluminum, and glass),
cogeneration, and improved electric motors
could reduce industrial energy use
significantly. This is especially important for
most developing countries and Eastern
Europe, where industrial energy is currently
the largest share of total energy use and rapid
growth is expected.
• Reforestation may offer one of the most
cost-effective technical options for reducing
CO2 and other gases. At some point, the costs
of reforestation are likely to rise rapidly, as the
costs of reforesting poorer lands rise or as the
costs of bringing lands into forestry from other
uses with high economic yields increases. The
world-wide cost curve for reforestation
opportunities is not well understood.
Preliminary estimates of the feasibility of
large-scale reforestation suggest that with
aggressive reforestation programs the current
deforestation trend might be reversed and that
a significant net increase in forest biomass is
possible. An effective program could include
programs to increase forest biomass - by
replanting marginal agricultural lands,
improving management of existing forests,
building tree plantations, and increasing urban
planting ~ as well as programs to reduce
demand for wood where resources are
currently stressed. This, according to some
estimates, could convert world forest
management practices from a net source to a
net sink for 0.7 petagrams of carbon/year, or
more, by the year 2025.
• Elimination of chlorofluorocarbons
(CFCs) and related compounds over the next
decade appears technically feasible and cost-
effective. Substitutes or process changes now
available or under development have been
identified to reduce or eliminate almost all
applications of CFCs and halons. Key
examples are:
V-l
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Policy Options for Stabilizing Global Climate
Worldwide replacement of CFCs
as an aerosol propellent with substitutes
already in use in the U.S., Canada, and
Sweden.
Replacement of CFC-12 with
substitutes (such as HFC-134a or other
hydrochlorofluorocarbons) in mobile air
conditioners.
Replacement of CFC solvent use
with aqueous cleaning in the electronics
industry.
Replacement of CFC-blown foam
insulation with other materials or use of
alternative blowing agents.
• Several actions may be possible to
reduce greenhouse gas emissions from agri-
culture. The magnitudes of the agricultural
sources, as well as the potential effects of
control measures, are difficult to quantify.
Further detailed research and data collection
will be required in order to produce credible
estimates. Major agricultural activities of
interest are:
Methane emissions from livestock
might be reduced through increases in pro-
ductivity of livestock systems and use of
methanogenesis inhibitors for beef cattle.
Methane emissions from rice
production may be reduced somewhat through
productivity increases and removal of crop
residues. In the long term, improvements in
varieties of rice, soil amendments, and water
management practices could decrease CH4
emissions.
Biomass burning associated with
agricultural practices produces N2O, CO, and
CH4. Changing those practices, for example,
practicing sustainable agriculture or utilizing
crop residues, is technically feasible and could
substantially reduce emissions.
N2O emissions from fertilizer use
could probably be reduced through better
placement of the fertilizer, nitrification
inhibitors, and fertilizer coatings, which may
also reduce farming costs and agricultural
runoff problems.
• Near-term reductions in greenhouse
gas emissions from electricity generation are
possible through:
Efficiency improvements
Improved fossil electricity generation
technology, such as advanced combustion
turbines and cogeneration, can increase the
efficiency of using these fuels by up to 25%.
More efficient transmission and distribution,
availability or capacity improvements at
existing non-fossil powerplants (i.e., nuclear,
hydro), and changes in electric utility system
operation (i.e., dispatching, wheeling across
regions or even internationally) can reduce
CO2 emissions by a few percent per kwh of
electricity delivered. The rate at which such
efficiency improvements are likely to be
implemented is uncertain. Electric generation
facilities are long-lived, and the economic
factors entering into decisions to replace
existing facilities are complex.
Fuel switching - Use of more
natural gas to displace coal as a fuel for
generating electricity could reduce CO2
emissions by a substantial amount in the near
term. The potential of this option is largely
dependent on availability and cost of natural
gas in the future. Wood, municipal waste,
wind, etc., could play a somewhat larger role
than they currently play in the near term.
• Alternative fuels that do not emit
significant amounts of greenhouse gases could
make an important contribution to reducing
these emissions in the medium term and
could virtually eliminate many categories of
emissions over the long term. For widespread
use of alternative fuels, important engineering,
economic, environmental, and social issues
must be resolved.
Hydroelectric power is already
making a significant contribution to global
energy production. There appears to be a
significant potential to expand this
contribution, although environmental and
social impacts of large-scale projects must be
considered carefully. How great the potential
for expansion, after taking into account the
economic costs and benefits of available
hydropower sites and the limitations due to
environmental and social impacts, is unknown.
V-2
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Chapter V: Technical Options
Biomass energy is currently being
extensively utilized, particularly in developing
countries. Current and emerging technologies
could vastly improve the efficiency of that use.
More advanced technologies, especially for
conversion of biomass to gaseous and liquid
fuels and electricity could become
economically competitive within a decade.
Measures to increase biological productivity
are also under study. These advances would
allow biomass to provide a much larger share
of global energy services over the long term,
particularly in developing countries. There
are certain environmental and social issues
associated with large-scale biomass use; these
involve, for example, land use, competition
with food production, and paniculate and
organic emissions.
Solar energy offers a large range
of options. Direct use of solar thermal
energy, either passively or in active systems, is
already commercially available for water and
space heating applications in many regions.
These applications could be expanded
considerably in the near to medium term.
Solar thermal concentrating technologies are
widely being tested for power generation or
industrial process heat and are already
competitive in some locations. Solar
photovoltaic cells are economically
competitive for some remote power
generation needs, especially in developing
countries. If current research and testing
succeeds in lowering the cost in the next
decade, solar electricity generation and/or
photolysis could play a major role in meeting
energy needs in the next century.
Geothermal energy resources are
extensive and widely distributed. Systems are
commercially available for electricity
generation, and over 7 gigawatts of capacity
are currently in operation worldwide.
Technologies are improving and being
demonstrated rapidly. It may be possible to
expand this energy source significantly in the
future.
Wind energy systems are
currently commercial in some applications and
locations. In recent years engineering
advances have resulted in reductions in cost
and improvements in performance. Assuming
this trend continues, wind energy can play a
larger role in future energy production.
-- Nuclear fission is a technology that
is currently widely used and increasing its
contribution to global energy supply due to
the completion of powerplants ordered during
the 1970s. High cost and concerns about
safety, nuclear weapons proliferation, and
radioactive waste disposal have brought new
orders to a halt in most countries. It is
technically feasible to expand the contribution
of this energy source beyond what is currently
projected in the future, if these problems are
resolved.
• Emission controls -- Control
technologies are currently available and in use
in some countries that reduce CO and NOX
emitted from automotive and industrial
sources and NOX produced by power
generation at relatively low cost. Other
technologies, which remove larger fractions of
these pollutants but at higher cost, are also
available. Emerging control technologies and
combustion technologies with inherently lower
NOX emissions are being tested and could
reduce NOX emissions drastically at a lower
cost. In a few very limited situations (i.e.,
combined with enhanced oil recovery), CO2
recovery from powerplant flue gases may be
economic.
• Methane emissions from coal seams,
natural gas production, and landfills can be
reduced. The current emissions from coal
production and landfills are projected to grow
in the future. Natural gas (primarily
methane) is sometimes vented and often
flared in conjunction with oil production.
Technologies exist for economically recovering
this methane and using it for energy
production, thereby partially augmenting
natural gas supply.
• Aggressive research programs may be
the most important policy option for the long
run. Resolution of several key technical
issues could vastly expand the economically
attractive options for reducing greenhouse gas
emissions in the next century. Some
important examples are:
V-3
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Policy Options for Stabilizing Global Climate
Improved characterization of
sources and control options in several areas
would allow better policy and research
planning decisions to be made. Since sources
of N2O and CH4 are poorly understood at
present, field measurement and data collection
work are needed to increase our under-
standing of the potential role that reductions
in these emissions could play in an overall
climate stabilization strategy. Detailed cost
analysis is also needed for most of the
technical reduction options identified to
support policy decisions in the future.
Solar photovoltaic technology has
been improving rapidly over the last decade.
Continuing or accelerating this progress could
bring this technology into widespread
commercial viability early in the next century.
Biomass conversion technologies
that could make substantially greater
contributions currently exist. Commercial
demonstrations of some existing technologies,
additional research on advanced biomass
conversion technologies, and improvements in
biomass productivity could greatly expand the
role of biomass energy.
Nuclear fission does not currently
appear viable in many countries because of
concerns about safety, waste disposal,
proliferation, and cost. Research is underway
in several countries to develop and
demonstrate "second generation" fission
technologies, which reduce cost and safety
concerns. The establishment of waste disposal
plans acceptable to society is also an area of
intense study in several countries already
committed to nuclear fission. Satisfactory
resolution of these problems could expand the
role of nuclear fission in future decades.
Energy storage technology could
play a crucial role in integrating intermittent
technologies such as solar and wind into
energy supply systems. A number of
promising concepts are currently under study.
Accelerating research and testing to reduce
cost and to improve performance of storage
technologies for electrical energy could greatly
expand the potential roles of some alternative
energy sources.
Hydrogen energy systems offer a
long-term potential for reducing or eliminating
CO2 emissions, if the hydrogen is produced
from non-fossil energy inputs. Hydrogen is
not a primary energy source but rather an
"energy carrier," an intermediate form like
electricity. As an energy carrier, it can help
resolve some of the energy storage issues with
renewables and substitute in some existing
fossil-fuel applications. Research needs
include improved conversion processes using
solar, hydroelectric, nuclear, wind, or other
renewable energy inputs. Additional concerns
include transmission and storage and also
applications to transportation, space heating,
industrial processes, and other end uses.
Research in energy efficiency
could be helpful in accelerating the rate of
improvement and ensuring continued
improvements over the longer term. Industrial
technology, for example, could be developed to
the extent that developing countries and
Eastern Europe could substantially increase
their standards of living without producing the
enormous increases in CO2 emissions that
accompanied this development in the OECD.
Further research to improve efficiency of
automobiles and other vehicles could make a
significant long-term contribution. Also
potentially effective would be a major
cooperative research effort to adapt advanced
technologies that are being developed in the
OECD to the particular constraints and needs
of the rapidly industrializing areas.
Agricultural research to identify
and develop alternative rice production
systems, which reduce the production of
methane, could play a significant role in a
long-term solution to the greenhouse problem.
Similarly, improvements in productivity and
other technological options for reducing
methane emissions from domestic animals
(cattle, sheep, etc.) are possible. Concentrated
research in these areas could make a major
long-term contribution toward reducing
greenhouse emissions.
V-4
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Chapter V: Technical Options
INTRODUCTION
This chapter describes a wide variety of
alternative technologies and other means by
which greenhouse gas emissions from man-
made sources could be reduced. It builds on
the discussion in the previous chapter
describing major sources of greenhouse gas
emissions in some detail. The catalogue of
technical options presented here provides a
background for the development of scenarios
that are presented in Chapter VI to illustrate
the effects of possible combinations of
emission reduction options over time. A
range of policy actions that might be taken to
implement various technical measures for
reducing emissions are described in Chapters
VII and VIII, which address domestic and
international policy, respectively.
The preceding chapters discuss the
diverse sources and economic activities
responsible for greenhouse gas emissions. It
should not be surprising, therefore, to find
that there is an equally diverse array of
methods for reducing greenhouse gas
emissions. The primary means of
accomplishing this goal is the development
and use of technologies that reduce energy
requirements (i.e., improve energy efficiency),
use less carbon-intensive fuels, or replace or
reduce emissions of other greenhouse gases.
In addition to this technological approach,
there are also several areas in which
management strategies are the means of
reducing greenhouse gas emissions,
particularly with respect to the buildup of
gases resulting from some agricultural
practices and the use of forest resources.
In general, technical options presented
in this chapter assume that the level of
consumer services remains constant. For
example, technical options are presented that
could dramatically reduce the energy
consumed per square meter of residential
buildings. It is assumed, however, that the
number of square meters of residential space
per capita would not change as a result of
implementation of any technical measures.
Obviously, policies could be implemented that
encouraged smaller homes, smaller or fewer
cars, less consumption of greenhouse gas-
intensive goods, etc. Such policies could be
effective in reducing emissions, but involve
potentially difficult tradeoffs with standards of
living or lifestyles. It is not the intent of this
report to argue for or against such tradeoffs.
Rather, the focus of this report is on
identifying those emissions reduction measures
that could be implemented with minimal
impact on lifestyles. This appears to be a
logical first step in the policy evaluation
process.
The Role of Long-Term and Short-Term
Options
In the time frames considered in this
report, long-term options become critical. In
order to stabilize or reduce the concentrations
of greenhouse gases, new sources of energy
supply and dramatic improvements in
efficiency will be necessary. However, there is
also much that could be done to reduce
greenhouse gas emissions over the next
decade by improving energy efficiency, making
greater use of natural gas, reducing use of
chlorofluorocarbons (CFCs), promoting
reforestation and other applications of
available technologies and techniques.
While the current generation of
technical measures will not be sufficient to
stabilize global greenhouse gas emissions
several decades hence, efforts to adopt such
technologies are exceedingly valuable for
several reasons. First, reducing the rate of
growth in global emissions now would make
it easier to stabilize concentrations in the
future because of the long atmospheric
lifetimes of greenhouse gases. Second, short-
term strategies are often intermediate steps
toward long-term strategies; for example,
implementation of currently-available
efficiency improvements will encourage the
development of future efficiency
improvements. Finally, the incentives
necessary for longer-term strategies, such as
emission fees on carbon-intensive fuels, will
generally be consistent with short-term
strategies.
Over the long term, the most important
options are advanced, non-fossil energy
technologies, combined with major
breakthroughs in end-use technology that
would drastically reduce energy requirements.
Also, changes in agricultural and forest
management technologies could become
V-5
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Policy Options for Stabilizing Global Climate
important. In addition to the incentives that
may flow out of short-term strategies, it is
important in the short term to promote
research and development by governments,
and the identification and advancement of
promising long-term technologies by the
private sector.
The Economics of Control Options
For several reasons, this report does
not attempt either a detailed comparison of
the economic cost of specific emission
reduction options or an assessment of the
aggregate cost of entire emission reduction
scenarios. For one thing, the analysis
presented in this report is, of necessity, global
and very long-term. It is very difficult, if not
impossible, to produce credible estimates of
global costs of policy scenarios. Similarly, it
is of questionable value to project costs of
alternative policy actions or particular
technologies more than a hundred years into
the future. A primary focus of this chapter is
to identify techniques that appear promising
today but are not yet widely accepted in
today's markets. As discussed above, the need
to foster new technological developments is
necessary because of the long-term nature of
the problem. The future costs of currently
emerging technologies are inherently
unknowable now.
It is more appropriate to begin serious
cost analyses on a country-by-country basis
and over a time horizon of a few decades. A
number of such cost studies are underway
now in the United States Environmental
Protection Agency (U.S. EPA) and other U.S.
agencies as well as in other countries. Even
when limited to individual countries and
shorter time horizons, however, many
difficulties remain in evaluating costs of
alternatives. For example, the cost of some
options is difficult to evaluate partly because
the absence of a market for reducing the risks
of climate change has meant relatively little
effort toward research and development.
The recent rapid development of
substitutes for CFCs demonstrates the
importance of creating a market incentive to
improve technology and reduce costs. Until
it became apparent that environmental
regulation would create a market for CFC
substitutes, industry reported that there were
few feasible options at any price. Now, an
intensely competitive race to commercialize
substitutes is underway around the world at
costs orders of magnitude below estimates
from just a few years ago.
Similarly, current prices may not
accurately reflect costs since climate change is
a potential major cost not currently reflected
in the cost of goods and services. As
discussed in Chapter VII, it may be desirable
to incorporate the risk of climate change into
markets through the imposition of carbon fees
or other policies, in which case currently
more expensive options may become more
competitive.
A detailed economic analysis of options
discussed in this report has not been
attempted for all of the reasons discussed
above. It is worth noting, however, -that
anecdotal information and partial analyses
cited in this chapter indicate many of the
near-term reduction options are economically
justified, or nearly so today, even based on
current prices. This is particularly true for
measures to improve energy efficiency, where
substantial opportunities for cost saving
investments exist despite recent progress.
Chapter VII discusses these opportunities as
well as some of the current constraints to
their implementation.
Worldwide Emissions and Control Techniques
Figure 5-1 shows the contribution to
global warming, by trace gas and by sector.
Figure S-la identifies the "greenhouse gases"
and illustrates their estimated percentage
contributions to the greenhouse effect in the
1980s. All of these gases are produced
through a diverse range of human activities,
which we have classified into five broad
categories. Energy-related activities have been
broken down into two categories:
"applications" of energy, that is, energy
services, or "end uses," and the production of
energy, or energy supply. Other emissions-
producing activities are related to industry,
which include the use of CFCs, forestry
(particularly deforestation), and agriculture.
Often a single broad category of activity -
fossil energy consumption, deforestation, for
example - contributes to several of the gases
V-6
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Chapter V: Technical Options
FIGURE 5-1
CURRENT CONTRIBUTION TO GLOBAL WARMING
(Percent)
(a)
(b)
By Trace Gas
Other (13%)
CFC-11 &-12
(14%)
N2O
(5%)
C02 (49%)
CH4(19%)
By Sector
Other Industrial (3%)
Forestry (8%)
Agriculture (15%)
Other CFCs (3%)
CFC-11 (4%)
CFC-12(10%y
Energy (57%)
V-7
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Policy Options for Stabilizing Global Climate
of concern. Figure 5-lb shows the
proportions that the major categories of
human activity contribute to global warming.
As the modeling results in the next
chapter make clear, the U.S. is likely to
account for a declining share of future
greenhouse gas emissions. Stabilizing
concentrations will require control options
applicable to the needs of other countries,
particularly developing countries with very
different resources. The special conditions in
the Soviet Union and Eastern Europe may
also require somewhat different technical
approaches. Some technologies, such as more
efficient lighting, are relevant to virtually all
parts of the world, but other needs vary
considerably. This chapter therefore discusses
improved cookstoves, strategies for arresting
tropical deforestation, and other options of
particular relevance to developing countries.
It also identifies special needs in the USSR
and Eastern Europe such as improvements in
existing district heating systems and the
industrial infrastructure. Table 5-1 illustrates
some of the promising options for various
regions under near-term and long-term time
horizons.
Organization of this Chapter
Because of the enormous amount of
information presented in this chapter (in
truth, a separate chapter could be devoted to
each major source category discussed here),
we have departed somewhat from the format
used throughout the rest of this Report to
Congress and divided the remainder of this
chapter into five parts.
The first two parts discuss energy-
related activities. The single most important
determinant of greenhouse gas emissions is
the level of energy demand and the
combination of sources used to supply that
energy. Energy use causes, in different
proportions, emissions of five important gases:
carbon dioxide (CO2), carbon monoxide (CO),
methane (CH4), nitrous oxides (N2O), and
nitrogen oxides (NOX). Energy use is
integrally linked with virtually all forms of
economic and recreational activity within
industrialized countries. In developing
countries, current biomass energy use
contributes to greenhouse gas emissions, and
potential increases in commercial energy use
could be the largest source of increasing
greenhouse gas emissions in the future.
Thus, evaluation of the options for
reducing greenhouse gas emissions from
energy use must begin with a systematic
analysis of all aspects of energy use.
Although there are "end-of-pipe" control
options for removing some of the relevant
emissions from energy use, while leaving the
basic process intact, the potential impact of
such approaches is very small relative to the
magnitude of the overall problem. Given the
dominance of fossil fuels as a source of
greenhouse gas emissions, technologies to
reduce use of fossil fuels must play a central
role in any effort to stabilize concentrations.
Accordingly, a major focus for policies to
reduce emissions, discussed in Chapters VII
and VIII, must be to promote demand-side
measures that reduce total energy demand and
supply-side measures that promote less
carbon-intensive fuels. Technologies to
achieve these goals are a major focus of this
chapter.
PART ONE: ENERGY SERVICES
reviews the basic applications for which
energy is ultimately used and the
opportunities for reducing greenhouse
emissions at the point of end use. PART
TWO: ENERGY SUPPLY reviews energy
supply, conversion activities, and related
opportunities for reducing emissions. This
includes improvements in efficiency in energy
conversion and distribution and the potential
for increasing supplies of non-fossil energy
sources. Also discussed are reductions in
emissions of CH4 from coal mining and
natural gas production and distribution.
PART THREE: INDUSTRY discusses
technical options for controlling emissions
from industrial activities. Non-energy
industrial activities contribute to greenhouse
wanning in three significant ways. First and
foremost, industrial activities are the source of
all CFC emissions. As discussed in
Chapters IV and VIII, an international
process is already underway to reduce global
emissions of CFCs because of their role in
depleting the stratospheric ozone layer. This
V-8
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Chapter V: Technical Options
TABLE 5-1
Key Technical Options By Region and Time Horizon
Region
Near Term (by 2010)
OECD
Energy Efficiency - autos, lighting, space heating
CFC Controls
Reforestation
Technology Development
Developing Countries
Energy Efficiency -- industrial processes, transport
Low-Carbon Energy -- hydroelectricity, biomass, natural gas
Reversing Deforestation
Eastern Europe
Energy Efficiency - industrial processes, space heating,
transport
Natural Gas
Non-fossil electricity
All Regions
Long Term
Alternative Fuels -- biomass, solar, nuclear, hydrogen
Agriculture - rice production, animals
Forest Plantations
V-9
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Policy Options for Stabilizing Global Climate
chapter discusses the technical potential for
reducing CFCs beyond the level required
under the current protocol.
A second source of industry-related
emissions are landfills, which produce
emissions of CH4. This source category
represents a small portion of total methane
emissions, but emissions from this source
could increase rapidly in the future. Finally,
production of cement produces CO2 as a
process emission (in addition to CO2
produced by energy consumption). This again
is a small component of total CO2 emissions
currently, but the percentage contribution
from cement production has been growing
rapidly in recent years.
PART FOUR: FORESTRY examines
current forest management practices (resulting
in a net annual loss of biomass), which
account for a significant share of emissions of
CO2 and CO as well as some portions of
other gases. It should be noted that the
importance of forestry is greater than its
percentage contribution to global warming as
implied in Figure 5-1. Forests are the only
category that, over time, can be shifted from
a source to a major sink for carbon. It is
technically possible, though by no means
simple, to reverse the long-term trend of
global deforestation and to begin increasing
the amount of forested lands. There are
several components to reforestation strategies
that need to be considered. For example,
reductions in demand for forest products (e.g.,
fuelwood) in some areas may be necessary to
relieve the pressures that have caused
deforestation in recent years.
PART FIVE: AGRICULTURE
examines the technical options for reducing
emissions resulting from agricultural activities,
which are an important source of CH4, N2O,
NO,p and CO. The principal activities of
interest are rice production, enteric
fermentation in domestic animals (primarily
cattle, sheep, etc.), fertilizer use, and biomass
burning. It is apparent that considerable
flexibility exists, particularly over the long
term, to alter agricultural practices in the
specific categories that constitute the large
emitters, but the technical potential is difficult
to quantify.
In general, most of the research and
analysis of agriculture to date has focused on
opportunities for improving productivity.
Productivity improvements should
automatically lead to some reductions in
greenhouse gas emissions per unit of output;
however, this relationship is not well
quantified. Additional options for reducing
emissions, beyond productivity changes, can be
envisioned for each of the specific
categories mentioned, though, again, very
little work has been done as yet to quantify
the potential effects and costs of such options.
Limitations
In this review the information
presented, although somewhat detailed, can
only begin to illustrate potential technical
options that currently appear most promising.
The analysis also highlights the uncertainties
and need for further study of many options.
In some cases, the impact of specific
technologies cannot be estimated at present,
for example, technologies for reducing
emissions from agricultural sources. In
general, however, there are fewer uncertainties
about how to achieve emission reductions
than there are about the rate of warming,
change in climate, and the ultimate effects of
an increase in greenhouse gas concentrations.
While some currently emerging technologies
may not fulfill current expectations, the
options are sufficiently diverse that we can
encourage the development and use of
technologies that are relatively less intensive
sources of greenhouse gas emissions if we so
choose.
The source of most of the
uncertainties discussed in this chapter is the
difficulty of predicting future technological
developments. Many of the options that may
have the greatest impact on the buildup of
greenhouse gases, such as the development of
new engine technology for cars, new designs
for nuclear plants, and the use of hydrogen as
a substitute for liquid fuels, are long-term
possibilities that require substantial further
research. It is important to recognize several
key limitations:
• The discussion cannot deal
exhaustively with the tremendous range of
V-10
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Chapter V: Technical Options
technical options that have been identified in
the areas of energy efficiency improvements,
fuel substitution, industrial emissions
reductions, forest management, and
agriculture.
• Because of the limited
information available, but even more so
because of the extensive scope of this study
(in terms of emissions-producing activities as
well as the global diversity of emissions), it
was not possible to provide detailed
quantification of expected emissions
reductions and costs for many of the technical
options discussed.
• Much data development and
detailed analytical work remains to be done.
A more detailed technical assessment of U.S.
emission reduction options and costs, also
mandated by Congress, is now underway and
will be completed in 1990 by the U.S.
Department of Energy and U.S. EPA.
• Estimates of the potential perfor-
mance of technical options, as discussed la
this chapter, are often based on engineering
design calculations, prototype performance,
laboratory results, etc. Actual achievable
performance may be less, in practice, since
mass production often requires some
engineering compromises relative to
laboratory or prototype specifications. Also,
performance of technology under conditions
of day-to-day use often deteriorates somewhat
from design or new product performance. On
the other hand, currently unforeseen
developments may improve performance
beyond levels estimated today.
• This chapter identifies and
attempts where possible to quantify technical
potentials for reductions in greenhouse gas
emissions. Even where technical options
appear economically attractive on a life-cycle
basis, there are generally institutional,
behavioral, and policy constraints that
currently operate to limit their market
penetration. The portion of identified
technical potential that can be achieved in
practice is largely a function of the availability
and effectiveness of policy options, as
discussed in Chapters VII and VIII.
V-ll
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Policy Options for Stabilizing Global Climate
PART ONE: ENERGY SERVICES
The services that energy provides (also
often referred to as end uses), such as lighting
and fuel-driven locomotion, are an integral
part of human society and, at the same time,
constitute the largest category of greenhouse
gas emissions. While the production and
conversion of primary energy (e.g., coal, oil,
gas) is the immediate source of a large
portion of energy-related greenhouse gas
emissions, it is the application of this energy
to provide specific services that justifies this
production and conversion. Thus, minimizing
the energy required to provide various
services or using non-fossil fuels in specific
end-use applications can reduce production-
and conversion-related emissions as well.
For convenience, energy services are
classified as belonging to one of three major
sectors: transportation, residential/
commercial, and industrial (including
agriculture). Each of these sectors uses
energy in distinctly different ways and offers
different opportunities for reducing energy use
and/or shifting to alternative fuels. Figure 5-2
shows the relative contributions of the three
sectors to global energy use as of 1985.
Figure 5-2a shows the secondary energy
actually consumed at end-use points. Figure
5-2b shows the energy use by sector in
primary energy production equivalent terms;
that is, the production, conversion, and
transmission losses are ascribed to the end-
use sectors based on the characteristics of the
energy they use. Figure 5-2c shows the
proportions that the equivalent primary
energy use for these three categories
contributes to global greenhouse emissions in
the 1980s. The differences are due to the
variations in greenhouse gas emissions from
the different primary energy sources.
There are two time horizons that are
useful in discussing technical options for
energy services. Near-term options refer to
technologies currently available or expected to
be commercially available by the year 2010.
These are the options about which
information is available; such information
could provide a basis for near-term policy
action. Long-term options are those that are
not expected to be available until after 2010
and, in some cases, well after.
An attempt is made to hypothesize
about potential technological developments
over the longer term and to discuss the role
research could play in accelerating the
availability of advanced options. Some of
these technologies are speculative and require
additional research. They are included in the
analysis because they have the potential to
play major roles in the long run.
In discussing global energy-use patterns,
it is important to distinguish between modern
and traditional energy forms, particularly in
order to understand energy use in developing
countries. For this discussion, the terms
modern or commercial energy are used to
describe all fuels and energy forms that are
priced and sold in energy markets (or, in the
case of centrally-planned economies,
accounted for and valued in national
economic planning). In this category are
virtually all of the fossil fuels, which are the
major source of greenhouse gases, as well as
electricity from all sources. Readily available
energy statistics, which pertain almost
exclusively to modern energy, accurately
represent energy-use patterns in industrialized
countries.
For developing countries, however,
traditional energy accounts for a substantial
fraction of the total energy used. This type of
energy includes fuels such as firewood,
agricultural waste, and animal waste that are
gathered and used informally, usually without
being priced and sold in commercial energy
markets.
Technical options, especially in the near
term, vary substantially from region to region
and often among individual countries. For
each of the sectors discussed in this part
(transportation, residential/commercial, and
industrial), we look first at near-term options,
V-12
-------
Chapter V: Technical Options
FIGURE 5-2
GLOBAL ENERGY USE BY END USE
1985
(a) Secondary Energy Use (b) Primary Energy Equivalent
Transportation
27%
44%
industrial Transportation
20%
Industrial
47%
Residential
Commercial
29%
Residential
Commercial
33%
(c) Contribution to Warming
Other CFCs (3%
CFC-11(4%
CFC-12(10%)
Agriculture
15%
Transportation Energy Use
18%
Forestry
8%
Other Industrial
3%
Industrial Energy
Use 25%
Residential/Commercial
Energy Use 14%
v-13
-------
Policy Options for Stabilizing Global Climate
for industrialized countries, developing
countries, and the USSR and Eastern Europe,
then briefly discuss the long-term options.
The industrial market economies, the
members of the Organization for Economic
Cooperation and Development (OECD), have
many similarities in terms of economic
activities and resources, and hence are
discussed as a group. Energy use in these
countries is relatively high but not expected to
grow rapidly; rising incomes are being devoted
increasingly to products that do not require
significant energy inputs.
The developing countries are vastly
different from industrialized countries both in
current levels and types of economic activities
and available resources. Energy use in the
developing countries will grow significantly in
the future, but there is great uncertainty
about the rate of growth.
The USSR and Eastern Europe share
with most developing countries a much
greater emphasis on government intervention
in economic planning and industrial activities
than occurs in OECD countries. On the
other hand, these countries have massive and,
in many ways, technologically sophisticated
industrial infrastructures that are in some
ways more similar to those of the OECD
countries than they are to the industrial
infrastructures of most developing countries.
Energy use in Eastern European countries
(and associated greenhouse gas emissions) has
been growing rapidly and is expected to grow
in the future. While less is known about the
technical potential to reduce emissions in
these countries, it is generally believed that
very substantial improvements can be made in
energy efficiency.
TRANSPORTATION SECTOR
Transportation currently consumes
approximately 27% of global modem energy
use. Virtually all of the energy used in
transportation is derived from oil. In 1985 in
OECD countries, energy used for
transportation accounted for about 23% of all
energy consumed (27% in the U.S.), expressed
as primary energy equivalents. As a share of
secondary energy consumption, transportation
accounted for about 34% in the OECD,
approximately 97% of which was oil (U.S.
DOE, 1987b).
In industrialized countries it is likely
that the private automobile will continue to
be the primary means of transportation in the
near future. Fortunately, there are near-term
opportunities for improving the efficiency of
this mode of transportation. Near-term
improvements in efficiency of freight transport
and aircraft will also be cost-effective over the
next few decades. A few industrialized
countries (e.g., Canada, New Zealand) are
also pushing ahead with major alternative
fuels programs in the near term.
Over the longer term, additional
reductions in energy consumption may come
from shifting to more efficient modes of
transportation and substitutes for
transportation (e.g., advanced communication
technologies). Also, increasing the use of
non-fossil-based fuels in the transportation
sector is essential in order to greatly reduce
or eliminate greenhouse gas emissions (see
PART TWO: ENERGY SUPPLY).
In developing countries and the USSR
and Eastern Europe, transportation currently
accounts for a smaller percentage of total
energy use. (In some African countries,
however, the percentage is much higher.)
However, in the future, as economies expand
and incomes rise in these regions, the
potential exists for explosive growth in
transportation energy use.
Near-Term Technical Potential in the
Transportation Sector
With aggressive programs to improve
transportation energy efficiency across the
board in industrialized countries, it appears
that significant overall reductions could be
made over time. By 2010 in the OECD,
improvements in the efficiency of light-duty
vehicles and freight transport could reduce
energy use in the transportation sector by
about 7 exajoules (EJ) from expected levels.
If the same efficient technologies were
transferred to developing countries and the
USSR and Eastern Europe, even larger
reductions below expected levels could be
achieved because of the rapid expansion of
vehicle stock in those areas. This suggests
V-14
-------
Chapter V: Technical Options
that the technical potential may exist to
reduce energy use 25 EJ worldwide by 2010.
Furthermore, it appears that there are
alternative fuel options that could be
implemented during this time period, which
could reduce the greenhouse gases emitted
per unit of energy consumed in
transportation. The overall potential of these
options has not been quantified. Near-term
options in the various regions are discussed
below.
Near-Term Technical Options: Industrialized
Countries
Within the transportation sector,
technical options to reduce greenhouse gas
emissions include improvements in fuel
efficiency, alternative fuel use, stricter and
more universal emissions control,
improvements in urban planning, and greater
use of mass transit.
Increase Fuel Efficiency
Light-duty vehicles, mainly passenger
cars, account for the bulk (about 63%) of
current transportation energy use (see Figure
5-3). Other major contributors are freight
transport vehicles (diesel trucks, ships, and
railroads), accounting for about 25%, and
aircraft, primarily those used in passenger
travel, accounting for 12% of transportation
energy.
Light-Duty Vehicles. In the past decade,
a great deal of attention has been devoted to
options for improving the efficiency of light-
duty vehicles. Consequently, a number of
very promising approaches have been
identified and well-documented (see Bleviss,
1988; Goldemberg et aL, 1988, for more
extensive discussions of the technical options
for improving the fuel efficiency of light-duty
vehicles). These efficiency improvements
must be considered in the context of several
societal and consumer concerns related to
light vehicles, such as urban air quality, safety,
comfort, and performance. These other goals
also affect the patterns of vehicle technology
development.
Although average fuel efficiency for
new cars in the industrialized countries is
between 25 and 33 miles per gallon (mpg), or
7.7-10 liters («)/100 kilometers (km) (IEA,
1987), several vehicles that are roughly twice
as efficient are commercially available: the
Honda Civic and the Chevrolet Geo Metro
both average greater than 50 mpg (5
-------
Policy Options for Stabilizing Global Climate
FIGURE 5-3
COMPONENTS OF TRANSPORTATION ENERGY USE
INTHEOECD: 1985
(P*rc*nt)
Dl»t«l (Primarily
Trucks, 20%)
Gaaolin* (Primarily Paaa«ng*r
Car* and Light Truck*. 83%)
Source: OECO, 1»8T.
V-16
-------
Chapter V: Technical Options
TABLE 5-2
High Fuel Economy Prototype Vehicles
Company
Model
Number of
Passengers
Aerody-
namic Drag
Coefficient
Curb Weight
(Ib)
Maximum
Power
(hp)
Fuel
economy
(mpg)
Genera!
Motors
TPC
(Gasoline)
2
.31
1040
38
61 City
74 Hwy
British
Leyland
ECV-3
(Diesel)
4-5
.24-.2S
1460
72
41 City
52Hwy
Volkswagen
AUTO 2000
(Diesel)
4-5
.25
1716
53
63 City
71 Hwy
Volkswagen
VW-E80
(Diesel)
4
.35
1540
51
74 City
99 Hwy
Volvo
LCP2000
(Diesel)
2-4
.25-.2S
1555
52,88
63 City
81 Hwy
Renault
EVE+
(Diesel)
4-5
.225
1880
50
63 City
81 Hwy
Renault
VESTA2
(Gasoline)
2-4
.186
1047
27
78 City
107 Hwy
Peugeot
VERA+
(Diesel)
4-5
.22
1740
50
55 City
87 Hwy
Peugeot
ECO 2000
(Gasoline)
4
.21
990
28
70 City
77 Hwy
Ford
(Diesel)
4-5
.40
1875
40
57 Cily
92 Hwy
Toyota
AXV
(Diesel)
4-5
.2<>
1430-
Targel
56
89 City
1 10 Hwy
Source: Bleviss, 1988.
V-17
-------
Policy Options for Stabilizing Global Climate
to assume that fuel economy levels achieved
by prototypes could be readily achieved by
production vehicles in the near term. On the
other hand, the prototypes do illustrate that
a wide range of technologies exist to improve
on today's fuel economy levels.
Box 5-1 outlines several examples of
the many automobile fuel-efficiency
improvements already possible with current
technology. Research is proceeding rapidly
and will undoubtedly yield further
opportunities for improved fuel efficiency in
the next decade. It is clear that opportunities
exist for major reductions in light-duty fuel
use by the end of this century. This is
particularly true for the United States, which
is still behind most other industrialized
countries in the average fuel efficiency of new
cars sold (see Table 5-3), partly because of
BOX 5-1. Technologies for Automotive Fuel Efficiency
Weight Reductions - Many of toe most efficient cars substitute
non-traditional materials for steel to achieve weight reductions,
which contributes to their superior operating efficiency. Much
greater weight reduction appears possible by substitution of
high-strength steels, aluminum, plastics, ceramics, and
composite materials (Bleviss, 1988).
Aerodynamic and Drag Improvements - In 1979 the average
"coefficient of drag" (CD) for the US. was 0.48, and for Europe,
0.44. Currently, some production models such as the Ford
Sable and Taurus, Subaru XT Coupe GL-10, and Peugeot 405
achieve a CD of 0.3 or less. AD experimental prototype, the
Ford Probe V, has achieved a CD of 0.13? (Bleviss, 1988).
Incorporating some of the prototype design features could
reduce drag for production vehicles significantly over the next
decade. Rolling resistance is being reduced with advanced
radial tires. General Motors has recently introduced a "fourth
generation'1 radial tire that reduces rolling resistance by 10-12%
from the previous generation. An Austrian company has
developed a more advanced tire concept, a licjuid-injection-
tnolded (LIM) poiyurethaae tire. Preliminary tests indicate
improvements in roiling resistance as well as tread mileage
(Bleviss, 1988).
Engine and Drive Train Improvements - Several researchers
have identified a number of improvements to conventional
light-vehicle propulsion systems and transmissions that couW
dramatically increase efficiency (see Bleviss, 1988; von Hippel
and Levi, 198$ Gray, 1983; OTA 1982). One interesting
example is the use of continuously variable transmissions
(CVT), which eliminate some of the energy losses during
shifting and allow the engine to be operated closer to Ml load
at varying speeds. Another possible innovation is an engine-off
feature with energy storage capability during Idle and coast. In
addition, advanced engine designs currently in prototype could
be much more fuel efficient than current technology. One
example is the adiabatic diesei engine shown to Box 5-2.
V-18
-------
Chapter V: Technical Options
TABLE 5-3
Actual Fuel Efficiency for New-Passenger Cars
(Gasoline consumption in liters per 100 kilometers)
Projections/Targets
Australia
Canada
Denmark
Germany
Italy"
Japan
Netherlands
Sweden
United Kingdom
United States
a 1987 target.
b 1995.
c 1975.
** nrtitf» fimir^c fr\r
1973
NA
NA
9.0°
10.3
8.4
10.4
NA
NA
11.0
16.6
Ttalv r^nm
1978
11.8
11.5
NA
9.6
8.3
8.8
9.2
9.3
9.1
11.8
*c**nt ot/4*ra A*
1979
11.2
11.5
NA
9.4
8.3
8.6
8.9
9.2
9.0
11.6
» tf»ffir»i*>n/n/ e
1980
10.1
10.3
8.6
9.0
8.1
8.3
8.8
9.0
8.7
10.0
if tho trttal ,
1982
9.8
8.5
NA
8.3
8.3
7.7
8.5
8.6
8.1
8.9
r>ar fli»i>t
1983
9.5
8.5
7.3
8.0
8.0
7.8
NA
8.6
7.9
9.0
1984
9.5
8.4
7.0
7.7
NA
7.8
8.5
8.8
8.9
1985
8.2
7.1
7.5
7.8
7.8
9.1
8.5
7.6
8.7
1990 2000
8.5a
7.4 6.8-b
7.4
8.6 7.8
8.8 8.2
Source: IEA, 1987a.
V-19
-------
Policy Options Tor Stabilizing Global Climate
the preference for larger cars in the U.S. If
light trucks were included in these averages,
the U.S. would be even further behind most
other OECD countries.
Despite the fact that improvements
have been identified, it is not clear whether,
and at what rate, new technology will be
incorporated into automobile designs.
Clearly, opportunities for dramatic efficiency
improvements exist, but costs associated with
these opportunities must be considered.
Several years ago, the U.S. Office of
Technology Assessment (OTA) conducted a
detailed analysis of the potential for and cost
of future improvements in the fuel efficiency
of new automobiles. The study, which was
based on extensive interviews with automobile
manufacturers and other fuel-efficiency experts
found that it was technically feasible to
achieve average new-car fuel efficiency in the
range of 50-70 mpg (3.4-4.7 2/100 km) by
2000. It also found that "the consumer costs
of fuel efficiency range from values that are
easily competitive with today's gasoline prices
to values that are considerably higher" (OTA,
1982).
OTA found that the projected cost of
efficiency improvements varied considerably,
depending on the actual performance of
potential design changes, whether production
techniques to hold down variable cost
increases are successfully developed, and the
value consumers place on future fuel savings.
Under optimistic assumptions, OTA estimated
the cost of fuel efficiency measures to be as
low as $60-5130 per car during the 1985-2000
time period. Under alternative assumptions,
the cost of efficiency improvements could be
as high as $800-52,300 per car.
Von Hippel and Levi (1983) conducted
a computer analysis of the cost of introducing
a number of specific measures that would
improve fuel efficiency, beginning with the
1981 Volkswagen Rabbit diesel. A package of
specific improvements that would improve the
fuel economy from 5.2 to 3.3 «/100 km (45 to
71 mpg) was estimated to cost about $500 per
car.
Goldemberg et al. (1988) and Bleviss
(1988), however, suggest that cost estimates
toward the lower end of the OTA range are
more likely for several reasons. First, the
efficiency improvements would yield a number
of other benefits to the consumer.
Alternative materials, for example, could also
reduce maintenance costs. There is also some
anecdotal evidence that, contrary to popular
expectations, use of more plastics and plastic
composites may in some cases increase
passenger safety (Bleviss, 1988). In other
cases, alternative materials may reduce safety.
The inclusion of the engine-off feature may
prolong engine life. If the value of these
other benefits is deducted from the cost of
fuel-efficiency improvements, more rapid
improvements may be cost-effective.
A second reason for lower cost
estimates is that the cost of individual
improvements may not be additive. Some
costs may be offset by the savings from
combining measures and integrating a number
of related changes into ongoing production
process changes. Vehicle manufacturers
periodically make major investments in design
changes, incorporating style concerns as well
as engineering improvements. Chrysler
recently conducted a study comparing the
costs of producing a conventional steel vehicle
and an alternative made principally of
composite plastics. Although the composite
material is more costly, its use allows a
dramatic reduction in the number of parts
and hence, assembly costs. The study
concluded that the number of parts might be
reduced by as much as 75%, and that the
overall production costs for the composite
vehicle would be only 40% of those for the
corresponding steel vehicle (Automotive News,
1986).
On the other hand, automobile
manufacturers have expressed the view that
further fuel efficiency improvements may be
more difficult and costly to achieve than
estimates from the early 1980s suggest
(Plotkin, 1989). Concerns raised by the
manufacturers include the following:
• Most of the cost-effective
efficiency measures that are acceptable to
consumers have been implemented in the last
decade.
V-20
-------
Chapter V: Technical Options
• Performance of actual production
models incorporating design changes for
efficiency have fallen short of engineering
calculations.
• There . are major technical
uncertainties and marketability problems
associated with many of the fuel-efficiency
technologies (e.g., advanced diesels, two-stroke
engines).
• Real trade-offs do exist between
further fuel-efficiency improvements and
environmental standards (particularly for
nitrogen oxide [NOX] emissions) and safety
standards.
Other recent research on potential fuel
economy improvements has also emphasized
the difficulties of achieving cost-effective
improvements in the near term. For example,
in diFiglio et al. (1989), several constraints on
vehicle efficiency improvements were noted,
including that auto manufacturers require
several years to retool existing production
lines, decisions on production are essentially
locked in already for the next several years,
and the technical acceptability of many
efficiency improvements has not been
demonstrated on many models. Also,
consumer purchasing decisions are affected by
many factors, including vehicle size,
acceleration, braking, maneuverability,
comfort, etc. Nevertheless, diFiglio et al.
pointed out that some efficiency
improvements are cost-effective, even if
vehicle size, performance, and ride quality are
held constant to current (1987) levels. They
noted that new-car fuel efficiency could be
increased 17% (to 31.6 mpg) by 1995 at a net
savings to the consumer (i.e., including fuel
savings using a 10% discount rate over four
years). Additional improvements to surpass
36 mpg would be cost-effective over the life
of the vehicle by 2000 (also see Plotkin 1989).
Fuel Efficiency Tradeoffs. The
governments of many industrialized countries
regulate light-duty vehicles to reduce
emissions of a number of air pollutants. In
addition, consumers value performance
attributes other than fuel efficiency, as well as
comfort, safety, and cost in their choice of
automobiles. To the extent that proposed
fuel-efficiency improvements or alternative
fuels involve tradeoffs against these other
goals, or are perceived to require such
sacrifices, they may be more difficult to
implement.
Safety is a major concern long
associated with light-duty vehicles. Some
industrialized countries regulate the
manufacture, sale, and maintenance of
vehicles to improve safety. In the 1970s and
1980s, U.S. safety standards significantly
improved vehicle safety. Some evidence exists
of a correlation between size and weight
reductions and increases in injury and fatality
for currently available vehicles (OTA, 1982).
Clearly, effects on safety must be considered
in the evaluation of technical alternatives for
improving fuel efficiency.
Weight reductions to improve efficiency
may in fact reduce the structural strength of
vehicles, thus making them less safe. It is not
true, however, that the use of lighter
materials necessarily reduces safety. Early
attempts in the 1970s to improve fuel
efficiency often involved simple weight
reductions throughout a vehicle with
corresponding declines in crashworthiness. In
recent years manufacturers have employed
other methods to achieve weight reductions,
including the use of lighter, composite
materials and changes in body designs that
maintain or enhance structural integrity.
These types of improvements are reflected in
U.S. government crash tests where some
smaller vehicles have consistently shown
superior crash performance to other vehicles
weighing as much as 50% more (Bleviss,
1988). In contrast, some comparatively heavy
vehicles have the lowest crashworthiness
ratings among available models. These crash
tests, however, do not accurately reflect safety
concerns in crashes between vehicles of
different weights.
Weight reductions, aerodynamic design
and engine improvements could also stimulate
increased use of composites, plastic, and other
new materials. Ultimately, these materials
might present new solid waste disposal
problems as the cars are eventually scrapped.
This area should be evaluated in more detail
in the future.
V-21
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Policy Options for Stabilizing Global Climate
Emissions are another major concern
associated with automobiles. Vehicles emit
several pollutants -- particulates, volatile
organic compounds (VOCs), carbon monoxide
(CO), and nitrogen oxides (NOX) -- which
contribute directly to urban air quality
problems and indirectly to climate change.
Some options for increasing fuel efficiency
(and thus reducing greenhouse gas emissions)
have the potential to worsen local air
pollution problems. For example, diesel
engines are more fuel efficient than gasoline-
powered automobiles, but diesel engines tend
to produce greater emissions of particulates
(many of which are cancer-causing
compounds) per mile travelled.
The design of vehicle emission
standards can be another complicating factor.
In most industrialized countries pollutant
emission requirements for vehicles are applied
on a grams-per-mile (or kilometer) basis.
One concern about this approach is that it
may not encourage development of
technologies that would simultaneously
improve fuel efficiency and reduce emissions
of urban air pollutants, even though such
technological options exist (Bleviss, 1988). In
addition, as fuel efficiency improves, the
marginal cost of driving would decline,
assuming fuel prices remain constant, which
might induce vehicle operators to drive more
than they otherwise would. If this effect is
significant, it would offset some of the
expected reductions in greenhouse gas
emissions and could also result in a net
increase in emissions of conventional urban
air pollutants.
Conversely, some of the options for
reducing emissions of pollutants can lead to
increases in emissions of greenhouse gases.
As noted above, switching to methanol fuels
could increase greenhouse gas emissions if the
methanol is derived from coal. Similarly, use
of electric cars might result in net increases in
greenhouse gas emissions if the electricity
were generated from fossil fuels, although
recent evidence indicates that electric cars
would likely achieve a net reduction in
emissions.
There are potential solutions to all of
the problems illustrated. For example, new
diesel cars are much cleaner than earlier
models. Mercedes Benz and Volkswagen have
now developed emission control devices that
make it possible for their diesel cars to meet
the strict California paniculate standard of 0.2
grams/mile (Bleviss, 1988). In addition,
emission standards could be modified (e.g., to
grams per gallon in conjunction with higher
efficiency standards, or direct regulation of
carbon dioxide [CO2] emissions) to encourage
fuel-efficiency improvements that would also
benefit local air quality. Over the long term,
it is important that options like methanol-
fueled and electric vehicles are promoted in
conjunction with non-fossil (or at least low
carbon) energy inputs.
Many consumers are concerned about
sacrificing size, comfort, or driving
performance to achieve major improvements
in fuel economy. On the other hand, many
consumers may also be concerned about the
environmental impacts of their consumption
patterns, and willing to alter those patterns, if
informed of the environmental implications.
Nonetheless, analysts have demonstrated
possible design changes that would reduce
fuel consumption while retaining the size and
performance of a large automobile (e.g.,
Forster, 1983).
Some of the prototype high-efficiency
vehicles have already demonstrated that size
and acceleration do not necessarily have to be
sacrificed. The Volvo LCP 2000, with an
average fuel efficiency of 65 mpg (3.9 {/100
km), accelerates from 0 to 60 miles per hour
in 11 seconds - compared with 13.1 seconds
for the average acceleration of the U.S. new-
car fleet (1986 models, which averaged only
28 mpg [8.4 1/100 km]). Likewise, a recently
developed lightweight prototype car, by
Toyota, is designed to seat five to six
passengers while achieving 80 mpg (2.9 2/100
km) under urban driving conditions (Bleviss,
1988).
In summary, it appears technologically
feasible to achieve average new-car fuel
efficiency of at least 40 mpg (3.8 2/100 km) in
the U.S. by 2000. A new fleet average of 50
mpg (4.7 2/100 km) would be technically
feasible with continuing technical innovation,
size reductions, and vehicle turnover. This
would require a strong commitment by
government and industry, but the reductions
V-22
-------
Chapter V: Technical Options
in energy use, and greenhouse gas emissions,
from this improvement would be significant.
However, a new car fleet average of 40 mpg
by the year 2000 could require size,
performance, and safety reductions. The
length of the development period and
the degree of technical change required-
to achieve a new fleet 50 mpg average
without compromising safety and other
desired product characteristics are highly
uncertain.
The U.S. Department of Energy (U.S.
DOE, 1987c) has projected that automobile
vehicle miles travelled (VMT) in the U.S. will
increase over 50% by the year 2010 (from
1,315 to 2,032 billion miles). In calculating
future transportation energy use, the report
also projects that automobiles will average
about 27 mpg (8.7 J/100 km) in 2010 (overall
average of all operating vehicles, not new-car
average). If automobiles averaged 50 mpg
(4.7 0/100 km), the energy consumed would
be reduced by over 45%, or more than 30
billion gallons of gasoline (3.8 EJ1) in
2010 -- more than a 40% decline from the
1985 consumption level (as opposed to the
7% increase projected by U.S. DOE). To
achieve these results, it would be necessary
for automobiles to perform at the specified
on-road fuel efficiency over the life of the
vehicle. Currently, there is a widening gap
between nominal test values and on-road
performance as well as considerable
degradation in fuel efficiency over the life of
an automobile. These factors require further
study and could limit the expected energy
savings from fuel economy programs.
In addition, the current trend in the
U.S. toward the use of light-duty trucks for
personal transportation could offset some of
the efficiency gains if it continues in the
future. Efficiency improvements in light-duty
trucks and/or programs to discourage personal
use of these vehicles could produce significant
energy savings in the U.S. The recent trend
toward slower turnover of older vehicles could
also offset efficiency improvements if it
continues. Conversely, programs to stimulate
more road turnover and scrappage of older
vehicles could improve efficiency gains.
Decreasing fuel use in the U.S. could also
support many important national goals such
as reducing international trade deficits and
improving energy security. Improvements of
this magnitude could be made for the OECD
as a whole and would undoubtedly also spill
over to the non-OECD countries that produce
vehicles for sale in the OECD and/or import
vehicles or technology from the OECD. Most
light-duty vehicles currently in production are
derived from designs that originated in the
OECD (Bleviss, 1988).
Freight Transport Vehicles. Diesel trucks
use about 14% of the oil consumed for
transportation in OECD countries (von
Hippel and Levi, 1983). Improvements in
efficiency in this sector could, therefore, have
a noticeable effect on total energy use.
Current prototype vehicles could reduce
energy use per ton-mile in the U.S. by as
much as 40% for truck transport (Automotive
News, 1983). Goldemberg et al. (1988) have
estimated that further improvements on the
order of 50% or better could be achieved
with existing technology and at reasonable
cost. Box 5-2 describes one of the most
promising advanced diesel technologies.
OECD truck fuel use for 1985 totaled about
5.3 EJ. A 50% improvement in fuel
efficiency over the next several decades seems
feasible if aggressively pursued. As truck
freight ton-miles are projected to grow in the
future, this level of improvement could save
at least 2.6 EJ by 2010.
Both rail and water transport are much
more efficient than truck transport on a ton-
mile basis. In 1984, the U.S. average energy
intensity of freight movements was estimated
at 1,610 British thermal units (Btu)Aon-mile
for trucks, while waterborne shipping averaged
350 Btu/ton-mile and rail freight was 510
Btu/ton-mile (Holcomb et al., 1987). To the
extent that shippers could be encouraged,
either through price incentives or other policy
mechanisms, to shift from truck transport to
these modes in the future, net energy use for
freight transport could be reduced. One
interesting approach is being tested by
General Motors Corporation (GM). GM has
developed a new truck trailer that can also be
easily converted to a rail car and connected to
a freight engine. This would allow loading of
truck trailers at source points, truck hauling
to the nearest rail terminal, and conversion to
rail without unloading/reloading. Likewise,
near the destination, the transition back to
V-23
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Policy Options for Stabilizing Global Climate
BOX 5-2. Adiabatic Diesel Engine Technology
The diesel engine is currently the most efficient powerplant used in heavy-duty, and some
light-duty, vehicles. Little has changed in its basic design over the years. However,
motivated by the energy crises of the 1970s, engine designers began trying to improve the
fuel efficiency of diesels even further. One of the most promising results of this research
is the adiabatic engine, which combines new structural ceramic materials and
turbocharging to increase the effective use of the heat generated during combustion.
• Adiabatic design, which means "without heat loss," increases efficiency by
retaining heat in the combustion chamber instead of losing it to exhaust
gases and the engine coolant, harnesses the high pressure exhaust gases, and
reduces weight and parasitic power losses by eliminating the normal cooling
system.
• As shown in the figure below, turbocompounding increases the pressure of
gases in the combustion chamber using a turbocharger and then harnesses
the extra pressure of the exhaust gases with a turbine connected to the
engine crankshaft. Structural ceramics, which are being developed to
withstand temperatures and pressures reaching 1000°C and 2000 pounds per
square inch, respectively, will be used to insulate the combustion chamber,
allowing greater thermal efficiency.
• Cummins Engines and Adiabatics in the U.S., as well as Japanese
automakers, are at the forefront of introducing the adiabatic engine both for
heavy-duty trucks and passenger vehicles. A Ford Tempo with an adiabatic
engine is projected to achieve a fuel economy of 80 mpg. Along with the
consequent reduction in CO^ additional reductions are expected in
hydrocarbon, CO, and NOX emissions, and paniculate emissions are expected
to be reduced by as much as 60-80% over current diesel technology (Kamo,
1987).
Turbocturger
Aerodynamic
Exh*i*t Sy*twn
Htgh Soccd
Reduction Gearing
V*relton ttoMfwn
FK*> Couotng)
Power Transfer
To Cr*n*«n*
-------
Chapter V: Technical Options
truck is simple. GM has estimated that for
hauls of over 200 miles, this approach could
reduce energy use to 20% of current energy
use for an all-truck haul or 50% of a
conventional rail shipment (Sobey, 1988).
Improvements in ship fuel efficiency are
also possible. Using some of the same diesel
engine technologies identified for truck
engines, 30-40% improvements in efficiency
may be possible over the next several decades.
Wind-aided cargo ships may also improve
efficiency somewhat in the future.
Aircraft. Dramatic improvements in
fuel efficiency have been achieved in the
airline industry over the past decades. From
1970 to 1980 fuel use per passenger mile in
the U.S. declined by over 40% (Holcomb et
al., 1987). Nevertheless, by 1980 energy still
accounted for about 30% of total operating
costs for commercial airlines in the U.S.
(Goldemberg et al., 1988). Since 1980, energy
intensity has continued to decline due to
some additions of more efficient aircraft and
continued improvements in load factors
(revenue passenger miles divided by available
seat miles ~ U.S. DOT, 1988), but at a slower
rate (from 1980 to 1984 the improvement
was about 4% - Holcomb et al., 1987). The
decline in the rate of efficiency improvement
is highly correlated with declining energy
costs. For example, between 1980 and 1987,
nominal fuel prices declined by nearly 40%
(U.S. DOE, 1988b), reflecting a drop of more
than 50% in real terms. Combined with some
efficiency improvements, this has resulted in
energy costs being reduced to a much smaller
percentage, 10-15%, of total operating costs.
Thus, the economic incentive to reduce energy
intensity has been greatly reduced.
Because of the historical importance of
fuel costs, however, a great deal of research
has been conducted within the industry to
identify opportunities for efficiency
improvements. Currently, commercially
available new planes are more than 25% more
efficient than the 1980 fleet average (Smith,
1981, for 1980 average; Ropelowski, 1982, for
test results of new 757 and 767 models).
Already improvements have been identified
that, if incorporated into aircraft design, could
reduce fuel use per passenger mile to less
than one-third of the current average
(Maglieri and Dollyhigh, 1982; Smith, 1988).
It may be technically possible to reduce fuel
use per passenger mile to 50% of the current
average by the year 2010.
The rate at which airline passenger
miles will increase in the future is, however,
a matter of considerable uncertainty. Some
industry sources are projecting very high rates
of growth in the next few decades, which
could more than offset the projected gain due
to improvements in energy per passenger
mile. Kavanaugh (1988), for example,
projects increases in global jet fuel use of 60-
120% by the year 2025 - despite assuming
significant substitution of more fuel-efficient
aircraft during the same period.
Alternative Fuels
A number of alternative fuels for
vehicles have been proposed in the past few
years. In the U.S. these proposals have been
driven primarily by concerns about the effects
of emissions on urban air quality and the
impact of petroleum-based fuels on energy
security. Only recently have analysts focused
attention on the greenhouse contributions of
alternative fuels. Near-term options of
interest include the use of alcohols ~ both
ethanol and methanol, as blends with
traditional fuels or as complete substitutes -
and direct use of compressed natural gas.
The discussion below refers to dedicated
alternative-fueled vehicles designed and
optimized for the alternative fuel. In the near
term, however, "flexible fuel" vehicles may be
produced; these would be capable of burning
one or more of the alternative fuels as well as
gasoline. In this case, because vehicles are
not optimized, energy efficiency may be less
than optimal (and greenhouse gas emissions
would be higher).
Methanol. Although methanol can be
produced from biomass, in the U.S. and
globally, natural gas would be the most likely
feedstock for methanol in the near term. The
estimated net contribution to greenhouse
gases when natural gas is used as a feedstock
will be roughly equivalent to that from
burning gasoline from petroleum. On the
other hand, greenhouse gas emissions from
the use of coal-based methanol, measured
over the entire fuel cycle, are about double
V-25
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Policy Options for Stabilizing Global Climate
those from crude-oil-derived gasoline
(DeLuchi et al., 1987). A shift from natural
gas to coal in the long run could lead to large
increases in greenhouse gas emissions.
Compressed natural gas (CNG) as a
transport fuel produces fewer CO2 emissions
per unit of energy released than any other
fossil fuel and also seems to be among the
cleanest fuels available when considering its
emissions of other gases that affect urban air
quality (e.g., NOX, CO, and VOCs, although
some questions remain about the level of NOX
emissions from CNG vehicles). However,
leaks of natural gas, primarily methane (CH4),
from the production, distribution, and refuel-
ing processes, could add to the concentrations
of this greenhouse gas. Some researchers
estimate that this increase in CH4 could offset
the advantage of lower CO2 emissions. The
degree to which CH4 releases would increase
or could be controlled is highly uncertain.
CNG is currently used as a transport
fuel in Canada and New Zealand, among
other industrialized countries. In New
Zealand, CNG, liquified petroleum gas
(LPG), and synthetic gasoline (from natural
gas) meet half of the total gasoline demand.
Other industrialized countries have small
alternative fuels programs, mainly based on
CNG, LPG, and methanol (Sathaye, Atkinson,
and Meyers, 1988).
Ethanol. Ethanol is likely to be
produced from biomass but is also likely to
have difficulty competing economically unless
its production is subsidized by government.
Additionally, ethanol production by means of
current technologies relies, on biomass
feedstocks such as corn and sugarcane, which
are also food crops. This competition with
food production raises concerns about the
long-term viability of this approach. As
discussed later, new technology for producing
ethanol from woody biomass may become
commercial and alleviate this concern in the
long term. If fossil fuels are used in the
production process (e.g., in fanning
operations to produce biomass or during
distillation), this could offset the greenhouse
gas benefits of biomass as a feedstock.
In summary, it appears that in the near
term there is limited technical potential for
industrialized countries to achieve reductions
in greenhouse gas emissions from the use of
alternative fuels. The CO2 reductions from
alternative fuels in industrialized countries
would not be enough to offset projected
growth in VMT. However, the use of
alternative fuels in combination with fuel
efficiency improvements may help alleviate
other concerns related to urban air quality
and energy security without increasing the
global warming commitment. As discussed
later, in the longer term, alternative fuels
derived from renewable sources may play a
key role in reducing greenhouse gas emissions
in the transportation sector.
Strengthen Vehicle Emissions Controls
The United States and most other
OECD countries currently regulate the
emission of hydrocarbons (HCs), CO, NOr
and paniculate matter on a gram per
kilometer (g/km) basis. Many developing
countries have recently adopted some
emission control standards as well. The
standards vary for the weight class of the
vehicle as well as by the type of engine.
International comparisons of emissions
standards are difficult because test procedures
vary, but it is generally recognized that U.S.
standards are among the most stringent in the
world. For light-duty gasoline vehicles (which
constitute a majority of the U.S. fleet), the
U.S. standards are 2.1, 0.25, and 0.62 g/km for
CO, HCs, and NOr respectively. Emission
standards in most European countries are
significantly less stringent than in the U.S.
(OECD, 1988). Many developing countries
have much less stringent standards, or none at
all.
Vehicles sold in the United States
control emissions in two steps. The first step •
is to control the amount of pollutants formed
during the combustion process. During
combustion, the primary determinant of the
amount of CO formed is the air/fuel mixture.
As the air/fuel ratio increases, CO emissions
fall. On the other hand, NOX emissions
increase as the air/fuel ratio rises, a result of
the concurrent increase in combustion
temperatures, the primary determinant of NOX
formation. Higher combustion temperatures
are often associated with increased power.
V-26
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Chapter V: Technical Options
An engine designed for greater power will
generally produce higher "engine-out" NOX
emissions than an engine designed for fuel
economy. Electronic engine management
systems, however, have been able to minimize
these tradeoffs, since many of the critical
engine parameters (like the air/fuel ratio) can
be controlled much more precisely (NAPAP,
1987; OECD, 1988).
The second step is to treat the "engine-
out" exhaust after combustion to reduce emis-
sions to the acceptable standard. To control
the "engine out" emissions, both catalysts and
exhaust gas recirculation (EGR) are used on
virtually all new U.S. and Japanese passenger
cars, usually in conjunction with electronic
engine management systems. Since 1981, the
primary catalyst system used on U.S.-bound
cars has been the three-way converter —
named for its ability to reduce emissions of
HC, NOr and CO, as opposed to just one or
two of the gases. Some cars also use a
second oxidation catalyst to catch additional
HC and CO. Catalysts use a variety of
precious metals, including platinum, rhodium,
and palladium, to break down or reduce the
unwanted emissions without causing the
metals themselves to react (Automotive News,
1988; OECD, 1988; White, 1982). EGR
reduces NOX emissions by reinjecting a
portion of the inert exhaust into the engine's
incoming air. The inert exhaust gas cannot
react in the combustion process and reduces
peak temperatures during combustion. As a
result, less NOX is formed. Today, all U.S.
light-duty vehicles have EGR systems
(Husselbee, 1984).
Some tightening of existing U.S.
standards has been considered and determined
to be technically feasible, although probably
expensive on a dollar-per-ton removed basis
(NAPAP, 1987). More significant
improvements in global emissions of NOX and
CO could result from the extension of U.S.
standards to the rest of the OECD and
ultimately, to the rest of the world.
Current technologies for compliance
with U.S. emissions standards have added
substantially to the cost of new vehicles,
although improving technology may reduce
the incremental cost in the future (U.S. EPA,
1985; NAPAP, 1987). Also, with existing
technologies, a modest tradeoff has been
documented between emissions control, and
fuel efficiency and performance, at the current
level of U.S. emissions standards (White,
1982; OECD, 1988). Tradeoffs and cost for
tighter standards, however, would depend on
the stringency of the standards and the level
of technology, as well as the demand for
other characteristics like performance.
Enhance Urban Planning and Promote Mass
Transit
In addition to fuel economy
improvements, some near-term technical
opportunities undoubtedly exist for reducing
VMT in personal vehicles. Programs to
encourage car pooling and use of mass transit
by urban communities may be justified on the
basis of traffic congestion and/or local air
quality benefits, but would also reduce energy
consumption and greenhouse gas emissions.
Similarly, programs to improve maintenance
practices and to modify traffic problems (i.e.,
sequenced traffic lights, one-way streets) to
encourage driving at more efficient speeds,
also have multiple benefits.
Near-Term Technical Options: Developing
Countries
Transportation energy use is a serious
concern in developing countries for several
reasons. Worldwide, energy used for
transportation is almost exclusively from oil.
From 1973 to 1986 oil use by developing
countries increased by 60%. During this same
period, oil use by OECD countries declined
by 13%. Recent projections by the U.S.
Department of Energy (U.S. DOE) indicate
that the overwhelming majority (86%) of
growth in oil consumption in the "free world"
(defined by U.S. DOE to exclude the
centrally-planned economies of Eastern
Europe, the Soviet Union, China, Cuba,
Kampuchea, North Korea, Laos, Mongolia,
and Vietnam) through the year 2010 could
come from developing countries (U.S. DOE,
1987c). The largest component of the
dramatic increases in oil use in developing
countries during the last decade is in the
transportation sector. For IS of the largest
developing countries, about 50% of the
growth in oil consumption in the 1970-1984
period has been in transportation applications
V-27
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Policy Options for Stabilizing Global Climate
(Meyers, 1988). Thus, indications are that
energy use for transportation has been
growing at a very rapid rate in recent years in
developing countries, and this high rate of
growth is projected to continue in the future.
Although some developing countries
have been successful in implementing
programs to reduce fossil fuel use (or at least
oil use) in other sectors, very little attention
has been paid to the transportation sector,
either by these countries themselves or by
international development assistance agencies
(with a few notable exceptions, e.g., Brazil
and, more recently, the Philippines). It is
difficult for developing countries to
implement the technical options that have
been relatively effective to date in the
industrialized countries.
First, information about transportation
energy use is limited in many developing
countries. It is very difficult to estimate, for
example, what portion of the fuel is used in
new versus old vehicles, light-duty trucks
versus heavy-duty trucks, two- and three-
wheeled vehicles, etc. The information that is
available, however, suggests other problems.
The average age of road vehicles tends
to be higher in developing countries for two
reasons. Vehicles tend to be kept in service
longer, and used vehicles from industrialized
countries are often resold to developing
countries. In addition, vehicles are often used
for purposes other than what they were
originally designed for. There is some
evidence that aging vehicles are often poorly
maintained in developing countries. Poor
roads also contribute to increased energy use
per vehicle kilometer of travel (VKT). Urban
congestion can also have this effect, although
in some cases it may also act as a deterrent to
increases in VKT. Although heavily utilized,
mass-transit systems in developing countries
are generally poorly developed and are also
affected by poor or congested road systems.
Thus, the approaches that have been
successful in slowing the growth of
transportation energy use in the industrialized
countries over the past 15 years may not be
as effective in many developing countries.
Industrialized countries have been able to
significantly reduce the average consumption
of fuel per highway mile by replacing existing
vehicles with more efficient newer models and
developing or expanding mass transit in urban
areas. The effectiveness of both strategies in
most developing countries is much more
limited because of the slower turnover of
vehicles and lack of capital to invest in
infrastructure improvements.
On the other hand, it is expected that
as developing countries reach a certain per
capita income, there will be a rapid explosion
in the demand for personal vehicles, which
will dramatically increase transportation
energy use (Sathaye et al., 1988). The fuel
efficiency of new vehicles available during that
period can have a significant effect on future
transportation energy use.
Those developing countries that do not
have domestic oil resources are concerned
that increasing their imports of oil will
diminish the already-limited foreign exchange
available to finance development and hence,
will limit long-term growth. Thus, there is
great interest emerging in limiting oil use for
transportation. Efficiency improvements,
though often more difficult to achieve than in
industrialized countries, clearly are pan of the
solution. Biomass-based alternative fuels are
very important for some developing countries
(Brazil, for example) in the near term. Other
developing countries (like some industrialized
countries) may have natural gas that can be
used for transportation or other types of
biomass-based options. Generally, the
transportation energy solutions that would be
attractive to developing countries for the
purpose of reducing oil imports ~ efficiency
improvements and alternative fuels -- are also
beneficial in reducing greenhouse gas
emissions. One exception is the use of coal
as a rail fuel, which occurs in China and India
and results in both lower energy efficiency in
rail transport and in more CO2 per unit of
fuel consumed. This option may appear
attractive to countries concerned primarily
with minimizing oil imports.
Increase Fuel Efficiency
As individual developing countries
reach a certain level of economic activity and
per capita income, it is expected that the
demand for personal vehicles will "take off,"
V-28
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Chapter V: Technical Options
as occurred historically in several more
industrialized countries. Currently, gasoline
prices are higher in many developing
countries, and oil imports frequently make up
a large fraction of total imports. Therefore,
improvements in the efficiency of new
vehicles, both light- and heavy-duty, should be
very attractive in developing countries to
reduce fuel costs.
Because of capital scarcity, all types of
vehicles are kept in service far longer than
they are in industrialized countries. Certainly
for some developing countries, programs to
improve the quality of maintenance or
accelerate retirement of older vehicles may be
very useful in reducing oil consumption and
greenhouse gas emissions.
For the same reason that aging vehicles
are kept in service, new classes of
intermediate vehicles, often used as low-cost
transport vehicles, have emerged in
developing countries. These are generally
produced locally, often by small companies or
even a single individual. Some alternative
vehicles, notably the Chinese tractor
converted for passenger transport, are
adaptations of vehicles designed for other
purposes. In India also, a significant amount
of road transport in rural areas is
accomplished with tractors. As a means of
passenger or freight transport, many of these
vehicles are very energy-inefficient. The
Chinese tractors, for example, are estimated
to use 75% more fuel than would a 4-ton
truck while carrying only 1 ton; these tractors
account for 27% of the total diesel fuel use in
China (World Bank, 1985). Programs to
improve the efficiency of these vehicles or to
replace them with more efficient alternatives
may be very effective in the near term in
some developing countries.
Alleviate Congestion and Improve Roads
In rural areas of many developing
countries, roads are so poor that traffic must
move much more slowly than is customary for
intercity travel in industrialized countries.
Frequent stops and starts are also a problem
in these areas. These conditions inevitably
lead to reduced energy efficiency regardless of
the quality of the vehicles themselves. A
recent study has concluded, however, that
poor road conditions do not appear to act as
a deterrent to increased vehicle ownership in
rural areas of developing countries (Meyers,
1988). Thus, carefully planned highway
improvements could result in net reductions
in fuel use in some countries. In addition to
reducing fuel use in the existing mix of
vehicles, better roads may allow "upsizing" of
some of the existing traffic to larger trucks
and buses that are much more efficient on a
passenger- or ton-km basis. Encouraging the
use of more efficient modes of transportation,
such as rail transport, may also be possible in
some cases.
In urban areas, congestion is clearly
already a major problem in many developing
countries (as it is in many industrialized
countries) and is likely to become more
severe as rapid urbanization continues in
many developing countries. Although
congestion, as already mentioned, reduces
efficiency in fuel use, it may also act as a
deterrent to increased vehicle use, promoting
the widespread use of more efficient
alternatives to personal automobiles, such as
motorcycles and mass transit. The degree to
which congestion functions as a deterrent to
increased transportation energy use is
uncertain and needs further investigation.
Thus, it is important to carefully
evaluate local conditions in designing
improvements to urban road systems,
including more extensive roads, but also
better road maintenance and road planning.
It may also be important to combine road
improvements with other measures such as
mass transit to achieve overall improvements
in energy efficiency.
Promote and Develop Alternative Modes of
Transportation
In addition to encouraging expansion of
urban mass transit, developing countries may
wish to promote alternatives to highway
transport in both rural and intercity travel.
Because major investments may be required
to develop or improve highways for these
types of travel, it may be more economically
attractive to direct this investment into
improved rail systems, for example, which
move passengers and freight more efficiently.
If highway improvement programs are carried
V-29
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Policy Options for Stabilizing Global Climate
out, however, they may be combined with the
introduction of efficient bus systems, which
would offer an attractive alternative to owning
and using a personal vehicle.
Use Alternative Fuels
Alternative fuels based on locally
available resources may be economically viable
and important options in developing countries
much sooner than is the case for indus-
trialized countries. In countries that have
abundant agricultural land, like Brazil,
commercial technologies to convert crops such
as sugarcane or corn for ethanol production
may make sense (see PART TWO for more
detailed discussion of the Brazilian ethanol
program). A fuels program based on
sustainable biomass production can be
extremely beneficial in reducing net CO2
emissions. However, most developing
countries would have difficulty in diverting
significant amounts of biomass, which is
currently used for food, to energy purposes.
Converting agricultural residues or forest
products to fuel may make more sense if the
conversion processes can be made
economically attractive.
In other countries locally available
natural gas may be readily converted to CNG,
which would reduce emissions of CO2 as well
as many other air pollutants and also reduce
oil imports. A recent review of international
programs noted that most Asian countries and
many Latin American countries that have
domestic gas resources are conducting
feasibility studies of CNG use and many have
pilot programs in place (Sathaye et al., 1988).
Where natural gas is currently vented or
flared as a by-product of oil production, (e.g.,
in the Middle East), the availability of cheap
local oil discourages investments in natural
gas distribution and utilization systems.
A final fuel-switching option that could
be helpful in the near term is replacing coal
with diesel fuel or electricity in rail
transportation systems. Coal is seldom used
anymore as a rail fuel in industrialized
countries - primarily because coal-fired rail
systems are markedly less efficient than the
alternatives. In energy consumed per mile
travelled, diesel trains are more than 3.5 times
as efficient, and electrified rail transport is 13
times more efficient (compared on the basis
of secondary energy consumed). If electricity
is generated from coal, primary energy
consumed is three times greater than the end-
use energy consumed. Electric rail transport
in this worst case would be about four times
more efficient than coal-fired rail transport in
primary energy consumption and net CO2
emissions. However, a few developing
countries with abundant coal resources and
extensive rail systems - notably India and
China -- still use coal in rail transport. India
has a program of gradual replacement
underway, which is expected to eliminate coal
use in rail systems by the year 2000. A shift
to diesel fuel should reduce the CO2
emissions from this source by a factor of five.
Research is also underway to develop
advanced, more efficient technologies for
using coal as fuel in rail transport (Watkins,
1989). This could also reduce CO2 emissions
per mile travelled.
Near-Term Technical Options:
Eastern Europe
USSR and
In the USSR and Eastern Europe,
transportation makes up a much smaller
proportion of total energy use than in
industrialized countries - primarily because
there are many fewer automobiles and trucks.
However, that number is growing rapidly:
from 1970 to 1980 the number of automobiles
in the Soviet Union increased from 1.6 to 6.9
million (a rate of 15%/year), and the number
of trucks rose from 3.2 to 5.1 million
(4.7%/year).
On the other hand, fairly significant
improvements have been made in recent
decades in the efficiency of freight transport,
primarily transport by rail. From 1960 to
1975, ton-kilometers of freight hauled by all
forms of transport in the Soviet Union
increased by 276%, while fuel use increased
by 2.4% and electricity use increased by 418%
(from a very small base). Overall, this
represents a significant increase in energy
efficiency that is primarily due to the
replacement of coal locomotives by much
more efficient diesel and electric engines
(Hewett, 1984).
Given the rapid growth in the numbers
of automobiles and trucks in the recent past,
V-30
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Chapter V: Technical Options
and in the number projected in the scenarios
developed for this report, it appears that an
important option for these countries will be
to increase the efficiency of new highway
vehicles. In addition, because of the large
natural gas resources available in the Soviet
Union (discussed in PART TWO), the
feasibility of using compressed natural gas as
a vehicle fuel may deserve further
investigation.
Long-Term Potential in the Transportation
Sector
The number of technical possibilities
for reducing greenhouse emissions in the
transportation sector increases considerably
over the long term. The range of options
runs from making further improvements in
highway vehicles and expanding the use of
alternative fuels, to using alternative
transportation modes, to developing measures
that would reduce the need for transportation.
All options for the long term are somewhat
speculative and very sensitive to assumptions
about the nature of society in the long term.
The discussion here is intended to illustrate
possible options rather than to suggest
choices.
Urban Planning and Mass Transit
A major concern in many urban areas
throughout the industrialized countries (and
in many developing countries as well) is
increasing traffic congestion. When vehicles
spend an increasingly greater proportion of
their time idling in stop-and-go traffic, they
use more fuel and emit more air pollutants
per mile travelled. In the near term,
solutions to urban congestion problems are
extremely difficult For the long term,
however, alternative approaches to alleviating
this problem will tend to incidentally benefit
the climate wanning problem. Mass-transit
systems not only reduce highway commuter
traffic, but also use much less energy per
passenger mile. Average intensities (over all
time periods) for bus and rail transit are
reported to range from about 2.0-2.5 mega-
joules (MJ)/passenger-km (Holcomb et al.,
1987). At normal commuting times, transit
systems tend to be much closer to fully-
loaded, however, so that the energy intensities
per passenger-mile would be even lower.
Similarly, carpooling can relieve congestion
and reduce fuel use at the same time.
Another possibility is shifting to
smaller, commuter vehicles. General Motors
Corporation is testing a three-wheeled, one-or
two-passenger, narrow, commuter car, which
is essentially more like a covered motorcycle
than a traditional automobile. Because the
vehicle is much narrower than a normal
passenger car, a standard traffic lane could be
split in half to double the carrying capacity of
existing roads. Because the vehicle is small
and aerodynamically designed, it would also
be much more fuel efficient than today's cars,
achieving over 100 mpg (Sobey, 1988).
Clearly, some safety issues and other
complexities in integrating such vehicles into
current urban traffic patterns must be
resolved.
The technical potential exists to design
and construct urban areas that are much more
energy efficient in terms of their
transportation requirements (as well as in
their energy requirements for other end uses).
By comparing cities whose transportation
energy use is very low, relative to global
averages, with cities whose energy use in this
sector is high, it is possible to identify
differences in location patterns, mass-transit
systems, and other factors that can partially
explain the differences in energy demands. In
theory, it should be possible to introduce
incentives that would encourage the more
energy-demanding cities to develop along the
lines of the less energy-demanding cities over
time. This may be especially important in
developing countries where populations,
especially urban populations, are growing
rapidly.
Alternative Fuels
Use of alcohol fuels as an alternative to
gasoline in highway vehicles is an option that
is already receiving considerable interest for a
number of reasons. Technologies currently
exist for producing ethanol and methanol
from various types of biomass. Further
research, testing, and commercial
demonstrations could be helpful in improving
performance and lowering cost In the long
run it appears that production of ethanol
using current grain- or sugar-based technology
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Policy Options for Stabilizing Global Climate
could play only a limited role. Methanol may
be the preferred alternative because its
biomass feedstock does not necessarily have a
food value and therefore is not in direct
competition with food production. Research
is underway to develop and commercialize
technologies for ethanol production from non-
food biomass such as wood, grass, and waste
paper (Lynd, 1989). If these technologies
become cost effective, ethanol may play a
much larger role as a long-term
transportation fuel. (See PART TWO for
more discussion of alternative fuels.)
Technologies currently exist for
operating highway vehicles with hydrogen fuel.
Such vehicles are not currently viewed as
commercial, primarily because of the high cost
of hydrogen fuel and the difficulty of storing
enough hydrogen on board for highway
driving. A hydrogen-powered automobile
built by Daimler-Benz of West Germany and
a hydrogen-powered bus built by the Billings
Energy Corporation of Provo, Utah, are
examples of current test vehicles. These two
vehicles use metal hydride storage tanks, one
promising approach to the storage problem
(Ogden and Williams, 1988). In addition, if
the fuel-efficiency improvements described
above are incorporated, future vehicles may
be able to achieve driving ranges comparable
to today's vehicles while carrying much less
fuel on board. The possibilities for producing
hydrogen at competitive costs are also
improving with the development of solar
photovoltaic technology (see PART TWO).
Another attractive feature of hydrogen
vehicles is that the engines and internal
structure required are very similar to what
CNG-powered vehicles would require. CNG
is already being used in fleet applications in
some countries and will be more widely used
in the future. This could provide a market
for the initial transition to hydrogen when
and if cost and storage problems are resolved.
Electric-powered vehicles have been
discussed for many years as an option for
reducing oil use and/or urban pollution. As
with hydrogen, the problem of storing enough
energy on board to provide a reasonable
driving range is an unresolved obstacle. In
addition, vehicle cost and performance ability
comparable to the cost and performance of
today's vehicles have not yet .been realized.
Concerns about higher future electricity costs
could also retard penetration of electric cars,
even if other problems are resolved.
The source of primary energy for both
electric and hydrogen-powered vehicles will
determine whether a switch to these fuels
increases or decreases greenhouse gas
emissions. Use of non-fossil sources of
electricity, such as solar or nuclear energy,
would decrease emissions of CO2 and other
greenhouse gases. Conversely, use of coal-
fired generating capacity as the primary
source of electricity or hydrogen would
increase greenhouse gas emissions.
Emerging Technologies
Telecommunications may substitute for
many transportation services in the future.
Teleconferencing is already replacing some
types of business travel, although the
magnitude of this substitution has not been
quantified in energy terms as yet. In the
future, as video conferencing equipment
improves and is more widely available, this
option could become more important,
particularly if higher transportation costs and
congestion act as incentives. Catalogue
shopping, electronic mail, electronic
advertising, and electronic banking are other
applications of telecommunications that are
used to accomplish tasks and conduct business
that formerly required travel. A recent
analysis projects that transportation energy
use may decline in OECD countries because
of these substitutions. As is the case with
many energy efficiency improvements, the
motivation for this substitution has very little
to do with energy use. These substitutions
are taking place because consumers and
businesses perceive advantages in convenience,
time saving, access to wider selections, and
cost savings (Schipper et al., 1989).
Fuel cell technology has many potential
applications (described briefly in PART
TWO). Two appealing characteristics of fuel
cells are that cost-effectiveness is not
fundamentally a function of size, as with many
energy technologies and that the cells are
virtually pollution-free at the point of use
(Jessup, 1988). Because of these character-
istics, one possibility is to use small fuel cells
to power highway vehicles. Input fuel can be
V-32
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Chapter V: Technical Options
derived from natural gas, coal, or, ultimately,
renewables-based hydrogen. Several different
fuel-cell approaches are being researched and
tested currently. If they prove economic, the
fuel cell could provide very efficient and clean
power for mobile sources at some point in
the future.
High-speed rail systems are currently in
commercial use in Japan and France. They
compete well with aircraft or automobiles on
a performance basis for some intercity travel.
Energy consumed per passenger-km is
significantly lower than with automobile or air
travel alternatives. As technologies develop
in the future (e.g., superconductors), these
systems could become more efficient and
economically attractive. The primary
constraints appear to be the cost of
constructing the systems and concerns about
safety and rights of way.
RESIDENTIAL/COMMERCIAL SECTOR
In the United States residential and
commercial energy services consumed 17 EJ
in 1985, or about 29% of total secondary
energy (36% of equivalent primary energy).
For the OECD as a whole, the picture is
quite similar, with residential and commercial
energy use amounting to about 30% of the
total secondary energy. Figure 5-4 shows the
distribution of energy use within the U.S.
residential/commercial sector. The largest
component (more than one-third) of
residential/commercial energy use is for space
heating; combined with air conditioning and
ventilation, the overall use of energy for space
conditioning accounts for more than half
(54%) of all residential and commercial
energy use. Lighting accounts for another
15%, hot water heating, 11%, refrigeration,
7%, and the remaining energy (13%) is
divided among all other appliances and
equipment used in residences and commercial
establishments (U.S. DOE, 1987b).
Global energy use in the residential and
commercial sectors is expected to grow
significantly in the future. In addition, a shift
toward electricity for a higher percentage of
energy use in these sectors is likely, resulting
in increases in end-use efficiency, but implying
that primary energy required (accounting for
losses in electricity generation) will grow
more rapidly.
It is expected that residential and
commercial energy use will grow most rapidly
in developing countries as economic growth
rapidly translates into increasing demands for
energy-related amenities in homes and
commercial buildings. In the USSR and
Eastern Europe large increases are expected
for similar reasons.
Due to major technical improvements
demonstrated in recent years, future
residential and commercial buildings could
require substantially less energy for heating
and cooling. Because the stock of buildings
turns over so slowly, it is also important to
focus on retrofitting, which could reduce air
conditioning and heating needs in existing
buildings. Dramatic improvements in
efficiency are also possible in lighting,
particularly in commercial buildings, where
lighting may account for a large share of the
electrical energy used. Improvements in
lighting efficiency also frequently have the
added benefit of reducing the amount of
waste heat produced by the lighting system
and thus reducing the air conditioning
requirements as well.
Options for reducing energy use in the
residential and commercial sectors are fairly
well characterized, at least in the OECD. As
discussed below, potentials are very great, but
due to the long turnover tune of building
stock, improvements may have to be phased
in over a long time period. In addition,
alternative fuels may be introduced,
particularly in developing countries, which
would further reduce the greenhouse impact
of energy use.
With aggressive programs to improve
the energy efficiency of buildings, it appears
technically feasible to reduce projected U.S.
energy use in the residential/commercial
sector at least 50% by the year 2010. The
technical potential in the OECD as a whole
is probably close to that of the U.S.
Although more detailed analysis is required,
preliminary indications are that the technical
potential to reduce projected residential and
commercial energy in the much more rapidly
V-33
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Policy Options for Stabilizing Global Climate
FIGURE 5-4
U.S. RESIDENTIAL/COMMERCIAL ENERGY USE
(Exajoulea)
Spac* Heating
10EJ
Refrigeration
2.1EJ
Hot Water Heating
3.2 EJ
Air Conditioning
•nd Ventilation
6.3 EJ
Source: U.I. DOE, ig*7e.
V-34
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Chapter V: Technical Options
growing developing countries and in the
USSR and Eastern Europe is even greater
than that estimated for industrialized
countries.
It appears technically feasible with
today's technology to reduce space
conditioning energy requirements in new
homes by 50% relative to the current average
for new homes. Retrofits of existing homes
could reduce space conditioning energy use by
an average of 25% with the "house-doctor"
approach. It may be technically feasible to
reduce energy use in existing commercial
buildings by at least 50%, and new
commercial buildings could easily be 75%
more efficient than the average U.S.
commercial building. In 1985 the U.S.
consumed about 15.3 EJ of energy (primary
energy equivalent) for residential and
commercial space conditioning (U.S. DOE,
1987a). Retrofits to existing stock could save
at least 4 EJ.
Current estimates indicate that
residential and commercial energy use in the
U.S. and in the OECD as a whole may
remain roughly constant through 2025 under
"business as usual" assumptions. With rapid
widespread penetration of the most efficient
new buildings, instead of gradual
improvement, the growth in energy
consumption from new buildings could be
greatly reduced.
Based on potential energy savings of
more than 60% for almost all types of
appliances, a 50% overall reduction in
appliance energy use by the year 2010 is
technically feasible. To achieve this
reduction would require aggressive policy
actions that would (1) ensure that all
appliances produced in the next decade be as
energy efficient as the best current technology
can produce and (2) encourage rapid turnover
of existing appliances. Current energy use
from such appliances is in the range of 7.4-8.4
EJ (expressed as primary energy equivalent).
Near-term technical options in the
residential/commercial sector for industrialized
countries, developing countries, and the
USSR and Eastern Europe are discussed
below.
Near-Term Technical Options: Industrialized
Countries
Improve Space Conditioning
Improved efficiency in space
conditioning (heating and cooling) can be
obtained in several ways. First, the design of
new buildings can be altered to improve their
insulating qualities, thus reducing losses in
heating or cooling. Second, improved
technologies can be applied to make existing
buildings more weathertight, requiring less
energy for heating and cooling. Finally,
advanced technologies for heating and cooling
equipment can be dramatically more efficient
than devices currently in wide use. A number
of very thorough and high-quality reviews of
the potential for energy efficiency
improvements in buildings have been
produced in recent years (see, for example,
Hirst et al., 1986; Schipper et al., 1985). The
discussion below draws on the extensive
published literature to illustrate the technical
potential for improvement.
New Residences. The potential for
improving energy efficiency in new homes is
very significant. Simply by modifying the
building shell to improve its insulating
capabilities, space heating energy
requirements can be reduced dramatically.
Current new homes in the U.S. require, on
average, almost 40% less energy to achieve
the same level of heating as the average
existing house in the U.S. (See Box 5-3, which
illustrates the range of energy requirements
for space heating on a per unit of floor space
basis.) What is even more interesting is that
the most efficient new houses are 50% more
efficient than the average new home.
(However, relatively few of these very energy-
efficient homes are currently being built.)
Very advanced prototypes and design
calculations indicate that it is technically
possible to build homes whose heating energy
requirements would range from 15 to 20
kilojoules per square meter per degree day
(kJ/m2/DD), or 10-12% of the average
requirements for today's homes.2
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Policy Options for Stabilizing Global Climate
BOX 5-3. Improving Energy Efficiency in Single-Family Homes
Space Heat Requirements in Single-Family Dwellings
(kJ/m2/DD)
United States
Average, housing stock 160
New (1980) construction in U.S. 100
Mean measured value for 97 houses in Minnesota's
Energy Efficient Housing Demonstration Program 51
Mean measured value for 9 houses built in Eugene, Oregon 48
Calculated value for a Northern Energy Home, New York area 15
Sweden
Average, housing stock 135
Homes built to conform to the 1975 Swedish Building Code 65
Mean measured value for 39 houses built in Skane, Sweden 36
House of Mats Wolgast, in Sweden 18
Calculated value for alternative versions of the prefabricated
house sold by Faluhus
Version #1 83
Version #2 17
Source: Goldemberg, 1988.
The striking energy savings (compared with the average home), up to 90%, that is
possible with new "low-energy" homes, as illustrated by the figures above, are achieved
through the use of state-of-the-art construction and design techniques and technologies;
a few of the areas where significant changes have occurred include the following:
• Building Envelope - Larger wall and ceiling cavities, allowing for significantly
more insulation, have been obtained with new construction materials and
designs, such as "I-beam" framing members, raising R-values to as high as R-
38 in some low-energy homes. Polyethylene vapor/air barriers in external
walls reduce infiltration of outside air, one of the major sources of heat loss
in most homes. Windows are being triple and even quadruple glazed, and,
in some cases, incorporate low-emissivity films and inert gases, such as
argon, between the panes to improve their insulating quality.
V-36
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Chapter V: Technical Options
BOX 5-3. Improving Energy Efficiency in Single-Family Homes
(continued)
• Mechanical -- These include heating, cooling, and ventilating systems. In
addition to high-efficiency furnaces, heat pumps, and air conditioners, many
low-energy homes incorporate air-to-air heat exchangers. These are needed
to bring fresh air into the house, since natural infiltration is significantly
reduced, but they improve energy efficiency by extracting approximately half
the heat from the exhaust air and transferring it to incoming air. The
newest development in mechanical ventilation is the heat-pump exhaust
system, which uses warm exhaust air to provide water heating.
• Active/Passive Solar Design, Thermal Storage - Many different designs have
been developed to make better use of solar gain to provide heat. These
include use of south-facing windows, greenhouses, atriums, etc., and are
often combined with thermal storage systems that store heat collected during
peak daylight hours for redistribution when it is needed at other times.
Storage systems can also work in the reverse way, collecting cool air during
the night and circulating it during warmer hours.
In addition to the potential for
improving the thermal properties of building
shells, equally important advances have been
made in developing high-efficiency equipment
for both space heating and cooling. Already
being marketed in the U.S. and in Europe are
high-efficiency gas and oil furnaces that are
about 95% efficient, compared with the
average of 75% for new furnaces in the U.S.
(Geller, 1988).
Substantial energy savings are possible
in electrically heated (and cooled) homes with
recently designed efficient heat pumps. The
most efficient pumps on today's market are
about one-third more efficient than average.
Advanced ground-coupled heat pumps have
recently been commercialized and will provide
even more efficient options over the next
decade. These commercial systems have been
shown to achieve a "seasonal performance
factor" (SPF) of 2.5-3.0, which compares with
an SPF of 1.5-1.9 for electric air-source heat
pumps (Strnisa, 1988). In addition, gas heat
pumps are currently being demonstrated and
may be commercial soon. These systems may
be even more efficient than advanced electric
heat pumps.
With super-insulated shells it may not
be necessary to install a central heating
system at all. Some of the advanced designs
require so little heat input that small electric
resistance heaters may be cost-effective in
moderate climate areas. The greatly-reduced
capital cost for this option may offset the
increased cost for the superinsulating features.
In very cold regions, the added cost of very
efficient gas or oil furnaces would be justified.
In regions where cooling is also required, the
advanced heat pumps would probably be the
most economic choice.
If all options were used in combination,
it appears technically quite feasible for
advanced building shells and efficient
heating and cooling equipment to reduce
space conditioning energy requirements in
new homes to less than 10% of current
average use.
Existing Residences. It is expected that
the net growth in housing stock will be slow
in the future in industrialized countries
because of the extensive existing stock and
low population growth. In addition, existing
housing stocks have very long lifetimes.
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Policy Options for Stabilizing Global Climate
Therefore, existing stocks will dominate the
residential sector for many decades. Thus, it
is extremely important to focus on
opportunities for reducing energy
requirements in existing buildings. Many of
the advances that have made possible the
enormous potential energy savings for new
homes are to some extent applicable to
existing homes.
In general, retrofit improvements are
somewhat less effective and more costly than
those incorporated in the initial design of a
new home. Nonetheless, cost-effective
technical options exist for substantially
reducing energy requirements of existing
homes. Storm windows, added insulation,
clock thermostats, and retrofit of heating
systems have been considered conventional
conservation measures for several years. In
addition, improved maintenance of equipment
and building shells and more attention to
operation of equipment (i.e., automatic
setback thermostats, automatic light switching)
could reduce energy consumption in existing
buildings at relatively low cost. Programs to
encourage consumers to implement these
conservation options have been carried out in
a number of areas and have shown
considerable success. One study of 40,000
retrofits monitored by U.S. utility companies
in the early 1980s showed that energy
consumption fell by 25% on average, and
homeowners received a 23% return on their
investments (Goldman, 1984).
Despite the favorable economics of
some retrofit conservation measures, only a
small portion of the potential energy savings
from conservation retrofits has been realized
to date. This is especially true in rental
housing where the landlords do not perceive
a financial interest in investing in retrofits.
Also, low-income families, even if they own
their homes, often lack the information or
upfront capital to carry out cost-effective
conservation measures. If conventional
retrofit programs could be extended to larger
percentages of existing housing stock, energy
savings could be substantial.
Beyond conventional conservation
programs, there are now more sophisticated
options for improving the retrofit savings.
Detailed measurements since the late 1970s
have shown that existing homes have obscure
defects in their thermal envelopes, leading to
very large heat losses. Conventional walk-
through energy audits are unlikely to identify
these defects, nor would subsequent
conservation retrofits correct them. New
instrumented analysis procedures developed
over the last few years can locate these
defects quickly, but these instrumented audits
are expensive compared with the standard
energy audits now provided by many utilities.
On the other hand, many of the
"hidden" defects, once detected, can be easily
corrected at small cost. This has led to the
development of the "house-doctor" concept as
an alternative to traditional audits. For this
type of audit a team of technicians conducts
an instrumented audit and repairs many of
the defects on the spot. One test of this
concept showed average immediate energy
savings of 19% from one-day "house-doctor"
visits. Subsequent conservation retrofitting
done at the recommendation of the house
doctors increased the average energy
reduction to 30%. The average cost of all
retrofit measures was $1300 and the average
real internal rate of return in fuel savings was
20% (See Goldemberg et al., 1988).
Another approach to improving
residential and commercial energy efficiency
has been proposed recently by researchers at
Lawrence Berkeley Laboratory. Their
approach is a reworking of the age-old
concept of using shade trees to assist in
cooling residential buildings. In their analysis
the authors point out that in addition to the
direct benefit in terms of reducing air
conditioning loads at each house, the indirect
effect of planting trees throughout an urban
or suburban area, as well as other measures
to increase the reflectivity of surfaces, can
reduce the "heat island" effect, lowering
ambient temperatures and further reducing air
conditioning loads. In addition, of course, the
trees directly remove CO2 from the
atmosphere, although the CO2 reductions due
to reduced cooling loads from well-placed
trees are probably much greater than the
CO2 absorption by the trees (see Rosenfeld,
1988; Akbari et al., 1988). The city of Los
Angeles has announced their intent to start
such a program (Washington Post, 1989).
V-38
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Chapter V: Technical Options
The advanced furnaces and heat pumps
available for new homes could also provide
significant benefits in the retrofit market.
Economics of efficient equipment are
generally more favorable as retrofits. Even
after a retrofit shell improvement program,
including the house-doctor approach, energy
use in existing homes will remain well above
the best levels achievable for new super-
insulated homes. Thus, the added expense of
advanced heating and cooling equipment will
be paid back much faster in energy savings.
In one example, existing homes that
had already been visited by house doctors and
had received associated shell improvements
were evaluated for improved furnaces. Shell
improvements were shown to have reduced
gas use for space heating to about 70% of the
previous requirement. Researchers estimated
that retrofit of advanced condensing gas
furnaces would further reduce space heating
energy use to 44% of the original
requirement. The estimated incremental
investment (to replace a worn-out furnace
with the 95% advanced furnace rather than a
conventional 69% model) was estimated to
average $1000 and result in fuel savings that
correspond to a real rate of return of 15%
(Goldemberg et al., 1988).
Commercial Buildings. Like residences,
commercial and institutional buildings
currently use significant amounts of energy,
particularly for space conditioning and
lighting. Opportunities for efficiency
improvements also appear significant
Commercial buildings in the U.S. use about
3.6 EJ of fossil fuels annually (mostly gas in
the U.S. - other OECD countries continue to
heat a significant percentage of buildings
with oil) and about 2.6 EJ of electricity
(equivalent to about 8 EJ of primary energy)
(Rosenfeld and Hafemeister, 1985).
Some progress is already being made in
improving energy efficiency in commercial
buildings. While surveyed commercial space
in the U.S. increased by almost 10% between
1979 and 1983, total energy consumption
actually declined by about 4%. Electricity
consumption, however, increased in absolute
terms as well as in share of total commercial
energy use. Thus, the primary energy
equivalent of commercial end-use energy
consumption has increased (U.S. DOE,
1987a).
While progress has been made, it is
evident that commercial energy use in the
U.S. could still be reduced significantly with
cost-effective efficiency measures. Estimated
commercial energy use in the U.S. was about
3.0 gigajoules (GJ)3 per square meter per
year in 1980 (expressed as equivalent primary
energy production). This figure is down from
5.7 GJ in 1973, but could still be greatly
improved (Flavin and Durning, 1988). One
recent analysis estimated that energy use in
new commercial buildings could be reduced by
more than 50% below the current averages
(Rosenfeld and Hafemeister, 1985).
As in the residential sector, traditional
building shell conservation measures, such as
added insulation and window glazing,
reductions in infiltration rates of outside air,
passive solar energy concepts, and heat
exchange between exhaust and incoming
ventilation air are effective although less
important. The traditional approach of tree
shading combined with reflective surfaces to
achieve direct cooling can, as discussed above,
also be applied to commercial buildings.
In addition, some more sophisticated
techniques are cost effective for larger
commercial buildings. New commercial
buildings are being designed with "smart"
energy management systems. These
computerized systems monitor outdoor and
indoor temperatures, levels of sunlight and
location of people in the building. The
system can then allocate heating, cooling and
ventilation efficiently (Brody, 1987).
Another advanced technique being
applied for commercial energy efficiency is
thermal storage. In this case, some storage
medium, such as a body of water, is used to
store heat or cooling when it is readily-
available and then the warm or cool air is
released later when it is needed. This
concept has been used in new commercial
buildings in Sweden, storing heat energy from
people and equipment, and in Nevada to chill
water with cool night air and use the chilled
water to offset the need for air conditioning
during the day (Rosenfeld and Hafemeister,
1985).
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Policy Options for Stabilizing Global Climate
Window technology is also improving
rapidly. A special "heat mirror" film, which
doubles the insulation value of windows, is
now commercially available. The film is
designed to let light in without allowing heat
to escape. Another available technology is to
create a vacuum in the space between two
panes, creating a thermos effect. These and
other advanced technologies may allow
commercially-available windows in the 1990s
to have the same insulating value as ordinary
walls (Brody, 1987; Selkowitz, 1985).
As was the case with residences, many
of the advances in energy efficiency for new
commercial buildings are transferable to
retrofit applications to a lesser degree. A
study conducted some years ago attempted to
estimate the potential energy savings available
from retrofits of existing commercial
buildings. The conclusion drawn from a
survey of several experienced engineers and
architects was that a target of a 50%
reduction in energy use in U.S. commercial
buildings by the year 2000 was reasonable
(SERI, 1981).
More recently, Amory Lovins and
others at the Rocky Mountain Institute
conducted a detailed analysis of the retrofit
potential of commercial buildings in the
Austin, Texas, area. This study identified
potential savings in electrical energy that
totaled 73% of the buildings' current
electrical energy use (for lighting and other
equipment as well as space conditioning).
The cost of these measures was estimated to
be lower than the operating costs of existing
powerplants (Rocky Mountain Institute,
1986). There is some question as to what
proportion of these calculated savings could
be achieved in practice.
District Heating and Cooling/
Cogeneration. Use of district heating and
cooling (DHC) can be an extremely efficient
approach to space conditioning, particularly in
dense urban areas and when the heat source
is also a cogenerator of electricity.
Technologies for cogeneration -- simultaneous
production of electricity and heat or steam for
other useful purposes - are described in
PART TWO. Cogeneration with DHC could
serve a very large potential market for these
efficient technologies, with the possibility of
offsetting significant amounts of oil and
natural gas that would otherwise be used in
dispersed space heating applications. In
addition, heat from a central cogenerator can
be used to generate air conditioning in high
efficiency, heat-activated chillers that do not
use chlorofluorocarbon (CFC) refrigerants,
possibly offsetting significant amounts of
electricity use and contributing to needed
reductions in CFC production. This approach
is already widely used in the Soviet Union
and in many European countries and may be
expanded in the future. In Denmark, for
example, 46% of current space heating
requirements are met with district heat -
27% based on cogeneration and the other
19%, single district heating. A recent
projection estimates that by 2000 district
heating based on cogeneration will satisfy
almost 37% of total space heating
requirements (Mortensen, 1989). The
efficiency improvements in this type of system
are substantial and contribute to reduced CO2
emissions even if fossil fuels are used, as is
normally the case. The International Energy
Agency (IEA) is coordinating a significant
amount of research by member countries to
develop more cost-effective technologies for
DHC. A recent report documents 47
advanced technologies that can improve
efficiency or lower costs (IEA, 1989).
Interest in DHC has grown in the U.S.
as well in recent years. In New York, for
example, three demonstration systems are
currently in operation in Buffalo, Rochester,
and Jamestown. Studies are underway to
design systems in five other communities
(Strnisa, 1988). At a recent conference on
DHC technology, one participant estimated
that widespread application of
cogeneration/DHC systems could reduce U.S.
carbon dioxide emissions by 10-15%. This
would also be expected to produce significant
local and regional economic benefits -
reducing and stabilizing energy costs to local
government and business communities,
creating jobs for skilled and unskilled
workers, and retaining a greater proportion of
total energy expenditures in local areas
(Clarke, 1989).
Indoor Air Quality. One of the
concerns about increasing the energy
efficiency of buildings is the increase in
V-40
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Chapter V: Technical Options
indoor air pollution that can result, primarily
from efforts to reduce air infiltration. Most
homes in the U.S. have air exchange rates, on
average, of more than one change per hour,
meaning all the air in the house is replaced
by outside air once each hour. As new homes
are constructed more tightly and some older
homes are retrofitted with vapor barriers and
better seals around doors and windows, the
air exchange rate drops. Without additional
ventilation measures, concentrations of several
harmful pollutants, including radon gas,
formaldehyde, combustion products from
tobacco smoke and wood stoves, and asbestos
particles, can reach harmful levels.
Control strategies for these forms of
indoor air pollution include air cleaning, local
ventilation, mechanical ventilation with heat
recovery, and exhaust ventilation with heat
pump heat recovery. Heat recovery or air-to-
air exchange systems have become more
popular as homes have become better
insulated and more tightly sealed. These can
ensure the generally-accepted minimum
standard of about 0.5 air changes per hour,
while reducing heat loss by using the heated
exhaust air to warm the incoming fresh air.
Unfortunately, the costs of these systems are
high and studies in Canada suggest that their
efficiencies may be lower than manufacturers
have claimed (Hirst et al., 1986). This may
be due in part to improper maintenance by
homeowners. Heat recovery systems, which
usually draw air continuously and can have
problems with condensation forming in the
heat exchanger, require more routine
maintenance than the average homeowner is
accustomed to devoting to a major appliance.
The use of exhaust ventilation systems
connected to an air or water heat pump is a
new technological approach that may hold
some promise for improving cost-effectiveness
and improving some of the maintenance
issues. These systems are being developed
primarily in Sweden. It appears that
currently-available commercial technology can
be applied to maintain indoor air quality
standards while significantly reducing energy
requirements. Current technology develop-
ment efforts directed at reducing costs and
maintenance requirements should be a high
priority research area.
Use Energy-Efficient Lighting
Lighting consumes about 20% of U.S.
electricity, most of it in residential and
commercial buildings. This end use offers
some of the most cost-effective opportunities
for saving energy. One study has estimated
that 40 large U.S. powerplants could be
replaced by simply implementing currently-
available, cost-effective lighting efficiency
improvements (Rosenfeld and Hafemeister,
1985). Cutting electricity use for lighting in
industrialized countries by three quarters has
been proposed as a reasonable goal (Flavin
and Durning, 1988). Box 5-4 describes several
key advanced lighting technologies.
A number of currently commercial
measures, implemented in combination, can
achieve dramatic energy reductions ~ over
75% in commercial/institutional settings.
These measures include improved controls,
reflectors, spacing of lighting, and more
efficient bulbs and ballasts. The University of
Rhode Island reported reductions of 78% in
lighting energy after implementing such a
program. The cost of saved energy was
calculated to be less than 1 cent per kilowatt-
hour (kwh) (New England Energy Policy
Council, 1987). An added benefit of lighting
improvements in warm climates is that more
efficient lighting reduces waste heat and,
therefore, air conditioning loads. The
California Energy Commission has estimated
that in Fresno, every 100-watt savings in
lighting reduces air conditioning energy
requirements by 38 watts (Rocky Mountain
Institute, 1986).
Use Energy-Efficient Appliances
After space conditioning and lighting,
remaining energy uses in residential and
commercial buildings are largely associated
with large appliances. Opportunities for
significant energy efficiency improvements in
this category have been well documented.
Table 5-4 illustrates some of these
opportunities. U.S.-made refrigerators, for
example, currently average 1450 kwh per year.
The best currently commercial model in the
U.S. uses about half that much energy. A
recent study calculated that efficient new
V-41
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Policy Options for Stabilizing Global Climate
BOX 5-4. Increasing Lighting Efficiency
Research and development into energy efficient lighting and design features has produced
a constant stream of new products and advances. Below are brief descriptions of several
of the areas where major advances have taken place.
• Compact Fluorescent Lamps: Compact fluorescent lamps are designed to be
screwed into a standard light socket and thus have begun to compete directly
with incandescent bulbs. Because they are 60-70% more energy-efficient
than incandescent (Hirst et al., 1986) and are beginning to gain wider
acceptance, they represent potentially significant energy savings. If compact
fluorescent replaced all incandescent lighting, it has been calculated that this
could displace 7.5% of total electrical consumption in the U.S. (Lovins and
Sardinsky, 1988).
• High Intensity Discharge (HID) Lamps: These are designed primarily for
warehouses, factories, street lighting, etc. Three types of HID lamps are
currently in use: high-pressure sodium, low-pressure sodium, and metal
halide. High- pressure sodium and metal halide give approximately 45-60%
savings over mercury vapor or fluorescent lighting. Low-pressure sodium is
somewhat more efficient, but its intense yellow light can be undesirable for
many applications (Hirst et al., 1986).
• Electronic Ballasts: In conventional fluorescent lights the voltage required
for operation is provided by an electromechanical ballast which itself
consumes a portion of the energy used. New electronic ballasts reduce this
additional power consumption by 20-35% (Hirst et at, 1986) and, became
of their smaller size, are a key factor in the emergence of compact
fluorescent lamps.
• Daylighting: Daylighting is a design approach that enhances the use of
natural light either from windows, sidelighting, clerestories, monitors and
skylights, or from the use of light pipes or optical fibers to transmit light to
the location needed. The use of light colored paints and light shelves helps
to distribute the light into the building interior.
• Additional Advances: Several other advances in lighting technology and
design deserve mention. One advance is specular ("mirrorHke11) reflectors
that increase total reflectivity, direct the light in a more optically favorabk
direction, and maintain their high reflectivity significantly longer. Lighting
controls, which include time clocks, scheduling controls, personnel or
occupancy sensors, and daylighting sensors, reduce power consumption by
turning off lights when they are not needed. Task lighting improves
efficiency by directing light onto the specific task area where it is needed
most, rather than lighting entire areas.
V-42
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Chapter V: Technical Options
TABLE 5-4
Summary of Energy Consumption and Conservation Potential
with Major Residential Equipment
(kwh/yr or therms/yr)
Product
Refrigerator
Freezer
Central AC
Room AC
Elec. water heating
Elec. range
Elec. clothes dryer
Gas space heating
Gas water heating
Gas range
1986
Stock
UEC3
1450
1050
3500
900
4000
800
1000
730
270
70
1986
New
UECb
1100
750
2900
750
3500
750
900
620
250
50
1986
Best
UEC0
750
430
1800
500
1600
700
800
500
200
40
Advanced
technology
for 1990s3
300-500
200-300
1200-1500
300-400
1000-1500
400-500
250-500
300-500
100-150
25-30
a Unit energy consumption per typical installation in the 1986 housing stock.
b Unit energy consumption for the typical model produced in 1986.
c Unit energy consumption for the best model mass-produced in 1986.
d Unit energy consumption possible in new models by the mid-1990s if further cost-effective
advances in energy efficiency are made.
Source: Geller, 1988.
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Policy Options for Stabilizing Global Climate
refrigerator freezers that would use about 200
kwh per year, or less than 15% of the current
average use, could be cost-effectively produced
(Goldstein and Miller, 1986). Water heaters
also account for a large percentage of
appliance energy use. The potential for
energy savings is significant through the use
of the most efficient technologies and also by
switching from electricity to gas. Other
energy-intensive appliances also provide
opportunities for energy savings. As shown in
Table 5-4, the potential exists for advanced
technologies that could be produced in the
1990s that are at least 50% more energy
efficient than the 1986 average for all major
energy-using residential appliances (Geller,
1988). As discussed in Chapter VII, recently
enacted national appliance energy efficiency
standards are expected to produce substantial
improvements in the United States.
Near-Term Technical Options: Developing
Countries
In developing countries markedly
different strategies may be necessary to
address residential and commercial energy
services. In many developing countries there
are distinct modern and traditional sectors.
In the modern sector, energy-use patterns are
very similar to those in industrial economies
(adjusted for climate differences).
Commercially-marketed fossil fuels and
electricity provide the energy input for a
similar mix of energy services: space
conditioning, water heating, lighting, and
appliances for cooking, refrigeration,
entertainment, etc. This modern sector,
however, is often smaller than the traditional
sector, which exhibits completely different
energy-use patterns.
The energy sources in the traditional
sector are largely "noncommercial" biomass,
used primarily for cooking and, in some
colder or high-altitude regions of developing
countries, for space heating. Also, fossil fuels
(e.g., kerosene) are frequently used for
lighting. (In China and the coal districts of
India, unlike most other developing countries,
coal is also used for residential cooking and
space heating in the traditional sector.) The
task of development projects in these poorer
sectors is to vastly increase the level of energy
services available for residential and
commercial applications. Altruism and
development objectives aside, this approach
can contribute significantly to solving
the climate warming problem because many
developing countries have used fuelwood to
such an extent that they have become net
consumers of forests, and global deforestation
is one of the significant causes of increasing
greenhouse gas concentrations. The
important issue from a climate perspective is
to increase energy services without increasing
greenhouse gas emissions.
As the developing countries continue to
increase their per capita energy use, the
implications in terms of energy use and
greenhouse gas emissions are enormous. It is
technically possible, however, for developing
countries to substantially increase per capita
energy services without substantially increasing
fossil-fuel use. Emissions-reducing strategies
similar to those proposed for industrialized
countries can be promoted in the modern
sectors of the developing countries. However,
strategies suitable for the traditional, poorer
sectors must be integrated into ongoing
economic development programs if they are
to be accepted by the local population.
Technical options for reducing greenhouse gas
emissions must not only be efficient, but also
be designed to increase energy services to
these poorer sectors.
More Efficient Use of Fuelwood
The primary use of biomass energy in
developing countries is in residential cooking,
traditionally done in inefficient and smoky
conditions. The inefficiency of combustion
can exacerbate deforestation and lead to
increased time and effort devoted to gathering
fuelwood (and fodder), and the smoky
combustion results in exposures to significant
emissions of health-damaging air pollutants.
Recognition of these problems has
focused a great deal of attention on
improving the cookstove as a low-cost
solution. Existing cookstoves have efficiencies
only on the order of 10%. Relatively simple
improvements in stove design can in theory
reduce wood requirements by 35-70%
(Goldemberg et al., 1987). However, getting
people in developing countries to accept and
use better-designed stoves has proved difficult
V-44
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Chapter V: Technical Options
for a number of reasons (Miller et al., 1986).
In spite of spirited efforts by a number of
dedicated groups, generous grants by
international aid agencies, and substantial
expenditures by many governments, it has
proved surprisingly difficult to coax people
away from traditional cooking stoves and
practices. Traditional stoves come in a
bewildering variety of designs and materials
and have evolved to suit local fuels and diets.
They perform a multitude of functions that
were not considered by designers and
promoters of early "improved" stoves. Failure
of the newer designs to incorporate features
that could perform some of these functions
often hampered their acceptance. Current
improved designs represent a third generation
in this technology development process
(Smith, 1989).
West Africa, Kenya and Karnataka,
India, and a few others, are successfully
promoting improved-design stoves (Baldwin et
al., 1985; Reid et al., 1988). Successful
designs are based on sound principles of heat
transfer (Baldwin, 1987), are targeted to a
particular region (generally where cooking
fuel is traded), require no substantial
behavioral modification from users, and are
provided with follow-up support.
Predicted fuel savings with improved
stoves, which are based on laboratory water-
boiling efficiency tests, have invariably proved
to be overestimates under field conditions. If
fuel savings observed in the laboratory were
directly transferable to the field, an improved
stove with 40% efficiency would result in a
75% fuel saving when it replaced a traditional
stove with 10% efficiency. Yet only a few
programs have reported fuel savings (at best
on the order of 20%), though greater savings
could be possible as programs improve with
experience (Ahuja, 1990).
Despite the limited efficiency
improvement with new fuelwood applications,
the payback period is on the order of a few
months and therefore economically attractive
(Manibog, 1984). As Williams (1985) points
out, the adoption of improved stoves is a far
more cost-effective method of dealing with
the fuelwood crisis than any "supply-oriented"
solution to the problem that emphasizes
growing trees for fuel.
Widespread introduction of the current
designs of improved stoves, while reducing
total emissions of oxides of carbon per
cooking task, will change the ratio of CO2 to
CO emitted. This ratio on a mass basis for
traditional stoves is close to 10:1, whereas for
more efficient stoves it could be reduced to
5:1, reflecting the more complete combustion
in traditional stoves (Joshi et al., 1989).
Although CO is not a radiatively interactive
gas, it does interact with hydroxyl ions; as a
result, its presence increases the concentration
of methane and ozone in the troposphere (see
CHAPTER II).
Use Alternative Fuels
In the traditional sectors of many
developing countries, substitution of fossil-
based end-use technology for traditional
biomass use may be desirable as part of a
larger strategy even though it may directly
increase greenhouse gas emissions to a small
degree. Gaseous fuels (natural gas, LPG,
etc.) are very attractive relative to fuelwood
for several reasons, including their vastly
superior convenience and controllability. In
addition, a well-designed gas-fueled stove can
be five to eight times more efficient than
traditional firewood stoves (Goldemberg et
al., 1988). Thus, the shift to gaseous cooking
fuel can decrease the demand for fuelwood,
which may slow the rate of deforestation in
some areas, or free up vast amounts of
fuelwood for use as a feedstock for advanced
biomass energy systems, or both. In a few
developing countries, such as China, coal is
used for cooking and space heating; the
advantages discussed above for gaseous fuels
also apply as a replacement for coal (with
associated reductions in greenhouse gas
emissions).
In the traditional sectors of many
developing countries, lighting frequently is
achieved with very inefficient combustion
technologies. In India, for example, it is
estimated that 80% of the rural households
illuminate with kerosene lamps. The
efficiency of illumination of these lamps is
very low. Providing the same level of
illumination with incandescent electric bulbs
would be 200 times more efficient at the end
use (Goldemberg et al., 1988). (In fact, the
availability of electricity will actually allow a
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Policy Options for Stabilizing Global Climate
much greater level of illumination in
homes). Thus, even if the electricity
production is only 30% efficient, and is coal-
fired (worst-case assumptions), the equivalent
electric lighting would still produce less net
CO2. If the most efficient current compact
fluorescent lighting were used, the benefit
would be even greater. Of course, the major
constraint to substituting electricity for fossil
fuels is the limited availability of electricity in
developing countries. Small-scale local
generation based on renewable technologies
could make major contributions in this
situation. These and other options for
increasing electricity in developing countries
are discussed in PART TWO.
Retrofit Existing Buildings
For those residential and commercial
segments of developing countries that have
similar characteristics to industrialized
countries, many of the same retrofit efficiency
measures are appropriate. In fact, it is likely
that many retrofit measures would be more
effective in developing countries. As pointed
out in a recent U.S. AID study (I988b), while
"industrialized countries have made major
strides in using electricity more efficiently
over the last decade, few achievements have
been made in developing countries in using
electricity more efficiently. The opportunities
for improvements are tremendous, and the
cost is only a fraction of the generation
expansion option." In addition, air
conditioning requirements are generally
heavier in tropical developing countries.
Thus, improvements in building shells and air
conditioning equipment could be very
effective in reducing electricity use. Similarly,
the air conditioning benefit of improved
lighting (due to less waste heat) would also
be greater in developing countries.
A recent study of Pakistan identified
cost-effective efficiency improvements that
could reduce electricity use in the commercial
sector by over 30%. Based on commercially
available improvements in lighting, air
conditioning and fans, and thermal insulation,
the study projected national savings of 1800
megawatts (MW) of generating capacity and
18,200 gigawatt-hours (GWh) of electricity
generation (U.S. AID, 1988b). An analysis in
Brazil indicated the potential to reduce
electricity use for lighting by 60% in many
commercial buildings (Geller, 1984).
Build New Energy-Efficient Homes and
Commercial Buildings
Rapid expansion of the residential and
commercial building stock is expected to
occur in conjunction with economic
development in the developing countries over
the coming decades. Use of the efficiency
options discussed for industrialized countries,
adapted to local conditions and objectives,
could minimize the increases in energy use
associated with this growth. Obviously, since
the rate of construction of new building space
(and distribution of appliances, etc.) will be
much higher in developing countries, the
importance and potential impact of efficiency
measures will be proportionately greater as
well.
Several recent studies have identified
significant potential for reductions in energy
use in new commercial buildings in
developing countries (see, e.g., Turiel et al.,
1984; Deringer et al., 1987). In Singapore,
careful use of daylighting alone has the
potential to reduce energy use by roughly
20% relative to the current building stock
(Turiel et al., 1984). Other important
improvements include efficient lighting
systems, external shading, and size and
placement of windows.
Near-Term Technical Options: USSR and
Eastern Europe
Energy use in buildings in the Soviet
Union is dominated by space heating: 25%
of the population lives in a climate that
requires the use of heating between 210 and
over 300 days per year. An additional 40%
live in a climate characterized by a 180- to
280-day heating season (Tarnizhevsky, 1987).
Since the early 1970s, the Soviets have made
dramatic progress in improving energy
efficiency in specific applications, "in large
energy uses easily identified and controlled by
the planning apparatus" (Hewitt, 1984). The
dominant approach advocated by Soviet
researchers for space conditioning is
consistent with this experience. Centralized,
or "district" heating systems, have been the
preferred approach to space heating for some
V-46
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Chapter V: Technical Options
time. By 1980, about 70% of residential and
commercial heat demand in cities and towns
was provided by central systems. Sources of
heat for these systems are primarily
cogeneration from both fossil-fueled and
nuclear powerplants and some waste heat
recovery from large industrial process heat
uses (e.g., ferrous metal, chemicals, and
petrochemicals) (Vavarsky et al., 1987). Most
of the residences in the USSR are multi-
family rather than single-family structures
which should, in principle, require less space
heat because of the lower surface-to-volume
ratio. Living space per capita is also much
lower than in OECD countries. A recent
estimate for the USSR is about 15 square
meters per capita as compared to roughly 50
square meters per capita in the U.S.
(Schipper and Cooper, 1989).
Despite the predominance of district
heating and multi-family structures, the energy
intensity of space heating in the USSR
appears high relative to OECD countries.
Schipper and Cooper (1989) have estimated
that space heating in the USSR requires
about 230 kJ/m2/DD, which is about 50%
higher than the U.S. average and about
double the value for Sweden. There is
obviously room for considerable efficiency
improvement in space heating. This may be
very important if heating space per capita
increases with incomes in the future. A
Soviet research institute has projected that
energy use in industrial and commercial
buildings may rise by over 40% between 1985
and 2000 (Bashmakov, 1989).
There is already considerable interest in
improving efficiencies in buildings in the
USSR. Plans for improving energy efficiency
include: 1) further replacement of local heat
sources with district heat from cogeneration;
2) weatherization of buildings; and 3)
reductions in heat losses in distribution
networks (Tarnizhevsky, 1987). As many
western visitors to the Soviet Union have
noted, a common method for regulating
temperature in over-heated buildings is simply
to open windows. Improvements in
temperature control systems could save
considerable space heating energy.
Electricity consumption in buildings is
also growing in the Soviet Union, principally
for lighting and household appliances
(including some electric ranges). The most
significant sources of growth from 1975-1985
were attributed to increasing proliferation of
household applications associated with
improving living standards. One Soviet
researcher estimated that significant electricity
savings are achievable through manufacture of
more energy-efficient appliances and lighting,
optimized use of lighting, elimination of
known losses or "wastes" of electricity, etc.
(Tarnizhevsky, 1987).
Long-Term Potential in the Residential/
Commercial Sector
In the long term, the potential for
reducing energy use in buildings is
considerable. The majority of current per
capita energy consumption in buildings could
be eliminated over the long run by simply
incorporating the best currently available
building and equipment technologies into
housing and commercial building stock as it is
expanded and replaced over the next 50-100
years. Further efficiency improvements could
come from emerging technologies and broader
application of existing technologies. In space
conditioning, examples include "smart
windows," which sense light and adjust opacity
to utilize solar heat and light most effectively,
and new building materials, which may
provide better insulating qualities at a
reduced cost. Existing technologies for large
buildings, such as use of thermal storage and
computer controls, could be applied to small
buildings and residences as well.
As improved building and equipment
technologies are incorporated over time, space
conditioning will probably become a much
smaller component of total building energy
use. Appliances and information technologies
(computers, telecommunications) may become
more important determinants of residential
and commercial energy consumption.
Advanced technologies may provide
comparable or improved services with less
energy. For example, some experimental
concepts have been developed for storing food
that might greatly reduce the need for
refrigeration. As information technology
continues to evolve, it may well provide
improved energy efficiency as a byproduct, as
has been the case in the evolution from
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Policy Options for Stabilizing Global Climate
vacuum tubes to semiconductors to integrated
circuits.
Alternative fuels could also play a more
important role in buildings over the long
term. Advances in solar photovoltaic and
other small-scale renewable energy
technologies may make it economical to
generate most or all of the needed electricity
locally. Hydrogen may become an energy
option for building energy needs by utilizing
or adapting the existing infrastructure for
distribution of natural gas (see PART TWO).
INDUSTRIAL SECTOR
Industrial end uses account for the
largest single component of energy use in the
industrialized countries ~ almost 43% of the
energy consumed in the OECD in 1985 (in
primary energy equivalent terms [U.S. DOE,
1987b]). Actual secondary energy
consumption was about 36%. In developing
countries, if agriculture is included as part of
industry (as it is in this chapter), then the
industrial sector generally consumes an even
higher percentage of total commercially
traded energy. In developing countries as a
whole, industrial energy makes up almost 60%
of total modern energy use. In the USSR
and Eastern Europe, the percentage is slightly
under 50% (see CHAPTER IV).
Industrial use is also an area in which
impressive efficiency gains have been observed
in recent years. In the United States, for
example, "end-use energy consumption per
constant dollar of industrial output declined
by 28% between 1974 and 1984 ~ reflecting
substantial improvements in energy efficiency
as well as the relative decline in output from
energy-intensive industries in this country"
(U.S. DOE, 1987b).
Several researchers have documented
the components of changing industrial energy
use in developed countries (see Ross, 1984,
1986; Goldemberg et al., 1987; and Williams
et al., 1987). One significant component of
declining industrial energy use is a structural
shift to products that are inherently less
energy-intensive to produce. It is now a well-
documented phenomenon that as
industrialized countries proceed beyond a
certain level of economic development and
affluence, their per capita consumption of
some of the most energy-intensive industrial
products (e.g., cement, steel, and durable
goods) declines. Thus, having approached
"saturation" in many energy-intensive
products, industrialized countries will likely
continue to consume less energy per dollar of
GDP in the future as incomes continue to
rise. Major programs to rebuild aging
infrastructure (roads, bridges, water and sewer
systems, etc.) in the U.S. and other OECD
countries are being discussed and could offset
the saturation effect somewhat.
The other major component of declines
in energy intensity over the past decade and
a half has been actual improvements in the
efficiency of production processes. Energy
price shocks of the 1970s often affected
industrial energy users more than other
sectors. As stated by Goldemberg et al.
(1988): "Because the cost of providing them
energy involves much less unit transport and
marketing cost, industrial users are more
sensitive than other energy consumers to cost
increases at or near the point of energy
production." In addition, industrial users,
particularly where energy costs are a
significant component of product cost, tend to
be more aware of and responsive to the
return on investments in energy efficiency
than are customers in other sectors. Ross
(1986) has noted many cases in which
industrial managers have pursued aggressive
efficiency improvement policies in response to
the price signals of the 1970s.
Efficiency improvements to date have
largely been in a few industries that are the
most energy-intensive: petroleum refining,
chemicals, cement, metals, pulp and paper,
glass, clay, etc. (see Table 5-5). There is
reason to believe that efficiency improvements
will continue rapidly in the future in the
energy-intensive sectors of industry in the
developed countries, particularly if real energy
prices begin to rise again. It is also expected
that the structural shifts to less energy-
intensive products will also continue in these
countries (Williams et al., 1987). Technical
options may exist for accelerating these trends
and also taking advantage of additional
efficiency improvements possible in other
industries. Evidence exists that economically
attractive energy conservation investment
V-48
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Chapter V: Technical Options
TABLE 5-5
Reduction of Energy Intensity"
in the U.S. Basic Materials Industries (1972-1983)
Percent
Chemicals'3
Steel
Aluminum
Paper0
Petroleum refining*1
Energy Weighted Reduction
31
18
17
26
10
21
a Generally energy per pound of product, unadjusted for environmental and other changes.
Purchased electricity accounted for at 10,000 Btu/kwh (2.5 Mcal/kwh).
b Not including fuels used as feedstock.
c Not including wood-based fuels.
d Changes in inputs and outputs and environmental regulations have had a particularly strong
impact on petroleum-refining energy. Adjusted for such changes, energy intensity was reduced
26%.
Source: Ross, 1985.
opportunities exist in industries outside of
those few that are energy-intensive. For a
number of reasons these investment
opportunities are often being overlooked
(Ross, 1984, 1986).
In contrast to industrialized countries,
the developing countries generally are in the
midst of, or beginning, a period of rapid
expansion of energy- and materials-intensive
industries to raise per capita income levels.
In addition, industries in these countries
currently use energy far less efficiently than
do similar industries in industrialized
countries. In many cases, this is related to
the government's subsidization of energy
prices, lack of access to the most modern
technologies, and lack of management skills
for identifying and implementing efficient
options (Flavin and Durning, 1988). If
developing countries industrialize without
dramatically improving energy efficiency, the
result would be enormous increases in
industrial energy use. As these countries
develop industrial infrastructure and as their
standards of living rise in the future, the
energy requirements for the production of
basic industrial materials could be enormous.
There is a widening recognition,
however, that this type of growth may not be
sustainable and may indeed become self-
defeating. Continuing along current energy-
intensive industrial development paths may
V-49
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Policy Options for Stabilizing Global Climate
result in increases in energy impoits, which
absorb foreign exchange credits that are
needed for further development. Local
environmental concerns and capital scarcity
may also constrain the conventional industrial
development option. Developing countries
and development assistance organizations are
now beginning to focus much more attention
on the energy consequences of industrial
development decisions.
Technical options may exist for
"leapfrogging" from current obsolete energy-
inefficient technologies directly to very
advanced efficient technologies in some
developing countries (although new policy
actions will be required; see CHAPTER VIII).
In addition, opportunities exist for designing
industrial development based on locally
available alternative fuels, which has been
initiated in some developing countries.
In the USSR and Eastern Europe
countries, significant heavy industrial capacity
is already installed, with energy often used
very inefficiently. For these countries
reducing industrial energy demand may
require structural shifts away from heavy
industry as well as the use of more efficient
industrial technology.
With the technical options identified
below, industrial energy consumption could be
reduced by 25% below levels projected for the
2000-2010 time frame. One recent analysis
indicates that cost-effective conservation could
result in an absolute decline of about 19% in
industrial energy consumption (fuel and
purchased electricity) in the U.S. by the year
2010 (Ross, 1988).
Some available projections based on
trends in structural change and process
technology improvement alone suggest that
industrial energy use in the OECD countries
may not rise significantly over the next 25-40
years (Williams et aL, 1987). Very recent
data for 1987 and 1988 in the U.S. show
sharp increases in durable goods and basic
materials production (U.S. DOC, 1988). If
these very recent trends continue, industrial
energy use in OECD countries could grow
significantly in the future. Industrial energy
consumption in the USSR, Eastern Europe,
and developing countries is expected to
increase substantially under "business-as-usual"
assumptions.
Near-term technical options in the
industrial sector in the three regions are
described below.
Near-Term Technical Options: Industrialized
Countries
Accelerate Efficiency Improvements in Energy-
Intensive Industries
As discussed above, significant
improvements in energy efficiency were made
in the basic materials industries during the
late 1970s and early 1980s (see Table 5-5 for
improvements in key industries). Despite
these improvements, in most industries the
opportunities for further reductions are still
quite large. This is true for two basic
reasons. Industrial process technology has
improved significantly in recent years, and the
pace of energy-related technology investment
has been relatively slow, particularly in
industries that are not growing overall (Ross,
1988).
The steel industry provides one
interesting example. For the integrated, or
ore-based industry (excluding scrap-based steel
making), the average energy intensity in the
U.S. in 1983 was about 31.2 GJ per ton
(Ross, 1987). The reference plant
documented by the International Iron and
Steel Institute (1982) would consume about
19.2 GJ per ton producing roughly the same
mix of products. Thus, if existing U.S.
capacity were replaced with plants equal in
efficiency to this reference plant, it would
produce a 39% savings. The costs and other
implications of such replacement have not
been assessed. Other estimates find a 20%
savings possible, if necessary investments were
made (Barker, 1990).
More energy-efficient technologies, once
proven commercially, will likely be extremely
attractive on the basis of cost-effectiveness,
including improvement in overall process cost
and environmental impact as well as energy
efficiency. Thus, the marketplace can be
expected to encourage all producers to adopt
advanced technologies in the long run. From
the perspective of climate wanning, the
V-50
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Chapter V: Technical Options
important concern is whether there are
opportunities for accelerating this turnover,
either through research initiatives or through
programs to promote more rapid capital
replacement in selected industries.
Other major energy-consuming indus-
tries - petroleum refining, chemicals, pulp
and paper, etc. - are also undergoing
transformations that will result in continuing
declines in energy intensity in the future.
Quantifying the potential energy efficiency
improvements in each major industry and in
various OECD countries will require more
detailed analysis than has been carried out to
date. Technically-feasible improvements (e.g.,
assuming that each industry average improves
to match the energy efficiency of the best
currently-available or emerging technology)
could be much greater. With the exception of
primary aluminum, other energy-intensive
industries have even greater technical
opportunities for energy conservation than the
steel industry (Ross, 1988).
One important component of the
technical potential for reducing energy use in
basic industries is materials recycling.
Recycling of inorganic wastes, such as bottles
and aluminum cans, saves energy and reduces
waste streams. Substituting recovered
materials for virgin materials to produce steel,
aluminum, and glass conserves energy.
Depending upon the types of materials
recycled, estimates of energy savings can range
from an average of 5 GJ per ton of material
recycled (Gordon, 1979) to 25 GJ per ton
(Stauffer, 1988). Recycling 24 million tons of
paper, cardboard, glass, and aluminum (about
16% of our current waste stream) could result
in savings of up to 0.6 EJ (Stauffer, 1988).
Unfortunately, economic policies
discourage recycling and the use of recycled
materials. Differentials in transportation rates
favor virgin loads over secondary loads, and
favorable tax treatment toward production
from virgin materials continues to make
recycled materials more expensive to use. If
these policies were eliminated or reversed
(e.g., creating incentives to boost demand for
recycled products), the technical potential for
energy savings is quite large. Increased
recycling would also have the added benefit of
reducing waste.
Aggressively Pursue Efficiency Improvements in
Other Industries
While there is clearly measurable
progress in the energy-intensive, and therefore
energy-price-sensitive, industries, less progress
has been made in energy efficiency in other
industries. Industries for which energy is not
a major component of product cost frequently
pass up opportunities for investing in energy
efficiency with high estimated rates of return
(Ross, 1984).
The technical potential for energy
savings could be important for widespread
penetration of just a few energy-saving
measures. The Electric Power Research
Institute estimates that 95% of industrial
electricity use is represented by three major
applications: electromechanical drives or
motors, 70%, electrolysis, 15%, and process
heat, 10% (Kahane and Squitieri, 1987).
Recent studies have estimated that cost-
effective replacement of motors and the
addition of variable-speed drives could reduce
total electricity use in motors by as much as
17% in some regions (Geller et al., 1987;
Alliance to Save Energy, 1987).
Comparable efficiency improvement
measures have also been identified for the
other major components of industrial
electricity use (Kahane and Squitieri, 1987).
In addition, many of the efficiency measures
identified earlier for lighting and space
conditioning in large commercial buildings are
also applicable to industrial users. A recent
study examined current electricity-saving
projects in automobile manufacturing plants
in the U.S. and Europe. The results showed
roughly 30% savings from the current cost of
purchased electricity (Price and Ross, 1988).
Increase Cogeneration
Technologies for cogeneration -
production of electricity and heat or steam for
other useful purposes from a single
combustion source - are described in PART
TWO. The primary market for cogeneration
is in large industrial facilities (although large
commercial/institutional and district heating
applications are important in the USSR and
Eastern Europe and are also beginning to be
seen in the U.S.). From industry's
V-51
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Policy Options for Stabilizing Global Climate
perspective, cogeneration is one method for
improving energy efficiency. The industrial
facility benefits, either in the form of
electricity used on-site or revenues from sales
of electricity to the local utility, from the fuel
it would otherwise have consumed solely for
industrial production purposes.
Industrial cogeneration has grown
rapidly in the U.S. since the 1978 passage of
the Public Utilities Regulatory Policies Act
(PURPA), which ensures that cogenerators
(among others) can sell electricity to utilities
at the utility's avoided cost (the cost that the
utility would otherwise have to pay to
produce or obtain the electricity). As of
1985,13 GW of cogeneration capacity were in
operation (Edison Electric Institute, 1985).
Projects that would yield an additional 47
GW have been registered with the Federal
Energy Regulatory Commission (FERC)
through October 1987 (FERC, 1988). One
company specializing in cogeneration has
estimated that cogeneration capacity could
reach 100 GW (equal to about 15% of
current capacity) by the year 2000 (Naill,
1987).
All of these projects tend to reduce
potential greenhouse gas emissions as they
result in more efficient use of energy. To the
extent that industrial cogeneration projects
are based on natural gas or oil -- or industrial
waste products such as black liquor or bark in
pulp and paper -- and displace new coal-fired
electric generating capacity, the net impact on
greenhouse gas emissions (as well as local
environmental loadings) could be much
greater.
Near-Term Technical Options: Developing
Countries
As noted above, developing countries
generally are in the early stages of a rapid
expansion in producing energy-intensive
materials associated with infrastructure
development and widespread access to basic
consumer durables. If this process proceeds
along the path experienced historically by the
industrialized countries, the increases in
energy consumption and CO2 emissions will
be enormous. In fact, the need to import
fossil fuels to support rapid expansion of
heavy industry could become self-defeating,
operating as a brake on the rate at which
some developing countries can industrialize.
Understandably, developing countries
and development assistance organizations are
concerned about alternative approaches to
industrial development that would allow
developing countries to increase economic
activity without having to devote ever-
increasing shares of their foreign exchange
earnings to financing fossil-fuel imports.
Several possible strategies for achieving this
goal are very compatible with concerns about
long-term greenhouse warming.
Practice Technological Leapfrogging
This phrase has been used by
Goldemberg et al. (1987) in discussing
industrial development options for both
industrialized and developing countries.
Theoretically, at least, developing countries
could adopt the most efficient process
technologies currently available, or even push
ahead with experimental technologies as they
invest in major expansions of heavy industry
necessary to foster economic development. If
this strategy were implemented, the projected
massive increases in industrial energy use in
the developing countries would be
significantly reduced.
There are a number of reasons why this
may not occur in practice. Because capital
(and entrepreneurial experience) is scarce in
developing countries, there is a tendency to
avoid risky investments. Conventional wisdom
suggests that these countries should adopt
technologies that are already "mature" in the
industrialized countries. This "conventional
wisdom" has affected decisions both by
developing countries themselves and by
relatively conservative lending institutions
(banks or assistance organizations) called
upon to provide capital. Often, though by no
means always, advanced energy-efficient
technologies require larger capital investments
than older technologies. It is also extremely
important to recognize the differences
between developing countries and
industrialized countries (and among individual
developing countries) in terms of the
availability and cost of certain components of
production ~ labor, capital, and natural
resources.
V-52
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Chapter V: Technical Options
Thus, developing countries will have
difficulty achieving rapid industrial
development with currently mature, but also
relatively energy-intensive, technologies
available from the industrialized countries.
On the other hand, "leapfrogging" to the most
advanced technologies now being developed in
industrialized countries may be inappropriate
in terms of the local availability of labor,
capital, and natural resources. What appears
to be needed is to identify and develop
advanced industrial process technologies that
are appropriate to each developing country's
individual endowment of resources. To the
extent that developing countries move in this
direction, energy efficiency, or at least
efficiency in fossil-fuel use, should be a major
characteristic of the desirable options for
most developing countries. Since many
developing countries have difficulty raising the
capital required for many investments, some
special form of international financial
arrangements may be necessary to assist
developing countries in adopting energy-
efficient technologies as they industrialize (see
CHAPTER VIII for further discussion).
Develop and Use Alternative Fuels
As discussed above, most developing
countries are interested in limiting increases
in fossil-fuel imports associated with
industrialization. For this reason, they will
undoubtedly provide a proving ground for
development of heavy industry based on
alternative fuels.
One option for some developing
countries may be to develop potential
hydroelectric generation resources and base
industrial development on advanced
electricity-intensive processes. (Opportunities
and difficulties in developing hydroelectric
generation are discussed in more detail in
PART TWO.) In general, developing
countries are relatively rich in biomass
resources and, in some cases, undeveloped
hydropower, while they are net importers of
fossil fuels. Thus, the tailoring of industrial
development strategies to local resources will
likely reduce greenhouse gas emissions in
addition to achieving other benefits.
For those developing countries with
abundant coal resources, most notably China,
there may be a tradeoff between energy self-
sufficiency goals and climate warming
concerns. Even in these situations, promoting
the most energy-efficient technologies should
be a common goal. When developing
countries have both natural gas and coal
resources, local environmental and economic
concerns, and consideration of the greenhouse
phenomenon, should all encourage a near-
term emphasis on natural gas.
Increase Industrial Retrofit Programs
A recent report by the U.S. Agency for
International Development (U.S. AID, 1988b)
reviewed the electricity supply-and-demand
situation in a number of developing countries.
The report documented serious concerns in
many developing countries about current or
projected shortages in electricity. However, it
also found that "few achievements have been
made in developing countries in using
electricity more efficiently. The opportunities
are tremendous, and the cost is only a
fraction of the generation expansion option."
According to the report, over 40% of the
electricity use in developing countries is by
electric motors in the industrial (including
agriculture) sector (U.S. AID, 1988b). One
detailed energy analysis in Pakistan identified
specific industrial efficiency improvements,
including improved controls and lighting,
which could reduce industrial energy
consumption by more than 20% in 2005
(Miller et al., undated).
Other recent studies in Kenya and
South Korea indicate that efficiency programs
have been successful in reducing energy use in
heavy industry (Geller, 1986). A detailed
analysis of the electricity conservation
potential in Brazil indicates that
improvements in electric motors and motor
controls could reduce industrial electricity
consumption by an amount equivalent to 8.7
CW of new generating capacity (Geller,
1984). Many of the potential industrial
energy savings in developing countries are
undoubtedly not yet identified because of the
relatively little attention that has been given
to these options in the past. However, the
fragmentary evidence currently available
suggests that these opportunities are much
greater in percentage terms than those in
industrialized countries and are much cheaper
V-53
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Policy Options for Stabilizing Global Climate
than the incremental cost of increasing energy
consumption.
Use Energy-Efficient Agricultural Practices
On a global scale, agriculture accounts
for a small part of "commercial" (excluding
traditional biomass) energy use -- about 3.5%
in 1972-73. However, the percentage in some
developing countries is higher. In addition,
the projected transition in developing
countries from traditional labor-intensive
agricultural practices to modern mechanized
practices is expected to increase the use of
commercial energy in agriculture significantly
in developing countries by the year 2000
(FAO, 1981).
A major goal of most developing
countries is to increase productivity in
agricultural production either for domestic
consumption or for export purposes. If
energy conservation is viewed as a constraint
to such improvements, it generally will not be
viewed as a more important objective.
However, productivity increases may be
possible through several alternative
approaches, with markedly different
implications for energy and employment.
Many developing countries are
interested in holding down imports of fossil
fuels. They may also suffer from widespread
unemployment or underemployment and,
therefore, may seek modernization without
displacement of employment. It is important
that agricultural modernization be
incorporated into an overall development
strategy appropriate to each individual
country. In this context, energy savings may
be achieved in conjunction with other
objectives. Goldemberg et al. (1988) point
out that some agricultural modernization can
occur without such large increases in
commercial energy consumption (and
associated reductions in labor requirements).
Using one type of rice production as an
example, they illustrate that many benefits of
the "green revolution" in increasing yields per
hectare can be achieved with intermediate
approaches that do not go as far in
substituting mechanical energy for labor.
Expanded agricultural energy needs can
also present an attractive opportunity for
biomass energy development. FAO (1981)
projected that an increase of 17 petajoules
(PJ) of oil-equivalent agricultural energy use
would be required to double food production
in developing countries by 2000.4
Goldemberg et al. (1988) calculate that this
amount of energy in the form of methanol
could be produced by thermochemical
processes from 40% of the present organic
wastes (crop residues, animal manure, and
food-processing wastes) in developing
countries. Alternatively, feedstocks could
come from tree plantations representing land
equivalent to 3% of current forest land in
developing countries. Other possible areas
for efficiency improvements include
electromechanical pumping of water for
irrigation, more efficient use of existing water
resources, and the use of alternative energy
supplies such as wind for pumping.
Near-Term Technical Options: USSR and
Eastern Europe
In the Soviet Union and Eastern
Europe, industrial energy use accounts for
nearly 50% of secondary energy use. As a
share of primary energy equivalent (with
electricity conversion losses allocated to end
uses of electricity) it is even larger (Mintzer,
1988). These countries have very high energy
consumption per unit of GNP. One recent
analysis indicates that the current energy
intensity of the Soviet economy is "akin to the
IEA energy economies of the early 1970s," as
shown in Table 5-6 (IEA, 1988). In fact,
while energy intensity in OECD countries was
declining by over 20% from 1973 to 1986,
energy use per unit of GDP in the USSR
actually increased slightly.
Encourage Structural Change
One major reason for the very high
energy/GDP ratio in the Soviet Union and
many Eastern European countries is the large
share of industrial activity devoted to heavy
industry (production of basic materials such as
metals, cement, etc.) which is inherently
energy intensive. Over the past several years,
a widespread belief has been expressed in
these countries that their economies need to
move rapidly toward producing a different
(and less energy intensive) mix of goods and
services (see, e.g., Gorbachev, 1987; Makarov
V-54
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Chapter V: Technical Options
TABLE 5-6
Energy Intensities of Selected Economies
(energy/unit of GDP)
1973
1986
Canada
United States
IEA Pacific
IEA Europe
IEA Total
Soviet Union
0.88
0.76
0.42
0.40
0.56
0.99
0.76
0.57
0.31
0.34
0.44
1.03
Source: IEA, 1988.
and Bashmakov, 1990; Sitnicki et al., 1990;
Jaszay, 1990). The interest in "restructuring"
or structural change is driven primarily by
economic necessity. The economic concerns
have both supply and demand components.
On the supply side, Makarov and Bashmakov
(1990), as well as Sitnicki et al. (1990), report
rapidly rising marginal costs of increasing
energy supplies in the Soviet Union and
Poland. Thus, they argue that economic
growth on the current energy intensive path
will be constrained by the ever-increasing
investment cost of producing more and more
energy.
On the demand side, it is believed that
a shift toward production of consumer goods
and services is necessary to increase living
standards and revitalize these economies. The
mix of goods and services currently demanded
in the more affluent market economies of the
OECD countries requires less basic materials
and considerably more fabrication and
finishing as well as service-oriented economic
activity per unit of GDP. Most of the
countries of Eastern Europe, as well as the
USSR, have indicated their intention to move
toward market economic systems and away
from central planning as the means of
allocating economic resources and activity.
This is viewed primarily as a means of
improving the efficiency of economic activity,
stimulating economic growth and ultimately
raising living standards. To the extent that
these economic reforms are successful, they
will have significant ancillary benefits in
reducing the rate of growth in greenhouse gas
emissions.
Makarov and Bashmakov (1990) provide
several alternative scenarios of economic
activity and energy consumption in the Soviet
Union. In the base case or "business-as-usual"
scenarios aggregate energy efficiency improves
very little through the year 2030. The authors
conclude that continuation of this type of
economic development would require invest-
ments of capital and other resources in energy
production "so large as to preclude possibility
of realizing any but the pessimistic economic
V-55
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Policy Options for Stabilizing Global Climate
growth case." The pessimistic economic
scenario assumes growth of GDP at 2%/year.
In contrast, a "structural change" scenario
results in a 25% decrease in energy per unit of
GDP by the year 2030. This allows more
rapid economic growth (3%/year) while using
about 15% less energy and reducing carbon
emissions by 14% (below the base case).
Sitnicki et al. (1990) report even more
significant reductions in energy consumption
under a structural change scenario for Poland.
Relative to a "business-as-usual" base case, the
structural change case reduces energy
consumption by 47% and carbon emissions by
43% in the year 2030. Jascay (1990) shows
for Hungary that structural change in the
economy could result in significantly lower
energy requirements and carbon emissions in
the future relative to the most recently
published official economic projections.
These analyses suggest that policies being
considered in the USSR and Eastern Europe
to encourage economic growth would also
have significant benefits in reducing
greenhouse gas emissions.
Other Emission Reduction Options
A closer look at some specific
industries verifies the general impression of
energy inefficiency. The USSR is by far the
world's largest producer of steel (WRI and
IIED, 1988). Unfortunately, it is also
apparently close to last in the world in
efficiency. Estimates for 1983 indicate that
the USSR used 31 GJ to produce a ton of
steel as compared to the Japanese standard of
about 19 GJ (Chandler, 1986). As shown in
Table 5-7, the Soviet Union and many
Eastern European countries continue to
produce a large percentage of their steel in
very inefficient "open hearth" furnaces, which
have been virtually eliminated in the OECD.
They also do very little recycling, as indicated
by the small percentage of steel produced in
electric arc furnaces.
One analyst has suggested that Soviet
industry has shown some success in improving
efficiency in their heavy industry with existing
technology (e.g., "housekeeping" measures,
refinements of existing technologies), but has
failed to assimilate distinctly different and
inherently less energy-intensive technologies.
An example is the cement industry, a heavy
energy-using sector for which energy use can
be greatly reduced by switching from the wet
process to a newer dry calcining process.
Although the dry process is available in the
Soviet Union, it has not been widely utilized
(Hewitt, 1984).
There are several reasons for the
extraordinarily high energy intensity of
Eastern European industry. The Soviet
Union (and to a lesser extent Eastern
Europe) has enormous energy resources and
has historically invested heavily in energy
development due to national economic policy
rather than demand. Hence, scarcity of
energy resources has not provided an
incentive to conserve. In addition, the "mark-
up" pricing systems used in these countries
do not provide a strong incentive for
efficiency improvements. In fact, it has been
argued that the reward system has actually
provided managers with an incentive to
consume more energy (Chandler, 1986).
More recently, the value of energy
efficiency has been recognized by Soviet
leadership. As described by Soviet energy
analysts, "the energy economy of the Soviet
Union is entering a new period of develop-
ment. The most economical and favorable
located oil and gas resources ... are
gradually running out" (Makarov et al., 1987).
The result is that development of new energy
resources is much more expensive and
difficult than in the past. One result of rising
costs of energy development has been the
explicit inclusion of energy efficiency measures
in central economic and energy planning.
Targets have been set that would result in
more than a 20% reduction in the energy
intensity of the Soviet economy (Makarov et
al., 1987).
The Soviet Union has historically done
very well in the utilization of industrial waste
heat for electricity generation (cogeneration)
and for other heat needs, such as district
heating. This trend is continuing. In the
Leningrad region, for example, the 1981-1990
energy plan calls for reducing projected
industrial energy use by about 2 EJ through
a combination of improved industrial
technology and expanded use of waste heat
V-56
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Chapter V: Technical Options
TABLE 5-7
Innovation in Steel Production Technology
Selected Countries, 1985
Country
Economy Type
"Inefficient" "Recycling"
Open Hearth Electric Arc
(% of production)
Spain
Italy
South Korea
United Kingdom
Japan
West Germany
Brazil
United States
Romania
China a
Yugoslavia
India a
Poland
East Germany
Hungary a
Soviet Union
M
M
M
M
M
M
M
M
C
C
C
C
C
C
C
C
0
0
0
0
0
0
4
7
29
31
34
42
42
34
51
57
61
53
31
29
29
19
25
33
22
19
26
19
15
31
13
11
M = Market-oriented; C = Centrally-planned.
a Though this country's agricultural economy is market-oriented, its indi^try is not.
Source: Chandler, 1986.
V-57
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Policy Options for Stabilizing Global Climate
for both electricity and other heat needs
(Glebov and Kovlenko, 1987).
In addition to efficiency improvements,
other options for reducing greenhouse gas
emissions from industry in the USSR and
Eastern Europe are possible through fuel
switching. Although the major resources are
generally located far from current industrial
centers, the Soviet Union has the world's
largest proven recoverable natural gas reserves
in the world, amounting to about 39% of the
World total (IEA, 1988). In addition, its
undeveloped geothermal and hydroelectric
resources are significant (as discussed in
PART TWO). It would be technically
possible, therefore, for the USSR to substitute
various alternative fuels for current and
projected coal use in the industrial sector,
although the costs of such substitution have
not been well analyzed.
Long-Term Potential in the Industrial Sector
Over the long term, technological
options for improving efficiency in industrial
energy use are very speculative. Several
concepts advanced by various analysts may
warrant further study to identify potential
options for reducing long-term industrial
demand for fossil fuels.
Structural Shifts
Over the long term, shifts in the
structural composition of industrial activity
will undoubtedly continue, with significant
energy consequences. As discussed by Ross et
al. (1987), production of basic (and inherently
energy-intensive) materials has tended to
decline over time as a share of GNP after an
economy achieves a certain level of affluence.
There are three components of this shift:
• substitution of new (and often
less energy-intensive) materials;
• product and production design
changes that result in more efficient materials
use; and
• saturation of major markets for
material-intensive products, including
infrastructure and material-intensive consumer
products.
These effects can be expected to
continue in the future and to some degree are
incorporated in all the scenarios of future
energy use presented in this report (see
CHAPTER VI). With combinations of
policies, such as economic incentives and
aggressive research and development, these
effects can be accelerated considerably,
especially in the developing countries where
major increases in industrial energy use are
expected. It is currently very difficult to
identify, much less quantify, the effects of
actions to achieve the technical potential.
Further study of long-term trends in the
structure of industrial activity and specific
policy options for influencing these trends is
needed.
Advanced Process Technologies
As pointed out by Ross (1985), major
reductions in energy intensity in industrial
processes can come about through "revolu-
tionary" change in process technology.
Typically, such change is not motivated
primarily by energy conservation; however,
large reductions in energy intensity often
result from technological advances. As an
example, advanced steel-production technology
now under development could result in very
large energy savings per unit of output.
About 40% of the energy used in iron and
steel production is related to shaping and
treating. Advanced processes utilize
controlled solidification, often very rapidly, of
thin castings that approximate the final shape.
When fully developed, this technology should
eliminate almost all of the energy use
currently associated with rolling and shaping
(Ross, 1985).
In the petrochemical industry, research
is currently underway to identify advanced
separation techniques that could eliminate
many of the losses inherent in the current
distillation process. Gas separation
membranes, gas adsorption, and liquid mass
separating agents are all currently commercial
for very specialized petrochemical applications
and use considerably less energy than the
distillation processes they have replaced (Mix,
1987). Over the long term, wider applications
of these or similar technologies may further
reduce process energy requirements.
V-58
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Chapter V: Technical Options
In general, advanced technologies are
attractive because of the lower total cost,
better quality control, reduction in
inventories, greater flexibility, etc., as well as
the improved energy efficiency. It is difficult
to identify possible process technology
improvements that could become available
through research and development over the
long term, although it is likely that energy
efficiency improvements will be part of these
developments.
Another long-term area of process
technology advancement is the use of
biological phenomena in production processes.
Although it is difficult to even identify
specific applications of biological processes at
this time, they appear to offer possible
improvements in the speed, control, and
precision of process technologies (Berg, 1988).
As such technologies emerge, they will
undoubtedly offer additional opportunities for
reductions in fossil energy use. Industrial
policies designed to stimulate technological
advances and capital turnover will ultimately
also lead to reduced energy requirements.
Non-fossil Energy
Although it is likely that energy
intensity of industrial activity will continue to
decline over the long term, significant levels
of energy consumption will no doubt still be
required. Opportunities exist for meeting
these demands with non-fossil energy sources.
Many industrial technology experts (see, e.g.,
Berg, 1988; Schmidt, 1987) have suggested
that increased use of electricity in industrial
processes over the long run is likely because
of its superior characteristics of controllability
and minimal loss or error.
Even though production of electricity
involves large losses, this is often offset
because the more sophisticated and precise
production processes it allows are generally
less energy-intensive at the end use.
Increasing electrification of industrial
processes at the end-use point allows for a
wide variety of alternative generation options
(as discussed in PART TWO), which can
reduce greenhouse gas emissions.
In addition, one analyst has suggested
that economic competition will cause energy-
intensive industries over the long run to
locate in areas where isolated resources of
cheap and hard-to-transport energy are
available. Examples cited include natural gas
and hydro locations in Canada, Brazilian
hydropower sites, and natural gas locations in
the Middle East (Ross, 1985). The same
logic could also apply to locations with
geothermal and solar resources as those
technologies become competitive. Policies
could be implemented to discourage fossil-fuel
use (see CHAPTERS VH and VHI), as well as
to encourage movement of heavy industry to
locations where renewable resources are
economically attractive.
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Policy Options for Stabilizing Global Climate
PART TWO: ENERGY SUPPLY
This section discusses technical options
for reducing greenhouse gas emissions by (1)
making more efficient use of fuels for power
generation and (2) altering the types of
energy supplies we use. These two goals have
one common objective: to supply a similar
amount of useful energy services compared to
current energy consumption practices, but in
such a way that greenhouse gas emissions are
minimized. Options for reducing greenhouse
gas emissions in end-use applications,
particularly by improving energy efficiency and
switching fuels, were discussed in PART ONE:
ENERGY SERVICES. This section focuses
on possible options for improving the delivery
of energy services by reducing the losses
during energy production and conversion
processes. Additionally, the types of energy
supplies can be altered by developing sources
of energy that do not emit greenhouse gases.
The first part of this section discusses
possible options for altering current patterns
of fossil fuel use. This is clearly one of the
highest near-term priorities, since as discussed
in Chapter IV, current commercial energy use
globally is dominated by fossil fuels. In many
cases, however, options exist for reducing
emissions from these applications. This is
followed by a discussion of possible supply
alternatives to fossil fuels, including increased
use of biomass, solar resources, additional
renewable energy resources, nuclear power,
and options for enhancing energy storage and
delivery to final consumers.
FOSSIL-FUEL OPTIONS
As discussed in Chapter IV, fossil-fuel
consumption is responsible for the vast
majority of CO2 emissions. On an energy-
equivalent basis, coal produces the most CO2
(about 25 kg C/gigajoule); oil, about 80% that
amount (about 20 kg C/gigajoule); and natural
gas, about 55-60% that amount (about 14 kg
C/gigajoule). Given these rates of CO2
emissions, fossil-fuel consumption would have
to be drastically reduced or eliminated over
the long run to control greenhouse gas
emissions. With the current global reliance
on fossil fuels, however, the shift away from
fossil fuels cannot be accomplished easily,
even with international agreement to pursue
this objective. Steps can be taken now to
begin or accelerate the transition to non-fossil
energy by minimizing the greenhouse impact
of the fossil fuels that are used. Possible
actions include improving the efficiency with
which fossil fuels are produced and convened
to electricity, switching from more carbon-
intensive fuels to less carbon-intensive fuels
(e.g., from coal to natural gas), and applying
various engineering controls to reduce
emissions of greenhouse gases during the
production and consumption of fossil fuels
(e.g., NOX control, CH4 recovery).
Since one of the primary uses of fossil
fuels currently is the production of electricity,
one potential option is to produce electrical
power more efficiently, using less energy input
to produce electricity. For example, in the
U.S. during the 1950s and early 1960s, the
efficiency of powerplants consuming fossil
fuels increased from 25% to about 32% (see
Figure 5-5). This improvement has stalled
since the early 1960s because of fewer
technical improvements in combustion
techniques, higher energy consumption by
auxiliary equipment used for pollution control
(e.g., electrostatic precipitators for paniculate
removal and scrubbers for SO2 removal), and
increased use of less efficient fuels, such as
subbituminous coal and lignite.
Although electricity production is
currently one of the primary uses for fossil
fuels, other applications have been proposed
in order to meet future energy needs.
Specifically, as conventional petroleum
resources are depleted, it is possible that
much of the demand for liquid (oil and
natural gas liquids) and gaseous (natural gas)
fuels will ultimately be met by synthetic fuel
production from solid fossil fuels. Although
there is currently little synthetic fuel
V-«0
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Chapter V: Technical Options
FIGURE 5-5
AVERAGE EFFICIENCY OF POWERPLANTS USING FOSSIL FUEL
1951- 1987
40
- 30
9
U
20
10 —
I I
I I
1900 1988 19*0 19H 1970 1978
Year
Av«rag« »f ftcUncy at aH •xtothHI coal, «0, and natural gat powcrplanU.
19*0 1968 199O
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Policy Options for Stabilizing Global Climate
production in the world, processes have been
developed to convert relatively abundant solid
energy resources such as coal, oil shale, and
tar sands to liquid or gaseous products that
could be consumed in the same end-use
applications as more conventional resources.
The production of synthetic fuels,
however, typically requires the consumption of
significant amounts of energy to produce the
liquid or gaseous fuels. These conversion
processes produce greenhouse gas emissions,
particularly CO2, so that the total emissions
per unit of energy are higher for synthetic
fuels than for conventional fossil fuels. For
example, the CO2 emissions from production
and consumption of liquid fuels from coal is
about 1.8 times the amount from conventional
liquid fuels from crude oil (see CHAPTER IV
for further discussion).
The following sections explore possible
options for reducing the greenhouse impact of
fossil fuels. Using fossil fuels more efficiently
is discussed, including refurbishment of
existing powerplants, repowering opportunities
(including application of "clean coal
technologies"), and cogeneration. Greater
use of natural gas is then discussed since it
produces less CO2 than oil or coal. Methods
for controlling greenhouse gas emissions are
also presented.
Refurbish Existing Powerplants
Energy use at existing powerplants can
be reduced by refurbishing the plant to keep
it operating at optimal efficiency. Over time,
these efficiencies decline due to wear and
various aging processes. For many economic
reasons it has become clear over the past
decade that utilities in the U.S. are planning
to keep existing powerplants in service longer
than initially planned (Democker et al., 1986).
It is likely that this trend will occur globally
as well to minimize the need to invest in new
powerplants. As these powerplants age,
however, declining efficiency will become
more widespread than in the past.
In response, the U.S. electric power
industry has developed new techniques for
extending the life of powerplants. The extent
of efficiency improvement depends on how
badly the specific plant had degraded and the
extensiveness of the upgrades. Increases in
efficiency in the range of 3-4% appear to be
possible at many existing units, with even
greater improvements possible in some cases
(PEI, 1988).
In developing countries, the
opportunities for improving the efficiency of
electricity generation may be much greater.
According to a recent study by U.S. AID
(1988b), "The majority of thermal powerplants
in developing countries operate at lower-than-
design capacity and efficiency." Many of these
powerplants use more than 13 MJ5 of fuel to
generate a kWh of electricity, compared to
typical design heat rates of 9-11 MJ/kWh. It
is estimated that a rigorous program of
powerplant rehabilitation could improve
overall fuel use efficiency for thermal power
generation by 10% or more in most
developing countries (U.S. AID, 1988b).
Pursue Clean Coal Technologies
As new powerplants are constructed to
meet increasing electricity needs, many of
these plants are likely to be fossil fueled. To
the extent that new powerplants use fossil
fuels, greenhouse gas emissions can still be
reduced by using the most efficient conversion
technologies. The U.S. Department of
Energy, the Electric Power Research Institute,
and many other organizations have been
investing significant funding in research,
development, and demonstration of "clean
coal technologies" designed to allow burning
of coal to generate electricity with maximum
efficiency and minimum environmental impact
(U.S. DOE, 1987d). These technologies offer
the potential to significantly reduce the
amount of traditional air pollutants such as
sulfur dioxide and nitrogen oxides. However;
they may also affect the amount of
greenhouse gas emissions, particularly for
those technologies that improve the overall
efficiency of convening coal to electricity.
For example, some of these technologies such
as the Kalina Cycle could improve efficiency
by at least 10% relative to conventional coal
combustion technologies.
Three of these advanced technologies
currently in the demonstration phase are
atmospheric fluidized bed combustion
(AFBC), pressurized fluidized bed combustion
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Chapter V: Technical Options
(PFBC), and Integrated Gasification/
Combined Cycle (IGCC). AFBC relies on
CO2-emitting limestone or dolomite and is
likely to be very similar in efficiency to
conventional technology, and therefore, not
beneficial in reducing CO2 emissions.
Moreover, it is believed research has indicated
that this technology may significantly increase
N2O emissions as compared with conventional
coal-fired powerplants. The PFBC and IGCC
systems, however, can be combined and are
projected to increase conversion efficiencies as
much as 10-20%, with corresponding
reductions in CO2 emissions per unit of
electricity produced (U.S. DOE, 1987d).
Clean coal technologies can be used for
newly constructed powerplants, but also to
"repower" existing powerplants. In
repowering, the basic combustion components
of existing powerplants are replaced with one
of the new technologies. Additionally, new
components, such as a gas turbine cycle, may
also be installed in combination with some
refurbished components of the existing
powerplant. The result is a hybrid plant with
performance very much like that of an
efficient new unit.
Increase Use of Cogeneration
Cogeneration refers to the production
of both steam and electricity from the same
source; the steam is used to meet heating and
process requirements at the facility, and the
electricity is used on-site or sold to electricity
customers. Because it is more energy-efficient
than conventional generating options, it has
been encouraged in the U.S. recently by many
regulatory and legislative initiatives. For
example, the Public Utilities Regulatory
Policy Act (PURPA) encouraged Cogeneration
by establishing a process ensuring that
cogenerators with low production costs could
sell this cogenerated electrical power to
electric utilities.
As discussed earlier in PART ONE,
Cogeneration has been very popular with large
industrial energy users as one approach for
reducing their overall energy costs. Most of
the approximately 18 GW of currently-
operating Cogeneration projects in the U.S.
and an additional 29 GW under active
development fall into this category (Williams,
1988). Similarly, as electric utilities face more
competition from industrial cogenerators and
independent power producers (i.e., companies
that produce and market power but are not
regulated as utilities), they may choose to
retrofit some existing generating facilities with
Cogeneration, using the waste heat from
electricity production for district heating or
industrial process heat applications.
Engineering assessments have shown this
potential retrofit option to be economically
attractive for powerplants that burn coal and
are located close to steam load centers (Hu et
al., 1984), though other fuel sources can be
used.
Substitute Natural Gas for Coal
Natural gas (which is primarily
methane) has 55-60% of the carbon per unit
of energy as coal. In applications such as
electricity production where coal is frequently
used, switching to natural gas would
substantially decrease CO2 emissions. As
discussed previously in PART ONE, natural
gas is currently used in several key end-use
applications, particularly in a wide variety of
industrial energy applications and in
residential and commercial space heating. In
addition to its end-use potential, natural gas
can be used as a fuel for electricity
generation. The discussion below focuses on
the technical options and advantages of using
natural gas as a fuel for electricity generation.
The role of natural gas as an end-use fuel and
a fuel for electricity generation, however,
depends on the natural gas resources available
and the cost at which these resources can be
supplied.
Natural Gas Use At Existing Powerplants
There are several near-term alternatives
for increasing the use of natural gas for
electricity generation. One relatively
inexpensive option would be to increase the
utilization of existing natural gas- and oil-fired
(most of which can also consume natural gas)
powerplants. For example, in 1987 average
capacity utilization rates for U.S. oil- and gas-
fired powerplants were 40%, compared with
58% for coal-fired powerplants. Thus, there
is some technical potential to increase gas use
by increasing the utilization of natural-gas-
fired powerplants. However, these plants are
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Policy Options for Stabilizing Global Climate
utilized less because the variable (operating
and maintenance) cost of power is higher at
most oil and gas plants than at coal, nuclear,
and hydro powerplants. In addition, oil- and
gas-fired powerplants can be easily operated
intermittently and with less wear on the
systems (i.e., to meet peak load conditions).
Since electric utilities (usually) produce
electricity with their least expensive
powerplants, policies would first have to be
adopted to increase utilization of natural gas
capacity.
Advanced Gas-Fired Combustion Technologies
An additional option for increasing
natural gas use is to construct new gas-fired
combined cycle or combustion turbine
powerplants. Although the variable cost may
be higher, these powerplants cost significantly
less to build than coal-fired powerplants and
are typically more energy efficient. They
could also be part of a near-term solution
since the lead times for gas-fired plant siting
and construction average about 2-4 years
versus 6-10 years for coal-fired powerplants.
These advanced combustion technologies are
not in greater use primarily because of
investors' expectations that the costs of
natural gas over the operating life of the
facility would be substantially higher than
other fuel alternatives such as coal. As a
result, despite the lower capital costs of these
technologies, electric utilities have often
invested in other alternatives because total
generating costs of combined cycle or
combustion turbine technologies have been
perceived to be greater than those of coal-
fired powerplants.
Combustion Turbines: Simple/Combined
Cycles. Combustion turbines are similar to jet
aircraft engines in that fuel is burned in
compressed air, with the combustion gases
then used to turn a turbine for electricity
generation. This process is known as a
simple-cycle turbine. After the hot gases are
used to produce electricity, the exhaust gases
can be used to convert water to steam in a
steam turbine. Together these two processes
generate power in a process known as
combined cycling. Most combustion turbines
in use are simple cycles, which are used
primarily for peak power requirements due to
their favorable intermittent operating
characteristics (primarily their ability to
increase power production quickly) and low
capital costs, although operating costs are
high. Combined cycle capital costs are higher
but the technology uses fuel more efficiently,
and hence, is currently preferred for units
expected to be utilized more frequently.
Aeroderivative Combustion Turbines.
Recent advances in jet engine (aeroderivative)
technology, including new materials and
designs that enable combustion to occur at
higher temperatures, have made turbines more
efficient. Many of these advances are being,
or could be, applied to turbines for generating
electric power. Existing simple and combined
cycle systems have efficiencies of about 32%
and 42%, respectively, compared to new
conventional coal-fired powerplants, which
have efficiencies of about 33-35%. Recent
advances in aeroderivative technology could
significantly improve these cycle system
efficiencies. One technology that has been
recently commercialized in California is the
steam-injected gas turbine (STIG). STIG
units take any steam not needed for process
heat requirements and inject it back into the
combustor for added power and efficiency. In
a simple-cycle application, the efficiency of
the turbine might be 33% with an output of
33 MW, while with full steam injection the
efficiency would increase to 40% with an
output of 51 MW (Williams, 1988). An
improvement in steam injection that has been
proposed is the intercooled steam-injected gas
turbine (ISTIG). ISTIG cools the compressor
bleed air used for turbine blade cooling,
allowing a much higher turbine inlet
temperature. With this technology, the
single-cycle efficiency cited above would
increase from 33% to 47% and output from
33 MW to 110 MW; the estimated capital
cost of ISTIG is about $400/kW (Williams,
Factors Affecting Use of Natural Gas
Resource Base. There is a significant
amount of research and debate over the
quantity of natural gas that is available. As
discussed in Chapter IV, global gas resources
are estimated to be significantly smaller than
global coal resources (resource estimates by
the World Energy Conference indicate that
coal resources are about 30 times greater than
V-64
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Chapter V: Technical Options
gas resources). Within the U.S., there is
disagreement over the size of this difference.
One source has indicated that in the U.S., the
natural gas resource base is as large as the
coal resource base when one compares the
economically recoverable and usable
resources; the supply should be adequate for
hundreds of years (Hay et al., 1988). On the
other hand, based on 1985 consumption levels
of about 18.6 EJ, the U.S. Department of
Energy (U.S. DOE) has estimated that
technically recoverable U.S. gas resources
would last only about 70 years at current
usage rates, and only about 45 years if limited
to supplies that could be marketed for about
a maximum of S5/GJ (see Table 5-8). In
contrast, U.S. coal reserves are estimated to
be about 350 times greater than 1985 U.S.
consumption levels (U.S. DOE, 1988d).
Significant gas reserves are available
outside of the U.S., though they are not well
matched with potential demand centers.
More than half of the world's proved reserves
are located in just two countries, the USSR
and Iran. Soviet gas reserves alone are eight
times those available in the U.S., and Iran has
over two and one-half times the quantity of
U.S. gas reserves. While roughly 30% of the
world's proved reserves of natural gas exist in
the Middle East, only 5% are in Western
Europe, and less than 1% are in China and
Japan combined (British Petroleum Company,
1989).
Cost. In addition to the potential limit
on gas supplies, there are also questions
about the cost of additional gas supplies, the
location of supplies vis-a-vis the areas of
demand, the cost and availability of improved
transmission and distribution systems, and in
the case of international trade in liquified
natural gas (LNG), the costs of liquefaction,
transportation, and regasification facilities.
Concerns over the cost and availability
of natural gas may appear unwarranted given
the existence of excess capacity and falling
prices in the U.S. gas industry in recent years.
However, these market conditions may be
temporary. Current excess capacity followed
a period in the 1970s when natural gas was in
short supply. The recent changes are
primarily because of natural gas price
deregulation, which allowed prices to increase
from previously controlled levels. The price
increases had two effects: (1) demand
decreased and (2) supply increased. The
duration of the current slack market
conditions is a matter of much debate, but as
the demand and supply for natural gas come
into balance, natural gas may no longer be
available at current prices.
The relevance of these concerns is not
that natural gas cannot play a role in reducing
CO2 emissions; unquestionably, it can.
However, the ability of natural gas to replace
fuels with higher carbon content is a function
of the quantity of natural gas available and
the cost at which natural gas can be supplied
to consumers. That is, even if natural gas is
available, the extent to which it replaces other
fuels will depend on its available supply and
cost relative to alternative fuels and the
available pipeline delivery system. Any
policies promoting increased use of natural
gas must recognize these factors.
Electric Utility Gas Consumption. In
1985, gas consumption by U.S. electric
utilities was about one-fifth of total U.S. gas
use, or about 3 EJ. Even though U.S. electric
utilities consume only a minor fraction of
natural gas, they can have a large impact on
prices because they are frequently the
marginal buyer. That is, utilities often have
alternative generation options such as oil or
coal and can easily switch, unlike many
residential or commercial gas users who do
not have such flexibility. Increases in electric
utility demand for natural gas would affect
residential, commercial, and industrial
customers, who would be charged higher gas
prices. For example, assuming 13 EJ of
consumption, a Sl/gigajoule price increase
would increase natural gas costs by $13 billion
per year among all consumers.
To replace a significant amount of
electric utility coal consumption would require
a very large increase in natural gas
consumption. For example, utility gas
consumption in 1985 was 3 EJ, whereas coal
consumption by utilities was about 15 EJ.
Thus, to replace 40% of coal consumption (6
EJ), a 200% increase in utility gas
consumption would be necessary (assuming
current efficiencies), raising U.S. electric
utility gas use to unprecedented levels. As a
V-65
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Policy Options for Stabilizing Global Climate
TABLE 5-8
Total U.S. Gas Reserves And Resources
(Exajoules)
Technically
Recoverable Gasa
Recoverable Gas by Priceb
<$3/Mcf $3-5/Mcf
Lower 48 States (Conventional)
Proved Reserves, 12/31/86, Onshore and Offshore
Inferred Reserves/Probable Resources, 12/31/86, Onshore
Inferred Reserves, 12/31/86, Offshore
Extended Reserve Growth in Nonassociated Fields, Onshore
Gas Resources Associated with Oil Reserve Growth0
Undiscovered Onshore Resources
Undiscovered Offshore Resources'1
Subtotal
171
91
25
60
66
95
58
533
19
12
63
30
125
Lower 48 States (Unconventional)
Gas in Low-Permeability Reservoirs
Coalbed Methane
Shale Gas
Subtotal
194
52
33
279
75
9
11
95
53
4
_5
63
Alaska
Reserves
Inferred Reserves (Cook Inlet Area)
Undiscovered, Onshore and Offshore
Total
Subtotal
36
3
100
139
1,278
8
3
2
13
640
0
0
2
2
189
8 Volumes of gas judged recoverable with existing technology.
b Volumes of gas judged recoverable with existing technology at wellhead prices shown (1987$). Mcf represents one thousand
cubic feet (about 1.1 GJ), which is a common measure of gas quantity.
c Judged at oil prices of <$24/bbl and $24-40/bbl.
d Outer Continental Shelf.
Source: U.S. DOE 1988c.
V-66
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Chapter V: Technical Options
result, any policy to increase natural gas use
needs to recognize possible impacts on gas
supply and the market price of gas.
Methods of Increasing Gas Resources
Two ways to increase the available
supply of gas to consumers are to (1) reduce
or capture methane emissions during the
production and distribution of natural gas and
(2) extract methane from coal seams. In each
of these cases, increasing the amount of
methane available to consumers would often
have other positive environmental benefits by
reducing the amount of CH4 and CO2 emitted
to the atmosphere.
Reduce or Capture Emissions from
Natural Gas Flaring, Venting, and Leaking. As
discussed in Chapter IV, during the
production of oil and natural gas, natural gas
may be vented to the atmosphere as CH4 or
flared (producing COj).6 Additional CH4
emissions are also produced during the
refining, transmission, and distribution of
natural gas. These emissions can be reduced
through more careful production and
maintenance procedures or by capturing the
gas for on-site use or sale to gas customers.
Gas vented or flared in the U.S.
represents around 0.5% of annual domestic
production, while gas losses during
transmission and distribution have been
estimated to represent less than 0.5% of gas
consumption (A.G.A., 1989). These values
are presumed to be much lower than the
global average because of several factors,
including regulations prohibiting the flaring
and venting of gas in the U.S., and the
existence of markets and infrastructure to
transport and sell the gas. In areas in the
U.S. where no market for the gas exists (e.g.,
Alaska), gas produced during oil production
activities is reinjected into the reservoirs in
order to maintain pressure. Opportunities
exist in the U.S. for reducing gas (methane)
losses during transmission and distribution,
such as through maintenance and replacement
of old, outdated distribution lines. Globally,
a larger percentage of natural gas is vented or
flared because of fewer regulations governing
these releases and a less-developed
infrastructure for utilizing the gas. The
quantities of gas vented or flared could be
reduced through development of an
infrastructure to market the gas or through
regulations governing these releases.
Extract Coalbed Methane. As discussed
in Chapter IV, during coal mining,
particularly underground mining, methane
trapped in the coal seam is released.
Historically, trapped coalbed methane has
been viewed as a safety problem since
methane can accumulate in the coal mine to
the point where it can explode. U.S. mining
regulations require that underground coal
mines be adequately ventilated to prevent this
problem. Recently, however, there has been
a growing interest in utilizing coalbed
methane as a natural gas resource.
Methane extraction from coalbeds,
which is being done commercially in a few
areas in the U.S., differs from traditional
natural gas production in several respects.
Perhaps most importantly, the gas production
profile differs from conventional gas wells in
that maximum output generally occurs two to
three years after the wells are in place,
compared to immediately afterwards for
conventional wells. For a given production
site, more wells are drilled to maximize
methane flow. Also, because these wells are
drilled into available coal seams, they are
generally quite shallow (i.e., not more than
3000-4000 feet deep). While the relatively
shallow access helps to reduce drilling costs,
more ground water is encountered, requiring
additional efforts to extract clean gas.
Because coalbed methane recovery is a
relatively new industry, it is difficult to
quantify the potential size of this resource.
In addition to offering another gas source,
coalbed methane recovery could occur before
the coal seam is mined. Such recovery would
help to ease the problem of methane buildup
in coal mines (possibly reducing coal mining
costs) and reduce the emissions of CH4 to the
atmosphere that result from current coal-
mining operations.
Employ Emissions Control Technologies
One technological option for reducing
the amount of greenhouse gas emissions is
the use of emission control techniques on
combustion technologies that generate these
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Policy Options for Stabilizing Global Climate
emissions. NOX and CO2 emission control
options for stationary combustion sources,
such as electric utility powerplants, are
discussed below.
Controls
Nitrogen oxides (NOX) are formed
during combustion primarily by the
combination at high temperatures of nitrogen
(N2) and oxygen (O^ naturally found in the
air, and secondarily by the nitrogen that is
found in fuels such as coal and oil. Of these
two factors, the combustion temperature is
usually the most critical factor affecting the
NOX emission rate. Fluidized bed combustion
is one possible way to significantly reduce
NOX emissions. There are several additional
available methods for controlling NOX
emissions (based on NAPAP, 1987):
• Low Excess Air (LEA)fOverfire
Air. These two combustion techniques alter
the flow of air during the combustion process.
With low excess air the amount of excess
combustion air is reduced, thereby lowering
emissions by as much as 15%. With overfire
air, some combustion air is redirected to a
region above the burners, which can reduce
emissions by as much as 30%. Potential
drawbacks are incomplete combustion of the
fuel, increased smoke, and the extensive plant
modifications that may be required.
• Low NOX burners. This control
technique operates within the furnace to limit
the mixing of coal and combustion air to
create a low-temperature combustion zone.
This technique can be applied to existing and
new units, although experience on existing
units is quite limited. Removal efficiencies in
new units approach 50%.
• Air and Fuel Staging. When
combined with low NOX burners, these two
controls can achieve up to 75% removal
efficiencies. With air staging alone, up to
50% of the combustion air is directed above
low-NOx burners. With fuel staging (also
known as reburning) additional fuel is burned
in a region above the burners to create a fuel-
rich combustion zone. Within this zone NOX
is destroyed by reducing conditions that
convert NOX to molecular nitrogen. This
technique has been used in full-scale
applications abroad, but only in pilot-scale
facilities in the U.S.
• Selective Catalytic Reduction
(SCR). SCR is a post-combustion control
technology that uses a catalyst to reduce NOX;
reductions of 50-80% are possible. Its
advantages include relatively simple
equipment, no byproduct, and minimal
efficiency loss. Its cost-effectiveness is
unproven, however, and depends on catalyst
lifetime, which depends primarily on fuel
characteristics. SCR has been used abroad on
low-sulfur coal, particularly in Japan and
West Germany. Testing of this technology's
performance on U.S. high-sulfur coal began in
late 1989.
CO2 Controls
Technologies have been developed to
remove carbon dioxide from powerplant flue
gases and dispose of it in a manner that
prevents it from reaching the atmosphere.
These technologies, however, are unproven
and very costly at this time. In one process,
carbon dioxide in the flue gas is mixed with
water in a solvent solution at temperatures
slightly above ambient conditions. The
carbon dioxide binds to the reagent and
passes to a regenerator chamber where
temperatures are elevated. The reverse
reaction then occurs and CO2 is released,
removed, pressurized, and liquified. The
reagent is regenerated and reused. The liquid
carbon dioxide could then be used for
commercial applications, or pumped to deep
ocean locations, deep wells, or salt domes for
permanent disposal. The volume of CO2
currently produced dwarfs existing markets for
reuse, however, so any control program of
significant scope would involve very large
disposal costs.
In order to understand the relative
costs of this CO2 removal process, the costs
of this system are compared to a conventional
sulfur dioxide scrubber in Table 5-9. The
carbon dioxide scrubber is 250-350% more
costly than the sulfur dioxide scrubber and
would increase electricity costs by 60-80%.
The cost of transporting and disposing of the
large volume of removed CO2 has not been
adequately assessed, but is likely to
substantially increase this estimate. Although
V-68
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Chapter V: Technical Options
TABLE 5-9
CO2 Scrubber Costs Compared To SO2 Scrubber Costs'
Capital Cost ($/kW)d
Scrubber
Pipeline/Disposal
Variable Operation and Maintenance
Costs (mills/kWh)
Energy Penalty (%)
Capacity Penalty (%)
Fixed Operation and Maintenance
Costs (S/kW-yr)
Total Cost (mills/kWh)e
CO2 Scrubberb
810
80-710
NA
25
22
^*
36-47
SO2 Scrubber0
220
NA
3.5
4.5
2.5
JQ
10.7
a Ninety percent removal of both CO2 and SO2.
b Source: Steinberg, Cheng, Horn, 1984.
c Source: U.S. EPA Interim Acid Rain Base Case Estimates, 1987.
d Greenfield Site.
e Sixty-five percent capacity factor; 9% capital charge rate; incremental power costs 65 mills
per kilowatt-hour; new plant costs of $l,200/kW; fixed O&M for CO2 scrubber is assumed
to be $10 per kilowatt-year for comparison purposes only, actual costs could well be higher,
1988 dollars assumed to be worth 42% less than 1980 dollars.
V-69
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Policy Options for Stabilizing Global Climate
some CO2 could be used for enhanced oil
recovery or stored in exhausted oil and gas
wells, large-scale disposal would most likely
have to be in the ocean. This raises serious
environmental concerns that have not been
examined.
Consider Emerging Electricity Generation
Technologies
There are several technological options
that could be available in the longer term that
would substantially alter the way fossil fuels
are utilized. Two of the most-discussed
options - fuel cells and magnetohydro-
dynamics -- are discussed below.
Fuel Cells
Fuel cell technology is now in use in
the U.S. space program and is expected to
eventually be commercially available to the
electric power industry. The technology
converts fuel energy to electricity using an
electrochemical process similar to that
employed in chemical batteries.
Total fuel cell plants may achieve
efficiencies of up to 85%. There are several
drawbacks to the technology at this time,
especially: (1) special fuel requirements, and
(2) relatively low reliability.
The fuel cell closest to commerciali-
zation is the Phosphoric Acid Fuel Cell
(PAFC). This fuel cell converts hydrogen
into electricity and water. The hydrogen must
be produced, however; considering the conver-
sion losses, overall powerplant efficiencies for
large fuel cell plants (e.g., several MW)
approach 45%. Second-generation technolo-
gies, such as molten carbonate and solid
polymer electrolyte fuel cells, could offer 60%
efficiencies. In theory, the chemical reaction
could continue as long as fuel is supplied, but
in practice the materials fail after prolonged
operation. The current goal is 40,000
generation hours which, even if achieved, is
still well below that of conventional
powerplants. Another drawback is that the
production of hydrogen from fossil fuels
creates CO2.
The use of hydrogen in fuel cells
suggests the possibility of coupling fuel cells
with renewable energy sources. For example,
solar powerplants could use any power not
delivered to customers to create hydrogen,
which could then be used when solar
powerplants are not operating or when
demand exceeds solar capacity (Ogden and
Williams, 1989). Molten carbonate fuel cells,
under research and development at the U.S.
DOE at this time, could expand the
capabilities of fuel cells to include natural gas
and gasified coals.
Magnetohydrodynamics
Magnetohydrodynamics (MHD) is an
advanced, efficient generation technology that
could use coal as a fuel. In a MHD system,
coal is burned at very high temperatures and
the hot combustion gases are chemically
treated. The gases then pass through a
magnetic field created with superconductors,
thereby generating power. The gases can also
be used in a steam cycle to produce
additional power. The MHD system is
expected to eventually achieve efficiencies of
60%. In comparison, existing conventional
coal powerplants operate at about 31-32%
efficiencies and advanced pressurized fluidized
bed combustion (PFBC) and Integrated
Gasification/Combined Cycle (IGCC) coal
units, now being demonstrated, are expected
to achieve 35-37% efficiency.
There are several drawbacks to the
MHD technology. It is very capital-intensive,
requires superconductors that have only
reached the laboratory stage of development,
and the high temperature combustion could
result in high nitrogen oxide emission rates.
Nonetheless, many observers believe MHD
systems will eventually be available as these
obstacles are overcome, creating an option for
very efficient coal combustion.
BIOMASS OPTIONS
Biomass in one form or another
continues to be the predominant source of
energy for at least half of the world's
population. In many countries, such as
Nepal, Ethiopia, and Guatemala, over 90% of
total energy used comes from biomass
(Goldemberg et al., 1988). Although on a
global basis it accounts for only one-seventh
of all energy consumed, for over 2 billion
V-70
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Chapter V: Technical Options
people it is close to being the only source of
energy.
A number of studies have reported on
the alarming rate of global deforestation as
the current demand for biomass resources far
exceeds the natural rate of regeneration (e.g.,
IUCN, 1980; WRI and IIED, 1988). It is this
difference between growth and use that
contributes to net greenhouse gas emissions.
Despite this current situation, biomass energy
over the long term offers some of the most
promising opportunities for displacing large
amounts of fossil fuel use.
Although biomass fuels account for
about 14% of global primary energy use, they
deliver a much smaller fraction of useful
energy because of the inefficient nature of
their current use. However, technologies exist
or are under development to provide many
times the current level of energy services from
the amount of biomass currently consumed
globally. In addition, it is also technically
possible to greatly increase the annual
increment of biomass available for energy use.
Methods for increasing supply through
agroforestry, biotechnology, etc, and for
reducing extractive use of forest products for
non-energy purposes are discussed in PART
FOUR: FORESTRY. In this section various
approaches are discussed to reduce biofuel
demand through fuel switching, by improving
end-use efficiencies, and by increasing
conversion efficiencies using upgraded fuels
(see Figure 5-6).
Improve Efficiency of Direct Firing Methods
The primary uses of biomass in direct
combustion applications include use in
cookstoves, space heaters, bakeries, brick
kilns, and boilers of various sizes. Typical
conversion efficiencies range from 5-15%.
There is tremendous potential for improving
the end-use efficiency in each of these energy
conversion processes. In fact, this may be the
most cost-effective, immediate option for
decreasing the demand for biomass resources
(e.g., see discussion on technical options for
improving efficiency of biomass use in PART
ONE).
Wood or wood products (bark, sawdust,
chips, bagasse) are already used directly as a
boiler fuel (especially in agroforestry-based
industries with readily-available access to
wood supplies). But there are a number of
modern technologies that can be used to
extract much more useful output. Due to the
physical variability of biomass (and the lower
density of crop residues), some improvements
in combustion properties can very often be
achieved just by properly sizing the solid
biofuels. The energy requirements for sizing
and densification must be weighed against
improved combustion, convenience, and ease
of transport. While this is not absolutely
essential when the application is for heating,
some amount of sizing and/or briquetting is
critical in more efficient boiler or gasifier
designs.
Another area in which combustion
efficiency can be significantly increased is in
the use of advanced burner systems, such as
fluidized bed combustors. These use a stream
of hot air to suspend the fuel and thus
achieve more complete combustion. Some of
these technologies can also use certain fuels
with high ash or silica content, such as rice
husks, that would be harmful to standard
combustion systems.
In a few areas, central power stations
have been constructed specifically to use wood
as a fuel. The facilities that are burning
wood for electrical power range in size from
5 to 50 megawatts. Depending on the cost of
fuel, conventional wood burning is generally
not competitive with conventional fuels due
to lower combustion efficiency and greater
fuel bulk, which necessitates larger fuel-
handling facilities. The localities served by
these plants gain various benefits that may
offset these inefficiencies. For example, local
timber industries may be assisted, and
environmental benefits may be obtained from
reduced CO2 emissions.
Improve Efficiency of Charcoal Production
Charcoal is produced by heating wood
in the absence of air (also known as
pyrolysis). The traditional method of
producing charcoal in kilns made of earth, as
used for centuries in many regions such as
Africa, is very inefficient Only 15-30% of the
energy content of the wood is retained in the
charcoal as all of the gases produced during
V-71
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Strategies for Improving Efficiency of Biomass Use
Mechanical
(chipping,
compacting,
brlquettlng)
Improve conversion
efficiencies
After processing
Thermo-chemlcal
Liquefaction
synfuels
vegetable oil,
methanol
turbines,
electricity, steam
transport
Direct use as solid fuel
(improve efficiencies of stoves
boilers, brick kilns, bakeries)
Pyrolysls
charcoal
fuel
Biological
(fermentation)
aerobic
anaerobic
ethanol
methane
L J
transport
blogas,
stoves,
engines,
lighting
C
•a
p*
5'
Ul
ra
O
o"
(8
-------
Chapter V: Technical Options
pyrolysis are allowed to escape. Substantial
efficiency improvements are possible, for
example, Brazilian kilns built of brick, which
produce charcoal for steel manufacture, have
achieved overall efficiencies of up to 50%,
twice that of traditional methods, by utilizing
the gaseous by-products (Miller et al, 1986).
Even further improvements are expected
(Goldemberg et al., 1987).
Promote Anaerobic Digestion Technology
Anaerobic digestion is a biological
process whereby a combustible gas is
produced in the absence of oxygen; this gas is
a mixture of methane and carbon dioxide
similar to the marsh gas produced in swamps
and landfills. This technology has the
attractive feature of separating the energy
content of biomass from its value as a soil
conditioner and fertilizer. The energy content
is released in a gaseous form (i.e., biogas)
that can be utilized at a higher efficiency than
the original solid biomass. Biogas is primarily
used for cooking and lighting, but can also
partially substitute for diesel in engines used
for irrigation pumping.
China and India have had extensive
biogas programs for more than 15 years
(Moulik, 1985). Both programs have
concentrated on household systems, with
manure and other farm wastes being the most
common feedstocks; over 7 million systems
have been installed, most of these in China.
Programs in both countries have had to deal
with design, construction, and maintenance
problems so that many of the digesters are no
longer functioning (Miller et al., 1986),
demonstrating the difficulty of introducing
even relatively "simple" low-cost technologies
in remote, rural areas of developing countries.
Some larger institutional plants have had a
higher probability of succeeding than
household-size facilities.
Financially, the feasibility of biogas
plants depends largely on whether the biogas
and biomass residues substitute for fuels or
fertilizers that have traditionally been
purchased or obtained at zero financial cost
In cases where the biogas or residues do not
generate incomes or reduce cash outflows,
they are less likely to be economically viable.
However, the nonfinancial benefits of these
programs, such as improvements in public
health due to lower emissions during cooking
or increased mortality of pathogens in the
digester, reduced deforestation, less reliance
on imported fuels, etc., motivate countries
such as China and India to continue subsidies
for biogas projects (Gunnerson and Stuckey,
1986).
There are a number of other
approaches being tried to make this
technology more appealing. Ideally, what is
required is a low capital-investment
technology that permits the use of a wide
variety of feedstocks and results in high gas
yields over a range of ambient temperatures.
In Taiwan, a durable and cheap above-ground
bag digester made from bauxite refining
wastes has been used with success (Miller et
al., 1986). Other promising anaerobic
digester designs being explored include the
upflow sludge blanket and baffled reactor
(Gunnerson and Stuckey, 1986).
Promote Use of Gasification
Many cellulosic materials can be
gasified and then either used directly or
liquified into methanol. There are two routes
for gasifying biomass - one resulting in
producer (or wood) gas and the other in
synthesis gas with higher calorific value.
Producer gas is made by heating wood in an
almost oxygen-free environment so that the
unburned fuel breaks down into gases, ash,
and tar. Producer gas was used to propel
trucks in World War II when oil was scarce.
Synthesis gas is made at higher temperatures
with a purer oxygen source than producer gas,
thus eliminating nitrogen, and lends itself to
conversion into methanol (see Improve
Technologies to Convert Biomass to Liquid
Fuels below).
Producer gas can be made using a
number of raw materials: wood, charcoal, crop
residues, and urban refuse. There are more
than 20 companies world-wide selling
gasifiers, with Brazil and the Philippines
leading in the use of this technology.
Gasifiers have been used to power tractors,
motor boats, and irrigation pumps and to
provide electricity for food processing and
other rural needs. They can also replace oil
as a boiler fuel.
V-73
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Policy Options for Stabilizing Global Climate
Kjellstrom (1985) has shown that for
conventional power generation applications,
biomass gasifiers compete favorably if the
operating times are long, load factors high,
and power outputs large. The economics are
most favorable for wood-based systems rather
than charcoal systems, and could become
substantially more attractive if oil prices were
to increase or biomass input costs were to
decline. One drawback to gasifiers at this
time is that current designs do not accept all
types of crop residues. Kjellstrom also
demonstrated that at 1985 diesel prices it
would be uneconomic to run diesel tractors or
trucks on producer gas or to use it in
industrial applications except for industries
with surplus biomass residues. Another
technical problem is the need to understand
the pollution impacts due to CO emissions
and tar condensates from the biomass
material.
While there are a number of problems
to be resolved before biomass gasifiers can be
easily used to replace natural gas in
conventional applications, research at
Princeton University has shown that
integrated gasifier-combustion turbine systems
could provide, at small scales (e.g., 5-50 MW),
power that is less expensive than power from
new hydroelectric, coal, or nuclear plants.
(See Box 5-5; Larson et al., 1987).
Improve Technologies to Convert Biomass to
Liquid Fuels
Biomass-produced ethanol and
methanol can be used as liquid fuels. In
addition, other biomass-derived oils have been
combined with diesel and used as fuel.
Methanol from Biomass
Methanol from biomass is attractive
because current technologies use raw
materials grown on lands not required for
food production, unlike ethanol from corn or
sugarcane. The state of Hawaii, which must
import all of its oil, has enacted legislation
supporting the construction of a methanol-
from-biomass facility towards the goal of
replacing gasoline and diesel fuel with
methanol (Phillips et al., 1990).
Methanol is produced by first making
synthetic gas (a mixture of CO and H2) by
gasifying (partially oxidizing) biomass, and
then catalytically reacting the product gases.
Though the process for converting synthesis
gas to methanol is fairly well established,
promising research is underway to improve
the conversion efficiency by using novel low-
temperature, low-pressure catalysts (Boutacoff,
1989). However, converting biomass to
clean, usable synthesis gas provides a major
technical and economic challenge. Various
gasification processes are under development,
for example, coal gasification technologies
such as the German Winkler gasifier could be
modified to accept wood as a feedstock
(Williams, 1985). In the U.S., most
evaluations have been based on bench-scale
testing of gasifiers. The next milestone in
commercializing this process calls for scaling
up the gasification and gas-cleaning plants
and operating the facility for extended periods
to confirm gas yields, quality, and operational
integrity (Phillips et al., 1988).
As with most renewable energy projects,
the economics of biomass-to-methanol
processes are less favorable now than they
were in the early 1980s due to lower world oil
prices. Moreover, it is significantly cheaper
currently to derive methanol from natural gas,
and even coal, than from biomass. With
wood costing $34 per dry ton (Phillips et al.,
1988) methanol could be produced at a
wholesale price of S15/GJ. Taking into
account that methanol has a 20% fuel
economy advantage over gasoline, this is
equivalent to a gasoline price of S12/GJ (or
about $1.60/gallon). As a result, the
production of methanol from biomass should
be regarded as a long-term opportunity as
conventional fuel prices rise and/or if
technical improvements reduce costs
(Williams, 1985).
Ethanol from Biomass
Biomass can also be used to produce
ethanol. Ethanol is useful both as an
automotive fuel and as a feedstock for the
production of ethylene and other chemicals.
Because of certain inherent requirements, as
discussed below, its applicability is limited to
V-74
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Chapter V: Technical Options
Box 5-5. Biomass-Fired Combustion Turbines
Adaptation of the integrated-gasifier-combustion-turbine technology discussed
above (combined cycle or aeroderivative turbines -- see FOSSIL-FUEL OPTIONS) to
use biomass presents an attractive option for generating electricity in developing
countries (Larson et al., 1987), and could also become important in industrialized
countries with advances in biomass plantation productivity (see PART FOUR).
Indeed, the use of this technology with biomass should be simpler than with coal
because biomass is easier to gasify and sulfur removal is unnecessary. The use of
aeroderivative turbines (STIG and ISTIG, see Substitute Natural Gas for Coal) may
be particularly attractive because this technology remains quite economic at small
scales. While the individual components of such a system have been tested, a
commercial demonstration of the integrated package could be very important in
increasing investor confidence in this technology.
Biomass-based electricity generation Is most economical where the fuel has
already been collected for other reasons (e.g., the forest products industry, the cane
sugar industry). A prime example is the use of bagasse (i.e., sugarcane residues) at
sugar mills and ethanol distilleries. Although these waste products are currently used
to provide on-site needs for process steam and often electricity, there has been little
interest in increasing efficiency once on-site requirements are satisfied. Indeed, steam
and electricity production is often intentionally inefficient because of the desire to
consume the wastes. Substituting an ISTIG-based cogeneration system for current
steam turbines could increase electrical output by a factor of 20, while still meeting
process steam requirements; total system efficiency could exceed 50% (Larson et a!.,
1987). This could make the cane sugar industry a major electricity producer in
developing countries: if this technology were adopted in the 70 sugar-producing
countries, total capacity could exceed 50 GW, increasing electricity supplies by 25%
in these countries.
Design calculations suggest that the costs would be very competitive with
alternatives. Capital costs could be less than $l,OOQ/kW, and electricity could be
generated for 3-4 cents/kWh where biomass is available for S2/GJ or less (Larson et
al., 1987). (Bagasse in the sugar cane industry is essentially free, implying that the
additional costs for producing electricity could be less than 2 cents/kWh.) The barriers
to adoption of this technology appear to be primarily institutional — collaboration
between the cane sugar or other biomass producers and the utility industry is required.
Furthermore, an integrated biomass-based advanced turbine system needs to be
commercially demonstrated, but it is difficult to attract investors in developing
countries where this technology is most attractive for projects considered to entail
technological risk (see CHAPTER VET).
a few countries. However, to the extent it
can replace petroleum products, net emissions
of CO2 will be zero since ethanol from
biomass is produced on a renewable basis.
Today, Brazil has the most extensive
ethanol development program in the world.
The purpose is to provide alternative trans-
portation fuels, based largely on sugarcane-
derived ethanol (Sathaye et al., 1988).
Although Brazil has succeeded in reducing its
oil imports, its program has received mixed
reviews, largely because the program has
depended on substantial subsidies to ensure
its success. Similar efforts in other countries,
such as Kenya, have been less successful,
usually due to a lack of low-cost biomass or
industrial expertise such as that available in
V-75
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Policy Options for Stabilizing Global Climate
Brazil (Miller et al., 1986). Despite these
problems, alcohol production may offer future
benefits, as a number of other feedstocks
(e.g., grain, sorghum, corn) may provide
cheaper ethanol and as technologies to
produce ethanol from wood are developed
(Brown, 1980).
Currently, the simultaneous saccharifi-
cation and fermentation process (SSF) is
believed to have the greatest promise to
achieve low costs and high yields (Wyman and
Hinman, 1989). The large volume market for
ethanol demands that feedstock and
conversion costs be low. Only the low costs
of lignocellulosic feedstocks provide sufficient
margin to cover conversion costs for efficient
processes. Although the cost of ethanol from
SSF has dropped from S3.60/gallon to
$1.35/gallon over the last eight years,
improvements are still needed in
pretreatment, enzyme production, hydrolysis,
xylose fermentation and recovery steps before
ethanol can compete with conventional fuels
at today's prices ($0.75/gallon at the refinery
gate) (Wyman and Hinman, 1989). This price
reduction can reasonably be expected by the
year 2000 even if research continues at today's
levels (Lynd, 1989).
Biomass Oils as Fuel
One technically-feasible option with
biomass-derived liquid fuels is to use coconut,
palm, and other vegetable oils in combination
with diesel fuel. These oils can be grown on
plantations with high yields, but their worth is
usually greater as food than as fuel. The
Philippines briefly experimented with a
mixture of coconut oil and diesel until
changes in relative prices made the approach
uneconomical (Miller et al., 1986).
SOLAR ENERGY OPTIONS
Solar energy technologies, as described
in this section, are those that collect,
concentrate, and convert solar radiation into
useful energy. Technologies for converting
solar energy into useable energy offer some of
the greatest long-term opportunities for
replacing fossil fuels. Within this category,
however, there are several types of
technologies. Some solar energy applications
for the residential and commercial sectors
were discussed in PART ONE. This section
will focus on solar thermal and solar
photovoltaic options.
Solar thermal systems that are more
sophisticated than the residential and
commercial systems described earlier and that
can concentrate solar radiation to prodace
higher temperatures are being developed.
These higher temperatures could be used to
make steam, electricity, or power for other
industrial process heat applications. The
most sophisticated solar conversion
approaches are photovoltaic technologies that
convert solar radiation directly into electricity.
These techniques have received considerable
research attention over the last 10-15 years
and have progressed considerably as a result.
The potential of both photovoltaic and solar
thermal technologies, which produce power
directly only during daylight hours, will be
even greater as more efficient storage
technologies increase the cost-effectiveness of
storing excess power generated during the
daytime for use at other times, as discussed
further in Enhance Storage Technologies.
Promote Solar Thermal Technology
Solar thermal technology is a promising
area of solar research since it can provide
thermal energy at temperatures from 150-
1700°C for heat or electricity applications, at
almost any scale, and with conversion
efficiencies as high as 31.6% for electricity
and 80% for heat (IEA, 1987). Solar thermal
concentrating systems have been extensively
demonstrated in recent years for both
industrial heat and electricity generation. 670
MW of electricity generating capacity are
already in place or under construction in
seven countries (Shea, 1988). In the U.S.,
solar thermal capacity is projected to increase
to 550 MW in the next 5 years based on
announced industry plans (U.S. DOE, 1987a).
The U.S. Department of Energy has estimated
recently that a further cost reduction by a
factor of 1.5 to 2 would make these
technologies competitive with conventional
electricity generating technologies. U.S. DOE
has also identified several key technical
improvements currently being researched that
could achieve the needed cost improvements,
leading to economic competitiveness by the
mid-1990s (U.S. DOE, 1987a). In recent
V-76
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Chapter V: Technical Options
years most research and development has
focused on three thermal technologies --
parabolic troughs, parabolic dishes, and
central receivers.
Parabolic Troughs
Parabolic troughs are often referred to
as line focus systems because they use one
axis only to track the sun; each concentrator
(collector) has its own receiver, with parabolic
troughs often connected to form a series of
collectors (see Figure 5-7). Troughs operate
at lower temperatures than most other
technologies, for example, up to 400°C,
making them most suitable for industrial
process heat applications. The thermal
efficiencies of these units have improved
significantly in recent years, reaching 65-70%,
with availabilities exceeding 95% (IEA, 1987).
Parabolic Dishes
Parabolic dishes differ from troughs in
that they are point focus systems, in other
words, a two-axis tracking system is employed
to follow the sun (see Figure 5-7). The
higher concentration ratios allowed by this
design (from one hundred to several thousand
suns) produces temperatures approaching
1700°C, making electricity conversion possible.
This technology currently holds many
efficiency records, including the highest
conversion efficiency (31.6%). Several of the
most ambitious development projects are in
the U.S., with installed capacity at some
projects approaching 5 MW. DOE estimates
total system cost at $3,400/kW, although cost
reductions of 40% are considered feasible
(IEA, 1987).
Central Receivers
Central receivers represent the largest-
scale thermal technology. The receiver is
typically mounted on a tower surrounded by
a large field of nearly flat tracking mirrors
called heliostats (see Figure 5-7). The
heliostats focus the solar energy on the
receiver, achieving working fluid temperatures
of 1500°C or higher (IEA, 1987). Several
countries are studying central receivers. The
largest plant, located in southern California
(10 MW), has exceeded peak design output by
20%, operated at night from storage, and
achieved an overall plant efficiency of 13%
(IEA, 1987). Heliostats account for 40-50%
of total costs, and consequently are the focus
of most cost reduction efforts; recent
developments indicate that cost reductions of
50% could be achieved in one or two years
(IEA, 1987).
Solar Ponds
Solar ponds collect and store heat in
large bodies of water and operate at much
lower temperatures than other solar thermal
technologies (85-100°C). In a typical design,
a salt gradient below the surface acts as an
insulating barrier by trapping incoming solar
radiation. Large heat exchangers are used to
extract the thermal energy, which can be used
for many purposes, including seasonal heat
storage for space heating, low temperature
process heat applications, or even electricity
production. Research into this technology
has achieved thermal efficiencies of 15%, with
electrical conversion efficiencies of about 1-
2% (IEA, 1987). Despite these low
efficiencies, solar ponds can be attractive since
capital costs are very low.
Improve Solar Photovoltaic Technology
Solar photovoltaic (PV) technologies
convert solar radiation to electricity (DC, or
direct current) without moving parts or
thermal energy sources. Photovoltaic
technology was initially developed in the
1950s; these first systems were about 100
times more expensive than conventional
generation technologies, but major
improvements have reduced this differential to
3-4 times current energy costs. This
differential is even lower when compared to
current replacement costs. Figure 5-8 shows
the dramatic progress that has been made
since 1975 in reducing the costs of electricity
from photovoltaic systems.
The principal drawback with
photovoltaic technology is the high capital
costs. The current goal is to reduce costs to
about 6 cents/kwh (which is comparable to
the best conventional powerplant costs), at
least for conditions in the southwestern
United States where insolation is high. The
U.S. DOE is projecting that its cost goal
($0.06/kwh) may be achieved in the 1990s and
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Policy Options for Stabilizing Global Climate
FIGURE 5-7
BASIC SOLAR THERMAL TECHNOLOGIES
Parabolic Trough
Concentrator
Parabolic Dish
Central Receiver
Receiver \ Coneeninlof
Receiver
Source: IEA, 1987.
V-78
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Chapter V: Technical Options
FIGURE 5-8
$15-1
3
"o
Q
CM
00
O)
PHOTOVOLTAIC ELECTRICITY COSTS
Small Stand-Alone
Applications
1st Large (60kW)
Experiment
Intermediate (20-200KW)
DOE
Present Status Research Goal:
Austin Electric m- 6C/kWh
1975
1986
1990
Source: U.S. DOE, 1tS7«
V-79
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Policy Options for Stabilizing Global Climate
that photovoltaic systems could provide up to
1.5 GW of generation capacity by 2005 (U.S.
DOE, 1987a). Researchers at Princeton
University are also projecting major
technological breakthroughs in amorphous
silicon solar cell technology. They have
projected that capital costs (almost the entire
cost for PV) for these cells may decline by
over 80% by the year 2000, while the
conversion efficiency of photovoltaic arrays
roughly doubles (Ogden and Williams, 1988).
This could greatly expand the contribution of
photovoltaic electricity generation over the
next several decades.
The basic principle behind solar
photovoltaic power is that as light enters the
PV cell, electrons are freed from the semi-
conductor materials, thereby generating an
electric current. To generate substantial
amounts of power with PV, individual cells
(which produce about 1 watt of direct current
electric power) are combined into a
weatherproof-unit called a module. Modules
can then be connected together into an array,
with the power output limited only by the
amount of area available. The modular
nature of PV arrays allows them to be built
in increments to conform more closely to
power requirements as demand for electricity
grows.
The principal photovoltaic technologies
for current commercial power applications use
silicon for the semi-conductor materials.
Several efforts are underway to improve
silicon-based photovoltaic cells, including
optical tracking that orients the cell toward
the sun, concentrating devices that increase
the amount of solar energy hitting the plate,
layering materials to absorb more of the
energy, and amorphous thin film techniques
that can lower production costs.
Crystalline Cells
Crystalline silicon cells are the earliest
and most-established PV technologies. The
most popular material has been single-crystal
silicon, which had 90% of the global market
in 1980 but only 44% (10.8 MW) by 1985
(DBA, 1987). Single-crystal silicon PV cells
are relatively efficient (production efficiencies
are 12-14%; laboratory efficiencies up to
21%), but have lost market share primarily
due to the high cost of manufacturing. This
involves several energy-intensive stages to
produce the large silicon crystal ingots from
which wafers are cut (which destroys about
half the crystal ingot), then final preparation
and assembly.
In response to some of the problems
encountered with single-crystal technology,
other crystalline technologies have been
developed. Polycrystalline silicon cells use a
casting process that is less expensive but only
slightly less efficient than single-crystal silicon,
for example, commercially-produced cells have
a conversion efficiency of 11-12%, with
laboratory efficiencies of 18% (IEA, 1987).
Polycrystalline silicon cells captured about
20% of the global market in 1985. Another
alternative is polycrystalline silicon ribbon,
which avoids the need to produce slices (or
wafers) by producing sheets or ribbons of
polycrystalline silicon. The advantages of this
technology are the potential for high-speed
production and less material waste, although
its efficiency is somewhat lower, for example,
production efficiencies are 10-13% and
laboratory efficiencies are 17% (IEA, 1987).
This technology has been commercialized only
recently.
Thin-Film Technologies
As an alternative to crystalline
technologies, researchers have focused on thin
films. Thin-film solar cells can be produced
less expensively using less material and
automated production techniques. There are
many semi-conductor thin-film materials
under investigation, including amorphous
silicon, copper indium diselenide, gallium
arsenide, and cadmium telluride.
Amorphous Silicon. Amorphous silicon
cells have received the most attention of the
thin-film technologies, supplying 35% of the
global market in 1985 (EA, 1987). The vast
majority of this was for use in the consumer
market, especially calculators. Because this
material does not possess the natural
photovoltaic properties of crystalline silicon,
efficiency levels have been a problem -
laboratory efficiencies are about 13%.
Additionally, amorphous silicon suffers from
a light-induced power degradation problem
that can cause a 22-30% loss of power output
V-80
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Chapter V: Technical Options
over time. Thus, large-scale projects can
currently expect to achieve about 5%
efficiency over the life of the project.
Research into this problem continues, with
amorphous silicon thin-film cells considered
one of the best potential technologies for
power applications as efficiencies improve and
production costs are lowered.
Other Semiconductor Materials. Other
materials are being investigated that do not
utilize silicon, including copper indium
diselenide, gallium arsenide, and cadmium
telluride. Copper indium diselenide is
attractive due to its high efficiency (up to
12% currently) and stability when exposed to
sunlight over extended periods. Gallium
arsenide technologies have achieved the
highest efficiency of any PV material, 29%
(Poole, 1988), but are also some of the most
costly. Research continues on production
processes, such as electroplating, that would
significantly reduce current production costs.
Multi-Junction Technologies
Multi-junction, or tandem, technologies
combine the characteristics of two or more
different PV technologies to take advantage of
different light absorption characteristics,
thereby increasing total cell efficiency (e.g.,
two-junction devices can achieve efficiencies
of 18-35%; U.S. DOE, 1987b). This
technique has been used to produce the most
efficient solar cell to date - a 31% efficient
cell that combined a single-crystal gallium
arsenide cell and a single-crystal silicon cell
(Poole, 1988). Multi-junction devices can also
be used in solar concentrators, which are
optical systems designed to improve PV
output by increasing the amount of sunlight
striking a cell by 10-1000 times. In
combination these technologies may help to
achieve in practice the 25-30% efficiency
range considered critical for utility
applications (U.S. DOE, 1987b). Multi-
junction thin film technologies are also
expected to become more important as multi-
layering increases efficiency more quickly than
system costs.
ADDITIONAL PRIMARY RENEWABLE
ENERGY OPTIONS
There are opportunities for increased
use of additional renewable energy sources,
such as hydroelectric, wind, geothermal, and
ocean energy. Many of these resources are
utilized today (often to supply electricity) and,
with continued research and development,
have the potential to make important
contributions to meeting future energy needs
without increasing emissions of greenhouse
Expand Hydroelectric Generating Capacity
Hydropower currently provides the
largest share of renewable electricity
generation in the U.S. and globally. In the
U.S., hydroelectric capacity accounted for 10-
14% of total electricity generation for the
years 1983-1987 (US. DOE, 1988a).
Globally, hydroelectric generation accounts for
about 20% of total electricity and 7% of
primary energy production (United Nations,
1988). The technical potential exists to
expand the contribution of hydro at least by
a factor of two by the year 2025.
Industrialized Countries
Traditional large-scale hydropower
projects are no longer a significant option for
most industrialized countries. Many of the
most attractive sites have already been
exploited in these countries and remaining
potential sites are often highly valued in their
natural state for recreational, wilderness, or
ecological purposes. The U.S. has more large
hydroelectric capacity in operation than does
any other country in the world. However,
new sites are no longer being developed, and
the U.S. Bureau of Reclamation, the federal
agency historically responsible for large dam-
building projects in the West, announced in
1987 that its mandate to develop new water
supplies has virtually expired and that it
would be contracting in size and shifting its
focus to other activities over the next decade
(Shabecoff, 1987).
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Policy Options for Stabilizing Global Climate
Among industrialized countries, Canada
has the potential to greatly expand its
hydroelectric generating capacity. The U.S.
Department of Energy recently identified
potential hydro sites in Canada which, if
developed, could more than double peak
hydro-generating capacity in Canada (from
about 55 GW to over 127 GW). This level of
expansion would not be required to meet
projected Canadian demand for many years.
However, excess capacity developed in Canada
could be used to generate power for
transmission to the U.S. where it could
compete favorably with other generation
options in many regions. The DOE analysis
estimates that U.S. imports of power from
Canada could more than doubled by 2010 if
the potential hydro sites discussed above were
developed (U.S. DOE, 1987c). In lieu of this
hydro development, additional generating
capacity in the U.S. during this period would
predominantly be fossil-fueled. Thus,
displacing U.S. capacity additions with
Canadian hydro development would reduce
CO2 emissions. However, any hydro
development raises potential bilateral and
environmental issues with Canada that would
need to be resolved.
Expansion of small-scale hydropower
(e.g., less than 30 MW) could be an option in
many industrialized countries. In the U.S. up
to 10 GW of potential capacity additions in
this category have been identified (U.S. DOE,
1987a). Other OECD countries, such as
Canada and West Germany, are evaluating the
potential for expanding small-scale
hydroelectric generation (Shea, 1988).
USSR and Eastern Europe
In the USSR and Eastern Europe,
there appears to be significant technical
potential for expanding both large- and small-
scale hydro use. In 1981, hydroelectric
generation provided about 13% of total
electricity in the USSR. Soviet researchers
estimated that this was only about 19% of the
country's potential large hydro capacity.
Much of the untapped potential is in Siberia,
requiring potentially costly long distance
transmission to reach major load centers
(Hewitt, 1984). In Eastern Europe there are
indications that opportunities for large hydro
projects still exist as well. Between 1980 and
1985 Romania increased its hydroelectric
capacity by 2.5 GW, which was more than a
70% increase in total capacity (World Bank,
1984).
Opportunities also exist for expanding
small-scale hydro in the USSR and Eastern
Europe. Poland, for example, has recently
initiated a program to rehabilitate 640 small
dams that had fallen into disrepair and return
them to electric generation (Shea, 1988).
Developing Countries
In developing countries the potential
for large-scale and small-scale hydro
development is very large. For example, by
1980 it is estimated that North America and
Europe had developed 59% and 36% of their
large hydropower potential, while in contrast,
Asia, Africa, and Latin America were
estimated to have developed only 5-9% of
potential resources. In fact, most large-scale
hydro development in the 1980s has taken
place in the developing countries.
Between 1980 and 1985, hydro capacity
additions in 12 developing countries totaled
over 38 GW (over 8% of total generating
capacity in developing countries). Several
developing countries, notably Brazil, China,
and India, have ambitious large hydro
development programs planned for the future.
Total capacity additions in developing
countries could exceed 200 GW by 1995 if
these plans are implemented (World Bank,
1984).
There is some question, however, if
these plans will be fully implemented. A
recent study by the U.S. Agency . for
International Development (U.S. AID, 1988b)
points out that many developing countries are
finding it increasingly difficult to finance
capital-intensive power projects, especially
hydro, which have construction periods of 10
years or more. In addition, the AID and
others have pointed out that concerns about
ecological and land-use impacts such as
submergence of forested areas as well as
resettlement impacts of large hydroelectric
projects may slow such development in the
future.
V-82
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Chapter V: Technical Options
As in industrialized countries, there is
also significant potential for small-scale hydro
potential in developing countries. At least 28
developing countries already have active
programs for developing small-scale
hydropower (World Bank, 1984). Equipment
for small-scale hydro generation is now
manufactured in a number of developing
countries, resulting in designs that are both
less costly and more suitable to local
conditions (U.S. AID, 1988a).
Reduce Cost of Wind Energy
Wind-powered turbines were first
connected to electric power systems in 1941.
Currently, there are several technologies
available, primarily horizontal axis wind
turbines and vertical axis wind turbines.
Under optimal conditions, these systems can
produce power at 10 to 15 cents per kilowatt-
hour, or about two to three times more
expensively than conventional fossil-fueled
powerplants. The goal is to reduce these
costs such that in areas with wind resources,
these systems can be used economically. In
particular, wind energy systems may be very
suitable for remote sites where the cost of
conventional generation technologies may also
be quite high.
Considerable improvement in the
performance and economics of wind electric
generation was achieved in the early 1980s.
In California, electricity generated from "wind
farms" increased from 10 terajoule-hours to
16 petajoule-hours (primary energy
equivalent), while capital costs fell from
$3,100 to $l,250/kW between 1981 and 1987
(Shea, 1988). The Department of Energy
reports that the cost of electricity from wind
turbines has fallen from about 30 cents/kWh
to 10-15 cents/kWh in the 1980s. DOE
projects that this improvement will continue
and that wind energy could provide as much
as 0.7 EJ of electricity in the U.S. by 2005
(U.S. DOE, 1987a).
Considerable international attention is
now being paid to wind energy. Wind farms
are being installed in Denmark, the
Netherlands, Great Britain, Greece, and Spain
(IEA, 1987). Other nations that have
announced plans for expanded wind energy
development include China, Australia,
Belgium, Israel, Italy, the Soviet Union, and
West Germany (Shea, 1988).
Exploit Geothennal Energy Potential
Geothermal energy is thermal energy
stored in rocks and fluids within the earth. It
has been estimated that approximately 10% of
the world's land mass contains accessible
geothermal resources that could theoretically
provide hundreds of thousands of megawatts
of energy for many decades (IEA, 1987). As
indicated in Table 5-10, geothermal resources
suitable for generating electricity are extensive
and geographically widespread. From a global
wanning context, several countries with the
most extensive geothermal potential, for
example, the U.S., China, and the USSR, are
also currently heavily dependent on coal
consumption. Geothermal energy may, in
these countries, provide one option for
displacing coal as a source of baseload
electricity generation and industrial heat.
Significant geothermal resources also exist,
and are being developed, in several Pacific
Rim countries, where economic growth rates,
and thus demand for additional energy, is
expected to be high.
While certain types of geothermal
resources, specifically hydrothermal and
geopressured reservoirs, are not strictly
renewable on a human time scale, resources
are so extensive that with careful phasing and
reservoir management, geothermal energy can
make a significant long-term contribution to
global energy needs. Unlike renewable energy
sources such as solar radiation and wind,
geothermal resources are available on a
constant basis, making them suitable for
baseload electricity generation and industrial
applications without the storage problems
associated with intermittent energy sources.
There are several types of geothermal
resources that require somewhat different
approaches for exploitation. Hydrothermal
resources contain hot water and/or steam
trapped in fractured or porous rock at
accessible depths (e.g., 100-4500 meters).
These are the most commonly used resources
currently, and the only resources currently
commercially exploited. Technology for
exploiting these resources involves sinking
wells, extracting the hot fluids, and using the
V-83
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Policy Options for Stabilizing Global Climate
TABLE 5-10
Estimates of Worldwide Geothermal
Electric Power Capacity Potential
(in Megawatts)
Country
Argentina
Bolivia
Cameroon
Canada
Chile
China
Columbia
Costa Rica
Ecuador
El Salvador
Ethiopia
Greece
Guadeloupe
Honduras
Iceland
India
Indonesia
Iran
Italy
Japan
MW
19,950
63,100
15,150
446,700
30,200
537,050
77,650
12,600
100,000
5,000
154,900
8,900
387
12,600
22,900
15,200
436,500
75,850
33,900
79,450
Country
Kenya
Korea (N. & S.)
Mexico
Morocco
New Guinea
New Zealand
Nicaragua
Peru
Philippines
Portugal
Saudi Arabia
Soviet Union
Spain
Taiwan
Tanzania
Turkey
U.S.
Venezuela
Vietnam
MW
79,450
79,450
257,050
19,950
30,900
30,900
33,900
302,000
67,600
1,000
15,850
239,900
5,900
8,150
6,200
87,100
501,200
39,800
37,150
Source: U.S. DOE, 1985c.
V-84
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Chapter V: Technical Options
steam or hot water for electricity generation
or direct heat applications. Steam can be
used directly in steam electric generating
turbines. Hot water resources are either
"flashed" to produce steam, or used to
vaporize another working fluid which in turn
drives a turbine.
Another type of geothermal resource of
long-term interest is hot dry rock. These
potential resources are widely distributed
around the world, but more difficult to exploit
than hydrothermal resources. To extract heat
from hot dry rock, it is necessary to inject
liquid into one well and withdraw it through
another well after it has absorbed heat.
Considerable research is underway to improve
technologies for extraction of energy from hot
dry rock. A geothermal resource still at the
conceptual stage of development is
magma, which is liquefied or partially-
liquefied rock. Potential resources may be
greater than any other geothermal resource
and the very high temperatures available
suggest that power could be economically
produced; however, development of the
necessary technologies is seen as a major
challenge.
Geothermal energy is currently used in
several countries for direct heat and electricity
generation. Table 5-11 shows the extent of
direct heat use in 1984. Table 5-12 indicates
the installed capacity for geothermal
electricity generation by country in 1985.
Although they represent only a small fraction
of total energy use, these facilities have
demonstrated the commercial viability of
geothermal technologies. In the U.S.
geothermal systems currently produce
electricity at a cost that is competitive with
coal and nuclear plants, and the average
geothermal unit today is available on-line
more than 95% of the time (U.S. DOE,
1987a). The Department of Energy projects
that U.S. geothermal electric capacity will
more than double by 1995 to about 4.7 GW.
Geothermal energy may also play an
even more important role in some developing
countries. Eight developing countries
currently have installed geothermal electric
capacity, and about 50 more have been
identified as having potential for geothermal
development (U.S. AID, 1988a). In the
1980s, the costs of geothermal technology
have come down considerably, and small-scale,
ready-to-install generators (1-1.5 MW) have
also been developed and proven reliable.
These and other developments should make
geothermal electricity more attractive to many
developing countries (U.S. AID, 1988a).
Research Potential for Ocean Energy
There are several types of potential
ocean energy sources, including thermal
gradients and waves. Research is underway in
many countries, including the U.S., to develop
technologies that can exploit these resources.
In one technology, cold water located deep in
the ocean is used to condense a working gas
such as freon or ammonia. The liquid then is
reconverted to gas by warm surface waters
and used to drive a turbine and generate
electricity. Current costs for such a system
are roughly three times higher than
commercial alternatives, and there remain
significant technological uncertainties
regarding system components and operation
in an ocean environment.
NUCLEAR POWER OPTIONS
This section discusses the potential role
for nuclear power to meet future energy
needs. From the perspective of global
wanning, nuclear power technologies are
attractive in that they emit only negligible
amounts of carbon dioxide and methane
(Wahlen et al, 1989). As will be discussed,
however, there are serious problems that
beset the nuclear power industry. Fission
technologies are currently used to operate
nuclear powerplants. One of the key
attributes of this technology is its need for
fissionable, radioactive material in order to
operate. Fusion technology is a longer-term
nuclear option currently in the research and
development stage. Unlike fission
technologies, fusion technologies would not
require large inventories of radioactive
materials such as uranium and plutonium.
Enhance Safety and Cost Effectiveness of
Nuclear Fission Technology
Nuclear fission technology is an
important source of electricity in many
regions of the world. For example, nuclear
V-85
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Policy Options for Stabilizing Global Climate
TABLE 5-11
Capacity of Direct Use Geothermal Plants
In Operation • 1984
(For countries having capacity above 100 MW)
Power Energy Load
Country MW GWh %
China 393 1945 56
France 300 788 30
Hungary 1001 2615 30
Iceland 889 5517 71
Italy 288 1365 54
Japan 2686 6805 29
New Zealand 215 1484 79
Romania 251 987 45
Soviet Union 402 1056 30
Turkey 166 423 29
United States 339 390 13
Other 142 582 47
Total 7072 23957 39*
* Based on total thermal power and energy.
Source: IEA, 1987.
V-86
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Chapter V: Technical Options
TABLE 5-12
Geothermal Powerplants On-Line as of 1985
Country
No. Units
Type(s)a
MW
United States
Philippines
Mexico
Italy
Japan
New Zealand
El Salvador
Kenya
Iceland
Nicaragua
Indonesia
Turkey
China
Soviet Union
France (Guadeloupe)
Portugal (Azores)
Greece (Milos)
56
21
16
43
9
10
3
3
5
1
3
2
12
1
1
1
1
DS,1F,2F,B
IF
1F,2F
DS.1F
DS,1F,2F
2F
1F,2F
IF
1F,2F
IF
DS.1F
IF
1F,1F,B
F
2F
IF
IF
2022.11
894.0
645.0b
519.2b
215.1
167.2
95.0
45.0
39.0
35.0
32.25
20.6
14.32b-
11.0
4.2
3.0
2.0b
Totals
188
4763.98
a DS = dry steam; 1F.2F = 1- and 2-flash steam; B = binary.
b Includes plants under construction and scheduled for completion in 1985.
Source: IEA, 1987.
V-87
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Policy Options for Stabilizing Global Climate
plants provided almost 20% of total electricity
generated in the U.S. in 1988. This total is
projected to increase throughout the
remainder of this century as about 16 GW of
new nuclear powerplants, which are currently
under construction, are completed. The
prospects for further capacity additions,
however, are clouded. According to the U.S.
Department of Energy, "No additional orders
for nuclear powerplants are likely in this
country until the conditions of the past few
years are changed" (U.S. DOE, 1987a).
Moreover, between 2000 and 2015, about 40%
of existing nuclear powerplant capacity will
have to be retired unless current operating
licenses are extended beyond their expiration
dates.
The situation is somewhat similar in
many other industrialized countries. The
International Energy Agency (IEA) reports
that nuclear energy was the fastest growing
fuel for electricity generation in the OECD
countries between 1985 and 1987, although,
"It should be kept in mind, however, that
present additions to nuclear capacity come
from stations authorized in the second
relatively intense "cycle" of nuclear plant
construction activity in the 1970s. Compared
with some 239 GW of nuclear capacity
operating in the OECD countries at the end
of 1987, around 52 GW are under
construction" (IEA, 1988). In addition,
planned nuclear electricity production in the
1980s in the USSR has been consistently
behind schedule due to construction delays.
By 1988, nuclear generation was providing
only 13% of electricity in the USSR. In the
wake of the Chernobyl disaster of April 1986,
the Armenian earthquake of December 1988,
and unprecedented public protest of nuclear
power, the nuclear program in the USSR has
experienced numerous reactor cancellations.
Further delays in the nuclear power program
are likely and future contributions are thus
difficult to project (Sagers, 1989).
Nuclear power has been beset by a
series of problems. Plant capital costs have
increased so dramatically that new nuclear
powerplants are no longer considered
economical (see Figure 5-9). The real non-
fuel operating costs of nuclear powerplants
have also escalated rapidly (U.S. DOE,
1988b). Powerplant lead times (i.e., the time
from project initiation to completion) are
greater than ten years, increasing project risk.
Additionally, in many countries such as the
U.S., the regulatory environment is generally
unfavorable toward large, long-term capital
investments and nuclear powerplants in
particular (U.S. DOE, 1987a).
Public opposition to new nuclear
powerplants is strong, in part due to concerns
about safety in the aftermath of the accidents
at Three Mile Island and Chernobyl. In
addition to plant safety, radioactive waste
disposal is an issue of major concern.
Although several countries utilizing nuclear
power are working on the problem, none have
identified an acceptable solution to the
problems of long-term nuclear waste disposal.
Finally, the nuclear weapons
proliferation issue must be resolved if nuclear
power is to become publicly acceptable. A
present-day 1000 MW nuclear plant produces
some 141 kg of fissionable plutonium annually
in its spent fuel. For comparison, it takes
less than 10 kg of fissionable plutonium to
make a nuclear weapon. Currently, this
spent, intensely-radioactive fuel is stored at
plant sites. If nuclear power were to be
greatly expanded in the future, limited
supplies of uranium worldwide would rapidly
force a shift from today's "once through"
nuclear cycles (i.e., the nuclear fuel is only
used once) in the U.S. and Canada to fuel
cycles involving the reprocessing of spent fuel
and the recycling of recovered plutonium for
use as fuel in present reactor types, as is
commonly practiced in Europe and Japan, and
a new generation of plutonium breeder
reactors. The amount of fissionable material
required would pose a formidable institutional
challenge to the world community to
safeguard relatively large quantities of
plutonium that would circulate in worldwide
commerce (Albright and Feiveson, 1987;
Ogden and Williams, 1989).
In the U.S., the Department of Energy
has recognized many of these potential
obstacles. In its 1987 Energy Security report
(U.S. DOE, 1987a), the U.S. DOE identified
three basic obstacles that must be overcome
before new orders will be forthcoming:
V-88
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Chapter V: Technical Options
FIGURE 5-9
CAPITAL COSTS FOR NUCLEAR POWER
18
16
14
a 12
o
U
o
at 10
(Avcrag* $/kw
rcftoet
•t-»p»nt dollart)
14.4
($2693/kw)
13.1
($1644/kw)
8.7
($S64/kw)
9.8
($670/kw)
6.8
($388/kw)
1971-74 1976-76 1977-80 1981-84
Y«ar of Commercial Operation
1986
Source: U.8. DOE, 1»87a.
-------
Policy Options for Stabilizing Global Climate
• Given current reactor designs and
regulatory processes, nuclear power is not
economically competitive with alternative
generation options.
• Public concerns about reactor
safety make licensing of new plants difficult.
• Currently unresolved questions
about the viability of long-term radioactive
waste disposal options have become a
significant barrier to expansion of nuclear
power.
The U.S. DOE has initiated efforts to
deal with all of these problems. First, it has
underway a research program aimed at the
development of improved reactor designs.
Program goals include new designs for
"enhanced safety, increased simplicity, and
improved reliability." To meet these goals,
the new designs incorporate innovative
concepts of passive safety that hopefully would
ensure that any equipment or operator failure
would cause the plant to shut down
automatically. A second important attribute
of the advanced designs is standardization of
designs, which could reduce cost, shorten the
permitting process, and improve reliability and
safety. Third, the new designs are for smaller,
modular units, which should make them more
compatible with the utility industry's needs for
smaller capacity addition. Another design
concept is that the portion of the plant that
is actually within the nuclear containment
vessel can be minimized and modularized,
thereby allowing the balance of the plant to
be built according to standard construction
specifications. An example of this approach
is Sweden's ASEA-ATOM's PIUS reactor,
which places the steam generator and primary
pumps outside the containment vessel (U.S.
DOE, 1988a). More stringent safety
standards for nuclear powerplants could
then focus on the smaller nuclear component.
Ultimately, the nuclear portion may be
designed to be fabricated at the manufacturing
plant and transported in its entirety to the
powerplant site for insertion into the
remainder of the plant (Griffith, 1988).
These principles are being applied to
several basic reactor types, such as:
• Advanced Light Water Reactor
(ALWR). Light water reactor technology is
currently the type most widely in use in the
U.S. The hope is to develop a standardized
design incorporating the lessons of recent
experience.
• Modular High Temperature Gas
Reactor (HTGR). This is an advanced
concept that has not been demonstrated yet
but is being designed to provide a next-
generation nuclear capability that goes further
toward meeting the design criteria mentioned
above than the ALWR.
• Advanced Liquid Metal Reactor
(LMR). For the longer term, designs are
being developed that would incorporate the
design goals stated above into a potential
breeder reactor option.
Finally, on the radioactive waste
disposal issue, DOE is evaluating the
suitability of Yucca Mountain, Nevada, as a
site for long-term deep geologic disposal of
high-level wastes, while also favoring the
construction of a Monitored Retrievable
Storage (MRS) facility for spent reactor fuel
(Blowers et al., 1990). Thus, DOE is
attempting to address many of the constraints
affecting the nuclear power industry. It is
difficult to predict at this point how effective
these programs will be. In addition, the
DOE's Energy Security report does not
mention the weapons proliferation problem
that is also perceived as a long-term
constraint by many observers.
Promote Research and Development, of
Nuclear Fusion Technology
Nuclear fusion, like nuclear fission, is
an attractive power generation technology
from a global wanning perspective because it
does not generate significant greenhouse gas
emissions. Fusion power has two key advan-
tages over fission power: (1) It uses secure
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and inexhaustible fuels, in that lithium and
deuterium are obtainable from seawater, and
(2) it does not create large inventories of
radioactive wastes.
Fusion reactor technology, however, is
only in the early stages of research and
development; it is not expected to be a viable
technology before 2025. The costs of
development for this technology are expected
to be high. To hasten fusion development
and to defray the costs that need to be borne
by any single country, additional international
cooperative agreements concerning research
and development of this technology are likely
to be signed in the next few years.
ELECTRICAL SYSTEM OPERATION
One possible option for reducing the
amount of greenhouse gas emissions from
electricity is to improve the efficiency of
transmission, distribution, and storage of
electrical power.
Reduce Energy Losses During Transmission
and Distribution
Electrical energy losses from
transmission and distribution are normally in
the 5-10% range in industrialized countries.
When generation is primarily from fossil fuels,
as in the U.S., programs to reduce efficiency
losses associated with electricity transmission
and distribution may provide one option for
modest reductions in greenhouse gas
emissions. In developing countries, however,
it is very likely that significant improvements
are technically possible. Many developing
countries experience losses of over 20%, even
30%. Relatively inexpensive and
straightforward technological solutions exist
for upgrading utility transmission and
distribution systems to recover a major
portion of these losses. On the other hand,
in many countries it is estimated that half of
the "controllable" losses are due to theft (U.S.
AID, 1988b); despite many reasons for
reducing these thefts, it is not clear whether
a straightforward solution to these electricity
thefts exists nor would this mean a significant
reduction in greenhouse gas emissions, except
to the extent demand is reduced as consumers
are charged for the power they use.
Electric utility companies normally
operate their systems and interconnections
with other systems in such a way as to
minimize generation costs, subject to a
number of other constraints. Thus,
powerplants with the lowest variable operating
(including fuel) costs would be operated more
of the time, and power available from other
utility systems would be purchased when its
cost is lower than the incremental cost of
generating additional power within the system.
Within this framework, there may be
some flexibility to shift more of the overall
load to non-fossil or natural-gas-fired capacity
without greatly increasing overall generating
costs. Although difficult to achieve
institutionally, such alternative dispatching
options may be technically feasible and cost-
effective in the near term. This could include
"wheeling" power from region to region to
take maximum advantage of non-fossil
generating capacity. On its largest scale,
this type of strategy could result in
international electricity transfers from
countries with less carbon-intensive generating
capacity to countries with more carbon-
intensive available options. For example,
expanded Canadian power imports to the U.S.
based on hydroelectric generation would be
one such possibility.
Superconductors offer no resistance to
electrical flow. Recently, breakthroughs in
superconductivity research have increased the
prospects that this technology could be
applied to power production. Until recently,
superconductivity could only be achieved in
extremely cold environments (e.g., more than
200°C below zero). The superconductivity
effect can now be achieved at much higher
temperatures, although they are still well
below ambient conditions. In the long term,
superconductivity could significantly improve
the transmission of power. Conventional
transmission systems lose about 8% of the
power they conduct; superconductors could
greatly reduce, if not eliminate, these losses.
Superconductivity could also be beneficial for
power production. For example, several
technologies use electromagnets, including the
MHD system discussed above. During the
power production process, electromagnets are
typically the source of some lost power.
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Superconductors could reduce the energy lost
in generating power by reducing the losses
associated with electromagnets. Also, as
discussed below, superconductivity could be
useful for energy storage.
Enhance Storage Technologies
There are a variety of technologies
currently available or under development for
energy storage. Storage systems can perform
several tasks, including the following:
• Load Leveling, which would allow
inexpensive baseload electricity to be stored
during periods of low demand and released
during periods in which the marginal cost of
electricity is high (e.g., powerplants could be
run during the night and the power stored to
meet peak requirements in the afternoon).
One drawback is that storage may allow
baseload coal to substitute for natural gas,
increasing greenhouse gas emissions, unless
renewable energy sources are used.
• Spinning Reserve, in which the
energy would be used as backup in case of
failed generating systems.
• System Regulation, in other words,
to balance a utility's constantly-shifting
generation and load requirements.
The development of adequate energy
storage systems could be particularly crucial
for the competitiveness of many renewable
energy technologies that can only produce
power when the resource is available, for
example, during daylight hours for solar or
when the wind is blowing for wind energy
systems. To enhance their competitiveness,
renewable technologies could be used in
tandem with storage systems that would allow
power to be generated whenever available and
then stored until needed.
There are many different types of
energy storage systems, including pumped
storage, batteries, thermal, compressed air,
and superconducting magnetic energy storage.
Several major energy storage systems are
discussed below.
Pumped Storage
Pumped storage is a hydroelectric
power storage option that has been used
recently by the electric utility industry to meet
electricity requirements during periods of
peak demand. With this system water is
pumped from a lower storage reservoir to an
upper storage reservoir during off-peak hours,
using electricity from a baseload powerplant
(which is frequently coal-fired or nuclear).
During peak demand hours, the water is
released to the lower reservoir much like it
would be at a typical hydroelectric dam. This
system essentially stores power from the
baseload powerplant when it is not needed for
use during peak demand periods when the
baseload plant is already committed 100% to
meeting the peak power requirements.
While there are numerous pumped
storage plants in the U.S., their efficiency is
low and additional siting is likely to be
difficult if they involve large, above-ground
reservoirs. When underground reservoirs are
used, the systems are only economical in very
large facilities (e.g., 1000 MW).
Batteries
Batteries are attractive primarily for
their flexibility; because they are modular,
plants can be constructed quickly on an as-
needed basis. Recent research and
development has focused on advanced lead-
acid batteries and zinc-chloride batteries.
Lead-acid battery technology has been used
for decades (e.g., in automobiles), although its
use in utility applications may be limited by
its capital costs. Due primarily to the lower
cost of the construction materials, the zinc-
chloride battery is expected to be less
expensive than the lead-acid battery in the
longer term; possibly less than S500/kW
compared to $600/kW or higher for lead-acid
batteries (OTA, 1985). Plans to test both
types of batteries on a commercial scale are
currently being planned. Other battery
technologies that could be available in the
longer term include zinc-bromide, sodium-
sulfur, iron-chromium, and lithium-iron
sulfide batteries.
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Compressed Air Storage
Compressed air energy storage (CAES)
uses off-peak electricity to store energy in the
form of compressed air in an underground
cavern such as salt reservoirs, hard rock
reservoirs, or aquifers. The compressed air is
used in tandem with natural gas or oil in a
modified gas turbine where the compressed
air is used in lieu of a conventional
compressor in the turbine cycle, thereby
allowing the turbine efficiency to increase up
to three times its normal efficiency (OTA,
1985). CAES is dependent on geological
characteristics that can be found in about 3/4
of the U.S. and uses technology that is well-
advanced. However, no CAES facility has yet
been built in the U.S.; there is a facility that
has been operating since 1978 in West
Germany. There are two sizes proposed for
CAES plants; a mini-CAES (about 50 MW)
costing about $392/kW and a maxi-CAES
(about 220 MW) costing about $515/kW;
construction lead times are estimated to be 4
to 8 years (OTA, 1985).
Superconducting Magnetic Energy Storage
Superconducting magnetic energy
storage (SMES) would function like more
conventional storage technologies, but would
be able to store energy with an efficiency of
approximately 95% compared to 75% for
pumped storage or 65% for battery storage
(Schlabach, 1988). At this time SMES is
clearly a long-term technology pending further
improvements in basic superconductivity
design.
HYDROGEN OPTIONS
One concept for reducing CO2
emissions is the long-term phaseout of a
carbon-based economy and the adoption of
one utilizing hydrogen and electricity as
complementary energy currencies. Hydrogen
would serve as an "energy carrier" since
electricity or some other source of power is
required to produce it. Hydrogen is attractive
for this role because it is nonpolluting,
portable, and relatively safe. Hydrogen could
be produced in a number of ways, including
chemical processes beginning with coal or
natural gas, and electrolysis using electricity
from the full range of potential electricity
production options. Of course, production
chemically from fossil fuels or the use of
fossil-based electricity would not provide
significant long-term reductions in greenhouse
gas emissions. However, these technologies
are currently available and could play a role
in a transition to greater use of hydrogen as
an energy source (Harvey, 1988).
One technology under development
holds some promise for allowing hydrogen to
be generated from fossil fuels without CO2
emissions. The process, known as hydrocarb,
produces hydrogen and carbon black through
a process of gasification and distillation.
When coal is used as the feedstock,
approximately 20% of the energy value is
converted into hydrogen. The carbon black
produced could be disposed of in mines or
other disposal facilities. Biomass can be used
as the feedstock, although it is a less efficient
source of hydrogen (Grohse and Steinberg,
1987).
While large-scale hydrogen use would
have to be considered a long-term option, this
fuel could begin to make contributions in the
near term. Researchers at Princeton Univer-
sity have suggested that use of hydrogen as a
transportation fuel in urban areas may be its
first significant role toward replacing
traditional fuels (Ogden and Williams, 1988).
Existing transport fuels are high-priced
(allowing hydrogen to compete more easily),
and urban air quality problems are already
forcing many cities to look for alternatives to
gasoline and diesel fuel in the transportation
sector. Ogden and Williams also suggest that
recent and projected improvements in the
economics of amorphous silicon photovoltaic
cells may make hydrogen fuel production
from solar PV electricity cost competitive in
some areas of the U.S. before the end of this
century.
Another attractive feature of hydrogen
that would be helpful in a long-term
transition away from fossil fuels is that it can
substitute relatively easily for natural gas in
many applications. For example, natural gas
space heating could be replaced by hydrogen
over the long term; natural gas pipelines
could be used to transport hydrogen and
hydrogen is the basic fuel for fuel cells.
Storage of hydrogen could occur in salt mines,
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Policy Options for Stabilizing Global Climate
aquifers, and depleted oil and gas fields for hydrogen accomplished by the electrolysis of
large needs and as liquid hydrogen and metal water.
hydrides for small applications.
Conversion efficiencies in producing
In a long-term hydrogen economy, non- hydrogen from renewable energy exceed 80%
fossil energy could be provided by a variety of and efficiencies for conversion back to energy
renewable sources, with conversion to in fuel cells range from 58-70%.
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Chapter V: Technical Options
PART THREE: INDUSTRY
Figure 5-10 illustrates the overall
current contribution of industrial processes
(excluding energy) to the greenhouse wanning
problem. By far the largest component is the
production and ultimate release to the
atmosphere of chlorofluorocarbons (CFCs),
batons, and chlorocarbons. Other industrial
processes are relatively minor, but growing,
contributors: carbon dioxide (COj) is emitted
from cement manufacture and methane (CH4)
is produced by solid waste landfills. In
addition, industrial process emissions of
carbon monoxide (CO) contribute to
atmospheric chemistry, which indirectly affects
the concentration of tropospheric ozone (O3)
and CH4.
CFCs AND RELATED COMPOUNDS
As a result of the Montreal Protocol
and the June 1990 London Amendments
(discussed in CHAPTER vni), emissions of
the most important CFCs will be capped in
1989, reduced to half of 1986 levels by 1995,
and phased out by 2000. Halons will be
frozen at 1986 levels beginning in 1992 and
phased out in 2000. In addition to the CFC
and halon phaseouts, phaseout schedules for
carbon tetrachloride and methyl chloroform
were set, and a non-binding declaration was
made regarding the phaseout of
hydrochlorofluorocarbon (HCFC) production.
A series of recent detailed reports
prepared under Article 6 of the Protocol by
international experts examined the available
and emerging options for reducing CFCs, as
well as halons, methyl chloroform, and carbon
tetrachloride, which are of potential concern
for both stratospheric O3 depletion and
greenhouse warming (UNEP, 1989). These
reports asserted that technical options are
currently available for virtually eliminating all
CFCs, methyl chloroform (reductions of 90-
95%), carbon tetrachloride, and halons
(minority view stated only 50% reduction
possible).
As a reflection of this technological
progress, many industrial groups (e.g., rigid
foam electronics, auto manufacturers) have
announced goals of eliminating their use of
CFCs in the mid-1990s or sometime before
the end of the century.
Some of the substitute compounds
affect greenhouse warming but to a much
smaller degree than do the controlled
substances. Most of the unregulated
compounds have much shorter atmospheric
lifetimes, which decreases their impact on the
greenhouse problem.
Use and emissions of CFCs could be
reduced by three possible mechanisms:
• Chemical substitution - switching
from production processes in which CFCs are
used to those in which other chemicals are
used; for example, using FC-134a or blends of
other non-fully halogenated HCFCs instead of
CFC-12 in mobile air conditioning.
• Engineering controls - in the near
term, switching to production technologies
that use fewer CFCs (or substitutes) per unit
of output, such as recycling equipment that
collects and recycles CFC emissions during
the production of electronics.
• Product substitution - switching
from CFC-using products to other products;
for example, replacing CFC-based foam egg
cartons with paper-based egg cartons.
This chapter surveys existing and future
product substitutes, engineering controls, and
chemical substitutes that can reduce use and
emissions of CFCs and halons. The
information presented is based on a detailed
series of industry studies performed by the
U.S. Environmental Protection Agency (U.S.
EPA) for use in its Regulatory Impact Analysis
for stratospheric ozone protection and from a
technical assessment performed by the Parties
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FIGURE 5-10
INDUSTRIAL PROCESS CONTRIBUTION
TO GLOBAL WARMING
Energy Use
and Production
(57%)
CFC-12(10%)
CFC-11 (4%)
Other CFCs (3%;
Other
Industrial
(3%)
Agricultural
Practices
(15%)
Land Use
Modification
(8%)
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Chapter V: Technical Options
to the Protocol (U.S. EPA, 1987). Unless
otherwise noted, information in this section is
drawn from U.S. EPA (1988b).
Expand the Use of Chemical Substitutes
Several chemical substitutes that have
physical properties (e.g., boiling point) similar
to those of CFCs either do not contain
chlorine or have short atmospheric lifetimes
that reduce their potential to deplete
stratospheric O3.
FC-134a, HFC-152a and blends
including non-fully halogenated HCFCs
(HCFC-22, HCFC-124, HFC-152a) appear to
be the most promising chemical substitutes
for refrigeration and air conditioning
applications, including commercial chillers and
mobile air conditioning, and along with
HCFC-141b and HCFC-142b appear to be
likely alternatives to CFC-11 and CFC-12 in
production of polystyrene sheet and
polystyrene boardstock. Several major
chemical producers have announced plans to
build commercial-scale production facilities
for FC-134a and HCFC-141b. An
international consortium of chemical
producers has been formed to undertake
toxicity testing of FC-134a and other chemical
substitutes.
HCFC-141b and HCFC-123 are
expected to become commercially available in
the early 1990s and could replace CFC-11
currently being used in manufacturing
slabstock flexible polyurethane foam and rigid
polyurethane foam. In blends with HCFC-22,
HCFC-142b appears to be an option for
replacing the remaining "essential" CFC use in
aerosols.
HCFC-22 is currently used in residential
air conditioners and might be used in
commercial chillers. It could substitute for
CFC-11 and CFC-12 as a leak-testing agent in
several refrigeration applications. Mixtures of
HCFC-22 and other compounds could be used
in mobile air conditioners.
HCFC-22 has already been adopted as
a substitute for CFC-blown polystyrene sheet
products. It was recently approved by the
Food and Drug Administration as an
alternative blowing agent for use in food
packaging. The Foodservice and Packaging
Institute, in concert with several
environmental groups, recently completed
implementation of an industry-wide program
to eliminate within one year the use of CFC-
11 and CFC-12 in food service packaging by
substituting HCFC-22.
A major manufacturer of extruded
polystyrene boardstock recently announced
that it will substitute HCFC-22 and other
partially halogenated CFCs in its
manufacturing processes beginning in 1989.
Blends of HCFC-22 with dimethyl ether
and HCFC-142b can be used to replace the
remaining "essential" CFC use in aerosols.
Hydrocarbons have largely replaced CFCs as
aerosol propellants in the United States.
Other nations can reduce their use of CFCs
in aerosol propellants by reformulating
aerosol products.
Ethytene oxide (EO) is currently
blended with CFC-12 for use in the
sterilization of medical equipment and
instruments. Reductions in CFC-12 use could
be achieved by using pure EO, a blend of
CO^/EO, radiation, or the use of HCFC or
HFC substitutes.
Aqueous cleanings and terpene-based
solvents can be used instead of CFC-113 to
clean electronic components. One major
manufacturer expects to replace one-third of
all its CFC use in electronics manufacturing
with terpene-based solvents. Aqueous
cleaning can also reduce CFC-113 use in
many applications for cleaning electronic
components.
Employ Engineering Controls
Recovery and recycling can reduce CFC
emissions from several applications. Recovery
and recycling during servicing of air
conditioning and refrigeration equipment,
such as commercial chillers and mobile air
conditioning units, can achieve large
reductions in CFC emissions. An industry-
wide voluntary purity standard for recycling
CFC-12 from car air conditioners was recently
adopted. U.S. EPA has recently been
petitioned by an industry trade group to
establish a national recycling program.
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Carbon adsorption units could be
installed to capture CFC emissions during
manufacture of slabstock flexible polyurethane
foam. Simple housekeeping improvements
and process modifications such as automatic
hoists and covers, carbon adsorption,
reclamation, and recycling can substantially
reduce CFC-113 emissions during solvent
cleaning. Furthermore, many electronics firms
are finding that cleaning during the
manufacturing process can be substantially
reduced and in some cases eliminated without
sacrificing product quality or reliability.
Alternative leak-testing agents can
reduce halon emissions during discharge
testing of total flooding fire-extinguishing
systems.
Improved system design can reduce
CFC emissions. Attractive techniques in
mobile air conditioning include design
improvements, such as the use of more
refrigerant-tight hose materials, shorter hoses,
and improved compressor seals and fittings.
Alternative processes can be used to
produce final products without using CFCs.
For example, the CFC-blown flexible foam
process can be modified to eliminate use of
CFC-11, but the foam will be slightly denser
as a result. Nearly all uses of molded flexible
foam could be converted to water-blown
formulations.
Training could reduce unnecessary
discharges of CFCs during air conditioning
servicing. Adoption of new training
procedures, such as use of simulators, could
reduce halon emissions during military
training exercises.
Use Substitutes for CFC-Produced Materials
Research efforts are exploring ways to
replace the use of CFC-blown insulation in
refrigerator walls by insulating vacuum panels.
A prototype vacuum panel refrigerator, which
could achieve sizeable gains in insulating
properties, is currently being built.
CFC-blown slabstock flexible
polyurethane foams can be replaced by other
products. Fiberfill materials, cotton batting,
latex foams, and built-up cushioning that
contains springs may be suitable substitutes,
but they are more expensive and lack the
durability of flexible polyurethane.
Some product substitutes are available
for rigid polyurethane foam products. Many
alternative products are currently available for
use as sheathing or roof insulating materials.
Expanded polystyrene foam headboard,
fiberglass, fiberboard, and gypsum, for
example, could be used instead of
polyurethane foam, as they were 30 years ago
when polyurethane foams were not yet
manufactured. In some cases, wall and
roofing insulation can be made thicker to
achieve the same insulating capacity as at
present, but the use of foam blown with
chemical substances is likely to continue
where it offers the advantages of reduced
labor costs and smaller bulk and meets a
building's energy efficiency requirements.
Some product substitutes are available
for poured or sprayed foam, depending on the
specific use. In applications such as
packaging and flotation, product substitutes
are numerous. Combinations of plastic and
non-plastic materials can provide equivalent
degrees of cushioning, shock resistance, and
water resistance. At present, however, no
other insulation materials have the equivalent
ability to be poured or sprayed, nor can other
materials of the same thickness insulate as
well as rigid polyurethane foams.
Polystyrene sheet competes with many
other disposable packaging and single service
products, including paper, cardboard, solid
plastic, metal foils, and laminar composites of
foil, plastic film and paper. Any of these
substitutes could eliminate CFC use in food
packaging applications.
Current and possible future alternatives
to foam boardstock as insulation include a
host of product substitutes, including
fiberglass board, perlite, expanded polystyrene,
fiberboard, cellular glass, insulating concrete,
rock wool, vermiculite, gypsum, plywood, foil-
faced laminated board, and insulating brick.
Greater thicknesses of these alternatives may
be required to provide equal energy efficiency.
Pre-sterilized, disposable products are
one possible alternative that will enable
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Chapter V: Technical Options
hospitals to reduce their dependence on CFC-
12 for sterilization.
Pump sprays and roll-ons are product
substitutes that can replace CFC-propelled
personal care aerosols.
METHANE EMISSIONS FROM LANDFILLS
Over 1.6 million tons of municipal solid
waste is generated on the planet each day
(adapted from Bingemer and Crutzen, 1987).
Approximately 80% of this volume is disposed
of on land in landfills or open dumps.
Anaerobic decomposition of municipal and
industrial solid wastes in landfills results in
the generation of 30-70 Tg of CH4 each year
(Bingemer and Crutzen, 1987).
The amount of gas produced by a given
site is a function of the amount and
composition of landfilled wastes. The rate of
gas production is a function of the age of
material in the landfill, oxygen and moisture
concentrations, pH, and the presence of
nutrients. Methane production is highest
when the organic content of the refuse is
high, the wastes are relatively new, and there
is adequate moisture available. The
decomposition process only occurs in an
environment that is oxygen-free and has a
moderate pH. There is a one- to two-year lag
period between landfilling of wastes and the
beginning of gas generation. Methane
production occurs once all available oxygen
has been consumed and the environment
becomes anaerobic. Food and garden wastes
generally decompose over a 1- to 5-year time
frame, while paper wastes could require 5 to
20 years to decompose (Bingemer and
Crutzen, 1987). These factors and the active
life of a landfill affect the duration of CH4
production. It can take anywhere from 10
years to over 100 years for a landfill to
produce significant amounts of CH4 (Wilkey
et al., 1982).
Estimates place the rate of CH4
production between 1000 and 7000 cubic feet
per ton (31-218 m3/mt) of municipal solid
waste deposited (Wilkey et al., 1982). The
United States generated approximately 148
million tons of municipal solid waste in 1988
(U.S. EPA, 1988c), which, using the rates
above, would produce between 2.9 and 20.7
teragrams (Tg) of CH4. Using a CH4
production rate suggested by Bingemer and
Crutzen (1987), the same amount of solid
waste would produce an estimated 7 Tg of
CH4.7
Increase Methane Recovery
Landfill gas, which is typically
comprised of approximately 50% methane,
50% carbon dioxide, and some trace
constituents of volatile organic compounds,
can be recovered and used as fuel. The gas is
a medium-British thermal unit (Btu) fuel
(approximately 500 Btu/standard cubic foot),
which can be used directly in boilers or for
space heating, in gas turbines to generate
electricity, or can be processed to high-Btu
pipeline quality gas (Zimmerman et al., 1983).
The gas is purified prior to use: for medium
Btu-gas, processing requires removal of
particulates and water, for high-Btu gas, CO2
and most trace components must also be
removed.
Landfill gas can present an
environmental hazard because of its high
combustibility and ability to migrate through
soil Methane is flammable in concentrations
between 5 and 15% by volume in air at
ordinary temperatures. Methane can rise
vertically or can migrate horizontally out of a
landfill. Methane migrates easily through
porous soils, drainage corridors and other
open areas, often travelling significant
distances. Migrating CH4 gas has caused
explosions and flash fires, resulting in
property damage and death. Malodors and
vegetative damage have also been attributed
to migrating landfill gas.
Methane control systems, required
under certain circumstances by the Resource
Conservation and Recovery Act (RCRA), can
help to mitigate malodors, gas hazards, and
vegetative stress. RCRA requires that
concentrations not exceed a lower explosive
limit of 5% methane (10% landfill gas) at the
landfill boundary. Controls include
impermeable barriers, induced exhaust
systems, evacuating and venting or flaring
(burning) of the gas, and recovery for use as
an energy source. Of these controls, only
flaring and recovery of the gas reduce the
amount of CH4 emitted into the atmosphere.
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Of the 6,584 municipal solid waste
landfills in operation in the U.S., 1,539
(16.6%) employ some methane recovery or
mitigation system such as venting or flaring.
Only 123 of these sites (1.9% of total)
recover methane for energy use (U.S. EPA,
1988c). New regulations proposed by U.S.
EPA under the Clean Air Act would require
collection and control of landfill gas at both
new and existing landfills. These regulations
have the potential to significantly reduce the
emission of CH4 from landfills in the U.S.
(U.S. EPA, 1988a).
Estimates place the quantity of gas
generated by sanitary landfills in the U.S. at
1% of the nation's annual energy needs, or
approximately 5% of current natural gas
utilization (Escor, 1982). The recovery
efficiency of methane from landfills can range
between 60 and 90% of the gas produced,
depending upon the quality and design of the
gas recovery system, spacing of recovery wells,
and landfill covering.
The economic viability of CH4 recovery
at a landfill depends upon the landfill's size,
location, proximity to potential users, current
competing energy costs, and regulations
governing the site. The capital costs of
recovery projects are about $1000/kW.
Suggested minimum requirements for recovery
include an in-place refuse tonnage of 2
million tons, a disposal rate of 150 tons per
day, an average refuse depth of 40 feet (ft), a
surface area of 40 acres, and two years of
remaining active fill life (EMCON Associates
and Gas Recovery Systems, Inc., 1981).
Probably fewer than 1,000 landfills in the U.S.
are of sufficient size to meet these criteria.
Sanitary landfills in developed countries hold
the best potential for economical recovery of
methane. Currently, there is little potential
for CH4 recovery from open dumps in the
developing world; if the practice of sanitary
landfilling is adopted, the prospect of CH4
recovery will improve.
Over 408 (about 5%) of the municipal
solid waste landfills in the U.S. receive more
than 500 tons of municipal solid waste per
day (U.S. EPA, 1988c). Collectively, these
landfills receive over 75 million tons of
municipal solid waste each year (over 50% of
the total generated in the U.S.). If CH4
recovery were implemented only on the
largest 5% of landfills in the U.S., an
estimated 2.2-3.3 Tg of CH4 could be
recovered.
Constraints on the economic feasibility
of recovery projects have hampered further
adoption of this technology. Under current
market conditions, projects are not
economically viable unless there is a suitable
gas user within two to three miles of the site,
or the electricity generation can be tied into
an electricity grid. Current regulations
governing many sites also discourage the
recovery of methane. Some state regulations
subject resource recovery projects to
unlimited liability for any potential
contamination problems at a landfill - a
significant disincentive to recovery.
Various techniques can be used to
enhance gas production and yield from a
landfill, including controlled addition of
moisture and nutrients (usually in the form of
landfill leachate or landfill gas condensate),
bacterial seeding, and pH control. The
addition of leachate and condensate is only
permitted at landfills where there is a liner.
Further research in these areas could increase
the economic viability of CH4 recovery.
Employ Recycling and Resource Recovery
Recycling and resource recovery hold
the potential to affect emissions of
greenhouse gases through both waste
reduction and reducing energy demand.
Source separation and waste-stream reduction
have many benefits for the municipality and
the environment. A reduced waste stream
means less refuse going to the landfill, an
increasingly limited resource. In addition, the
energy savings from recycling can be
significant as discussed in PART ONE.
Separating organics from the waste
stream, such as paper and food, lawn, and
garden wastes, can achieve many benefits,
including reduced production of CH4.
Reducing organics in the landfill results in
less CH4 production from that source.
Organics that are separated and composted do
not produce CH4 if the composting includes
aeration to keep the process aerobic
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Chapter V: Technical Options
Within the industrialized countries of
the OECD, garden and park wastes make up
about 12-18% of the municipal solid waste
stream and account for about 10-14% of its
organic content, while food wastes make up
between 20 and 50% of the stream and
account for over 20% of the organic content.
Within developing countries, garden and park
wastes are insignificant, while food wastes
account for between 40 and 80% of the waste
stream and over 70% of the organic content
(adapted from Bingemer and Crutzen, 1987).
Given these high proportions of food, garden,
and park wastes, the potential for reducing
CH4 production through aerobic composting
could be significant.
Reduce Demand for Cement
Carbon dioxide emissions from cement
production originate from two sources: 1) as
a chemical by-product of the manufacturing
process, and 2) as a by-product of fossil-fuel
combustion used for kiln firing and plant
electricity. Energy consumption emissions are
discussed in the end-use section of this
chapter. The CO2 emissions that result as a
chemical by-product occur during the firing
process, when the raw materials (cement rock,
limestone, clay, and shale) are exposed to
progressively higher temperatures in a kiln.
It is during calcination, which occurs at
approximately 900 to 1000°C, that the
limestone (CaCO3) is converted to lime
(CaO) and CO2, and the CO2 is released.
For every million tons of cement produced,
approximately 0.137 Tg C as CO2 is emitted
as a result of this chemical process (Rotty,
1987). For comparison, approximately 0.165
Tg C per million tons of cement produced
result from energy consumption.
Although cement manufacture currently
accounts for only a small percentage
(approximately 2%, not including the energy
consumption emissions) of the global
anthropogenic source of CO2, emissions
associated with this industry have increased
rapidly over the last few decades and can be
expected to continue to grow in the future as
demand for cement grows. Between 1950 and
1985, cement production and associated CO2
emissions grew at an average annual rate of
6%. Regional production growth rates have
varied during this period due to economic
fluctuation in the construction industry
(cement's primary market) and shifts in
international competition between the
cement-producing countries. Today, the
USSR, China, Japan, and the U.S. account for
43% of the world's cement production.
Since CO2 is an inherent product of
cement manufacture, the only way to slow the
rate of growth in emissions is to limit the
amount of cement required, that is, reduce
demand through more efficient use of cement
and/or through substitution with other
materials (e.g., steel and glass). Increases in
efficiency can be achieved through both
material and fabrication improvements, for
example, through the use of pre-stressed and
steel-reinforced concrete products.
Substitution of cement with other materials
such as steel, glass, or wood also would slow
the growth in cement demand, although
substitution with such energy-intensive
materials as steel may result in greater net
CO2 emissions. In fact, in some applications
cement products have been used in lieu of
other materials, such as steel Improved
efficiency has already occurred in much of the
developed world due to improved engineering
design in construction. Also, most basic
infrastructure has been built in the developed
world, so demand may slow somewhat in the
future. This is not likely to be the case in
the developing world, however, where demand
will probably continue to grow more rapidly
than GNP, particularly since cement is an
inexpensive building material.
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Policy Options for Stabilizing Global Climate
PART FOUR: FORESTRY
Forests, which store 20-100 times more
carbon per unit area than croplands, play a
critical role in the terrestrial carbon cycle
(Houghton et al., 1988b). Active forest
management to maintain high amounts of
standing biomass, to reduce tropical
deforestation, and to aggressively reforest
surplus agricultural or degraded lands, offers
significant potential for slowing atmospheric
buildup of carbon dioxide (CO2), carbon
monoxide (CO), nitrous oxide (N2O), and
methane (CH4). Forestry-related policy
responses to climate change are particularly
important because they (1) are capable of
partially offsetting current fluxes of CO2, (2)
require modest costs relative to non-forestry-
related options, (3) do not require the
development and dissemination of new
technologies, and (4) offer a wide range of
ancillary social benefits (e.g., increase
fuelwood supply, reduce soil erosion, improve
preserve wildlife habitat) significant enough to
justify forestry options even without the
specter of global warming (Andrasko and
Tirpak, 1989; USDA/EPA, 1989). For a
general overview of climate change and forest
ecosystems and management (effects of
climate change, adaptation options, and
mitigation opportunities), see Andrasko
(1990a, 1990b).
Most research on greenhouse gas
emissions from natural and disturbed forest
ecosystems, and on the implications of
accelerating rates of tropical deforestation for
global change, has focused on emissions of
CO2 and CO and large-magnitude fluxes in
the carbon cycle from burning and gradual
decay of biomass associated with clearing of
tropical forests. Since less work has been
done on other gases, this section will
concentrate on the carbon cycle.
FOREST DISTURBANCE AND CARBON
EMISSIONS
The ecological diversity and geographic
range of vegetation communities determine
the degree of carbon sequestering by forests
and the rate of carbon emissions due to
disturbances of forests. Forests cover about
one-third of the Earth's land, or 4 billion
hectares (ha),8 of which about 42% is in
developed countries (mostly temperate) and
58% is in developing countries (mostly
tropical) (FAO/WRI/World Bank/UNEP,
1987). The carbon content of tropical moist
forests (with closed canopies, like Amazonian
rain forest) averages 155-160 tons of carbon
per hectare (t C/ha) of standing biomass in
Latin America and Asia and ranges up to 187
t C/ha in Africa.9 The carbon content of dry
tropical forests (closed or open forests on
relatively dry soils with grassy or herbal
ground cover) averages 27 t C/ha in Latin
America and Asia and 63 t C/ha in Africa
(Houghton et al., 1988).
Recent estimates of boreal (northern,
largely coniferous) forest in North America,
however, suggest that all of our carbon
content and biomass estimates commonly
utilized in calculations of global carbon cycle
fluxes may be seriously flawed. Botkin and
Simpson (1990) recently used more
statistically reliable methods to estimate
North American boreal forest biomass carbon
content at about 9.7 billion metric tons -
only one-quarter of previous estimates of 13.8
to 40 billion tons of carbon used routinely to
balance the global carbon budget.
Anthropogenic alterations of forest
ecosystems now account for emissions of
atmospheric CO2 equal to about 10-50% of
total emissions from combustion of fossil
fuels, as carbon stored in vegetation and soils
is released by clearing, fire, or decay
(Houghton, 1988a). Releases of gases
continue for a long time following forest
clearing; emissions of CO2, N2O, and CH4 in
Amazonia decline to one-third or one-half of
their initial rate after 10 days, but then
appear to continue for a year at a constant
rate (Goreau and de Mello, 1988). One
estimate of total CO2 emissions from burning
the entire Amazonia forest ecosystem suggests
that only 15% of the total carbon emitted
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Chapter V: Technical Options
would be contained in the initial biomass
burning; fully 85% would be released over
years or decades from soils (Fearnside, 1985).
Recent estimates of annual net carbon
flux from deforestation range from 0.4 to 2.6
petagrams (Pg) C/yr for 1980,10 primarily
due to land-use change in the tropics
(Detwiler and Hall, 1988b; Houghton et al.,
1987). Brazil, Indonesia, and Colombia were
the largest of the top ten producers of net
carbon release from tropical deforestation in
1980 (see Table 5-13), although new estimates
of forest loss rates for the 1980s move Burma
into the top three (WRI et al., 1990;
Houghton, 1989, in Myers, 1989). These ten
combined account for about 70% of the CO2
emitted due to changes in land use
(Houghton et al., 1987; WRI et al., 1990).
Very recent estimates of forest loss
rates, some not yet fully reviewed by the
forestry community and controversial, suggest
far higher rates of deforestation and, hence,
carbon emissions. Myers (1989) has estimated
that the rate of conversion of tropical closed
forests has risen 82% since the 1981 FAO
estimate of 7.2 million ha/yr of closed forests,
to 13.9 million hatyr for 1989. This produces
an estimate (by Houghton, in Myers, 1989)
for current emissions of carbon from
deforestation of 2.0-2.8 Pg, with a mean of 2.4
Pg, although this has not been widely
reviewed by experts. Similarly, a tally of new
country-level estimates for forest loss by WRI
et al. (1990; see below) suggests that the
standard FAO 1980 deforestation figure of
11.4 million ha may be revised upward by
other new studies to about 20.4 million ha for
1989/90.
Uncertainties still exist in determining
carbon storage in and emissions from changes
in forest cover associated with various land
uses. For example, emissions of greenhouse
gases from cropping practices in swidden (i.e.,
shifting, or slash-and-burn cycle) agriculture
versus sedentary (permanent) agriculture,
including agroforestry systems, have not been
quantified. Neither do we have reliable
estimates of biomass, carbon content, and
trace gas emissions in a truly representative
sample of natural and disturbed tropical
forests and carbon fluxes in disturbed tropical
soils (which may account for one-third of
carbon flux from deforestation) (Houghton et
al., 1988). Permanent conversion of natural
forest to pasture or cropland results in net
loss of carbon stored both in standing
biomass and soils; the amount lost is
dependent on the biomass productivity and
soil carbon storage rates of the former versus
the new land use. Cyclical harvest of forest
for timber or fuelwood similarly releases
carbon from slash (nonmarketable tree parts:
branches, leaves) that is burned or left to
decay on-site, and from timber milled into
non-durable wood and paper products (and
wastes like sawdust and scrap) that are soon
burned or discarded.
Forests in temperate regions are
essentially now in balance in terms of carbon
cycling, with annual incremental growth rates
roughly equal to rates of timber harvest and
deforestation for urban growth and other land
uses. Consequently, temperate forests do not
currently contribute significantly to the
increase in atmospheric CO2 (Houghton et
al., 1987). However, they now cover much
smaller areas than in the past, and have
historically contributed heavily to global
carbon emissions, as forests were cleared in
Europe, North America, and Russia for
agricultural production.
Widespread reforestation programs that
could expand temperate forests into former
forest ranges and reduce net carbon emissions
are discussed below. Trees newly planted in
urban areas would alleviate the greenhouse
problem in two ways: (1) by reducing the
need for air conditioning and hence
electricity, and (2) by increasing the uptake of
carbon in biomass growth (Akbari et al.,
1988).
DEFORESTATION
Each year, at least 11.4 million
hectares, and perhaps as much as 20.4 million
hectares (see below), of forest are cleared in
the tropics, an area larger than Austria or
Tennessee (Lanry, 1982; TIED and WRI,
1987). The rate of deforestation - combined
with the escalating growth in demand for
forest products - is such that while 33
tropical countries are currently net exporters
of wood products, this number may decline to
fewer than 10 by the end of the century
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Policy Options for Stabilizing Global Climate
TABLE 5-13
Estimates of Release of Carbon to Atmosphere from
Top 10 Deforestation Countries,
1980 and 1989
(million tons of carbon)
1980 1989
Brazil
Indonesia
Colombia
Ivory Coast
Thailand
Laos
Nigeria
Philippines
Burma
Peru
336.1
191.9
123.3
100.5
94.5
84.7
59.5
56.7
51.2
45.0
Brazil
Indonesia
Burma
Mexico
Thailand
Colombia
Nigeria
Zaire
Malaysia
India
454
124
83
64
62
59
57
57
50
41
Note: Estimates based on area deforested and biomass estimates, and
reflect limits in data available.
Sources: For 1980: Houghton et al., 1987; for 1989: Houghton, 1989,
in Myers, 1989.
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Chapter V: Technical Options
(Repetto, 1988). If this trend could be halted
and reversed, tropical forests could serve as a
vast carbon sink, reducing global CO2 levels.
Figure 5-11 illustrates the movement of
tropical forest lands among different stages of
the deforestation cycle (an approach used by
several researchers, e.g., Houghton et al.,
1985; Lugo, 1988). The figure also
summarizes the reductions or increases in
forestland conversions that could shift tropical
forests from net sources of greenhouse gases
to net sinks using the range of technologies
(i.e., forest management and land-use
practices) and policies identified below as
potentially available response options.
Deforestation pressures and their
socioeconomic and ecological consequences
are complex, however, and greatly complicate
the task of devising technical control
solutions.
The underlying causes of deforestation
vary widely by ecosystem and region, and are
often complex, involving the interplay of
historical, biological, economic, and political
factors at both macro (national and trans-
national) and micro (household and village)
levels. A recent international conference on
the state of the world's tropical forests
concluded that
the causes of deforestation are
well known. They include
population pressure for agricultural
land, the demand for industrial
timber production and export, and
inappropriate government policies
regarding land tenure, economic
incentives, forest settlement, and
other population issues (Bellagio,
1987).
The predominant causes of
deforestation vary by region. In tropical
Africa and in South and Southeast Asia, rapid
population growth appears to be the critical
factor affecting deforestation. The majority of
the population practices agriculture, and most
of the increases in agricultural production
necessary to sustain high birth rates have
come from increases in the area under
cultivation through deforestation. Seventy
percent of Africa's deforestation stems from
swidden (shifting) agriculture. Logging
activities, both commercial and individual, in
Malaysia, Indonesia, and the Philippines
provide access to partially cleared forest lands
that facilitates further clearing of forest for
agriculture (Houghton, 1988a).
Rural populations rely on wood as the
major source of energy, another important
cause of deforestation. More than a billion
people are currently affected globally by
fuelwood shortages. The fuelwood deficit in
arid and semi-arid regions of the world in
1980 affected 29.3 million people, and totaled
13.1 million cubic meters (m3) of wood. This
fuelwood gap between consumption and
supply is anticipated to grow to 130% for the
Sahelian countries overall by 2000, with
single-country forecasts as high as 620% for
Niger (Anderson and Fishwick, 1984).
One of the critical first steps in
devising ways to slow tropical deforestation is
for national and international development
assistance agencies to support local people in
introducing sustainable forest management
and reforestation techniques that provide for
basic needs - fuelwood, food, fiber, and
fodder -- for growing populations without
mining primary forest.
The Amazon region in Brazil is
experiencing one of the highest rates of
tropical deforestation in the world (Setzer and
Pereira, 1988; IIED and WRI, 1987;
Fearnside, 1987). As a consequence,
Amazonia is emitting greenhouse gases at
rates and quantities high enough to affect
global CO2 and climate cycles. Salati et al.
(1989) estimate that the Amazon region has
already emitted from 3.5 to 12 Pg C to the
atmosphere - totalling 2-7% of the total
release of CO2 to the atmosphere from
deforestation and biomass burning up to 1980
(see Table 5-14). Current annual emissions
from Amazonia alone are estimated at 0.24 to
1.6 Pg C, or 4-25% of global CO2 emissions
from all sources, assuming 7 Pg C per year
from all sources.
Centralized government policies that
undervalue standing forest and provide tax
and other fiscal incentives for conversion to
crop and pasture lands contribute to
increasing deforestation rates in Brazil
(Binswanger, 1987; Repetto and Gillis, 1988).
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Policy Options for Stabilizing Global Climate
FIGURE 5-11
MOVEMENT OF TROPICAL FOREST LANDS AMONG STAGES OF
DEFORESTATION AND POTENTIAL TECHNICAL RESPONSE OPTIONS
(Millions of Hectares)
OPTIONS TO REDUCE
SOURCES OF GREENHOUSE
GASES
* Decrease forost loss
to development
* Substitute sustainable
agriculture
• Improve efficiency
of blomass fuels
* Decrease production
of disposable wood
products
OPTIONS TO MAINTAIN
AND EXPAND GAS
SINKS
* Plant plantations
* Reforest degraded
forest lands
* Increase harvest
efficiency
* Increase forest
productivity
* Reforest degraded
lands
* Substitute sustainable
agriculture
* Plant plantations
* Support agroforestry
* Substitute sustainable
agriculture
* Reforest degraded
lands
Figure 5-11. Pathways of conversion of tropical closed and open forest lands, and where technical
response options discussed here would intervene to slow conversion. Data were derived from FAO
(1981) and from Lanly (1982) and are expressed in millions of hectares. Numbers inside boxes
represent total area in category in 1980. Numbers on lines tipped with arrowheads represent annual
rates of conversion. Data include both closed forests (complete canopy) and open forests
(incomplete canopy and grass herbaceous layer). Source: Pathway data modified from Lugo, 1988.
Houghton et al. (1985) offer similar conversion data.
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Chapter V: Technical Options
TABLE 5-14
Recent Estimate of CO2 Emissions from Biomass Burning in Amazonia
Range of CO2 Emissions
Estimate of Carbon (x 1015 g carbon')
Biomass Available3
(tons/ha = 108 g/km2)
Lower (140)
Upper (200)
Cumulative Totalb
3.5 to 8.4
5.0 to 12.0
Total in 1988C
0.24 to 1.1
0.34 to 1.6
NOTE: Estimate based on the assumption that 100% of the
burned biomass is transformed into CO2.
a Based on data from Martinelli et al. (1988).
b The total range of emissions is calculated as the product
of the lower and upper estimates of the carbon biomass
available and the lower (250,000 km2 in INPE, 1989) and
upper (600,000 km2 in Mahar, 1988) estimates of the total
area deforested.
c The range of emissions for 1988 is calculated as the
product of the lower and upper estimates of the carbon
biomass available and the lower (17,000 km2 in INPE, 1989)
and upper (80,000 km2 in Setzer and Pereira, 1991)
estimates of the area deforested in 1988.
Source: Salati et al., 1989.
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Policy Options for Stabilizing Global Climate
With the vast scale of its forest resources and
international pressures, Brazil has the
potential to slow deforestation if proactive
adjustments in government, commercial, and
colonizing forest use and development
practices are adopted (e.g., see discussion of
options to reduce biomass burning, below).
Brazil has 357 million hectares of
closed tropical forest -- 30% of the global
total, and three times as much as Indonesia,
which is second to Brazil in its extent of
forest area. The area deforested per year in
the Amazonian state of Rondonia tripled
from 7,600 square kilometers (km2) in 1980
to 26,000 km5 in 1985, while the population
increased roughly 15% per year during 1976-
81 (Malingreau and Tucker, 1988; Woodwell
et al, 1986). The major factors driving the
loss of forests include land speculation,
inflation, negative-interest and special-crop
loans, government tax and fiscal incentives
undervaluing standing forest (land is worth
more cleared than forested), production of
beef for export, and population redistribution
in response to high growth rates and the
mechanization of agriculture in southern
Brazil (Repetto and Gillis, 1988).
The situation in Brazil is changing
rapidly. Analysis conducted at the Brazilian
Space Research Center found that forest fires
during 1987 covered 20 million ha (77,000
square miles, or 1.5 times the area of New
York state), of which 8 million ha were virgin
forest (Setzer and Pereira, 1988). This
observation has forced reevaluation of
standard mid-1980s estimates (e.g., Lanty,
1982) of 11.4 million ha deforested for the
entire globe's closed and open tropical forests
and could raise estimates, to perhaps as high
as 20.4 million ha/yr for the 1980s. The wide
disparity between FAO's interim estimates for
selected countries and newer studies, often
relying on remote sensing, is shown in Figure
5-12 (WRI et al., 1990). The emissions from
these fires contribute roughly 10% of total
global emissions of CO2 (Fearnside, 1985). If
the Brazilian Amazon were completely
cleared, 11 Pg C would be released
immediately, augmented by a continuing
gradual release that would elevate the total to
62 Pg (Fearnside, 1985). Thus, deforestation
in Brazil poses serious global consequences
for climate change as well as the much
discussed loss of species diversity.
TECHNICAL CONTROL OPTIONS
Technical control options involving
forestry can sequester carbon through the
growth of woody plants, reduce anthropogenic
production of CO2, and complement other
strategies for reducing the buildup of
greenhouse gases. Forestry-sector strategies
for responding to the threat of global
warming fall into two major categories from
an economic standpoint: those technical and
policy options that reduce the demand for
forest land and forest products, and those that
increase the supply of forested land and forest
products. From a greenhouse gas accounting
perspective, these can be divided more
profitably into three classes:
1. Reduce Sources of Greenhouse
Gases;
2. Maintain Sinks of Greenhouse
Gases; and
3. Expand Sinks of Greenhouse
Gases.
Table 5-15 lists the components of these three
classes of forestry-related strategies.
The set of potential response options in
the forest sector fall into three categories.
First, adaptive measures in forest management
practices (e.g., planting drought-tolerant tree
species in areas likely to undergo reduced
precipitation during climate change, or
shortening tree-crop rotations to allow
planting of different species as growth
conditions change), which are not reviewed
here, offer one set of options (see Larson and
Binkley, 1989; Binkley, 1990; and AFA, 1990).
Secondly, technologies and land-use practices
are currently available that, if widely utilized
by forest managers, could reduce emissions
from forestry. These are reviewed here.
Lastly, government and corporate policies and
fiscal incentives could be generated that
would encourage market forces to reward
forest managers for greenhouse-positive forest
management (see CHAPTER Vffl).
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Chapter V: Technical Options
FIGURE 5-12
ESTIMATES OF ANNUAL DEFORESTATION
1981-1985 AND MOST RECENT
8
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Policy Options for Stabilizing Global Climate
TABLE 5-15
Summary of Major Forestry Sector Strategies
for Stabilizing Global Climate
Reduce Sources of Greenhouse Gases
• Substitute sustainable, sedentary agricultural technologies for swidden (slash-and-
burn) agriculture resulting in deforestation
• Reduce the frequency, interval, scale, and amount of forest and savannah
consumed by biomass burning to create pasture and maintain grassland
• Decrease consumption of forest for cash crops and development projects through
environmental planning and management
• Improve the efficiency of biomass (fuelwood) combustion in cookstoves and
industrial uses
• Decrease the production of disposable forest products (e.g., paper, disposable
chopsticks) by substituting durable wood or other goods and by recycling wood
products
Maintain Existing Sinks of Greenhouse Gases
• Conserve standing primary and old-growth forests as stocks of biomass offering
a stream of economic benefits
• Introduce natural forest management systems utilizing sustainable harvesting
methods to replace inefficient and destructive logging
• Substitute extractive reserves producing timber and non-timber products with
sustainable practices through integrated resource management and development
schemes
• Increase harvest efficiency in forests by harvesting more species with methods
that damage fewer standing trees and use more of total biomass
• Prevent loss of soil carbon stocks by slowing erosion in forest systems during
harvest and from overgrazing by livestock
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Chapter V: Technical Options
TABLE 5-15 (Continued)
Summary of Major Forestry Sector Strategies
for Stabilizing Global Climate
Expand Sinks of Greenhouse Gases
Improve forest productivity on existing forests through management and
biotechnology on managed and plantation forests
Establish plantations on surplus cropland and urban lands in industrialized
temperate zones to produce high biomass and/or fast-growth species to fix
carbon
Restore degraded forest and savannah ecosystems through natural regeneration
and reforestation
Establish plantations and agroforestry projects in the tropics using both fast-growth and
high-biomass species on short rotations for biofuels and timber
Increase soil carbon storage by leaving slash after harvest and expanding
agroforestry
V-lll
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Policy Options for Stabilizing Global Climate
In addition to the obvious benefit, from
the climate change perspective, of increasing
the supply of forested land (i.e., trees absorb
CO2), afforestation has a number of valuable
ecological and economic benefits worthwhile
on their own merits. For example, more
forests may mean more jobs in the forest
products industry, enhanced maintenance of
biodiversity, better watershed protection,
greater non-point pollution reduction, and
more areas for recreation.
Compared with the annual crop cycles
of agriculture, rotation time in forestry (the
time necessary for one cycle of a forest crop
to be planted, grown, and harvested) is slow,
typically on the order of 25-80 years in
temperate zones and 8-50 years in the
tropics where growth is faster. Essentially,
therefore, forestry climate strategies can
create a net CO2 sink for a fixed period,
albeit long, since trees eventually die or are
cut and release carbon through decay or
burning. Harvesting on short rotations, at the
point where the rate of mean annual
increment (MAI) of biomass added per year
begins to level off, in conjunction with
aggressive replanting, must be combined with
greatly expanded storage of carbon in durable
products like construction beams, crates, or
fences until they decay, and regeneration of
new biomass at high rates of growth and
carbon fixation.
The set of strategies in Table 5-15
could be evaluated by resource managers for
the optimal mix of land use and forest
management practices and policies best suited
for any given forest management unit (e.g., a
farm, watershed, national forest, integrated
development project, or nation). Some
options, however, are better suited to
industrialized countries and some are more
appropriate for developing countries.
Strategies for maintaining the volume of
standing stock, maximizing biomass growth
rates, and expanding the area in sustainably
managed, rapidly growing forest are all
needed. Species and ecosystems that produce
high volumes of biomass (e.g., Douglas fir old
growth in the Northwest, mixed hardwoods in
the East, and mahogany and teak in the
tropics) usually grow slowly (e.g., 70-200 years
to mature) and may be most useful as
response options in industrialized countries
and well-managed protected areas in the
tropics, where socioeconomic conditions favor
long-term forest protection and intensive
management. Developing countries especially
need to maximize biomass growth rates, to
restore degraded and desertifying lands, and
to produce fuelwood and timber. Developing
countries face rapid forest depletion and high
population growth rates, and have limited
institutional capability to guarantee long
forest rotation times in the face of these
realities. However, developing countries
should also plant high-value, long-rotation
hardwood stands and protect existing old-
growth forests from cutting and burning.
Because of the long rotation times for
forest growth, technical options will need to
integrate short-term educational, harvesting,
and research work with longer-term
adaptations in forest planting, management,
and product use.
All strategies should be, to the extent
feasible:
• sustainable over time, without
deteriorating the natural resource base or
introducing ecological changes (i.e., pests),
especially relying on improved management of
both undisturbed (virgin) and secondary
(disturbed or fallow) forests;
• capable of addressing the direct
and indirect causes of forest loss by providing
viable alternatives to current land-use
patterns;
• economically attractive (low-cost
and offering income commensurate to present
land uses);
• capable of providing an
equivalent spectrum of forest products (e.g.,
fuelwood, fodder) and jobs, at rates of return
to labor (or time) and capital comparable to
current forest-use patterns;
• socially integrative or adaptive,
building on local needs and tradition;
• technologically simple and
durable, to overcome low reforestation success
rates on lands degraded by human resource
use patterns (e.g., upland forests cut for
V-112
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Chapter V: Technical Options
timber and fuelwood and then overgrazed by
goat and sheep); and
• readily adaptable to changing
economic, political, social, ecological, and
climate change realities (e.g., civil war,
drought, resource-driven population shifts,
and climate change impacts on forest growth).
Table 5-16 presents a summary of
potential technical options for implementing
forestry strategies to reduce demand and to
increase supply.
Forestry Strategy I: Reduce Sources of
Greenhouse Gases
Both tropical and temperate forest
lands are in high demand to provide a range
of alternative land uses and forest products.
Forests are consumed in areas of rapid
population growth worldwide as villages and
cities expand, transportation corridors are
built to connect them, and additional arable
land is sought for food production. Other
major forces contributing to deforestation in
the tropics, include swidden (shifting)
agriculture, large-scale economic development
projects (often financed by multilateral
banks), cattle ranches and palm oil, timber
and rubber plantations, and fuelwood demand.
Based on population growth, projected
demand for fuelwood by the year 2000 will
require the creation of 20-25 million ha (or
perhaps as high as 50 million ha) of new
closed forest plantations for fuelwood, at a
cost of $50 billion, a rate 10-20 times current
planting tallies (Nambiar, 1984; FAO, 1981;
Lundgren and van Gelder, 1984). An
additional 200 million ha of croplands will be
needed (Postel and Heise, 1988) just to
maintain the already inadequate 1980 levels of
per capita food supply.
Currently, more than 10 hectares are
lost to each one that is planted, based on the
ratio of global deforestation to tree planting
(Lanly, 1982). Models of forest product
demand from 1980-2020 project tropical forest
removals (harvest for timber) to double
between 1980 and 2000, and then plummet to
72% of their 1980 level by 2020 (WRI and
IIED, 1988; Grainger, 1987).
Option 1: Substitute Sustainable Agriculture for
Swidden Forest Practices
Sustainable agricultural systems are
those that rely on biological recycling of
chemical nutrients in soils and energy, and on
naturally occurring mechanisms for protecting
crops from pests, to produce annual harvests
that can be sustained in perpetuity (Dover
and Talbot, 1987). Generally, such systems
use low levels of agricultural technology (i.e.,
minimal agricultural pesticides or fertilizers or
improved seeds, and few conservation
measures).
Sustainable agriculture, especially
agroforestry, offers all three major types of
greenhouse gas cycle benefits:
• Reductions of emissions of
greenhouse gases:
reduced demand for natural
forest wood products, since fuelwood, poles,
and fodder are grown in many sustainable
agricultural systems
reduced demand for new
land cut from primary or secondary forest for
swidden agriculture (by substituting higher-
nutrient sedentary systems on permanent
plots).
lower soil erosion, thereby
less volatilization of soil carbon and methane,
diminished reliance on
fertilizers, reducing N2O emissions.
• Conservation and enhancement of
gas sinks:
increased supply of woody
biomass fixing carbon in trees and soils in
forest-crop systems,
maintenance of soil carbon
stocks, due to reduced erosion.
Swidden agricultural methods involve
cutting and, usually, burning forest patches to
plant crops that are harvested for 1-7 years,
and then abandoning and leaving the patches
fallow for about 7-14 years as new patches are
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Policy Options for Stabilizing Global Climate
TABLE 5-16
Potential Forestry Strategies and Technical
Options to Slow Climate Change
Strategy
Technical Options
Regions Potentially Most
Effective In
Reduce Sources of Greenhouse Cases
Substitute sustainable agriculture
Small-scale agroforestry
Financial incentives for swidden colonists to shift
to sustainable practices
Technical aid in soil and crop selection
Plan into development projects by banks, state
agencies
Tropical moist and dry forests with strong central
governments (Brazil, Colombia, Malaysia,
Indonesia)
Decrease forest consumption for development and
sustainable agricultural systems
Assistance from multilateral banks and state
agencies contingent on planning. Loans
contingent on minimal forest loss
Mitigation of loss by 2:1 protection of forest
Government tax and fiscal policies to prevent
Strong central governments and banks with ability
to plan and manage (Brazil, Costa Rica, India,
China, Mexico)
Improve efficiency of biomass combustion
Widely distribute efficient cookstoves
Incentives for industrial cogeneration
Areas with inefficient current stoves, good
extension, and difficult-access or expensive
fuelwood (Nepal, India, Sahel, Haiti)
Decrease production of disposable forest products
Substitute durable wood products for disposables
Establish recycling programs for wood
Areas with cheap substitutes for wood and
developed markets (industrialized areas of
developing countries, Japan, U.S.)
Reduce biomass burning in forests and savannah
Manage savannah more actively to prevent
overgrazing of forage
Establish fire prevention plans and brigades in
forestry development projects
Provide government surveillance and enforcement
program
Savannah and dry forest areas already under
active management and readily accessible
Countries with remote sensing real-time detection
of fires and will to enforce
M-
Sinks of Greenhouse Ga
Conserve standing primary and old growth forests
Establish protected areas and prevent forest loss
Biosphere reserves
Old-growth forests in Pacific Northwest (U.S.),
and developed countries
Inaccessible and/or actively managed tropical
moist forest
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TABLE 5-16 (Continued)
Potential Forestry Strategies and Technical
Options to Slow Climate Change
Chapter V: Technical Options
Strategy
Technical Options
Regions Potentially Most
Effective In
Maintain IM«UH« Sinks of Greenhouse Gases
(Continued)
Introduce natural forest management (NFM) systems
Introduce widely several NFM techniques
Development or forest management projects in
tropics
Substitute extractive reserves for unsustainable
logging and agriculture
Extractive reserves for rubber, fruits, and nuts
Expand markets for non-timber forest products
Brazil, Indonesia, Malaysia
Tropical forests with indigenes and colonists near
markets and transport
Increase forest harvest efficiency
Increase number of species harvested
Decrease damage to standing trees
Use harvest slash and mill scraps
Any area, if marketed, and countries with large or
multinational logging concessions (Brazil,
Malaysia)
Prevent loss of soil carbon
Soil erosion via soil management, cover crops,
windbreak plants
Prevent overgrazing of pasture, forest via livestock
management and fodder tree planting
Dry forest and savannah in tropics
Hilly agricultural areas with active extension
programs
Expand Sink* of Greenhouse Ga
Increase forest productivity
Manage temperate forests
Apply natural forest management in tropics
Increase plantation productivity
Intensify timber stand improvement all forests
Apply fertilizers and biotechnology to plantations
Extend natural forest management practices
Developed countries and industrialized developing
countries, with extension capability
Plant trees on crop and urban lands in temperate
zone
Expand tree planting programs
Reforest croplands
Reforest urban areas
Reforest highway corridors
Reforest surplus cropland
Plant fast-growth plantations
Plant trees near buildings, highways, rivers
Developed countries
U.S.: Southeast, North Central states, West
Coast
V-U5
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Policy Options for Stabilizing Global Climate
TABLE 5-16 (Continued)
Potential Forestry Strategies and Technical
Options to Slow Climate Change
Strategy
Reforest degraded forest lands
Plant fuelwood and timber plantations in tropics
Increase soil carbon storage
Technical Options
• Incentives for agroforestry
• Establish extension farms and workers for
agroforestry
• Require commercial and village loggers to replant
• Plant strip-mined, overgrazed, and abandoned
lands in U.S.
• Organize village tree planting
• Mobilize youth and religious groups to plant trees
• Include plantations in all development projects
• Leave slash after harvest
• Prevent soil erosion with management practices
Regions Potentially Most
Effective In
• Tropics, where rainfall and soils are adequate
• Degraded lands in U.S., with adequate soil
nutrient and rainfall
• Throughout tropics, especially in moist soils and
in desertifying areas
• All managed temperate and tropical forests
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Chapter V: Technical Options
cut and farmed. About 41 million ha of
tropical primary and secondary forest are
burned annually (see CHAPTER VIII).
Tropical forests store up to 90% of a plot's
nutrients (some of which are released by
burning) in woody plants, compared with
temperate forests, where only 3% are stored
in plants and 97% in soils (Keay, 1978).
Swidden systems persist throughout the world,
especially in remote and hill districts, and
during times of individual or regional
economic stress. For example, on Negros
Island in the Philippines, the number of
swidden fanners rose by 80% in only two
years in the mid-1980s because of declines in
the sugarcane industry that forced under-
employed workers into swidden agriculture to
grow food. Ecologists predict that a major
rain forest there could be destroyed by the
year 2000 (Dover and Talbot, 1987).
Sustainable agriculture and soil
management systems can be introduced as a
substitute for swidden systems that destroy
virgin or secondary forest. For every hectare
farmers put into such methods, 5-10 hectares
of tropical rainforest may be saved from
destruction to store carbon, conserve
hydrologic cycles, and retain biological
diversity, according to Sanchez (1988). Table
5-17 shows the equivalent area of forests
needed for traditional swidden practices for
every one hectare of forest land needed for
more resource-intensive sustainable uses.
Agroforestry is the combination of
agricultural and forestry techniques to
produce woody plants on the same parcels as
food or commodity crops or animals, with a
mutually beneficial synergism. It offers one of
the most promising approaches for providing
both fuelwood and food needs, while reducing
greenhouse gas releases and environmental
externalities (e.g., pesticide use, pest
population surges, high irrigation
requirements) associated with monoculture!
row cropping. Interest in agroforestry has
surged since the late 1970s, and development
assistance for agroforestry during the mid-
1970s to mid-1980s reached $750 million in
approximately 100 developing nations (Spears,
1987).
Agroforestry systems derive from
traditional forest farming practices of many
indigenous peoples and are sustainable over
long rotations, large acreages, and low
population densities. The Lacandon Maya
Indians, who live in the rainforest in Chiapas,
Mexico, practice a multiple-layer cropping
system utilizing up to 75 species in one-
hectare plots that produce crops for 5-7 years.
As soil fertility wanes, the Lacandon plant
tree crops (cacao, citrus, rubber, avocado) that
provide valuable products as the plots
regenerate with secondary forest. This forest
is cut again when the trees overgrow the
managed species. It is estimated that only 10
hectares of rain forest are consumed per
farmer throughout his career with this method
of sustained agroforestry. In contrast,
immigrant colonists consume two or three
times as much forest area (Nations and
Komer, 1983).
Newer systems build on these local
methods by incorporating trees and bushes in
erosion-control strips, hedges, nitrogen-fixing
trees in fields, and cash and fodder crops
(e.g., see, Wimerbottom and Hazelwood,
1987; Dover and Talbot, 1987; Kidd and
Pimentel, forthcoming 1991; and OTA, 1984).
For example, a typical agroforestry system in
steep uplands with poor soils in Himachal
Pradesh, India, is stocked with 20.5 trees/ha,
which produce a yield of 2.0 m3/ha/yr of
wood, or 0.8 t C/ha/yr, plus the potential
savings of roughly a 5:1 ratio of hectare of
virgin forest retained intact per hectare
convened to permanent cultivation. A more
intensive stocking rate of 322 trees/ha in
home gardens in Surakarta, Indonesia, yields
7.3 nr/ha/yr wood, or 1.9 t C/foa/yr. Data
from Indonesia and Tanzania indicate that
200-300 trees are sufficient to provide wood
production needs of a typical household
(Lundgren and van Gelder, 1984). An
overview of potential carbon cycle benefits
from a range of agroforestry systems is
presented in Table 5-18, and a summary of
potential greenhouse gas reduction
implications of agroforestry is given in Table
5-19.
Obstacles to substituting agroforestry
for traditional agriculture include the need for
suitable environmental conditions (soils and
rainfall), and human population densities and
institutions adequate to encourage multi-year
resource management Either overcrowding
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Policy Options for Stabilizing Global Climate
TABLE 5-17
Comparison of Land Required for Sustainable
Versus Swidden Agricultural Practices
Sustainable Agricultural Practices
Number of Swidden Hectares Required
for Every One Hectare of Sustainable
Flooded rice
Low-input cropping (transitional)
High-input cropping
Legume-based pastures
Agroforestry systems
11.0
4.6
8.8
10.5
not determined
Sources: Derived from 17-year ongoing research by North Carolina State team at Yurimaguas,
Peru, in tropical moist lowland forest (Sanchez, 1988; Sanchez and Benites, 1987).
V-118
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Chapter V: Technical Options
TABLE 5-18
Potential Carbon Fixation and Biomass Production
Benefits from Representative Agroforestry Systems
Type of System
Natural forest
management and
crops
Steep uplands,
poor soils
system
Alley cropping
Trees
Per
Location Hectare
Guesselbodi
forest,
Niger
Himachal 20.5
Pradesh,
India
IITA,
Nigeria
Productivity
(t C/ha/yr) Species Used
0.8 native shrubs
(Combretum
micranthum,
Guiera
senegalensis)
0.8
0.9-3 nitrogen-fixing
shrubs (Glicidia,
Products Produced
wood, mulch, crops,
gums, fodder,
medicines
fuelwood, fodder,
crops
maize in alleys
between hedgerows
Leucaena, Calli-
andra, Sesbania)
cut for mulch and
stakes
Home gardens
Surakarta, 322
Indonesia
1.9
fruit, fodder, mulch
fuelwood
CARE Agrofor-
estry and Re-
source Conser-
vation Project
Guatemala 400
4.7 conifers (high-
lands), hard-
woods (lowlands).
20 species in total
fuelwood, fodder,
crops
Note: Soil carbon storage benefits are not available, and may be significant.
Sources: Winterbottom and Hazelwood, 1987, and WRI and IIED, 1988 (Niger, Nigeria); Lungren
and van Gelder, 1984 (India, Indonesia); Trexler et al., 1989, and WRI, 1988 (Guatemala).
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Policy Options for Stabilizing Global Climate
TABLE 5-19
Assessment of Potential Reductions in Greenhouse Gases from Large-Scale
Substitution of Agroforestry for Traditional Swidden and Monoculture! Agriculture
Source of Gas
Gas
Potential Effect of Agroforestry
Clearing of forest
Biomass burning
C02, CH4
C02, CH4,
N20, CO, NOX
Sustainable agroforestry would provide fuelwood and
fodder, reducing forest clearing for unsustainable
cropping and biofuels
Displacement of shifting cultivation would free forest
fallow for reforestation and carbon fixation in biomass
and soils
Cultivation and
degradation of
soils
Denitrification by
soils
Denitrification of
nitrogen fertilizer
Denitrification by
Rhizobium
CO,
N,0
N20
N2O
Reduced disturbance of soils during plowing, reduced
introduction of mulch to soils, and reduced erosion
should increase carbon storage in soils
Agroforestry could reduce denitrification by improving
soil chemical and physical properties
Agroforestry could substitute symbiotic fixation for
fertilizer use, reducing N2O emissions
Use of nitrogen-fixing tree species with associated soil
and by root Rhizobial symbionts could facilitate
denitrification
Source: Adapted from Franz, 1989.
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Chapter V: Technical Options
or pervasive poverty will shift the focus to
short-term survival. Social and economic
factors likely to promote success include clear
and relatively equitable land tenure for
farmers, local decision-making, political
systems that at least tolerate medium-term
investment by villagers of various classes,
developed and accessible markets for crop and
forest products, and adequate protection of
agroforestry systems from grazing livestock,
villagers, civil strife, and rapid economic
changes (Winterbottom and Hazelwood, 1987;
IIED and WRI, 1987).
Constraints to wide diffusion of
agroforestry include the difficulty of
technology transfer to remote populations
with traditional values that do not encourage
innovation, the need for systems tailored to
site-specific conditions, capital requirements
to purchase and maintain seedling nurseries
and to fund extension efforts and research,
and the vast scale of implementation
necessary to slow forest degradation
(Lundgren and van Gelder, 1984). The long-
term sustainability of new agroforestry systems
has not been fully demonstrated in many first-
generation projects, which often still rely
upon high levels of fertilizer and labor.
Option 2: Reduce the Frequency, Interval, and
Scale of Forest and Savannah Consumed by
Biomass Burning as a Management Practice
Techniques to reduce the frequency,
interval, and scale of forest and savanna
burned during management for livestock
grazing and for forest land conversion to
agriculture and grazing may offer significant
benefits in decreasing emissions from biomass
burning. Little analysis of this potential has
been performed. Another option may be to
expand fire risk management on selected
pasture and forest lands already under
intensive management in the dry tropics
through technology transfer. This option may
be feasible as a new best management practice
that alters burning frequency or extent enough
to reduce greenhouse gas emissions. No
detailed discussion of how such an expansion
for climate change purposes could be
achieved, and its benefits, is currently
available.
Relevant examples of potential fire
management practices include fire (and
grazing) protection of abandoned pasture land
around Guanacaste National Park, Costa
Rica, to allow natural regeneration of dry
forest (Jansen, 1988a, 1988b; see below), and
fire protection as a component of the
CARE/AES Guatemala forestry project
designed to offset CO2 emissions of an
electric plant in Connecticut (Trexler et al.,
1989; see below). In Brazil, the federal
environmental agency IBAMA launched a
vigorous burning management program in the
dry season of 1989 in which the space agency
INPE identified areas being burned through
remote sensing; a helicopter with
environmental police was then dispatched to
the site within 6 hours to ascertain if a burn
permit had been obtained and to levy fines.
IBAMA has indicated that this enforcement
program, along with the unusually long wet
season, contributed to a major reduction in
number of fires and area burned in 1989,
although the program is being challenged in
court at present and no fire fines have been
collected as yet (Setzer and Pereira, 1991;
U.S. EPA, 1989; Prado, 1990). Results of the
1990 dry season burning rates are eagerly
awaited by analysts and IBAMA.
The constraints in limiting burning are
many, including the low level of management
often associated with grazing lands, highly
decentralized land use and ownership, and
ecological reliance on burning to stimulate
nutrient flow and primary productivity of
grasslands. Exploratory analysis of biomass
burning response options is needed.
Option 3: Reduce Demand For Other Land
Uses That Have Deforestation as a Byproduct
Large development projects, especially
those planned in the tropics by transnational
corporations and multilateral development
banks, consume huge tracts of forest for
roads, hydroelectric project reservoirs, and
new communities. For example, the
Mahaweli project in Sri Lanka will destroy
260,000 ha of tropical moist forest in order to
generate 466 MW of electric power and
provide flood control and irrigation benefits.
The Narmada Valley Project in Madhya
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Policy Options for Stabilizing Global Climate
Pradesh, India, may inundate 350,000 ha of
teak and bamboo forest (Kalpavriksh, 1985).
Pressure on banks and governments to
reduce adverse impacts on tropical forests has
mounted since 1980 and spawned new
development planning methods that include
protection of forest tracts in order to offset
consumptive use of other forested lands
(Rich, 1989; Gradwohl and Greenberg, 1988).
In 1986, the World Bank issued a new six-
element policy on wildlands to guide planning
of Bank development projects. This policy
states preference for choosing already
degraded (e.g., logged over) and least valuable
lands for development purposes. It requires
compensation for wildlands converted by Bank
projects in the form of an added wildlands
management and preservation component
(Goodland, 1988; World Bank, 1986). India
is experimenting with compensatory
reforestation at a 2:1 replacement ratio for
forest cut for hydro projects. Compensatory
mitigation planning for forest areas during
development project design can be expanded
as a response option, although problems still
remain with such approaches, including
management responsibility over long time
frames and potential productivity rates of new
compensatory forests.
The probability of forest loss along
transportation corridors and in settlement
projects in Indonesia has been quantified by
Soemarwoto (1990) based on data on
population pressures, carrying capacity of
given land tracts, and targeted standard of
living. Several policies and practices with
potential to reduce forest loss in new planned
settlements, like the huge transmigration
projects in Indonesia, were noted by
Soemarwoto, including: increasing the
agricultural production per unit area by
improving technological inputs, introducing
crops with high market values, increasing off-
farm income, reducing the number of farmers
by providing alternative employment
opportunities through economic diversifi-
cation, and reducing the population growth
rate.
Forest loss for creation of new pasture
in Amazonia has been estimated for 1970 to
1990 at 17.5 million ha, emitting about 2.6
billion tons CO2, resulting in a net loss (after
accounting for growth of new biomass in
pastures of about 10 tons/ha/yr) of about 2.4
billion tons CO2 (Serrao, 1990). Response
options identified by Serrao (1990) to slow
this conversion include intensifying cattle
production on pasture already degraded, using
appropriate technology like second-cycle
pastures and silvo-pastoral systems;
regenerating degraded pasture with economic
tree species offering additional income; and
increasing use of existing natural grassland
ecosystems, now undergrazed, to reduce
demand for new pasture land.
Option 4: Increase Conversion Efficiencies of
Technologies That Use Fuelwood
Fuelwood demand from tropical dry
and moist forests accounts for significant
deforestation, although often biomass is
obtained from "invisible forests" around
villages, such as trees in densities so low that
they are not reported as forest area in
government statistics. Household biofuel
cooking systems contribute an estimated 2-7%
of the anthropogenic emissions of greenhouse
gases (Ahuja, 1990). Wood supplies over
90% of total energy use in Burkina Faso,
Malawi, Tanzania, and Nepal, 50% in
Indonesia, 25% in China, and 20% in Brazil
(Starke, 1988). Annual average fuelwood
consumption for agricultural and industrial
uses in Tanzania from 1979-80, for example,
was 1.9 million m3 of fuelwood, which
released 0.5 million t C to cure tobacco,
smoke fish, dry tea, fire pottery, and burn
bricks (Mwandosya and Luhanga, 1985).
The introduction of more efficient
cookstoves and industrial technologies could
reduce wood requirements by 25-70% at very
low cost (Goldemberg et al, 1987; Postel and
Heise, 1988). Current cookstove greenhouse
gas emissions of 2-7% may be halved at a
cost of about S12/ton C (Ahuja, 1990). The
most successful strategy for reducing
fuelwood-related deforestation in the long run
may be the substitution for inefficient biomass
burning cookstoves (5-12% efficiency) of more
efficient stoves powered by kerosene (40%),
gas, and electricity, and widespread
distribution of cogeneration technologies to
produce higher benefits from fuelwood use.
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Chapter V: Technical Options
Technical and policy options available
to improve stove efficiency and widely
disseminate better stoves include identifying
areas where biomass has a cash value and
biomass loss rates are high, and then
substitute kerosene or gas at subsidized prices.
The Annapurna Conservation Project of the
King Mahendra Trust in Nepal has
established kerosene depots that sell fuel at
fixed prices subsidized by permit fees collected
from tourist hill trekkers, and required all
trekking lodges in critical areas to replace
biomass with kerosene (ACAP, 1988). Cash
markets can be created for biomass through
fiscal incentives and regulatory mechanisms to
encourage use of improved stoves, fuelwood
conservation, and fuel substitution. New
portable, efficient stoves need to be mass
produced in order to reduce the unit cost,
and to create markets for the production and
sale of low cost stoves. Stove dissemination
should be linked to guaranteed, sustainably-
produced supplies of biomass from fuerwood
plantations integrated into energy and
resource management systems, which would
reduce pressure on natural forests (EPA
Cookstove Workshop, 1989).
Option 5: Decrease Production of Disposable
Forest Products
Forests harvested in developing
countries or managed in industrialized nations
to generate wood products that are consumed
and then burned or buried in landfills in the
short term (e.g., newsprint, paper goods, and
fast-food packaging) contribute greenhouse
gas emissions. Work has begun on
introducing technologies and programs to
replace consumable forest products with
durable goods that are used repeatedly and/or
recycled, avoiding these emissions and
providing carbon storage. Two major control
options are discussed below.
Substitute Durable Wood or Non-Wood
Products for High-Volume Disposable Uses of
Wood. Current storage of durable wood
products has been estimated at 6-10 billion
m3 of solid wood (2.6 Pg of carbon), or
roughly 25% of world industrial harvest over
the past 35 years (Rotty, 1986; Sedjo and
Solomon, 1989).
The global forest industry has been
stagnating for the past 15 years, as real prices
have decreased, growth in consumption has
shrunk, and competition on world markets
has accelerated from developing countries.
FAO (1986a) and Kuusela (1987), however,
project annual growth rates of wood-based
panels will be about 2.5-4.0% between 1985-
1995, down from 6.9% between 1963 and
1975, but along with printing and writing
paper the most quickly rising rate among
wood products. Total world production of
principal forest products for 1978-82 averaged
805.5 million t/yr, or about 0.4 Pg C/yr, and is
projected to rise to a mean estimate of 1333
million t/yr (0.66 Pg C) by 2000.
Accelerated harvest and storage of
wood products could provide one option for
reducing demand for products from virgin
forest and increasing supply from managed
forests. For example, if production of all
wood products was increased by 30% on
average above the projected growth from
1982-2000, and this increase occurred through
increased use of durable wood products, then
production would rise to 1733 million t/yr,
storing an additional 0.4 Pg C over the 18-
year period. Potential storage over the next
50 years to 2030 has not been calculated, but
might reach a total of more than 1 Pg C.
Examples of potential product shifts
from consumables to durables include
eliminating the use of disposable chopsticks in
Japan and elsewhere in favor of permanent
wood or plastic ones; replacing single-use
wooden crates and pallets with metal or
plastic ones; and widely installing wood
paneling in homes and commercial structures.
To achieve net greenhouse gas emission
benefits, production processes for durables
must minimize generation of gaseous
byproducts through use of energy conservation
measures noted earlier in this chapter.
Expand Recycling Programs for Forest
Products. Global production of newsprint,
paperboard, and other paper averaged 334
million t/yr from 1978-82, with growth rates
to 2000 anticipated at around 3% per annum
(FAO, 1986a,b).
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Policy Options for Stabilizing Global Climate
In the U.S., consumption of all paper
products in 1988 totalled 79.8 million tons.
Post-consumer recycling of paper in the U.S.
now provides 28% of domestic production of
paper and paperboard, and totaled about 22.3
million tons in 1986 - virtually twice the
amount recycled in 1970 (U.S. EPA, 1988).
Current obstacles to enhanced recycling rates
include market development, regulatory, and
financial issues (Ruston, 1988).
Recycling paper products in the U.S.
could be pursued as a climate change
response option. If, for example, recycling
rose to 80% (with 10% diverted to [stored in]
durable books or construction and 10%
disposed of), then the difference between the
number of tons burned or buried in landfills
in 1986 at 28% recycling (about 57 million
tons) and at an 80% rate (about 16 million
tons) would equal 41 million tonstyr.
Methane production from landfills (see PART
TWO) and carbon emissions from incineration
would decline. Paper products formerly
treated as consumables would convert to
essentially durable recycled products, thereby
increasing the net total stock of carbon
(assuming that forests previously used to grow
wood for paper remain undisturbed).
Forestry Strategy II: Maintain Existing Sinks
of Greenhouse Gases
Maintaining standing primary forests,
with their generally high levels of biomass per
unit area, offers significant advantages over
planting new stocks, and may be highly cost-
effective.
Option 1: Conserve Standing Primary and Old-
Growth Forests as Stocks of Biomass Offering
a Stream of Economic Benefits
Maintaining some high-biomass forests
as "carbon sinks" is likely to be far more
efficient from a greenhouse gas cycle
standpoint, more cost-effective, and less likely
to generate negative side effects than the
competing strategy of afforestation to fix
carbon (e.g., Postel and Heise, 1987).
Old-y
Douglas f
Northwest i>
carbon sinks •
'100-400year-old) forests of
• r species in the Pacific
'-.ave been suggested as
tiu.y have high recreational
and wildlife values (e.g., as habitat for the
endangered spotted owl), and are declining
rapidly in area. Old-growth forests offer
higher carbon storage than managed forests
per unit area, on average (Row, 1989).
In response to the debate about
whether to continue harvest of old-growth
forests or leave them as a sink, analysts have
used computer simulation models to estimate
the implications on global warming and
carbon storage, by comparing biomass
(carbon) in old-growth left standing with
managed Douglas fir harvested and replanted
with shorter rotation silvicultural systems
(Row, 1989; Harmon et al., 1990). Results of
the two studies differ. Row envisions net
carbon sequestration from harvesting old-
growth and replanting Douglas fir managed
on 70-year rotations of 15.0 tons of carbon/ha
over the first 70-year rotation, figuring that
15.5 tons of carbon would be emitted or lost
during old-growth harvest; but 34.1 tons of
carbon would be sequestered by the second
growth, and 3.5 tons of carbon would be lost
from the degradation (discarded, burned, or
decayed) of forest products made from the
harvested old-growth (the rest is assumed,
questionably, to be sequestered in products).
However, Harmon et al. reach the
opposite conclusion: old-growth harvest and
replacement with managed stands would
generate net carbon emissions, not sinks, due
to soil carbon loss, reduced growth rates of
new stands, and exaggerated claims of carbon
storage in forest products. Thus, conservation
of old growth stands in the Northwest (and
presumably in other locations) may offer
carbon storage benefits over replacement with
managed plantations. Further analyses are
required.
Option 2: Slow Deforestation by Introducing
Natural Forest Management of Little-Disturbed
and Secondary Tropical Forests
Natural tropical moist forests produce
annual wood increments higher than managed
forests on average (IIED and WRI, 1987;
Wadsworth, 1983) due to the latter's higher
harvest offtake volumes, minimal replanting
success, and reduced biomass in regenerating
forests. From a carbon-cycle perspective, this
argues in favor of a two-prong forest
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Chapter V: Technical Options
management strategy managing virgin and
secondary forests as sustainable high-biomass
sinks, and managing fast-growth plantations
for provision of forest products. Natural
forest management (NFM) techniques
(discussed below) can generate products and
services that sustain indigenous and village
populations otherwise engaged in forest
felling, and serve as high-biomass carbon
sinks. Natural forests comprise 83% (35
million ha) of the tropical forest under
intensive management; only 7.1 million ha of
intensively managed tropical forests have been
planted or artificially regenerated (IIED and
WRI, 1987). Hence, NFM, while requiring
considerable investments of labor, may
present the most viable long-run option for
forestry on a wide range of tropical forest
lands.
Net deforestation in an area results
when demand for timber, fuelwood, or
forested land exceeds the local supply and the
productivity rates of forest lands allowed to
regenerate do not keep pace with the
harvesting of products. One key method of
reducing demand for virgin or secondary
forest is to introduce sustainable natural
resource management techniques at the village
and regional levels that provide a stream of
forest benefits but minimize cutting of natural
forest. McNeely (1988) and McNeely and
Miller (1984) offer theory and case studies
illustrating the economics of non-consumptive,
integrated natural resource management.
NFM applies silvicultural techniques to
allow smaller sustainable harvests of natural
forests instead of traditional clear-cuts of
large tracts that only maximize short-term
profits. NFM may increase forest productivity
and provides a wide range of non-wood
products with high economic returns (e.g.,
nuts, herbal medicines, nature tourism
operations; see Gradwohl and Greenberg,
1988). Extractive reserves are a newly evolved
example of NFM in which economic products
like nuts and rubber are extracted from forest
reserves in Brazil. They maintain standing
forest while providing jobs and wages to
rubber tappers and nut collectors otherwise
dependent upon income from logging.
The Malaysian Uniform System is a 60-
year NFM rotation technique developed to
rapidly regenerate harvested dipterocarp forest
(lowland closed forest dominated by trees of
the Dipterocarpaceae family) in peninsular
Malaysia. Another method is the Celos
Silvicultural System, practiced on long-term
research plots in Suriname, which uses
carefully planned logging trails and winches to
reduce damage to standing trees during
harvest from 25% to about 12%. Numerous
small areas are cut on 20-year rotations rather
than single huge tracts, and three
improvement thinnings of non-target tree
species and vines are made each rotation.
The Palcazu Development Project in
Peru, funded by the U.S. Agency for
International Development, has devised a
system of active forest management that
harvests thin swaths of forest 20-50 meters
wide on 30-40 year rotations. Old-growth
forest left surrounding the strips naturally
provides seed dispersal after harvest, as in
natural tree-gap regeneration processes, and
maintains biological diversity lost in logging
operations. Potential net profits after the
wood is processed could be as high as
S3500/ha worked, according to estimates by
researchers (Hartshorn et al, 1987).
NFM systems could be widely
introduced via forest extension programs,
bilateral and multilateral rural development
projects, and integrated management of
protected reserves and adjacent lands (e.g.,
the Biosphere Reserve concept of multiple-
purpose protected areas combining
preservation, research, and economic use
zones [McNeely and Miller, 1984]). NFM
offers a promising vehicle for maintaining
high-biomass standing forest, slowing
deforestation, and allowing the 54 million ha
of forests already logged (WRI and IIED,
1988) to regenerate.
Option 3: Conserve Tropical Forests by
Developing Markets and Extractive Reserves far
Non-Timber Products
Multiple-use management of tropical
forests has been introduced in NFM,
Biosphere Reserve, extractive reserve, and
other land management systems to employ
sustainable timber harvesting, replanting,
stand improvement (release cutting), and
forest protection to confer benefits from
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Policy Options for Stabilizing Global Climate
timber sales, recreation, and flood control.
Fully 16% of tropical moist forest species
have non-timber economic benefits according
to one recent survey by IUCN (IIED and
WRI, 1987). For example, minor forest
products like rattan, latex, resins, medicinal
plants, and bamboo contributed S150 million
to Indonesia's economy in 1982 (Repetto,
1988).
Recent research has shown that tropical
deforestation, based solely on the value of the
wood products, does not make financial sense.
Perpetual, sustainable fruit and latex (rubber)
harvest offers far larger economic returns than
timber felling, plantation planting, or cattle
grazing on the same land parcel. The net
present value of future yields of a hectare of
species-rich Amazonian forest in Peru was
calculated by Peters et al. (1989) as S6330 per
hectare if fruits and latex are sustainably
harvested, as $1000 if all merchantable trees
are harvested at once (but $0 if as few as 18
fruit or latex were damaged during harvest),
as S490 if periodic selective timber cutting
occurred, as $3184 if the hectare of forest was
converted to a plantation of Gmelina arborea
managed for timber and pulpwood, and as
S2960 if converted to cattle pasture. The
combined financial worth of this hectare is
given as S6820, of which 90% is the market
value of fruits and latex (see Table 5-20).
Option 4: Improve Forest Harvesting Efficiency
Commercial forest management,
especially in tropical forests with extremely
high species diversity per hectare, has targeted
harvesting on only about 5% of species.
Reasons for this high-grading - selective
cutting of high-value trees ~ include
tradition, lack of demonstrated uses and
markets for other species, and the availability
of virgin stands open to resource "mining"
without costly management and with
government support. As a result, fully 85%
of total wood produced from tropical natural
forests in 1970 went unused, left as slash or
wasted at the mill (Goldemberg et al., 1987).
A survey of Malaysian and Indonesian
logged forests recently found that 45-75% of
standing trees had been injured (Gillis, 1988).
In southeast Amazonia, remote sensing study
has revealed that while 90,000 km2 had been
clearcut by 1985, three times that area
(266,000 km2) had been seriously damaged by
logging and colonization (WRI and IIED,
1988; Malingreau and Tucker, 1988).
Improvements in forest management would
reduce waste of non-target species damaged
during logging (e.g., the Celos Silvicultural
System, discussed under NFM options).
Efficient harvesting would require less
virgin and mature secondary forest to be cut
(Mergen and Vincent, 1987). Malaysian
government policy has raised the number of
commercial tree species for harvest from 100
in the mid-1960s to over 600 today (IIED and
WRI, 1987). The harvest and marketing of
under-used species and size classes throughout
the tropics, encouraged by government
regulations and forestry company practices,
could reduce tree losses from harvest and
improve stand yields more than silvicultural
innovations could, especially in secondary
forests (OTA, 1984).
Option 5: Prevent Loss of Soil Carbon Stocks
by Slowing Erosion in Forest Systems During
Harvest and from Overgrazing by Livestock
See Option 9: Increase Soil Carbon
Storage by Leaving Slash Harvest and
Expanding Agroforestry below.
Forestry Strategy III: Expand Sinks of
Greenhouse Gases
Option 1: Increase Forest Productivity:
Manage Temperate Natural Forests for Higher
Yields
Modern forestry management techni-
ques, including biotechnological (genetic)
improvement of selected species, applied to
commercial, state, and large private forest
lands offer the greatest potential for large-
scale increases in productivity.
In the U.S., new forest area growing at
average rates would not be sufficient to offset
our current annual production of 1.3 Pg C.
Per capita annual carbon production for 237
million Americans is about 5 t C/capita. U.S.
commercial forests (those producing greater
than 1.4 m3/ha/yr and not set aside in parks)
totaled 195.3 million ha in 1977, with a net
V-126
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Chapter V: Technical Options
TABLE 5-20
Value of One Hectare of Standing Forest in Amazonian Peru
Under Alternative Land Uses
Land Use System Net Present Value of Perpetual
Stream of Forest Products
Sustainable harvest of fruits and latex $6330
Clearcutting merchantable timber (not damaging fruit trees) $1000
Clearcutting merchantable timber (damaging >18 fruit trees) $0
Converting forest to Gmelina arborea timber/pulp plantation $3184
Converting forest to cattle pasture $2960
Total estimated value of hectare's forest products $6820
Source: Peters et al., 1989.
V-127
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Policy Options for Stabilizing Global Climate
average growth rate of 3.15 m3/ha/yr, or 0.82
t C/ha/yr. Thus, 6 ha (15 acres) of forest
would be required to sequester each person's
fossil-fuel emissions. For 237 million people
this would require 1.5 billion ha of average
forest -- a tract 50% larger than the 0.9
billion ha land area of the country (Marland,
1988).
However, intensive forest management
to increase biological productivity or
economic returns on forest land may offer a
partial solution. Presently, it remains unclear
whether increased stocking of existing stands
is likely to significantly increase total biomass,
or simply provide economic incentives that
increase the volume of merchantable timber
and hence store additional carbon by
encouraging more intensive management and
shorter rotations of larger stocks.
The U.S. Forest Service (USFS)
estimates that if current commercial forests
simply were fully stocked (i.e., they were
universally managed to grow the tree densities
and volumes of mature stands), their net
annual growth could be increased by about
65%, which would sequester 0.1 Pg Cyyr
(USFS, 1982). This full stocking option is
appealing, since many areas not presently
growing forests are sites so poor that even
intensive management or aggressive planting
are likely to provide only negligible net
annual growth (USFS, 1982). Forest Service
estimates also indicate that forest owners
could go further by managing forests to take
advantage of economically feasible
opportunities that would offer a 4% annual
return on investment. These management
options could produce an additional 18 billion
cubic feet of annual forest growth, equal to
0.16 Pg C (327 million t wood) (Hagenstein,
1988; Moll, 1988).
Intensive management techniques that
improve productivity include site-specific
species selection (through provenance trials
with seeds), thinning and release cuttings,
control of spacing among trees, weed and pest
control, fire suppression, fertilization,
irrigation, and planting of genetically
improved seedlings. All options requiring
significant labor tend to be prohibitively
expensive if implemented on large scales;
however, access to volunteer labor from youth
or citizen groups might make these options
more feasible on some lands, especially those
publicly owned.
Timber stand management measures to
assist forests in adaptation to climate change
conditions may accelerate the natural
processes of change in ecosystems expected
under increased temperatures and water
stress, thereby allowing silvicultural
intensification as a mitigation option.
By harvesting potential mortality prior
to its occurrence, managers can increase
production of merchantable volume, and allow
accelerated conversion of a stand to the suite
of species in the forest best adapted to a new
climate, according to stand simulation results
for a northern hardwood forest in New York
State (Larson and Binkley, 1989; see also
Kellomaki et al, 1988). Model results for 6
scenarios over 120 years in managed and
unmanaged stands are summarized in Table
5-21. An increase in soil moisture in this
northern stand drops productivity sharply.
However, adaptive management techniques
produce far greater merchantable volume than
productivity achieved in unmanaged
conditions, suggesting the benefits to
commercial management - and thus to
increased carbon storage, indirectly ~ of
intensive management.
A country-level case study of Finland
(reported in AFOS, 1989) reviews growth and
carbon storage of pine, spruce, and birch in
southern Finnish forests under existing
climate and management (i.e., planting
density, thinning, and harvest regimes), more
intensive management, and altered climate
(assuming a warming of 2°C for mean
temperature in growing season) and
management. Results reveal that Finnish
forests could store 273 million tons more
carbon in aboveground biomass in forests by
altering management techniques - a carbon
figure equal to total Finnish emissions of
carbon from fossil fuels during the next 39
years (if carbon emissions remain constant at
7 million tons per year). However, the
warming considered might stimulate tree
growth such that 470 million tons additional
carbon could be sequestered in forests ~
equivalent to Finnish fossil-fuel use for the
next 67 years. Altered management practices
V-128
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Chapter V: Technical Options
TABLE 5-21
Effects of Adaptive Forest Management Activities on Production of Merchantable
Volume for a Northern Hardwood Forest Under Two Climate Change Assumptions
Warm/Wet Scenario
Base (present)
Warm Scenario
Warm/Wet Scenario
Managed
4.97
7.57
3.16
Unmanaged
4.03
5.93
0.74
Difference
0.94
1.64
2.42
Note: Volume = mean annual increment, m3/ha/yr, for trees >18 cm.
Source: Binkley, 1990, based on Larson and Binkley, 1989.
V-129
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Policy Options for Stabilizing Global Climate
would be capable of increasing carbon
sequestration more than natural increases
from CO2 enrichment.
Other stand management options
potentially available to assist forests in
adaptation to climate change stresses and to
increase stand productivity include:
(a) Introducing drought- and pest-
resistant species, including exotics (e.g.,
Nilsson, 1989),
(b) Changes in harvest practices and
rotation lengths. Rotation lengths could be
shortened to allow for a faster response to
changes in stand productivity (e.g., Nilsson,
1989) and to harvest impending mortality via
more frequent and intensive thinnings
(Kellomaki et al., 1988). Planting species or
genetic strains better adapted to impending
changes in site conditions is widely
recommended. Coniferous plantations will
probably need more intensive tending to
thwart increasing competition from broad-
leaved species, and pest management will
need to be intensified (Kellomaki et al.,
1988).
The economics of fertilization on large
tracts varies. For many species and sites, the
costs of chemical fertilizers exceed the amount
of growth stimulated. Yet according to Ford
(1984), "fertilization is the most important
single treatment that the forest manager can
apply during the growth of the crop to
accelerate growth." More than half of the
loblolly pine plantations in the Southeast
would show value-added growth from
fertilization, according to one observer
(Binkley, 1986).
Obstacles to use of fertilizers include
low nutrient recovery rates for trees due to
leaching and microbial activity, the nutrient
status of the site, and whether slash is
removed from the site during harvest (tropical
forests store 90% of available nutrients in
biomass and only 10% in soils, compared with
about 3% for temperate forest biomass)
(Marland, 1988; Ballard, 1984). Increased
fertilizer use would probably increase
emissions of N2O (see PART FIVE), and may
interfere with CH4 uptake by soils, leading to
increased CH4 fluxes from forestland soils.
Further, a net analysis of the benefits of
fertilizer use from a greenhouse standpoint
has yet to be undertaken, but should include
the releases of CO2 during manufacturing and
transport of fertilizer.
Nitrogen-fixing legume species, like
black locust and honey locust in the U.S. and
Leucaena and Calliandra in the tropics, offer
the advantages of supplying their own nutrient
requirements, thus growing well in the
depleted soils of degraded lands and cutting
fertilizer costs.
Other constraints to intensive
management include the need for very short
rotations to maintain high growth rates and
associated labor costs, the need to sequester
large volumes of harvested wood, pest and
genetic diversity problems associated with
monocultural stands, costs of energy and labor
for plantations, the tradeoff between
maintaining large volumes of standing biomass
and fast growth rates, and fire management
costs.
Option 2: Increase Forest Productivity:
Plantation Forests
Plantation biomass productivity can be
improved by three types of actions:
1. Silvicultural practices that yield
biomass gains, especially in industrialized
country forests,
2. Lengthened and stabilized land
tenure for commercial and community forestry
projects in developing countries, to encourage
forest management for multiple (rather than
single) rotations and the ensuing
environmental benefits, and
3. Biotechnological advancements
utilizing genetics and seed selection.
This discussion focuses primarily on
biotechnology and genetic potential, since
Silvicultural management is addressed below
and land tenure considerations are discussed
in Chapter VIII.
Plantations managed to grow a mix of
short-, medium-, and long-rotation species, if
site conditions allow, are most likely to
V-130
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Chapter V: Technical Options
provide the continuous stream of forest
products and income necessary to meet timber
and fuelwood demand in developing country
villages. Similarly, mixed-stand (multiple
species) plantations in temperate zones may
reduce ecological problems (e.g., pest
infestations) and timber market disruptions,
although mixed-stand plantations may require
more intensive management and harvest
techniques.
Applied genetics or tree improvement
may produce greater increases in yields of
biomass than improved silvicuitural methods.
Short-rotation intensive culture (SRIC) efforts
apply intensive agronomic practices to
growing selected and/or genetically improved
hardwood species in plantations to achieve
maximal productivity rates at competitive
costs. The Department of Energy's Short-
Rotation Woody Crops Program, begun in
1977, has conducted field trials to boost
productivity and reduce costs of woody species
managed under SRIC as an energy source. Its
target is to achieve average productivity of 20
dry t/ha/yr (10 t C/ha) of biomass at a cost of
S2.25/GJ on optimal plots by 1995, and a
competitive technology 5 years later.
By 1987, productivity reached 13 dry
t/ha/yr (6.5 t C/ha) at a cost of $55/dry t, or
S3.25/GJ (ranging from $2.90 to $5.10
delivered), on Soil Conservation Service
(SCS) site class I-III soils (i.e, largely fertile
and flat). Planting densities ranged from
2500-4000 trees/ha, on coppice rotations of 5-
8 years. Ongoing research is focused on four
species (silver maple, sweetgum, American
sycamore, and black locust) and one genus
(Popuhts, including cottonwood, poplar, and
aspen). Collectively, average SRIC growth
rates have reached about 9.5 dry t/ha, or 4.7
t C/ha. Rates as high as 12-14 t C/ha have
been documented for exotic or hybrid trees
(Ranney et al., 1987).
Other species with high potential for
plantation biomass production include wood
grass (Popuhts), grown at densities of about
1700 trees/ha for 4-year rotations, and 25,000
trees/ha for 2-year rotations (Shen, 1988).
Kenaf, an African annual crop closely related
to hibiscus, grows to 6 meters in 120-150 days
after seeding, and can produce 3-5 times more
pulp for paper than trees on an annual basis,
which potentially frees forests for biomass
production and carbon storage. Field trials in
Texas by the U.S. Department of Agriculture
(USDA) have found that kenaf grows well
without pesticides in the Cotton Belt and with
irrigation in the drier Southern states, and
requires less chemical input than wood to
produce and whiten pulp. Ninety percent of
its original weight can be converted to usable
fiber (Brody, 1988).
Working with tropical species in
Espirito Santo, Brazil, the Aracruz Pulp
Company has produced eucalyptus hybrids
with 30% increased height and 80% improved
diameter at breast height (dbh) compared to
parent trees at four years through selection of
parent tree seeds, breeding for desired
characteristics, and planting into specific
microsites. Average yields of 70 nr/ha/yr
(18.2 t C/ha/yr) for 14 million trees per year
grown from rooted cuttings of 54 species have
been achieved, and yields of 100 m3 (26 t C)
or greater are projected. Stands are managed
for bleached pulp and charcoal for steel
making. The trees reach 20 meters in height
in less than three years (OTA, 1984; IIED
and WRI, 1987). Other trials with eucalyptus
from 32 sites in 18 countries have generated
productivity gains of several hundred percent
simply by matching optimal seed character-
istics with site soil and microenvironmental
conditions (Palmberg, 1981).
Pine breeding for straightness, reduced
forking, and drought resistance, coordinated
by seed cooperatives in Latin America and
Europe, is showing significant improvements.
Other tree-improvement methods include seed
orchards that rely on grafting and rooted
cuttings to produce clones of trees, but these
methods are limited to only a few species.
Tissue culture (manipulating sprouts from
germinating seeds) is still in its infancy in
forestry, although the Weyerhaeuser Corpora-
tion in the U.S. Northwest soon plans to
produce 100,000 clones of Douglas fir per
year. Research on producing cell culture
embryoids (microscopic infant trees) is
underway in major developed countries on
temperate species, and early work on teak and
Caribbean pine is encouraging (IIED and
WRI, 1987).
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Policy Options for Stabilizing Global Climate
Table 5-22 surveys productivity
increases from intensive management and
applied genetics for selected species in the
U.S. and in the tropics.
The implications for carbon fixing are
clear. A 30% rise in biomass production
allows 30% less land in forest, or a 30%
offtake of fuelwood or timber to achieve the
same results. Drought-resistant strains would
encourage forest sector and donor community
investment in arid and degraded land projects.
The potential benefits of productivity
increases on plantation forests are currently
limited by the slow pace of research and field
trials on promising species and varying site
conditions. Eighty-seven percent of
plantation forestry in the tropics focuses on
species of only 3 types: pine, teak, and
eucalyptus (Vietmeyer, 1986). Obstacles to
expanding plantations are reviewed below.
Option 3: Expand Current Tree Planting
Programs in the Temperate Zone
Forested area in temperate and boreal
zones is considered roughly constant in most
studies but may be declining in this decade
(Houghton, 1988a). The U.S. had an
estimated 445 million ha (1.1 billion acres) of
forest land circa 1630. By 1987, forest area
had declined to 296 million ha (731 million
acres), still 32% of our land area. However,
temperate forests were much larger
historically and could be expanded. Some
European countries have increased their net
forested area: France was 14% forest in
1789; today, 25% of France is forested (Postel
and Heise, 1988).
According to the Forest Service, total
U.S. tree planting by federal and state
agencies revegetated 1.2 million hectares (3
million acres) in 1987 (USFS, 1987). Table
5-23 lists the five major tree-planting
programs in the U.S. since 1935 and the
number of acres planted in their highest
5-year period.
If current programs planted 1.2 million
ha with existing financial and programmatic
incentives geared to replacement levels of
planting, then additional enticements on the
order of $220-345/ha ($90-140/acre) would
probably stimulate tree planting on hundreds
of thousands of hectares. The Conservation
Reserve Program of USDA (see below) paid
an average of S219/ha (average rental payment
of $125/ha or S50/acre plus half of
establishment costs at an average of S94/ha)
to plant 850,000 ha of trees (2.1 x 106 acres)
from 1986 to mid-1988. Youth groups could
be mobilized to plant trees annually on Arbor
Day or during weekend or summer work
camps.
Large-scale reforestation by individuals,
companies, and/or government programs has
been proposed as a possibility in temperate
zones. However, this would be far less cost
effective (by perhaps a factor of 3-10) than in
the tropics because of higher land costs and
slower tree growth. Recently, more targeted
proposals for tree planting in the U.S. focus
on use of croplands that are considered
surplus during periods of diminished exports
and high-cost land for farm support programs.
Option 4: Reforest Surplus Agricultural Lands
Reforestation of economically or
environmentally marginal ("surplus") crop and
pasture lands has been proposed as the
quickest, most cost-effective way to stimulate
tree planting at the scale necessary to partially
offset CO2 emissions (Dudek, 1988b; Postel
and Heise, 1988; Andrasko and Tirpak, 1989;
Moulton and Richards, 1990; USFS/EPA,
1989). Planting tree carbon sinks may be
comparatively cheaper than other current
CO2-limiting options, for example, planting
short-rotation biomass energy plantations,
investing in energy conservation measures, or
scrubbing CO2 from industrial emissions
(Dudek, 1988a,b).
The most commonly suggested model
for afforestation is the Conservation Reserve
Program (CRP) administered by USDA The
CRP was established by the conservation title
of the Food Security Act of 1985 to retire
highly-credible cropland, reduce production
and boost prices of surplus food commodities,
and reduce Treasury outlays. Participating
landowners contract to retire cropland for 10
years. They are reimbursed for 50% of the
costs of planting the necessary vegetative
cover, and receive an annual rental payment.
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Chapter V: Technical Options
TABLE 5-22
Productivity Increases Attributable to
Intensive Plantation Management
Maximum
Mean Annual Yield
Management Technique (Tons carbon/ha/yr)
Douglas Fir in Washington
Natural stands 2.8
Silvicultural treatments
Plantation establishment 3.6
Nitrogen fertilization 4.4
First-generation genetics 4.9
TARGET 12.5
Loblolly Pine in North Carolina Pocosins
Natural stands 1.8
Silvicultural treatments
Drain and plant 3.5
Bedding 4.3
Preplant phosphorus 5.3
Nitrogen fertilization 5.9
First- and second-generation genetics 7.2
TARGET 15.0
SRIC Hardwoods, Various Sites in U.S.
Short rotation, genetics, site preparation, fertilizer, coppicing 6.5
TARGET for year 19% 10.0
Energy Crop Plantations, Temperate Zone
Intensive management, mixed species;
TARGET for year 2025 24.7
Eucalyptus Hybrids in Espirito Santo, Brazil
Seed selection, breeding, microsite planting 18.2
TARGET 26.0
Source: Based on Farnum et al., 1983, and Marland, 1988 (Douglas fir and loblolly pine); Ranney
et al., 1987 (SRIC hardwoods); Walter, 1988 (energy crop plantations); WRI and IIED, 1988
(Eucalyptus).
V-133
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Policy Options for Stabilizing Global Climate
TABLE 5-23
Summary of Major Tree Planting Programs in the U.S.
Program
Civilian Conservation Corps (CCC)
Soil Bank
USDA-Forest Service Reforestation
Forestry Incentive Program (FIP),
Agriculture Incentive (ACP)
Conservation Reserve Program (USDA)
Period
(Highest 5 years)
1935-39
1957-61
1979-83
1978-82
1986-90 projected
1986-89 actual
Land
(acres)
1.4
2.0
1.5
1.1
5.6
2.0
Planted (x 106)
(hectares)
0.6
0.8
0.6
0.4
2.3
0.8
Sources: Conrad, 1986; USDA, Land Retirement and Water Quality Branch statistics on
conservation Reserve Program enrollment, November, 1988.
V-134
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Chapter V: Technical Options
Participation in the tree-planting
program was targeted at 12.5% of projected
total retired acreage (16.2-18.2 million ha, or
40-45 million acres by 1990), or about 2.3
million ha (5.6 million acres). However, tree-
planting enrollment totals only 0.40 million
ha (of 10.5 million ha enrolled in CRP by
November 1988), mostly in Southern states
already producing plantations of loblolly pine
in favorable soils and climate. Planting rates
have been low due to low bid prices,
reluctance of fanners to lose base acreage in
federal crop support programs, and
inadequate support for tree planting by
extension offices. Better financial incentives
(i.e., higher bid prices, higher share of
planting costs paid) and open, continuous
enrollment opportunities may greatly increase
tree acreage enrollment.
For example, all new CO2 emissions
from fossil-fuel electricity plants projected for
1987-96 could be offset by planting trees (see
Table 5-24). Estimates of planned increases
in fossil-fuel electric generating capacity for
1987-96 total 25,223 MW, producing 45.5 Tg
C (equivalent to 166.7 million tons CCM
(NAERC, 1987).
The uptake of CO2 varies by species.
Silver maple, for example, a relatively
inefficient species, absorbs 5 t C/ha/yr under
optimal conditions, while American sycamore
absorbs as high as 7.5 t C/ha/yr (Steinbeck
and Brown, 1976; Marland, 1988). Depending
upon the species chosen, it would take
between 4.5-13 million ha of short-rotation
(4-5 years) monocultural plantations on good
sites to offset the planned 25,223 MW of
additional fossil-fuel electricity.
Mixed stands of numerous tree species
are more desirable to prevent ecological
problems associated with monocultural stands
such as increased pest populations, low
species diversity, and vulnerability of even-
aged stands. The acreage requirements for
mixed stands to offset 45.5 Tg C could rise to
13 million ha (32 million acres), or about
70% of the total enrollment target for the 10-
year CRP program. Further analyses are
underway to consider availability of productive
soils, variations in actual site characteristics,
and mixed-stand productivity rates (e.g., AFA,
in press).
USDA's share of costs for establishing
trees on CRP acres averages $94 per hectare,
plus rental payments averaging S125 per ha
per year for the 10 years of the current CRP.
If the full costs of the planting are assumed
to be $370/ha, and fertilizer costs are S62/ha,
then the mid-range estimate of 9.1 million ha
of trees added to the CRP would cost S3.9
billion to establish (S3.1 billion if current
average USDA cost-share expenditures
continued). Rental payments by USDA or
utilities, estimated to rise to about S250/ha/yr,
would need to continue over the 50-year life
of the electricity plants whose emissions
would be offset Some lands not presently
producing timber or crops might be available
for afforestation. In 1976, the U.S. had 70
million ha (173 million acres) of land out of
production with average rainfall greater than
50 cm/yr. Although the land was used for
recreation or other purposes, it may offer
suitable (although not optimal) habitat for
tree planting (Fraser et al., 1976). Any
additional lands required would have to be
diverted to forestry from other competing
land uses.
U.S. EPA developed a national plan to
offset 10% of current U.S. emissions of CO2
in June, 1989, called "Reforest America"
(Andrasko and Tirpak, 1989) that identified
five program components: 1) federal lands
(planted with new trees or more intensively
managed), 2) rural surplus agricultural lands
(planted), 3) urban parks, residences, and
commercial buildings (planted), 4) private
timberlands (more intensively managed), and
5) Conservation Reserve Program lands
(private croplands enrolled in a USDA
program, and planted). The plan estimated
that 10-20 billion trees would need to be
planted on 5.7-10.5 million ha (14-26 million
acres), and 13.8-23.5 million ha (34-58 million
acres) of forest managed more intensively to
fix 81-127 million t Cfyr at a federal sector
cost of $146-193#r (plus private sector costs).
Moulton and Richards (1990) have
performed the most sophisticated analyses
thus far to estimate the cost per ton of
carbon sequestered by tree growth in large-
scale afforestation programs for lowest-cost
pasture and crop lands in the U.S.,
summarized in Figure 5-13. "Trees for U.S.,"
a federal government executive branch
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Policy Options for Stabilizing Global Climate
TABLE 5-24
Estimates of CRP Program Acreage Necessary to Offset
CO2 Production from New Fossil Fuel-Fired Electric Plants,
1987-96, by Tree Species or Forest Type
Carbon Fixing Rate Land Requirements for Offset (million)
Tree Species/Forest Type Used (t C/ha/yr) Hectares Acres
Average growth U.S. commercial
forests 1977 (USFS, 1982)
Average growth US commercial
forests fully stocked (USFS, 1982)
Estimate for large mixed stands
of moderate-growth species
Silver maple (Ranney et al., 1987)
SRIC program average productivity
by 1987 (Ranney et al., 1987)
American sycamore (Marland, 1988)
SRIC program target for 1996
(Ranney et al., 1987)
SRIC program, highest documented
from exotics (Ranney et. al., 1987)
Loblolly pine, target after genetics
(Farnum et al., 1983)
0.82
1.35
3.5
5.0
6.5
7.5
10.0
13.0
15.0
55.5
33.7
13.0
9.1
7.0
6.1
4.5
3.5
3.0
137.1
83.2
32.1
22.5
17.3
15.1
11.1
8.6
7.4
Notes:
1. New fossil fuel-fired electric utility plant emissions are assumed to be 166.7 million tons CQ2 total
for period 1987-1996 (or 45.5 Tg C) (Dudek, 1988a; NAERC, 1987). 1 metric ton CO2 = 0.27 ton
carbon.
2. 1 ton biomass = 0.50 ton carbon. 1 hectare — 2.47 acres. Units are expressed as metric (not
English) tons/acre for comparison.
3. Rotations for all estimates are assumed to be 4-5 years.
4. The carbon fixation rates for silver maple and American sycamore differ from those cited in
Dudek (1988a), following personal communication with Dudek.
V-136
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Chapter V: Technical Options
FIGURE 5-13
Dollars/Ton
SO
COST CURVES FOR POTENTIAL LARGE-SCALE
AFFORESTATION IN THE U.S.
Marginal Cost of Carbon Sequestering
(Dollars/Ton of Carbon at Margin)
40
30
20 -
10 -
.«
200
400 600
Millions of Tons of Carbon Sequestered
800
Total Annual Cost of Carbon Sequestering
Billions of Dollar*
25
20
15
10
100 200
Source: Moulton and Richards, 1(90.
300 400
Tom ol Carbon Saqu
1000
SOO 800 700 800 900
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Policy Options for Stabilizing Global Climate
proposal prepared by USFS and U.S. EPA in
the fall of 1989, was built on "Reforest
America" and work by Moulton and Richards.
The proposal consisted of a four-component
plan to (1) offset 1%, 2%, 5%, or 10% of
U.S. CO2 annual emissions through increased
cost-sharing for the existing USFS Forest
Incentives Program (FIP) and Agricultural
Conservation Program (ACP), (2) plant
community forests, and (3) use surplus low-
cost pasture lands (theoretically available at
25-35% of the cost of rental payments for
surplus crop lands). Total cost estimates are
$1-12.9 billion over 20 years (roughly $50-210
million/yr, on average) for the 1-10% options,
respectively (USDA/U.S. EPA, 1989).
Analyses of options to use economic
incentives to accomplish the program, impacts
of such national afforestation programs on
food and fiber supplies and prices, ecological
implications, and the role of volunteerism in
tree planting and maintenance have been
undertaken or are in progress. Table 5-25
compares these recent estimates to other
studies of costs and acreage requirements.
President Bush announced a major
reforestation program as part of a broader
conservation initiative (America the Beautiful)
in January, 1990, based on the USFS/U.S.
EPA analyses. The new tree plan calls for
planting 1 billion trees per year for about 10
years, on 600,000 ha of private land. In
addition, 30 million trees/yr would be planted
in communities, and 73,000 ha/yr of private
forest land would be more fully stocked or
undergo timber stand improvement via a
50/50 federal/private cost-share arrangement.
Total estimated cost of the program would be
$175 million/yr, beginning in the Ml of 1990,
if approved by Congress. If fully
implemented, the plan would offset 1-3% of
current U.S. CO2 emissions after all trees are
planted and mature -- a small but significant
first step by a major greenhouse gas emitter
to use forestry to slow CO2 accumulation.
Australia announced its One Billion
Trees plan in 1989, to restore its degraded
subtropical and temperate forests, offset
climate change, and conserve biodiversity.
The plan entails planting 1 billion trees on 1
million ha by 2000, including 400 million in
community planting, and 600 million in
natural regeneration and direct seeding, plus
a National Afforestation Program to establish
hardwood plantations. Establishment costs
are estimated at AS300-2,000/ha, with a total
of AS320 million over 10 years. Carbon
benefits are expected to be 6-10 million tons
of carbon per year, and 300-500 million tons
of carbon over the 50-year lifetime of the
program (Eckersley, 1989; Hawke, 1989).
The stream of direct and indirect
benefits that would accrue from afforestation,
including timber harvest, reduced soil erosion
and nonpoint source water pollution,
increased recreational use, and increased
wildlife have not been considered yet, and
would tend to reduce costs attributed to
climate change programs if utilities or farmers
managed forested land for multiple uses.
Quantification of these potential benefits is
needed.
CO2 uptake rates might be increased
through biotechnology improvements to
perhaps 10 t C/ha/yr within 10-15 years
(Ranney et al., 1987). Higher uptake rates
would reduce both offset acreage
requirements and costs. If economic
hardwood species like American sycamore
(used in flooring and millwork) and silver
maple (for furniture and box and crate
production) or softwoods (for lumber) are
harvested for durable products, carbon storage
would continue after harvest.
Option 5: Reforest Urban Areas
Urban areas, which currently contain
75% of the U.S. population on 28 million ha,
are increasing by 0.53 million ha (1.3 million
acres) per year (USDA, 1982). A study of
urban forests in 20 cities found that for every
four trees removed only one tree is planted,
and for one-third of the cities, only one in
eight trees lost is replanted (Moll, 1987).
The total number of trees in Chicago dropped
by 43,853 between 1979 and 1986. Trees
planted per year declined from 24,675 in 1979
to 9380 in 1980 (NASF/USFS, 1988; Open
Lands Project, 1987).
An urban tree is about 15 times more
valuable than a forest tree in terms of
reducing CO2 emissions. Trees break up
urban "heat islands" by providing shade, which
reduce cooling loads (air conditioning) in
V-138
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Chapter V: Technical Options
TABLE 5-25
Estimates of Forest Acreage Required to
Offset Various CO2 Emissions Goals
Estimate
Dyson and Mariand (1979)
Marland (1988)
Myers (1988)*
Sedjo and Solomon
(in press)
Woodwell (1987)
Pastel and Heise (1988)
Dudek (1988a,b)
EPA (this study)
Andrasko and Tirpak (1989)
USFS/U.S. EPA (1989)
Location
Temperate Zone
Tropics
Tropics
Tropics or
Temperate
Tropics
Tropics
U.S.
U.S.
US.
U.S.
Carbon
Sequester
Rate Assumed
(tC/na/yr)
7.5
9.6
10.0
6.2
5.0
6.8
10-12
3.5-10
4.4
5.7
5.7
Offset Goal
5 Pg C (total annual fossil fuel use)
5 Pg C (total annual fossil fuel use)
2.9 Pg (net annual increase C)
2.9 Pg (net annual increase C)
1-2 Pg (net annual increase C
from tropics)
0.7 Pg (C benefits from new fuelwood
plantations and restored forests)
0.05 Pg (1987-96 new electric plant C)
0.05 Pg (1987-96 new electric plant C)
0.12 Pg/yr
0.06 Pg/yr
0.12 Pg/yr
Hectares
(million)
700
500
300
465
200-400
110
3.4-4.5
4.5-13
10.5d
8.1e
is-of
Total
Planting
Cost
($ billion)
120
186 tropics
372 temperate
1.6-1.9°
1.9-5.6°
6.4
9.4
19.2
Average
Cost/ha
($)
398
395
800-1400b
432C
432C
a See also Booth, 1988.
b Includes $400/ha land purchase cost.
c Assumes no cost-sharing of establishment costs and no annual rental payments (see text).
d Assumes 10.S million ha planted and 23.S million ha more intensively managed.
e Assumes 8.1 million ha planted and 4.3 million ha intensively managed.
f Assumes 1S.O million ha planted and 10.8 million ha intensively managed.
V-139
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Policy Options for Stabilizing Global Climate
warm weather by reducing the building's heat
gain, and cuts heating loads in cool weather
by slowing evaporative cooling and increasing
wind shielding. Three strategically placed
trees per house can cut home air conditioning
energy needs by 10-50% (Akbari et al., 1988).
Trees planted as windbreaks around houses
and buildings also can reduce winter heating
energy use by 10-50% (Robinette, 1977).
Thus, urban trees both sequester CO2 and
reduce consumption of fossil fuels, making
strategic planting around buildings a small but
efficient response option (Meier and Friesen,
1987). The American Forestry Association
(AFA) recently conducted a survey of urban
forest needs and launched in the fall of 1988
Project ReLeaf, which intends to plant 100
million trees in city streets, parks, and rural
areas. Akbari et al. (1988) estimate savings
of 40 billion kilowatt-hours of energy from
these new trees, which would provide a
carbon cycle benefit equivalent to 4.9 Tg C
annually. This benefit would accrue from a
combination of CO2 absorption and reduced
emissions from electricity generation.
Option 6: Pursue Afforestation for Highway
Corridors
Highway corridors offer significant op-
portunities for tree planting, along 6.2 million
kilometers (km) (3.9 million miles) of roads
in the U.S. In 1985, 11.9 million ha (29.5
million acres) of land totalling 1.3% of the
contiguous U.S. were in use as highways,
including right-of-ways and buffer strips with
9.9 million ha in rural areas, and 2.0 million
ha in urban areas (calculations based on
average municipal right-of-way as 50 feet,
reported in U.S. EPA, 1987; data from U.S.
DOT, 1985). The North-Central states have
4.2 million ha (10.3 million acres) in roads,
the South has 3.9 million ha, and the
Northeast, 1.1 million ha, all regions with
generally good site characteristics for tree
planting. If, for example, an additional 10%
of the 9.2 million acres of interstate, state,
and local highway corridors in these regions
were planted with trees, 0.9 million ha would
be available -- about 10% of the roughly 9
million ha in trees necessary to offset new
CO2 emissions from powerplants from 1987-
19% (see above). At average costs of
establishment and fertilization of $432/ha,
total costs would approach $390 million. If
20% of highway corridors were planted, 1.8
million ha (4.52 million acres) would be
produced, at a cost of $777 million.
Obstacles to planting highway corridors
include safety and visibility concerns of state
and federal departments of transportation,
establishment costs (which should, however,
be less than regular grass maintenance costs),
and existing regulations.
Option 7: Reforest Tropical Countries
Numerous estimates have been made
for tree planting desirable for economic,
social, and environmental reasons unrelated to
climate wanning. One authority concludes
that "at least 100 million hectares of tree
planting worldwide appears necessary to
restore and maintain the productivity of soil
and water resources," an area equivalent to
the size of Egypt (Postel and Heise, 1988).
Major tree-planting programs are being
promoted in many parts of the world, partly
in response to a 1985 international initiative,
the Tropical Forestry Action Plan (TFAP),
jointly sponsored by the Food and Agriculture
Organization (FAO), the United Nations
Development Programme (UNDP), The
World Bank, and World Resources Institute
(WRI) (see CHAPTER Vffl). In response to
TFAP, global funding for forestry by
multilateral development banks and bilateral
agencies is expected to rise from $600 million
in 1984 to $1 billion in 1988. In a parallel
effort, China doubled tree planting to 8
million hectares by 1985, and planted 3.3
million ha of seedlings in 1986 alone
(Houghton, 1988a, quoting FAO data),
although the survival rates initially hovered
around 30%. China has set a goal of 20%
forest cover by the year 2000 (up from 12.7%
forest in 1978) (Postel and Heise, 1988).
The carbon benefits achieved from
afforestation, which reduce emissions of CO2
to the atmosphere, are not likely to be
realized solely on the basis of slowing global
warming. Instead, social forestry projects
designed to integrate the provision of human
needs with economic incentives and
environmental stabilization, with carbon-
reduction goals piggybacked on top, provide
the most feasible approach.
V-140
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Chapter V: Technical Options
Forest plantation planting in the tropics
to date has focused on establishing
commercial hardwoods (722,000 ha/yr) (WRI
and IIED, 1988), and on providing fuelwood
(550,000 ha/yr) (Postel and Heise, 1988). The
gap between fuelwood supply and demand in
the rapidly expanding developing countries
could reach 1 billion m3 by the year 2000
(Marland, 1988). World Bank tallies suggest
that 55 million ha of high-yielding fuelwood
plantations will need to be established by
2000 to close this projected deficit -- fully 2.7
million ha/yr, or 5 times current fuelwood
rates. Thus, allowing for overlap, Postel and
Heise (1988) calculate that a total of about
110 million ha of planting is necessary both
to restore degraded lands and to provide fuel
requirements in 2000, which would sequester
approximately 0.7 Pg C/yr for the roughly 40-
year life of the forest.
Several crude estimates have explored
the possibility of very large reforestation
efforts in tropical regions to provide a sink
for fossil-fuel emissions. For example, Sedjo
and Solomon (1989) have proposed that the
current annual atmospheric net increase in
carbon (approximately 2.9 Pg C) could be
sequestered for about 30 years in
approximately 465 million ha of plantation
forests, at a cost possibly as low as S186
billion in the tropics or $372 billion in the
temperate zone, a large but not inconceivable
sum. This area would also produce as much
as 4.7 billion m3 of industrial wood annually,
three times the current annual harvest The
opportunity cost to society to offset carbon
production from global annual deforestation
of 11.4 million ha in the tropics can be
calculated from Sedjo and Solomon's
replacement cost figures and equals $400 per
hectare, or $4.6 billion per year, a sum the
world community should be willing to pay for
forest preservation in order to avoid paying
carbon offset replanting costs. Myers (1988)
has suggested that 300 million ha of
plantation eucalyptus or pine (a landmass the
size of Zaire), which absorbs about 10 t
C/ha/fyr, could offset the 2.9 Pg C
accumulating in the atmosphere annually (see
also Booth, 1988). Dyson and Marland
(1979) and Marland (1988) have suggested
that 700 million ha of land, an area about the
size of Australia or equal to the total global
forest cleared since agriculture began
(Matthews, 1983), in short-rotation American
sycamore, fixing carbon at a rate of 7.5 t/ha/yr
would be required to offset total global
production of 5 Pg C per year.
For all of these estimates some of the
highest growth rates observed on selected
sites have been assumed for vast tracts of land
characterized by very different site conditions.
Also, global reforestation estimates thus far
have focused on the potential for using forest
growth to completely offset total or net global
carbon emissions. New estimates are needed
that consider more feasible offset goals and
growth rates. More complete analyses, based
on better field estimates of carbon fixation
rates for a range of mixed-species stands and
agrosilvicultural systems, are underway to
identify available acreage with adequate soils
for potential planting programs in specific
countries, i.e., to generate inductive
assessments of the potential of this approach
rather than the deductive approaches utilized
thus far. Table 5-25 gives a summary of
preliminary estimates of forest acreage
required to of&et global CO2 emissions.
Is there adequate idle land to seriously
entertain the notion of massive tree planting?
Houghton (1988b) has roughly calculated for
tropical Asia and Africa the availability of
tropical land climatically and edaphically
suitable for forest growth (i.e., climate and
soils that previously supported forest). Crude
measures of land formerly in forest but
presently degraded or in pasture, and not in
use for crops or development, suggest that
about 100 million ha are available for
reforestation in South and Western Southeast
Asia (excluding arid lands in India and
Pakistan). For tropical Africa, ratios of land
once forested and land currently in "other
land" categories in FAO estimates (FAO,
1987) are less reliable, but create a range of
20-150 million ha available. Human-initiated
fires set to create and maintain savanna for
cattle grazing and other uses hypothetically
could be suppressed (although difficult to
manage in practice), potentially allowing
another 191 million ha of savanna to revert to
closed forest along the northern savanna and
hi Western Africa, thus providing an upper
limit of 340 million ha with potential for
reforestation (Houghton, 1988c; FAO/UNEP,
1981).
V-141
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Policy Options for Stabilizing Global Climate
Option 8: Restore Degraded Lands
Restoration of lands formerly forested
but degraded by anthropogenic practices such
as logging, overgrazing, swidden and
inappropriate agricultural methods could
increase reforestation and carbon fixation
rates. Forest fallow in swidden agriculture,
often with low volumes of standing biomass,
totals one billion ha globally, with another
one billion in some form of degradation.
Desertification (the reduction of biological
productivity, primarily from human activities,
usually in dry forests or rangelands) has
moderately or severely affected 1.98 billion ha
globally, especially in the African Sahel,
Southern Africa, Southern Asia, China and
Mongolia (IIED and WRI, 1987; OTA, 1984).
Sedjo and Solomon (1989) stress the low
purchase price of degraded lands, while
recognizing that low-productivity soils on
degraded sites are likely to greatly increase
acreage requirements for a given offset goal.
Grainger (1988) concluded that 758 million
ha of degraded tropical land, including the
203 million ha forested in the past, could be
restocked with forest.
The substitution of sustainable resource
use practices and active reforestation on these
lands can reduce further loss of woody
biomass and increase rates of carbon fixing
and fuelwood production. The price of
establishing plantations on degraded
grasslands in Indonesia has hovered around
S400 per hectare (JICA, 1986). For example,
Hough ton (1988b) estimates that by replacing
swidden cultivation with permanent, low-input
agriculture, about 365 million ha of fallow
land would be available for reforestation
during the period 1990-2015. Managed
reforestation of arid lands has been successful
in some sites where natural mulch or
commercial fertilizers were applied to
seedlings, and native species well-adapted to
local pest and environmental conditions were
planted. These lands were supplemented by
cautious use of fast-growth or nitrogen-fixing
leguminous exotic species, like Leucaena,
Pinus, Acacia, and Eucalyptus, which tend to
be more susceptible to pest invasions.
Research and field tests on leguminous trees
inoculated with Rhizobium fungi, which
produce nitrogen-fixing nodules on legume
roots, have shown that damaged tropical soils
depleted of essential mycorrhizal fungi can be
replanted effectively and inexpensively (less
than $0.01 per tree) (Janos, 1980).
Subtropical dry forests in the Western
Hemisphere have been reduced by 98%.
Botanist Daniel Janzen has organized an
ambitious plan to restore dry forest cut for
agriculture and to manage remaining habitat
fragments in order to expand Guanacaste
National Park in Costa Rica (Jansen,
1988a,b). The plan calls for establishing a
local and international environmental
educational and research program, suppressing
human fire activities, cattle ranching,
agricultural clearing, purchasing intact
remnant dry forest habitat adjacent to moist
forest tracts or protected areas to provide
seed sources, and developing a management
plan stressing species diversity and zoning for
habitat use, including provision of economic
opportunities. A closed-canopy dry forest
with significant representation of its previous
fauna is expected to evolve within 10-50 years.
This natural regeneration may sequester an
estimated 8.6 million t C, at a rough cost of
$11.8 million (Jansen, 1988c). Expansion of
this innovative approach throughout the dry
tropics may be feasible, if stable land tenure
and managed use can be attained.
In Nyabisindu, Rwanda, hillsides
denuded by intensive swidden agriculture
including rapid deforestation, soil erosion, and
overgrazing, are being restored to productivity
by strips of densely planted trees positioned
across steep slopes to catch soil and create
terraces for crops, and to produce fruit and
fuelwood. The restoration project stocks
these hedges from a tree nursery producing
five million seedlings per year for farm fruit
trees, shade trees lining roads, and hilltop
woodlots. A typical farm family can produce
25-50% more fuelwood than it consumes with
this mixed crop-tree system (Dover and
Talbot, 1987).
Option 9: Increase Soil Carbon Storage by
Leaving Slash After Harvest and Expanding
Agroforestry
Forest soils store about 1030-1630 Pg
of carbon, about twice the total amount of
carbon stored in terrestrial biomass, and fully
73% of the total carbon stored in soils (Olson
V-142
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Chapter V: Technical Options
et al., 1983; Bolin, 1983). The annual flux of
carbon into soils is 40-100% of the carbon
emitted by fossil-fuel combustion, but this flux
is offset by an equivalent release of carbon by
microbial activity and root respiration in soils
(Bolin, 1983; Johnson, 1989). Potentially, sofl
carbon storage pool size and residence time
could be increased through forest and land-
use management practices that recognized this
new objective.
Carbon enters soil via three main
methods: 1) deposition of biomass debris on
the surface, which is decomposed by
heterotrophic organisms into CO2 and
amorphous organic matter or humus that is
mixed or leached into the soil, 2) plant root
respiration releases carbon into soils, and root
biomass is roughly half carbon, and 3)
agroecosystems often employ the direct
introduction of plant residues into soils
during preplanting and post-harvest plowing.
Organic matter accumulation in soils is
inversely proportional to mean annual air
temperature. Prolonged waterlogging of soils
also facilitates storage of carbon in soils; both
low annual temperatures and waterlogging
prevent carbon volatilization (Johnson, 1989).
Changing agricultural and forestry
management practices to lengthen soil carbon
retention times offers one of the most
promising ways to store additional carbon.
Retention times range from lows on the order
of 4 years for equatorial forests, to 100 years
for tundra soils, and up to around 2,000 years
for peats, with a global mean time of 30-40
years (Oades, 1988). Alternative agricultural
practices like no-till and low-till, which
minimize soil disturbance due to plowing, are
being widely encouraged for conservation and
economic reasons (National Research Council,
1989). These practices could also reduce soil
carbon loss and facilitate carbon storage;
however, there has been little research on
low-input sustainable agriculture systems from
a greenhouse gas balance perspective.
For tropical agroecosystems, the soil-
agroforestry hypothesis has been stated by
Sanchez (1987) as follows: 'appropriate
agroforestry systems improve soil physical
properties, maintain soil organic matter, and
promote nutrient cycling.* This hypothesis is
currently the subject of a series of studies at
the International Council for Research in
Agroforestry in Nairobi and elsewhere. Field
work and simulations underway on changes in
soil carbon storage for an alley cropping
system in the Machokos District in Kenya
show that its introduction on degraded soils
leads to recovery of carbon storage averaging
100 kg/ha/tyr for the initial 20 years (see
Figure 5-14). Thereafter, annual net carbon
storage falls off asymptotically and after 108
years reaches zero, but averages 28 kg/ha/yr
for the entire 108-year period (Franz, 1989).
The Southeastern U.S. lost huge quanti-
ties of soil carbon from 1750 to 1950 due to
conversion of forest to agriculture (Delcourt
and Harris, 1980), although reforestation from
natural regeneration of forest and commercial
plantations has reversed that trend over the
past 30 years (Schiffman and Johnson, 1989).
Natural regeneration on old fields increased
carbon storage over 50-70 years by 235%,
from 55,000 to 185,000 kg/ha, including a
10% increase in soil carbon. Soil carbon
storage in surface soils of old field plantations
and natural forests has been found to be
double that of adjacent croplands, totalling
10.4-12.9 t C/ha (Schiffman and Johnson,
1989). Hence, widespread reforestation of
surplus crop and pasture lands has the added
advantage of increasing soil carbon storage
significantly.
Forest harvest practices could be
altered to increase the storage of soil carbon
by leaving more slash on the ground after
cutting, allowing slow decay and more
incorporation of biomass into soils instead of
burning slash, which adds a sudden flux of
carbon to the atmosphere. The amount of
slash burned might be minimized, and the
period between burns of slash might be
lengthened as well. Harvest techniques and
equipment that minimize disturbance and
degradation of soil organic matter could be
introduced, especially on steep terrain and
during rainy seasons. Timber selection
systems, rather than clearcut methods, would
leave more standing biomass to absorb rainfall
and reduce erosion and soil carbon
volatilization. Similarly, even-age
management techniques that utilize harvest of
virtually all trees in a stand because they are
ready for harvest simultaneously could be
replaced by all-age management.
V-143
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Policy Options for Stabilizing Global Climate
FIGURE 5-14
ALLEY CROPPING IN MACHAKOS, KENYA
Leucoeno/moize and beans 50/50
in
«*
c
a
-100
D Carbon Benefit
Time since initiation (years)
Cum. Carbon o Revenue Benefit
Source: Franz, 1989.
V-144
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Chapter V: Technical Options
Obstacles to Large-Scale Reforestation in
Industrialized Countries
Economic and institutional obstacles to
widespread reforestation center on the high
costs of site preparation, planting, forest
management, and necessary financial
incentives to private landowners. However,
1.2 million ha of trees were planted in 1987
without strong incentives (USFS, 1988). U.S.
state foresters maintain that financial
incentives on the order of $125-250/ha ($50-
100/acre) would be sufficient to bolster
reforestation of harvested woodland and
surplus croplands in most states. With about
three years of lead time, existing tree
nurseries could accelerate production of
seedlings enough to plant 3-10 times current
acreage per year (NASF, 1988).
Ecological drawbacks to massive
reforestation schemes include the low levels
of genetic variability that characterize vast
tracts of monocultural stands and their
reduced resistance to pest infestations (e.g.,
gypsy moth, pine bark beetles), which can
lead to widespread forest decline and
mortality. Large-scale plantations may strain
surfacewater and ground water resources in
areas already experiencing overdrafts of and
escalating demand on aquifers, for example,
the Ogallala aquifer in the southern Great
Plains, and Southeast coastal plain ground
water (Los Alamos National Laboratory,
1987).
Air pollution, such as acid
precipitation, ozone, and other photochemical
oxidants, is already affecting the health of
forests in the U.S., Europe (e.g., see
Kairiukstis et aL, 1987; UNECE/FAO, 1989),
and China. Since 1979 there has been
documented decline in at least seven
important coniferous and four important
broadleaf species in European forests, and in
at least eight important species in North
American forests. Fifty-two percent of West
German and 36% of Swiss forests were in
decline by 1986. In the Southeast US.,
natural-stand diameter growth rates for yellow
and loblolly pines have declined 30-50% in
the past 30 years (WRI and IIED, 1986; IIED
and WRI, 1987).
Air pollution impacts may be
exacerbated by the combined effect of
wanning due to climate change and increased
ultraviolet radiation due to ozone depletion.
The long-term process of climate change is
likely to complicate the task of actively
expanding net forest area, a topic explored in
Smith and Tirpak (1989). The increase of
carbon dioxide, through the effect of CO2
fertilization, may spur tree growth rates, but
the net result of climate change on forest
growth under changing temperature and preci-
pitation conditions is difficult to predict.
Early studies suggest that Southern bottom-
lands hardwood, oak, and pine forests, and
Northern conifer forests are likely to advance
northward as temperatures increase. The
natural rate of forest migration ~ about 100
to perhaps 400 km per 1000 years - appears
unlikely to keep up with the likely rate of
forest decline (Davis and Zabinski, in press;
Shands and Hoffman, 1987; Smith and Tirpak,
1989). Technical methods of speeding seed
dispersal to favorable soils (e.g., seeding from
aircraft) are not complex but may be costly,
with potentially low seedling survival rates
(WWF, no date).
Forests under the stress of climate
change may have difficulty maintaining
current productivity rates, let alone increased
rates and expanded geographic range, as
envisioned under reforestation policies.
Forests migrating north in response to rising
temperatures will tend to encounter poorer
soils, slow natural seed dispersal methods,
stresses on ecosystems, competition from
other land use sectors and ecosystems also
responding to climate change, and either
reduced or increased precipitation and water
supply conditions, depending on the region.
While global boreal forests are likely to
increase in total area and tree density
(Shugart and Urban, no date), they probably
will contain, on average, lower standing
biomass volumes and carbon fixation rates
than current boreal forests. Sedjo and
Solomon (1989) estimate a net loss of 24 Pg
C storage in global forests under a 2xCO2
scenario (doubling of pre-industrialized CO2
concentration levels), largely due to declines
in total biomass in boreal forests.
V-145
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Policy Options for Stabilizing Global Climate
Forest decline presents a major obstacle
to forest management to mitigate climate
change in all forest zones (i.e., reports of
decline are emerging in the subtropics and
tropics). According to one source, decline is
"a complex disease caused by the interaction
of a number of interchangeable, specifically
ordered abiotic and biotic factors to produce
a gradual general deterioration, often ending
in the death of trees" (Manion, 1981, in
Auclair, 1987). Significant modelling of stress
and decline have taken place (e.g., Kairiukstis
et al., 1987), and may have potential for
application to climate stress on forest and
tree growth and regeneration, migration of
forests, and afforestation. "In large areas, the
silvicultural regimes are at least partly
increasing the forest damages" (Kuusela,
1987).
Aggressive silvicultural and management
responses to decline may offset losses and
facilitate evaluation of mitigation options for
climate change under intensifying conditions
of air pollution. Responses include increasing
diversity of stands; thinning younger stands to
maximize tree vitality (Rykowski, 1987);
keeping stands densely planted in order to
avoid physiological wind damage observed in
stand borders and to provide a selection
reserve for further thinning; and applying
fertilizers to stands liable to pollution stress
and decline, as practiced in Duben-Forest and
Lower Lusatia pine stands on nutrient-poor
soils in Eastern Europe, while avoiding over-
fertilization that leads to growth depressions
(Thomasius, 1987).
Climate change, therefore, may affect
the viability of reforestation strategies as a
mitigation measure. Further research is
needed.
Obstacles to Reforestation in Developing
Countries
Tropical reforestation schemes face
many obstacles. Pest management in
monocultural plantations (e.g., rats, fungus,
nematodes for Leucaena in the Philippines)
and loss of genetic diversity, which might
allow adaptation to pest or viral infestations,
have proved major deterrents to large-scale
plantation projects in the Philippines, at Jari,
Brazil, and elsewhere. Other issues include
rapid removal of soil nutrients by fast-growth
species, reduced growth rates at altitudes as
low as 450 meters and in frost belts for some
species, and sheet erosion. Practical
limitations of plantations include the large
areas of land necessary, limited transportation
infrastructure to move biomass to users,
plantation security (fencing to prevent
poaching of trees in northern Nigeria in 1976
costs $160-200 per ha), costs of establishment,
and limited availability of skilled technicians
(Villavicencio, 1983).
Pastures cut from tropical forests have
been invaded by resilient monocultural grasses
like Imperata cylindrica, which must be
suppressed before trees can survive. Research
into recolonization of large, highly degraded
pastures in the Amazon (Uhl, 1988) suggests
that three factors inhibit reforestation: few
seeds of forest species are being dispersed
into pastures because 85% of tree seeds are
transported by animal pollinators that do not
frequent pastures; most seeds dispersed to
pastures are eaten by predators; and moisture
and energy conditions near the ground surface
in pastures are radically different from forest
conditions.
Economic and population pressures in
many regions make net afforestation difficult
to achieve. China, for example, is
experiencing rapid economic development,
which has led to housing construction that
consumed 195 million cubic meters of wood
(0.05 Pg C) between 1981 and 1985,
equivalent to the total annual growth of all
China's forests (Postel and Heise, 1988).
Cost estimates for plantation establishment in
the tropics (80% of costs are for labor) are
summarized in Table 5-26. These costs range
from about $100-200/ha/yr for dry areas with
less than 1100 millimeters (mm) of rainfall
per year, to over SlOOO/ha/yr in wetter areas
receiving over 1800 mm/yr (FAO, 1989).
Other environmental stresses on extant
forests, including seasonal climatic variations
and human-induced stresses, reduce the ability
of forests to meet current and projected
demand for forest products, let alone supply
new large increases in productivity and
plantation acreage. Persistent drought already
plays a prominent role in the migration of
environmental refugees from traditional
V-146
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Chapter V: Technical Options
TABLE 5-26
Costs of Afforestation: Stand Establishment and Initial Maintenance
(per hectare basis)
Rainfall
(mm) Species
1. PLANTATION (approximately 80%
<500 Acacia tortilis, Albizia
lebbeck, Prosopis
cineraria, Prosopis
juliflora
500-1,100 Leucaena leucocephala
1,200-1,800 Tropical pines
Teak, Gmelina, Khaya,
Eucalypts
Some species, but with
Taungya system
Bamboo
Enrichment planting,
various species
> 1,800 Eucalypts
Okoume
Gmelina
Eucalypts
Schizottobiwn parahybum;
Condia alliodora
2. DIRECT SOWING
By hand, spot sowing
By air, pelletized seed
Number
of
Country Plants
of costs are labor)
India 400
India 1,000
India 1,000
Honduras 1,600
Madagascar 2,000
Zambia
Zambia
Burkina Faso 2,500
Senegal 2,500
Togo 2,500
Benin 1,600
Cote d'lvoire
Cote d'lvoire
Togo
India
Madagascar
Zaire 250
400
Zaire 4,500
Congo 950
Gabon 400
Brazil
Gambia
Brazil
Gambia
Ecuador 2,000
Honduras, 1980
India, 1986 (trials)
Cost
(year S)
100 US$ (78)
200 USS (78)
200 USS (78)
400 USS (84)
15,000 CFA (71)
238 USS (78)
228 USS (78)
955 USS (79)
600 USS (79)
1,700 USS (79)
1,200 USS (79)
640 USS (88)
50 USS
15-50 USS
Man-Day
160
320
320
50
100
N/A
N/A
255-330
345
185
250
145-210
100-150
145
150
260
80
124
468
80
264
N/A
N/A
N/A
N/A
150
Source: FAO, 1989.
V-147
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Policy Options for Stabilizing Global Climate
agricultural areas such as the Sahel, forcing
relocation to areas of marginal dry forest that
introduces new pressures (Houghton, 1988a;
Postel and Heise, 1988).
Comparison of Selected Forestry Technical
Control Options
Slowing tropical deforestation, and
rapidly expanding temperate and tropical
reforestation, may offer two of the most cost-
effective policy responses to increasing CO2
emissions. However, only rudimentary
estimates of the feasibility, costs, and
consequences of large-scale reforestation have
been performed. Table 5-27 summarizes
these options. All calculations are
preliminary estimates of planting costs only.
Total costs of these measures are not
estimated, and would vary greatly depending
on land costs and management costs. These
estimates are provided to give a general sense
of the relative costs of these options. Few
viable, global-scale plans to slow forest loss in
the tropics have been advanced. Most are
policy options rather than technical fixes, and
these are discussed in Chapters VII and VIII.
Replacement of swidden agriculture with
permanent low-input, sustainable agricultural
systems offers particular promise.
Integrated natural resource management
and social forestry projects such as provision
of the full spectrum of forest and food
products in demand; forest protection from
swidden agriculture, logging, and fire;
economic opportunities and reasonable rates
of return; and cooperative management by
local people and resource professionals are
likely to be the most successful in addressing
climate change effects and offset goals.
Examples of three such projects are displayed
in Table 5-28. These projects were proposed
to offset the lifetime CO2 emissions of a 180
MW coal-fired electric plant planned by
Applied Energy Services in Uncasville,
Connecticut, by planting and managing
forests, or protecting former forest converted
into pasture to allow natural regeneration
into secondary forest (to be protected in a
national park in Guanacaste, Costa Rica
[Jansen, 1988c]).
Obstacles to slowing deforestation and
to planting and maintaining reforested lands
in the tropics include degraded soils, limited
research on appropriate species and systems,
limitations in institutional capabilities,
government incentives that hasten
deforestation, and soaring population growth
rates.
V-148
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Chapter V: Technical Options
TABLE 5-27
Comparison of Selected Forest Sector Control Options: Preliminary Estimates
Option
No. ha
Required
(million)
Planting
Cost/ha
($)
Total
Planting Cost
(million $)
Fixation
Rate
(t C/ha)
Carbon
Offset Goal
(Pg C/Sequestered)
Planting
Cost Per
Pg C
(billion $)
Plant trees to offset
annual CO2 emissions U.S.
Plant 100 million
urban trees
Reforest 20% of
highway corridors
Plant trees to
offset new U.S. electric
plant C02 (1987-%)
Implement current forest
economic opportunities at
4%ROR
Plant tree* to offset
new U.S. electric plant
CO2 (1987-96) in LDCs
Plant trees in Guatemala
to offset CO2 emissions of
180 MW electric plant in U.S.
240.0
0.0
1.8
9.1
58.3
6.0
0.1
DOMESTIC U.S. OPTIONS
432 104,000 5
100 5
432
432
778
3,930
INTERNATIONAL FORESTRY OPTIONS (TROPICS)
400 2,400 7.5
14'
1.2 Pg C/yr
0.052 Pg C/yr
0.009 Pg C/yr
0.045 Pg C/yr
0.164 Pg C/yr
0.045 Pg C/yr
0.16 Pg C total over
40-year period
10
0.2
10
10
0.9
V-149
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Policy Options for Stabilizing Global Climate
Substitute sustainable
agriculture for all
swidden agriculture
Restore degraded lands
and provide fuelwood
for year 2000 and reduce
tropical C release by 40%
Reforest tropical lands
to offset global annual
net increase in C
Replant tropical forest
cut or burned each year
TABLE 5-27 (continued)
Comparison of Selected Forest Sector Control Options: Preliminary Estimates
Option
No. ha
Required
(million)
Planting
Cost/ha
($)
Total
Planting Cost
(million $)
Fixation
Rate
(t C/ha)
Carbon
Offeet Goal
(Pg C/Sequestered)
Planting
Cost Per
PgC
(billion $)
41
110
465
11.3/yr
400
400
400
44,000
186,000
4500/yr
7.5
6.2
0.7 Pg C/yr
over 40 yrs.
2.9 Pg C/yr
1.0 Pg C/yr
4.5
* Total project cost, including forest protection, plantation establishment, and agroforestry.
Note: All calculations made from estimates and references listed in this section; and all calculations are preliminary estimates of planting costs only, without management, harvest,
rental or purchase costs included.
V-1SO
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Chapter V: Technical Options
TABLE 5-28
Overview of Three Social Forestry Projects Proposed to
Offset CO2 Emissions of a 180-MW Electric Plant in Connecticut
Forest Attribute CARE/WRI/Guatemala WWF/Costa Rica Guancaste/Costa Rica
Total area of project
Protected in forest reserves
Logged or managed forests
Newly established woodlots
101,000 ha
19,740 ha
38,000 ha
13,140 ha
122,000 ha
72,000 ha
12,000 ha
70,400 ha
70,400 ha
(plantations)
Agroforestry lands
Carbon sequestered
over 40-year life of plant
68350 ha
18.1 Tg C
Cost estimate (cash or in-kind) $14 million
Cost per ton C sequestered $0.77
11.0 Tg C
$9.6 million
$0.87
8.6 Tg C
$11.8 million
$1.37
Note: Offset goal = 0.39 Tg C/yi.
Sources: Turner and Andrasko, 1989 (all projects); Trexler et aL, 1989 (Guatemala); WWF, 1988
(Costa Rica); Jansen, 1988c (Guanacaste).
V-151
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Policy Options for Stabilizing Global Climate
PART FIVE: AGRICULTURE
Agriculture contributes to the emissions
of greenhouse gases through several means:
rice cultivation, nitrogenous fertilizer use,
enteric fermentation in domestic animals, and
decomposition of animal manure. Estimates
place the annual contribution of rice
cultivation and domestic animals at
approximately 20 and 15%, respectively, of
global methane (CH4) production. The use
of nitrogenous fertilizers is estimated to
account for between 1 and 17% of the current
global source of nitrous oxide (N2O) (see
CHAPTER II). Land clearing for agriculture,
and the intentional burning of agricultural
wastes, grasslands, and forests make a
significant contribution to the global
emissions of carbon dioxide (CO2), CH4, and
N2O, as well as carbon monoxide (CO) and
nitrogen oxide (NOX). Also, energy use in
agriculture is significant, particularly in
developed countries, where the requirements
for irrigation, field operations and agro-
chemicals are high. Figure 5-15 illustrates the
net effect of these agricultural sources on
current greenhouse warming.
Both the magnitude of agricultural
source emissions and the potential
effectiveness and costs of possible reduction
measures are very uncertain. While
considerable research has been done on the
agricultural activities of interest, relatively
little attention has been focused on
agriculture-related emissions of greenhouse
gases and how various changes in agricultural
practices affect these emissions. Many field-
level measurements across a wide range of
cropping situations, in addition to whole
systems evaluation (across the range of
greenhouse gases), will be required in order
to develop a rational control strategy.
For each of the three major trace-gas-
producing agricultural practices, we discuss
existing technologies and management
practices, emerging technologies, and areas
that require additional research. Technical
options for reducing greenhouse gas emissions
are discussed under each of these subsections.
RICE CULTIVATION
Methane is produced by anaerobic
decomposition in flooded rice fields. Some
CH4 reaches the atmosphere through
ebullition (bubbling up through the water
column), but most of it (about 95%) passes
through the rice plants themselves, which act
as conduits. Methane production is affected
by the particular growth phase of the rice
plant, temperature, irrigation practice,
fertilizer usage, amount of organic matter
present, rice species under cultivation, and
number and duration of rice harvests (Fung et
al., 1988). A limited number of
measurements have been performed in
California, Italy, and Spain to evaluate CH4
production in flooded rice fields. No
measurements have been published for the
major rice-producing areas of Asia, however,
where environmental conditions and
cultivation practices differ significantly from
those in these more temperate regions
(Cicerone and Shelter, 1981). This data
limitation makes it difficult to evaluate
emissions and potential greenhouse gas
reductions strategies for Asia. Measurements
of CH4 from rice are currently being
performed in China and Japan.
Rice cultivation is currently estimated
to contribute between 60 and 170 Tg CH4 per
year (Fung et al., 1988), and with rice-
harvested area increasing between 0.5 and
1.0% per year (IRRI, 1986), rice cultivation
will continue to be a significant source 'of
CH4 emissions.
Rice cultivation practices around the
globe vary widely. With over 60,000 varieties
of rice, there is great variation in water
requirements, fertilizer response, pest and
disease resistance, growing season, plant
height, and yield potential. Traditional rice
varieties are generally tall plants with a low
grain-to-straw ratio that have a good
resistance to endemic weeds and pests and a
high tolerance for moisture, including
flooded monsoon conditions. Cultivation of
V-152
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Chapter V: Technical Options
FIGURE 5-15
CONTRIBUTION OF AGRICULTURAL PRACTICES
TO GLOBAL WARMING
CFC-12(10%)
Energy Use
and Production
(57%)
CFC-11 (4%)
Other CFCs (3%)
Other Industrial (3%)
Agricultural
Practices
(15%)
Land Use
Modification
(8%)
V-153
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Policy Options for Stabilizing Global Climate
traditional varieties of rice does not involve
heavy fertilization because these plants tend
to lodge (fall over) at high levels of
fertilization. The highest most stable rice
yields are achieved with irrigation.
Research of the 1960s led to the Green
Revolution, which radically changed the
nature of rice production in Asia. This
research produced a high-yielding rice cultivar
that is short, stiff-stemmed, and very fertilizer
responsive. These modern, high-yielding
varieties also have a short growing time,
which allows for multiple plantings during the
year. The first of these modern varieties, IRS,
established a maximum yield potential of 10
million tons per hectare (mt/ha) under ideal
conditions, and reduced the average growing
time from 160 to 130 days (Barker et al.,
1985).
Existing Technologies and Management
Practices Affecting Methane Production
No currently-available technology can
inhibit the production of CH4 in rice paddies,
but cultivation practices and plant variety
affect the amount of CH4 produced.
Nature of Rice Production System
The nature of the rice production
system has a substantial effect on the amount
of CH4 produced. Wet paddy rice produces
CH4, while dry upland rice does not.
Wetland rice comprises about 87% of rice
area worldwide. Of global rice area, about
53% is irrigated, 22.6% is shallow rainfed,
8.2% is deepwater, and 3.4% is tidal wetland.
The remaining 13% is dry upland rice
(Dalrymple, 1986). The majority of upland
rice area is in Africa and Latin America.
Rice paddies are inundated to varying depths
and for different lengths of time depending on
production system used, which affects the rate
of CH4 generation. How these rates differ
has yet to be quantified.
Fertilization With Organic Matter
The kind and volume of organic matter
added to the rice paddy has been shown to
affect CH4 production. Laboratory
experiments have shown that adding organic
matter leads to an early peak in CH4
production and an overall increase equivalent
to 2-5% of the added organic matter
(Delwiche, 1988).
Organic fertilizers are often used in rice
cultivation in Asia. Sources include animal
manures, composted garbage, night soil
(human feces), and plant residues. After
harvest, rice plant residue is often
incorporated into the soil as a source of
organic material - a practice that appears to
increase CH4 emissions significantly. In
addition, it is not known whether and to what
extent the introduction of manure from
domestic animals during plowing and
harrowing affects CH4 production.
Disposition of Crop Residues
Crop residues can be burnt, buried,
incorporated into the rice paddy, or used for
some other activity. Burning the residue
releases CO2. Buried residue partially
decomposes and produces CH4, but less than
the amount produced by incorporating the
residue into the paddy.
In southern India and Sri Lanka, there
is a preference for intermediate height
varieties of rice, which produce more straw
for fodder and fuel (Barker et al., 1985).
Finding additional uses for rice straw, such as
for fiber or building materials, is necessary in
order to reduce the incentive for plowing crop
residue back into the field.
T}pe of Rice Variety Planted
The shift to high-yield varieties of rice
has helped to reduce the amount of CH4
produced per unit of rice. Modern, short-
stemmed varieties have a grain-to-straw ratio
that is about 50% higher than traditional
varieties, which means less organic material
(straw) is left to decompose, assuming it is
not burned. In addition, the shorter growing
season of high-yield varieties results in a
reduction in CH4 emissions. However, the
shorter growing season also allows multiple
plantings during the course of a year.
Overall, CH4 emissions could increase as a
result of multiple planting, particularly if
more organic material is incorporated into the
paddies to support the greater number of
plantings.
V-154
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Chapter V: Technical Options
High-yield varieties of rice are largely
limited to irrigated areas where yield response
is the highest. These modern varieties show
the highest fertilizer response and overall
yield in irrigated areas during the dry season,
when water levels are best controlled and
solar energy is at its peak. The yield
response is lower and highly variable under
the summer monsoon conditions when
flooding, pests, and diseases are most
common. Some farmers in India and
Bangladesh cultivate modern varieties in the
dry season and traditional varieties in the wet
season (Barker et al.( 1985).
The uncertainty of adequate moisture in
many areas, and flooded conditions in others,
discourages the use of modern fertilizer-
responsive varieties in non-irrigated
production regimes. But, in some countries,
the use of modern varieties has expanded well
beyond the irrigated zones. In the
Philippines, modern varieties are grown
extensively in rainfed lowlands. In Burma,
modern deepwater and upland varieties now
cover an area three times that which is
irrigated (Dalrymple, 1986; see Table 5-29).
Further dissemination of the short, stiff-
stemmed, fertilizer-responsive modern
varieties of rice has potential for decreasing
emissions of methane. World rice yield is
currently at about one-half of genetic
potential, which is as much as 14-16 mt/ha
(Mikkelsen, 1988). There is considerable
room for efficiency improvements in rice
production, which would lead to a relative
decrease in CH4 production.
Fertilizer Use
Widespread adoption of modern
varieties has been somewhat impeded in
developing countries because of the capital
required for new seed and fertilizer.
Switching to modern varieties has resulted in
an increase in the use of both organic and
chemical fertilizers. Research indicates that a
significant increase in production could be
achieved through more efficient application of
chemical fertilizer. Asia currently has a
fertilizer-use efficiency of between 30 and
40%. Direct placement of fertilizer into the
soil when rice is transplanted could double
fertilizer-use efficiency and would increase
yield (Mikkelsen, 1988).
The use of chemical rather than organic
fertilizer may, at least temporarily, reduce
CH4 production in the rice paddy. The
interaction of such soil amendments on CH4
production and rice yield needs to be
thoroughly examined.
Fertilizer use on rice is a significant
source of N2O. Intermittent flooding and
drying of the paddy results in a high rate of
N2O evolution through denitrification
(Eriksen et al., 1985). Methane control
strategies for rice must also consider the
effect on N2O evolution (see
NITROGENOUS FERTILIZER USE AND
SOIL EMISSIONS).
Emerging Technologies
Current research at the International
Rice Research Institute (IRRI) and other rice
research centers is focused on the
development of varieties better suited to a
wide range of environmental conditions
(Dalrymple, 1986). The development of high-
yield varieties that can withstand the drought
conditions of upland and shallow rainfed
systems, as well as the flooded conditions
associated with lowland and tidal rice
cultivation, would increase the dissemination
of high-yielding varieties in these areas.
Greater emphasis is being placed on
efforts to understand the complexities of the
farming system by conducting research in
farmers' fields and encouraging farmer
involvement. This so-called farming-systems
style of research combines the knowledge of
researchers with the direct experience of
farmers (Barker et al., 1985). Research that
focuses on developing cultivars that
consistently produce a good yield under a
wide range of conditions, rather than a high
yield under ideal conditions, holds the most
promise for improving food supply stability
and decreasing CH4 emissions from rice
cultivation in Asia.
There are likely to be further shifts to
irrigated rice production in the future.
However, improving the potential of modern
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TABLE 5-29
Water Regime and Modern Variety Adoption for
Rice Production in Selected Asian Countries
Percent Rice Area by Water Regime
Country
Bangladesh
Burma
China (a)
India
Indonesia
Korea Rep
Malaysia
Nepal
Pakistan
Philippines
Sri Lanka
Thailand
Total Rice
Area
(000 ha)
10190
4751
34286
39515
8913
1229
680
1261
1999
3535
818
8679
Irrigated
Season
Dry Wet
10
2
(b)
7
30
(b)
29
-
.
17
27
6
2
15
95
32
51
100
29
23
100
26
40
14
Shallow
(0-30 cm)
42
43
S
28
6
-
29
54
-
34
27
53
Rainfed
Deep Water
(30-100 cm)
26
21
(c)
12
3
-
-
15
.
11
-
12
Floating
(>100 cm)
11
4
-
6
2
-
-
4
-
-
-
4
Dryland
9
15
-
15
8
-
13
4
-
12
6
11
Percentage Cropped
in Modem Varieties
25
53
20 (d)
53
64 (d)
34
44
36 (d)
46
85
89
13
a Allocations based on impressions rather than data.
b All rice grown during the summer months and shown under wet season.
c A dash (-) indicates magnitude zero.
d Number of MV adoption in disagreement with "Development and Spread of High-Yielding Rice Varieties in Developing Countries." U.S. AID numbers:
for China - 91%; Indonesia - 82%; Nepal - 53%.
Source: IRRI, 1986.
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Chapter V: Technical Options
varieties to perform well under rainfed
conditions would reduce the incentive to shift
to irrigated production systems, which are
large producers of CH4.
Research Needs and Economic Considerations
Before a comprehensive strategy to
reduce CH4 production in rice can be
developed, research in several areas is needed.
There is a need for experiments in Asia,
where the majority of the world's rice is
grown, and no data is currently available. In
particular, to estimate the amount of CH4
produced per unit of rice we need to quantify
the amount of CH4 produced from different
cultivars, under various cultivation practices,
particularly under different water management
regimes. Additionally, the effect of adding
chemical rather than organic fertilizer on CH4
production needs to be further examined and
quantified.
The increased temperatures and changes
in precipitation patterns associated with
climate change could have major implications
for global rice cultivation. Particularly in the
tropics, heat stress could present a problem
for rice, where high temperatures could
increase sterility, impair growth, and decrease
yield (IRRI, 1981). Increased temperatures
could also increase microbial activity and CH4
production within the rice paddy. Such
feedbacks need to be examined.
Rice is the cornerstone of the Asian
economy. Economic and cultural considera-
tions must be at the root of any CH4 control
strategy. The sheer number of small-scale
rice farmers in Asia will make implementation
of a control strategy difficult. Practices that
are low-cost, beneficial, and attractive to small
farmers will need to be identified and
disseminated through existing and expanded
agricultural research networks.
Many Asian countries are striving for
self-sufficiency and have protected internal
markets against the price fluctuations of the
international market. Some countries have
initiated price floors and others price ceilings.
Price supports in countries such as the U.S.
and Japan cause an increase in the production
of rice.
NITROGENOUS FERTILIZER USE AND
SOIL EMISSIONS
Denitrification and nitrification are the
primary processes that lead to the evolution
of N2O from soils fertilized with nitrogenous
fertilizers. In well-aerated soils, nitrification
is the primary process producing N2O
(Breitenbeck et al., 1980). Denitrification is
prevalent in poorly drained, wet soils. Rice
cultivation is the largest agricultural
contributor to denitrification losses (Hauck,
1988). Soil erosion and leaching of fertilizer
into ground water and surface water is an
additional source of N2O: between 5 and
30% of fertilizer leaves the soil system via
leaching or runoff (Breitenbeck, 1988).
Researchers need to derive a more precise
estimate of N2O from this source.
Fertilizer-derived emissions of N2O are
estimated to be 0.14-2.4 teragrams of nitrogen
(Tg N) annually (Fung et al., 1988), based on
global consumption of 70.5 Tg of nitrogenous
fertilizer in 1984/1985 (FAO, 1987).
Nitrogenous fertilizer .use is increasing at an
estimated 1.3% per year in industrialized
countries and 4.1% per year in developing
countries (World Bank, 1988). By 2050,
global fertilizer consumption is estimated to
increase by a factor of 3.5 over the 1990 level
(Frohberg et al., 1988).
Anthropogenic factors affecting the
fertilizer-derived emissions of N2O include the
type and amount of fertilizer applied,
application technique, timing of application,
tillage practices, use of chemicals, irrigation
practices, vegetation type, and residual
nitrogen in the soil. Natural factors such as
temperature, precipitation, organic matter
content, and pH of soil also affect N2O
emissions (Fung, 1988).
N2O emissions are difficult to estimate
because of the complexity and variability of
fertilized soil systems. Estimates suggest that
fertilizer-derived emissions of N2O are highest
for anhydrous ammonia (between 1 and 5%
of N applied), followed by urea (0.5% of N
applied), ammonium nitrate, ammonium
sulfate, and ammonium phosphate (0.1% of N
applied), and nitrogen solutions (0.05% of N
applied) (Fung, 1988). Anhydrous ammonia
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Policy Options for Stabilizing Global Climate
is only used extensively in the United States,
where it comprises about 38% of nitrogenous
fertilizer consumption. Urea is used
extensively in Asia and South America, where
it accounts for 69% and 58%, respectively, of
nitrogenous fertilizer consumption.
Existing Technologies and Management
Practices Affecting Production of Nitrous
Oxide
The wide variety of agricultural systems
and fertilizer management practices produces
very different quantities of N2O emissions.
These emissions can be reduced by improving
the efficiency of fertilizer use, which can be
achieved through changes in management,
such as better placement in the soil, or in
technology, for example, introducing
nitrification inhibitors and fertilizer coatings,
which both improve the efficiency of fertilizer
applied and reduce the amount required.
Adoption of more efficient fertilizer
management practices and technologies by
farmers has been slow, however, particularly
in developing countries. Traditional
agricultural practices have proven to be
difficult to dislodge. Immediate benefits of
alternative practices must be made apparent
or incentives provided in order to achieve
widespread adoption of these more efficient
practices and technologies.
Type of Fertilizer
Nitrous oxide emissions vary by one to
two orders of magnitude between nitrogen
solutions, urea, and anhydrous ammonia. The
feasibility of using fertilizers with lower N2O
emission rates for different cropping
situations needs to be examined and
encouraged.
Fertilizer Application Rate
Typical fertilizer application rates vary
depending upon crop type, soil conditions,
fertilizer pricing, and environmental policies.
Fertilizer application is often in excess of
crop and soil requirements. Increased
fertilizer application results in increased
emissions of N2O. Adjusting fertilizer
application in accordance with plant
requirements would improve fertilizer-use
efficiency. Currently, fertilizer subsidies and
pricing encourage a higher than optimum
level of fertilizer use.
Efforts to provide adequate nutrition to
crops continue to be hindered by inadequate
understanding and forecasting of factors that
influence nutrient storage, cycling,
accessibility, uptake, and use by crops during
the growing season. Testing of soil and plant
tissues could allow fanners to apply nutrients
more in accordance with crop requirements,
rather than following broad guidelines that
often recommend excessive fertilization.
Crop Type
Fertilizer application rates vary widely
by crop type. For example, in the U.S. in
1985, average fertilizer application rates (in Ib
N per acre) were 134 for com, 64 for wheat,
and less than 20 for soybeans (NRC, 1989).
Within the U.S., corn alone accounts for 44%
of all directly applied fertilizers in agriculture,
while wheat, cotton and soybeans receive 18%
combined (NRC, 1989).
Corn, being a row crop, is susceptible
to high rates of soil erosion, increasing the
potential nitrogen losses. After the harvest of
corn, substantial amounts of nitrogen
generally remain in the soil, available for
evolution as N2O. The surplus nitrogen can
be captured by inter-cropping with a grain
crop such as rye, which could then be plowed
back into the soil (see Alternative
Agricultural Systems).
Overall, N2O emissions could be
reduced through less cultivation of crops with
high fertilizer requirements. Within the U.S.,
reducing price supports for corn, or zoning
against row crops in high credibility areas or
in nitrate-contaminated watersheds could
achieve this goal.
Timing of Fertilizer Application
The timing of fertilizer application is
likely to affect the evolution of N2O from the
soil. Limited studies on the subject suggest
that emissions from fertilizer applied in the
foil exceed those from fertilizer applied in the
spring (Bremner et al., 1981).
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Chapter V: Technical Options
Placement of Fertilizer
Proper (deep) placement of fertilizer
can improve fertilizer efficiency by curbing
nitrogen losses and thus N2O emissions.
Broadcasting and hand placement of fertilizer
results in higher nitrogen losses than does
deep placement. Deep placement is
particularly important in flooded fields where
fertilizer is used inefficiently. In Asia, only
about one-third of the nitrogen applied
benefits rice crops. Placement of fertilizer
into the reduced zone, which prevents
microbial action, can double fertilizer-use
efficiency (Stangel, 1988). This technique
improves efficiency regardless of the water
regime (Eriksen et al., 1985).
Rice can either be grown from seeds or
transplanted. Transplanted rice may reduce
denitrification losses by allowing more
efficient fertilizer application. A simple tool
that allows for proper fertilizer placement at
the time of transplanting greatly improves
fertilizer efficiency, however, this tool has not
been widely adopted in Asia (Stangel, 1988).
Rice farms in Asia average 3 ha or less and
are very labor-intensive operations.
Consequently, there has been little incentive
to develop and disseminate fertilizer
technology.
Water Management
Intermittent flooding of rice paddies
increases nitrogen loss and the creation of
N2O (Eriksen et al, 1985; Olmeda and
Abruna, 1986). In paddy rice, the trade-off
between CH4 and N2O production must be
evaluated.
Tillage Practices and Herbicide Use
A few preliminary measurements
suggest that denitrification activity and N2O
emissions are higher under no-till systems
than under conventionally tilled systems
(Groffman et al., 1987). This increase could
be the result of fertilizer placement or the
increased use of herbicides associated with no-
till systems. Preliminary observations indicate
that application of post-emergent herbicides
leads to significant, but short-lived, increases
in N2O emissions (Breitenbeck, 1988). The
influence of tillage practices and herbicide use
on N2O emissions merits further study.
Legumes as a Nitrogen Source
Few studies have been done to
determine the role of nitrogen-fixing crops in
the emission of N2O. Estimates of N2O
emissions from legumes cover a wide range:
some are similar to those from fertilized crop
systems (Groffman et al., 1987), while others
are similar to emissions from fallow
unfertilized soil (Blackmer et al., 1982). If
N2O emissions from legumes as a nitrogen
source were comparable to emissions from
nitrogenous fertilizer, the use of legumes
would be superior from an overall greenhouse
gas perspective because of the great energy
requirement for production of ammonia-based
fertilizers. Further quantification of N2O
from legumes per unit of nitrogen supplied to
the soil is required.
Technologies that Improve Fertilization
Efficiency
Nitrification Inhibitors
Nitrification and urease inhibitors are
fertilizer additives that can increase efficiency
by decreasing nitrogen loss through
volatilization. Nitrification inhibitors can
increase fertilizer efficiency by 30% (Stangel,
1988).
Reduced Release Rate
Techniques that limit fertilizer
availability, such as slow-release or timed-
release fertilizers, improve nitrogen efficiency
by reducing the amount of nitrogen available
at any time for loss from the soil system.
Coatings
Limiting or retarding water solubility
through supergranulation or by coating a
fertilizer pellet with sulfur can double
fertilizer efficiency (Stangel, 1988).
Emerging Technologies
No breakthrough in chemical fertilizer
technology is anticipated in the near future,
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Policy Options for Stabilizing Global Climate
but there are likely to be improvements in
fertilizer production and application efficiency.
The development of a subsurface fertilizer
application method for no-till, for example,
could have a significant effect on N2O
emissions from that source.
Advances in biotechnology are likely to
affect N2O emissions from agriculture.
Engineering of crop varieties that are more
resistant to weeds could reduce herbicide use,
and in turn, decrease the emissions of N2O.
Nitrogen-fixing cereal crops, which
could be available by 2000, would decrease
the use of fertilizer on those crops. The
potential for reduced N2O emissions needs to
be examined (OTA, 1986).
Technological advances that increase
crop yield will help reduce the amount of
land and other inputs needed to produce the
goods required to support the population.
Improved yield and other efficiency
improvements hold potential for reducing
N2O emissions.
Alternative Agricultural Systems
Environmental concerns regarding
pollution of ground and surface water and soil
degradation from intensive agriculture have
renewed interest in alternative agricultural
systems. Such systems, sometimes referred to
as sustainable, alternative, or low-input, strive
to achieve a style and level of agricultural
production that has long-term sustainability
on the resource base. As compared with
conventional agriculture, such systems utilize
more thorough incorporation of natural
processes such as nutrient cycling, nitrogen
fixation, and pest-predator relationships;
reduce the use of off-farm inputs with the
greatest potential to cause environmental or
health effects; and seek to achieve profitable
and efficient production with emphasis on
conservation of soil, water, and biological
resources (NRC, 1989). The potential of
alternative agricultural systems to reduce
greenhouse gas emissions, while maintaining
food security and satisfying farm income
needs, needs to be evaluated holistically.
Alternative Agriculture and Nitrous Oxide
Alternative, low-input sustainable
agricultural systems frequently utilize crop
rotations, soil-conserving tillage practices, on-
farm nutrient sources, green manures
(leguminous crops), and integrated pest
management (IPM) techniques. Such systems
achieve energy savings by reducing the need
for plowing and lowering the fertilizer
requirement.
Crop Rotation. Rotating crops serves to
increase soil moisture, provide pest control,
and increase the availability of nutrients in
the soil. Rotating crops, rather than leaving
land fallow, can reduce N2O losses (see Crop
Type above). Crop rotations can reduce the
establishment of root pests and diseases,
leaving root systems better able to absorb
nutrients, thereby reducing the fertilizer
application requirement (NRC, 1989).
Conservation Tillage. Practices such as
low-till, no-till, and ridge-till reduce soil losses
and associated loss of nitrogen contained in
the soil. Tillage practices may reduce the
efficiency with which the fertilizer can be
applied. The overall effect on N2O emissions
(on and off the field) needs to be evaluated.
Organic Nitrogen Sources. Using
leguminous crops or animal manure as a
nitrogen source reduces the need for
additional nitrogen fertilizer, but may result in
similar or enhanced N2O emissions. The
energy savings and environmental benefits
associated with reduced use of nitrogen
fertilizer make this option appealing, but
better estimates of N2O from each type of
system is required.
Sustainable Agriculture and Land Conversion
Agricultural practices affect greenhouse
gas emissions in a large way through land
conversion, disturbance, and biomass burning.
Particularly in the tropics, the conversion of
forest to cropland, pasture, or fallow results
in a net loss of stored carbon (see PART
FOUR: FORESTRY). Much of the reduction
in stored carbon will come from the soil,
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Chapter V: Technical Options
evolving over time after clearing (Houghton
et al., 1983). Land clearing also results in a
net loss of N2O from the soil (Matson, pers.
communication). Slash and burn agriculture
(as discussed in PART FOUR) promotes high
levels of land conversion, and hence, a net
loss of carbon and nitrogen sinks.
Additionally, biomass burning associated with
slash and burn agriculture results in emissions
of CO2, CH4, N2O, CO, and NOr
Sustainable agricultural practices can do much
to reduce greenhouse gas emission by
reducing the demand for agricultural land and
by increasing organic nutrient storage in the
land. Carbon storage in these.systems is high
as compared with conventional systems (Lai,
1989).
Research Needs and Economic Considerations
Many uncertainties surround the factors
influencing N2O emissions from fertilizer.
Cultivation practices and environmental
practices that affect the fertilizer-derived
emissions of N2O have not been well
quantified. Additional research in the
following areas is needed:
• N2O emissions by fertilizer type;
• the effect of crop type on
emissions;
• the effect of water management
practices on emissions;
• N2O release from drainage and
ground water;
• N2O emissions from legumes and
manure;
• the effect of tillage and herbicide
use on N2O emissions;
• how the rate of fertilizer
application affects emissions;
• the effect on emissions of
different fertilizer management practices,
including fertilizer placement;
• how overall emissions from
conventional and alternative cropping systems
compare; and
• the contribution of tropical
agriculture to N2O emissions.
Most fertilizer use in Asia is for rice
cultivation. Rice is a significant source of
both CH4 and N2O. Fertilizer management
practices can affect the level of both CH4 and
N2O production. The production of the two
gases under different management regimes
needs to be explored, and trade-offs evaluated.
There is room for significant efficiency
improvement in this area.
Agricultural policies in the U.S.
dissuade the adoption of alternative
agricultural practices and systems by
economically penalizing those who adopt
rotations, apply certain soil conservation
systems, or attempt to reduce pesticide
application. Federal policies have made high
production levels a higher priority than
protection of the resource base, sometimes
encouraging inefficient fertilizer and pesticide
use and unsustainable use of land and water.
Fertilizer subsidies, target prices, and
loan levels encourage a level of fertilizer use
that is above the economic and environmental
optimum. Such policies also reduce the
attractiveness of more efficient fertilizer
application and use. Increased fertilizer
prices and the threat of shortages in fossil-
fuel-based fertilizers should increase interest
in fertilizer efficiency in the future.
ENTERIC FERMENTATION IN DOMESTIC
ANIMALS
Livestock play a vital role within the
agricultural sector, producing meat, dairy
products, and fiber. Ruminant animals,
including cattle, dairy cows, buffalo, sheep,
goats, and camels have the capability of
converting roughage into usable nutrients
through microbial fermentation. This unique
capability allows them to convert cellulosic
plant material to milk, meat, and fiber that
would otherwise be unavailable for human
consumption. Some non-ruminant animals
(e.g., horses and pigs) also produce CH4>
although in much smaller quantities.
Currently, ruminants contribute approximately
97% of the annual CH4 emissions from
domestic animals; non-ruminants contribute
approximately 3%.
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Policy Options for Stabilizing Global Climate
Protein of animal origin has the highest
biological value of all sources of protein.
Within the United States, animal products
supply 53% of all foods consumed, including
69% of the protein, 40% of the energy, 80%
of the calcium, and 36% of the iron in our
diets (English et al., 1984). In developing
countries, there is a continued and growing
demand for animal proteins.
About 24% of the world's land area is
in permanent pasture. Rangeland and
pastureland combined account for over 50%
of total land area in the world. Within Africa
and Oceania (Australia and New Zealand),
rangeland and pastureland comprise 65% and
75% of the land area, respectively (HED and
WRI, 1987). These areas are typically too
steep, arid, rocky, or cold to be suitable for
crops, but they provide forage for about 3
billion head of cattle, buffalo, sheep, and
goats (FAO, 1986).
The type and function of livestock
systems vary considerably around the globe.
Within developed economies in which meat is
a major export commodity, livestock are
intensively managed for either meat or dairy
production. Ranches within these economies
are typically large and use management
techniques such as selective breeding,
rangeland management, feed enhancement,
and the use of antibiotics to increase cattle
production.
Livestock within these systems are
typically larger animals, fed at least part of
the time on a high-quality grain diet. Fodder
crops are grown specifically for feeding cattle.
Most beef cattle are fed a high-quality, low-
cellulose diet in a feedlot for several months
prior to slaughter. These animals have a
much higher yield of meat or dairy product
than similar animals in developing countries.
Table 5-30 shows average meat production
per animal in several regions of the world.
Within less developed economies,
livestock are usually more integrated into the
whole agricultural system, frequently as a pan
of a crop/livestock or pasture-based system.
These animals are not always managed to
maximize reproductive efficiency or
slaughtered at the most efficient stage for
optimal productivity. They are frequently
maintained as scavengers and live on a low-
quality forage diet.
Livestock serve as a buffer within
agricultural systems by helping to stabilize
cash flows and food supplies. Livestock
production can serve to level out the effect of
climate variability and the seasonality of
rainfall in crop/livestock systems. Ruminant
livestock can salvage energy and nitrogen
from what otherwise could have been
complete crop failures. In a grain crop
failure, for example, vegetative matter suitable
for livestock consumption is still produced.
Livestock are convenient disposal systems for
crop residues and provide a sink for surplus
and damaged crops not suitable for human
consumption (Raun, 1981).
In Tanzania and other Central African
countries, tribal groups regard an increase in
animal numbers as the best insurance against
economic and social risk. The animals afford
protection against the uncertainties of climate
and destruction of crops by pests (Winrock,
1977). Livestock ownership enhances social
status in many developing countries.
In addition to the production of meat,
dairy products, and fiber, livestock are a
source of fertilizer, fuel, and provide most of
the tractor power in many developing
countries. Animals are used for plowing,
threshing, and providing power for irrigation.
Draft animals can increase farm output
several times by increasing the area that a
farm family can cultivate. Within Africa and
the Far East, over 80% and 90%, respectively,
of all draft power is provided by animals
(Raun, 1981).
Animal manure is used by about 40%
of the world's fanners to enhance soil fertility.
Dried dung can also be used as fuel. It is
estimated that over 200 million tons of
manure are used each year as fuel in
developing countries (Winrock, 1977).
Management Practices Affecting Methane
Emissions from Livestock
Enteric fermentation, the digestive
process that makes livestock so useful, causes
them to emit CH4 into the atmosphere. The
1272 million cattle, 1140 million sheep, 460
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Chapter V: Technical Options
TABLE 5-30
Average Meat Yield per Animal
(kilograms)
Region
North America
Europe & USSR
Oceania
Latin America
Near East
Far East & China
Africa
World Average
Beef & Veal
87.7
59.7
45.8
29.4
17.3
8.2
13.6
31.2
Mutton & Goat
11.1
6.6
5.7
2.7
4.4
4.0
3.5
4.7
Source: Stoddart et al., 1975.
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Policy Options for Stabilizing Global Climate
million goats, 126 million buffalo (FAO,
1985), and assorted other domesticated
animals contribute an estimated 65-100 Tg of
CH4 to the atmosphere annually. Of this
amount, approximately 57% comes from beef
cattle, 19% is from dairy cattle, and 9% is
from sheep (Lerner et al., 1988). With the
global cattle population increasing at 1.2%
per year (see CHAPTER IV), livestock will
continue to be a significant source of
methane.
Livestock cannot metabolize CH4. It is
lost energy, which neither contributes to the
animal's maintenance, nor to the production
of a product. Estimates of gross energy
intake lost as CH4 for cattle have ranged
from 3.5% (Johnson, 1988) to 8.3% (Blaxter
and Wainman, 1964).
Methane emissions from livestock are
affected by differences in quantity and quality
of feed, body weight, age, energy expenditure,
and enteric ecology. All other things being
equal, emissions are higher for animals that
are heavier, have higher feeding levels and
high-cellulose forage diets, and are ruminants.
Emissions are also higher for work animals
because some of the additional feed required
to supply this energy is converted to CH4
(Lerner et al., 1988). Manure is an
additional, unquantified source of CH4
(Winrock, 1977).
Although we know that animal type,
feed type, and management practice affect the
amount of CH4 generated by an animal, few
modifications to current practices are certain
to reduce CH4 production significantly.
Livestock System Productivity
Intensively managed, high-productivity
livestock systems ~ those with fewer, larger,
and more productive animals - produce more
animal product per unit of CH4 (Moe and
Tyrell, 1979). In these highly managed
livestock systems, as the feeding level is
increased, the level of CH4 production
increases, but the energy loss in relation to
gross energy intake decreases (Thorbek, 1980).
An animal fed at maintenance level, however,
loses a larger percentage of its gross energy
intake to methanogenesis than does an animal
fed at a higher level and has no increase in
animal product.
The vast differences between livestock
systems in developed and developing countries
make variances in productivity difficult to
compare. Additional benefits, such as the
work output of draft animals, must be
considered, but intensively managed, high-
productivity livestock systems are the most
efficient in terms of animal product yield.
Diet
At low levels of feed intake, or at
slightly above maintenance, a high-cellulose
forage diet results in lower CH4 production
per unit of feed than a high-nitrogen grain
diet. Conversely, at high levels of feed intake,
approaching three times maintenance, a high-
quality grain diet results in lower CH4
production per unit of feed (Blaxter and
Clapperton, 1965). Overall, CH4 emissions
from an animal at any level of feed intake
seem to decline with increased digestibility of
the feed (Gibbs et al., 1989).
This information suggests that feeding
practices could be modified for some feedlot
animals to reduce overall CH4 emissions.
Gibbs et al. (1989) suggest that "low-CH4"
diets could be identified that reduce CH4
emissions without sacrificing animal
productivity. The use of oils as a feed
supplement also has potential for reducing
CH4 emissions. The implications of
modifying feeding strategies on feed costs,
animal productivity, and CH4 emissions need
to be thoroughly evaluated. Such analysis
needs to consider energy inputs and N2O
emissions resulting from production of the
feed. For example, the CH4 reduction
achieved from switching from a forage diet to
corn could be largely offset by the N2O
production and energy consumption associated
with the row crop. Once again, the whole
system needs to be evaluated as a unit.
Nutritional Supplements
In developing countries, animals are
generally living near maintenance levels and
subsisting on a high-cellulose diet of forage
and agricultural by-products such as wheat
V-164
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Chapter V: Technical Options
straw, rice straw, and sugar cane tops.
Methane yields in these animals may be as
high as 9-12% of gross energy intake due to
low digestibility of the diet and ammonia
deficiency in the rumen (Preston and Leng,
1987). If this is the case, providing nutrient
supplements of urea or poultry litter to these
animals could increase animal productivity
and reduce CH4 emissions. However, further
research is needed in this area since no
measurements of CH4 generation have been
done on livestock within farm conditions of
developing countries.
Feed Additives
Feed additives, which increase feed use
efficiency and reduce CH4 generation by
modifying rumen fermentation, are currently
available for beef cattle. These feed additives,
known as ionophores, are fed to most feedlot
cattle to improve the efficiency of beef
production during finishing for market
Ionophores reduce the amount of CH4
produced by a ruminant by improving
digestive efficiency (less is produced) and by
causing the animal to eat less, which leaves
less food in the gut to ferment Ionophores
improve the efficiency of beef production by
6-8%, while reducing CH4 production by
approximately 5% for animals on a forage
diet, and by approximately 20% for animals
on a high-grain diet (Johnson, 1988).
Ionophores have been shown to lose
methane-suppressing effectiveness over time
as the bacteria in the gut develops a tolerance
to them (Johnson, 1974). A feeding program
that alternates different ionophores has been
suggested to improve overall efficiency by
impeding bacterial adaptation (Hubbert et al.,
1987).
The use of ionophores is predominately
limited to feedlot cattle because of the
difficulties associated with administering a
drug to range cattle. Range cattle can be fed
ionophores using a mineral block lick, but few
range cattle receive this drug.
Feed additives are not currently
available for dairy cattle, and are unlikely to
become available because of problems with
efficiency and chemical residues in the milk.
In developing countries, where cattle are
generally used for milk and meat production,
ionophores cannot be used.
Methane from Manure
Under anaerobic conditions, microbial
decomposition in manure generates CH4.
The amount of CH4 produced depends upon
the waste management method used and
temperature and pH of the system. The
waste of livestock managed in confined
feedlots or dairies is frequently piled or
flushed into waste lagoons. Disposing of
manure in lagoons or flooded fields creates
anaerobic conditions conducive to the
generation of CH4.
Overall CH4 production from this
source is uncertain, largely due to a lack of
information on manure disposal by method,
and lack of data on CH4 production across a
range of lagoon systems. Measurements of
CH4 generation from waste lagoons and
anaerobic digesters have been on the order of
0.14 to 1.0 cubic meters of volatile solids
added to the lagoon (Safley and Westennan,
1988), which translates into about 12-85 kg of
CH4 per ton of manure (wet weight).
Because a 600-kilogram (kg) dairy cow
produces about 15 tons of manure per year
(wet weight), the disposal of this manure in a
lagoon could result in 120-825 kg of CH4
emissions per head per year (Gibbs et al.,
1989). This amount of CH4 production is on
the order of ten times that which originates in
the animal's rumen, but this level is often not
realized due to variability in disposal methods.
Swine and poultry wastes produce a similar
amount of CH4 emissions per ton of waste
(Gibbs et al., 1989).
Methane from manure can be captured
and used as an energy source. Techniques are
being developed and are in use for covering
waste lagoons and capturing the CH^ which
can then be used to generate electricity for
use on the farm or can be sold to an
electricity grid. Energy from manure can also
be captured in the form of CH4 in biogas
plants. Manure produced by ruminants,
particularly cattle and buffalo, is an ideal
substrate for anaerobic fermentation in biogas
plants. Methane from manure has a value of
5 kilocalories (kcal) per cubic meter (about
70% of the energy value of natural gas). In
V-165
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Policy Options for Stabilizing Global Climate
the U.S., the dung from about 40 cows could
provide all of the non-mobile fuel for a farm
family, including electricity. Disposal of
manure in biogas plants can reduce CH4
generation, while still providing a fertilizer
source from the residue (Winrock, 1977).
Emerging Technologies
Efficiency improvements and advances
in biotechnology have resulted in considerable
productivity increases for beef cattle, dairy
cattle, and sheep. Since 1940, dairy
production in the U.S. has remained relatively
constant while the herd size has been cut in
half (English et al., 1984). Efficiency
improvements should continue to produce
gains in productivity, along with associated
reductions in CH4 emissions.
Bovine growth hormone, a
bioengineered imitation of a naturally
occurring protein in cattle, is expected to
increase productivity in dairy cattle by 10-
15%. This drug, which has not yet been
approved by the U.S. Food and Drug
Administration, is likely to decrease CH4
production per unit of milk (Tyrell, 1988). A
net decrease in CH4 production could be
achieved through a reduction in the size of
the dairy herd.
Improving reproductive efficiency in
dairy cows and beef cattle would reduce the
brood herd requirement, and thereby decrease
CH4 emissions by decreasing the livestock
population. The total size of the cattle
population can be reduced by reducing losses
from disease, increasing the birth rate and
decreasing the inter-calving interval of cows
used to produce calves, and increasing the
success rate of replacement heifers. In
developing countries nutritional management
programs may be required to improve the
reproductive success rate and calf survival
(Gibbs et al., 1989).
The development of a methanogenesis
inhibitor for dairy cattle is unlikely in the
near future. Improving the ionophore
delivery system for range cattle could increase
use of that additive.
There is also some potential for
reducing CH4 production by inhibiting fungus
in the rumen of cattle. These fungal
interactions need to be more thoroughly
investigated before fungal inhibitors can be
developed.
Through longer-term research in
biotechnology, there exists the potential to
develop microbial species capable of
convening hydrogen to a useful hydrogen
sink, rather than to CH4. Acetic acid is such
a hydrogen sink, which is useful as an energy
source in cattle.
Animal scientists have long been
working on the problems of improving feed-
use efficiency and livestock system
productivity and, thereby, the problem of CH4
generation. This research should continue to
reduce CH4 generation per unit of animal
product within highly managed systems.
Research Needs and Economic Considerations
Further research is needed on livestock
in developing countries in order to devise a
strategy to reduce CH4 generation. For
example, estimates of CH4 generation are
needed for a range of livestock (including
draft animals) on a variety of diets. Also, the
potential for using antibiotics, such as
ionophores, on cattle needs to be explored.
We also need to quantify CH4
generation from manure under a range of
management and disposal options. Incentives
may need to be provided to initiate further
use of manure as an energy source.
Commodity programs in the U.S.
encourage a larger cattle population than
there otherwise would be. Unnaturally low
grain prices, which are a result of price
supports, are, in effect, a subsidy to beef and
dairy production. Beef producers are also
protected by a tariff, which in recent years has
been converted to a variable levy (Schuh,
1988). These policies result in a larger cattle
herd and increased production of CH4.
V-166
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Chapter V: Technical Options
NOTES
1. EJ = exajoule; 1 exajoule = 1018 joules.
2. kJ = kilojoule, 1 kilojoule = 103 joules.
3. GJ = gigajoule, 1 gigajoule = 109 joules.
4. PJ = petajoule; 1 petajoule = 1015 joules.
5. 1 MJ = 1 megajoule = 106 joules.
6. Natural gas is mostly methane, but the
methane content can vary from less than 70%
to nearly 100% depending on the source of
the gas. We refer to the vented or flared
gases as methane, although other trace gases
may also be present.
7. This estimate assumes a carbon content of
22% (Bingemer and Crutzen, 1987), that 90%
of municipal solid waste generated is
landfilled, and a conservative methane
production efficiency of 0.25 ton of methane
per ton of carbon.
8. 1 hectare = 2.471 acres.
9. t C = tons of carbon.
10. Pg = petagram. 1 Pg = 1015 grams.
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Schuh, G.E. 1988. Agricultural Policies for
Climate Changes Induced by Greenhouse
Gases. Report prepared for U.S. EPA,
Washington, D.C.
Safley, Jr., L.M. and P.W. Westerman. 1988.
Anaerobic Lagoon Biogas Recovery Systems.
Presented at the 1988 Winter Meeting of the
Agricultural Society of Agriculture Engineers,
Chicago, Illinois, 31 pp.
Stangel, P. 1988. Technological Options
Affecting Emissions. Presented at U.S. EPA
Workshop on Agriculture and Climate
Change, Washington, D.C, February 29-March
1, 1988, and personal communication.
Stoddart, L., A. Smith, and T. Box. 1975.
Rangeland Management. McGraw-Hill, New
York.
Thorbek, G. 1980. Commission on Animal
Nutrition, Factors Influencing Energy Losses
During Metabolism. Evaluation of Energy
Systems. Energy Losses in Methane. National
Institute of Animal Science, Copenhagen.
Tyrell, H. 1988. Livestock Emissions
Estimates. Presented at U.S. EPA Workshop
on Agriculture and Climate Change,
Washington, D.C, February 29-March 1,1988.
Winrock. 1977. Ruminant Products: More
than Meat and Milk. Windrock International
Livestock Research and Training Center.
Morrilton, Arkansas.
World Bank. 1988. World Bank, FAO,
UNIDO Fertilizer Working Group Nitrogen
Supply, Demand and Balances for 1986/87 to
1992/93. The World Bank, Washington, D.C.
V-L88
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CHAPTER VI
THINKING ABOUT THE FUTURE
FINDINGS
• Decisions made in the next few decades
about how electricity is produced, homes are
constructed, and cities are laid out, for
example, will have an impact on the climate in
2100 and beyond. While it is not possible to
precisely predict the level of greenhouse gas
emissions over this time period, it is possible
to construct scenarios of economic and
technological development, and a reasonable
range for resulting greenhouse gas emissions,
atmospheric concentrations, and global
temperature changes. Global temperature
change estimates provide an indicator for the
rate and magnitude of climate change.
• If stabilizing policies are not adopted,
carbon dioxide (CO2) emissions are likely to
grow by a factor of 2 to 5 during the next
century, primarily due to expansion of global
coal consumption. Options are available,
however, that could stabilize or reduce CO2
emissions. Despite the Montreal Protocol to
control CFCs, without the June 1990 London
Amendments global emissions of these
compounds would remain constant, or even
increase significantly. The stabilizing policy
scenarios presented here were produced prior
to the negotiations of the London
Amendments and are somewhat more
stringent than the London Amendments.
Methane emissions could increase by 60-100%,
or even more during the next century unless
measures to control these emissions are taken.
• Although per capita emissions of
greenhouse gases are currently very low in
developing countries, their share of global
emissions will probably rise significantly in the
future.
• The relative contribution of CO2 to
greenhouse warming is likely to increase
significantly in the future. Carbon dioxide
accounts for at least 60% of the increased
commitment to global wanning between 2000
and 2100 in all of the scenarios analyzed in
this report. This represents a significantly
higher estimate of the role of CO2 compared
to its roughly 50% contribution to greenhouse
forcing in the last few decades, but is similar
to the estimated contribution of CO2 to
increases in the greenhouse effect over the last
century.
• If there is no policy response to the risk
of climate change, CO2 concentrations are
likely to reach twice their pre-industrial levels
sometime in the latter half of the 21st century,
but total greenhouse gas concentrations
equivalent to this level may occur by 2030 or
before, and are likely to occur before 2050.
• Even with modest economic growth and
optimistic assumptions regarding technical
progress, the world could be committed to an
equilibrium warming of 1-2°C by 2000, 2-5°C
by 2050, and 3-6°C by 2100 (assuming the
climate sensitivity to doubling CO2 is 2.0-
4.0°C). Realized warming would be about 2°C
by 2050 and 3-4°C by 2100.
• With rapid, but not unprecedented rates
of economic growth, the world could be
committed to an equilibrium warming of 1-2°C
by 2000, 3-6°C by 2050, and 5-10°C by 2100
(assuming that the climate sensitivity to
doubling CO2 is 2.0-4.0°C). Realized warming
would be 2-3°C by 2050 and 4-6°C by 2100.
Estimated warming commitments greater than
6°C may not be fully realized because the
strength of some positive feedback mechanisms
may decline as the Earth warms.
• The adoption of policies to limit
emissions on a global basis, such as
simultaneous pursuit of energy efficiency, non-
fossil energy sources, reforestation, the
elimination of CFCs and other measures,
could reduce the rate of wanning during the
21st century by 60% or more. Even under
these assumptions, the Earth could ultimately
warm by 1-4°C or more relative to pre-
industrial times. Extremely aggressive poli-
cies to reduce emissions would be necessary to
ensure that total warming is less than 2°C.
VM
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Policy Options for Stabilizing Global Climate
INTRODUCTION
Although technological advances in
industry and agriculture have provided
extraordinary wealth to a portion of the global
population of over 5 billion people, these
technologies have the potential to dramatically
alter the Earth's climate by causing changes in
the composition of the atmosphere as
discussed in Chapters II through IV. Global
increases in the atmospheric concentrations of
carbon dioxide (CO2), nitrous oxide (N2O),
methane (CH4), and chlorofluorocarbons
(CFCs) are now well documented (see
CHAPTER II), perhaps already committing the
Earth to significant climate change. Myriad
human activities are contributing to this
situation, and continued population and
economic growth raise the prospect of
accelerated greenhouse gas buildup in the
future (see CHAPTER IV).
If current trends in trace-gas
concentrations continue, the average surface
temperature of the Earth could be warmer
than at any time in recorded human history by
the second decade of the 21st century. If the
composition of the atmosphere were stabilized
by 2000, on the other hand, detectable climatic
change is still possible, but its magnitude
would be limited, and the rate of change might
be similar to natural fluctuations recorded in
the geologic record (Hansen et al., 1988).
What will happen in the future cannot
be predicted. The future evolution of the
atmosphere will depend largely on the paths of
economic development and technological
change, as well as on the physical, chemical,
and biological processes of the Earth-
atmosphere system. While we have no control
over this system once gases enter the
atmosphere, economic and technological
change will be influenced by policy choices
made at local, national, and international
levels. This chapter explores some of the
paths that the world might follow in the
decades ahead and provides an indication of
the relative climatic consequences under these
alternatives. After a discussion of the
economic and social factors that determine
emissions, six scenarios of economic and
technological development are presented.
These scenarios are not intended to capture
the full range of possibilities; rather, they have
been developed in order to explore the
greenhouse consequences of significantly
different, but plausible, economic and
technological conditions. The warming
implications of these scenarios are analyzed
using an integrated atmospheric stabilization
framework described briefly in this chapter and
in greater detail in Appendix A and ICF
(1989). The chapter concludes by discussing
the results of this analysis, compares these
results with other studies, and evaluates how
changes in key parameters affect our portrayal
of the rate and magnitude of global climate
change.
APPROACH TO ANALYZING FUTURE
EMISSIONS
The scope of this analysis must be
global, and because of the long lags built into
both the economic and climatic systems, this
study must consider a time horizon of more
than a century -- we chose 2100 as the ending
year for the analysis. While this is an eternity
for most economists and planners, it is but a
moment for geologists. And indeed, decisions
made in the next few decades about how
electricity is produced, homes are constructed,
and cities are laid out, for example, will have
an impact on the climate in 2100 and beyond.
Decisions about what kinds of automobiles
and other industrial products to produce and
how to produce them will also have a
profound impact. These choices, which will
affect the amount and type of fuel we use to
travel, to heat and light our homes and offices,
and to run our factories, will influence the
magnitude of greenhouse gas emissions for
many years.
The vast difference between the energy
demand projections of the early 1970s and
what has actually occurred in the 1980s
illustrates the danger inherent in simple trend
extrapolations, and even in making predictions
based on results obtained from more complex
econometric models. Our approach, then, is
not an attempt to predict the future, but a
construction of what we believe are logically
coherent scenarios of possible paths of
economic and technological development. An
analytical framework is used to keep track of
the assumptions, data, and relationships
needed to define the scenarios. Our intent is
to define the climatic risks associated with
VI-2
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Chapter VI: Thinking About the Future
various economic/social/technological
alternatives and, in so doing, increase the
likelihood that these risks will be taken into
account when policy decisions are made. If we
believe that under a wide variety of
assumptions about long-term economic growth
and technological change the world will face
rapid warming in the absence of political or
economic forces arising from concerns over
the greenhouse problem, then it will be
necessary to seriously examine the options
available for reducing greenhouse gas
emissions.
Projections of greenhouse gas emissions
are very uncertain, however, because of
uncertainties in world economic growth, future
fuel prices (which demonstrably affect both the
intensities of their use and the substitution
amongst alternative energy sources), future
rates of land clearing, and rates of
technological change, among other factors.
For example, both the vagaries of the world oil
market in the medium term, as well as
uncertainties regarding the long-term
relationship between the cost of producing
fossil fuels, and the cost of using those fuels in
ways that are relatively benign to the local
environment, mean that at best we can only
guess at future fossil-fuel use.
Another avenue of analysis, however,
yields information that can guide policymakers
who will be faced with these uncertainties. If
we can construct scenarios of future energy
demand, land-clearing rates, CFC production,
etc., that are driven by reasonable assumptions
about population growth, economic growth,
technologies, and energy prices, then we can
develop a plausible range of future greenhouse
gas emissions. To accomplish this task we
must consider the structural factors that
determine the quantities and patterns of
emissions of chemically and radiatively
important trace gases (i.e., those gases whose
presence in the atmosphere contribute to
greenhouse warming).
It is conceptually useful to distinguish
between production activities and consumption
activities. Production, that is, the processing of
bulk materials ~ steel from ore, plastics from
petroleum, cement and glass from limestone
and silicate rock - requires large amounts of
energy per unit of industrial value added (i.e.,
the difference in value between an industry's
products and its inputs) and may also be
associated with direct emissions of greenhouse
gases. For example, during cement-making,
limestone (CaCO3) is reformed to lime (CaO)
and CO2, and the CO2 is released to the
atmosphere; during the making of plastic
foams, CFCs are released. Much lower
emissions per unit of value added are generally
associated with fabrication and finishing.
Food production leads to emissions of CH4
and N2O as discussed in Chapter IV, as well as
to emissions of CO2 and other gases as a
result of the energy used on and, even more,
off the farm. The large amount of energy
required to move freight is also attributable to
production activities. Consumption leads to
greenhouse gas emissions as people use
energy, primarily in pursuit of comfort (space
heating and air conditioning) and mobility
(automobile and air travel). Other major end
uses for energy include refrigeration, lighting,
water heating, and cooking.
Production
As societies develop over time, both the
quantity and the structure of activities that
influence emissions change radically. For
example, energy use per unit of Gross
National Product (GNP) has declined steadily
and dramatically over the past 70 years in the
United States, even in periods of declining real
energy prices (see Figure 6-1). This decline is
due to a combination of two factors. First,
improvements in production processes, which
often save capital and labor as well as energy,
reduce the energy intensity per ton of physical
output. For example, in steel production
modern energy recovery and process
technology make it possible to produce a ton
of steel using only BxlO9 joules (13 GJ) of
final energy, less than half of the current U.S.
average.1 New processes under development
in Sweden (Elred and Plasma-Smelt) that
integrate several operations have even lower
energy requirements and reduced overall costs
(Goldemberg et al., 1988). Second, the bulk
of value added by industry tends to shift from
basic materials processing to fabrication and
finishing as a country's infrastructure matures.
Williams et al. (1987) suggest that
consumption of steel, cement, and other raw
materials begins to decline after income
surpasses about $5000 (1985$) per capita (see
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Policy Options for Stabilizing Global Climate
FIGURE 6-1
TOTAL U.S. ENERGY CONSUMPTION PER GNP DOLLAR
1900-1985
(Megajoules/1982 Dollar)
50
45
40
35
30
CO
o>
5 2S
o
20
15
10
1900 1910 1920 1930 1940 1950 1960 1970 1980
Y*ar
Sources: EIA, 1987; U.S. Bureau of DM COIMIM, 1976.
VI-4
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Chapter VI: Thinking About the Future
Figure 6-2). These shifts in technology and
the mix of products generally increase the
share of energy consumed as electricity but do
not significantly increase absolute electricity
intensity because efficiency in electric end uses
improves as well (Kahane, 1986). Rapid
economic growth over the long term can be
expected to accelerate the reduction of
industrial energy intensity in wealthier
countries by promoting the replacement of old
plants and equipment with more efficient
technology, as well as by accelerating the shift
toward a less energy-intensive product mix
In industrialized societies, services such
as public and private administration, health
care, and education are likely to grow faster
than GNP, both because much of industry is
being redefined as services and because much
of our new wealth is being created by the
development and transfer of information.
Heating, air conditioning, and lighting, which
dominate energy and electricity use in
buildings today, will become less energy-
intensive (even as indoor environmental
quality continues to rise) as more efficient
technologies are adopted. At the same time,
information technology is exerting upward
pressure on electricity use per square foot in
office buildings and schools. The Business
Services sector depends more on electricity
than does any other sector in the economy,
although it still uses less electricity per unit of
output than industry. If there is to be a large
increase in electricity use in industrialized
countries, it will most likely come from a
massive expansion of the services sector.
The greatest potential for large increases
in production-related emissions lies in
developing countries. As these countries
expand their industrial infrastructure, the
demand for basic materials could skyrocket.
But developing countries have the opportunity
to take advantage of new processes and
materials that sharply reduce the energy
required to produce a given level of amenity.
As a result, it is unlikely that materials and
energy intensity per capita in developing
countries would reach the levels of
industrialized countries today, even as similar
levels of per capita income are achieved. The
extent to which developing countries seize
these opportunities will strongly influence
future greenhouse gas emissions.
Consumption
The factors influencing emissions arising
from consumption are quite different from
those that affect production. In developing
countries, energy use in consumer products
can be expected to increase rapidly as the
number of households that can afford to
acquire fans, televisions, refrigerators, and
automobiles grows. Part of the reason that
developing country energy demand has
historically increased faster than it did in
member countries of the Organization for
Economic Cooperation and Development
(OECD) is that households in developing
countries can afford to purchase these
products at lower income levels than
households in industrialized countries. The
declining price-to-income ratios for many of
the energy-intensive consumer goods make this
possible, with the consequence that energy
consumption in developing countries tends to
grow more rapidly than the experience of the
industrialized countries might indicate. At the
same time, the efficiency of many of these
products is increasing, so that per capita
energy consumption in developing countries
may not reach the levels of industrialized
countries today.
As a society becomes wealthier, it
becomes saturated with energy-intensive
equipment (there are, e.g., 600 cars for every
1000 people in the U.S. compared to 6 cars
per 1000 in Asian countries). In addition,
changes in the efficiency of the stock and how
the stock is used become more important than
changes in the levels of ownership alone. For
example, as automobile ownership shifts from
corporate to private hands, the number of
vehicles increases dramatically, but the miles
driven per vehicle declines. Consumers rarely
consider energy use in making major
purchases, and many key decisions that
determine energy requirements are made by
developers rather than by the consumers who
pay the energy bills (Ruderman et al., 1987).
Amenity levels can often be increased at the
same time that energy use and emissions are
reduced (better insulated houses are more
comfortable because they are less drafty, and
more efficient air conditioners are usually
quieter), but more affluent consumers are
likely to choose powerful cars and spacious
dwellings, paying less attention to the
VI-S
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Policy Options for Stabilizing Global Climate
FIGURE 6-2
n
'a.
U
$
UNITED STATES CONSUMPTION OF BASIC MATERIALS
Consumption per Dollar of GNP
3000
G.N.P. Per Capita (In 1983 Dollars)
4000 5000 8000 11000
14000
70.
60.
50.
40-
30-
20.
» /
\
l »• / \
/ jc?L_/
-6
lJ
k< °-l
ao
Consumption p«r Capita
TOO- I
600.
500.
400.
300-
200.
100.
I J I 1 I I TII
1890 1900 1910 1920 1930 1940 1950 1960 1970 1980
Year
Source: Williams «t •!., 1987, In Goktemtorg »t al., 1987.
.70
-60
«
.50 I
£
40 (£
.30 I
2
.20
10
.0
-------
Chapter VI: Thinking About the Future
associated operating costs. Furthermore,
because a very wide range of efficiency can be
achieved with a small impact on total costs
over the life-cycle of the product (see
CHAPTER V; von Hippel and Levi, 1983;
Ruderman et al, 1987), consumers who are
concerned primarily about initial cost are
unlikely to choose a product with the
maximum level of efficiency justified on
economic and environmental grounds.
The level and pattern of mobility may
be the most significant uncertainty in future
energy use. Will we spend our free time in
our air-conditioned homes watching rented
movies on the VCR/TV, or are we more likely
to drive to the countryside to go hiking? Not
surprisingly, the pattern of automobile use at
present (roughly 1/3 of all passenger-
kilometers driven in the U.S. are to and from
work, 1/3 are for family business, and 1/3 are
in pursuit of leisure activities; OTA, 1988) is
a function both of distances between where we
live, work, and relax, and of how often we
choose to move about. Similarly, airline
travel, already dominated in the U.S. by
personal rather than business travel, is
increasingly determined by how and where
people want to spend their free time.
Meanwhile, in cities like Hong Kong, Sao
Paulo, New York, and Los Angeles, congestion
is increasingly constraining automobile use.
The level of fuel economy and emissions
achieved by a particular automobile in practice
is very sensitive to average speed, which is
down to about 15-20 miles per hour in Los
Angeles and under 10 miles per hour in New
York City (M. Walsh, pers. communication,
1988). How and whether cities solve these
congestion problems« with roads, car and van
pools, buses, light rail, or all of the above -
will have a large impact on both urban and
global environmental quality.
SCENARIOS FOR POLICY ANALYSIS
In order to explore some of the
implications of the relationships discussed
briefly above, we have constructed six
scenarios of future patterns of economic and
technological development starting with
alternative assumptions about the rate of
economic growth and the adoption of policies
that influence climate change (see Table 6-1).
These six scenarios cannot capture all the
possibilities, of course; rather, they allow us to
explore likely climatic outcomes and the
impact of strategies for stabilizing the
atmosphere as well as policies that may
accelerate emissions. The sensitivity of the
results to a wide range of specific assumptions
has been tested and is discussed later in this
chapter and in Appendix C.
Two scenarios explore alternative
pictures of how the world may evolve in the
future assuming that policy choices allow
unimpeded growth in emissions of greenhouse
gases (these are referred to as the "No
Response11 scenarios). One of these scenarios,
called a Rapidly Changing World (RCW),
assumes rapid economic growth and technical
change; the other assumes more gradual
change and is called the Slowly Changing
World (SCW). That is, we have invented one
future with relatively high and robust
economic growth and another representing a
more pessimistic view of the evolution of the
world's economies. The first world would
likely illustrate the upper half of the potential
range of future greenhouse gas emissions,
because in general, higher economic activity
means higher total energy use and emissions.
Conversely, the second world could serve as a
useful guide to the lower half of the range. In
either case, our scenarios are first constructed
as if there were no interventions motivated by
global climate problems.
In constructing these two worlds/
scenarios, we have borne two important ideas
in mind. First, there is evidence that with
more rapid economic growth, energy-efficiency
improves more rapidly than with slower
growth (Schurr, 1982). This occurs because
innovation proceeds more rapidly and because
older, less efficient systems are more rapidly
replaced with new technology. History shows,
for example, that for almost every country,
energy efficiency in industry increases with
increasing incomes, as sophistication and scale
win over brute force. At the same time,
higher incomes allow people to spend more
money on two key energy-intensive uses, space
conditioning (heating and air conditioning),
and automobiles. Thus, not all of the
technological benefits of rapid economic
growth put the brakes on overall energy use.
But more rapid economic growth allows
society to put resources aside to improve the
VI-7
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Policy Options for Stabilizing Global Climate
TABLE 6-1
Overview of Major Scenario Assumptions
Slowly Changing World
Slow GNP Growth
Continued Rapid Population Growth
Minimal Energy Price Increases
Slow Technological Change
Carbon-Intensive Fuel Mix
Increasing Deforestation
Montreal Protocol/Low Participation
Rapidly Changing World
Rapid GNP Growth
Moderated Population Growth
Modest Energy Price Increases
Rapid Technological Improvements
Very Carbon-Intensive Fuel Mix
Moderate Deforestation
Montreal Protocol/High Participation
Slowly Changing World
with Stabilizing Policies
Slow GNP Growth
Continued Rapid Population Growth
Minimal Energy Price Increases/Taxes
Rapid Efficiency Improvements
Moderate Solar/Biomass Penetration
Rapid Reforestation
CFC Phaseout
Rapidly Changing World
with Stabilizing Policies
Rapid GNP Growth
Moderated Population Growth
Modest Energy Price Increases/Taxes
Very Rapid Efficiency Improvements
Rapid Solar/Biomass Penetration
Rapid Reforestation
CFC Phaseout
Rapidly Changing World
with Accelerated Emissions
High CFC Emissions
Cheap Coal
Cheap Synfuels
High Oil and Gas Prices
Slow Efficiency Improvements
High Deforestation
High-Cost Solar
High-Cost Nuclear
Rapidly Changing World
with Rapid Emissions Reductions
Carbon Fee
High MPG Cars
High Efficiency Buildings
High Efficiency Powerplants
High Biomass Penetration
Rapid Reforestation
Vl-8
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Chapter VI: Thinking About the Future
efficiency of both space comfort and personal
transportation. Similar patterns can be
expected in other economic sectors.
Conversely, slower economic growth
retards innovation, in part because neither
consumers nor producers see bright economic
times that would make innovation and
expansion into new technologies useful.
Comfort and mobility still manage to increase
as important drivers of personal energy
demand, but at a slower rate. When these two
paths are compared, the effect of more rapid
efficiency increases in the higher growth world
is a narrowing of the difference in greenhouse
gas emissions; that is, the likely difference
between levels of emissions in the Rapidly and
Slowly Changing Worlds is less than the
differences in GNP. This result makes our
scenarios somewhat more robust than one
might otherwise think.
The second idea concerns energy prices.
In a world of high and robust economic
growth, which we have assumed in the RCW
scenario, energy demand will likely, increase,
and in the medium term, so will energy prices.
Yet if energy efficiency increases, then energy
prices can increase more rapidly than the rate
of economic growth and still not consume an
increasing share of national wealth and
income. In other words, energy prices can rise
without putting the brakes on economic
growth, as long as the price increases are
gradual (CONAES, 1980). But in a world of
sluggish economic growth, energy demand rises
more slowly, so that energy prices would rise
very little. This relationship is an additional
reason why we believe that energy efficiency
increases more rapidly in the high growth
scenario (RCW) than in the low growth
scenario (SCW).
With these ideas in mind, we can build
scenarios of world energy demand by end use
and region, as well as levels of other activities
that emit greenhouse gases. The scenarios are
not exact predictions; rather, they serve as
guides to the level of emissions associated with
each important purpose or end use in the
worlds we constructed.
This approach allows us to compare the
utilization efficiencies that we assume for the
No Response scenarios with those we believe
achievable if more than just market forces
were acting. Two additional scenarios
(referred to as the "Stabilizing Policy"
scenarios) incorporate the same economic and
demographic assumptions but also assume that
policies to contend with global climate change
are adopted. These scenarios are called the
Slowly Changing World with Stabilizing
Policies (SCWP), and the Rapidly Changing
World with Stabilizing Policies (RCWP). In
addition, we add a variant of the RCWP case
called the Rapidly Changing World with Rapid
Emissions Reductions (RCWR); for this
scenario we assume that policies are more
aggressive than those under the RCWP
scenario. A fourth additional scenario
assumes emissions accelerate because of policy
choices that directly conflict with concerns
about global warming; this scenario, called the
Rapidly Changing World with Accelerated
Emissions (RCWA), is more pessimistic than
the RCW scenario since policy choices
increase the rate of greenhouse gas buildup.
Using our best information about
technologies that could become available, or
technologies that are already available but not
taken up by the market because of market
failures or other reasons, we can reconstruct
activity patterns that are still consistent with
our overriding economic assumptions, but
produce much lower (or higher) levels of
greenhouse gas emissions. Key changes are
assumed in energy efficiency, the energy supply
mix, land-clearing rates, and other factors that
might be changed by government policies or
other means.
In other words, we keep the basic
scenarios but, for example, manipulate
important energy-use patterns within these
scenarios. These manipulations can only be
carried out if greenhouse gas emissions in each
scenario are constructed from the bottom up,
i.e., by specifying the level of each major
emitting activity, as well as the emissions per
unit of activity (e.g., total harvested rice paddy
area and methane emissions per square meter
of paddy).
Thus, the scenarios we constructed
illustrate a range of greenhouse gas emissions
under two quite different assumptions about
economic growth and under various
assumptions about adoption of a variety of
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Policy Options for Stabilizing Global Climate
strategies to reduce emissions. In the final
analysis, our work can be turned around, and
we can ask what level of economic growth,
agricultural activity, policy implementation,
etc., is necessary in order to leave the world's
climate tolerable.
Scenarios with Unimpeded Emissions Growth
In a Slowly Changing World (SCW) we
consider the possibility that the recent
experience of modest economic growth will
continue indefinitely, with no concerted policy
response to the risk of climate change. In this
scenario we assume that the aggregate level of
economic activity (as measured by GNP)
increases relatively slowly on a global basis
(see Table 6-2). Per capita income is stagnant
for some time in Africa and the Middle East
as rapid population growth continues. Modest
increases in per capita income occur
elsewhere, and per capita growth rates increase
slightly over time in all developing countries as
population growth rates slowly decline (see
Figure 6-3). The share of global income going
to the developing world increases with time,
but not dramatically. The population engaged
in traditional agriculture and shifting
cultivation continues to increase, as do
demand for fuelwood and speculative land
clearing. These factors lead to accelerated
deforestation until tropical forests are virtually
eliminated toward the middle of the next
century.
In industrialized countries economic
growth is sluggish, although per capita income
reaches about 540,000 by 2100 in the OECD.
Because of slack demand, real energy prices
increase slowly. Correspondingly, existing
capital stocks turn over slowly, and production
efficiency in agriculture and industry improve
at only a moderate rate. The energy efficiency
of buildings, vehicles, and consumer products
also improves at a slow rate.
In a Rapidly Changing World (RCW)
we assume that rapid economic growth and
structural change occur and that little
attention is given to the global environment.
Per capita income rises rapidly in most regions
and consumer demand for energy increases,
putting upward pressure on energy prices. On
the other hand, there is a high rate of
innovation in industry, and capital stocks turn
over rapidly, which leads to an accelerated
reduction in energy required per unit of
industrial output. An increasing share of
energy is consumed in the form of electricity,
produced mostly from coal. The fraction of
global economic output produced in the
developing world increases dramatically as
post-industrial structural change continues in
the industrialized world. As educational and
income levels rise, population growth declines
more rapidly than in the SCW scenario (see
Figure 6-3).2 Deforestation continues at
about current rates, spurred by land
speculation and commercial logging, despite
reduced rates of population growth. Energy
efficiency is not much of a factor in consumer
decisions, as incomes increase faster than real
energy prices. Private vehicle ownership
increases rapidly in developing countries while
air travel increases rapidly in wealthier ones.
Nonetheless, significant reductions in energy
intensity occur with technological innovation
and structural change.
Scenarios with Stabilizing Policies and
Accelerated Emissions
Three variants of the above scenarios
explore the impact of policy choices aimed at
reducing the risk of global warming. These
scenarios, labelled Slowly Changing World
with Stabilizing Policies (SCWP), Rapidly
Changing World with Stabilizing Policies
(RCWP), and Rapidly Changing World with
Rapid Emissions Reductions (RCWR), start
with the same economic and demographic
assumptions used in the SCW and RCW
scenarios, respectively, but assume that
government leadership is provided to ensure
that limiting greenhouse gas emissions
becomes a consideration in investment
decisions beginning in the 1990s. We assume
that policies to promote energy efficiency in
all sectors succeed in substantially reducing
energy demand relative to the No Response
scenarios, and that because of efforts to
expand the use of natural gas, its share of
primary energy supply increases relative to
other fossil fuels in the near term. Research
and development into non-fossil energy supply
options such as photovoltaics (solar cells) and
biomass-derived fuels (fuels made from plant
material) assure that these options are
available and begin to become competitive
after 2000. In addition, the RCWR case
VI-IO
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Chapter VI: Thinking About the Future
TABLE 6-2
Economic Growth Assumptions
(percent per year)
US & OECD
USSR &
Eastern Europe
Centrally
Planned Asia
Other Developing
Countries
World
1965-1975
3.9
6.2
7.0
5.6
4.4
1975-1985
2.8
NA
7.8
3.2
2.9*
Slowly Changing World
1985-2025 2025-2100
1.7
2.2
3.2
2.7
2.0
1.0
1.6
2.5
2.1
1.5
Rapidly Changing World
1985-2025 2025-2 10(
2.7
4.3
5.1
4.5
3.4
1.5
2.6
4.0
3.3
2.6
Excludes USSR and Eastern Europe,
Source: Historical rates taken from IMF, 1988. Assumptions derived from World Bank, 1987.
VI-11
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Policy Options for Stabilizing Global Climate
14
12
10
FIGURE 6-3
POPULATION BY REGION
Slowly Changing World
/////
\V\\\ \ X \\\\\\\\\\\\
Other Developing
S ft. SE Asia
China A CP Asia
USSR * E. Europe
Other OECD
United State*
1986 2000
202S
2060
2076
2100
Rapidly Changing World
\ X \ \ X X \ \ X \ \ X XX X XXX
Other Developing
SASEAsia
China * CP Aela
USSR * E. Europe
Other OECD
United State*
1986 2000
2026
2060
2076
2100
Year
Source*: U.S. Bureau of the Census, 1987; Zacnarlah and Vu, 1988.
VI-12
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Chapter VI: Thinking About the Future
considers the imposition of even more
aggressive policies (compared to the RCWP
case) such as a substantial carbon emission fee
and rapid reforestation. In all three scenarios,
non-fossil energy sources meet a substantial
fraction of total demand in later periods. The
Montreal Protocol to reduce CFC emissions is
assumed to be strengthened, leading to a
phaseout of fully halogenated compounds and
a freeze on methyl chloroform. A global effort
to reverse deforestation transforms the
biosphere from a source to a sink for carbon,
and technological innovation and controls
reduce agricultural, industrial, and
transportation emissions of greenhouse gases.
While the general policy assumptions
apply to the SCWP, RCWP, and RCWR cases,
the degree and speed of improvement are
higher in the Rapidly Changing variants
because technological innovation and capital
stock replacement are greater in these cases.
In the long time frame of our analysis,
lifestyles will certainly change, although the
policies we consider do not restrict basic living
patterns. For example, energy use in buildings
is greatly reduced in the Stabilizing Policy
scenarios relative to the No Response
scenarios, but the floor space available per
person and the amenity levels provided are
assumed to be the same. The technological
strategies available to achieve the Stabilizing
Policy scenarios were discussed in detail in
Chapter V; the policy options for
implementing these strategies will be examined
in Chapters VII and VIII.
The fourth policy case considers a
Rapidly Changing World with Accelerated
Emissions (RCWA). In this scenario, not only
are concerns over climate change ignored, but
other policies adopted actually exacerbate the
buildup of greenhouse gas emissions. For
example, current U.S. energy policy is to
increase coal production and use, reduce
dependence on imported oil, and boost
employment; the U.S. Department of Energy
(U.S. DOE) has made numerous suggestions
concerning various policies to increase the role
of coal in relative and absolute terms (U.S.
DOE, 1988; National Coal Council, 1987; see
Figure 6-4). Furthermore, recent initiatives in
utility regulation and alternative fuels may also
increase greenhouse gas emissions.
Improving the efficiency of coal
combustion in so-called "clean coal"
technologies may reduce greenhouse gas
emissions relative to the current generation of
coal-burning plants. Over the long run,
however, more efficient coal-burning
technologies may increase greenhouse gas
emissions by making coal economically
attractive relative to other fuels. (This
proposition is tested in the modeling analysis
presented below.) Numerous policy proposals
have also been made to increase U.S. coal
exports in order to improve the balance of
trade. A recent proposal by the U.S. DOE
coal advisory committee would link exports of
clean-coal technology to an agreement to
purchase U.S. coal, a policy that might slow
the adoption of more efficient technology for
burning less expensive domestic coal in some
developing countries like China (National
Coal Council, 1987).
The need to consider more carefully the
potential impact of government decisions on
greenhouse warming is evident from analyses
of two recent policies with ambiguous impacts
on greenhouse warming. The Alternative
Motor Fuels Act of 1988 (Public Law 100-494)
creates incentives for auto manufacturers to
produce vehicles powered by methanol,
ethanol, and substitutes for gasoline. This
program was adopted to lessen dependence on
imported oil and to improve urban air quality.
During Congressional debates, however,
concern was expressed that if methanol were
produced in large quantities from coal, the
result would be a significant increase in
greenhouse gas emissions. Congress therefore
included a provision for study of this
relationship. (The potential effect of
accelerated synthetic fuels development is
presented below.)
Another example of a policy with
ambiguous, but potentially significant, effects
on greenhouse gas emissions is rule changes
proposed by the Federal Energy Regulatory
Commission (FERC) to facilitate non-utility
power production. The draft environmental
impact statement on these rules concluded
that coal-fired technologies have, so far, played
a limited role in the development of
independent power projects relative to
resource recovery, hydroelectric power, and
natural gas. As a result of the FERC
VM3
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Policy Options for Stabilizing Global Climate
FIGURE 6-4
ACTUAL AND PROJECTED U.S. COAL PRODUCTION
(Million Metric Tons)
1200
1000
5 800
o
9
£
i
600 -
400 c
200
Actual
Projected /Exports
U.S.
Consumption
1960 1965 1970 1975 1980 1985 1990 1995 2000
Year
Source: EIA, 1987.
VI-14
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Chapter VI: Thinking About the Future
proposals, coal could assume a much larger
role in future non-utility power production
because (1) cogeneration requirements that are
typically incompatible with the most economic
coal technologies would be eliminated, and (2)
larger firms that have the resources necessary
to undertake large-scale coal projects would
find the electric power market more attractive.
Alternative assumptions, however, imply
natural gas use will grow much more than coal
(FERC, 1988).
ANALYTICAL FRAMEWORK
To make it possible to assess the
implications of the kinds of scenarios just
described, we have developed an integrated
analytical framework to organize the data and
assumptions required to calculate emissions of
radiatively and chemically active gases,
concentrations of greenhouse gases, and the
rate of temperature change. This framework
is described very briefly here, and in more
detail in Appendix A and 1CF (1989).
The analytical framework consists of
four emissions modules and two concentration
modules as shown in Figure 6-5. The four
emissions modules use input data, including
scenario specifications for population growth,
GNP, energy efficiency, etc., to estimate
emissions of greenhouse gases for nine regions
of the globe (see Figure 6-6). Emissions are
calculated every 5 years from 1985 to 2025 and
then every 25 years through 2100. Emissions
of the greenhouse gases CO2, CH4, N2O, and
numerous CFCs are explicitly calculated within
the framework. Emissions of carbon monoxide
(CO) and nitrogen oxides (NOxy which are
not themselves greenhouse gases, are also
explicitly calculated, since these gases can
significantly alter the chemistry of the
atmosphere and thus affect the concentrations
of the greenhouse gases. The concentrations
of other greenhouse gases, such as water vapor
and ozone, are calculated implicitly, or
explicitly, as a function of the other gases.
The atmospheric composition and ocean
modules together estimate global concentra-
tions of the greenhouse gases resulting from
the projected emissions and increases in global
temperatures resulting from the calculated
concentrations. The atmospheric trace-gas
concentrations and temperatures affect the
emissions and concentration modules in the
next time period.
Energy Module
The energy module consists of a Global
Energy Supply Model (SUPPLY), which is
based on the energy-CO2 model of Edmonds
and Reilly (1983a, 1984) and was developed by
ICF Inc. for this study; a global energy end-use
analysis (DEMAND), conducted by the World
Resources Institute and Lawrence Berkeley
Laboratory; and combustion emission
coefficients developed by Radian Corporation
(1987).
DEMAND estimates energy
consumption based on specific assumptions
about the level of energy-using activities and
technical efficiency by region and sector (i.e.,
industry, transportation, buildings). Although
this analysis provided more detail than most
previous global studies, this level of
aggregation obscures many important
variations, particularly for developing
countries. For example, per capita incomes
vary from S150 for Bangladesh to S7000 for
Singapore within the South and East Asia
region. The share of energy used by the
manufacturing sector, vehicle ownership levels,
and types of fuels used (particularly the
importance of biofuels), all vary from one
economy to another. In conducting the
analysis, we capture some of this diversity by
examining energy use by region and by income
group within regions. For the first four
scenarios, detailed analysis was performed for
2025 to anchor the demand estimates
calculated for other years using SUPPLY. The
RCWR and RCWA scenarios were analyzed
using more aggregated assumptions in
SUPPLY, as variants of the RCWP and RCW
scenarios, respectively.
SUPPLY includes estimates of energy
resources and costs by region and can balance
supply and demand using a highly aggregated
estimate of demand as a function of price and
income. Supply-demand equilibration takes
place within SUPPLY, which projects fuel mix
and final prices. Trace-gas emissions are
calculated by allocating the final fuel
VMS
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Policy Options for Stabilizing Global Climate
FIGURE 6-5
STRUCTURE OF THE ATMOSPHERIC STABILIZATION FRAMEWORK
Inputs
Base case
Assumptions
Resources
Population
Growth
Productivity
Technology
Alternative !
Strategies
Emissions
Forecasting
Modules
Energy
Industry
—
Concentration
Determination
Modules
Atmospheric
Composition
Ocean
Feedbacks
Outputs
Atmospheric
Concentrations
and
Temperature
Change
VI-16
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Chapter VI: Thinking About the Future
FIGURE 6-6
GEOPOLITICAL REGIONS OF CLIMATE ANALYSES
KEY:
1. United States
2. OECD Europe/Canada
3. OECD Pacific
4. USSR/Centrally Planned Europe
5. Centrally Planned Asia
6. Middle East
7. Africa
8. Latin America
9. South and Easl Asia
Souro: Adapted from Edmonds & R«My, 1983a. In Mnucr. 1988.
VI-17
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Policy Options for Stabilizing Global Climate
technologies for which emission coefficients
are available. Additional emissions associated
with fuel production are also estimated.
Industry Module
The industry module consists of a CFC
model and a model for other non-combustion,
industrial trace-gas sources. The CFC model
was developed by U.S. EPA for use in
assessing stratospheric ozone depletion (U.S.
EPA, 1987). It projects production and
emissions of the following compounds: CFC-
11, CFC-12, HCFC-22, CFC-113, CC14,
CH3CC13, CH3C1, CH3Br, CF4> halon 1211,
and halon 1301. Other industrial sources of
trace gases include landfilling and cement
production. Emissions from these activities
are estimated as a simple function of
population and per capita income.
Agriculture Module
The agriculture module uses the
IIASA/IOWA Basic Linked System, or BLS
(Frohberg, 1988), to forecast fertilizer use,
agricultural land use, and agricultural
production. These estimates are used with
emission coefficients derived from the
literature to calculate emissions of N2O from
fertilizer use, CH4 from rice production, CH4
from enteric fermentation in domestic animals,
and emissions of CH4, N2O, NOX, and CO
from the burning of agricultural wastes.
Land-Use and Natural Source Module
This module consists of components
dealing with several land surface processes and
other natural sources of trace gases. The most
important of these is carbon dioxide released
from land-use change, particularly
deforestation, which is projected with the
Marine Biological Laboratory/Terrestrial
Carbon Model, or MBL/TCM (Houghton et
al., 1983), based on assumptions about future
rates of land clearing. Other anthropogenic
emissions related to land clearing, such as a
portion of CO emissions from biomass burning
and N2O emissions from land disturbance, are
scaled based on the CO2 emissions calculated
by the MBL/TCM. Natural emissions of CO,
CH4, N2O, and NOX from sources such as
forest fires, wetlands, soils, oceans, and fresh
water are based on values from the literature
and generally are held constant throughout the
projection period (biogeochemical feedbacks
can be assumed to alter these emissions; see
end of this chapter).
Ocean Module
Ocean uptake of heat and CO2 are
modeled using the Box-Diffusion approach
introduced by Oeschger et al. (1975) as
implemented for the Goddard Institute for
Space Studies general circulation model (GISS
GCM) (Hansen et al., 1984). The ocean
mixing parameter for heat uptake is chosen to
reproduce, as closely as possible, the time
scales obtained in the time-dependent
calculations with the GISS GCM (Hansen et
al., 1988). Alternative values for this
parameter can be used to approximate the
time scales of other approaches to estimating
ocean heat uptake (see end of this chapter).
Alternative ocean model formulations for
CO2, such as the Advective-Diffusive Model of
Bjorkstrom (1979) and the Outcrop-Diffusion
Model of Siegenthaler (1983), are included in
the integrating framework and can be used for
alternative estimates of CO2 uptake. Total
carbon uptake is calibrated using estimates of
historical emissions of CO2 from fossil fuels
(Rotty, 1987a,b) and deforestation (Houghton,
1988). The atmospheric CO2 concentration is
assumed to be 285 parts per million by volume
(ppm) in 1800 and is forced to be equal to the
values obtained at Mauna Loa for the period
of record (1960-1985). The excess flux
required to meet these conditions is calculated
and held constant in the future at the average
value for 1975-1985. Alternative assumptions
are considered in Appendix C.
Atmospheric Composition and Temperature
Module
The atmospheric composition model was
developed for this study (Prather, 1989). It
estimates changes in the concentration of key
atmospheric constituents and the global
radiation balance based on the emissions/
uptake projected by the other modules.
Perturbations to atmospheric chemistry are
incorporated based on first-order (and
occasionally second-order) relationships
derived from more process-based chemical
models and observations. The model is
essentially zero-dimensional, but it
VI-18
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Chapter VI: Thinking About the Future
distinguishes between the northern
hemisphere, southern hemisphere,
troposphere, and stratosphere. Global surface
temperature change is calculated based on the
radiative forcing of the greenhouse gases
derived from Lacis et al. (1981) and
Ramanathan et al. (1985) coupled to heat
uptake by the ocean model using a specified
climate sensitivity parameter. This sensitivity
parameter is set to yield a global equilibrium
temperature increase of 2°C or 4°C when the
CO2 concentration is doubled, reflecting a
central estimate of the range of uncertainty; a
broader range of possibilities is examined later
in this chapter (see CHAPTER III).
Assumptions
Population Growth Rates
The population estimates for the
Rapidly Changing World scenario were
developed from Zachariah and Vu (1988) of
the World Bank; for the Slowly Changing
World scenario, estimates were taken from the
U.S. Bureau of the Census (1987). These two
sources agree quite closely on the size of the
world's population through 2000, then diverge
thereafter due to different assumptions about
the rate at which the global population will
stabilize. Zachariah and Vu (1988) assume
that population growth rates in developing
countries will begin to decline markedly after
2000, achieving a net reproduction rate of
unity in every country by 2040. (A net
reproduction rate of unity indicates that
people of child-bearing age have children at a
replacement rate; it eventually leads to a stable
population level.) U.S. Bureau of the Census
(1987) assumes that global population stability
will occur at a later date, with developing
countries experiencing rapid population
growth rates until the middle of the next
century.
Economic Growth Rates
The primary source for the economic
growth rate estimates was the World Bank
(1987). In their report, Gross Domestic
Product (GDP) forecasts were provided for the
1986-1995 period for several different types of
country groups. Most countries could be
classified into one of these three general
categories: low income, middle income, or
industrialized. In addition, the World Bank
defined several other more select groups for
which separate growth rates were estimated,
including oil exporters, exporters of
manufactured products, highly indebted
countries, and sub-Saharan Africa. The World
Bank's low growth case was used as a starting
point for this analysis because these estimates
were more consistent with recent historical
trends and other forecasts. For the RCW
(SCW) scenario these initial values were
generally increased (decreased) by one
percentage point for developing and Eastern
European countries and by one-half
percentage point for OECD countries to
reflect the greater uncertainty regarding future
growth in developing and centrally-planned
economies. The growth rates were applied for
the period 1985-2000, and were generally
reduced by one-half percentage point each 25-
year period, beginning in 2000, to reflect
structural change and the decline in
population growth rates over time.
Nonetheless, GDP per capita continues to
increase throughout the projection period,
although the rate of growth is substantially
lower in the SCW scenario.
Oil Prices
The oil prices used in this analysis were
taken from EIA (1988), which supplied a
range of oil price forecasts. The Middle Price
forecast from U.S. DOE was used for the
RCW scenario (by 2000 the world oil price is
about $31/barrel in 1987 dollars), while the
Low Price forecast was used for the SCW
scenario (oil prices by 2000 were about
S25/barrel in 1987 dollars). Since the U.S.
DOE price forecasts did not extend beyond
2000, oil prices were derived from the
SUPPLY model; in each scenario prices
escalated about 0.8% annually from 2000 to
2100.
Limitations
This analytical framework attempts to
incorporate some representation of the major
processes that will influence the rate and
magnitude of climate change during the next
century within a structure that is reasonably
transparent and easy to manipulate. In so
doing we recognize a number of major
limitations:
VI-19
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Policy Options for Stabilizing Global Climate
• Economic growth rates are difficult to
forecast. Our alternative assumptions may not
adequately reflect the plausible range of
possibilities. In particular, we have assumed
that aggregate economic growth rates will
generally decline over time from the levels
assumed for 1985-2000; this may not be the
case.
• Economic linkages are not fully
captured. The economic analysis uses a
partial-equilibrium framework, making it
impossible to ensure that the activity levels
assumed in each sector are completely
consistent with the aggregate economic
assumptions. In addition, capital markets are
not explicitly considered. This is particularly
significant in examining developing countries,
as it is unclear if they will be able to obtain
the capital investments needed to develop
the energy supplies assumed in some of the
scenarios.
• Technological changes are difficult to
forecast. Substantial improvements in the
efficiency of energy-using and energy-
producing technologies are assumed to occur
even in the absence of substantial energy price
increases or policy measures. If this
assumption proves to be untrue, then
greenhouse gas emissions may be substantially
underestimated in the No Response and
Accelerated Emissions scenarios. Similarly,
aggressive research and development is
assumed to substantially reduce the cost of
renewable technologies in the Stabilizing
Policy scenarios. The impact of policies may
be overestimated if such improvements fail to
materialize or if they would have materialized
as rapidly even without increased government
support.
• Detailed cost analyses have not been
conducted. Technological strategies have been
screened based on judgments about their
potential cost-effectiveness, but no attempt has
been made to rank the cost-effectiveness of
each strategy or to estimate the government
expenditures or total costs associated with the
stabilizing strategies.
• The modules of the framework are not
fully integrated. Existing models of individual
processes that affect greenhouse gas emissions
were assembled within the analytical
framework and were used with consistent
assumptions. However, it was not possible to
ensure complete consistency of results. For
example, while the biomass energy supplies
arrived at in the Energy module do not appear
to be inconsistent with the land-use patterns
calculated in the Agriculture and Land-Use
and Natural Source modules, there is no
explicit coupling among these results.
• The ocean models employed are highly
simplified. The ocean plays an important role
in absorbing both CO2 and heat. The one-
dimensional models used to represent this
process may not adequately reflect the
underlying physical processes, particularly as
climate changes.
• Changes in atmospheric chemistry are
calculated in a highly simplified fashion.
Chemical interactions are analyzed based on
parameters derived from detailed chemical
models. These parameters may not adequately
reflect the underlying chemistry, particularly as
the atmospheric composition changes
significantly from current conditions. Also, it
is not possible to explicitly model the
heterogeneous conditions that control, for
example, tropospheric ozone concentrations.
In our analysis we also assume that non-
methane hydrocarbon emissions remain
constant, which may cause future methane and
ozone changes to be underestimated.
SCENARIO RESULTS
Using the integrated analytical
framework developed for this study, we have
estimated the implications of the six scenarios
described above for emissions of chemically
and radiatively important trace gases arising
from energy production and use, industrial
processes, changes in land use, and agricultural
activities. The resulting changes in
atmospheric composition and global average
temperature increases are also estimated for
all six scenarios.
Energy Production and Use
The single most important determinant
of greenhouse gas emissions is the level of
energy demand and the combination of sources
that is used to supply that energy. Given the
dominance of fossil fuels as a source of
VI-20
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Chapter VI: Thinking Abou* the Future
greenhouse gas emissions, technologies to
reduce use of fossil fuels must play a central
role in any effort to stabilize concentrations.
Fossil-fuel-based technologies supply over 70%
of global primary energy needs in the No
Response scenarios. A major focus for
policies to reduce emissions, as discussed in
Chapters VII and VIII, must accordingly be to
promote demand-side measures that reduce
total energy demand and supply-side measures
that promote less carbon-intensive fuels.
The No Response scenarios assume that
technological innovation and market forces
will yield substantial efficiency gains. The
range of demand-side measures discussed in
Chapter V illustrates how this assumed
efficiency improvement might occur, as well as
improvements incorporated into the Stabilizing
Policy scenarios.
End-Use Consumption
Government policies that affect demand
for energy are likely to be the most important
determinant of greenhouse gas emissions in
the near term. Figure 6-7 illustrates global
end-use energy consumption by region. Total
end-use energy consumption increases from
227xl018 joules (227 EJ) in 1985 to 344 EJ in
2025 in the SCW versus 458 EJ in the RCW.3
Greater improvements in energy efficiency in
the SCWP, RCWP, and RCWR cases reduce
end-use demand in 2025 by 15%, 22%, and
27%, respectively, relative to the No Response
scenarios; smaller improvements .in energy
efficiency in the RCWA case increase end-use
demand in 2025 by 35%. Extrapolating these
trends to 2100 yields 429 EJ in the SCW and
850 EJ in the RCW scenarios, while in the
Stabilizing Policy cases there is 21%, 42%, and
45% lower demand, respectively; in the
RCWA case, end-use demand is 67% higher
compared to the RCW case.
In each scenario, the growth in end-use
demand is driven almost entirely by countries
outside the OECD (USSR, Eastern Europe,
China, and other developing countries) as a
result of higher rates of economic and
population growth in these regions and of
more rapid efficiency improvements and the
saturation of energy-intensive technologies in
the OECD (e.g., steel production, automobile
transportation, and central heating). Fuel use,
in particular, is not expected to grow
significantly in the U.S. and other OECD
countries as efficiency gains compensate for
increases in floor space, mobility, and
production. Electricity use is projected to
grow much more rapidly than fuel use in all
cases, and significant increases in OECD
electricity demand are reflected in the RCW.
It is important to note that both the
SCW and RCW scenarios assume substantial
efficiency gains due to technological
innovation and market forces. For example,
fuel use per square meter of residential and
commercial floor space is assumed to fall by
45-55% in the United States and Western
Europe by 2025. Similarly, fleet average fuel
efficiency of U.S. cars and light trucks reaches
7.8 and 6.9 liters per 100 kilometers (liters/100
km), or 30 and 34 miles per gallon (mpg), in
the SCW and RCW scenarios, respectively. In
the SCW, industrial energy use per unit of
GNP falls by 1.5-2%/yr in the industrialized
countries, in accordance with recent trends.
This rate accelerates to 2-3.5%/yr in the RCW,
the highest rate of improvement stemming
from the USSR and Eastern European
countries as they have the highest initial
industrial energy intensities. Less optimistic
assumptions about efficiency gains in the No
Response scenarios would imply higher rates
of associated temperature rise as shown by the
RCWA scenario and greater relative
improvement in the Stabilizing Policy
scenarios.
In developing countries, the use of
biofuels for cooking is strongly influenced by
urbanization and the efficiency with which
these fuels are used. Urban populations have
better access to modern fuels, and thus, a
smaller share of urban households will use
traditional fuels. There is substantial scope
for improvement in the efficiency of biomass
use. Laboratory experiments in Asia with
improved cookstoves suggest that it is possible
to achieve efficiencies of up to 33% (compared
with current averages of 8%). However,
experience from the last decade of improved
cookstove dissemination projects suggests that
efficiencies are unlikely to exceed 20% in the
field. We assume the dissemination of
efficient cookstoves to almost all users of
biomass only in the Stabilizing Policy cases.
Thus, the average efficiency of biomass use is
VI-21
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Policy Options for Stabilizing Global Climate
FIGURE 6-7
END-USE ENERGY DEMAND BY REGION
1400 p
sew
I
• too
xxxxxxxxxxxxx
SCWP
Other Develop**
CKMtCPU*
UStt 4 CP Eurepe
Other Of CO
IMtM ttttM
RCWP
Other Developing
1 China ft CP A«t«
USSR I CP Europ*
Othv OECD
UMtM It.t.I
RCWR
2078 2100
Other Developing
China 4 CP Atii
USSR It CP Europ*
Other OECO
Unned States
20TS 2100
Vl-22
-------
Chapter VI: Thinking About the Future
assumed to improve to 15-17% in each region
in these scenarios. As a result of these
efficiency improvements and because an
increasingly larger share of the population is
assumed to move to urban areas where there
is better access to modern fuels, the amount of
biofuels consumption declines in the
household sector for each scenario.
Important structural shifts underlie the
aggregate trends in these scenarios.
Electricity's share of end-use consumption
more than doubles in the RCW, from 14% in
1985 to 19% in 2025 and 30% in 2100, while
it grows less dramatically in the SCW, reaching
21% in 2100. These trends are accentuated in
the policy scenarios, as there appears to be
even greater room for reductions in fuel use
than in electricity use, partly because
electricity is substituted for fuel in some highly
efficient applications. For example, electricity
accounts for 33% of end-use consumption by
2100 in the RCWP scenario because of
dramatic increases in electricity use in
developing countries. The distribution of
energy use among the industrial,
transportation, and residential and commercial
sectors also shifts. In the RCW, the share of
end-use energy going to the residential and
commercial sectors declines slightly, then
increases as the share going to industry
increases until the middle of the 21st century
and then declines. This pattern reflects the
increasing importance of developing countries,
which currently have low heating demands and
a greater percentage of modern energy devoted
to the industrial sector, but whose share of
residential and commercial energy demands
increases as incomes rise and industrialization
proceeds. As the most intense phase of
industrialization is completed, the
transportation sector begins to take off, its
share rising steadily after 2050. In the SCW
scenario, the share of end-use energy
consumed in the industrial sector grows less
dramatically and does not peak until 2050,
since industrialization in developing countries
is stretched out over a longer time-span and
dramatic increases in mobility are delayed. In
the Stabilizing Policy scenarios, the gro-vth in
transportation energy use is suppressed by
much higher fuel efficiency, and the share of
end-use energy going to the residential and
commercial sectors increases slightly toward
the end of the next century.
Primary Energy Supply
While policies affecting demand will
have the largest impact on near-term
greenhouse gas emissions, changes in the
supply mix will also be very important over the
long term. Global primary energy supply by
source under the six scenarios is shown in
Figures 6-8 (exajoules per year) and 6-9
(percent share). Growth in primary energy
production is substantially higher than growth
in end-use energy consumption because of
increased requirements for electricity and
synthetic fuel production. For example, in the
RCW scenario primary energy production
increases from 300 EJ in 1985 to 650 EJ in
2025 and 1485 EJ in 2100, a 115% and 395%
increase, respectively, compared with 100%
and 275% increases in end-use consumption.
In the RCWA scenario these increases are
even more dramatic, with primary energy
production increasing to 970 EJ in 2025 and
2595 EJ in 2100, increases of 225% and 765%,
respectively, compared with increases in end-
use consumption of 170% and 525%.
The use of synthetic fuels to supplement
conventional oil and gas production becomes
particularly important after 2025, influencing
both total requirements and the mix of sources
(see Figure 6-10). In the RCW, conventional
oil production and gas production increase
through 2025 and 2050, respectively, then
begin to decline due to resource depletion (the
share of primary energy supplied by oil and
gas declines throughout the projection period).
As a result, synthetic fuels are increasingly
relied on to supply liquid and gaseous fuel
requirements. By 2050,19% of primary energy
is used in synthetic fuel production, and this
value increases to 39% by 2100. In the SCW
heavy dependence on synthetic fuels begins
later because conventional oil and gas
resources are depleted more gradually. Coal is
the dominant feedstock for synfuel production
in both of these scenarios.
The mix of primary energy resources
used to generate electricity is also crucial in
determining future greenhouse gas emissions.
While non-fossil energy sources (nuclear, solar,
and hydro) increase their absolute contribution
to primary energy supply in all scenarios, in
the absence of policies to limit greenhouse gas
emissions, it is likely that future electricity
VI-23
-------
Policy Options for Stabilizing Global Climate
FIGURE 6-8
PRIMARY ENERGY SUPPLY BY TYPE
SCWP
Hydro
Gu
1M6 2000 2025 20<0 2078 2100
Not*: Seal* is diff *r*nt for th» RCWA cast.
IMS 2000
2028 2030 2076 2100
V»«r
Vl-24
-------
Chapter VI: Thinking About the Future
FIGURE 6-9
SHARE OF PRIMARY ENERGY SUPPLY BY TYPE
sew
SCWP
100
100
Biomats
BlomiM
Biomitt
1986 2000 2025 2060 2076 2100
Y»«r
1*862000 2026 2060 2076 2100
Y»«r
VI-25
-------
Policy Options for Stabilizing Global Climate
FIGURE 6-10
ENERGY DEMAND FOR SYNTHETIC FUEL PRODUCTION
600
600
600
400
300
200
100
0
600
500
400
300
200
100
0
600
SOO
400
300
200 -
100
SCWP
Biotnui
Coil
BCWP
RCWR
2025 2050 2100
Y*«r
Not*: Seal* !• different for th* RCWA c«»*.
2025
2050
Y*«r
2100
VI-26
-------
Chapter VI: Thinking About the Future
production will be dominated by coal-based
technologies over the long term (in the near
term, current gas prices make gas-based
combustion turbine technology very attractive
in many regions). Thus, in the RCW, demand
for electricity and synfuel production pushes
global coal consumption up by more than a
factor of ten between 1985 and 2100. In the
RCWA coal consumption by 2100 is nearly 25
times higher than 1985 levels; correspondingly,
the share of primary energy supplied by coal
increases, for example, in the RCW from 29%
in 1985 to 42% in 2025 and 63% in 2100 (see
Figure 6-9). The same forces are at work in
the SCW, but the results are less dramatic.
Coal production increases by less than a factor
of four, and its share of primary energy
reaches just over 50% by 2100 in the SCW
scenario.
In the Stabilizing Policy scenarios,
natural gas is relied on more heavily in the
near term while accelerated research and
development and other incentives are assumed
to make several non-fossil electricity supply
technologies strongly competitive over the
long term. In particular, photovoltaics,
biomass-based combustion turbines, and
advanced nuclear reactors appear to be strong
candidates to make a large contribution to
future electricity production (these and other
options were discussed in some detail in
Chapter V). In the policy scenarios, these
technologies begin to supply energy after 2000
and become strongly competitive by 2025. By
2050 they supply 54%, 62%, and 64% of
global electricity in the SCWP, RCWP, and
RCWR scenarios, respectively.4
It is also assumed that research
priorities and other policies will promote the
use of biomass-derived fuels rather than coal-
based synfuels. In fact, in 2025 and 2050 total
synfuel production is higher in the policy
scenarios because biomass production and
conversion is assumed to become competitive
with imported oil and gas in many developing
regions starting around 2010 (Walter, 1988).
The particular mix among the non-fossil
supply technologies shown in Figure 6-9 is
rather arbitrary, but the type of non-fossil
technologies is of little consequence to total
greenhouse gas emissions.
Greenhouse Gas Emissions From Energy
Production and Use
The heavy reliance on coal in the SCW,
RCW, and RCWA scenarios leads to large
increases in both CO2 and CH4 emissions (see
Figures 6-13 and 6-15 later in the chapter). In
the SCW scenario energy-related emissions of
CO2 increase from 5.1 petagrams of carbon
(Pg C) in 1985 to 7.6 Pg C in 2025 and 10.4
Pg C in 2100.5 Emissions ultimately reach
more than twice this level in the RCW
scenario: 11.2 and 25.0 Pg C in 2025 and 2100,
respectively. In the RCWA, emissions are
even higher: 19.8 Pg C in 2025 and 54.4 Pg in
2100 (see Table 6-3). This growth in
emissions of 0.6 Pg C per decade in the SCW,
1.5 Pg C per decade in the RCW, and 3.8 Pg
C per decade in the RCWA between 1985 and
2025 compares with the average growth of 1.1
Pg C per decade between 1950 and 1980.
Emissions of CH4 from fuel production,
predominantly coal mining, grow even more
dramatically. The estimated emissions from
fuel production in 1985 are 60 teragrams of
CH4 (Tg CH4), or just over 10% of the
total.6 In the SCW estimated emissions from
this source increase to 98 Tg CH4 in 2025 and
154 Tg CH4 in 2100. The corresponding
values for the RCW are 152 Tg CH4 in 2025
and 389 Tg CH4 in 2100, about 21% and 35%
of the CH4 total, respectively. In the RCWA,
emissions from fuel production are 307 Tg
CH4 in 2025 and 855 Tg CH4 in 2100, about
34% and 54% of the CH4 total, respectively.
The combination of higher efficiency
and greater reliance on non-fossil fuels
assumed in the Stabilizing Policy scenarios
serves to substantially curtail CO2 and CH4
emissions. In the SCWP and RCWP cases,
CO2 emissions from energy use reach only 5.6
and 5.9 Pg C in 2000, after which time they
decrease, reaching 2.6 and 5.2 Pg C by 2100 in
the two cases, respectively. In the RCWR
case, CO2 emissions from energy use are
reduced even further, to 2.9 Pg C in 2025 and
1.5 Pg C in 2100. Similarly, CH4 emissions
from fuel production increase slightly in the
RCWP, from 60 Tg CH4 in 1985 to 81 Tg CH4
in 2100, while they decline substantially in the
SCWP and RCWR scenarios, to 39 Tg CH4 in
VI-27
-------
Policy Options for Stabilizing Global Climate
TABLE 6-3
Key Global Indicators
Parameter
GNP/capita
(1000 1988 S)
Primary Energy
(EJ)b
Fossil Fuel CO,
(Pg C)c
GNP/capita
(%/yr)
Energy/GNP
(%/yr)
Fossil Fuel
CO,/Energy
(%/Vr)
Scenario3
SCW, SCWP
RCVV, RCWA
RCWP, RCWR
SCW
RCW
RCWA
SCWP
RCWP
RCWR
SCW
RCW
RCWA
SCWP
RCWP
RCWR
SCW, SCWP
RCW, RCWA,
RCWP, RCWR
SCW
RCW
RCWA
SCWP
RCWP
RCWR
SCW
RCW
RCWA
SCWP
RCWP
RCWR
1985
3.0
300
5.1
1985-2025
0.5
2.0
2.0
-1.0
-1.4
-0.4
-1.4
-1.8
-2.1
0.0
0.0
0.4
-0.5
-1.1
-2.6
Year
2025
3.7
6.7
6.7
460
650
970
390
530
520
7.6
11.2
19.8
5.5
5.7
2.9
2100
7.1
35.9
35.9
650
1480
2590
510
850
800
10.4
25.0
54.4
2.6
5.2
1.5
2025-2100
0.9
2.3
2.3
-0.9
-1.5
-13
-1.2
-2.1
-2.0
-0.1
0.0
0.1
-1.4
-0.8
-1.5
a SCW = Slowly Changing World; SCWP = Slowly Changing World with
Stabilizing Policies; RCW = Rapidly Changing World; RCWA = Rapidly
Changing World with Accelerated Emissions; RCWP = Rapidly Changing
World with Stabilizing Policies; RCWR = Rapidly Changing World with
Rapid Emissions Reductions.
b EJ = exajoule; 1 EJ = 0.948 quadrillion Btus.
c Pg C = petagrams of carbon; 1 Pg = 1015 grams.
VI-28
-------
Chapter VI: Thinking About the Future
the SCWP and 19 Tg CH4 in the RCWR by
2100.
Energy-related emissions, other than
CO2 and CH4 emissions, are strongly affected
by the type of control technology employed in
addition to the total amount and type of
energy used. Emissions of CO and NOX
associated with energy use can be expected to
increase almost as rapidly as primary energy
consumption in the absence of new policies.
On the other hand, in the Stabilizing Policy
scenarios NOX emissions are roughly constant,
and CO emissions are cut by more than half.
This assumes that the rest of the world
gradually adopts control technology similar to
that required of new mobile and stationary
sources in the United States today, and that
industrialized countries adopt standards
consistent with the use of Selective Catalytic
Reduction technology in utility and industrial
applications after 2000, with developing
countries following after 2025.
Comparison to Previous Studies
Despite the large range of outcomes
illustrated by the six scenarios developed here,
none of the global rates of change are
unprecedented (see Table 6-3). Global
reductions in aggregate energy intensity
generally fall within the range of 1-2% per
year; the lower value is consistent with long-
term trends, and the higher value is consistent
with recent experience. Changes in the
amount of carbon emitted per unit of energy
consumed (carbon intensity) between 1985 and
2025 vary from an increase of 0.4% per year in
the RCWA to a decrease of 2.6% per year in
the RCWR with significant declines apparent
only in the Stabilizing Policy cases. The larger
reductions in the Stabilizing Policy cases (up
to 1.4% per year) may be difficult to achieve,
but they are not unprecedented: carbon
intensity declined by an average of 1.5% per
year between 1925 and 1985 because of
increased reliance on oil and gas over coal.
The reduction in carbon intensity of 2.6% per
year implied by the RCWR scenario is the
most ambitious scenario.
While we know of no previous attempts
to develop long-term scenarios for emissions
of the full set of gases discussed above based
on explicit economic and technological
assumptions, there have been a number of
previous studies that relate to many of the
components examined here. Over the last
decade there have been many studies of U.S.
energy futures that can be compared to our
U.S. results. In addition, there have been
several recent studies of long-term global
energy use and CO2 emissions (see CHAPTER
I). One recent study developed "conventional
wisdom reference scenarios" for CH4, CO,
NOX, and N2O emissions related to major
energy sources (Darmstadter et al., 1987).
This section compares the scenarios presented
here to those developed in previous work.
Since the OPEC oil embargo focused
the world's attention on energy in 1973,
numerous studies have examined the future of
energy supply and demand in the United
States. Those analyses contain much more
detail, particularly in the short term, than is
possible in this study, as our focus is
necessarily global and long term. Nonetheless,
it is useful to compare the results of this study
for the U.S. with selected previous work. The
National Energy Policy Plan (NEPP) prepared
by the U.S. Department of Energy (U.S. DOE,
1988) and Energy for a Sustainable World
(ESW), an international study supported by
the World Resources Institute (Goldemberg et
al., 1985, 1987, 1988) are examples of two
important recent studies.
The results of these studies for the
United States are summarized and compared
with our scenarios in Tables 6-4 and 6-5. A
key point is that both the SCW and RCW No
Response scenarios developed here
incorporate lower growth in energy use and
CO2 emissions than is projected in the NEPP
reference and NEPP High-Efficiency cases.
The largest discrepancies are in demand for
electricity and consumption of coal, although
all energy sources, other than gas, and all
sectors show higher consumption in the NEPP
projections. The NEPP Reference Case
projects an increase of over 45% in U.S. CO2
emissions between 1985 and 2010, while the
High Efficiency case produces about a 20%
increase. By contrast, the RCW scenario,
which has GNP assumptions similar to those
used in NEPP, estimates about a 20% increase
in CO2 emissions, while the SCW scenario
predicts essentially flat emissions. In fact, the
RCWA scenario is most similar to the NEPP
Vi-29
-------
Policy Options for Stabilizing Global Climate
TABLE 6-4
Comparison of No Response Scenarios and NEPP: Year 2010
U.S.
End-Use Energy Demand
fexaioules')
Estimates for 2010
Sector
Residential/Commercial Fuel
Electricity
Transport Fuel
Electricity
Industry Fuel
Electricity
Total Fuel
Electricity
1985
11
5
21
0
16
3
48
8
SCW
12
7
22
0
18
4
52
11
RCW" RCWAC
12 14
8 9
21 22
0 0
21 24
4 5
53 60
12 15
NEPP-RC"
13
9
23
0
26
7
62
15
NEPP-HE*
19f
-
22
0
28f
55
13
U.S. Primary Energy Consumption
(exaioules)
Primary Energy
Coal
Oil
Gas
Other*
Total
1985
18
30
19
8
75
SCW
21
31
22
9
84
Estimates
RCW RCWA
26 41
30 30
23 26
11 8
91 106
for 2010
NEPP-RC
38
35
19
22
114
NEPP-HE
31
33
17
20
101
U.S. Carbon Dioxide Emissions
(Detaerams of carbonl
Estimates for 2010
CO,
1985
1.3
SCW
1.4
RCW RCWA
1.6 2.0
NEPP-RC
1.9
NEPP-HE
1.6
a Slowly Changing World scenario.
b Rapidly Changing World scenario.
c Rapidly Changing World with Accelerated Emissions scenario.
d National Energy Policy Plan (NEPP) Reference Case (U.S. DOE, 1988)
* National Energy Policy Plan (NEPP) High Efficiency Case (U.S. DOE, 1988)
f Fuel + Electricity. Separate values not given.
* Excludes dispersed wood.
VI-30
-------
Chapter VI: Thinking About the Future
TABLE 6-5
Comparison of Stabilizing Policy Scenarios and ESVV: Year 2020
U.S. End-Use Energy Demand
(exaioules")
Sector
Residential/Commercial Fuel
Electricity
Transport Fuel
Electricity
Industry Fuel
Electricity
Total Fuel
Electricity
1985
11
5
21
0
16
3
48
8
SCWPa
10
6
17
0
14
3
40
10
U.S
RCWP"
8
6
13
0
16
4
37
10
. Primary
Estimates
RCWRC
6
5
10
0
16
4
33
9
for 2020
ESW-Sd
5
4
12
0
14
5
31
9
ESW-R'
5
4
14
0
15
5
34
9
Energy Consumption
(exajoules)
Estimates for 2020
Primary Energy
Coal
Oil
Gas
Other8
Total
1985
18
30
19
8
75
SCWP
12
25
19
13
68
U.S.
RCWP
10
19
20
17
67
RCWR
4
14
19
24
62
ESW-S
11
13f
13f
14
52
ESW-R
3
14f
14f
14
56
Carbon Dioxide Emissions
(petaerams of carbon)
CO2
1985
1.3
SCWP
1.0
RCWP
0.9
Estimates
RCWR
0.6
for 2020
ESW-S
0.7
ESW-R
0.8
1 Slowly Changing World with Stabilizing Policies.
b Rapidly Changing World with Stabilizing Policies.
c Rapidly Changing World with Rapid Emissions Reductions.
d Energy for a Sustainable World, Goldemberg et al., 1987,1988. Assumes a 50% increase in per capita GNP from
1980 to 2020. Note that the SCWP case assumes a 50% increase from 1985 to 2020.
e Energy for a Sustainable World, Goldemberg et al., 1987, 1988. Assumes a 100% increase in per capita GNP
from 1980 to 2020. Note that the RCWP and RCWR cases assume a 120% increase from 1985 to 2020.
1 Given as Oil + Gas. A 50% split is assumed following the global supply scenario given by Goldemberg et al.,
1987, 1988.
8 Excludes dispersed wood.
VI-31
-------
Policy Options for Stabilizing Global Climate
Reference case, with energy use and CO2
emissions virtually equal between the two
cases. This similarity illustrates that if the
NEPP reference case had been adopted as one
of our No Response scenarios, the U.S.
contribution to global emissions would have
been substantially higher than what we have
estimated in the SCW and RCW cases, and
the difference between the No Response and
Stabilizing Policy cases would have been
significantly greater.
Comparing lowemissions scenarios, U.S.
energy use is considerably higher in our
Stabilizing Policy cases than in those given in
Energy for a Sustainable World (ES W), except
in the RCWR case, where primary energy
consumption is higher but end-use energy
demand is about equal to the ESW-R case.
The largest differences in consumption are in
the residential and commercial sectors, with
significant differences also in the
transportation sector in the slow-growth cases.
We assume that slower turnover of the
housing stock leads to higher residential and
commercial demand, particularly in the slow-
growth variant, whereas Goldemberg et al.
(1985, 1987, 1988) assume that income does
not affect demand in this sector. Despite
higher energy consumption in our scenarios,
our rapid-growth cases have similar or lower
CO2 emissions due to lower consumption of
coal and heavier reliance on gas and non-fossil
energy sources in the RCWP and RCWR
scenarios compared to the ESW cases.
The global energy use and CO2
emissions calculated for 2050 in the six
scenarios developed here are compared to the
bounding extrapolations discussed in Chapter
IV and the results of selected previous
studies in Table 6-6. With the exception of
the RCWA case, the total energy use derived
in our scenarios falls within the lower end of
the range given by trend extrapolation and
previous analyses. In those studies that
included a "Base Case" that assumed no
implementation of policies to reduce CO2
emissions, the estimated primary energy
demand for the year 2050 ranges from 21 to 52
terawatts (TW).7 This level of energy
demand is approximately 2.2 to 5.5 times the
1985 consumption level of 9.4 TW. The
RCW scenario has total energy demand (29.4
TW) that is quite similar to the Base Case
given by several previous studies, including
Edmonds and Reilly (1984), Seidel and Keyes
(1983), and World Energy Conference (1983).
The Slowly Changing World scenario, with
almost 50% less total energy use in 2050, lies
between the median and 25th percentile non-
zero correlation scenario of Edmonds et al.
(1986) and Reilly et al. (1987). The estimated
uncertainty bounds in the systematic
uncertainty analysis conducted by Edmonds et
al. (1986) are not symmetric; their median
scenario has significantly lower energy use and
CO2 emissions than both the mean of their
results and the result of using the median
values for all model parameters. The
implication is that very high energy-use
scenarios may be much less probable than is
suggested by simply considering the range
given by many studies.
Compared to the energy use estimates,
there is substantially less, though still
considerable, variation in the CO2 emissions
estimates for 2050. None of the studies cited
in Table 6-6 approach, within a factor of four,
the result of exponentially extrapolating the
pre-1973 rates of energy demand growth,
assuming no change in the mix of sources.
This reflects the constraint due to the finite
size of the fossil-fuel resource base (see
CHAPTER IV), which implies that very high
growth in energy consumption would need to
be accompanied by a significant shift away
from fossil fuels (but not before atmospheric
CO2 concentrations reached extraordinarily
high levels). Considering the full range of
values for both energy use and CO2 emissions
represented in Tables 6-4 and 6-5, it does
appear that, as intended, the SCW and RCW
scenarios represent very different but not
extreme possibilities.
While the general agreement found
between this study and previous studies at the
aggregate level may be comforting, substantial
disagreements are possible when the results
are examined more closely. For example, the
global increase in energy demand obtained in
the RCW scenario is the result of little growth
in OECD countries coupled with very vigorous
growth in energy demand in developing
countries. Other scenarios with nearly
identical global demand in 2050 may not
distinguish among regions (e.g., Nordhaus and
Yohe, 1983) or may have a more even pattern
VI-32
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Chapter VI: Thinking About the Future
TABLE 6-6
Summary of Various Global Primary Energy Forecasts
for the Year 2050
Report "Base Case"
(TW)
This Study, No Response and RCWA cases
This Study, Stabilizing Policy and RCWR cases'"1
Trend Extrapolation (see CHAPTER IV)
Darmstadter el al. (1987)
Edmonds and Reilly (1983b)a
Edmonds et al. (1984)
Edmonds et al. (1986); Reilly et al. (1987)b
Goldemberg et al. (1985)a
IIASA (1981)
11 ASA (1983)
Keepin et al. (1986)
Legasov et al. (1984)
Lovins et al. (1981)a
Nordhaus and Yohe (1983)c
Reister (1984)
Rose et al. (1983)a
Seidel and Keyes (1983)a
World Energy Conference (1983)
.
-
35.1
52.2
28.4
21.3
11.2 (2020)
-
26.3
-
42
4.6
30.6
29.9
-
30.0
29.8
Range
(TW)
16.0-51.0
15.2-21.6
10-130
—
17-63
12.7-38.8
11.2-14.8 (2020)
22.4-35.7 (2030)
-
10-35
-
—
18.1-43.1
24.0-41.3
16.3-32.3
—
18.9-29.8
"Base Case"
(Pg C/yr)
.
-
-
22.2
26.3
14.5
7.7
4.6 (2020)
-
9.4
-
13
< 1.0 (2030)
13.9
10.7
-
15
14.4
Range
(Pg C/yr)
7.9-34.6
1.0-5.3
19-240
15.7-26.3
6.8-47.4
4.3-18.7
4.6-5.9 (2020)
10-17 (2030)
2-20
7.2-20.6
9.7-27.1
2.7-15
10-18
10.0-14.4
a Policies to limit CO2 emissions are explicitly considered in some or all of these cases.
b Median, 25th, and 75th percentile, non-zero correlation between parameters.
c Probability weighted mean ± one standard deviation.
Source: Adapted from Keepin et al. (1986). See text, Chapter I, and original sources for further discussion and notes.
VI-33
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Policy Options for Stabilizing Global Climate
of energy demand growth (e.g., Edmonds ei al.,
1984). Similarly, the GNP growth rate
assumed in the RCW scenario is higher than
what was assumed by Seidel and Keyes (1983),
but because higher rates of technical efficiency
improvements were assumed in the RCW case,
energy demand and CO2 emissions are almost
identical in 2050.
The results obtained in the policy
scenarios developed here are most
appropriately compared with the results of
Lovins et ah (1981), Rose et al. (1983), and
Goldemberg et al. (1985, 1987, 1988). These
studies all emphasize the possibility that
increased efficiency of energy use could limit
energy demand and CO2 emissions while
allowing for sustainable economic growth.
They conclude that energy demand in 2050
could be held to between 5 and 16 TW by
supplying energy services with advanced cost-
effective technology that is either available or
nearly commercial today. In these scenarios,
efficiency improvements combined with shifts
in energy supply allow CO2 emissions to be
held at or below today's level, and Lovins et
al. (1981) argue that it is technically feasible to
reduce fossil-fuel CO2 emissions by about 80%
over 50 years. The SCWP, RCWR, and
RCWP scenarios have global energy
consumption of 15,20, and 22 TW respectively
in 2050 -- similar to, but somewhat higher
than, what previous studies suggested was
feasible. Part of this difference may be
explained by the high rate of economic growth
assumed in the RCWP case, and our
assumption that efficiency measures are not
adopted up to their technical potential,
particularly in comparison to Lovins et al.
(1981). The CO2 emissions in the RCWP and
SCWP scenario^ are 10-20% below current
levels, again consistent with some previous
analyses. This result, however, is obtained in
different ways. For example, like the RCWA
case, the lowest CO2 scenario given by Rose et
al. (1983) assumes substantially more
contribution from non-fossil energy sources
than do the other policy scenarios developed
here, while the Goldemberg et al. (1985, 1987,
1988) high-demand scenario has somewhat
more oil and gas and less coal than does the
RCWP case in 2020.
The estimates of energy-related (fossil
fuel and wood use) emissions of CH4, N-,0,
NOX, and CO developed in the RCW and
RCWP scenarios are compared in Table 6-7
with results of a study by Darmstadter et al.
(1987). While the main purpose of their study
was to develop an historical database,
reference values for future emissions are
presented assuming either constant emission
coefficients or coefficients declining by 1% per
year. The emissions calculated with constant
coefficients by Darmstadter et al. (1987)
increase much more rapidly than those
obtained in any of our scenarios. These
differences are not too surprising given our
explicit assumptions regarding technological
change, including increasing penetration of
emission control technologies. The largest
discrepancy is for N2O, reflecting not only our
assumptions regarding technical change, but
also the much higher initial emission
coefficient adopted by Darmstadter et al.
(1987) based on Hao et al. (1987) (see
CHAPTER II). The initial estimate of CO
emissions given by Darmstadter et al. (1987) is
a factor of two lower than ours, probably due
primarily to their extrapolation of the U.S.
emission coefficient for gasoline to the rest of
the world. We have attempted to account for
variations in automobile emission control
technology by region, with most regions having
higher average CO emissions than the U.S.
The closest agreement lies in CH4, probably
because these emissions are directly
proportional to the total quantity of coal and
gas produced and are not assumed to depend
on production technology in our No Response
scenarios.
When Darmstadter et al. (1987) assume
that all emission coefficients decline by 1% per
year, they obtain estimates of NOX emissions
that are similar to those occurring in the RCW
case and CH4 emissions estimates closer to
those obtained in the RCWP case. Their CO
emissions estimate falls between these two
cases. Overall, the RCWP case has
significantly lower emissions than are obtained
by Darmstadter et al. (1987) even when they
decrease their emission coefficients by 1%/yr
for a rull century. This is a result not only
because of the assumptions regarding emission
VI-34
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Chapter VI: Thinking About the Future
TABLE 6-7
Comparison of Energy-Related Trace-Gas Emissions Scenarios
Emissions of Trace Gases
(teragrams)
Trace Gas
CH4
(TgCH4)
NoO
(TgN)
NO*
(TgN)
CO
(TgQ
Scenario
RCW
RCWP
Darmstadter et at. (1987)a
Darmstadier et al. (1987)b
RCW
RCWP
Darmstadter et al. (1987)a
Darmstadter et al. (1987)b
RCW
RCWP
Darmstadter et al. (1987)a
Darmstadter et al. (1987)b
RCW
RCWP
Darmstadter et al. (1987)a
Darmstadter et al. (1987)b
1985/1980
70
63
1.2
4.3
26
20
206
108
2025/2030
164
78
192
117
2.4
1.6
16
9.5
49
32
62
37
354
125
292
177
2075/2080
325
82
432
131
3.8
1.4
57
21
79
24
184
68
653
73
614
226
a Constant emission coefficients.
b Emission coefficients decline 1% per year.
VI-35
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Policy Options for Stabilizing Global Climate
control technology, but also because our policy
scenarios have substantially lower total energy
demand and a very different fuel mix.
Industrial Processes
Halocarbon Emissions
The most important industrial source of
greenhouse gases not directly associated with
energy use is the production and release of
CFCs and halons. In both the SCW and RCW
scenarios, the Montreal Protocol, as
formulated without the June 1990 London
Amendments, is assumed to come into force
and apply throughout the projection period.
This agreement (described in CHAPTERS IV,
VII, and VIII) calls on developed countries to
reduce their emissions of certain CFCs 50%
from 1986 levels by 1998, and to freeze their
use of halons at 1986 levels in approximately
1992. Developing countries with low per
capita consumption, however, are allowed to
increase the use of these compounds for up to
ten years -- as a result, emissions of the
controlled compounds could actually increase
substantially, depending on the number of
countries that participate in the Protocol and
the rate at which use increases in developing
and non-participating nations (Hoffman and
Gibbs, 1988). The London Amendments were
not included because this analysis was
conducted prior to their adoption. The
London Amendments were not included
because this analysis was conducted prior to
their adoption.
For the SCW scenario, we adopt the
assumptions of the Protocol scenario
developed for the Regulatory Impact Analysis
of rules to implement the Montreal Protocol
in the United States (U.S. EPA, 1988).
Namely that, in addition to the U.S., 94% (in
terms of current CFC consumption) of
developed countries and 65% of developing
countries participate in the agreement. In this
scenario the global average annual growth rate
in demand for products and services that
would use CFCs, if they were available, is
approximately 4.0% from 1986 to 2000 and
2.5% from 2000 to 2050 (constant production
is assumed after 2050). Growth in demand is
much higher in certain developing countries,
particularly India and China. These growth
rates are not applied directly to CFC use in
non-participating and developing countries,
however, because it is assumed that shifts in
technology development away from CFCs in
the United States and other participating
countries "rechannel" demand in other
countries as well.8 In the RCW scenario, the
rate of growth in demand was increased 75%
to reflect the higher economic growth rates.
Also, 100% of the developed countries and
75% of the developing countries participate in
the Montreal Protocol. In the RCWA
scenario, we have assumed a low rate of
participation in and compliance with the
Protocol, assumptions similar to those used in
the "low case" analysis in the Regulatory
Impact Analysis (U.S. EPA, 1988). The
SCWP, RCWP, and RCWR scenarios assume
that the Montreal Protocol is strengthened to
produce a complete phaseout of CFCs in
participating countries by 2003.9 This
phaseout assumption is somewhat more
stringent than the phaseout actions required
by the June 1990 London Amendments to the
Montreal Protocol.
A considerable amount of recent
analysis evaluates the potential for further
reducing emissions of CFCs and related
compounds beyond what is required by the
Montreal Protocol (see Hoffman and Gibbs,
1988, or Makhijani et al., 1988). A phaseout
by 2000 appears to be feasible given that
substitutes and alternative technologies now
being developed and tested are expected to
become available over the next decade as a
result of the considerable research currently
underway in response to the Montreal
Protocol.
Figure 6-11 shows the estimates for
emissions of CFC-11, -12, and -113, and
HCFC-22 under the six scenarios. Emissions
change more slowly than production because
a significant portion of each year's production
is "banked" in air conditioners, refrigeration
systems, and closed-cell foams. The model
keeps track of the size of this bank and
estimates the gradual release of these CFCs.
In the SCW scenario, emissions are relatively
constant despite the Protocol's requirement of
a 50% reduction in participating industrialized
countries. After declining to 12% below 1985
levels between 1990 and 2020, emissions of
CFC-11 begin to rise again, reaching 1985
levels by the end of the projection period.
VI-36
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Chapter VI: Thinking About the Future
FIGURE 6-11
EMISSIONS OF MAJOR CFCs
CFC-11
CFC-113
E too
i
J
BCW« J
CFC- 12
A
\
\
. \
'•• \
'•-. v .
•CWf IKCWH
. scwr
1MI JOOO 2011 ZOM 207< 2100
HCFC-22
/ RCW.IKWA.
/ KWf. KCWH
/
I L
1M1 1004 20M
207» 21M
Vl-37
-------
Policy Options for Stabilizing Global Climate
CFC-113 emissions also fall significantly for a
few decades but rise again toward 1985 levels.
CFC-12 emissions never decline to 1985 levels:
they decline by 11% between 1990 and 2015,
reaching a few percent above 1985 values, then
they rise slowly, almost reaching the 1990 peak
levels towards the end of the 21st century.
Emissions of HCFC-22 grow rapidly as the
compound is issued as a substitute for the fully
halogenated species that have the highest
ozone-depletion potential. Although HCFC-
22 has a shorter lifetime and weaker radiative
forcing than the fully halogenated compounds,
it could make a significant contribution to
global warming during the next century
because it is not controlled by the Montreal
Protocol (the London Amendments passed in
June 1990 include a non-binding resolution to
phaseout HCFCs).
In the RCW scenario, higher
consumption growth rates in developing
countries more than compensate for higher
participation and rechanneling rates. CFC-11
emissions decline by no more than 6% below
1985 levels, while CFC-12 and -113 each
increase by more than 25% by 2100.
Emissions of HCFC-22 grow dramatically in
this scenario. In the RCWA case emissions of
all the CFCs increase rapidly until about 2050,
and then flatten out. In the SCWP case
emissions of the fully halogenated compounds
fall by more than 80% from 1985 levels by
2025, which is sufficient to reverse the trend in
concentrations (see Figure 6-16 later in the
chapter). Emission reductions in the RCWP
and RCWR cases are not quite as large, but
the rate of growth in concentrations slows
considerably after 2000. HCFC-22 emissions
are assumed to be the same in the No
Response and Stabilizing Policy cases;
however, these emissions could rise as a result
of a CFC phaseout if chemical substitution is
the primary approach to eliminating CFCs, or
fall, if product substitution and process
redesign are the major approaches (see
CHAPTER V).
Emissions From Landfills and Cement
Other important activities included in
the industrial category are CO2 emissions from
cement production and CH4 emissions from
landfills. The growth of these activities in
developing countries is assumed to be related
to per capita income in a simple fashion,
although growth is curtailed as current per
capita levels in industrialized countries are
approached. The result is a three to fourfold
increase in CO2 emissions from cement in the
SCW and RCW scenarios, respectively, though
emissions remain less than 0.5 Pg C/yr in all
cases. Landfill CH4 emissions increase by
more than fivefold in the RCW, reaching 15%
of the total by 2100. In the policy scenarios,
advanced materials are assumed to reduce the
demand for cement (relative to the No
Response scenarios), while gas recovery
systems and waste reduction policies are
assumed to limit emissions from landfills. The
result is that emissions from cement making
still increase by a factor of two to three, but
CH4 emissions from landfills are held
essentially constant.
Changes in Land Use
Deforestation has been a significant
source of CO2 in the atmosphere over the last
two centuries, as indicated by the
measurements of CO2 concentrations in
Greenland and Antarctic ice, which show that
concentrations began to rise before fossil-fuel
use became significant (see CHAPTER II). If
current trends continue, tropical forests could
be completely eliminated during the next
century, adding significantly to the CO2
emissions from fossil fuels. On the other
hand, efforts are underway to reverse
deforestation; if these afforestation and
reforestation efforts succeed, forests could
become a net sink for atmospheric CO2. The
total amount of carbon that can move in
either direction between the atmosphere and
terrestrial ecosystems is ultimately constrained
by the area of forests available for
deforestation or by the area of land available
to support new forests. The timing and
magnitudes of these carbon fluxes are
determined by the timing and extent of
changes in land use as influenced by local,
national, and international policies.
The causes of deforestation are complex
and vary from country to country. This makes
it difficult to directly tie assumptions about
deforestation rates to the economic and
demographic assumptions of the general
scenarios. Qualitatively, we assume that in a
Slowly Changing World poverty, unsustainable
VI-38
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Chapter VI: Thinking About the Future
agricultural practices, and rapid population
growth lead to continuously increasing
pressure on remaining forests. The rate of
deforestation is assumed to increase from
current levels at the rate of population growth,
and tropical deforestation increases from 11
million hectares per year (Mha/yr) in 1980 to
34 Mha/fyr in 2047, when all the unprotected
forests in Asia are exhausted. By 2078, all
available tropical forests have been cleared. In
a Rapidly Changing World, improved
agricultural practices and the substitution of
modern fuels for traditional uses of wood
could ease the pressure on forests.
Nonetheless, clearing of forest lands for
agriculture, pasture, logging, and speculation
could continue apace, even if small areas are
set aside as biological preserves. In this
scenario tropical deforestation is assumed to
increase very gradually, reaching 15 Mha/yr in
2097, when the unprotected forest areas of
Latin America are exhausted.
In the Stabilizing Policy scenarios, it is
assumed that a combination of policies
succeed in stopping deforestation by 2025,
while about 850 Mha is reforested by 2100.
Only land that once supported forests and is
not intensively cultivated is assumed to be
available for reforestation. These lands
include 85% of the area currently involved in
shifting cultivation (370 Mha) under the
assumption that this practice is replaced by
sustainable low input agriculture (Sanchez and
Benites, 1987) and by planted pasture in Latin
America (100 Mha), which is abandoned and
allowed to support forests again. Of the
reforested land, about 380 Mha of plantations
are established in the tropics (sufficient to
produce the biomass energy requirements of
the RCWP or RCWR case depending on the
productivity increases assumed; see Walter,
1988); the rest of the land absorbs carbon at a
much lower rate but reaches a higher level of
average biomass per hectare since the land is
not routinely harvested.10
The carbon fluxes associated with these
deforestation/reforestation scenarios based on
Hough ton's (1988) low estimates of average
biomass are shown in Figure 6-12. In the
SCW, CO2 emissions from deforestation
increase rapidly from 0.4 Pg C/yr to 2.4 Pg
C/yr in 2046 before the Asian forests are
exhausted. All available Latin American and
African forests are exhausted by 2075, reducing
emissions drastically. Total deforestation
emissions are almost the same in the RCW,
but they are spread out over a longer period.
Annual emissions are close to 1 Pg C/yr from
2000 to 2100. In the Stabilizing Policy
scenarios the biosphere becomes a sink for
carbon by 2000 and reaches its peak
absorption of 0.5 Pg C/yr in 2015. The size of
this sink declines gradually after 2025 as
forests reach their maximum size and extent.
Agricultural Activities
The demand for agricultural products is
a direct function of population but is not
strongly dependent on income levels. Thus,
there are only small differences in demand
between the scenarios as the much higher
incomes largely offset the somewhat lower
populations in the RCW compared with the
SCW. The land area used for rice production,
and thus the methane emissions from this
source, increases by only about 50% by 2100 in
both the SCW and RCW scenarios
(production per hectare increases by 80-
100%). Meat production increases more,
about 125%, as demand rises with income to
some extent. Satisfying the demands of
increasing populations with a finite amount of
land requires more intensive cultivation, and
fertilizer use increases by 160% as a result.
In the Stabilizing Policy scenarios, we
assume that changes in technology and
production methods, not in the demand for
agricultural commodities, could reduce
greenhouse gas emissions per unit of product.
Although the impact of specific technologies
cannot be estimated at present, several
techniques have been identified for reducing
methane emissions associated with rice and
meat production and nitrous oxide emissions
related to the use of fertilizer (see CHAPTER
V). For simplicity, we have assumed that CH4
emissions per unit of rice, meat, and dairy
production decrease by 0.5% per year'
(emissions from animals not used in
commercial meat or dairy production are
assumed to be constant). Emissions of N2O
per unit of nitrogenous fertilizer applied are
also assumed to decrease by 0.5% per year for
each fertilizer type. In addition, fertilizer use
is assumed to shift away from those types with
the highest emissions after 2000. Based on
VI-39
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Policy Options for Stabilizing Global Climate
FIGURE 6-12
COMMISSIONS FROM TROPICAL DEFORESTATION
Global Total
•-0.5
-1
Stabilizing Policy Scenarios
Slowly Changing World Scenario by Region
2100
VI-40
-------
Chapter VI: Thinking About the Future
these assumptions, CH4 emissions from rice
production remain roughly constant until 2075,
after which time they fall by about 20% as the
global population stabilizes. Methane
emissions from domestic animals increase by
40-50% by the middle of the 21st century,
before falling to within about 30% of 1985
levels. Similarly, N2O emissions from fertilizer
use increase from'l.6 to about 3.0 Tg N/yr
between 1985 and 2025 and then decline
slightly.
Total Emissions
Total emissions of the key radia lively
important trace gases, the aggregate of
estimates of the emissions from each activity
discussed above and of natural emissions, are
shown in Table 6-8. Overall, emissions
increase gradually in the SCW scenario and
more dramatically in the RCW, while in the
policy scenarios emissions are reasonably
stable or declining.
In the No Response scenarios, CO2
emissions are projected to increase by a much
greater percentage than emissions of the other
gases. This is because all net CO2 emissions
are assumed to be anthropogenic in origin and
because CO2 is a fundamental product of all
fossil-fuel combustion. In the SCW, increased
deforestation contributes significantly to near-
term growth in CO2 emissions, and total
emissions are relatively constant between 2025
and 2075 as forests are exhausted (see Figure
6-13). In the RCW, CO2 emissions are
dominated by the growth in fossil-fuel
combustion, and total emissions increase by a
factor of three by 2050. In the Stabilizing
Policy scenarios, increased end-use efficiency
and reforestation significantly contribute to
decreased emissions in the near term, while
decreased reliance on fossil fuels in
conjunction with continued improvements in
efficiency allows for further decreases later.
The regional allocation of CO2
emissions shows a rapid increase in the
amount attributed to developing countries in
all scenarios except in the RCWR case (see
Figure 6-14). This share increases from about
35% currently to 55% by 2025, and levels off
at about 60% after 2050 in the RCW. The
developing countries account for a little over
50% of CO-, emissions in the SCW after 2025,
with the share from developing countries,
other than China, decreasing after 2050 as
deforestation emissions decline. China's share
of emissions grows most dramatically in the
Stabilizing Policy scenarios, as deforestation is
eliminated in other developing countries and
China becomes, by far, the world's largest coal
consumer. About 67% of global CO2
emissions are from China and other
developing countries by 2100 in the RCWP
scenario, but only 32% in the SCWP. In the
RCWR scenario, developing countries
contribute virtually no net CO2 emissions as
reforestation and biomass energy production
offset emissions from fossil-fuel use (China's
reliance on fossil fuels makes it the largest
CO2 contributor globally).
The projected increases in CH4
emissions in the No Response and Accelerated
Emissions scenarios are attributable to a
variety of sources (see Figure 6-15). In the
SCW over 50% of the increase between 1985
and 2050 is because of enteric fermentation
and rice cultivation, whereas in the RCW
these sources account for about 40% of the
increase, and the growth in emissions from
fuel production accounts for another 40%. In
the RCWA fuel production accounts for nearly
75% of the growth. In these scenarios,
emissions from landfills increase steadily,
becoming quite significant by the end of the
period. Reduced growth in each component is
responsible for relatively stable CH4 emissions
in the Stabilizing Policy scenarios. The total
increases gradually until 2050 in the RCWP
and declines to near 1985 levels by the end of
the period. In the SCWP, CH4 emissions peak
in 2025, then fall below 1985 levels by 2100.
In the RCWR, emissions peak in 2000, falling
constantly to 90% of 1985 levels by 2100.
Total N2O emissions do not increase
dramatically in the scenarios except in the
RCWA, although we note again that current,
and therefore future, emissions of N2O are
highly uncertain. These uncertainties,
however, do not appear to have a large impact
on the overall rate or magnitude of climate
change in these scenarios (see APPENDIX C).
In the SCW, emissions related to deforestation
and land clearing, as well as fertilizer-induced
emissions, increase significantly through 2025,
and total emissions decline after 2050. In the
RCW, emissions growth is driven mainly by a
VI-41
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Policy Options for Stabilizing Global Climate
TABLE 6-8
Trace Gas Emissions
C02 (Pg C)
sew
RCW
RCWA
SCWP
RCWP
RCWR
N,0 (Tg N)
sew
RCW
RCWA
SCWP
RCWP
RCWR
CH4 (Tg CH4)
sew
RCW
RCWA
SCWP
RCWP
RCWR
NO, (Tg N)
sew
RCW
RCWA
SCWP
RCWP
RCWR
CO (Tg C)
sew
RCW
RCWA
SCWP
RCWP
RCWR
CFC-ll(Gg)
sew
RCW
RCWA
SCWP
RCWP
RCWR
1985
6.0
6.0
6.0
6.0
6.0
6.0
12.5
12.5
12.5
12.5
12.5
12.5
510.7
5 10.7
510.7
510.7
510.7
510.7
54.2
54.2
54.2
54.2
54.2
54.2
505.8
505.8
505.8
505.8
505.8
505.8
278.3
278.3
278.3
278.3
278.3
278.3
2000
7.6
8.1
9.1
5.6
5.9
5.2
14.3
14.2
14.7
12.9
12.9
12.8
581.0
590.1
614.4
528.1
536.7
529.6
61.2
62.4
67.1
51.8
52.9
51.3
610.8
561.7
619.6
366.3
364.5
363.2
310.9
337.6
438.9
295.0
331.4
331.4
2025
9.6
12.4
21.9
5.2
5.4
2.1
16.5
16.1
18.5
13.1
13.3
13.1
687.9
731.9
911.9
544.8
561.2
520.8
71.1
79.2
104.9
47.8
56.1
53.2
825.4
724.6
976.2
289.4
294.2
272.6
260.7
281.2
611.1
42.0
56.0
56.0
2050
9.9
16.9
36.6
4.0
5.3
0.3
17.1
17.2
20.7
13.1
12.9
12.7
748.4
901.1
1,237.6
527.9
567.3
500.2
72.2
95.4
145.3
44.0
47.8
45.5
842.2
885.3
1,197.1
251.5
237.5
225.0
291.6
319.8
995.4
50.4
55.8
55.8
2075
9.6
22.0
50.3
3.3
5.2
0.5
15.8
18.1
21.3
13.0
12.7
12.6
783.9
1,044.5
1,504.0
518.0
548.9
4S4.1
66.7
110.4
174.2
43.9
47.4
46.0
614.1
1,052.3
1,050.1
257.9
232.9
232.7
297.4
327.1
1,056.4
53.5
57.9
57.9
2100
10.7
26.1
54.8
2.6
5.3
0.8
15.6
18.1
22.0
12.8
12.6
12.5
829.7
1,126.1
1,576.9
483.0
524.6
462.7
69.0
121.6
186.8
44.7
48.8
48.1
625.0
1,192.2
1,122.3
254.5
230.3
236.1
297.4
327.1
1,056.4
53.5
57.9
57.9
VI-42
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Chapter VI: Thinking About the Future
TABLE 6-8 (Continued)
Trace Gas Emissions
1985 2000 2025 2050 2075 2100
CFC-12 (Gg)
sew
RCW
RCWA
SCWP
RCWP
RCWR
HCFC-22 (Gg)
sew
RCW
RCWA
SCWP
RCWP
RCWR
CFC-113(G2)
sew
RCW
RCWA
SCWP
RCWP
RCWR
363.8
363.8
363.8
363.8
363.8
363.8
73.8
73.8
73.8
73.8
73.8
73.8
150.5
150.5
150.5
150.5
150.5
150.5
419.5
500.2
614.6
402.9
491.4
491.4
206.1
263.0
263.0
206.1
263.0
263.0
121.3
178.4
248.6
112.7
174.7
174.7
393.5
450.3
857.2
50.6
83.5
83.5
407.0
830.7
830.7
407.0
830.7
830.7
124.2
170.5
371.7
8.8
19.9
19.9
420.0
508.7
1,400.0
64.5
87.9
87.9
754.5
2,425.6
2,425.8
754.5
2,425.8
2,425.8
142.2
1953
618.7
14.0
26.1
26.1
426.5
519.1
1,483.1
68.5
91.2
91.2
879.1
3,124.5
3,124.5
879.1
3,124.5
3,124.5
142.2
195.3
618.7
14.0
26.1
26.1
426.5
519.1
1,483.1
68.5
91.2
91.2
879.1
3,124.5
3,124.5
879.1
3,124.5
3,124.5
142.2
195.3
618.7
14.0
26.1
26.1
VI-43
-------
Policy Options for Stabilizing Global Climate
FIGURE 6-13
CO 2 EMISSIONS BY TYPE
1M6 2000 202* 20*0 2076 21OO
V*«r
Not*: The «eil* It different for the RCWA c«e*.
2!
30
SCWP
RCWP
RCWR
Tropic .1
Tro»teM
DcforMtetMn
IHf 2000 1021 20M 2071 2100
-------
Chapter VI: Thinking About the Future
FIGURE 6-14
C02 EMISSIONS BY REGION
Not*: Sell* it different for th* RCWA end BCWR e*t*i.
VI-45
-------
Policy Options for Stabilizing Global Climate
FIGURE 6-15
CH4 EMISSIONS BY TYPE
RCWR
0 •^^^^^^^^^^^^^^^^^^«"^^^^^^« g
1MI 1000 Mil 20<0 JOTi 1100 IM| 200« «0»« tOM IOT« 2100
VMT YMT
Net*: »eml» It dfff*r»nt for th» BCWA c««».
VI-46
-------
Chapter VI: Thinking About the Future
fourfold increase in fossil-fuel combustion
emissions between 1985 and 2100. Similarly,
in the RCWA fossil-fuel-related emissions
increase ninefold. In the Stabilizing Policy and
RCWR cases, total emissions remain constant
because decreases in emissions per unit of
fertilizer use and fossil-fuel combustion are
assumed and because deforestation is halted.
In the No Response scenarios, emissions
of both NOX and CO increase significantly
through 2050. After 2050 declining emissions
related to deforestation in the SCW
compensate for continued increases in energy-
related emissions. The deforestation
assumptions have a particularly large impact
on CO emissions as deforestation accounts for
40-50% of the total between 2000 and 2050 in
this case. In the RCW, deforestation
emissions are relatively uniform, and both CO
and NOX emissions continue to increase
through 2100. In the RCWA, large increases
in fossil-fuel use increase NOX and CO
emissions significantly through 2100. In the
Stabilizing Policy cases, emission controls
produce relatively stable NOX emissions and
declining CO emissions from fossil-fuel
combustion sources, while deforestation
emissions are eliminated. The result is a
moderate decline in NOX emissions and more
than a 50% cut in CO emissions by 2050.
Atmospheric Concentrations
Figure 6-16 shows concentrations of
greenhouse gases that result from the pattern
of emissions discussed above. Because CO2,
N2O, and CFCs are long-lived in the
atmosphere, their concentrations respond
gradually to changes in emissions. CH4 has an
intermediate lifetime (about 10 years), which
is itself affected by changes in emissions of
CO, NOX, CH4, and other trace gases, so its
atmospheric concentration may respond
rapidly to changes in emission rates of these
gases.
CO2 concentrations reach twice their
pre-industrial levels (570 ppm) in about 2080
in the SCW scenario. This level is reached by
2055 in the RCW, and concentrations more
than three times pre-industrial values are
reached by 2100 (see Figure 6-16). In the
RCWA case, CO2 concentrations reach twice
their pre-industrfal levels by 2035 and are
nearly six times higher by 2100. Despite
declining CO2 emissions in the Stabilizing
Policy scenarios, CO2 concentrations continue
to increase throughout the projection period,
reaching about 430 ppm in the SCWP case
and about 475 ppm in the RCWP case by
2100. In the RCWR case, concentrations peak
around 2025 at about 380 ppm, then decline to
about 350 ppm by 2100. It is interesting to
note that the fraction of total CO2 emissions
during the 21st century that remains in the
atmosphere in 2100 is 46% in the RCW case
and 39% in the RCWP case, so that emission
reductions have a more than linear impact on
concentrations.
CH4 concentrations increase by about a
factor of 2 in the SCW and a factor of nearly
2.8 in the RCW, relative to 1985 levels, with
the most rapid growth occurring between 1985
and 2050 (see Figure 6-16). In the RCWA
case, concentrations increase nearly fourfold
between 1985 and 2100. Interestingly, the
2050 concentration obtained in the SCW is
similar to the result of linearly extrapolating
the currently observed growth rate of 1% per
year, whereas the RCW value is close to an
exponential extrapolation of current growth;
the 2100 values lie substantially below a
continuation of such extrapolations for
another 50 years. In the Stabilizing Policy
cases, CH4 concentrations increase by 10-20%
between 1985 and 2025, after which they level
off and decline to roughly 1985 levels by 2100.
In the RCWR case, concentrations decrease
below 1985 levels by 2100. CH4
concentrations are affected by temperature
feedbacks on atmospheric chemistry:
increasing the climate sensitivity of the model
from 2.0°C to 4.0°C reduces concentrations by
65 ppb in the RCWR (the smallest change)
and about 450 ppb in the RCWA (the greatest
change), assuming that emissions are not
affected (see end of chapter).
In contrast to methane, N2O
concentrations increase gradually in all the
scenarios (see Figure 6-16). The concentration
increase between 1985 and 2100 is about 115
parts per billion by volume (ppb) in the SCW,
130 ppb in the RCW, and 185 ppb in the
RCWA. This compares to 70 ppb in the
SCWP and about 65 ppb in the RCWP and
RCWR. Thus, the policy assumptions reduce
the concentration growth by 40-65%.
VI-47
-------
Policy Options for Stabilizing Global Climate
FIGURE 6-15
CH4 EMISSIONS BY TYPE
RCWR
207> I100
I07( 1100
Not*: Seal* li dlff*r*nt for th» BCWA c«»».
VI-46
-------
Chapter VI: Thinking About the Future
fourfold increase in fossil-fuel combustion
emissions between 1985 and 2100. Similarly,
in the RCWA fossil-fuel-related emissions
increase ninefold. In the Stabilizing Policy and
RCWR cases, total emissions remain constant
because decreases in emissions per unit of
fertilizer use and fossil-fuel combustion are
assumed and because deforestation is halted.
In the No Response scenarios, emissions
of both NOX and CO increase significantly
through 2050. After 2050 declining emissions
related to deforestation in the SCW
compensate for continued increases in energy-
related emissions. The deforestation
assumptions have a particularly large impact
on CO emissions as deforestation accounts for
40-50% of the total between 2000 and 2050 in
this case. In the RCW, deforestation
emissions are relatively uniform, and both CO
and NOX emissions continue to increase
through 2100. In the RCWA, large increases
in fossil-fuel use increase NOX and CO
emissions significantly through 2100. In the
Stabilizing Policy cases, emission controls
produce relatively stable NOX emissions and
declining CO emissions from fossil-fuel
combustion sources, while deforestation
emissions are eliminated. The result is a
moderate decline in NOX emissions and more
than a 50% cut in CO emissions by 2050.
Atmospheric Concentrations
Figure 6-16 shows concentrations of
greenhouse gases that result from the pattern
of emissions discussed above. Because CO2,
N2O, and CFCs are long-lived in the
atmosphere, their concentrations respond
gradually to changes in emissions. CH4 has an
intermediate lifetime (about 10 years), which
is itself affected by changes in emissions of
CO, NOX, CH4, and other trace gases, so its
atmospheric concentration may respond
rapidly to changes in emission rates of these
gases.
CO2 concentrations reach twice their
pre-industrial levels (570 ppm) in about 2080
in the SCW scenario. This level is reached by
2055 in the RCW, and concentrations more
than three times pre-industrial values are
reached by 2100 (see Figure 6-16). In the
RCWA case, CO2 concentrations reach twice
their pre-industrfal levels by 2035 and are
nearly six times higher by 2100. Despite
declining CO2 emissions in the Stabilizing
Policy scenarios, CO2 concentrations continue
to increase throughout the projection period,
reaching about 430 ppm in the SCWP case
and about 475 ppm in the RCWP case by
2100. In the RCWR case, concentrations peak
around 2025 at about 380 ppm, then decline to
about 350 ppm by 2100. It is interesting to
note that the fraction of total CO2 emissions
during the 21st century that remains in the
atmosphere in 2100 is 46% in the RCW case
and 39% in the RCWP case, so that emission
reductions have a more than linear impact on
concentrations.
CH4 concentrations increase by about a
factor of 2 in the SCW and a factor of nearly
2.8 in the RCW, relative to 1985 levels, with
the most rapid growth occurring between 1985
and 2050 (see Figure 6-16). In the RCWA
case, concentrations increase nearly fourfold
between 1985 and 2100. Interestingly, the
2050 concentration obtained in the SCW is
similar to the result of linearly extrapolating
the currently observed growth rate of 1% per
year, whereas the RCW value is close to an
exponential extrapolation of current growth;
the 2100 values lie substantially below a
continuation of such extrapolations for
another 50 years. In the Stabilizing Policy
cases, CH4 concentrations increase by 10-20%
between 1985 and 2025, after which they level
off and decline to roughly 1985 levels by 2100.
In the RCWR case, concentrations decrease
below 1985 levels by 2100. CH4
concentrations are affected by temperature
feedbacks on atmospheric chemistry:
increasing the climate sensitivity of the model
from 2.0°C to 4.0°C reduces concentrations by
65 ppb in the RCWR (the smallest change)
and about 450 ppb in the RCWA (the greatest
change), assuming that emissions are not
affected (see end of chapter).
In contrast to methane, N2O
concentrations increase gradually in all The
scenarios (see Figure 6-16). The concentration
increase between 1985 and 2100 is about 115
parts per billion by volume (ppb) in the SCW,
130 ppb in the RCW, and 185 ppb in the
RCWA. This compares to 70 ppb in the
SCWP and about 65 ppb in the RCWP and
RCWR. Thus, the policy assumptions reduce
the concentration growth by 40-65%.
VI-47
-------
Policy Options for Stabilizing Global Climate
1800
500
450
FIGURE 6-16
ATMOSPHERIC CONCENTRATIONS
(3.0 Degree Celsius Climate Sensitivity)
CARBON DIOXIDE
METHANE
RCWA
RCWA
RCW
«ooo r
5000 -
Jj 4000 -
RCW
SCW 3000 -
RCWP
SCWP
RCWR 2000
NITROUS OXIDE
1000
10000
CHLOROFLUOROCARBONS
RCWA
, RCWA
SCWP § 5000
1986 2000 2029 20SO 2076 2100
1*862000 2028 2060 2076 2100
RCW
SCW
RCWP
RCWR
SCWP
VI-48
-------
Chapter VI: Thinking About the Future
CFC concentrations increase dramati-
cally in the No Response and Accelerated
Emissions scenarios despite the assumption
that at least 65% of developing countries and
95% of industrialized countries participate in
the Montreal Protocol (see Figure 6-16). The
total concentration of CFCs, weighted by their
relative contribution to the greenhouse effect,
increases by a factor of 4.8, 7.5, and 14.6 in the
SCW, RCW. and RCWA scenarios,
respectively. On the other hand, the phaseout
assumed in the Stabilizing Policy cases
stabilizes CFC concentrations (other than
HCFC-22) by 2025, but their total radiative
forcing still increases to 1.7-3.1 times the
current levels.
It is worthwhile to compare the
concentration changes calculated here, on the
basis of explicit assumptions linking emissions
with activities, to recent studies that have
made less formal estimates based primarily on
current trends in concentrations and/or
emissions (see Table 6-9). Our No Response
estimates of future concentrations are in close
agreement with those of Ramanathan et al.
(1985) for 2030 and Dickinson and Cicerone
(1986) for 2050. A notable exception is the
estimation of future concentrations of CFCs;
we expect significantly lower concentrations as
a result of the recent Montreal Protocol to
control production of these compounds. In
addition, our 2030 estimates of N2O
concentrations are at the lower end of the
range given by Ramanathan et al. (1985),
although they are closer to the center of
Dickinson and Cicerone's (1986) range for
2050.
The differences between the SCW and
RCW scenarios are significantly less than the
ranges suggested by these authors for all the
compounds listed in Table 6-9 - at least in
part because the only differences between the
SCW and RCW scenarios are assumptions
about activity levels and technology. In
contrast, the estimated concentration ranges
from the literature also consider uncertainties
in current sources, atmospheric chemistry, and
ocean carbon uptake (uncertainties in these
factors are considered later in this chapter and
in Appendix C). Also, the Slowly Changing
World and Rapidly Changing World scenarios
are not intended to completely bound future
possibilities; significant reductions in emissions
per unit of GNP are built into the No
Response scenarios. If this fails to materialize,
and/or if economic growth is more rapid than
assumed here, concentrations of several
greenhouse gases could be dramatically higher
than is estimated in these scenarios. For
example, in the RCWA scenario CO2
concentrations are about 750 ppm in 2050.
CH4 concentrations about 4.5 ppm, and N-.O
concentrations about 390 ppb.
Global Temperature Increases
Evaluating the consequences of
alternative climate change scenarios is beyond
the scope of this report (a variety of potential
domestic effects are examined in the
companion report, The Potential Effects of
Global Climate Change on the United States,
Smith and Tirpak, 1989), but an indicator of
the relative magnitude of change is needed as
a basis for comparing the scenarios considered
here. Analysts of trace gas emissions have
often emphasized the year by which carbon
dioxide concentrations (or the equivalent
combination of trace gases) can be expected to
reach twice their pre-industrial level (referred
to as 2xCO2), which is about 285 ppm. In the
absence of policies to reduce emissions,
however, climate change is potentially
unbounded. Atmospheric composition and
climate would continue to change after the
2xCO2 level was reached, and the ecological
and social consequences may depend as much
on what happens after CO2 doubles (if it does)
as on when this benchmark occurs. More
relevant to ecological and social systems are
the average and maximum rate of climate
change. Therefore, we focus on the average
rate at which global temperature may increase
during the next century as well as the
maximum rate of change. We emphasize that
these parameters are only indicators of global
change; changes at the regional level will vary
in both magnitude and timing, and changes in
precipitation may be as important as changes
in temperature. Nonetheless, the global
quantities calculated here can be used to
compare the scenarios presented here among
themselves and with results of more detailed
climate models.
VI-49
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Policy Options for Stabilizing Global Climate
TABLE 6-9
Comparison of Estimates of Trace-Gas Concentrations in 2030 and 2050
Concenirations in 2030
Trace Gas
CO, (ppm)
CH4 (ppm)
Tropospheric-O; (%)
N:O (ppb)
CFC-11 (ppb)
CFC-12 (ppb)
HCFC-22 (ppb)
Ramanathan
ct al. (1985)
450
2.3(1.8-3.3)
12.5
375(350-450)
1.1(0.5-2.0)
1.8(0.9-3.5)
0.9(0.4-1.9)
A
443
3.5
+
381
2.3
3.9
GISS
B
427
2.5
0
352
0.8
1.4
C
368
1.9
0
314
0.2
0.5
sew
440
2.6
20
350
0.5
1.0
0.4
RCW
460
2.6
20
350
0.6
1.1
0.7
Concentrations
Trace Gas
CO: (ppm)
CH, (ppm)
Tropospheric-O, (%)
N2O (ppb)
CFC-11 (ppb)
CFC-12 (ppb)
HCFC-22 (ppb)
Dickinson &
Cicerone (1986)
400-600
2.1-4.0
15-50
350-450
0.7-3.0
2.0-4.8
A
513
4.7
*
480
4.2
7.3
GISS
B
465
2.7
0
376
1.0
1.8
C
368
1.9
0
314
0.2
0.4
sew
495
2.9
24
375
0.6
1.3
0.7
RCW
560
3.2
26
370
0.6
1.4
1.8
RCWA
530
3.3
38
360
0.8
1.6
0.7
in 2050
RCWA
750
4.5
60
390
1.2
2.4
1.9
SCWP
400
1.9
-0.3
335
0.4
0.7
0.4
SCWP
410
1.8
-2.3
345
0.3
0.7
0.6
RCWP
400
1.9
1
335
0.4
O.S
0.7
RCWP
425
1.9
-1.1
345
0.3
0.8
1.7
RCWR
380
1.7
-2.4
330
0.4
0.8
0.7
RCWR
370
1.6
-7
345
0.3
0.8
1.6
* In this scenario the effect of O, and other trace-gas changes is approximated by doubling the radiative forcing contributed
by CFC-11 and CFC-12.
VI-50
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Chapter VI: Thinking About the Future
The changes in concentrations shown in
Figure 6-16 produce the estimated global
temperature changes shown in Figure 6-17 and
Table 6-10 for a range of climate sensitivity
(2.0-4.0°C equilibrium increase in global
temperature from doubling the atmospheric
concentration of CO2; see CHAPTER III).
Both the "equilibrium warming commitment"
and the "realized warming" are presented as a
function of time. The equilibrium warming
commitment for any given year is the
temperature increase that would occur in
equilibrium if the atmospheric composition
was fixed in that year. Because the oceans
have a large heat capacity, the temperature
change realized in the atmosphere lags
considerably behind the equilibrium level.
Realized warming has been estimated with a
simple model of ocean heat uptake as
discussed in Chapter III.
Because the response of the climate
system to changes in greenhouse gas
concentrations is quite uncertain, we also
consider a range of "climate sensitivities."
Climate sensitivity is defined as the
equilibrium warming commitment due to
doubling the concentration of carbon dioxide
from pre-industrial levels. Given a particular
emissions scenario and climate sensitivity, the
realized warming is much more uncertain than
the equilibrium warming commitment because
the effective heat storage capacity of the ocean
is not known. On the other hand, because the
amount of unrealized warming increases with
increasing climate sensitivity, for a given
scenario, realized warming depends less on
climate sensitivity than does warming
commitment.
The SCW, RCW, and RCWA scenarios
lead to substantial global warming. In the
SCW, estimated realized warming increases
1.0-1.6°C between 2000 and 2050, and 1.9-
3.2°C between 2000 and 2100 (see Table 6-10).
The maximum decadal (per decade) rate of
change associated with this scenario is 0.2-
0.3°C sometime in the middle of the next
century. The total equilibrium warming
commitment is substantially higher, reaching
3.3-6.6°C by 2100 relative to pre-industrial
levels. The equilibrium warming commitment
equivalent to doubling the concentration of
CO2 from pre-industrial levels is reached by
about 2040 in the SCW scenario.
The rate of change during the next
century would be more than 50% greater in
the RCW scenario, which shows a global
temperature increase from 2000 of 1.3-2.0°C by
2050 and 3.1-5.0°C by 2100 (see Table 6-10).
In this case the maximum rate of change is
0.4-0.6°C per decade, which occurs sometime
between 2070 and 2100. The equilibrium
warming commitment is 5-10°C by 2100 in this
scenario, and the 2xCO2 equivalent level is
reached by about 2030.11
The rate of change is substantially
higher in the RCWA case compared to the
SCW and RCW scenarios. The global
temperature increase from 2000 to 2050 is 2.1-
3.1°C; by 2100, it is 5.4-8.3°C. The maximum
rate of change is about 0.7-1.0°C per decade,
which occurs toward the end of the next
century. The equilibrium warming
commitment in this scenario is 8.2-16.38C by
2100, and the 2xCO2 equivalent level is
reached by about 2015.
By contrast, the rate of climate change
in the Stabilizing Policy scenarios would be
less than 1.6°C per century. Global
temperatures in the SCWP case increase by
0.4-0.7°C from 2000 to 2050, and 0.5-1.1°C
from 2000 to 2100. Corresponding values are
0.5-0.9°C and 0.8-1.5°C in the RCWP case, and
0.2-0.5°C and 0.1-0.4°C in the RCWR case.
The maximum rate of change in these
scenarios is less than 0.2°C per decade and
occurs before 2010, largely as a result of
warming to which the world may already be
committed. In these three cases the additional
commitment to wanning is greater between
2000 and 2050 than it is between 2050 and
2100: 0.1-1.1°C versus (-0.5)-0.5°C. The
lowest values occur in the RCWR, where
aggressive policies reduce the equilibrium
warming commitment throughout most of the
next century. Total equilibrium warming
commitment reaches 1.4-2.8°C in the SCWP,
1.9-3.6°C in the RCWP, and 0.8-1.6°C in the
RCWR. While not without some risk, the rate
of change represented by the Stabilizing Policy
scenarios would give societies and ecosystems
much more time to adapt to climate change
than would be the case in the No Response
scenarios.
Carbon dioxide accounts for at least
60% of increased commitments to global
VI-51
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Policy Options for Stabilizing Global Climate
-
12 f-
4
4
FIGURE 6-17
REALIZED AND EQUILIBRIUM WARMING
(2.0 - 4.0 Degree Climate Sensitivity)
sew
RCW
SCWP
RCWP
RCWR
IMS 2000
20Z< 20(0
VI-52
-------
Chapter VI: Thinking About the Future
TABLE 6-10
Scenario Results For Realized And Equilibrium Warming
Realized Warming - 2°C Sensitivity
sew
RCW
RCWA
SCWP
RCWP
RCWR
Realized Wanning - 4°C Sensitivity
sew
RCW
RCWA
SCWP
RCWP
RCWR
Equilibrium Warming Commitment - 2°C Sensitivity
sew
RCW
RCWA
SCWP
RCWP
RCWR
Equilibrium Warming Commitment - 4°C Sensitivity
sew
RCW
RCWA
SCWP
RCWP
RCWR
1985
0.5
0.5
0.5
0.5
0.5
0.5
1985
0.7
0.7
0.7
0.7
0.7
0.7
1985
0.7
0.7
0.7
0.7
0.7
0.7
1985
1.5
1.5
1.5
1.5
1.5
1.5
2000
0.7
0.7
0.7
0.7
0.7
0.7
2000
1.0
1.0
1.1
1.0
1.0
1.0
2000
1.1
1.1
1.1
1.0
1.0
1.0
2000
2.2
2,2
2.3
2,0
2.0
2.0
2025
1.2
1.3
1.5
0.9
1.0
0.9
2025
1.8
1.9
2.1
1.4
1.5
1.4
2025
1.7
1.9
2.4
1.2
1.3
1.2
2025
3.5
3.8
4.7
2.5
2.6
2.3
2050
1.7
2.0
2.8
1.1
1.2
0.9
2050
2.6
3.0
4.2
1.7
1.9
1.5
2050
2.3
2.9
4.4
1.4
1.5
1.1
2050
4.7
5.8
>6.0*
2.7
3.1
2.1
2075
2.2
2.9
4.5
1.2
1.4
0.9
2075
3.4
4.4
>6.0*
1.9
2.2
1.5
2075
2.8
4.0
>6.0*
1.4
1.7
1.0
2075
5.7
>6.0*
>6.0*
2.8
3.4
1.9
2100
2.6
3.8
>6.0*
1.2
1.5
0.8
2100
4.2
6.0
>6.0*
2.1
2.5
1.4
2100
3.3
5.1
>6.0*
1.4
1.9
0.8
2100
>6.0*
>6.0*
>6.0*
2.8
3.6
1.6
* Estimates of equilibrium warming commitments greater than 6°C represent extrapolations beyond the range tested
in most climate models, and this warming may not be fully realized because the strength of some positive feedback
mechanisms may decline as the Earth warms. These estimates are represented by >6*C
VI-53
-------
Policy Options for Stabilizing Global Climate
warming between 2000 and 2100 in all of the
scenarios analyzed in this report (see Figure
6-18). This represents a significantly higher
estimate of the role of CO2 compared with
estimates for the last few decades (roughly
50%) and in Ramanathan et al.'s (1985)
scenario for 2030. Much of this difference is
because of smaller increases in CFCs in our
scenarios due to our assumption that the
Montreal Protocol comes into force. In
addition, growth in emissions of CH4 and N2O
is projected to be slower than that of CO2,
particularly after 2030. The role of CO2 is
greatest in the Stabilizing Policy scenarios
because our assumptions lead to relatively
stable concentrations of CH4 and tropospheric
ozone, while CO2 concentrations continue to
increase gradually.
Comparison with General Circulation Model
Results
Hansen et al. (1988) analyzed three
transient trace gas scenarios using the GISS
GCM (see Table 6-9). The GISS A scenario,
based on exponential extrapolation of current
greenhouse gas trends, most closely resembles
our RCW with 4.0°C climate sensitivity (the
climate sensitivity of the GISS GCM is 4.2°C).
Indeed, both the equilibrium and realized
global warming in these cases are within 0.1°C
in 2025.12 By 2050, the continuation of
exponential growth in trace gas concentrations
in the GISS A scenario leads to an equilibrium
warming commitment that is about 30%
higher than in the RCW, with a corresponding
realized warming of 3.4° versus 3.0°C (all
references to realized warming in the GISS
scenarios are based on five-year running
means; see Figure 3b in Hansen et al., 1988).
By 2060, the end of the GISS simulation, the
realized warming in the GISS A scenario is
4.2°C compared with 3.6°C in the RCW. The
GISS B scenario, which is based on linearly
increasing trace gas concentrations at current
rates, is most similar to the RCWP case (with
4.0°C climate sensitivity). These two cases
have very similar equilibrium warming
commitments and realized warmings in 2030
(the end of the GISS simulation for this
scenario). The final scenario examined by
GISS, case C, assumes that atmospheric
composition is stable after 2000, which leads
to realized warming of about 0.9°C by 2040.
The Stabilizing Policy cases examined here do
not achieve this result; realized warming
reaches 1.4-1.5°C by 2025 if the climate
sensitivity is 4.0°C. Thus, the GISS scenarios
bracket the range of the scenarios developed
here and may provide some indication of the
regional differences in the rates and
magnitudes of temperature change that might
be associated with our cases (possible regional
variations are discussed in Hansen et al.,
1988).
Relative Effectiveness of Selected Strategies
The major assumptions that distinguish
the RCW and RCWP scenarios from each
other have been grouped into eleven
categories in order that we may examine the
relative importance of different policy
strategies. Similarly, the rapid emissions
reduction policies and the accelerated
emissions policies have been grouped into six
and eight such categories, respectively. Each
set of options was applied individually to the
RCW case; the combination of all the
strategies represents the RCWP, RCWR, and
RCWA cases, respectively. Figures 6-19
through 6-21 present the results in terms of
the effect of each policy strategy in reducing or
increasing the equilibrium warming
commitment in 2050 and 2100. This analysis
suggests that accelerated energy-efficiency
improvements, reforestation, modernization of
biomass use, carbon emissions fees, and a CFC
phaseout could have the largest near-term
impact on the rate of climate change. In the
long run, advances in solar technology and
biomass plantations also play an essential role.
Comparing the results in Figures 6-20
and 6-21 suggests, however, that the effects of
policy choices that increase the rate of growth
in greenhouse gas emissions could be much
larger than the effects of policies that
accelerate reductions in future emissions rates.
In other words, it may be easier for
government policy to worsen the problem than
to ameliorate it. If the policies evaluated here
are representative of the range of relevant
choices, policies that increase emissions may
make the situation much worse than current
trends suggest, and they may produce large
effects very quickly.
VI-54
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Chapter VI: Thinking About the Future
FIGURE 6-18
RELATIVE CONTRIBUTION TO WARMING
1985 TO 2100
sew
SCWP
64%
70%
4%
13%
13%
6%
12%
7%
11%
RCW
RCWP
• 6%
66%
4%
14%
12%
15%
11%
6%
RCWA
BCWR
61%
• 1%
20%
11%
Nltrout Oxld*
CFCi
Ozon*
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Policy Options for Stabilizing Global Climate
FIGURE 6-19
STABILIZING POLICY STRATEGIES:
DECREASE IN EQUILIBRIUM WARMING COMMITMENT
1. Improved Transportation
Efficiency*
2. Other Efficiency Gains"
3. Carbon Fee0
4. Cheaper Nuclear
Power"
5. Solar Technologies*
6. Commercialized Biomass'
7. Natural Gas Incentives9
8. Emission Controls
9. CFC Phaseout1
10. Reforestation
11. Agriculture, Landfills,
and Cementk
RCWP (Simultaneous i
Implementation of 1-11)
Percent Reduction Relative to RCW
2050
2100
64%
10 15
Percent
20
Figure 6-19. The impact of individual measures on the equilibrium warming commitment in the RCW
scenario. The simultaneous implementation of all the measures represents the RCWP scenario.
VI-56
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Chapter VI: Thinking About the Future
Figure 6-19 -- NOTES
Impact Of Stabilizing Policies On Global Warming
a The average efficiency of care and light trucks in the U.S. reaches 30 mpg (7.8 liters/100 km) by 2000, new cars achieve 40
mpg (5.9 liters/100 km). Global fleet-average automobile efficiency reaches 43 mpg by 2025 (5.5 liters/100 km). In the RCW
case global vehicle efficiencies for cars and light trucks achieve 30 mpg by 2025.
b The rates of energy efficiency improvements in the residential, commercial, and industrial sectors are increased about 0.3-0.8
percentage points annually from 1985 to 2025 compared to the RCW, and about 0.2-0.3 percentage points annually from 2025
to 2100.
c Carbon fees are placed on fossil fuels in proportion to their carbon content. Fees are placed only on production; maximum
production fees (1988$) are Sl.OO/gigajoule (GJ: 1 GJ = 10* joules) for coal (about 525/ton), S0.80/GJ for oil. and S0.54/GJ
for natural gas. These fees increase linearly from zero, with the maximum production t'ee charged by 2025. In the RCW case
no carbon fees were assumed.
d Assumes that technological improvements in the design of nuclear powerplams reduce costs by about 0.6 cems/kWh (1988S)
by 2050. In the RCW we assumed that nuclear costs in 1985 were 6.1 cents/kWh (1988S).
e Assumes that low-cost solar technology is available by 2025 at costs as low as 6.0 cents/kWh. In the RCW case these costs
approached 8.5 cents/kWh, but these levels were not achieved until after 2050.
f Assumes the cost of producing and convening biomass to modern fuels reaches S4.35/GJ (1988$) for gas and 56.00/GJ (1988$)
for liquids. The maximum amount of liquid or gaseous fuel available from biomass (i.e.. after conversion losses) is 205 EJ.
8 Assumes that economic incentives to use gas for electricity generation increases gas share by 5% in 2000 and 10% in 2025.
h Assumes more stringent NOX and CO controls on mobile and stationary sources, including all gasoline vehicles using three-way
catalysts, in OECD countries by 2000 and in the rest of the world by 2025 (new light-duty vehicles in the rest of the world use
oxidation catalysts from 2000 to 2025). In the RCW case only the U.S. adopts three-way catalysts (by 1985), the OECD
countries adopt oxidation catalysts by 2000, and the rest of the world does not add any controls. From 2000 to 2025
conventional coal boilers used for electricity generation are retrofit with low NO, burners with 85% retrofit in the developed
countries and 40% in developing countries; starting in 2000 all new combustors used for electricity generation and all new
industrial boilers require selective catalytic reduction in the developed countries and low NO, burners in the developing
countries, and after 2025 all new combustors of these types require selective catalytic reduction; other new industrial non-boiler
combustors such as kilns and dryers require low NO,, burners after 2000. In the RCW case no additional controls are assumed.
i A 100% phaseout of CFCs by 2003 and a freeze on methyl chloroform is imposed. There is 100% participation by
industrialized countries and 94% participation by developing countries. In the RCW scenario we assumed compliance with the
Montreal Protocol, which called for a 50% reduction in the use of the major CFCs. The London Amendments to the Protocol
were not included in this analysis because they were adopted in June 1990, after this analysis was completed. The 100%
phaseout assumed here is more stringent that the phaseout reflected in the London Amendments.
' The terrestrial biosphere becomes a net sink for carbon by 2000 through a rapid reduction in deforestation and a linear
increase in the area of reforested land and biomass plantations. Net CO, uptake by 2025 is 0.7 Pg C. In the RCW case, the
rate of deforestation continues to increase very gradually, reaching 15 Mhafyr in 2097 and no reforestation occurs.
k Assumes that research and improved agricultural practices result in an annual decline of 0.5% in the emissions from rice
production, enteric fermentation, and fertilizer use. CH4 emissions from landfills are assumed to decline at an annual rate of
2% in developed countries because of policies aimed at reducing solid waste and increasing landfill gas recovery, while emissions
in developing countries continue to grow until 2025 and then remain flat due to incorporation of the source policies.
Technological improvements reduce demand for cement by 25%.
1 Impact on global warming when all the above measures are implemented simultaneously. The sum of each individual reduction
in warming is not precisely equal to the difference between the RCW and RCWP cases because not all the strategies are strictly
additive.
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Policy Options for Stabilizing Global Climate
FIGURE 6-20
RAPID REDUCTION STRATEGIES:
ADDITIONAL DECREASE IN EQUILIBRIUM WARMING COMMITMENT
1. Carbon Fee
2. High MPG Cars
3. High Efficiency
Buildings6
4. High Efficiency
Powerplants"
5. High Blomass
6. Rapid Reforestation
Rapid Reduction '
(Implementation
of 1-6)
Additional Percent Relative to RCW
2050
2100
10 15
Percent
20
25
Figure 6-20. The impact of additional measures applied to the RCWP scenario expressed as percent
change relative to the equilibrium warming commitment in the RCW scenario. The simultaneous
implementation of all the measures in combination with the measures in the RCWP scenarios
represents the Rapid Reduction Scenario.
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Chapter VI: Thinking About the Future
FIGURE 6-20 -• NOTES
Impact Of Rapid Reduction Policies On Global Warming
a High carbon emissions fees are imposed on the production of fossil fuels in proportion to the CO, emissions potential. In
this case, fees of about S4.00/GJ were imposed on coal (SlOO/ton). S3.20/GJ on oil (Sl9/barrel), and"S2.15/GJ on natural gas
(52.00/mcf). These fee levels are specified in 1988S and are phased in over the period between 1985 and 2025. No fees were
assumed in the RCW case.
b Assumes that the average efficiency of new cars in the U.S. reaches 50 mpg (4.7 liters/100 km) in 2000 and that global fleet-
average auto efficiencies reach 65 mpg in 2025 (3.6 liters/100 km) and 100 mpg (2.4 liters/100 km) in 2050.
c Assumes that the rate of technical efficiency improvement in the residential and commercial sectors improves substantially
beyond that assumed in the RCWP case. In this case, the rate of efficiency improvement in the residential and commercial
sectors is increased so that a net gain in efficiency of 50% relative to the RCWP case is achieved in all regions.
d Assumes that, by 2050. average powerplant conversion efficiency improves by 50% relative to 1985. In this case the design
efficiencies of all types of generating plants improve significantly. For example, by 2025. new oil-fired generating stations achieve
an average conversion efficiency roughly equivalent to 5% greater than that achieved by combined-cycle units today.
e The availability of commercial biomass is doubled relative to the assumptions in the RCWP case. In this case the rate of
increase in biomass productivity is assumed to be at the high end of the range suggested by the U.S. DOE Biofuels Program.
Conversion costs were assumed to fall by one-third relative to the assumptions in the RCWP case.
' A rapid rate of global reforestation is assumed. In this case deforestation is halted by 2000 and the biota become a net sink
for CO, at a rate of about 1 Pg C per year by 2025, about twice the level of carbon storage assumed in the RCWP case.
s Impact on warming when all of the above measures are implemented simultaneously. The impact is much less than the sum
of the individual components because many of the measures are not additive.
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Policy Options for Stabilizing Global Climate
FIGURE 6-21
ACCELERATED EMISSIONS CASES:
INCREASE IN EQUILIBRIUM WARMING COMMITMENT
1. High CFC Emissions"
2. Cheap Coal
3. Cheap Synfuels
4. High Oil & Gas Prices
5. Slow Efficiency
Improvements*
6. High Deforestation'
7. High-Cost Solar
8. High-Cost Nuclear
Accelerated Emissions
(Combination of 1-8}'
Percent Relative to RCW
-5 0 10 20 30 40 50 60 70
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Chapter VI: Thinking Abou» the Future
FIGURE 6-21 -- NOTES
Impact Of Accelerated Emissions Policies On Global Warming
3 Assumes a low level of participation in and compliance with the Montreal Protocol. The assumptions used in this case are
similar to those used in the "Low Case" analysis described in the U.S. EPA's Regulatory Impact Analysis report (U.S. EPA,
1988), i.e., about 75% participation among developed countries and 40% among developing countries. This analysis does not
include the London Amendments to the Protocol, which were adopted in June 1990 after this analysis was completed.
b Assumes that advances in the technology of coal extraction and transport rapidly reduce the market price of coal at the burner
tip. In the RCW scenario, the economic efficiency of coal supply is assumed to improve at a rate of approximately 0.5% per
year. In this case, it is assumed to improve at a rate of 1% per year.
c Assumes that the non-fuel cost of converting coal to synthetic oil and gas is reduced by 50% relative to the RCW case.
* Assumes that OPEC (or some other political entity) can control production levels and thus raise the border price of oil and
gas. To simulate this effect, oil and gas resources were shifted to higher points on the regional supply curves. In addition.
extraction costs for oil in each resource grade were increased relative to the assumptions in the RCW case.
c Assumes that technical gains in the engineering efficiency of energy use occurs only half as rapidly as assumed in the RCW
case. In the RCW case it is assumed that energy intensity per dollar of GNP improves at rates of approximately 1-2% per year.
In the Slow Improvement case the assumed rates were reduced to only 0.5-1.0% per year. The lower rate of improvement is
similar to the assumptions in recent projections for the U.S. Department of Energy's National Energy Policy Plan.
f Assumes annual tropical deforestation increases at a rate equal to the rate of growth in population.
6 Assumes that solar energy remains so expensive that its price precludes the possibility of its making any significant contribution
to global energy supply.
h Assumes that the cost of electricity from fission electric systems becomes so high that their contribution to global energy
supply is permanently limited. In this case, an environmental tax of about 6 cents/kWh (1988S) on the price of electricity
supplied by nuclear powerplants was phased in by 2050.
1 All of the above assumptions were combined in one scenario. The result is not equal to the sum of the warming in the RCW
and the eight individual cases because of interactions among the assumptions.
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Policy Options for Stabilizing Global Climate
SENSITIVITY ANALYSES
The RCW and SCW scenarios presented
earlier in this chapter describe two
significantly different futures for the global
community. Although these two potential
paths capture a wide range of uncertainty, they
do not represent all possible outcomes.
Alternative assumptions are clearly possible
for many of the parameters specified in these
scenarios; these alternative specifications could
alter the timing and magnitude of global
climate change described in the RCW and
SCW scenarios. To understand the
importance of these alternative assumptions,
this section examines how changes in key
parameters affect our portrayal of the rate and
magnitude of global climate change. These
sensitivity analyses include alternative
assumptions about the magnitude and timing
of global policies to combat climate change,
rates of technological change, the carbon cycle,
sensitivity of the climate system, and
feedbacks.
The sensitivity analyses discussed in this
section are generally run relative to the RCW
scenario, unless specified otherwise. Only a
few of the major sensitivity analyses are
discussed here for the reader; more detailed
discussion of all of the sensitivity analyses that
were evaluated are provided in Appendix C.
Assumptions About the Magnitude and Timing
of Global Climate Stabilization Strategies
The analyses of the Stabilizing Policy
scenarios presented in this Report are based
on the assumption that the global community
takes immediate, concerted action to contend
with the consequences of climate change.
Potential actions, which are discussed in
Chapters V, VII, and VIII, include reducing
the amount of energy required to meet the
world's increasing needs, developing
alternative technologies that do not require
the consumption of fossil fuels, halting
deforestation, and making changes in
agricultural practices, among others. For
many reasons, however, the world may not
respond to the threat of climate change in a
timely fashion. This section explores the
consequences of other possibilities, particularly
the unwillingness or inability of some
countries to participate in climate stabilization
programs and the implications of delaying
global action until a later date.
No Participation by the Developing Countries
Most of the greenhouse gas emissions
currently committing the world to climate
change can be traced to activities by the indus-
trialized countries. Although the quantity of
emissions generated by developing countries
has been increasing, some argue that since the
greenhouse problem has been largely caused
by the industrialized countries, those countries
should be responsible for solving the problem.
Also, despite the potential environmental
consequences of global climate change, other
problems facing the developing countries, such
as poverty, inadequate health care, and more
immediate environmental problems may make
it difficult for developing countries to commit
any resources to climate stabilization policies.
Regardless of the merits of these
arguments, for this sensitivity analysis we have
assumed that developing countries do not
participate in any climate stabilization
activities; that is, only developed, industrialized
countries adopt policies to limit global climate
change. For this analysis the developing
countries include China and other centrally-
planned Asian economies, the Middle East,
Africa, Latin America, and South and
Southeast Asia. We have assumed that
industrialized countries (i.e., the U.S., the rest
of the OECD countries, and the USSR and
Eastern Europe) follow the path assumed in
the RCWP scenario, while developing
countries follow the path assumed in the RCW
case, in which the entire global community
does not respond to climate change.
Even if developing countries do not
participate in global stabilization policies,
policies adopted by the industrialized countries
are likely to lead to technological
advancements, altered market conditions, etc.,
that indirectly reduce emissions in the
developing countries as well. For example,
advancements by the developed countries in
automobile fuel efficiency or fuel supply
technologies may be partly adopted by the
developing countries, tangentially allowing for
some climate stabilization benefits. If the
developing countries do not participate,
however, they may tend to adopt technological
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Chapter VI: Thinking About the Future
advances more slowly and at a higher cost than
if they had participated from the start. This
slower rate of technological diffusion could
occur for many reasons -- for example, if the
industrialized countries take actions that
prevent easy access to improved technologies
or they are unwilling or unable to make the
necessary capital available for investment, or if
developing countries decide to invest their
limited resources in other areas.
Since we cannot be certain of the
direction that non-participation by the
developing countries might take, we analyzed
two cases to capture the potential range of
likely possibilities. In the first case, little
technological diffusion was assumed, resulting
in a future path of energy consumption and
investment trends for developing countries
similar to those assumed in the RCW scenario.
In the second case, developing countries were
assumed to have greater access to the
efficiency improvements and technological
advances assumed for the RCWP case as a
result of policies by the industrialized
countries to make these improvements
available and to extend the credit necessary for
investment by the developing countries in
these improvements.
In this analysis key assumptions for the
developing countries included the following:
(1) rates of energy-efficiency improvements for
all sectors are the same as in the RCW case or
midway between the RCW and RCWP case;
for example, automobile efficiency levels,
which by 2050 in developing countries were 5.9
liters/100 km (40 mpg) in the RCW case, and
3.1 liters/100 km (75 mpg) in the RCWP case,
were varied from 5.9-4.1 liters/100 km (40-58
mpg); (2) CFCs are not phased out (although
compliance with the Montreal Protocol would
still occur); (3) agricultural practices that
cause methane emissions from rice and enteric
fermentation and nitrous oxide emissions from
fertilizers do not change or show modest
improvements; (4) deforestation continues as
in the RCW case with an exponential decline
in forest area; (5) non-fossil energy supply
technologies developed by the industrialized
countries are available to developing countries
at a later date and higher cost than assumed in
the RCWP case; for example, technological
diffusion of biomass gasification technology
would occur ten years later than it would in
the RCWP case, but feedstock costs would
remain high due to a lack of investment by the
developing countries in highly productive
energy plantations; and (6) no additional
incentives are provided for increased use of
natural gas.
Without the participation of the
developing countries to stabilize the
atmosphere, the amount of greenhouse gas
emissions will increase substantially. In the
two analyses considered here, CO2 emissions
are 3.9-5.3 Pg C higher than in the RCWP
case by 2050 and 4.6-8.5 Pg C higher by 2100
(emissions by 2100 are 12.3 to 16.2 Pg C lower
than in the RCW case since industrialized
countries adopt climate stabilization policies),
and other greenhouse gas emissions are also
higher (based on 3°C climate sensitivity).
These emission increases are sufficient to
increase realized warming by 0.4-0.6°C in 2050
compared with the RCWP case and 1.2-1.6°C
by 2100 (see Figure 6-22), with equilibrium
warming by 2100 up to 1.9-2.6°C higher (based
on 3°C climate sensitivity). Figure 6-22 also
shows the results for the SCW scenarios.
These emission increases are sufficient to
increase realized warming by 0.4-0.5°C in 2050
compared with the SCWP case and 0.8-1.0°C
by 2100, with equilibrium warming by 2100 up
to 1.2-1.6°C higher.
The implications of these results are
clear: even if the industrialized countries
adopt very stringent policies to counteract the
effects of climate change, the atmosphere will
continue to warm at a rapid rate. Unilateral
action by the industrialized countries can
significantly slow the rate and magnitude of
climate change, but because of the growing
impact that developing countries have on the
global climate, without the participation of the
developing countries, substantial global
warming is unavoidable. Because most of the
world's population resides in these countries,
their role in climate stabilization becomes
increasingly important as the demand for
resources to feed and clothe their growing
populations and to improve their standard of
living expands.
Delay in Adoption of Policies
For the Stabilizing Policy cases it is
assumed that the global community takes
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Policy Options for Stabilizing Global Climate
FIGURE 6-22
INCREASE IN REALIZED WARMING
WHEN DEVELOPING COUNTRIES DO NOT PARTICIPATE
(Based on 3.0 Degree Sensitivity)
Slowly Changing World
Rapidly Changing World
£ 3
U
•
•
o „
sew
SCWP with
No Participation
by Developing
Countrle*
SCWP
RCW
4 -
3 -
RCWP with
No Participation
by Developing
Countries
2 -
1986 2000 2026 2060 2076 2100 1986 2000 2028 2060 2076 2100
Y««r Year
VI-64
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Chapter VI: Thinking About the Future
immediate action to respond to the dangers
posed by climate change. For this sensitivity
analysis we have assumed that the global
community delays any response to the threat
of climate change, with developed countries
(i.e., the United States, the rest of the OECD
countries, the USSR and centrally-planned
European economies) delaying action until
2010, and the developing countries delaying
action until 2025. Additionally, once regions
do initiate action to combat global warming,
they do so at a slower rate than that assumed
in the RCWP case. This slower approach
assumes a minimum 25-year delay in attaining
the policy goals of the RCWP case; that is,
levels of technological improvement,
availability of alternative energy supply
technologies, etc., will be achieved at least 25
years later. For example, in the RCWP case,
automobile efficiency reaches 3.1 liters/100 km
(75 mpg) by 2050, whereas in the Delay case
industrialized countries reach 3.9 liters/100 km
(60 mpg) by 2050, while developing countries
reach 4.7 liters/100 km (50 mpg). The rate of
energy efficiency improvement for the
residential, commercial, and industrial sectors
is unchanged from the rates assumed in the
RCW case, through 2010 for industrialized
countries and through 2025 for developing
countries. After these years, energy efficiency
improvements occur at the same rate as was
assumed in the RCWP case, and the
implementation of production and
consumption taxes on fossil fuels from the
RCWP case is delayed until 2010 for
developed countries and until 2025 for
developing countries.
Delaying the adoption of policies to
stabilize the atmosphere significantly increases
the Earth's commitment to global warming.
With delay by the industrialized countries until
2010 and by the developing countries until
2025, the increase in realized wanning
compared to that assumed in the RCWP case
is 0.5-0.7°C by 2050 and 0.6-0.9°C by 2100,
and equilibrium warming is 0.7-1.4°C higher by
2050 and 0.7-1.4°C higher by 2100, respectively
(based on climate sensitivities of 2.0-4.0°C; see
Figure 6-23). Figure 6-23 also shows the
results for the Slowly Changing World
scenarios. If global delays do occur, the
increase in realized warming compared to that
assumed in the SCWP case is 0.4-0.6°C by
2050 and 0.4-0.6°C by 2100, and equilibrium
warming is 0.5-1.10C higher by 2050 and 0.4-
0.8°C higher by 2100, respectively (based on
climate sensitivities of 2.0-4.0°C).
Assumptions Affecting Rates of Technological
Change
The extent of global warming will
depend on the availability of energy supplies
and technologies that minimize dependence on
carbon-based fuels, nitrogen-based fertilizers,
and other sources of greenhouse gas emissions.
The availability of non-fossil-fuel technologies
could have an impact on the rate of change in
greenhouse gas emissions. Alternative
assumptions regarding this issue are presented
below.
Availability of Non-Fossil Technologies
Most technologies in use currently rely
on fossil fuels to supply their energy needs. In
the Rapidly Changing World, fossil-fuel-based
technologies continue to dominate throughout
the next century: by 2100 fossil fuels still
supply over 70% of primary energy needs.
However, if non-fossil technologies can be
commercialized earlier, the magnitude of
global climate change can be reduced because
these technologies do not emit the greenhouse
gases that cause global warming. To evaluate
the implications of the availability of non-fossil
technologies, two different scenarios were
analyzed: (1) an Early Non-Fossil case, in
which non-fossil technologies, specifically solar
photovoltaics, advanced nuclear power designs,
and production of synthetic fuels from
biomass, are commercially available by 2000 at
a rate faster than that assumed in the RCWP
case; and (2) an Intermediate Non-Fossil case,
in which non-fossil technologies are widely
available by the middle of the next century
(i.e., greater use of non-fossil technologies
than in the RCW case, but less than in the
RCWP case). The intent of these two cases is
to capture a range of possible roles for non-
fossil technologies, with the first case reflecting
very optimistic assumptions on non-fossil
availability and the second case reflecting more
modest assumptions.
In the Early Non-Fossil case, non-fossil
energy sources increase their share of total
primary energy supply from 12% in 1985 to
about 40% by 2025 and 55% by 2100, while in
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Policy Options for Stabilizing Global Climate
FIGURE 6-23
INCREASE IN REALIZED WARMING
DUE TO GLOBAL DELAY IN POLICY OPTIONS
(Based on 3.0 Degree Sensitivity)
Slowly Changing World
Rapidly Changing World
sew
SCWP with
Global Dolay
SCWP
RCW
RCWP with
Global Delay
HCWP
1886 2000 2026 2060 2076 2100 1«86 2000 2026 2060 2078 2100
Y«ar Yoar
VI-66
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Chapter VI: Thinking About the Future
the Intermediate Non-Fossil case the share for
non-fossil technologies increases to 20% by
2025 and about 50% by 2100 (see Figure
6-24a). In the near term, the non-fossil share
of total energy could be greater than that
reflected in the RCWP case if commercial
availability is achieved at an earlier date. In
this sensitivity analysis, however, the non-fossil
share is lower in the long run compared with
the share in the RCWP case because other
policies that were included in the RCWP case
to discourage the use of fossil fuels were not
included in this case. In both cases, however,
an increased role for non-fossil technologies
can affect the amount of global warming. As
shown in Figure 6-24b, for the Early Non-
Fossil case the amount of realized warming
compared with the RCW case is reduced about
0.1-0.2°C by 2050 and 0.6-0.9°C by 2100;
equilibrium warming is reduced about 0.3-
0.6°C by 2050 and 0.9-1.7°C by 2100 (based on
2.0-4.0°C climate sensitivities). For the
Intermediate Non-Fossil case, the amount of
realized warming compared with the RCW
case is reduced about O.TC by 2050 and 0.4-
0.6°C by 2100; equilibrium warming is reduced
about 0.2-0.3°C by 2050 and 0.6-1.2°C by 2100.
Assumptions About Climate Sensitivity and
Timing
Sensitivity of the Climate System
A general benchmark for comparing
atmospheric models is their response to a
doubling of CO2 concentrations (see
CHAPTER III). Simply put, this benchmark
describes how much warming would be
expected once the atmosphere stabilizes
following a twofold increase in CO2
concentrations (relative to pre-industrial
levels). In our analyses we have used the
range of 2.0-4.0°C. As discussed in Chapter
III, there is a great deal of uncertainty about
the strength of internal climate feedbacks and,
in some cases, whether a feedback will be
positive or negative. If cloud and surface
albedo changes produce large positive
feedbacks, as suggested by some analyses, the
climate sensitivity could be 5.5°C or greater.
On the other hand, these feedbacks could be
weak, and cloud feedbacks could be negative,
resulting in a climate sensitivity as low as
1.5°C. For this sensitivity analysis, therefore,
we have evaluated the extent of global
warming using 1.5 and 5.5°C as lower and
upper bounds, respectively. The impact of
these assumptions on realized warming is
illustrated in Figure 6-25 for the RCW and
SCW cases. In the RCW case the range of
realized warming for a 1.5-5.5°C climate
sensitivity would be 1.6-3.5°C by 2050 and 3.0-
7.0°C by 2100, compared to a range of 2.0-
3.0°C by 2050 and 3.8-6.0°C by 2100, when the
climate sensitivity is bounded by 2.0-4.0°C.
The corresponding values for equilibrium
warming for a 1.5-5.5°C climate sensitivity are
2.2-7.9°C by 2050 and 3.8-13.9°C by 2100,
compared to 2.9-5.8°C by 2050 and 5.1-10.1°C
by 2100 for a 2.0-4.0°C climate sensitivity. In
the SCW case the range of realized warming
for a 1.5-5.5°C climate sensitivity would be 1.4-
3.0°C by 2050 and 2.0-5.0°C by 2100, compared
to a range of 1.7-2.6°C by 2050 and 2.6-4.2°C
by 2100, when the range of climate sensitivity
is 2.0-4.0°C. The corresponding values for
equilibrium warming for a 1.5-5.5°C climate
sensitivity are 1.8-6.5°C by 2050 and 2.5-9.0°C
by 2100, compared to 2.3-4.7°C by 2050 and
3.3-6.6°C by 2100 for a 2.0-4.0°C climate
sensitivity.
Rate of Heat Diffusion
CO2 and heat are currently transferred
from the atmosphere to the oceans and within
the ocean itself as a result of many complex
chemical and physical interactions. One of
these interactions is the transfer of heat from
the mixed layer to the thermocline, thereby
delaying global warming. In addition, changes
in ocean mixing and circulation patterns as a
result of climate change, could alter the
capacity of the oceans to absorb heat (see
Biogeochemical Feedbacks for further
discussion). The rate at which heat is
absorbed affects only the rate of realized
warming, not the rate of equilibrium warming,
because the oceans cannot absorb heat
indefinitely.
In our model the rate at which mixing
occurs between the mixed layer and the
thermocline is parameterized with an eddy-
diffusion coefficient (see CHAPTER III). The
value of the eddy-diffusion coefficient in the
base cases was assumed to be 0.55 x 10"4
square meters per second (m2/sec). For
VI-67
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Policy Options for Stabilizing Global Climate
FIGURE 6-24
AVAILABILITY OF NON-FOSSIL ENERGY OPTIONS
(a) Non-Fossil Share Of Total Primary Energy Supply
100
80 —
80 —
40 —
20 -
(b)
m
• 2
RCWP
Non-Foul!
Energy Option*
RCW
Increase In Realized Warming
(Bated en 3.0 Degree Sensitivity)
RCW
Non-Fo>«ll
Energy Optlen*
,-; RCWP
1880 2000
2026
2000
2070
2100
Year
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Chapter VI: Thinking About the Future
FIGURE 6-25
7 -
IMPACT OF CLIMATE SENSITIVITY ON
REALIZED WARMING
(Based on 1.5 - 5.5 Degree Sensitivity)
Slowly Changing World
Rapidly Changing World
7 -
6.6
4.0
6 -
3 -
2 -
18S6 2000 2026 2060 2078 2100 1986 2000 2026 2060 2076 2100
Y««r Y»«r
VI-69
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Policy Options for Stabilizing Global Climate
purposes of this sensitivity analysis, alternative
values of 2 x 10'5 and 2 x 10'4 m2/sec have
been evaluated.
As shown in Figure 6-26, the rate at
which the oceans absorb heat can noticeably
affect the amount of realized warming by 2100.
If the rate of heat absorption is greater than
that assumed in the base cases (i.e., if the
eddy-diffusion coefficient is 2 x W4 m2/sec),
realized warming by 2100 would be 0.5-1.2°C
less than in the RCW case (assuming 2.0-4.0°C
climate sensitivities). For the smaller eddy-
diffusion coefficient of 2 x 10"5 m2/sec, realized
warming by 2100 would be 0.3-0.9°C higher.
Biogeochemical Feedbacks
The sensitivity of the climate system to
anthropogenic perturbations is determined by
a combination of feedbacks that amplify or
dampen the direct radiative effects of
increasing concentrations of greenhouse gases.
Several important internal climate feedbacks,
such as those resulting from changes in water
vapor, clouds, and sea ice albedo, are included
in the estimates of climate sensitivity discussed
throughout this report. There are a number of
feedbacks of a biogeochemical origin, however,
that may also play an important role in climate
change that were not included in the analyses
on which this range is based. Biogeochemical
feedbacks include releases of methane from
hydrates; changes in ocean chemistry, biology,
and circulation; and changes in the albedo of
the global vegetation.
Any attempt to quantify the impact of
biogeochemical feedbacks is necessarily quite
speculative at this time. However, it does
appear that feedbacks could have an important
impact on global climate. For example,
Lashof (1989) has estimated that the gain from
biogeochemical feedbacks ranges from 0.05-
0.29 compared with a 0.17-0.77 gain from
internal climate feedbacks. (The gain is
defined as the portion of global equilibrium
temperature change attributable to the
feedback divided by the total global
equilibrium temperature when the feedback is
included). Some of these key feedbacks were
incorporated into the atmospheric composition
model for these sensitivity cases to determine
the magnitude of their impact on global
warming.
Ocean Circulation
As mentioned above, the oceans are
currently a major sink for heat and CO2.
Concerns have been raised, however, that the
basic circulation patterns that allow these
processes to continue could be significantly
altered as the global climate changes. This
possibility is suggested by the rapid rate of
atmospheric CO2 change during past periods
of climate change (e.g., see CHAPTER III). If
circulation patterns did change, it is plausible
that the oceans would no longer be a net sink
for heat and CO2.
It is not known at what point ocean
circulation would be altered. For this analysis
we assumed that a 2°C increase in realized
warming would alter ocean circulation patterns
sufficiently to shut off net uptake of CO2 and
heat by the oceans. This would increase
atmospheric CO2 concentrations from 10-13%
by 2100, and would reduce the difference
between realized and equilibrium wanning as
the atmosphere warmed more quickly due to
the oceans' inability to continue to act as a
heat sink. As shown in Figure 6-27, this
feedback is sufficient to increase realized
warming up to 1.6°C by 2050 and 1.3-3.6°C by
2100 compared with the warming estimated for
the RCW case (assuming 2.0-4.0°C climate
sensitivities).
Methane Feedbacks
Increases in global temperature could
increase the amount of CH4 emissions due to
several feedback processes: (1) release of
methane from hydrates, which are methane
compounds contained in continental slope
sediments, as increasing temperatures
destabilize the formations; (2) additional
methane from high-latitude bogs due to longer
growing seasons and higher temperatures; and
(3) increased rate of methanogenesis from rice
cultivation. The amount of CH4 that could be
released from each of these feedback
processes, and the rate at which any releases
might occur, are highly speculative. For each
process we have assumed that the rate of CH4
release is linearly related to the increase in
temperature, with each 1°C increase leading to
an additional 110 Tg from methane hydrates,
12 Tg from bogs, and 7 Tg from rice culti-
vation (Lashof, 1989). These methane
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Chapter VI: Thinking About the Future
FIGURE 6-26
INCREASE IN REALIZED WARMING
DUE TO RATE OF OCEAN HEAT UPTAKE
(Based on 3.0 Degree Sensitivity)
6
o
I
o
3 -
2 -
1985 2000
2025 2050
Year
2x I0"5m2/sec
RCW
-4 2
2x10 m /sec
2075 2100
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Policy Options for Stabilizing Global Climate
FIGURE 6-27
INCREASE IN REALIZED WARMING
DUE TO CHANGE IN OCEAN CIRCULATION
(Based on 3.0 Degree Sensitivity)
1985 2000
Ocean
Circulation
RCW
2025 2050
Year
2075
2100
VI-72
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Chapter VI: Thinking About the Future
feedbacks could have a major impact on
atmospheric CH4 concentrations -- by 2100
concentrations would increase to about 6900-
8050 ppb, compared with 4310-4550 ppb in the
RCW case. As shown in Figure 6-28, this
increase in CH4 would be sufficient to increase
realized warming relative to the RCW case
about 0.1-0.2°C by 2050 and 0.4-0.8°C by 2100
(assuming 2.0-4.0°C climate sensitivities).
Combined Feedbacks
In addition to the two separate
feedbacks discussed above, we analyzed the
combined impact of several types of
biogeochemical feedbacks. The following
specific feedbacks were included: (1) methane
from hydrates, bogs, and rice cultivation, as
previously discussed; (2) increased stability of
the thermocline, thereby slowing the rate of
heat and CO2 uptake by the deep ocean by
30% due to less mixing; (3) vegetation albedo,
which is a decrease in global albedo by 0.06%
per 1°C warming as a result of changes in the
distribution of terrestrial ecosystems; (4)
disruption of existing ecosystems, resulting in
transient reductions in biomass and soil carbon
at the rate of 0.5 Pg C per year per 1°C
warming; and (5) CO2 fertilization, resulting in
an increase in the amount of carbon stored in
the biosphere in response to higher
atmospheric CO2 concentrations at the rate of
0.3 Pg C per ppm increase (see Lashof [1989]
for further discussion).
The combined impact of these feedbacks
on realized warming is an increase of 0.2-0.7°C
by 2050 and 0.7-2.2°C by 2100 relative to the
RCW case (assuming 2.0-4.0°C climate sensiti-
vities; see Figure 6-29); the increase in
equilibrium warming is 0.2-1.3°C by 2050 and
0.6-2.6°C by 2100. These preliminary analyses
strongly suggest that biogeochemical feedbacks
could have a major impact on the rate of
climate change during the next century.
CONCLUSIONS
While the future will never be
anticipated with certainty, it is useful to
explore the consequences of alternative
plausible scenarios. The results of this
exercise suggest that even with sluggish rates
of economic growth and optimistic
assumptions regarding technical innovation,
the world could experience significant rates of
climate change during the next century.
Temperature increases reach 3-4°C by 2100
under our assumptions, and the world would
be committed to an additional warming of up
to 2.4°C at this date. With higher rates of
economic growth, which is certainly the goal of
most governments, significantly greater rates of
climate change are possible. With our
assumptions, which involve lower global energy
use than considered in many previous studies,
an average warming of 4-6°C could be
expected by 2100, with an additional
commitment of 1-4°C by that date. On the
other hand, by vigorously pursuing a variety of
technical and policy options simultaneously, it
would be possible to reduce the average rate
of warming during the next century by more
than 60%. Chapters VII and VIII of this
report explore options for implementing these
policies in more detail.
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Policy Options for Stabilizing Global Climate
FIGURE 6-28
INCREASE IN REALIZED WARMING
DUE TO METHANE FEEDBACKS
(Based on 3.0 Degree Sensitivity)
6
5 -
o
«
2 3
2 -
Methane
Feedbacks
RCW
1985 2000
2025
2050
Year
2075
2100
VI-74
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Chapter VI: Thinking About the Future
FIGURE 6-29
INCREASE IN REALIZED WARMING
DUE TO CHANGE IN COMBINED FEEDBACKS
(Based on 3.0 Degree Sensitivity)
6 -
Combined
Feedbacks
RCW
1985 2000
2075
2100
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Policy Options for Stabilizing Global Climate
NOTES
1. 1 GJ = 1 gigajoule = 0.948 million British
Thermal Units (Btu).
2. The sole exception is China, where
aggressive policies are assumed in both cases.
Slightly higher population growth is shown in
the Rapidly Changing World scenario based
on the sources of the alternative estimates (see
APPENDIX B). This could be attributed to a
relaxation of the one-child-per -family policy in
response to greater economic growth.
3. 1 EJ = 1 exajoule = 0.948 quadrillion Btu
(Quad).
4. This value includes all of the electricity
generated from gas, reflecting the assumption
that most of the synthetic gas used to produce
electricity by 2050 is generated from biomass
and is both produced and consumed in
integrated gasifier-combustion turbine units.
5. 1 Pg = 1 petagram = 1015 grams.
6. 1 Tg = 1 teragram = 1012 grams.
7. 1 TW = 1 terawatt = 1012 watts = 31.54
EJ.
8. In the Slowly Changing World scenario this
rechanneling effect is assumed to decrease
growth in CFC demand by 63% in developed
countries and by 50% in developing countries.
In the Rapidly Changing World scenario the
baseline growth rates are increased by a factor
of 1.7 to reflect the higher rate of economic
growth, but participation is assumed to be
100% in developed countries and 75% in
developing countries. Rechanneling reduces
the baseline growth rates by 63% in
developing countries (rechanneling does not
affect developed countries in this scenario as
100% participation in the Protocol is
assumed).
9. Participation is assumed to be 100% in
industrialized countries and 85% in developing
countries; rechanneling reduces the baseline
growth rates of non-participants by 75%.
10. Plantation products decay at various rates
at the end of each rotation; no attempt to
protect this carbon from oxidation is assumed.
11. Estimates of equilibrium warming
commitments greater than 6°C represent
extrapolations beyond the range tested in most
climate models, and this warming may not be
fully realized because the strength of some
positive feedback mechanisms may decline as
the Earth warms.
12. The path to 2025, however, is not
identical. The GISS scenarios are referenced
to the atmospheric composition of 1960,
whereas our scenarios are referenced to the
estimated pre-industrial atmospheric
composition. Thus, the warming commitment
in 2000 is already 2.2°C in the RCW, whereas
it is only 1.9°C in the GISS A scenario.
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CHAPTER VII
POLICY OPTIONS
FINDINGS
• Many alternative policies are available
that could be used to promote reductions in
greenhouse gas emissions, including market
incentives, research and development
programs, regulations, and information
programs. Choosing among these options will
require a detailed evaluation of numerous
criteria, including effectiveness in reducing
emissions, economic impacts, administrative
feasibility, enforceability, and compatibility
with other environmental and social goals.
• Defining goals is an important issue in
formulating policy responses to global
warming. In the short run, the goal proposed
by Congress for study in this report --
stabilizing greenhouse gas concentrations -- is
a costly, perhaps impossible, goal given current
economic expectations and expected
technological developments. Several states are
now assessing the feasibility of reducing
greenhouse gas emissions up to 20% over the
next 10-20 years.
• If we assume that energy-related
greenhouse gas emissions in the U.S. and
elsewhere will continue increasing in the
absence of government action, policies to
achieve significant reductions may require
major economic changes. However, further
study is necessary to assess the likely cost of
such measures, and many initial steps -
particularly those to improve energy efficiency
-- may have negative or very low costs, because
they would produce large savings. Policies
adopted today may substantially lower the cost
of future actions by redirecting research and
development priorities to technologies that
lower greenhouse gas emissions.
• Near-term actions to reduce greenhouse
gas emissions will be necessary if it is decided
to limit the concentrations of greenhouse gases
and facilitate future reductions. Atmospheric
concentrations of most greenhouse gases will
decline much more slowly than emissions.
Putting off actions to reduce emissions would
give us time to increase our knowledge of the
risks and to refine policy options, but delay
also could substantially increase the cost and
reduce the effectiveness of policy responses.
We will need time to agree on and implement
policy responses since rapid changes in
patterns of energy use and the industrial
infrastructure responsible for emissions are
likely to be disruptive and expensive.
• There is an important distinction
between short-term and long-term policy
options. In the short term, the most effective
means of reducing emissions is through
strategies that rely on pricing and regulation.
In the long term, policies to increase research
and development of new technologies and to
enhance markets through information
programs, government purchases, and other
means could also make a major contribution.
• If limiting U.S. and global emissions of
greenhouse gases is desired, government action
will be necessary. Market prices of energy
from fossil fuels, products made with CFCs,
forest and agricultural products, and other
commodities responsible for greenhouse gas
emissions do not reflect the costs associated
with the risk of climate change. As a result,
increases in population and economic activity
will cause emissions to grow in the absence of
countervailing government policies to modify
and/or supplement market signals.
• Policy preferences will vary among
nations. However, nations can choose among
many complementary policy options to reduce
emissions consistent with governmental
systems and other societal needs.
• The most direct means of allowing
markets to incorporate the risk of climatic
change is to assure that the prices of fossil
fuels and other sources of greenhouse gases
reflect their full social costs. It may be
desirable to impose emission fees on these
sources according to their relative contribution
to global warming in order to accomplish this
goal. Imposing fees would also raise revenues
that could finance other programs. The
acceptability of such fees will vary among
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Policy Options for Stabilizing Global Climate
countries, but would be enhanced if they are
equitably structured.
• Regulatory programs would be a
necessary complement when pricing strategies
are not effective or produce undesirable
impacts. In the U.S., greenhouse gas
emissions are influenced by existing federal
regulatory programs to control air pollution,
increase energy efficiency, and recycle solid
waste. Reducing greenhouse gas emissions
could be incorporated into the goals of these
programs. New programs could focus directly
on reducing greenhouse gas emissions through
such requirements as emissions offsets (e.g.,
tree planting), performance standards, or
marketable permits.
• Over the long term, other policies to
reduce emissions may be needed, and these
can complement pricing and regulatory
strategies. Other policy options include
redirecting research and development priorities
in favor of technologies that could reduce
greenhouse gas emissions, developing and
operating information programs to build
understanding of the problems and solutions,
and the selective use of government
procurement to promote markets for
technological alternatives.
• State and local government policies in
such areas as utility regulation, building codes,
waste management, transportation planning,
and urban reforestation could make an
important contribution to reducing greenhouse
gas emissions.
• Voluntary private efforts to reduce
greenhouse gas emissions have already
provided valuable precedents for wider action
and could play a larger role in the future.
• Government policy is already exerting
considerable influence on the rate of growth in
greenhouse gases. Clean Air Act provisions to
attain and maintain National Ambient Air
Quality Standards by regulating emissions of
volatile organic compounds, nitrogen oxides,
and carbon monoxide will not only produce
cleaner air but also significantly affect
greenhouse gases or their precursors. Major
reductions of sulfur dioxide to 10 million tons
below 1980 levels and of nitrogen oxides to 2
million tons below projected year 2000 levels
will reduce greenhouse gas emissions by
greatly encouraging energy efficiency. Phasing
out CFCs, carbon tetrachloride, methyl
chloroform, and hydrochlorofluorocarbons
(HCFCs) in accordance with the Montreal
Protocol and the Clean Air Act will
substantially reduce emissions of greenhouse
gases as well as protect the stratospheric ozone
layer.
• Policies to create further incentives to
improve energy efficiency, promote renewable
energy technologies, encourage tree planting,
and similar strategies may have the potential
to achieve substantial further emissions
reductions.
The President's proposed program for
planting a billion trees a year will produce
substantial benefits for wildlife, soil
conservation, urban amenity, and energy
saving, as well as directly take up CO2 from
the atmosphere. The increase in the federal
gasoline tax enacted in the Budget
Reconciliation Act of 1990 will reduce
emissions by encouraging energy efficiency in
road transportation. Increased funding
requested in the 1991 budget for research and
development in solar and renewable energy
and energy conservation will be important in
identifying and developing technologies that
will allow us to meet our energy needs in
environmentally efficient ways. New energy
saving appliance standards promulgated by the
U.S. Department of Energy will increase
energy conservation and reduce demand.
• Many of the policies necessary to limit
the buildup of greenhouse gases, such as
improving energy efficiency and reversing
deforestation, would produce other substantial
short-term benefits. Therefore, it is very likely
that additional policies can be found that,
when analyzed, have sufficient benefits in areas
not subject to the scientific and other
uncertainties of climate change to justify their
costs. Such policies can therefore be
implemented in a manner that is consistent
with other important economic, social, and
environmental goals.
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Chapter VII: Policy Options
INTRODUCTION
If the government desires to stabilize
the concentration of greenhouse gases at or
near current levels, short-term actions must be
considered. Market forces do not reflect the
risks of climate change and therefore, barring
government intervention, emissions -- and the
risks of climate change -- can be expected to
grow. The costs of taking action may increase
with time; it takes many years to develop new
technologies, implement policies, and replace
the existing capital stock. There is also a long
lag time between changes in emissions and
consequent changes in the chemistry of the
atmosphere, so that even with large reductions
in emissions, atmospheric concentrations of
some greenhouse gases may decline very slowly
or even increase. The earth would continue to
warm, and the climate may change for decades
after atmospheric concentrations of
greenhouse gases were stabilized.
Near-term government action to reduce
emissions may consist entirely of policies that
will contribute other substantial short-term
benefits. The justification for policies that
reduce greenhouse gas emissions may,
therefore, be much greater than it would
appear from a traditional comparison of costs
and benefits. Decisions not to take action to
reduce emissions could also facilitate the
adoption of policies that result in increased
emissions; such policies presumably would be
less likely to be adopted if they were to
contravene the purpose of other programs.
This is a significant risk as we discuss later in
this chapter; several recently proposed policies
have the potential to significantly increase
greenhouse gas emissions.
The government may pursue many
policy alternatives to reduce greenhouse gas
concentrations. In the short term, economic
incentives and regulatory strategies will be
most effective, but in the long run other
policies will complement and support these
approaches. Strategies to reduce greenhouse
gas emissions can contribute to other goals,
including economic growth, enhanced energy
security, and a cleaner environment. Chapter
V shows the wide range of measures available
to limit greenhouse gas emissions. Many of
these measures are nearly cost-competitive or
are expected to be so soon. Is government
intervention to reduce emissions therefore
necessary? The analysis done for this report
strongly suggests that without such action
emissions will increase significantly. Without
government intervention, there may be
insufficient market incentive to develop and
adopt the measures identified in Chapter V.
In the absence of government
intervention, market prices will not reflect the
cost to society of activities that are detrimental
to the environment. Accordingly, we will not
see a reduction in consumer demand for goods
and services that increase environmental risk.
The obstacles to bringing about
consumer response to environmental dangers
are particularly challenging for global
problems like ozone depletion and the
greenhouse effect. In this situation, there is
the danger of what is commonly termed the
"tragedy of the commons," the ecological
destruction that can occur from uncontrolled
use of shared resources like the atmosphere.
There is probably no country for which
reductions in global wanning provide an
adequate economic incentive to reduce
greenhouse gas emissions unilaterally, even
though such action could yield substantial
global benefits. From any one country's
viewpoint, the costs of controlling emissions
may exceed the benefits since, without
international agreement, reductions achieved
by one nation may be offset by another.
Therefore, even though the entire world may
be better off as a result of efforts to lower
emissions, new economic incentives are
necessary to lead the market to a socially
efficient outcome.
There are many possible policy
responses for reducing greenhouse gas
emissions; no one policy is likely to be totally
effective without other supporting programs.
However, as previously mentioned, consumers
are not likely to reduce their demand for
products and services that produce emissions
of greenhouse gases unless the cost begins to
exceed the benefits derived. In addition, other
policies will be much less effective in the
absence of economic incentives. In the short
term, economic incentives and regulatory
programs are likely to be the most effective
policies. In the long term, research and
development (R&D), information and
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Policy Options for Stabilizing Global Climate
educational activities, government
procurement, and other policies can make a
substantial contribution.
The policies discussed here are most
applicable to the United States. However,
many of the ideas reviewed are likely to be
potentially relevant to other countries.
Policies most suitable for developing countries
are discussed in Chapter VIII. Some programs
developed in the U.S., such as energy
conservation programs financed by electric
utilities, may have even greater relevance for
developing countries, which have higher
interest costs and a greater need for new
generating capacity.
GOALS
The choice of goals is a critical issue in
thinking about the global warming problem.
This study began with a request to identify
policies that could stabilize greenhouse gas
concentrations; for reasons discussed in
Chapter VI, this goal may be extremely
difficult to achieve, although some other
studies have suggested otherwise (Mintzer,
1989). It is less obvious what goals ought to
guide policymakers in responding to potential
global warming.
Several legislative proposals have been
framed to meet the goal proposed by the
Toronto Conference discussed in Chapter VIII:
to reduce emissions of carbon dioxide (CO2)
20% by the year 2005. The government of
Sweden has already agreed to limit its
emissions of carbon dioxide to current levels.
Proposals have also been made to limit
greenhouse gas emissions on the basis of
impacts. For example, a 1988 meeting of
experts at Bellagio, Italy, proposed that the
rate of global warming should not exceed
0.1°C per decade, a rate based on evidence of
past adaptation by flora and fauna to changes
in temperature.
These alternative goals reflect very
different policy approaches, with substantially
different potential environmental and
economic consequences. Approaches based on
emissions are most easily measured and
enforced, at least insofar as they are applied to
the commercial use of fossil fuels. Approaches
based on limiting greenhouse gas
concentrations come closer to addressing the
underlying problem, but without precise means
of attributing emissions to concentrations
there are difficulties in devising programs to
assure compliance. These problems are still
greater with approaches based on rates of
change or impacts, both of which require even
more scientific precision and understanding.
Ultimately, a workable international
agreement to address the problem will require
goals that are readily understood and
translated into enforceable requirements by
implementing authorities. This problem is
likely to be addressed in the ongoing
intergovernmental process discussed in
Chapter VIII.
CRITERIA FOR SELECTING POLICY
OPTIONS
This chapter, and the chapter that
follows, offer a wide variety of policy
alternatives with differing advantages and
disadvantages. The U.S. Environmental
Protection Agency (U.S. EPA) tested the
effectiveness of some of these options, as
discussed in Chapter VI. Much more detailed
analysis would be necessary prior to any effort
to design a program for reducing greenhouse
gas emissions, and numerous additional factors
would have to be considered (McGarrity,
1983).
An initial consideration is effectiveness
in reducing greenhouse gas emissions.
Regulations, such as efficiency standards for
automobiles and appliances, may appear to be
the most predictable and reliable means of
reducing greenhouse gas emissions. This is
not necessarily so, however, as regulations may
have unintended offsetting effects; for example,
consumers have retained older, less efficient
cars longer since such regulations went into
effect, slowing the improvement in the overall
efficiency of the vehicle fleet. Similarly
troubling is the knowledge that automobiles
usually travel fewer miles per gallon on the
road than is indicated by the mileage ratings.
Economic incentives may be more effective,
although their results are also not always
predictable. In the long run, R&D efforts may
produce much greater results — particularly if
complemented by policies that create market
incentives, such as energy taxes. (Many
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Chapter VII: Policy Options
strategies are complementary and not at all
inconsistent, as discussed below.)
Cost is one key issue. Some evidence of
the costs of policies to reduce emissions is
presented in this chapter, and U.S. EPA has
begun a separate cost study. Some of the
difficulties in evaluating costs are discussed
further below. Economic efficiency is a closely
related consideration. Policies should
encourage the most productive use of available
resources, thereby minimizing the cost of
achieving a given objective.
Public acceptability is also important.
Taxes and economic incentives are often
recommended by economists as the most
efficient means of inducing behavioral changes,
but such policies may be unrealistic because of
popular resistance.
Regional and income equities are often
an issue with energy policy proposals. Raising
energy prices may disproportionately affect
lower-income groups; restrictions on coal
production may damage the economies of
coal-producing regions. These considerations
assume even greater importance in the
international arena as any international accord
to limit emissions must allow for enormous
differences in national resources and needs.
The effect of policies on other societal
goals, both positive and negative, may also be
important. Energy conservation incentives that
reduce oil imports may contribute to energy
policy objectives and improve the balance of
trade. Tree-planting programs may improve
other measures of environmental quality by
removing air or water pollutants. On the other
hand, programs that impose large costs on the
economy, or that require imported technology,
may hamper economic goals.
Administrative burdens may be a factor
with some policies. For example, some forms
of regulatory programs require substantial data
collection and paperwork and impose
substantial time and monetary demands on
both industry and government. In contrast,
taxes and some economic incentive programs
are relatively free of paperwork and easier to
administer.
Legal and institutional constraints
complicate some policy choices. For example,
the use of environmental fees or taxes may
require new laws. Shared savings programs, a
strategy for promoting investments in energy
conservation, have not been widely utilized by
federal agencies, in part because of restrictions
on government procurement practices.
Enforceability is a concern with respect
to some strategies. For example, some
environmental regulations in the U.S. have
arguably suffered from lack of specificity,
making it difficult to detect and take action
against violators.
No single policy can simultaneously
satisfy all the criteria implied by the factors
listed above; some trade-offs are inevitable,
and the choices among different policy
proposals must reflect judgments about the
relative importance of these factors. Two
examples, based on two of the largest sources
of global energy consumption, automobiles
and space conditioning, illustrate some of the
issues. In the U.S., several approaches have
been considered to promote improved
automobile efficiency, including corporate
average fuel economy (CAFE) standards,
mandatory efficiency labeling, and government
supported R&D. (Details concerning these
policies are provided below.)
The standards approach has been the
most controversial. On the one hand, it
appears to offer the most certain promise of
efficiency improvements; new car efficiency did
improve substantially since standards went into
effect, and Greene (1989) concluded that
CAFE standards were perhaps twice as
influential as gasoline price. However, the
interest in further efficiency improvements has
declined substantially since oil prices began to
decline several years ago. There is also concern
that the standards resulted in some
unnecessary inefficiencies, benefitted foreign
car manufacturers, and encouraged an
undesirable market shift toward unregulated
light trucks. Many economists have argued that
gasoline taxes would be a much more effective
and easily administered policy alternative;
however, public support for a tax approach has
been lacking.
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Policy Options for Stabilizing Global Climate
Policies to promote improved building
efficiency encounter a still more complex set
of constraints because of the much larger
number of builders, the lack of simple
standards to measure efficiency, and the
fragmentation of political authority among
federal, state, and local jurisdictions.
Regulations currently exist for only certain
types of buildings (e.g., new homes) and
jurisdictions; the federal government has not
always applied accepted standards for
minimizing energy costs in its own buildings.
Proposed uniform national standards for new
homes were adopted in the 1970s but later
were rescinded because of technical difficulties
and political opposition. Market incentives are
also not easily implemented, because retail
electricity and gas prices are controlled at the
state level and usually reflect average costs
rather than the marginal cost of new supply.
Innovative approaches have been developed to
create incentives for consumers and investors
to take advantage of low-cost opportunities for
cost reductions. Many utilities offer low-cost
energy audits, energy labels, and rebates for
the installation of efficient equipment. A few
utilities have begun to offer direct payments
for the incremental cost of efficiency
investments that exceed minimum standards.
The federal government has also achieved
some notable successes through its R&D
efforts, including the development of more
efficient lights and heat pumps.
A recent report to Congress by the U.S.
Department of Energy (U.S. DOE), "A
Compendium of Options for Government
Policy to Encourage Private Sector Responses
to Potential Climate Change," provides a much
more detailed catalog of policy instruments
and their attributes. The report reviews four
broad categories of policies roughly
corresponding to those considered in this
report: regulation, fiscal incentives,
information, and research development and
demonstration. The general attributes of each
are described in terms of efficiency,
information requirements, distributional
effects, political sustainability, and applicability
to greenhouse gas issues. The application of
alternative policy instruments to different
sectors of the economy is then assessed in
terms of seven screening criteria: applicability,
efficacy, time frame necessary to be effective,
focus, decisionmaker sensitivity required,
current level of knowledge, and linkage to
other goals. Some particularly promising
options are emphasized, but U.S. DOE's
report is similar to this one insofar as it avoids
recommending specific policies: "We have
sought to offer a menu of the options that are
evaluated based on an initial systematic
screening" (U.S. DOE, 1989).
COMPLEMENTARY STRATEGIES TO
REDUCE GREENHOUSE GAS EMISSIONS
The policies described in this chapter
are likely to be most effective when used in
combination and, wherever possible, linked to
the attainment of other national goals. Pricing
and regulatory strategies are the most effective
policies in the short term; however, the other
policies reviewed in this section can
complement and enhance pricing and
regulatory approaches. In the long run,
government-supported R&D, information
programs, and other market-enhancing
activities can make a significant contribution.
Because government action to reduce
greenhouse gas emissions will often be closely
related to other national policies, programs
must also be carefully crafted to meet several
goals simultaneously (IEA, 1987).
Improving the efficiency of the U.S.
economy is closely related to concerns about
the country's economic competitiveness. While
the U.S. has reduced its energy intensity
substantially, our principal economic
competitors have done even better and can
offer more efficient technologies in many
areas. Per capita energy consumption in the
U.S. remains more than double that of Europe
or Japan. Japanese industry uses half as much
energy per dollar of value added as does
industry in the U.S., although they spend
about as much because energy prices are
higher (Zimmerman and Reid, 1988; Ravin
and Durning, 1988). Efficiency investments
would make billions of dollars in capital
available for other investments (Rosenfeld and
Hafemeister, 1988). Oil imports are also a
growing negative influence on the U.S. balance
of trade, accounting for roughly a fourth of the
merchandise trade deficit - more than any
other single item (Chandler et al., 1988).
Policies for reducing greenhouse gas
emissions may also complement efforts to
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Chapter VH: Policy Options
address concerns raised by recent growth in oil
imports and potential risks to U.S. energy
security (U.S. DOE, 1987c). Net oil and
petroleum imports have increased from 27%
of U.S. supply in 1985 to about 42% in 1989,
and current forecasts indicate imports could
exceed 50% by the mid-1990s (U.S. DOE,
1987c). By comparison, imports accounted for
35% of supply before the 1973 embargo and
43% before the 1979 embargo.
As discussed in Chapter IV, oil
consumption for transportation is one of the
largest sources of U.S. greenhouse gas
emissions, as well as a major contributor to
projected increases in global emissions.
Transportation also accounts for almost two-
thirds of U.S. oil consumption. Further
improvements in auto efficiency could
therefore contribute to both decreases in
greenhouse gas emissions and energy security
objectives (MacKenzie, 1988).
Complementary strategies are very
important in the buildings sector, where the
effectiveness of pricing strategies is limited by
extreme first-cost sensitivity, and the stringency
of regulation is likely to reflect considerable
compromise. Studies show that selective
financial incentives in combination with
information and training programs can be
highly effective in promoting innovation not
covered by standards, creating incentives for
early adoption of standards, and enhancing
compliance with standards. The result can be
performance that is substantially better than
mere compliance with minimum standards
(Vine and Harris, 1988).
Complementary strategies can also work
well to achieve the goal of reducing carbon
emissions from automobiles. To achieve this
goal, which is clearly consistent with efforts to
promote higher average fuel economy,
consumers must be able to evaluate the
relative fuel efficiency of automobiles; federal
fuel efficiency tests, gas mileage guides, and
other information programs promote this
goal.1 Manufacturers have rightfully noted
that consumer interest in fuel efficiency has
declined with lower gasoline prices. Higher
gasoline taxes, gas guzzler fees, or some other
form of economic incentive is necessary to
stimulate demand for efficiency.
Better management of solid wastes can
reduce methane emissions. States with the
most effective programs often combine some
or all of the following policies: regulations on
landfills, deposits on recyclable materials, tax
incentives for recycling companies, and
government procurement policies that
promote purchase of recycled materials (Shea,
1988).
Research and development programs
can assist on the supply side by accelerating
the development and testing of new
technologies. Procurement programs can
provide an initial market and extensive testing
for concepts prior to wider marketing.
Minimum fuel economy standards fill a
different role by providing clear targets and
reducing market uncertainty, but regulations
must be carefully structured to allow adequate
time for adjustment, to avoid conflicts with
other social goals and to preserve fair
competition.
There is some concern that other
national policies for reducing automobile oil
consumption and improving urban air quality
may lead to increased carbon emissions - for
example, legislation promoting large-quantity
production of methanol from coal (see
CHAPTER V), particularly if vehicles using
such fuels are permitted to be less efficient as
provided for in recent federal legislation.
Federal and state governments have also
been considering air pollution regulations that
could unintentionally exacerbate global
warming. The problem is illustrated by the
ongoing debate over acid rain legislation.
Acid rain is caused in part by sulfur dioxide
and nitrogen oxides emissions from electric
utility powerplants. Some of the methods to
limit these emissions could result in greater
CO2 emissions. For example, the use of
scrubbers to control sulfur dioxide emissions
from coal-fired or oil-fired powerplants would
increase CO2 emissions slightly because of the
additional fuel required to operate the
scrubbers. However, strategies that rely on
natural gas or demand-side reductions would
reduce carbon emissions (Centolella et al.,
1988). Thus, an important priority for acid
rain mitigation strategies should be to consider
the global warming impacts of alternative acid
rain programs.
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Policy Options for Stabilizing Global Climate
Just as strategies to reduce greenhouse
emissions must be applied in combination in
order to be maximally effective, so too must
we work together at all levels of government,
as well as in the private sector.
Many short-term actions to reduce
greenhouse gas concentrations could be
implemented today on the basis of existing
legislative authority. Indeed, some policies
directed toward this objective are already
under consideration. For example, agencies
could make greater use of the environmental
impact statement process to consider the
extent to which their major projects will
contribute to or be affected by climate change.
The President's Council on Environmental
Quality has done an analysis of projects that
might warrant discussion of climate change
issues and may issue guidelines for other
agencies. U.S. EPA, which is legally required
to review draft impact statements, has used its
authority in at least one instance to comment
on the additional greenhouse gas emissions
that might result from actions proposed by the
Federal Energy Regulatory Commission
(FERC).
Much more could be done to improve
the federal government's energy management
within existing legislative authority, beginning
with much more disaggregated reporting of
energy use by agencies. The laws creating the
Federal Energy Management Program require
an examination of opportunities for energy-
saving alternatives in federal buildings. Such
analysis is to be done on the basis of life-cycle
costs, reflecting marginal fuel costs, and a 7%
real discount rate - terms intended to favor
conservation, as compared with using average
costs and a higher discount rate (Energy
Security Act, PL 96-294, Section 405). The
U.S. Department of Energy proposed
implementing regulations in 1980, but final
regulations were never completed. An
Executive Order was initiated in 1990,
however, that could reduce energy
consumption in federal buildings by 10% in
1995.
Other short-term possibilities follow
from some of the recent and pending agency
decisions discussed above, such as ongoing
consideration of rules to promote demand-side
bidding by FERC and reconsideration of
CAFE standards by the U.S. Department of
Transportation (for further discussion see
ADDENDUM TO CHAPTER VII).
The Cost Issue
Cost is obviously an important basis for
comparing policy alternatives. As discussed in
Chapter I, U.S. EPA recognizes the need for
detailed analysis of the costs of alternative
means of reducing greenhouse gas emissions
and has initiated a separate cost study. This
report reviews only policy options; costs are
only one of many factors that will have to be
examined in detail before recommendations
can be made.
While no effort has been made to
compare the costs of alternative policies, this
chapter identifies numerous examples of
policies that appear to offer opportunities for
low-cost reductions in greenhouse gas
emissions. Recent studies have identified
substantial remaining opportunities for cost
savings through investments in energy
conservation. For example, a recent detailed
study of electricity use in Michigan concluded
that currently projected residential electricity
demand in the year 2005 could be reduced by
close to one-third for a total cost substantially
less than the marginal cost of existing
powerplants (see Figure 7-8). The cost of
storing carbon by tree planting is also very
modest, although costs can be expected to rise
as programs increase in scale and land
availability becomes a constraint.
The policy examples cited in this
chapter also serve to make another important
point about the cost issue. Since the policies
available to reduce greenhouse gas emissions
also produce other benefits -- energy
conservation, enhanced air or water quality,
economic development, etc. - the costs
attributable to reducing greenhouse gas
emissions are often difficult to isolate. For
example, a tree-planting program may reduce
the risks of flooding, improve water quality,
enhance local air quality, and provide fruit as
well as store carbon dioxide. An energy
conservation program may reduce energy
imports, improve air quality, and save
consumers money. In these circumstances, the
VII-8
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Chapter VII: Policy Options
total cost of the measure may significantly
overstate the cost of reducing greenhouse gas
emissions.
Cost estimates may also be misleading
insofar as they necessarily reflect existing
opportunities and short-term projections. The
analysis in this report highlights the
importance of emphasizing long-term,
cumulative emissions; for this reason, research
and development to improve technologies and
lower costs may be the highest priority, and
the fact that the current cost of a technology
is high makes it even more important.
Recent experience developing
alternatives to chlorofluorocarbons (CFCs) in
response to concerns about ozone depletion
illustrates the importance of this point. In
1984, use of CFCs was growing rapidly, and
studies of the feasibility and costs of
alternatives prepared by industry and U.S.
EPA contractors were extremely pessimistic.
For some applications, particularly solvents,
substitutes for CFCs could not be identified.
However, the signing of the Montreal Protocol
in September 1987 created a significant market
incentive to explore alternatives, and as a
consequence, promising new substitutes have
been announced with increasing frequency at
much lower cost than was previously assumed.
At least with respect to CFCs, pre-regulatory
experience was not an adequate indication of
cost since alternatives were only seriously
explored after regulations were implemented.
The ozone depletion problem and
international regulation of CFCs resulted in a
worldwide race to identify, test, and engineer
acceptable substitutes. There maybe additional
costs associated with this kind of crash effort,
as discussed with respect to the issue of timing
(see next section). Costs may therefore be
difficult to distinguish from government policy
choices.
IMPLICATIONS OF POLICY CHOICES
AND TIMING
The potential cost of government action
to reduce greenhouse gas emissions may be
much less than it would appear if such action
serves other important economic or
environmental objectives. Most of the
measures proposed to reduce emissions are
already of substantial public interest - for
example, policies that promote energy
efficiency, reductions in use of CFCs, efforts to
halt deforestation, and other desirable social
policies -- so that the threat of a global
warming is often simply another reason to
implement such policies. The incremental cost
of taking actions to limit global warming today
may therefore be modest.
The technical feasibility of implementing
various measures that have been proposed for
limiting global warming has already been
addressed in Chapter V. However, since the
threat of global warming has so far not been
an important consideration in government
policymaking, it is important to note the other
benefits of these measures. For example,
serious consideration is being given to
eliminating emissions of CFCs because of their
impact on the ozone layer. In addition, a
substantial number of states are promoting
investments in energy-efficient technology in
order to reduce energy costs and to meet the
need for new electric generating capacity.
Also, federal and state authorities are
promoting waste reduction and recycling as
alternatives to land disposal because of the
high cost and environmental risks associated
with traditional disposal methods. Finally, a
large and growing international effort has been
organized to slow tropical deforestation
because of its impact on economic
development and the quality of life in many
developing countries.
For several reasons, near-term action
may be necessary to stabilize greenhouse gas
concentrations. For political and economic
reasons, actions cannot be immediately
implemented once it is agreed they are needed,
and for reasons having to do with atmospheric
chemistry, concentrations of greenhouse gases
and the attendant risks will decline only
gradually even after actions are implemented.
Policy development and implementation
can be a lengthy process, particularly at the
international level. Roughly a decade was
required for the process that led to
international agreement to reduce emissions of
CFCs embodied in the Montreal Protocol, and
it will take another decade to implement the
agreed-upon reductions. An agreement to
reduce emissions of greenhouse gases
VII-9
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Policy Options for Stabilizing Global Climate
associated with the use of fossil fuels and with
deforestation could take even longer to
achieve: the activities responsible for CO2
emissions are more economically valuable, the
distribution of emissions is greater, the
responsible countries have diverse economies
and less shared interests, and the difficulty of
implementing alternatives may be greater.
Implementing new technologies can also
often be time-consuming. Most emissions
result from activities that are fundamental to
supporting the global economy (transportation,
space conditioning, industrial production, land
clearing, etc.); therefore, rapid introduction of
new technologies for some uses could be very
disruptive. Once a technology is cost-effective,
it may take years before it achieves a large
market share, and decades more for the
existing capital stock to be replaced. The
historical pattern of gradual displacement of
old energy sources by new sources is shown in
Figure 7-1. Government policy may be able to
significantly accelerate this transition, although
it is debatable whether such efforts have been
very successful in the past.
New end-use technology with greater
efficiency can replace existing technologies
more quickly: it takes 5-10 years to develop
new automobile models, and the existing fleet
is largely replaced over 8-12 years; major home
appliances and space heating and conditioning
systems are in use for 10-20 years, and
industrial equipment, for 20-40 years.
Buildings may be used for 40-100 years or
more, however, and the reduction in energy
requirements that can be achieved (per unit)
as a result of remodeling is more limited than
what can be achieved in newly constructed
buildings. Thus, depending on the sector, it
traditionally takes roughly 20-50 years to
substantially alter the technological base of
industrial societies, and the cost of reducing
emissions could rise dramatically as the time
allowed for achieving these reductions is
decreased. While the rate of change can be
higher in rapidly developing countries, once
the industrial infrastructure is built, it will
normally be many years before it is replaced.
This process will be naturally accelerated if
new technologies become sufficiently attractive
and government policies can encourage more
rapid retirement of existing buildings and
equipment. Nevertheless, such efforts are likely
to be more expensive and technically difficult.
Once greenhouse gases have entered the
atmosphere, they continue to affect climate for
decades. Even if all anthropogenic emissions
of carbon dioxide could be suddenly
eliminated, it may take more than a century
for the oceans to absorb enough carbon to
reduce the atmospheric concentration of CO2
even halfway toward its pre-industrial value
(see CHAPTER II). With continued
emissions, the time required to reduce excess
concentrations by the same percentage
increases further. For CFCs and N2O, it
would be more than 50 years before their
excess concentrations declined by half even if
all anthropogenic emissions were eliminated.
Only methane responds relatively quickly -
the excess concentration would fall by 50% in
less than a decade after anthropogenic
emissions were eliminated (see Figure 7-2).
The climate response also lags behind
the radiative forcing imposed by changes in
atmospheric composition (see CHAPTER III).
Due to the heat capacity of the ocean, the
global average temperature will rise more
slowly than if climate were continuously in
equilibrium with the changing composition of
the atmosphere. The climate will also cool
more slowly if trace-gas trends are reversed.
Consequently, any strategy that involves
responding to climate impacts is very risky:
once climate change occurs even draconian
measures would not reverse the process for
decades.
The effect of delaying policy responses
is illustrated by Figure 6-23 (see CHAPTER
VI), which shows the potential increase in
realized warming that results from simply
waiting before implementing a defined set of
policies.
IMPORTANCE AND IMPLICATIONS OF A
LONG-TERM PERSPECTIVE
In thinking about policies to address
global warming, it is critical not to lose sight
of the long-term nature of the problem.
Short-term policy choices may be very
important, for the reasons noted above.
However, the choices outlined below are
VIMO
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Chapter VII: Policy Options
FIGURE 7-1
U.S. ENERGY CONSUMPTION BY FUEL SHARE
(Percentage of Total U.S. Energy Consumption)
Nuclear
Hydropower
Natural Gas
Petroleum
Wood Fuel
Coal
1900 1910 1920 1930 1940 1950 1960 1970 1980
Year
Source: U.S. DOE, 1987a.
VII-ll
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Policy Options for Stabilizing Global Climate
FIGURE 7-2
ATMOSPHERIC RESPONSE TO EMISSIONS CUTOFF
(Percent Reduction Relative To Year of Emissions Cutoff in 2000)
125
100
75 -
u
50 -
25
0 h
2000
v Realized Warming
2025
2050
Y«ar
2075
2100
VII-12
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Chapter VII: Policy Options
designed to address very long-term needs as
indicated by the scenarios tested in Chapter
VI, which extend to the year 2100. In this
time frame, it must be expected that
substantial changes will occur in technologies
and lifestyles that will have a significant effect
on the global warming problem. Research and
development strategies are of the utmost
importance in providing long-term solutions.
Improvements in nuclear energy systems,
renewable energy technology, and other non-
fossil sources of energy could make an
enormous difference in the scenarios
considered here, and research begun today
could help provide these technologies.
A long-term focus also helps to identify
constraints and opportunities associated with
alternative technologies. For example, natural
gas technologies are a promising interim
means of reducing CO2 emissions, but the
analysis presented in Appendix C suggests the
supply of natural gas is too limited to offer a
long-term, worldwide substitute for coal.
Similarly, a long-term global shift to nuclear
energy would create concerns about both the
supply of uranium and the proliferation
problems associated with worldwide shipments
of materials suitable for weapons production
(Williams, 1988). Large-scale reliance on
biomass and solar energy leads to concerns
about land availability and conflicts with
resources needed for food production.
INTERNALIZING THE COST OF
CLIMATE CHANGE RISKS
One of the most potentially effective
ways to promote energy efficiency and other
strategies to reduce greenhouse gas emissions
is to increase the cost of activities responsible
for emissions to reflect the risks of climate
change. The government could increase the
price of fossil fuels and other sources of
greenhouse gases by imposing taxes or fees,
while reducing the price of desirable
alternatives by providing direct or indirect
subsidies. Prices of some relevant
commodities, particularly electricity, are
already regulated and could be adjusted to
promote reduced emissions. Such policies
have already been adopted to varying degrees
in some states to promote other economic and
environmental goals. However, the limitations
of economic approaches should also be
recognized; other types of policies may be
more effective in redressing some market
failures, and these can complement policies
based on adjusting prices.
Evidence of Market Response to Economic
Incentives: Energy Pricing
Proper pricing of energy to reflect the
reality of the global warming threat could
substantially reduce emissions. It was long
assumed (based on historical data) that there
was a constant relationship between the rate of
growth in energy use and the rate of growth of
GNP (Weinberg, 1988). The historical
constancy of the relationship was often
explained as a consequence of technology and
stable or declining fuel prices. The chief flaw
in this argument was its failure to anticipate
the effects of rising real energy prices. During
the century preceding 1973, the relative price
of energy had fallen, while energy efficiency
improved slowly as the capital stock turned
over (Edmonds and Reilly, 1985). However,
between 1973 and 1985 the price of energy
rose, relative to other goods and services, and
in accordance with basic economic theory,
growth in energy demand slowed, and by some
measures, declined significantly.
Prior to 1973, U.S. energy demand grew
at a rate only slightly less than the rate of
growth in real GNP. Had pre-1972 energy-use
trends continued, by 1984 the United States
would have been consuming almost 40% more
energy than it actually did (U.S. DOE, 1987c).
But efficiency improvements induced by
significant oil price increases enabled the U.S.
to hold energy use to 1973 levels while
expanding the economy by 40%. By one
estimate, energy efficiency improvements now
save the U.S. economy $160 billion annually.2
U.S. energy efficiency improved
markedly between 1973 and 1985 while energy
prices rose markedly (see Figure 7-3).
However, efficiency improvements in the U.S.
and many other industrialized countries have
leveled off in recent years. Whereas energy
intensity in the nations of the European
Economic Community (EEC) declined 20%
from 1973 to 1982, the corresponding figure
for 1982 to 1986 is 2.4% (EEC, 1988). One
VII-13
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Policy Options for Stabilizing Global Climate
FIGURE 7-3
35
10
5 -
ENERGY INTENSITY REDUCTIONS
1973-1985
(Thousand Btu Per Dollar GNP; 1985 Dollars)
1973 1975 1977 1979 1981 1983 1985
Year
Source: Chandler et al., 1988
VIM4
-------
Chapter VII: Policy Options
important factor is that oil prices have fallen
continuously since 1981. Oil prices dropped
precipitously in 1986: world oil prices fell
from about S25 per barrel in January 1986 to
about S10 per barrel in July 1986. Prices have
since fluctuated in the S15 per barrel range.
Adjusted for inflation, gasoline prices in the
first half of 1988 were 27% less than in 1985
and 48% less than in 1980 (Geller, 1989). The
rapid decline in world energy prices has slowed
the rate of improvement in energy efficiency.
This trend is a predictable response to pricing
and may continue for some time given U.S.
Department of Energy forecasts of relatively
constant or even declining energy prices in the
short term (EIA, 1989).
The performance of other countries
suggests that higher energy prices are
conducive to greater efficiency. Japan, France,
and West Germany, much more dependent on
imported oil than the U.S., currently use much
less energy per unit of output than does the
United States (see Table 7-1). Many
developing countries are much less energy
efficient than the U.S., in part because they
subsidize energy prices.
In recent years, the U.S. has debated
and rejected higher oil import fees and
gasoline taxes as an instrument of energy
policy. The increase in the federal gasoline tax
recently enacted in the 1990 Budget
Reconciliation Act will produce increased
revenues to reduce the deficit and will also
assist in reducing greenhouse gas emissions by
encouraging greater efficiency in highway
transport.
Consumer concern about the "cost" of
some products may in fact focus on first
(initial) costs, or more simply, capital costs (as
opposed to operating costs, including
energy).3 Thus, the high-efficiency, long-life
light bulb may pay for itself in savings over its
useful life, but because the price is $12 most
TABLE 7-1
Energy Intensity of Selected National Economies, 1973-85
(megajoules per 1980 dollar of GNP)
Country
Percent
Change
1973 1979 1983 1985 1973-85
Australia
Canada
Greece*
Italy
Japan
Netherlands
Turkey
United Kingdom
United States
West Germany
21.6
38.3
17.1
18.5
18.9
19.8
28.4
19.8
35.6
17.1
23.0
38.8
18.5
17.1
16.7
18.9
24.2
18.0
32.9
16.2
22.1
36.5
18.9
15.3
13.5
15.8
25.7
15.8
28.8
14.0
20.3
36.0
19.8
14.9
13.1
16.2
25.2
15.8
27.5
14.0
-6
-6
+ 16
-19
-31
-18
-11
-20
-23
-18
* Energy intensity increased as a result of a move toward energy-intensive industries such as metal
processing.
Source: IEA, 1987.
VIMS
-------
Policy Options for Stabilizing Global Climate
people are reluctant to buy it. There are some
good reasons for this sensitivity to first costs,
such as limited access to capital, doubts about
performance claims, etc. These problems may
be addressed through the provision to the
consumer of accurate and useful information
about costs and performance, utility programs
to promote energy efficiency as an alternative
to expensive investment in new capacity, or
other incentive programs.
Another way of looking at costs is to
focus on the necessary increase in current
expenditures as a measure of the disruption
associated with certain policy proposals. Thus,
policies that require dramatic changes (or rates
of change) in current investment practices may
be characterized as "costly." For example, a
recent study compared the relative
effectiveness of energy conservation and
nuclear generation as strategies for reducing
CO2 emissions (Koomanoff, 1989). The
author found that to achieve a comparable
reduction in greenhouse gas emissions, nuclear
generation would have to increase at a rate
more than 40 times the rate at which plants
were completed during the peak decade 1975-
1985. In contrast, end-use efficiency would
have to increase 4.6% per year, a rate 60%
greater than the 2.9% annual rate at which
U.S. efficiency improved during 1978-1986 - a
challenging, but much less ambitious goal
measured as a change from historical practice.
Existing federal law gives an additional
economic incentive for efficiency through the
so-called "gas-guzzler" tax. For 1986 and later
models, the law imposes a $500 tax on any car
with a fuel economy rating less than 22.5 miles
per gallon (mpg) and a $3,850 tax on models
with ratings less than 12.5 mpg. It was
originally proposed that the revenues collected
be given to purchasers of highly efficient cars
in the form of a rebate; however, this proposal
was rejected because at the time the
beneficiaries would have been almost
exclusively buyers of imported cars (see
Bleviss, 1988).
Gas-guzzler fees could be used as a
potentially more effective and acceptable
substitute for gasoline taxes if set equal to the
amount that would be collected from a gas tax
over the expected lifetime of the automobile.
For example, a 50 cents per gallon tax would
become a 51,000 excise tax on a 25 mpg car
but only S333 on a 75 mpg car (assuming the
tax is calculated on the basis of driving 50,000
miles). An advantage of this strategy is that it
is less regressive than gasoline taxes because it
only applies to new vehicles and because it
gives consumers greater freedom to reduce or
avoid the tax by buying a more efficient model.
The structure of the charge could vary with
vehicle class so as not to unduly favor small
cars over larger models. The effectiveness of
such a system could be enhanced by rebating
some of the revenue to buyers of the most
efficient models, a concept that now may be
more acceptable since several American
models rate among the most efficient.
The market for electricity also
demonstrates the influence of prices and
competition on growth in demand. Until
about 1970, the efficiency of new powerplants
was improving and electricity prices were
therefore declining, contributing to steady
growth in the demand for electricity. From
about 1970 through 1982, electricity prices
rose mainly as a result of higher fuel costs and
interest rates, construction delays, the cost of
environmental controls, and the end to
significant improvements in generating
efficiency. In the last five years prices have
been stable or declining as fuel costs stabilized,
and the amount of new capacity being added
slowed in response to the decline in demand
(see Figure 7-4). The U.S. Department of
Energy projects continued stable prices until
the mid-1990s, followed by modest price
increases (EIA, 1989).
Financial Mechanisms to Promote Energy
Efficiency
Since the mid-1970s, the U.S. has
experimented with a variety of financial
incentives for energy efficiency. Most of these
programs have been carried out by state and
local governments and utility companies,
usually without much publicity but often quite
successfully.4 These efforts suggest that there
are possibilities for more widespread programs
in the future.
One of the most popular forms of
financial incentives offered by utilities is
rebates for high-efficiency appliances. A
recent survey revealed 59 such programs
VII-16
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Chapter VII: Policy Options
FIGURE 7-4
U.S. ELECTRICITY DEMAND AND PRICE
8
(1982 Cents/kwh; Annual Average Percentage Growth)
1960-1970
Demand
! 6
o
o
o
s
« u
c£
• s.
CO «
1960
1965
Source: U.S. DOE, 1988.
1970-1987
Demand
1970
1975
1980
Year
1987
VII-17
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Policy Options for Stabilizing Global Climate
amone U.S. utilities in all parts of the country
(Berrnan et a!., 1987; ACEEE, 1988). The
majority of these programs are only for
residential customers, but more than 20
programs also provide incentives to
commercial and industrial customers. Rebates
are structured in many different ways; most go
only to the purchaser, but some are also
offered to retailers. Program coverage varies
with differences in demand across the country;
some summer-peaking utilities promote both
high-efficiency air conditioners to reduce
summer demand and heat pumps to increase
demand in winter. Rebate amounts frequently
vary with the size and efficiency of the
appliance, sometimes according to a sliding
scale to encourage maximum efficiency. In
general, rebate programs appear to be highly
cost-effective relative to the costs of new
generating capacity. For 33 utilities reporting
such data, the median cost of peak demand
reduction was $200 per kilowatt (kW) saved.
(For an example of one unique utility
conservation program, see Box 7-1.)
Some programs demonstrate the
potential for giving economic incentives for
energy efficiency to builders. For example, the
Bonneville Power Administration's "Super
Good Cents" program gives builders a cash
grant of $1,000 per house for meeting Model
Conservation Standards developed by the
Northwest Power Planning Council (Randolph,
I988a).
Creating Markets for Conservation
The opportunity for highly profitable
investments in energy efficiency has not gone
unnoticed by some businesses. If consumers
are unresponsive to opportunities for
profitable investments in conservation,
businesses theoretically could make such
investments and share the savings, particularly
since a technically expert company could avoid
some of the uncertainties facing the typical
energy user. Such firms, often referred to as
energy service companies, did emerge in the
early 1980s. These firms offered a one-stop
shopping approach to conservation, combining
an energy audit to identify opportunities for
savings with installation and financing in
exchange for a share of the savings for some
fixed period. The owner is not required to
assume any risk and is guaranteed that his/her
Box 7-1.
The Hood River Experiment
One recent conservation program
illustrates the possibility of achieving
high levels of efficiency and broad
public participation. The Pacific Power
& Light Company and Bonneville
Power Administration financed what
was arguably the most aggressive
conservation program in the U.S. in the
small community of Hood River,
Oregon. The sponsors offered to audit
electrically-heated households and
implement all cost-effective
conservation measures. In two years,
85% of the eligible households
accepted improvements, and most of
the remainder of the populace received
an audit or had previously improved
their homes. Space heating levels were
reduced to about half the level expected
in pre-project forecasts. However, the
cost-effectiveness of the program
became difficult to evaluate when
electricity consumption dropped sharply
shortly before the program went into
effect due to price increases in excess of
40% (Cavanaugh and Hirst, 1987).
bill will be no higher than would have been
the case without the improvements. Federal
and state governments are testing shared-
saving programs to reduce capital spending
requirements (see STATE AND LOCAL
EFFORTS below).
In practice, the energy service concept
has proven to be valuable but not a panacea
(Weedall et al., 1986). The negotiation and
administration of contract terms can be
lengthy and expensive. Relatively large savings
are necessary to justify the overhead costs,
meaning that privately funded energy service
companies have generally been most interested
in larger projects, such as commercial
buildings. One means of expanding the reach
VII-18
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Chapter VII: Policy Options
of the energy service companies has been the
organization of such services by non-profit
groups, which can sometimes operate on a
lower margin because they do not pay taxes or
return a profit and may also be able to obtain
below-market-rate financing. On the other
hand, the range of permissible activities for
such organizations is usually limited by charter
and funding source. Recently, hybrids
containing elements of non-profit and for-
profit organizations have begun to appear,
with possibilities for achieving the benefits of
both (Kerwin and Jolin, 1988).
Another innovative approach to
reducing the cost of energy service contracting
is to pool enough buildings to achieve
economies of scale. The Alliance to Save
Energy developed a model for this concept
after a demonstration program with eight
agencies organized by the United Way of
Wilkes-Barre, Pennsylvania. However, the
project was difficult to implement, and the
potential for replication remains to be seen
(Prindle and Reid, 1988).
Many other financing mechanisms have
been tested or proposed (Lovins and Shepard,
1988). Several utilities offer generic rebates
for any demonstrated savings; in one area in
Manhattan with exceptionally high cost of
service, the utility offers commercial customers
rebates of $500 per kW peak reduction.
Another possibility is sliding-scale hookup fees
for new buildings, based on the cost of the
generating capacity necessary to supply the
building's electricity needs (the converse of
subsidies for more efficient buildings)
(Rosenfeld and Hafemeister, 1988; also see
Box 7-2).
Limits to Price-Oriented Policies
Box 7-2. Creating Markets Through
Demand Side Bidding
Another emerging approach to
promoting markets for efficiency is the
demand-side bidding concept. Bidding
programs for new capacity have been
developed in many states as a means of
obtaining low-cost supply additions, a
concept that may receive further
encouragement from proposed rules
now being considered by the Federal
Energy Regulatory Commission
(FERC, I988a). FERC has invited
comment on the possibility of
addressing demand-side bidding, and
several states have already implemented
such programs. Energy service
companies have some potential here
since they can achieve some economies
of scale. However, large commercial
and industrial firms may want to bid
themselves rather than share savings
(Cole et aL, 1988). In 1987 Central
Maine Power requested bids for
investments producing demand
reductions from large industrial
customers. The utility offered to pay
up to 50% of the project cost or a
rebate sufficient to reduce the payback
to two years, whichever is less; four
contracts were produced for a demand
reduction of over 11 MW at a cost of
$2.5 million.
Economic incentives could play a critical
role in reducing greenhouse gas emissions.
Nevertheless, there are often practical and
political limits to reliance on price-oriented
policies. Demand may be very inelastic due to
lack of information, the absence of alternatives
in the near term, or shortages of capital. Price
increases may also have socially undesirable,
disproportionate impacts on particular groups
or regions. Price increases may also be
politically unpopular relative to other policies.
Thus, the price necessary to induce change
might be so high as to be inequitable,
economically impractical, and politically
unattractive. Empirical studies illustrate some
situations in which increased energy prices
have not resulted in nearly the degree of
energy efficiency that would be expected from
economic calculations. One study at the
Energy Analysis Program at the Lawrence
Berkeley Laboratory examined the market for
more energy-efficient appliances over the
vn-19
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Policy Options for Stabilizing Global Climate
period 1972-1980 (Ruderman et al., 1987).
The authors found that consumers demand
payback periods of two years or less for
investing in more efficient household
appliances. Except for air conditioners, the
implicit discount rates corresponding to these
payback periods are much higher than real
interest rates or the discount rates commonly
used in life-cycle cost analysis of consumer
choice (see Table 7-2). The study suggests
several factors are responsible for this
substantial underinvestment in energy
efficiency: lack of information, lack of access
to capital to pay for the added first cost, the
relatively small savings, a substantial number
of purchases of some appliances by builders or
landlords who do not pay operating costs, and
manufacturers' decisions to limit high-
efficiency features to top-of-the-line models
that yield higher profit margins.
Studies of small commercial customers
and larger industrial customers indicate they
also make greater demands of efficiency
investments than of alternatives that are
considered to be more within their main line
of business (Komor and Katzev, 1988; Lovins
and Shepard, 1988; Cavanaugh, 1988; Alliance
to Save Energy, 1987). Managers of small
enterprises may never see the electric and gas
bill, have no knowledge of the rate structure
for their building, and are largely unaware of
which appliances are responsible for most of
their bills. Larger companies may demand
payback periods of six months to two years for
conservation investments, while simultaneously
investing in government bonds at an 11%
interest rate. Utility companies typically apply
investment criteria to new powerplants that
are much less demanding than consumer
investments to save an equivalent amount of
energy (Cavanaugh, 1986).
Some authorities predict that market
forces alone are unlikely to prompt continued
demand for automobile efficiency
improvements because of the declining share
of operating costs attributable to fuel as
efficiency improves (see Figure 7-5). According
to an analysis by the U.S. Department of
Energy, a typical automobile costs over
510,000 and consumes about 370 gallons of
gasoline per year (U.S. DOE, 1988; see also
Bleviss, 1988; Goldemberg et al., 1987). At
Si.10 per gallon, this implies that annual fuel
expenses typically represent only about 4% of
the purchase cost and much less than
insurance, maintenance, and financing
expenses. The result, according to the U.S.
DOE, is that "the desire to reduce fuel
expenses, even with higher gasoline prices, will
not motivate consumers to significantly alter
their preferences for automobiles" (U.S. DOE,
1988).5 Precise evaluation of this effect is
TABLE 7-2
Years Required to Pay Back Investment
in Energy-Efficient Appliances, 1972-1980
Appliance
1972
Source: Ruderman et al., 1987.
1978
1980
Gas central space heater
Oil central space heater
Room air conditioner
Central air conditioner
Electric water heater
Gas water heater
Refrigerator
Freezer
2.98
2.33
5.11
4.96
0.48
1.50
1.35
0.60
2.38
1.70
4.77
4.16
0.41
1.07
1.45
0.67
2.21
1.18
5.25
5.18
0.41
0.98
1.69
0.72
VII-20
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Chapter VII: Policy Options
FIGURE 7-5
COST OF DRIVING VERSUS AUTOMOTIVE FUEL ECONOMY
£2 cS
-ci
-5- c
. I 1
4- H§
= S * i .3 £
-
i i i
r
Miles Per Gallon (United States)
50
£
2
10-1
Base Vehicle Purchase Price ($7,000)
Vehicle Fees and Taxes _
Incremental Price •
for Improvements
Insurance
Garaging, Parking, and Tolls
Repairs, Parts, and Maintenance
-10
20
10 7.5 6 5 4
Liters Per 100 Kilometers
3.5
2.7
Figure 7-5. The indicated energy performance is based on computer simulations of an automobile
having various fuel economy improvements added in the sequence shown at the top of the graph. The
base car is a 1981 Volkswagen Rabbit (gas version). The figure shows that the reduced operating
costs associated with various fuel economy improvements are roughly offset by the increased capital
costs of these improvements over a wide range of fuel economy.
Source: Goldemberg et al., 1987.
VH-21
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Policy Options for Stabilizing Global Climate
difficult; the high visibility of posted gasoline
prices may cause some consumers to focus
more attention on this cost than on other
operating costs. Moreover, at some higher
price, consumers could be induced to change
their preferences, but this price might be so
high as to be inequitable, impractical, or
politically unacceptable.6
Economic incentives alone may not
serve to reduce trace-gas emissions to
acceptable levels. When markets are
unresponsive, there may be a need for
regulations or other policies to help restrict
activities that result in emissions of trace
gases. One desirable effect of regulations and
other alternatives to direct economic
incentives may be to increase the costs of
regulated products and activities, thereby
creating indirect economic incentives.
REGULATIONS AND STANDARDS
Regulation of energy, CFCs, and
forestry could complement pricing and other
policies for reducing greenhouse gas emissions.
In brief, pricing strategies and other
government policies may not always induce
changes in consumer behavior effectively,
either because there is some major market
failure or because of an unwillingness to set
prices high enough to bring about the desired
change in demand.
Like pricing and economic incentive
policies, government regulations should be
viewed as simply one tool for promoting the
development and adoption of technologies and
behavioral changes necessary to reduce
greenhouse gas emissions. They are likely to
be most effective (and perhaps most
acceptable) when they are targeted to specific
groups, are no more restrictive than necessary,
and are used to complement economic
incentives, research and development
programs, information programs, and the other
approaches outlined in this chapter.
In this section we will discuss possible
regulatory strategies for strengthening existing
regulatory programs (which have been adopted
for reasons unrelated to climate change) to
either restrict emissions of greenhouse gases
or encourage actions to reduce emissions, as
well as concepts for new regulatory programs
specifically targeted to reduce emissions.
Existing Regulations that Restrict
Greenhouse Gas Emissions
The U.S. federal government already has
extensive regulations and regulatory programs
that limit greenhouse gas emissions, such as its
air pollution control laws, restrictions on the
use of CFCs, and regulation of investments
and rates charged by utilities. There are also
energy-efficiency standards for automobiles,
appliances, and fluorescent lamp ballasts. All
of these programs could be modified to yield
further reductions in greenhouse gas
emissions.
Regulation of Chlorofluorocarbons
Chlorofluorocarbons are being regulated
because of concern about their impact on
stratospheric ozone (see discussion in
CHAPTERS IV and V). The potential for
introducing substitutes for CFCs to reduce the
risks of ozone depletion and global warming
has been known for many years. For example,
the DuPont Company stated in 1980 that such
substitutes could be produced, but the cost
would be much higher (E.I. DuPont, Inc.,
1980). Without regulation, however, there was
no market for these alternative chemicals so
they were not produced. The Montreal
Protocol on Substances That Deplete the
Ozone Layer, signed in September 1987,
provides a framework for global reductions in
CFC emissions. The subsequent June 1990
London Amendments to the Protocol provide
an accelerated framework for global reductions
of CFCs and halons, and introduce a schedule
for global reductions in methyl chloroform and
carbon tetrachloride:
• The use of CFCs-11, -12, -113, -114
and -115 is to be frozen at 1986 levels starting
in approximately mid-1989, reduced to 80% of
1986 levels in 1993, and reduced to 50% of
1986 levels in 1995. The reduction from 80%
to 50% will take place unless the parties
participating in the Protocol vote otherwise.
• The use of halons 1211, 1301, and
2402 is to be frozen at 1986 levels starting in
approximately 1992, reduced to 50% of the
1986 levels in 1995, and phased out by 2000.
VII-22
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Chapter VII: Policy Options
• The use of methyl chloroform is to
be frozen at 1989 levels starting in 1993, and
reduced to 70% of 1989 levels by 1995, and
reduced to 30% of 1989 levels by 2000, with
full phase out in 2005.
• The use of carbon tetrachloride is to
be frozen at 1989 levels in 1992, reduced to
15% of 1989 levels in 1995, and completely
phased out in 2000.
• The London Amendments also
include a non-binding resolution regarding
phase out of HCFCs.
• Beginning in 1990, and at least every
four years thereafter, the parties will assess the
control measures in light of the current data
available. Based on these assessments the
parties may adjust the control levels and
substances covered by the Protocol.
• Each party shall ban the import of
the controlled substances (bulk CFCs and
halons) from any State not party to the
Protocol beginning one year after the Protocol
takes effect. The parties shall, in addition,
develop a list of products that contain the
controlled substances, which will be subject to
the same trade restrictions. The feasibility of
restricting trade in products manufactured with
the controlled substances shall also be
assessed.
• Developing countries with low levels
of use per capita are permitted to delay their
compliance with the Protocol for up to ten
years. The parties also agree to assist
developing countries to make expeditious use
of environmentally safe alternative substances
and technologies.
The U.S. Clean Air Act Amendments
provide a more detailed reduction schedule for
CFCs and halons, accelerate the reduction
schedule for methyl chloroform (freeze at 1989
levels starting in 1991 with full phase out in
2002), and for carbon tetrachloride (freeze at
1989 levels starting in 1991 with full phase out
in 2000), as well as a phase-out of HCFCs
over the 2015 to 2030 period.
On August 1, 1988, U.S. EPA
announced a comprehensive regulatory
program for these chemicals that will reduce
production and consumption in three phases
leading to a 50% cut by July 1, 1998 (Federal
Register, 1988). The U.S. regulations become
effective upon international ratification of the
Protocol. In September 1988, U.S. EPA
Administrator Lee Thomas stated that recent
scientific evidence makes it necessary to
consider a complete phase-out of these
chemicals. The regulatory approach adopted
by U.S. EPA restricts CFCs by granting limited
production rights to the five U.S. companies
who manufactured them in 1986, and by
restricting imports. This is expected to cause
an increase in price and an increasing
incentive for CFC users to find substitutes.
U.S. EPA was concerned that the added
profits for CFC producers could create an
incentive to delay the introduction of
substitute chemicals. U.S. EPA estimated that
CFC producers could earn additional profits
between SI.8 billion and S7.2 billion by the
year 2000. The Agency therefore requested
comments on the merit and legality of taxes on
CFCs to remove the added profit and potential
incentive to delay.
Another concern is that the price rise
alone may not be an effective means of
reducing demand for some uses of CFCs for
which substitutes may be available, but which
have a small impact on total product cost.
U.S. EPA has indicated it will monitor this
possibility and will, if necessary, consider
product-specific regulations.
Energy Efficiency Standards
Congress adopted minimum energy
efficiency standards in 1987 for refrigerators,
water heaters, air conditioners, furnaces, and
other appliances. The standards take effect on
different dates for different products in
recognition of variations in product planning
and production needs. The law defines
standards for different classes and categories of
each appliance and does not prevent the
addition of new features that may increase
total energy consumption (see Table 7-3). By
one estimate, the standards will reduce peak
electricity demand in the year 2000 by an
amount equivalent to the output of 22 large
powerplants (Geller, 1986a). The appliance
standards were adopted on the basis of a
consensus supported by industry and
VII-23
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Policy Options for Stabilizing Global Climate
TABLE 7-3
Comparison of Energy Efficiencies of Regulated Appliances
Average Annual Enerev Consumption
Appliance In-Use Models
Refrigerator0
Central Air Conditioner0
Electric Water Heater0
Electric Range0
Gas Furnaced
Gas Water Heaterd
Gas Ranged
1,500
3,600
4,000
800
730
270
70
New Models
1,100
2,900
3,500
750
620
250
50
Best Estimated
Commercial Cost-Effective
Model Potential3
750
1,800
1,600
700
480
200
40
200-400
900-1,200
1,000-1,500
400-500
300-480
100-150
25-30
Potential
Savings6
(percent)
87
75
75
50
59
63
64
a Estimates are made of potential efficiency (by mid-1990s) if further cost-effective improvements
already under study.
b Percent reduction in energy consumption from the average of those appliances in use to the best
cost-effective potential.
0 Energy consumption for these appliances measured in kilowatt-hours per year.
d Energy consumption for these appliances measured in therms per year.
Source: Geller, 1986b.
VII-24
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Chapter VII: Policy Options
environmental and consumer groups,
demonstrating that a cooperative approach to
establish achievable energy efficiency goals is
possible. Appliance manufacturers were most
interested in preemption of state regulation,
while utilities and environmental groups were
motivated by energy savings. On November
17, 1989, the Department of Energy published
regulations imposing new efficiency standards
for refrigerators and freezers. The new
standards are more stringent than minimums
established by the federal law and by
California and are expected to reduce energy
use by 25%.
The energy efficiency standard for new
U.S. automobiles as of 1988 was a CAFE of 26
mpg. In September 1988, the Department of
Transportation set CAFE standards at 26.5
mpg for the 1989 model year, down from a
scheduled increase to 27.5 mpg. The standard
for the 1990 model year has been set at 27.5
mpg. Automakers are allowed to meet this
requirement by offsetting less efficient (usually
larger, more powerful) models with more
efficient ones; they may also offset their failure
to meet the target in one year with credits
gained in prior years. However, mpg ratings
of domestic models may not be averaged with
those of foreign imports. New-car fuel
economy has improved markedly since CAFE
was adopted (well over 50% since 1973), but
its value has been vigorously debated. The
research of Greene (1989) indicates that
CAFE standards have had about twice the
influence of gasoline prices on efficiency
improvements. Critics of the efficiency
standards, however, argue that the fuel-
economy gains have been primarily a response
to higher prices and that the regulations have
imposed substantial costs on manufacturers
and consumers. They argue that fuel efficiency
is improving due to market pressures and
technological innovation, but that if more
rapid improvement is desired, it could be
promoted more efficiently by higher gasoline
taxes to promote demand for more efficient
vehicles and encourage turnover of older,
inefficient cars (U.S. DOE, 1988; Crandall et
al., 1986). Another problem with efficiency
standards is that they may have contributed to
the trend toward longer use of older vehicles.
Only 12% of vehicles in use in 1969 were
more than ten years old,' but this figure
increased to 29% in 1987, substantially
increasing both fuel consumption and air
pollution from what it would otherwise have
been.
There is, however, no assurance that
market forces alone will produce substantial
further improvement in vehicle mileage ratings
as long as oil prices are stable or declining in
real terms. Higher gasoline taxes would help
but may have to be increased sharply to spur
demand for efficiency improvements beyond 30
mpg. Exclusively demand-oriented strategies
can leave manufacturers with considerable
uncertainty about future markets (Bleviss,
1988). Regulations adopted as a supplement
to tax increases could give industry a clear
target, reducing the need for hedging strategies
that dilute efforts and increase investment
costs (Bleviss, 1988).
The CAFE approach also could be
improved to increase incentives for efficiency
improvements and to meet some industry
objections (McNutt and Patterson, 1986). The
fleet average concept unduly penalizes larger
cars, when technologies could allow
improvements in all sizes and classes. It
requires annual improvements, when
improvements are made in steps over longer
time periods, and then seeks to provide
flexibility with credits that encourage a search
for administrative exemption rather than long-
term improvement. Lower standards have
been set for light trucks, which further
undercut the program. Finally, violations of
standards are punishable by court-imposed
civil penalties, when equivalent economic
incentives could achieve the same results more
acceptably by imposing fees proportional to
the noncompliance (Bleviss, 1988).
Air Pollution Regulations
Some greenhouse gases are already
regulated as air pollutants because of their
effects on human health and welfare. Under
the Clean Air Act, U.S. EPA sets uniform
ambient standards for emissions of carbon
monoxide (CO), ozone (O3), nitrogen oxides
(NOX), and other pollutants and uniform
technology-based standards for major new
sources of these pollutants. However, states
retain responsibility for compliance with the
ambient standards, which may require
allocating greater responsibility on some
YII-25
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Policy Options for Stabilizing Global Climate
sources than on others. States are also free to
set more stringent requirements on stationary
sources.
The regulatory strategy for control of air
pollutants to stabilize greenhouse gas
concentrations is not identical to that for
achieving compliance with ambient air quality
standards. In the latter case, the objective is
to stay below threshold levels that affect
human health or welfare. Total as well as
peak emissions, however, affect the buildup of
greenhouse gases, which implies a potentially
different regulatory approach. An area barely
in compliance with ambient air quality
standards at all times may contribute more to
greenhouse gas buildup than an area with
occasional air quality violations but extensive
periods of much cleaner air.
Substantial progress has been made in
reducing total emissions of regulated
pollutants since the Clean Air Act was
adopted in 1970 (U.S. EPA, 1987). For
example, CO emissions from automobiles
dropped about 35% from 1970 to 1985 despite
a 58% increase in vehicle miles traveled (see
Figure 7-6). Emissions of volatile organic
compounds from highway vehicles decreased
48% in the same period. However, emissions
of NOX during this period were relatively
unchanged.
Passage of the Clean Air Act
Amendments of 1990 will result in
substantially increased progress toward cleaner
air from a health and welfare viewpoint. In
addition, it will have substantial greenhouse
gas reduction effects. The efforts to achieve
attainment and maintenance of National
Ambient Air Quality Standards through
regulation of carbon monoxide, nitrogen
oxides, and volatile organic compounds will
reduce tropospheric ozone and methane.
Specific targets for sulfur dioxide of 10 million
tons below 1980 levels and for nitrogen oxides
of 2 million tons below projected year 2000
levels will encourage energy efficiency and
reduce greenhouse gas emissions. The
provisions of the Clean Air Act and the
Montreal Protocol to phase out CFCs, halons,
and carbon tetrachloride by 2000, methyl
chloroform by 2002, and HCFCs over the 2015
to 2030 period will directly reduce greenhouse
gas emissions as well as protect the
stratospheric ozone layer.
Solid Waste Management
The problem of solid waste management
illustrates another area in which policies to
reduce greenhouse gas emissions may
complement other environmental objectives.
As discussed in Chapter IV, decomposition of
solid wastes is a growing source of methane
emissions. In the U.S., governments at all
levels have accelerated efforts to promote
recycling and reduction of solid wastes for
both economic and environmental reasons.
Slate and local governments have
historically been primarily responsible for solid
waste disposal. The cost of landfills and
public opposition to burning waste has
generated substantial interest in recycling and
waste reduction. Numerous states have
recently adopted stringent programs to reduce
the waste stream by a minimum of 25%. How
this will be accomplished has yet to be made
completely clear, but economic incentives will
play a major role in some states. Florida
adopted an advance disposal fee on every retail
container sold that fails to achieve a 50%
recycling rate; the fee increases if targets are
not met (Carlson, E., 1988). Similarly,
California adopted a system of deposit fees
with increases scheduled to take effect if goals
are not met.
Federal law (RCRA Sec. 4Q10(c))
assigns U.S. EPA the responsibility for
ensuring the environmental safety of sanitary
landfills. As discussed in Chapter V, U.S.
EPA proposed minimum standards on August
1, 1988, that would require gas monitoring
stations to detect methane and to plan for its
removal, and proposed regulations under the
Clean Air Act that would require collection of
landfill gas at both new and existing landfills.
The Agency has also supported a national
recycling goal of 25% by 1992.
Another source of methane releases
discussed in Chapter V is coal mining. Interest
in coalbed methane recovery is increasing for
economic reasons, but at this time there are
no specific policies to promote such efforts.
VII-26
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Chapter VII: policy Options
FIGURE 7-6
80
U. S. CARBON MONOXIDE EMISSIONS
(Million Metric Tons)
Miscellaneous
Solid Waste
Industrial
Processes
Fuel
Combustion
Transportation
1986
Source: U.S. EPA, 1988.
VII-27
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Policy Options for Stabilizing Global Climate
Utility Regulation
Regulatory policies also can exert a
significant influence on the price and demand
for electricity. Electric companies are
monopolies whose rates and investments are
regulated by state public utility commissions --
except for wholesale and interstate
transactions, which are approved by the
Federal Energy Regulatory Commission. The
structure, as well as the overall level of
electricity rates, is regulated, and both
influence demand (see Kahn, 1988). For
example, some states provide relatively low
"lifeline" rates for the initial increment of
residential demand to meet the basic energy
needs of all customers. The consequence is
usually an inverted block rate structure, with
rates increasing with greater use. Even though
rates may be initially set to produce the same
total revenue, the result is some reduction in
demand because consumers recognize the
higher rates associated with greater use. For
example, Detroit Edison estimated that a
lifeline rate structure imposed in 1981 resulted
in reducing demand about 3% (Kahn, 1988).
Where the production of electricity to
meet peak power needs is more carbon-
intensive (e.g., where the marginal fuel is oil
and the base fuel has a large percentage of
nuclear power), incentives to reduce peak
demand and to level loads may be
economically justified as a means of
supporting greenhouse gas reductions. With
time-of-use metering, utilities can charge rates
that more accurately reflect costs, potentially
promoting energy efficiency as well as cost
savings. This is possible because the costs of
generating electricity are not uniform
throughout the year; when demand peaks,
costs are usually highest because the utility
must rely on its most costly units to meet the
increased demand. Some utilities in the U.S.
and in Europe have tested rate structures that
give customers incentives to use electricity at
times when costs are low, and conversely,
disincentives when costs are high. For
example, a recent three-year New York
experiment gave customers a one-cent-per-
kWh reduction during hours of normal
demand, but above a certain threshold level,
customers were charged a rate of 40 cents per
kWh, several times higher than the usual rate.
On average, customers saved 5 to 10%
annually, reduced their peak period loads over
40% relative to the average customer, and
expressed strong support for the continuation
of the program (Cole and Rizutto, 1988). The
metering costs are currently about S500 per
house, but the overall program is still expected
to produce substantial net benefits. Moreover,
it is expected that meter costs will drop
substantially with large production. (For an
example of utility disincentives, see Box 7-3.)
Box 7-3. Disincentives to
Utility Conservation
The revenues earned by electric
and gas utilities are governed by
accounting rules devised to allow
utilities to recover operating costs and
earn a fair rate of return. These rules
were not intended to favor particular
types of investments but recent analysis
by the Maine and California public
utility commissions indicates that they
may in fact favor investments in
additional supply as opposed to
efficiency improvements, even when the
latter is much less expensive
(Moskovitz, 1988; Cavanaugh, 1988).
As long as retail rates exceed short-
term production costs, these studies
show that, under traditional regulatory
practices, utilities will always earn
greater profits by selling more
electricity, even if the cost of
conservation is zero. Allowing utilities
to profit from conservation by allowing
an equivalent return on such
investments does not rectify the
situation. Instead, the economic
incentive is to do the most costly
conservation investments (to achieve
the greatest return) with the least
impact (to maintain sales). California
and Maine have adopted procedures
designed to correct these disincentives
as one means of encouraging utility
interest in demand-side investments.
VII-28
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Chapter VII: Policy Options
Another significant issue in utility
regulation is the creation of competitive
markets for the generation of electricity.
Federal and state policy have encouraged this
concept since the enactment of the Public
Utility Regulatory Policies Act (PURPA) in
1978. This law requires utilities to buy power
from cogenerators and small renewable energy
projects and to pay an amount equal to the
costs they save as a result. Since the law's
adoption, thousands of projects have been
developed around the country, despite the
absence of a need for new generating capacity
in many areas (FERC, 1988c).7 FERC
compilations indicate cumulative applications
from projects equivalent to more than 40
nuclear powerplants (see Table 7-4). In
addition, FERC is currently reviewing
proposed rules to expand the circumstances
and type of projects eligible to participate in
competitive bidding arrangements (FERC,
1988a, 1988b). FERC has also asked for
comment on the possibility of allowing
demand-side reduction efforts to compete with
capacity additions.
Existing Regulations that Encourage
Emissions Reductions
In contrast with the mandatory
regulations discussed above, some regulatory
programs stress positive incentives for
activities to reduce greenhouse gas
concentrations. Such programs could be
expanded to encourage greenhouse gas
reductions.
Tree Planting
A prime example of regulatory
incentives for actions that reduce greenhouse
gas concentrations is the Conservation Reserve
Program (CRP) created by the Food Security
Act of 1985. The CRP gives up to 50% of the
cost of establishing approved conservation
practices to farmers who agree to take highly
erodible cropland out of production for
contracted periods of 10-15 years. Under
Section 1232(c), at least one-eighth of the
number of acres placed in the reserve between
1986 and 1990 are to be devoted to trees. As
of the sixth signup, ending February 19, 1988,
more than 1.5 million acres had been
committed to trees -- less than a third of the
Congressional goal — at a cost to the
government of roughly S58 million (Dudek.
1988).
In recognition of the CRP's broader
potential for achieving environmental
protection, the program was modified in the
sixth signup to allow the inclusion of 66- to
99-foot-wide strips of former cropland along
streams and waterbodies, irrespective of the
erosion rate.8 Tree planting is one allowed
use of the land. These so-called "filter strips"
provide a buffer zone that absorbs pollutants
that would otherwise go into lakes and
streams. The Conservation Reserve Program
offers a possible model and precedent for
further cooperation between U.S. EPA and the
U.S. Forest Service to identify opportunities
where tree planting may serve multiple-agency
goals.
Because the CRP provides such diverse
benefits, proposals have been made to expand
its scope and coverage. In some states,
particularly in the Southeast, aggressive tree
planting could become a significant means of
offsetting the buildup of carbon dioxide.
According to a recent study, most eastern
states, with the exception of Florida, appear to
have enough erodible acreage to provide the
acres needed to offset new CO2 emissions
from electricity production if such acreage is
planted with trees (see Table 7-5). Roughly
11-22 million acres of new trees, or about one-
fourth to one-half of the current CRP goal,
would offset projected new fossil-fueled
generating plants for the 1987-1996 period,
assuming those 11-22 million acres were
planted with optimum species (Dudek, 1988).
By this estimate, the costs are modest relative
to other environmental requirements
associated with operating powerplants, on the
order of 0.5 cents per kilowatt-hour.
New strategies to promote tree planting
may avoid some of the limitations and
complications created by the CRP, which must
identify farmers willing to withdraw farmland
and which must restrict the land for a period
less than the time many trees require to reach
maturity. Utility companies and large
industrial coal users may also wish to sponsor
tree planting. The U.S. Forest Service reports
that southeastern states - where most timber
industry investments have occurred in the past
two decades - must replant and manage their
VII-29
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Policy Options for Stabilizing Global Climate
TABLE 7-4
Cogeneration Facilities
(No. Filings), [No. of Facilities), and Capacity in kW
Total Cogeneration
New
Existing
Both
Total
Qualified Facilities
and
Initial Capacity
Coal
Natural Gas
Biomass
Waste
Oil
Other
( 183)
(1,264)
( 122)
( 51)
( 47)
( 38)
10,419,659
25,894,776
1,617,390
2,432,239
324,921
1,258,288
(6)
(41)
(18)
(2)
(8)
(3)
461,600
1,888,457
570,497
40,875
323,700
56,500
(12)
(9)
(9)
(1)
(1)
(1)
356,272
694.67J
615,000
51,000
5,350
62,250
( 201)
(1,314)
( 149)
( 54)
( 56)
( 42)
11,237,531
28,477,904
2,802,887
2,524,114
653,971
1,377,038
( 178]
(1,269]
( 1381
[ 50]
[ 56]
f 39]
10,948,083
26,880,678
2,698,802
2,450,114
653,971
1,311,968
(1,705) 41,947,273
(78) 3,341,629
(33) 1,784,543
(1,816) 47,073,445
[1,730]
44,943,616
NOTES:
1. Under §292.202 of the Commission's rules, "Cogeneration facility means equipment used to produce electric energy and forms of useful thermal energy (such ;is
heat or steam) used for industrial, commercial, heating, or cooling purposes, through the sequential use of energy." Topping-cycle facilities first apply the energy
input to electric power production; bottoming-cycle facilities first apply the energy input to a useful thermal application. All but nine filings in this table are
topping-cycle facilities. Bottoming-cycle and partially bottoming-cycle facilities are listed below, along with their capacities:
QF80
QF82
QF82
QF83-
QF84-
QF84
QF85
QF86
QF86
6-000 New
100-000 New
207-000 New
220-000 New
134-000 New
192-000 Ex.
•572-000 New
23-000 New
800-000 New
Petro Coke 75,000
Coal 10,000
Coal/Waste 125,000
NG, FO 6,000
Petro Coke 27,300
NG 910
Waste/Petro Coke 49,900
NG 2,700
Hydrocarbon Coke 3,300
2. "Other" includes Cogeneration facilities using nuclear or solar energy sources.
Source: FERC, 1988c; Koomanoff, 1989.
VII-30
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Chapter VII: Policy Options
TABLE 7-5
Erodible Acreage Available to Offset CO2 Emissions
From Electricity Production
Megawatts
State
Alabama
Arizona
Colorado
Florida
Georgia
Iowa
Indiana
Kentucky
Louisiana
Maryland
Minnesota
Missouri
Mississippi
North Carolina
Nevada
Ohio
Oklahoma
Texas
Utah
Wisconsin
Total
(MW)
1,557
710
899
2,678
1,641
50
1,600
1,095
540
753
1,251
1,005
250
690
1,865
1,300
470
5,515
814
60
24,743
CO2 Emission
(103 tons)
10,458.4
4,900.3
6,204.7
15,136.3
11,325.9
201.2
10,179.6
7,557.5
3,727.0
4,870.3
8,634.2
6,792.4
1,725.5
4,762.3
12,469.0
8,972.4
2,754.6
38,063.5
5,577.8
414.1
164,727
Erodible Acres
(103 acres)
2,558.8
187.1
6,480.1
670.2
3,072.7
17,833.7
5,244.2
2,412.7
2,171.0
602.7
10,102.0
7,223.7
3,009.9
2,476.4
79.1
3,799.8
3,795.2
20,417.2
392.6
4,015.6
96,544.7
Offset
(103
697.2
326.7
413.6
1,009.1
755.1
13.4
678.6
503.8
248.5
324.7
575.6
452.8
115.0
317.5
831.3
598.2
183.6
2,537.6
371.9
27.6
10,981.8
Average
acres)
- 2,091.6
- 980.1
- 1,240.8
- 3,027.3
- 2,265.3
40.2
- 2,035.8
- 1,511.4
- 745.5
- 974.1
- 1,726.8
- 1,358.4
- 345.0
- 952.5
- 2,493.9
- 1,794.6
- 550.8
- 7,612.8
- 1,115.7
82.8
-32,945.4
Percent
27.2
6.4
24.6
0.1
12.9
20.9
11.4
53.9
5.7
6.3
3.8
12.8
15.7
4.8
12.4
94.7
0.7
11.4
(%)
- 81.7
> 100
- 19.2
> 100
- 73.8
- 0.3
- 38.7
- 62.7
- 34.2
-> 100
- 17.1
- 18.9
- 11.4
- 38.4
> 100
- 47.1
- 14.4
- 37.2
-> 100
- 2.1
- 34.2
Source: Dudek, 1988.
VII-31
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Policy Options for Stabilizing Global Climate
dwindling forests to allow their timber industry
to keep growing (USFS, 1987).
There are some practical questions to be
answered before attempting a large-scale
program to offset carbon emissions with tree
planting, particularly if implemented on an
international basis. For example, there may be
difficulty counting net "new" trees in a
developing country undergoing deforestation;
there must be assurances that the trees are
properly cared for and not cut down
prematurely. Similarly, counting net energy
reductions may be difficult since a factory may
have intended to make improvements in any
case.
Despite these concerns, the offset
concept offers some advantages that make it
worthy of further consideration. First, it can
be targeted to achieve greenhouse gas
reductions, unlike energy regulations, which
may not always reduce carbon-intensive fossil
fuels. Second, the offset concept is consistent
with efficiency and innovation by allowing each
developer the flexibility to seek out the least
expensive means of reducing his emissions.
Third, it can be implemented in a way that
promotes international cooperation by
allowing reductions to be achieved in
developing countries where they can be
accomplished most cheaply and also contribute
to development. Eligibility for offsets could be
limited to countries that join in an
international greenhouse agreement as an
incentive for participation.
Other Incentives I Disincentives
The Food and Security Act has another
provision that demonstrates the potential use
of regulations to promote environmental goals.
Under Section 1221, any farmer who produces
an agricultural commodity on a wetland
converted to agricultural use after the effective
date of the Act may become ineligible for
many forms of U.S. Department of Agriculture
financial assistance. The restriction applies to
all of the farmer's land, not only the converted
wetland area. The impact of the program
obviously depends on the value of the financial
assistance, which in turn varies with
commodity prices, but the precedent is
important (see Tripp and Dudek, 1986).
Another example of regulatory
incentives for actions to reduce greenhouse gas
emissions is higher rates of return in some
states for utility investments in energy
efficiency or renewable energy. Utilities are
also sometimes allowed to choose whether to
amortize their investment and receive a return
or recover their expenses in the first year.
Some states have also adopted revenue
adjustment provisions to prevent reductions
in utility profits as a consequence of utility-
sponsored conservation programs (Cavanaugh,
1988; Moskovitz, 1988).
RESEARCH AND DEVELOPMENT
Further research and development will
be necessary to bring about widespread use of
many of the technologies and strategies
reviewed in Chapter V. As discussed below, in
some areas substantial programs are already in
place, while in others existing priorities may
not be entirely consistent with the objective of
stabilizing greenhouse gas emissions.
Research programs can serve several
different purposes. In some cases, such as
finding more efficient methods for producing
steel and photovoltaics, basic research is
needed. In other areas, technologies are
nearly commercially ready but their
introduction could be accelerated through
testing and demonstration (see Box 7-4).
Research is important to improve policies and
programs as well as hardware; for example, the
U.S. has acquired considerable experience with
energy conservation programs over the last
decade that has yet to be fully evaluated and
summarized for use by public and private
authorities.9
The importance of government support
for R&D is widely accepted; industry often has
only a weak incentive to pay for research that
will be of widespread benefit or that is long
term and high risk (U.S. DOE, 1987c).
However, government can create incentives for
greater industry efforts. Special efforts are
also needed to develop technologies suitable
for use in developing countries where local
needs and resources may dictate very different
solutions.
VII-32
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Chapter VII: Policy Options
Box 7-4. Light-Vehicle Fuel Economy R&D
Prototype vehicles designed by Toyota and Volvo have already demonstrated that it is
technically possible to produce full-sized vehicles with fuel economy of 70 mpg or better, as
discussed in Chapter V. Recent developments in materials technology and other areas suggest
that even this level will be greatly exceeded in the near future. The problem therefore is less
one of basic science than it is lack of incentives for product development to reduce costs. The
relatively low price of oil has diminished incentives to invest in improved efficiency unless it
is associated with other features considered more marketable. This is true in both Japan and
Western Europe, as well as in the U.S., since the price of oil has declined even more rapidly
in these countries because of the relative decline in the value of the dollar.
Barring another large rise in oil prices or some significant government policy intervention,
it seems unlikely to expect that consumers will demand, and that manufacturers will produce,
vehicles with much higher fuel economy. Indeed, there is some evidence that fuel economy
(particularly in U.S.-made vehicles) will stagnate or even decline in the near term as a result
of market demand for larger models and increased acceleration and performance capabilities
(Bleviss, 1988).
Energy Research and Development
The energy R&D budget is important
from a greenhouse perspective in both its total
amount and its relative priorities. Research to
promote the more efficient use of all forms of
energy is desirable from the standpoint of
greenhouse gas emissions, as is research to
reduce the cost of renewable and nuclear
energy relative to fossil fuels. Since fiscal year
(FY) 1981, annual appropriations for energy
R&D have declined from $3.4 billion to
roughly $1.4 billion in FY 1988. An
examination of R&D expenditures in other
western industrialized countries suggests that
their research budgets have tended to remain
more constant than those of the U.S. As of
1986, the U.S. ranked last among the
Organization for Economic Cooperation and
Development (OECD) member countries in
the percentage of GNP devoted to energy-
efficiency R&D. However, U.S. expenditures
still ranked first in absolute terms (see Table
7-6).
Priorities among energy sources have
also shifted during the 1980s as research on
renewables and conservation has declined
more than research in other areas (see Figure
7-7). The Clean Coal Program is by far the
largest energy R&D initiative this decade;
President Reagan requested $525 million for
FY 1989 and $1.775 billion for FY 1990-1992.
Clean coal technologies could make an
important contribution to reducing CO2
emissions by substantially improving the
efficiency of coal use so that less coal needs to
be used to produce a given amount of
electricity. Electricity generation is the only
major area of primary energy use that has not
achieved significant efficiency improvements in
the last 25 years (Fulkerson et al., 1989).
However, the intent of current policy is also to
expand the market for coal here and abroad,
thereby helping to improve the U.S. balance of
trade (coal exports were worth $3.5 billion in
1987). Unfortunately, expanded coal use would
unavoidably increase carbon emissions relative
to other fuels used with equivalent efficiency
(U.S. DOE, 1987c; National Coal Council,
1987). The U.S. DOE has suggested the use
of alternative fuels and increased domestic
production of petroleum. However, these
alternatives could exacerbate the greenhouse
problem, particularly if alternative fuels were
coal-derived.
Total federal spending on R&D is not
the only measure of success. Some studies
suggest that the variations in funding levels
and priorities in U.S. R&D efforts have
reduced their effectiveness relative to more
VII-33
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Policy Options for Stabilizing Global Climate
TABLE 7-6
Government Efficiency Research and Development
Budgets in OECD Member Countries, 1986
Efficiency Total Efficiency
Budget R&D Budget as Percent
Country (millions of dollars) (millions of dollars) of Total
Japan 78 2,311 3
United States 275 2,261 12
Italy 48 761 6
West Germany 21 566 4
United Kingdom 43 378 11
Canada 34 336 10
Sweden 29 79 37
Greece 0 15 0
Denmark 5 14 36
Total OECD* 622 7,133 9
* Total includes minor additional expenditures. Excludes France.
Source: IEA, 1987.
VII-34
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Chapter VII: Policy Options
FIGURE 7-7
CHANGES IN U.S. RENEWABLE ENERGY
R&D PRIORITIES OVER TIME
(Million Dollars)
1000
800
600 -
o
: o
• C
o
400
200 -
1980 1981 1982 1983 1984 1985 1986 1987 1988 1989
Fiscal Year
Source: U.S. DOE, 1987a.
VII-35
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Policy Options for Stabilizing Global Climate
steady and long-term programs such as those
in Japan (Flavin, 1988; Chandler et al., 1988).
Federal R&D support may no longer be as
important for technologies reaching
commercial competitiveness, such as
photovoltaics; low energy prices have become
a more critical obstacle (Carlson, D., 1988).
The largest improvements in energy efficiency
often result from changes in processes or
products that serve multiple purposes; reduced
energy costs may be only a secondary
consideration (OTA, 1983). Narrowly focused
energy conservation programs may not
effectively address this objective. One
alternative is to establish research centers for
energy-intensive industrial processes. Such
centers could research multiple improvements
on a cooperative basis with industry and
academia, an approach currently incorporated
in the Combustion Research Program
operated by Sandia National Laboratories
(Chandler et al., 1988).
In 1989 the Oak Ridge National
Laboratory (ORNL) published a major review
of U.S. energy R&D entitled Energy
Technology R&D: What Could Make A
Difference (Fulkerson et al., 1989). The study
was conducted by more than 100 ORNL staff
members with additional help from experts
from other laboratories and R&D institutions.
The authors reviewed both public and private
expenditures and concluded that total U.S.
expenditure on energy R&D is in the vicinity
of $4 billion to 55 billion annually, or about 1
to 1.5% of total annual energy expenditures.
The ORNL study evaluated current
research budgets and priorities in terms of
their adequacy to meet future circumstances,
including a scenario in which the greenhouse
effect calls for reductions in the use of fossil
fuels. The report concluded that from the
perspective of global warming "the nation's
R&D agenda is not adequate nor balanced. A
much greater effort is needed to develop and
improve non-fossil sources and to improve the
efficiency and economics of end-use
technologies. The latter has the greatest
potential to reduce the use of fossil fuels in
the near to mid-term" (Fulkerson et al., 1989).
The timing and cost of a greenhouse-
firi p.nerov R#D nnlirv were also
oriented energy R&D
addressed by ORNL:
policy were also
Because of the substantial lead
time required [to develop new
technologies], it seems imprudent
to delay the R&D necessary to
provide the options that move the
energy system away from fossil
fuels at reasonable cost.
Furthermore, what will we have
lost by taking aggressive action
now? . . .[Improved efficiency and
non-fossil technologies] will be
useful in any event, and the cost of
achieving them on an accelerated
schedule is the increased cost of
R&D (Fulkerson et al., 1989).
To meet these goals and to reduce CO2
emissions, ORNL proposed a program of
about $1 billion annual additional energy
R&D expenditures as itemized in Table 7-7.
They suggest about $600 million of this
amount could be raised by a tax on fossil fuels
at the rate of 0.2%, with the remainder coming
from matching funds invested by private firms.
Oak Ridge reviewed many specific areas
where the potential for technological
improvement is considered very promising.
Some of the most important areas for research
are crosscutting technologies such as
improvements in materials science that would
produce benefits throughout the economy (see
also Williams et al., 1987).
Federal programs are also not the only
large source of energy R&D support. Several
states, notably New York, California, and
North Carolina, have created state agencies to
support energy R&D (see STATE and LOCAL
EFFORTS, below). Private sector support is
also large: the utility-supported Electric
Power Research Institute and Gas Research
Institute both have annual budgets in excess of
S100 million, and some of these organizations
give high priority to research on efficiency
improvements.
Another important consideration is the
allocation between basic science and more
applied research. The former has received
highest priority, but demonstration and
technology transfer programs can accelerate
acceptance of innovative ideas that have been
proven on a small scale but are not yet widely
adopted. The U.S. Department of Energy now
VII-36
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Chapter VII: Policy Options
TABLE 7-7
Additional Energy Technology R&D Expenditures
Needed to be Prepared to Control CO2 Emissions
(combined public and private sector investments)
Added Cost
R&D Area (million S per year)
Improve efficiency and economics of end-use and conversion technologies 300
Phased increase over several years to double the current national
level seems warranted by opportunities.
Improve nuclear power 300-400
Prototyping an advanced LWR (ALWR) with passive safety
features and an MHTGR which is fully passively safe would
probably cost $3 billion to $4 billion over the next decade.
Prototyping the liquid metal breeder with passive safety
features should be initiated in the first decade of the
next century.
Solar and renewables 200
Expanded budgets for biomass, hydroelectric (to capture 50
Gw of remaining capacity) photovoltaics, solar thermal electric,
wind, and others (phased increases over several years) seem
warranted by the technological promise.
Fusion
Better international coordination of the Si billion to $2 None, if improved world
billion per year expended worldwide is needed. cooperation achieved
Technologies for less-developed countries 100-200
This would be the U.S. part of a worldwide effort to
develop energy technologies for developing nations.
TOTAL 900-1100
Source: Fulkerson et al., 1989.
VII-37
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Policy Options for Stabilizing Global Climate
supports some technology transfer activities
for conservation and full-scale demonstration
of clean coal technologies to provide "proof-
of-concept" experience (Clean Coal Synfuels
Letters, 1988; U.S. DOE, 1987c). Some of the
technologies with greatest potential to reduce
greenhouse gases, such as advanced gas
turbines (see CHAPTER V), could also benefit
from full-scale demonstration and evaluation
(Williams and Larson, 1988).
Energy R&D should also include
examination of policy and program issues
(IEA, 1987). One very critical question is why
so many consumers often fail to invest in
energy conservation measures despite very high
rates of return; this behavior appears to be
irrational in economic terms (Kempton and
Neiman, 1987; Aronson and Yates, 1985).
Consumers also respond differently to loans,
rebates, and other subsidies even though they
have roughly equal cost to the government.
Another research need for policy
purposes is a more detailed data base on
international sources of greenhouse gas
emissions. The compilation of such data
should be an initial goal of the
Intergovernmental Panel on Climate Change.
Global Forestry Research and Development
The benefits of trees for storage of
carbon are widely accepted, but the elements
of a large-scale forestry program to stabilize
greenhouse gas emissions have yet to be fully
described (see CHAPTER V). Such a program
would seek to maximize global vegetation and
storage of carbon. The steps necessary to
accomplish this objective may not be entirely
consistent with the emphasis and goals of
existing governmental and commercial forestry
research programs. The preservation of
tropical forests, for example, is a critical
international environmental problem with
considerable impact on global climate change.
However, this effort may not be the most cost-
effective way to increase net global forest
cover, because the underlying causes are often
closely related to deeply rooted social ills that
require very long-term solutions. Large-scale
plantation forestry is one alternative, but the
economic criteria used in commercial forestry
may also have little relationship to maximizing
carbon storage.
Traditional forestry research priorities
have not emphasized conservation. Recent
reviews of forestry research in tropical
countries conclude that most projects have
focused on the creation of large-scale
industrial plantations and other activities to
promote the improved industrial use of timber
(FAO, WRI, World Bank, and UNDP, 1987).
According to the Tropical Forest Action Plan
prepared by an international task force,
forestry has not received the large-scale,
targeted research support devoted to
agricultural study of plant breeding and the
development of improved crop varieties. The
Plan proposed to begin responding to these
needs with a five-year, Si billion research
program.
Efforts to date indicate that forestry
research can produce markedly higher yields
through genetic improvement and better
management practices. For example, a
Brazilian paper company was able to double
yields from 33 to 70 cubic meters per hectare
per year through genetic selection and cloning
(WRI, World Bank, and UNDP, 1985).
Research and demonstration can also help
promote sustainable management practices; a
U.S. Agency for International Development
(U.S. AID) -funded village woodlot project in
Thailand shows that planting fuelwood species
can be profitable and environmentally
protective (U.S. AID, 1987).
More research on managing public
lands, pricing public resources, and other
policy aspects of tree planting is also needed.
For example, government policies in both the
developing and industrialized world have been
a major source of pressure on tropical forests,
but this relationship has not been thoroughly
studied. Excessive consumption of forest
products has also sometimes been encouraged
by underpricing of public resources in some
developing countries (see CHAPTER VIII).
Research to Eliminate Emissions of CFCs
Industry is now making substantial
efforts to reduce or eliminate emissions of
CFCs as discussed earlier (U.S. EPA, 1988;
Cogan, 1988). However, existing regulatory
incentives may not be adequate to assure that
all users of CFCs will make a serious effort to
find substitutes. The demand for some uses of
VII-38
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Chapter VII: Policy Options
CFCs, such as automotive air conditioning, is
highly inelastic because the cost is very low
relative to the total cost of the product and
there are no obvious short-term alternatives
(Federal Register, 1988). U.S. EPA is not only
considering regulatory changes to address this
problem, but also attempting to bolster
industry interest in alternatives through a
program of cooperative research on promising
technologies (U.S. EPA, 1988; Claussen, 1988).
Such efforts could be expanded as part of an
effort to phase out all CFC emissions as soon
as possible and could serve as a model for
programs to reduce emissions of other
greenhouse gases.
INFORMATION AND TECHNICAL
ASSISTANCE PROGRAMS
The government can facilitate the
development and adoption of new technologies
and strategies through many forms of
information and technical assistance programs.
These efforts complement research, pricing,
and other policies by making consumers more
aware of the value of energy conservation and
therefore more likely to respond to investment
opportunities. Information programs can
serve to improve consumer understanding of
the significance of energy costs, which are
often underestimated because they occur over
time. For example, many consumers do not
know the relative energy cost of home
appliances or that the cost of operating a
refrigerator over its lifetime will be greater
than the first cost. Information coming from
the government is also frequently perceived to
be more credible than similar information
coming from utility companies or other private
firms (Kempton and Neiman, 1987).
Information and technical assistance
programs take a variety of forms to serve a
range of specialized purposes. Within the U.S.
Department of Energy, R&D results are
disseminated to potential users through
"technology transfer" programs (U.S. DOE,
1987c). One element of this program is the
National Awards for Energy Innovation, which
annually recognizes outstanding achievements
in conserving and producing energy.
U.S. DOE also operates several energy
information services for different audiences
(U.S. DOE, 1987b). The Conservation and
Renewable Energy Inquiry and Referral
Service (CAREIRS) serves the general public
through a toll-free telephone number and
refers technical questions to one of several
hundred laboratories and expert agencies. In
FY 1987, CAREIRS responded to more than
40,000 inquiries. General information on
energy production and consumption is also
available through the National Energy
Information Center and the Solar Technical
Information Program. More specialized
assistance is provided by the National
Appropriate Technology Assistance Service
(NATAS), which helps evaluate new
technologies and suggests approaches to
commercialization.
The federal government has also
provided consumers detailed information on
the comparative energy cost of new cars and
appliances through mandatory labeling
requirements. These programs improve
market forces by making it easier for
consumers to make decisions about the value
of more expensive but more efficient models.
There is no standardized or widely
accepted system for communicating energy cost
information for homes and buildings, which
may be partly responsible for the slow rate of
improvement in this sector (Chandler et al.,
1988; Hirst et al., 1986). For example, such a
system could be used by lenders to evaluate
the expected energy cost of a home as a factor
in loan amounts, creating an incentive to
improve energy efficiency. Such a system is
used on a limited basis now by the Federal
National Mortgage Association (U.S. DOE,
1987c). Another model is in use by 12 banks
in Seattle (Hirst et al., 1986).
Several federal information programs
directed to small-scale energy use have been
gradually curtailed but still operate in many
states. One is the Residential and Commercial
Conservation Program, which requires electric
and gas utilities to offer home energy audits to
their customers for a minimal charge. The
program was not promoted effectively in most
parts of the country and participation has
typically been very low, although a few states
achieved notably better success (Hirst et al.,
1986). The Energy Extension Service provides
a small amount of federal support for state
energy information programs and technical
VII-39
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Policy Options for Stabilizing Global Climate
assistance programs targeted to individuals and
small energy consumers.
Another approach to improving
consumer awareness of energy costs is through
the introduction of technology that continually
reports electricity costs. Advances in
microelectronics and communications now
make it possible to provide such information
for a cost that could be offset by savings
achieved through better energy management
and shifts in time of use, and at the same time
allow closer tracking of marginal costs (Peddie
and Bulleit, 1985; Rosenfeld, 1985).
Federally supported programs have also
helped support development of computer
models and other analytical methods for
evaluating the energy use from new residential
and commercial buildings. These analytical
tools can be used by designers to lower the
energy use of buildings and as a basis for
calculating energy use for purposes of
minimum standards and incentive programs
(Vine and Harris, 1988). Computer models of
building energy use were a key product of the
Federal Building Energy Performance
Standards. The Standards began as a
mandatory federal regulatory program in 1976,
but Congress subsequently amended the law to
require only voluntary guidelines. The
standards have yet to be released in final form;
however, much has been learned in the
process, and interim products have been used
by industry and government. The federal
government could facilitate use of the final
rules by providing additional technical
assistance such as materials on compliance
methods (U.S. DOE, 1987c; Chandler et al.,
1988).
The integration of research, technical
assistance, and public information has a long
and productive tradition in federal agriculture
programs. The federal budget for such
activities is about S3 billion annually, and as of
1984 there were over 3,500 specialist extension
agents and over 11,000 county agents (OTA,
1986). As discussed in Chapters IV and V,
modifications in some farming practices such
as selection of crop varieties and fertilizers,
water use, and disposal of crop residues may
inhibit greenhouse gas emissions, although
more research is needed to establish the
efficacy of such changes. As our
understanding of agricultural sources of
greenhouse gas emissions improves, extension
activities could be used to teach farmers how
to reduce their emissions.
Information and technical assistance is
also an important function of bilateral aid, as
discussed in U.S. Bilateral Assistance
Programs (see CHAPTER VIII).
CONSERVATION EFFORTS BY FEDERAL
AGENCIES
The federal government is the single
largest consumer of energy in the United
States, accounting for 2.5% of total energy
consumption (U.S. DOE, 1987a).10 The
annual energy budget for over 500,000 federal
buildings and facilities is about $4 billion, plus
another $2 billion for federally assisted
housing. A Federal Energy Management
Program was established 12 years ago to
provide leadership in reducing these costs and
has achieved some success. According to U.S.
DOE, cumulative energy savings over the past
12 years are nearly 1.6 Quads, equivalent to
about $6.5 billion in savings (U.S. DOE,
1987a; see Table 7-8). In FY 1985 a ten-year
performance target for improving the energy
efficiency of federal buildings ended, having
attained a 16.6% reduction in energy per
square foot relative to a 20% target.
The government could use its buying
power to test and demonstrate energy
conservation and alternative energy sources.
Government procurement could help
demonstrate new products, acting as an
incentive for manufacturers worried about the
lack of a market and consumers worried about
being first-of-a-kind purchasers (Goldemberg
et al., 1987). The Department of Energy
expressed support for this role in the 1987
Energy Security report to the President: "The
federal government should lead by example in
testing and adopting cost-effective technologies
that use energy more efficiently, especially
those that minimize future reliance on
insecure supplies of oil" (U.S. DOE, 1987c).
According to the U.S. DOE, a major
obstacle to federal conservation efforts was
recently addressed through a change in federal
law. Conservation investments, although cost-
effective, may require a substantial initial
VII-40
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Chapter VII: Policy Options
TABLE 7-8
Federal Energy Expenditures and Cost Avoidance
FY L975-FY 1987
Annual Energy Cost
(S Million)
Buildings and Facilities
1975 1,812.453
1976 1,888.673
1977 2,162.395
1978 2,286.054
1979 2,636.361
1980 3,168.399
1981 3,713.200
1982 3,804.965
1983 3,863.248
1984 3,919.356
1985 4,054.799
1986 3,828.608
1987 3,941.605
Total
General Operations
1975 2,697.494
1976 2,310.695
1977 2,594.787
1978 2,710.483
1979 3,705.588
1980 6,195.928
1981 8,289.325
1982 9,828.685
1983 8,743.907
1984 7,728.081
1985 6,336.706
1986 4,006.669
1987 4,348.108
Total
ALL ENERGY TOTAL
Annual Energy Use
Reduction Rel. to
FY 1975 (BBtu)
58,080.4
51,847.4
66,013.3
77,885.9
97,947.3
99,466.9
92,207.3
98,559.4
64,706.3
27,131.1
50,877.7
6,465.6
129,389.8
115,884.7
139,408.6
112,222.9
94,910.6
33,191.0
6,669.7
9,260.1
18,506.1
49,557.8
63,407.1
26,606.8
Average Annual
Energy Cost
(S/MBtu)
2.107
2.355
2.675
2.879
3.370
4.157
4.882
4.955
5.073
4.928
4.868
4.731
4.617
2.578
2.520
2.789
2.989
3.967
6.513
8.182
9.454
8.432
7.258
6.358
4.077
4.264
Annual Energy
Cost Avoidance
(S Million)
136.779
138.692
190.052
262.475
407.167
485.597
456.887
499.992
318.873
132.074
240.702
29.852
3,299.142
...
326.062
323.202
416.692
445.188
618.153
271.569
63.055
78.081
134.317
315.088
258.511
113.451
3,363.369
6,662.511
Note: This table incorporates revisions to previously published energy consumption and cost data
submitted to U.S. DOE by federal agencies. Energy costs for FY 1975-1981 are estimated, based on
data provided by the Defense Fuel Supply Center and U.S. DOE's Energy Information Administration
(ELA). Energy costs for FY 1982-1987 are based on annual reports submitted to U.S. DOE by federal
agencies.
Source: U.S. DOE, 1987a.
VII-41
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Policy Options for Stabilizing Global Climate
investment in order to achieve energy and cost
savings over the long term (U.S. DOE, 1987a).
Agencies may now legally "share the savings"
from investments in conservation through
contracts for up to 23 years with companies
that supply the necessary equipment or
services in lieu of paying the full capital cost
upfront. Several states already have such
programs, which can serve as demonstration
programs for other levels of government and
the private sector and may facilitate future
federal efficiency investments. Texas has
implemented an energy performance audit
program for 18 major universities enforced by
a potential 10% withholding of administrative
funds. The audit includes a review of the
energy management program, including
procedures for tracking and monitoring, use of
audit activities, capital outlays, and
professional training programs. The entire
program has been highly cost-effective and, in
addition, has served to increase upper
management awareness of the energy
management opportunities under their control
(Verdict, 1988).
STATE AND LOCAL EFFORTS
State and local governments can make
an important contribution to the reduction of
greenhouse gas emissions (see Box 7-5). Much
environmental regulation and energy policy
are, to a considerable degree, state and local
responsibilities. For example, state public
utility commissions oversee decisions about the
need for new generating capacity and the
choice of fuel, and they can exercise their
discretion to promote or discourage particular
fuels to promote environmental objectives
(ABA, 1980; Randolph, 1988b).n
A growing number of states have
adopted programs to reduce costs and growth
in electricity demand through comprehensive
planning and conservation efforts supported by
electric utilities. There is evidence that the
potential impact of such programs is very large
and could allow substantial displacement of
fossil-fuel generating capacity in the future.
At least ten states have statutory requirements
and policies requiring that utilities examine
efficiency investment opportunities as part of
Box 7-5. Recent State Initiatives On Global Warming
During 1989, several states passed legislation or signed executive orders that applied
specifically to global warming. The most common approach has been the creation of
procedures to study the feasibility of reducing greenhouse gas emissions by a specific amount
by some target date. In Oregon, a bill passed in July requires a state strategy to reduce
greenhouse emissions 20% from 1988 levels by 2005. In Vermont, an executive order calls for
a similar plan to reduce both greenhouse gas emissions and acid rain precursors by 15% below
current levels by the year 2000; additional restrictions on CFCs were adopted by the legislature.
A New York executive order accompanying release of a state energy plan in September set a
goal of reducing CO2 emissions 20% by 2008. A study of how to achieve that goal will be
conducted jointly by the Energy Office, Department of Environmental Conservation, and the
Public Service Commission for presentation to the Governor by April 30,1990. A New Jersey
executive order on global warming requires state agencies to purchase the most energy efficient
equipment available "where such equipment or techniques will result in lower costs over the
lifetime of the equipment." In Missouri,, the state legislature created a commission to study the
effects of ozone depletion and global warming on the state and to identify means of reducing
the state's emissions; findings and recommendations are due in late spring 1990.
VII-42
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Chapter VII: Policy Options
a "least-cost" plan (Machado and Piltz, 1988).
However, in recent years some utilities have
reduced their commitment to conservation and
renewed efforts to promote new demand for
electricity in order to reduce the costs of
excess capacity.
One of the most comprehensive and
thoroughly evaluated programs is in the Pacific
Northwest. The Northwest Power Planning
Council, a regional planning agency created by
Congress in 1980, must by law evaluate
conservation as a potential resource
comparable to generation, and may not
support new plants until after first undertaking
less expensive demand-side measures. In
cooperation with the Bonneville Power
Administration and regional utility companies,
the region spent over $1.1 billion on
conservation efforts between 1979 and 1989.
Funds went for research, marketing, builder
training, promoting the implementation of
stronger building codes, and pilot projects.
The Council concluded that its conservation
programs had achieved energy savings at costs
ranging between 1.9 and 2.9 cents per kilowatt-
hour, much less than the cost of generation.
The Council has undertaken some
conservation programs despite a power surplus
because of the potential "lost-opportunity"
resource if, for example, new buildings are
constructed without cost-effective conservation
measures. Savings from improving the
efficiency of new buildings alone are estimated
at S700 million over 20 years (NPPC, 1988).
Using high economic growth assumptions, the
Council estimates that it would need almost
13,000 additional megawatts (MW) of
electricity but that more than 2,500 MW could
be obtained through additional conservation
efforts (NPPC, 1989).
A recent Michigan study focused on
opportunities to improve efficiency in the
residential sector (Krause, 1988). The study,
done by the Lawrence Berkeley Laboratory,
examined the technical and economic potential
for electricity conservation. Some of the key
findings were that 3400 GWhtyear, or 680 MW
of baseload equivalent, can be reliably saved by
2005. This is about 29% of the forecasted
demand for this date and is about two-thirds
of the technical potential (see Figure 7-8).
The result implies a steady decline in overall
residential electricity demand of about 1% per
year over the next 20 years. Most of the
projected savings could be purchased at a cost
of less than 3 cents per kWh assuming utilities
pay for the full extra first costs of consumer
investments; the average cost is about 1.1
cent/kWh, in contrast with short-run marginal
costs in Michigan of about 3 cents/kWh and
much higher costs for new capacity. The
greatest savings are from improving the
efficiency of lighting, water heating, and
refrigerators. The net present value of
implementing these savings over 20 years at a
7% discount rate would be $545 million.
Some states have undertaken impressive
programs to develop alternative energy
technologies suited to their climate and energy
needs. The North Carolina Alternative Energy
Corporation (AEC), for example, is funded by
voluntary contributions from electric utilities
recovered from ratepayers (Harris and
Kearney, 1988). The AEC has contributed
almost S6 million to projects that test or
demonstrate either conservation, load
management, or renewable energy
technologies. New York and California are
among the other states with substantial energy
research programs.
Local governments also undertake many
relevant activities. One traditional local
government function is to establish building
codes and land-use regulations. Some local
governments have implemented stringent
energy conservation requirements for new
housing. For example, Tacoma, Washington,
estimates that compliance with its code adds
only 52,000 to the cost of a new home but
saves electricity at a cost equivalent to 2
cents/kWh (much less than any new
generation) and offsets the need for 1 MW of
generation (Randolph, 1988a). Seattle, Santa
Monica, and several other cities have worked
out cooperative arrangements with their
utilities in which the utility provides audits or
other services on a reimbursable basis ~
sometimes at a profit (Randolph, 1988a). Two
California cities, Davis and Berkeley, require
compliance with minimum residential energy
standards as a condition for the sale of a home
(Randolph, 1988a).
The state and local role in limiting
greenhouse gas emissions is not limited to
energy regulation. Other state and local
VII-43
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Policy Options for Stabilizing Global Climate
FIGURE 7-8
COST OF POTENTIAL RESIDENTIAL ELECTRICITY
CONSERVATION IN MICHIGAN BY 2000
(1985 cents kwh)
10
8
\
£ «
• c
c •
o o
O U>
». 00
O 0)
*• 1"
o
o
Average Price of Electricity
Short-run marginal costs, 7
existing plants '
400 800 1200
2400 2800 3200
3409
683
1600 2000
gwh
0 300
Megawatt Baseload
Cost estimates are based on an analysis of territories served by Consumers
Power and Detroit Edison companies and assume a 7% discount rate.
Source: Llpkls, 1988.
VH-44
-------
Chapter VII: Policy Options
authority that could be exercised to lower
greenhouse gas emissions includes
management of landfills and regulation of
existing stationary sources of air pollution.
Another source of large, short-term
opportunities may be tree-planting programs.
As discussed in Chapter V, urban tree planting
can reduce local temperatures, thus reducing
summer energy needs for air conditioning,
while simultaneously storing carbon dioxide
for a relatively modest cost (Akbari et al.,
1988). Cities have undertaken large-scale
tree-planting programs to improve air quality,
lower summer temperatures, and beautify
neighborhoods. In Los Angeles, a non-profit
group called TreePeople organized a successful
effort to plant 1 million trees prior to the 1984
Olympic games. A new initiative announced
by Mayor Bradley in October 1988 calls for
planting 5 million trees and painting surfaces
light colors to save 500 MW of peak power, or
the equivalent of a large new coal plant
(Lipkis, 1988).
Some states have also taken steps to
help reduce emissions of CFCs. For example,
Massachusetts recently fined a foam
manufacturer for failing to recover CFCs and
obtained an agreement from the company that
it will reduce emissions in the future (New
York Times, 1988).
PRIVATE SECTOR EFFORTS
Because of the global nature of the
greenhouse problem and the lack of direct
economic incentive for solutions, much of the
impetus for solutions will have to come from
governments. Nevertheless, private
corporations, non-governmental organizations,
and individuals can make important
contributions without waiting for government
direction. Indeed, there are already several
good examples of private initiatives that will
contribute to reducing greenhouse gas
emissions.
There have also been a number of
important actions by private companies to
reduce emissions of CFCs in advance of any
government mandate. In September 1986 ~ a
year before the Montreal Protocol -- the
DuPont Company announced that they could
produce chemical replacements for ozone-
depleting CFCs within five years if
governments provided proper regulatory
incentives to support the new market. The
substitutes either do not contain chlorine, one
of the chemicals that threatens the ozone
layer, or they contain hydrogen, resulting in a
much shorter and therefore less dangerous
atmospheric lifetime. As evidence of the risk
to the ozone layer mounted, other companies
also announced support for efforts to reduce
CFC emissions. The food packaging industry,
for example, voluntarily agreed to substitute
food packaging made with HCFC-22 rather
than with CFC-12; HCFC-22 has an ozone-
depletion potential roughly one-twentieth that
of CFC-12 and a greenhouse forcing potential
about one-third that of CFC-12.
Since March 1988, when the National
Aeronautics and Space Administration
(NASA) Ozone Trends Panel announced its
conclusion that global ozone depletion has
been detected, several major CFC producers
and users have stated their support for an
orderly phase-out of all production of CFCs by
the turn of the century. Some companies have
restricted sales to existing markets, stopped
development work on new applications for
regulated products, and committed neither to
increase production capacity nor to sell
technology to others.
It is often the private non-governmental
organizations that are uniquely capable of
promoting grassroots development and
alleviating poverty (World Bank, 1987). The
World Bank has supported the involvement of
private companies in the design and
implementation of projects, particularly
projects on social forestry, agroforestry, and
the environment. U.S. AID and the Peace
Corps have given a high priority to involving
private voluntary organizations in community
forestry projects undertaken through the Food
for Peace Program (Joyce and Burwell, 1985).
The Tropical Forestry Action Plan also
includes strong support for involving private
organizations.
Applied Energy Services (AES) of
Arlington, Virginia, a private company
involved in cogeneration projects, recently
hired a non-profit organization, the
International Institute for Environment and
Development, to assist in identifying potential
reforestation projects capable of providing a
VII-45
-------
Policy Options for Stabilizing Global Climate
carbon sink equal to the emissions from a new
180 MW coal-fired plant in Connecticut. This
approach reflects the offset concept discussed
earlier. One problem in making this exchange
on a voluntary basis was that the company had
difficulty obtaining financing despite the small
cost of the trees relative to the total
project.12
Many of the strategies necessary to
reduce greenhouse gas emissions require
changes in technologies or policies that can
only be accomplished by large corporations
and governments. However, there are some
important exceptions, particularly tree
planting. Reviving the tradition of Arbor Day
could provide a very effective symbol of
individual responsibility for greenhouse gas
emissions; one hectare of well-managed
Douglas fir trees can absorb the average
American's lifetime per capita emissions of
CO2 (about 400 tons, or 5 tons carbon per
year for 80 years).13 The cost of planting
that many trees on a large scale is difficult to
estimate, but S1500 is a reasonable
approximation - a large but not impossible
lifetime investment.14
As these examples suggest, the
government can help foster private initiatives.
In some cases, regulatory obstacles impede
voluntary efforts and government can help
remove them. In other cases, the government
may be able to help bring parties together and
provide technical information or assistance.
The important point is that government can
help promote voluntary efforts to reduce
greenhouse gas emissions.
VII-46
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Chapter VII: Policy Options
ADDENDUM TO CHAPTER VII:
ANALYSIS OF SPECIFIC PROPOSALS
FOR REDUCING GREENHOUSE GAS
EMISSIONS
POTENTIAL OPTIONS TO REDUCE
GREENHOUSE GAS EMISSIONS
Chapter VII provides a general
discussion of policy options for responding to
global warming. This addendum uses some
specific policy proposals that have recently
been analyzed to illustrate how such a
combination of policy options might
contribute to reducing greenhouse gas
emissions. Since the specific proposals
discussed in this section reduce different types
of greenhouse gases, the effectiveness of each
proposal for reducing greenhouse gas
emissions will be evaluated on a CO2-
equivalent basis using the Global Warming
Potential (GWP) of individual gases. The
GWP, discussed in Chapter II and the
Executive Summary, provides a way to express
total greenhouse gas emissions in terms of
CO2 equivalence (we convert all CO2 values
from their full molecular weight to a carbon-
only basis to follow the convention used in the
carbon-cycle literature). Specifically, we have
used the 100 year GWPs developed by the
Intergovernmental Panel on Climate Change
(IPCC).
As discussed throughout Chapters VII
and VIII, there are a wide range of policies
that could reduce greenhouse gas emissions.
Those discussed below are just a few of many
options currently under discussion, and in
some cases they may not represent the most
cost-effective options. They are presented
here to serve as a simple illustration of
possible policy initiatives that may help to
reduce greenhouse gas emissions and how the
GWP approach may be used to assess the
reductions in emissions resulting from
alternative policy options. The discussion of
these options does not imply endorsement;
additional analysis would have to be conducted
before any recommendations could be made.
Tree Planting
Reforestation initiatives can increase the
uptake of carbon as the trees mature. A
recent proposal would sequester approximately
9 million metric tons of carbon (106 t C) per
year by the year 2000 and about 45 106 t C by
2010 ' (Moulton and Andrasko, 1990).
Congress has approved initial appropriation
for this reforestation initiative as a part of a
larger conservation program in the 1990 Farm
Bill that would set a goal of planting one
billion trees per year over a ten to twenty year
period, as well as improving forest
management practices.
U.S. DOE Energy Efficiency Initiatives
Reductions of 25.3 106 t C may be
achieved through recent U.S. DOE energy
efficiency initiatives (Egan, 1990; Williams,
1990).1S These initiatives are aimed at
increasing energy efficiency in order to
decrease demand for electricity generated
primarily with fossil fuels, which reduces the
amount of CO2 emissions resulting from
energy production. Specific initiatives include:
• Increase Lighting Efficiency in Federal
Buildings. An annual electricity savings of 0.05
quads, equivalent to a reduction in emissions
of 1.2 10* t C by 2000, is expected if Federal
agencies fully comply with the relevant
Executive Order. This Executive Order
establishes energy efficiency targets for
building lighting based on state-of-the-art
techniques.
• Increase Lighting Efficiency in
Commercial Buildings. Emissions reductions of
2.2 106 t C are expected by 2000 if 50% of
commercial buildings convert to high efficiency
lighting. This is equivalent to an average
savings of 25% of electrical demand for
lighting, or an electricity savings of 0.125
quads.
• Promote State Least-Cost Utility
Planning. A reduction in the need for coal
and other fossil fuels for electricity generation
of 7.5%, equivalent to a savings of 0.48 quads
of electricity, or a reduction in emissions of 8.2
1061C by 2000, may be achieved through state
efforts to institute integrated, least cost
resource planning for electric utilities to
achieve greater end use energy efficiency.
• State Adoption of U.S. DOE Interim
Building Standards. Emissions reductions of
7.4 10° t C, or 0.43 quads of electricity, may be
VII-47
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Policy Options for Stabilizing Global Climate
expected by 2000 if states make current
voluntary guidelines for buildings mandatory.
Federal buildings currently must meet new
U.S. DOE interim building standards
beginning in 1989. The energy savings
estimate assumes a 50% acceptance rate for
new non-federal buildings and a 20%
reduction in energy demand per building.
• Expand Energy Analysis and Diagnostic
Centers to Increase Energy Audits. Emissions
reductions of 5.5 106 t C, equivalent to 0.28
quads, including 0.05 quads of electricity, may
be expected by 2000 if the energy audit
program is expanded. This initiative assumes
that the program is expanded to include 40
energy efficiency engineering centers by 2000.
These centers are assumed to audit 3% of the
eligible industrial facilities by 2000; 60% of the
audit recommendations are assumed to be
implemented, which results in a 15%
improvement in energy efficiency.
• Adoption of U.S. DOE Building
Standards by U.S. HUD. The U.S. Department
of Housing and Urban Development (U.S.
HUD) is currently designing a program to
adopt U.S. DOE building standards that, if
successful, are estimated to achieve annual
efficiency gains of 0.05 quads, or a reduction in
emissions of 0.7 106 t C by 2000. If
implemented by U.S. HUD in public housing
assistance programs, it may provide a 25%
efficiency increase in buildings that are
refurbished, if 1.4 million units in the 7 major
public assistance programs are retrofitted by
2000.
U.S. DOE Renewable Energy Initiatives
An additional 3.8 106 t C of emissions
may be reduced by 2000 through imple-
mentation of renewable energy initiatives that
reduce demand for fossil fuel-fired electricity
(Egan, 1990; Williams, 1990). Specific
initiatives are:
• Expand Hydroelectric Power.
Hydroelectric power would be expanded at
both existing and new sites by working with
permitting/development authorities to
streamline the present complex processes for
hydropower development. This initiative may
increase the current level of 90,000 Mw to a
maximum of 110,000 Mw in 2000. If 25% of
the increased potential could be realized by
2000, electricity requirements generated with
fossil fuels may be reduced by 0.27 quads,
which is equivalent to a reduction in emissions
of 6.7 106 t C by 2000. (Fov this analysis this
estimate was reduced by 50% to 3.3 106 t C).
• Transfer Photovoltaic Technology. By
increasing the transfer rate of photovoltaic
technology to the marketplace, savings of 0.03
quads of fossil fuel electricity, equivalent to
emissions reduction of 0.5 106 t C, may be
achieved by 2000. This would be accomplished
by increasing photovoltaic capacity to 675
MW.
U.S. DOE Appliance Standards
Annual electricity savings of 0.15 quads
by 2000, equivalent to emissions reduction of
3.7 106 t C, may be achieved through revised
U.S. DOE appliance standards (Egan, 1990;
Williams, 1990). The standards, applied to
1993 and subsequent model years, would
increase the energy efficiency of refrigerators
and freezers, washers, dryers, and dishwashers,
assuming consumer purchases continue similar
to today's buying and replacement patterns.
The standards applying to refrigerators and
freezers have already become law, while the
remaining standards are still being
promulgated.
Clean Air Act Provisions
Emissions reductions of 15.6 106 t C
may be achieved by 2000 through conservation
initiatives implemented as part of the Clean
Air Act (CAA) Amendments passed by
Congress in 1990. The initiatives concern acid
rain and transportation fuels and would reduce
emissions of CO2.
• Acid Rain Controls. Emission reductions
of 14.9 106 t C would be achieved by 2000
assuming reduction of 5% in end-use demand
from current coal-fired generation. Acid rain
control provisions require SO2 reductions at
current coal facilities but allow the facilities to
determine how the reductions will be met.
Some reductions are assumed to occur due to
reductions in electricity demand that is
generated at older, less efficient coal-fired
powerplants. New powerplants must obtain
offsetting emission allowances.
VII-48
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Chapter VII: Polky Options
• Biofuels Program. Emissions reductions
of 0.2 106 t C would be achieved by the year
2000 by increasing the use of biofuels,
particularly ethanol. This would be achieved
by replacing 13% of gasoline use with a
gasoline mixture of 10% ethanol, which would
reduce CO2 emissions assuming that the
ethanol is made from a biomass feedstock that
is replaced or recycled. This reduction
represents 50% of the expected oxygenated
fuel required by the Clean Air Act.
• Natural Gas Program. Emissions
reductions of 0.5 106 t C would be achieved by
the year 2000 by replacing 1% of the gasoline
used with compressed natural gas, resulting in
a 20% decrease in CO2 emissions.
Landfill Regulations
Pending regulations under the current
Clean Air Act provisions regarding emissions
of methane from landfills would reduce
emissions by about 9.0 Tg CH4 (equivalent to
44 106 t C) by 2000 (U.S. EPA, 1990a).
Landfill control regulations will require the
collection of landfill gases and the combustion
or recovery of these gases. These regulations
are primarily directed at reducing emissions of
VOCs and toxic air pollutants, but will result
in reducing CH4 emissions simultaneously.
There are approximately 6,000 active landfills
in the U.S. that generate about 15.5 Tg/yr of
methane. About 9.0 Tg of CH4 is estimated to
be recovered, reflecting a recovery rate of
approximately 60%. Assuming a GWP of 18,
emissions reduction of about 160 106 t CO2
(44 106 t C) may be achieved by 2000.16
Montreal Protocol and CFC Phaseout
The Montreal Protocol is assumed to be
strengthened by adoption of a total CFC
phaseout, which reduces emissions
approximately 119 106 t C (i.e., on a CO2-
equivalent basis) by 2000 (U.S. EPA, 1990b).
The Montreal Protocol currently calls for a
50% reduction from 1986 levels in the
production of CFC-11, -12, -113, -114, and
-115 by 1998, and a freeze on the production
of halon 1211, 1301, and 2402 at 1986 levels
starting in approximately 1992. A phaseout of
controlled CFCs and halons by 2000 was
agreed to in principle by the U.S and several
other countries in the London Amendments to
the Montreal Protocol in June 1990. This
would eliminate 95% of the radiative forcing
due to CFC emissions in 2000. Included in
the phaseout are CFC-11, -12, -113, -114,
HCFC-22, CC14, HCFC-134, HCFC-141b, and
HCFC-124.
How These Options May Reduce Emissions to
Current Levels
Table 7-9 shows the emissions
reductions in CO2 and carbon equivalents of
the policy options discussed above. If all of
these initiatives were implemented, the options
have the potential to reduce emissions by
approximately 290 106 t C by the year 2000.
However, these initiatives do not represent a
recommended or preferred set of options, but
rather are readily-available examples of
options to illustrate the potential for reducing
carbon emissions.
Table 7-10 provides estimates of
greenhouse gas emissions for 1987 as well as
projected baseline emissions in 2000 that
assume no policy actions (as described above)
are taken. These baseline CO2-equivalent
emissions were developed by U.S. EPA and
U.S. DOE based on best-available estimates.
To demonstrate one possible method for
reducing emissions close to current levels, we
have also included the potential reductions
from the policy options package described
above. If the 290 1061C reduction is achieved
successfully by implementing all of these
options, greenhouse gas emissions could be
reduced to less than 1987 levels bv the year
2000, from 2587 106 t C to 2250 10* t C.
ADDITIONAL POLICY OPTIONS
U.S. EPA has begun investigating a
range of additional policy options that would
provide additional reductions in greenhouse
gas emissions in the future. These options
include tax and non-tax initiatives. It should
be noted that these additional policy options
represent ongoing work at U.S. EPA and
therefore the results are considered
preliminary. The full economic and
environmental impacts of these initiatives have
not been fully evaluated.
VII-49
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Policy Options for Stabilizing Global Climate
TABLE 7-9
Emissions Reductions from Current Policy Initiatives by 2000
(in 106 metric tons on a CO2-Equivalent Basis)3
POLICY OPTION
Tree Planting
U.S. DOE Efficiency Initiatives
Federal Buildings Lighting
Commercial Buildings Lighting
Promote State Least Cost Utility Planning
Interim Building Standards
Expand Energy Analysis
HUD Adoption of Standards
U.S. DOE Renewable Initiatives
Expand Hydropower
Transfer of Photovoltaic
U.S. DOE Appliance Standards
Clean Air Act Provisions
Acid Rain
Biofuels
Natural Gas
Landfill Regulations
CFC Phaseout
TOTAL
CO2
30.0
92.7
4.5
8.2
30.0
27.3
20.0
2.7
14.0
12.2
1.8
13.6
57.3
54.5
0.9
1.8
160.0
693.0
1060.6
CO2as
CARBON
9.0
25.3
1.2
2.2
8.2
7.4
5.5
0.7
3.8
3.3
0.5
3.7
15.6
14.9
0.2
0.5
44.0
189.0
290.0
a
Based on conversion to a CO2-equivalent basis using 100-year GWPs.
VII-50
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Chapter VII: Policy Options
TABLE 7-10
Emission Estimates for 1987 and 2000
(106 metric tons carbon)3
GAS
CO2
CH4
VOCs
NOX
CO
N2O
CFC
Total
a Based on conversion to a CO2-equivalent basis using 100-year GWPs.
b Includes policies currently under discussion that would achieve about 290 106 t C in emission
reductions.
c The difference in 2000 between the Baseline and Current Policy cases is about 337 106 t C. This
is greater than the total shown in Table 7-9 because the emission reductions attributable to changes
in VOCs, NOX, and CO are not included in Table 7-9.
Sources: Egan, 1990; IPCC, 1990d; Moulton and Andrasko, 1990; Pechan, 1990; U.S. EPA, 1989,
1990a, 1990b, 1990c; and Williams, 1990.
1987
1319
235
71
210
52
74
463
2424
Baseline
1565
252
72
210
52
74
362
2587
2000
Current
Policvb
1508
208
49
193
45
74
173
2250°
vn-si
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Policy Options for Stabilizing Global Climate
Tax Initiatives
Two sets of tax-based policy options are
being evaluated that may reduce CO2
emissions. The first set of options examines
transportation taxes, including a federal
gasoline tax and an oil import fee. The second
set of options evaluates a general carbon tax
on fossil fuels. These options are briefly
discussed below.
Transportation Taxes
The effects of a federal gasoline tax and
an oil import fee were estimated using the
Data Resources Incorporated (DRI)
Transportation model (DRI, 1990). These are
preliminary DRI model estimates. Results for
the transportation taxes are presented in Table
7-11. It was assumed that the taxes were
phased in over time. A S0.33/gallon tax is
estimated to reduce emissions by 16 1061 C by
the year 2000, while a $1.24/gallon tax yields
an emissions reduction of 78 106 t C by the
year 2000. An oil import fee of S6.00/barrel
results in emissions reduction of 30 106 t C by
the year 2000.
Carbon Taxes
Three models were used to estimate the
effects of carbon taxes by the year 2000: the
Manne-Richels Global 2100 model (Manne
and Richels, 1990a, 1990b, 1990c), the DRI
national energy model, and the Dynamic
General Equilibrium Model (DGEM).17 A
range of taxes was examined: from S5.00/ton
carbon to S25.00/ton carbon. The results for
each model are presented in Table 7-11. For
the lowest tax evaluated, i.e., a $5/ton carbon
tax, estimates on the amount of emission
reductions are: 9 106 t C for the Manne-
Richels model; 24 106 t C for the DRI model;
and 62 106 t C for the DGEM model.
Non-Tax Initiatives
Two potential non-tax initiatives, tighter
landfill regulations and an increased tree
planting initiative, have been evaluated that
could provide additional reductions in
greenhouse gas emissions. These initiatives
are briefly described below.
Tighter Landfill Regulations
As discussed earlier, landfill regulations
currently under discussion as part of the Clean
Air Act regulations would limit methane
emissions from decomposition of organic
wastes. If such regulations were tightened
beyond these pending U.S. EPA regulations,
methane emissions could be reduced by an
additional 7.9 Tg, resulting in a 39 106' t C
reduction on a carbon equivalent basis (U.S.
EPA, 1990a).
Increase in Tree Planting
The tree planting initiative discussed
earlier is designed to plant one billion trees
annually for a ten to 20 year period. If the
size of this program were doubled so that an
additional one billion trees were planted per
year, an additional reduction of 9 106 t C may
be attained (Moulton and Andrasko, 1990).
Implications of Additional Policy Initiatives
A comparison of the effects of
transportation and carbon taxes, as forecast by
the DRI model, suggests that a carbon tax is a
preferable policy option from the standpoint
of achieving CO2 emissions reductions. A
S5.00/ton carbon tax is equivalent to a
SO.Ol/gallon gasoline tax, yet the carbon tax
yields 25 106 t C of carbon emission
reductions, whereas a S0.33/gallon gas tax
yields only a 16 106 t C emissions reduction.
However, no distributional or equity issues
associated with these tax initiatives have been
examined. Also, given the range of uncertainty
in the estimated effects of tax options, any
conclusions based on these initiatives as
discussed here should be considered
preliminary.
Although these are preliminary results,
it is informative to note the effect of these
additional options when combined with the
policy options discussed earlier. The first set
of policy options reduced emissions by 290 106
t C, reducing greenhouse gas emissions to
about 93% of the 1987 emissions level by the
year 2000. As one example of additional
options, if we assume a combination of a
carbon tax of $5.00/ton (based on the DRI
VII-52
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Chapter VII: Policy Options
TABLE 7-II
Emission Reductions from Potential Tax Initiatives for the Year 2000
(106 metric tons of carbon)
DRI
DGEM
Carbon Reductions
(million tons')
Transportation Taxes
Gasoline Tax
S0.33/gallon 16
Sl.24/gallon 78
Oil Import Fee
$6.00/barrel 30
Carbon Taxes ($/ton)
Manne-Richels
S5.00 9
S 10.00 18
$15.00 27
S5.00 25
S 10.00 49
S15.00 74
S25.00 124
S5.00 62
S10.00 124
S15.00 182
S25.00 247
Sources: DRI, 1990; Manne and Richels, 1990a, 1990b, 1990c; and Montgomery, 1990.
VII-53
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Policy Options for Stabilizing Global Climate
Model), the tighter landfill regulations, and an
increase in tree planting, additional emissions
reduction of 73 106 t C may be possible.
When added to the first combination of
options, these additional options would reduce
estimated emissions in the year 2000 to 2177
106 t C, or about 10% less than 1987
emissions.
IMPLICATIONS IF ONLY CO2 IS
CONSIDERED
The preceding analysis compares
emission reductions on a CO2-equivalent basis
for all of the greenhouse gases. Because all of
these gases contribute to the global warming
problem, this approach is valuable as one
means for comparing the relative contributions
of each gas to the problem. However, because
CO2 is the major greenhouse gas and CFCs
will be reduced due to the Montreal Protocol
and the recently revised London Agreement,
much of the national and international debate
has focused on the role of CO2 and policy
actions that could be taken to reduce
emissions of this gas only.
If only CO2 emissions are considered for
achieving specific targets such as stabilization
at current levels, not all of the policies
discussed in the previous section would
contribute to the attainment of the target. For
example, landfill regulations primarily control
CH4 emissions, while the CFC phaseout
focuses on reducing the use of CFCs and
related chemicals. Several of the policies
would contribute to reducing CO2 emissions
directly, specifically programs that affect
energy use or forestry practices, such as the
U.S. DOE appliance standards, the U.S. DOE
energy efficiency programs, the Clean Air Act
proposals, and the tree-planting initiative. If
only direct CO2 emission reductions are
considered, reductions estimated for current
policy commitments in the year 2000 total
about 57 million tons of carbon, which is a
reduction of about 4% from estimated CO2
emissions for 2000; CO2 emissions for 2000
would still be about 14% higher than 1987
levels. The additional policies discussed
above, such as a carbon tax and an increase in
a tree planting program, could reduce total
CO2 emissions further. These additional
initiatives, however, would not be sufficient to
reduce CO2 emissions to 1987 levels unless
reductions of about 190 106 t C could be
obtained. This level of reductions is only
achievable with a carbon tax of about S15/t C
based on the DGEM analysis. (For further
discussion, also see Box 1-6, which discusses
the preliminary results of an analysis that
evaluates the technology costs for reducing
CO2 emissions from the U.S. energy sector;
this analysis evaluates only the technical
potential for reducing CO2 emissions, not the
full economic costs that would be incurred to
actually achieve the reductions.)
VII-54
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Chapter VII: Policy Options
Box 7-6. A Technology Cost Analysis of U.S. Energy Options
for Reducing CO2
As part of its ongoing analyses on greenhouse gas emission reduction options, U.S.
EPA has been examining a variety of options for reducing CO2 emissions from the
consumption and production of energy. To assist in this effort, the MARKAL (Market
Allocation) model has been employed to analyze least cost options for reducing CO2 emissions
from the energy sector. MARKAL is a dynamic linear programming model of U.S. energy
supply and demand by sector developed in the late 1970s at Brookhaven National Laboratory
and Kernforschungsanlage Julich in West Germany and recently updated for U.S. EPA.
Current research with MARKAL is attempting to identify least-cost strategies for reducing
CO2 emissions. MARKAL focuses on technological options for reducing emissions and
considers the engineering costs of these options; it does not, however, address the specific
policy actions that would have to be implemented to achieve the technological reductions. For
example, MARKAL may identify that gasoline use in the transportation sector can be reduced
for a certain cost by building more energy-efficient vehicles; it does not evaluate how
successfully different policies, such as a gasoline tax or higher CAFE (Corporate Average Fuel
Economy) standard, may be at achieving the energy efficiency improvements. In this example
costs of achieving specific CO2 reductions will vary depending on the cost of different
technologies and future fuel prices. This approach serves as a scoping analysis to identify those
areas where emission reductions may be achieved at least cost, although identification of all
costs would require further analysis.
Preliminary results using MARKAL have been estimated for three emission reduction
targets: 1) stabilization of CO2 emissions by 2010; 2) 10% reduction in CO2 emissions by 2010;
and 3) 20% reduction in CO2 emissions by 2010. The table below summarizes the results for
these cases.
Estimated Costs to Achieve CO2 Reductions in 2010
Total Reductions Total Costs Cost/ton
Case (106tons) CIO9 S) fS/ton>
Stabilization 56 0.22 3.95
10% Reduction 126 1.22 9.70
20% Reduction 197 3.22 16.353
TOTAL 197 3.22 16.35
a Estimated marginal cost of emission reductions is $39/ton.
The results presented in the table above are preliminary and do not reflect the total
costs of achieving the indicated reductions since only technology costs and energy costs are
included in the estimates; they do reflect the estimated costs that consumers would incur once
the decision has been made to purchase the more energy-efficient technologies.
Source: Morris et al., 1990.
VII-55
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Policy Options for Stabilizing Global Climate
NOTES
1. U.S. DOE publishes Gas Mileage Guides,
which list the fuel economy of all new car
models; however, the number of guides
distributed has been reduced from 10 million
to 3 million annually.
2. The 5160 billion figure is derived by first
calculating what total expenditures on energy
in 1985 would have been had energy intensities
remained constant at 1973 levels and 1985
price levels prevailed, and then subtracting
actual expenditures on energy in 1985. For
further discussion, see Chandler et al. (1988)
and U.S. DOE (1987c).
3. First-cost sensitivity refers to the tendency,
common to many consumers, to prefer a
product that has a low initial cost to a higher-
priced alternative, which might be much more
cost-efficient over the long term. In other
words, the upfront costs to consumers tend to
dominate the purchase decision more than a
conventional economic analysis would predict.
The use of a hefty excise tax may affect
consumer decisions more acutely than would
the gasoline expenses for operation of an
inefficient vehicle, which occur in smaller
amounts and at intervals rather than all at
once.
4. The results of these programs have been
periodically reported and evaluated by the
Electric Power Research Institute, the
American Council for an Energy Efficient
Economy, and others. See, for example,
Berman et al. (1987) and ACEEE (1988).
5. One domestic automotive company
reportedly estimates that consumers will seek
a 1 mpg improvement in fuel efficiency for
every 20 cent increase in gasoline prices
(Bleviss, 1988).
6. One expert has noted that "No aspect of
America's energy price system is more
peculiar, in comparison with other industrial
countries, than the absence of a substantial
national sales tax on gasoline" (Nivola, 1986).
7. FERC publishes periodic compilations of
"qualifying facilities," projects that have
formally requested status as entitled to the
benefits of PURPA. However, the list is only
an approximation of actual activity, since not
all projects file such applications; some file
after they have already begun operation, and
some applications are made for projects that
are never completed.
8. Joint Memorandum of the Soil
Conservation Service, U.S. EPA, Fish and
Wildlife Service, and U.S. Forest Service on
the Conservation Reserve Program Filter Strip
Initiatives, April 29, 1988.
9. One excellent source of information on
technologies, programs, and policies on energy
efficiency in buildings is the biennial
proceedings of the summer study program
organized by the American Council for an
Energy Efficient Economy (ACEEE, 1988).
10. Expenditures on energy in FY 1987 were
over $8 billion, or 0.8% of the federal budget.
11. For example, Washington offers utilities a
higher rate of return on investments in
renewable energy systems, while Texas requires
that utilities first consider using renewable
energy for new capacity additions and that
owners of renewable energy generators under
10 MW who wish to sell power to non-utilities
employ retail wheeling (use of transmission
lines).
12. The program will cost the company S2
million for an endowment to finance a 10-year
tree planting program by CARE, the
Guatemalan forest service, and the Peace
Corps to support 40,000 small farmers in
planting 52 million trees in plantations and
agroforestry systems. Over the 40-year life of
the plant, 15 million tons of carbon will be
fixed at a total cost of $14 million cash and
contributed labor. AES is considering
providing similar offsetting forestry projects
for nine other plants. The costs are expected
to be only about 0.1 cents per kWh because
the projects will take place in developing
countries and some labor will be contributed.
CARE officials informally estimate that the
project could be replicated perhaps 100 times
given current institutional capability and land
availability (WRI and IIED, 1988).
13. Other species would require more land,
but with research it may be possible to do
substantially better.
VII-56
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Chapter VII: Policy Options
14. A more detailed discussion of the
feasibility of large-scale tree planting is
provided in Chapter V.
15. Estimates of the amount of energy saved
and CO2 emissions reduced as a result of
specific energy efficiency initiatives are
sensitive to many assumptions incorporated
into the U.S. DOE analysis. The U.S. DOE
estimates have been used without extensive
review for this illustrative discussion.
16. IPCC (1990a) estimates that CH4 has a
100-year GWP of 21. In its analysis, U.S. EPA
assumed that all CH4 recovered from landfills
would be flared immediately, thereby
converting CH4 to CO2 in the process. The
IPCC indicates that the GWP for CH4 after it
becomes CO2 in the atmosphere is 3.
Therefore, the avoided impact due to
recovering CH4 and flaring it is represented by
using a GWP of 18.
17. A thorough description and comparison of
these models is contained in Montgomery, D.,
Effects on Energy Markets and the U.S.
Economy of Measures to Reduce CO2 Emissions
from Fossil Fuels, draft report presented at the
MIT Conference on Energy and the
Environment in the 21st Century, March 1990.
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USFS (United States Forestry Service). 1987.
The South's Fourth Forest. USFS, Washington,
D.C
Verdict, M. 1988. The new energy audit tool:
Performance audits for energy management.
In National and Regional Conservation
Programs: Proceedings of the 1988 ACEEE
Summer Study on Energy Efficiency in Buildings.
ACEEE, Washington, D.C.
Vine, E., and J. Harris. 1988. The experience
of energy conservation programs with new
commercial buildings. In National and
Regional Conservation Programs: Proceedings
of the 1988 ACEEE Summer Study on Energy
Efficiency in Buildings,. ACEEE, Washington,
D.C.
Weedall, M., R. Weisenmiller, and M.
Shepard. 1986. Financing Energy Conservation.
ACEEE, Washington, D.C.
Weinberg, A 1988. Energy policy in an age
of uncertainty. Issues in Science and
Technology 5:81-85.
Williams, R.H. 1988. Are Runway Energy
Capital Costs a Constraint on Development?
Presented at International Seminar on the
New Era in the World Economy. August 31-
September 2, 1988, Sao Paulo.
Williams, R.H., and E. Larson. 1988.
Aeroderivative turbines for stationary power.
Annual Review of Energy 13:429-489.
Williams, R., E. Larson, and M. Ross. 1987.
Materials, affluence, and industrial energy use.
Annual Review of Energy 12:99-144.
Williams, T. 1990. Private communication
between A. Cristofaro, U.S. EPA, and T.
Williams, U.S. DOE. June 6.
World Bank. 1987. Annual Report 1987.
World Bank, Washington, D.C.
WRI (World Resources Institute) and IIED
(International Institute for Environment and
Development). 1988. World Resources 1988-
1989. Basic Books, New York.
WRI (World Resources Institute), World
Bank, and UNDP (United Nations
Development Programme). 1985. Tropical
Forests: A Call for Action. WRI, Washington,
D.C.
Zimmerman, M., and M. Reid. 1988. Fact
Sheet: Energy and Efficiency in Industry and
Commerce. Alliance to Save Energy,
Washington, D.C.
Vn-62
-------
CHAPTER VIII
INTERNATIONAL COOPERATION TO REDUCE
GREENHOUSE GAS EMISSIONS
FINDINGS
• Most of the expected growth in
greenhouse gas emissions is from other
countries, particularly developing countries,
the USSR, and Eastern Europe. Efforts to
promote international solutions are therefore
essential to achieve global reductions in
greenhouse gas emissions.
• Technological solutions and policy
strategies for the U.S. and other western
industrialized nations may not be equally
applicable in other parts of the world.
Differences in economic development, energy
resources, and economic systems must be
addressed when devising international
strategies to reduce greenhouse gas emissions.
• U.S. leadership has historically made
important contributions to other important
international environmental agreements, such
as the Montreal Protocol on Substances that
Deplete the Ozone Layer, the London
Amendments to the Protocol, and the Tropical
Forestry Action Plan. In the future, U.S.
leadership could promote international
cooperation to reduce greenhouse gas
emissions worldwide. Successful U.S. efforts
to reduce national emissions may encourage
similar actions by other nations and could
serve as a valuable demonstration that
reductions are feasible.
• Developing countries could reduce the
expected increase in greenhouse gas emissions
consistent with economic development and
other environmental and social goals. Energy
efficiency improvements are already essential
to reduce capital requirements for the power
sector, and efforts to halt tropical
deforestation will provide many long-run
economic and environmental benefits. The
U.S. can promote desirable changes in energy
and environmental policy in developing
countries through judicious use of its bilateral
aid programs and its influence on loans
extended by multilateral development banks.
• The Soviet Union and Eastern
European nations are and will continue to be
important contributors to greenhouse gas
emissions. The absence of market pricing has
hindered efforts to reduce the energy intensity
of these economies, but their governments
have shown increasing interest in curbing
energy use.
• There have already been some
important first steps toward building a
framework for international cooperation to
reduce the risks of climate change. In
November 1988, an Intergovernmental Panel
on Climate Change (IPCC) was initiated under
the auspices of two United Nations (U.N.)
agencies, the United Nations Environment
Programme and the World Meteorological
Organization, to assess the science, impacts,
and policy responses to global warming and to
submit a report by August 1990, prior to the
Second World Climate Congress, which was
held in November 1990. The United States
chairs the Response Strategies Working
Group. The IPCC submitted its report in the
Fall of 1990. Also, in February 1991 the first
meeting of the Intergovernmental Negotiating
Committee for a Framework Convention on
Climate Change, convened by the U.N.
General Assembly, was held in Chantilly,
Virginia.
vni-i
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Policy Options for Stabilizing Global Climate
INTRODUCTION
The greenhouse problem requires
international strategies to promote global
cooperation. An important first step has been
taken in this direction under the auspices of
the United Nations Environment Programme
(UNEP) and the V/orld Meteorological
Organization (WMO). In 1988 these
organizations helped organize an
Intergovernmental Panel on Climate Change
(IPCC) to review the science, impacts, and
response strategies associated with climate
change. The U.S., Soviet Union, China, Japan,
and many other leading nations agreed to
participate. Three panels were organized to
consider scientific issues (chaired by the
United Kingdom), effects of climate change
(chaired by the Soviet Union), and policy
responses (chaired by the U.S.). The first
meetings occurred in early 1989, and the final
report was submitted in time for the Second
World Climate Congress, held in November
1990.
There is an important relationship
between the domestic policies discussed in
Chapter VII and the evolution of international
cooperation that is the focus of this chapter.
U.S. actions can promote further international
cooperation and complementary strategies by
other countries. Consideration of the
domestic policies reviewed in this report
demonstrates that the U.S. no longer views the
problem as only a scientific concern. Further
analysis and consideration of such policies may
also convince other nations of the seriousness
of the risks and the need for action. U.S.
leadership in the United Nations (U.N.) and
other international forums can have a major
impact on the evolution of international
understanding and ultimately agreements, as
illustrated by the Montreal Protocol on
Substances that Deplete the Ozone Layer.
Special efforts will be necessary to limit
the growth in greenhouse gas emissions from
developing countries while addressing their
need for energy and economic growth.
Solutions to the problems of climate change
may be linked to other development needs,
such as capital shortages and increased
recognition of local environmental problems.
U.S. bilateral assistance programs and
participation in multilateral development
banks (MDBs) provide an opportunity to
promote policies that reduce greenhouse gas
emissions in developing countries consistent
with their development needs. Programs
should be designed to increase developing
countries' stakes in contributing to this global
effort, for example, through debt swaps,
afforestation programs, and technology
transfer agreements that are linked to
reductions in greenhouse gas emissions.
The need for international cooperation
has already been recognized, and some
important first steps have been taken to
establish a framework for international
cooperation on the scientific aspects of global
warming and to discuss policy responses.
THE CONTEXT FOR POLICIES
INFLUENCING GREENHOUSE GAS
EMISSIONS IN DEVELOPING
COUNTRIES
Because of faster growth rates and
greater needs for basic materials, the
developing countries will contribute an
increasing share of greenhouse gas emissions
(see Figure 8-1). Any global effort'to reduce
emissions will therefore have to take into
account the very different needs, resources,
and other constraints in the developing
countries, particularly their need to grow
economically so that they can meet basic
human needs despite their limited capital
resources for meeting development objectives.
These issues will have to be addressed in the
international forums that are being created
specifically to deal with the greenhouse
problem. However, the U.S. can also address
these concerns in the short term by
recognizing the link between emissions of
greenhouse gases and the investment choices
encouraged by bilateral aid and lending by
multilateral development banks. Before we
discuss these options, however, it is useful to
examine the different context within which
developing countries operate to get an idea of
the energy and environmental issues they face
and the priority of their concerns.
The context for policy formation in
developing countries often differs substantially
from that in the industrialized countries,
reflecting differences in political and economic
systems, resources, and societal needs. Some
VIII-2
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Chapter VIII: International Cooperation
FIGURE 8-1
Greenhouse Gas Emissions by Region
(RCW Scenario)
C02
o
•
30
25
20 —
15 —
10 —
CH4
•
\
•
1000
800
600 —
400 —
200
1985 2000
2026
2060
2076
Year
Other
Developing
China &
CP Asia
USSR 4
'E. Europe
Rest of OECD
United States
Other
Developing
China &
CP Asia
USSR*.
E. Europe
Rest of OECD
United States
2100
* RCW = Rapidly Changing World. See Chapter VI for a description of this and other scenarios
used to make projections about future levels of greenhouse gas emissions.
Note: These graphs do not include natural emissions.
YIII-3
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Policy Options for Stabilizing Global Climate
of the major issues associated with the
formulation and implementation of energy and
related environmental policies in developing
countries include socioeconomic equity,
financial viability, institutional structure and
management of enterprises, and the
burgeoning awareness of environmental
concerns. Our understanding of these issues
is essential to developing emissions reduction
policies that are relevant to developing
countries and that take into account the
conditions existing in these countries and the
issues that are of most concern to them.
Economic Development and Energy Use
Developing countries are a much more
diverse group than the member countries of
the Organization for Economic Cooperation
and Development (OECD). They range from
some of the poorest nations, such as
Bangladesh and Ethiopia, to some of the
richest ones, such as Saudi Arabia and
Singapore. Their annual income per capita
varies from S150 to S7000 (World Bank, 1987).
The group includes oil and natural gas
exporters and importers at different levels of
per capita income. Their economies vary from
a centrally-planned one like China to more
market-oriented ones like Brazil and South
Korea. Each country has a different mix of
institutions engaged in the supply of energy,
reflecting different degrees of governmental
control and foreign involvement. Table 8-1
shows energy use data from selected countries.
Equity concerns play a strong role in the
pricing of fuels. Preferential electricity tariffs
for residential customers are often
accompanied by even lower tariffs for
agricultural ones. (This is not unlike the
situation in some developed countries where
low "lifeline rates" are charged for small
amounts of electricity consumption.) On the
other hand, gasoline prices in developing
countries are typically set high relative to
world market prices, since gasoline is used in
cars that are primarily owned by the rich.
Petroleum taxes represent an important
instrument of social policy; they can be
adjusted to cushion the impact of energy price
increases or to maintain higher prices when
international prices decline.
The price of coal in India and China,
the two major developing countries that rely
heavily on coal, is subsidized, and the amount
of the subsidies varies by sector. In China,
since the coal price is too low, the government
provides subsidies, in amounts from 10 to 27
yuan/ton (or S2.70 to S7.20/ton), to coal
producers in order to encourage them to
produce more coal (Dadi, 1988). Similarly,
despite continual increases in the price of coal
in India, Coal India Limited (CIL), an Indian
government enterprise that produces over 90%
of the country's coal, incurred losses
equivalent to more than S8/ton (Hindu Survey,
1988).
Industrial energy use forms a major
segment of overall energy use in the
developing countries. Because the industries
are generally less modern than their
counterparts in the developed countries, they
tend to be less energy-efficient as well (see
Table 8-2). According to the U.S. Agency for
International Development (U.S. AID),
developing countries can typically save 5-15%
of commercial fuel through low-cost measures
and up to 25% through cost-effective retrofits
(U.S. AID, 1988a). A recent detailed study of
the potential for cost-effective electricity
conservation in Brazil documented potential
savings equal to more than a fourth of
currently forecasted needs (Geller et al., 1988;
see Table 8-3). The management of
government-controlled industries is often
inefficient, as a comparison of similar products
produced by government-controlled and
private-sector industries, even in the same
country, will show.
Given adequate capital and technical
knowledge, industries in a developing country
can operate just as efficiently as comparable
ones in a developed country (Schipper, 1981).
For example, multinational companies
operating in developing countries often use
about the same amount of energy per unit of
output as the company's comparable plants in
the developed countries.
The energy sector is typically owned and
operated by government-controlled
corporations in the poorer developing
countries. These corporations often have little
VIII-4
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Chapter VIII: International Cooperation
TABLE 8-1
1985 Population and Energy Use Data from Selected Countries
ELECTRICITY
Country
China
India
Brazil
Indonesia
Korea
Nigeria
Mexico
Egypt
Kenya
U.S.
Population3
(Millions)
1,045.3
750.9
134.6
165.2
41.1
92.0
75.6
47.2
20.4
239.3
GDP
(1985
U.S.S
Billions)
265.53
177.10
155.45
86.20
86.80
48.70
146.87
30.06
5.02
3,946.60
GDP/
Capita
(1985
U.S.S)
254
236
1,155
522
2,112
529
1,943
637
246
16,492
Sales
Per
Capita
(kWh)
365
166
1,283
74
1,234
68
929
471
107
9,719
Growth
Rate
(1970-85)
(%)
6.7
7.2
10.2
14.3
13.4
10.7
7.9
9.9
10.9
3.5
MODERN FUELSb
Per Growth
Capita Rate
(GJ) (1970-85)
(%)
21.25
7.91
35.13
8.57
57.03
7.13
62.72
23.68
2.31
325.76
5.2
5.5
7.3
11.2
8.9
16.4
7.2
8.7
-3.3
0.7
Biomass
Use Per
Capita
(GJ)
8.83
5.79
16.16
9.28
2.07
10.92
5.28
NA
NA
11.46
DOMINANT FUEL
Total
Coal
Coal
Hydro
Oil
Oil
Oil
Oil
Oil
Oil
Oil
%c
79
56
46
71
49
80
58
72
93
42
a Based on several sources.
b Modern fuels expressed as fossil-fuel equivalent assuming conversion efficiency of 10,000 Btu/kWh.
c Dominant fuel as a percentage of modern fuels (excluding most biomass).
Source: LBL, 1988.
VIII-5
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Policy Options for Stabilizing Global Climate
TABLE 8-2
Efficiency of Energy Use in Developing Countries: 1984-85
Country/Region
North America13
Canada
United States
Average
Oceaniab
New Zealand
Australia
Japan
Average
Europe13
Luxembourg
Turkey
Portugal
Greece
Ireland
Norway
Sweden
Belgium
Netherlands
United Kingdom
Austria
Italy
Spain
Germany
Denmark
Switzerland
Average
Energy Use/
Unit of GDP3
0.80
0.61
0.62
0.50
0.45
0.29
0.32
0.65
0.56
0.49
0.44
0.44
0.40
0.40
0.36
0.36
0.35
0.33
0.33
0.32
0.31
0.27
0.25
0.34
Average Annual
Growth Rate (%)
-0.5
-2.2
-2.1
+ 1.8
-0.5
-3.1
-2.5
-4.9
-1.0
+ 1.5
+ 1.2
-1.4
-1.4
-0.6
-2.2
-1.7
-2.0
-1.2
-1.8
+0.3
-1.7
-1.7
+0.3
-1.4
VIII-6
-------
Chapter VIII: International Cooperation
TABLE 8-2 (continued)
Efficiency of Energy Use in Developing Countries: 1984-85
Country/Region
Asiac
People's Republic of China
India
Pakistan
Taiwan
Thailand
Malaysia
Indonesia
Philippines
Bangladesh
Average
Latin America0
Venezuela
Brazil
Mexico
Argentina
Average
West Africad
Senegal
Morocco
Nigeria
Cote d'lvoire
Average
Energy Use/
Unit of GDP3
1.40
0.79
0.64
0.62
0.38
0.36
0.35
0.35
0.27
0.97
1.40
0.68
0.56
0.29
0.57
0.49
0.27
0.18
0.13
0.20
Average Annual
Growth Rate (%)
-1.3
+ 1.4
4-4.2
+0.2
-0.8
+0.3
+3.3
-2.7
NA
+0.5
+4.6
+2.1
+2.2
+ 1.8
+2.7
+3.6
0.0
+9.4
+2.8
+6.5
a Gross domestic product metric tons of oil equivalent per $1,000 U.S. (constant 1980 dollars).
b Average annual growth rate for 1973-85; 1985 data.
c Average annual growth rate for 1973-84; 1984 data.
d Average annual growth rate for 1977-84; 1984 data.
NA = Not available.
Sources: Sathaye et al., 1987; OECD/IEA, 1987.
VIII-7
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Policy Options for Stabilizing Global Climate
TABLE 8-3
Potential for Electricity Conservation in Brazil
End-Use
Application
Current
forecast
(twh)
Savings
potential
Savings
potential
(twh)
Industrial motors
Domestic refrigerators
Domestic lighting
Commercial motors
Commercial lighting
Street lighting
Total
164.8
24.7
16.5
28.0
25.0
16.8
275.8
20
60
50
20
60
40
33.0
14.8
8.2
5.6
15.0
6.7
83.3
Source: Geller et al., 1988.
incentive to invest in reducing their energy
costs because they are protected from
competition and rewarded more by measures
of production than efficiency of service. This
problem is compounded by regulated prices
that are often not high enough to pay for the
companies' expenses and non-payment or
delayed payment for fuels purchased from
other government companies.
Oil Imports, Capital Shortages, and Energy
Efficiency
Most developing countries are largely
dependent on imports for commercial fuels.
During periods of high oil prices, import costs
have resulted in serious hardship in these
countries. In some countries oil import costs
exceeded 25% of export earnings in 1984 and
much more than that in earlier years (see
Table 8-4). Future increases in world oil
prices may have an even more adverse impact
because of the rapid growth in the
transportation sector in some countries.
A shortage of capital for large
development projects is pervasive in
developing country economies and increasingly
a constraint on the energy sector. Energy
investments in developing countries require a
high percentage of available capital (see Table
8-5). The World Bank and, more recently,
U.S. AID have reviewed the magnitude of
energy shortfalls in developing countries and
its implications for economic development
(World Bank, 1983; U.S. AID, 1988b; see
Table 8-6). U.S. AID estimates that in a
current-trends scenario, U.S. AlD-assisted
countries would need to spend over S2.6
trillion for the power sector by the year 2008
to meet projected needs. This is an average of
over $125 billion per year, compared with the
estimated $50 to $60 billion currently being
spent annually. Since current expenditures
already consume one-fourth or more of
development budgets, this is potentially a
serious constraint on economic development.
Aggressive conservation efforts, however, could
reduce capital needs by 40-60% (Williams,
1988; World Bank, 1983).
The added cost of more efficient
products is often cited as an obstacle to efforts
to improve efficiency in capital-short
developing countries. However, the high cost
of capital may favor investments in efficiency
relative to investments in long lead-time
supply projects, such as construction of new
powerplants. Because efficiency investments
pay off much more quickly, their economic
VIII-8
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Chapter VIII: International Cooperation
TABLE 8-4
Net Oil Imports and Their Relation to Export Earnings
for Selected Developing Countries, 1973-1984
Net Oil Imports
(million U.S. dollars, current prices)
1973
1974
1977
1979
1981
1983
Imports as Percentage of Export Earnings
1984
Kenya
Zambia
Thailand
Korea
Philippines
Brazil
Argentina
Jamaica
India
Bangladesh
Tanzania
1
11
173
276
166
986
83
71
308
-
47
27
30
510
967
570
3,230
328
193
1,170
92
153
57
53
806
1,930
859
4,200
338
242
1,750
172
102
113
72
1,150
3,100
1,120
6,920
351
309
3,067
247
174
316
63
2,170
6,380
2,080
11,720
302
490
-
509
306
208
274
1,740
5,580
1,740
8,890
-
-
-
286
175
219
454
1,480
5,770
1,470
7,470
-
-
-
314
156
Kenya
Zambia
Thailand
Korea
Philippines
Brazil
Argentina
Jamaica
India
Bangladesh
Tanzania
0.1
2.2
11.1
8.6
8.8
15.9
2.5
18.1
10.6
-
12.8
4.1
5.1
20.9
21.7
20.9
40.7
8.3
27.3
29.7
26.5
38.0
4.8
9.5
23.1
19.2
27.5
34.7
6.0
32.4
27.5
36.1
20.2
10.2
8.2
21.6
20.6
24.4
45.4
4.5
37.7
39.3
37.4
34.8
26.9
7.8
30.9
30.0
36.8
50.4
3.3
50.3
-
64.6
52.7
21.2
20.8
27.3
22.8
35.4
40.6
-
-
-
39.4
47.0
20.3
21.4
20.0
19.7
27.8
27.7
-
-
-
33.6
42.3
Source: IMF, 1985, in Goldemberg et al., 1987.
VIII-9
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Policy Options for Stabilizing Global Climate
TABLE 8-5
Annual Investment in Energy Supply As a Percent of
Annual Total Public Investment (Early 1980s)
Under 20%
20-30%
30-40%
Source: Munasinghe and Saunders, 1986.
Over 40%
Egypt
Ethiopia
Ghana
Nigeria
Sudan
Botswana
China
Costa Rica
Liberia
Nepal
Ecuador
India
Pakistan
Philippines
Turkey
Argentina
Brazil
Colombia
Korea
Mexico
TABLE 8-6
World Bank Estimate of Capital Requirements for Commercial Energy
In Developing Countries, 1982-1992
(billions of dollars)
Middle Income
Low Income Oil Importers
Oil Exporters
All Countries
Total Required Capital
Electricity
Oil and Gas
Coal
Total
17.6
12.1
5.6
35.3
35.9
16.7
2.8
55.4
13.1
40.0
0.6
53.7
66.6
68.8
9.0
144.4
Foreign Exchange Requirements
Electricity
Oil and Gas
Coal
Total
3.6
4.9
1.1
9.6
11.4
5.9
1.0
18.3
7.2
25.4
0.3
32.9
22.2
36.2
2.4
71.2*
* Includes S10.4 billion for refineries that is not included in country group or individual fuel totals.
Source: World Bank, 1983.
VIIMO
-------
Chapter VIII: International Cooperation
advantage increases with interest rates (Geller
et al., 1988). However, this comparison is not
visible to consumers since they do not pay the
marginal cost of new energy supplies, and
energy and utility companies may have no
interest in efficiency for institutional reasons
(Goldemberg et al., 1987).
Greenhouse Gas Emissions and Technology
Transfer
The transfer of state-of-the-art
technology will be necessary to significantly
reduce commercial energy use in developing
countries. However, there are many obstacles
to the development and dissemination of such
technologies from industrialized countries to
potential competitors in developing countries.
Even when state-of-the-art technology is
made available, developing-country
governments or manufacturers may be
reluctant to accept it. Such technology will
carry a higher capital cost and may produce
products of higher quality only at a higher
price. Heavily indebted developing countries
may not be in a position to secure the
additional capital needed for state-of-the-art
technology. Developing-country markets tend
to be more price sensitive given the lower
discretionary income enjoyed by consumers in
these countries. A program to reduce the cost
of capital for more efficient plants and
equipment, and another to induce consumers
to purchase products with higher first costs yet
lower life-cycle costs, are essential to
encourage developing-country consumers to
acquire and use state-of-the-art technology.
Most developing countries need
technologies that take advantage of abundant
but unskilled labor and that minimize the need
for capital. Many have more biomass
resources than fossil fuels (Goldemberg et al.,
1987; Williams, 1988). Improved versions of
some low-cost technologies no longer used in
the industrialized countries, such as wood-
burning cookstoves, are therefore a high
priority. Developing countries are still rapidly
increasing their consumption of basic
materials, whereas such consumption is being
replaced by high-value-added fabrication and
finishing activities in industrialized countries
(Williams et al., 1987). This fact implies
substantial differences in research priorities,
but there are few institutions and much less
money devoted to meeting their needs. The
tendency, reinforced by the risk-averse policies
of multilateral banks, is to make do with what
is tried and true in the industrialized nations.
A recent study of energy research and
development (R&D) by the Oak Ridge
National Laboratory concluded that U.S.
support for R&D should include some efforts
aimed specifically at the needs of developing
countries, in recognition of differences in their
resources and infrastructure. The study notes
that such expenditures may be in the best
interests of the U.S. as a contribution to
reduce the buildup of greenhouse gases.
Additional potential benefits include reducing
the expected increased stress on oil markets
that would occur with higher demand and the
creation of a significant export market for U.S.
manufacturers. The study proposes additional
annual expenditures of between $100 million
and $200 million as part of a larger
international effort (Fulkerson et al., 1989).
The potential for developing new export
markets would become even more important if
the U.S. exports of coal (worth $3.5 billion in
1987) were reduced. The Committee on
Renewable Energy Commerce and Trade
(CORECT) may be a model for integrating
technology transfer efforts with export
promotion activities. The Committee was
created by an act of Congress in 1983, serves
as a vehicle for bringing together developing
country officials, donor agencies, and U.S.
renewable energy firms, and addresses both
development needs and potential export
markets. CORECT has organized trade shows,
analyzed trade barriers, brought potential
foreign buyers to the U.S. to see operating
systems first-hand, and recommended measures
to improve access to financing.
STRATEGIES FOR REDUCING
GREENHOUSE GAS EMISSIONS
Studies of future energy use in
developing countries indicate that the
industrial sector and power generation sector
will retain their large share of total energy
demand (Sathaye et al., 1989). However, the
mix of fuels is less certain. A slower growth
rate would mean continued use of traditional,
and therefore, biomass fuels. On the other
VIII-11
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Policy Options for Stabilizing Global Climate
hand, faster economic growth would reduce
hiomass consumption, but increase oil
consumption as individuals with higher
incomes would demand greater mobility and,
consequently, more petroleum products.
Strategies to reduce carbon dioxide (CO2)
emissions will therefore depend on the rate of
economic growth in the developing countries.
Energy-pricing reform is essential to
promote efficient use of fuels; existing
subsidies and price controls are major barriers
to investments in energy conservation.
However, as discussed below, the short-term
result may not be to reduce CO2 emissions
since many countries have substantial unmet
energy needs that would utilize any supplies
made available by efficiency improvements.
Coal is also the least expensive fuel other than
biomass in most developing countries, and
market pricing may lead to increasing the
share of energy from this carbon-intensive
source.
U.S. AID, the World Bank, and other
development agencies have actively promoted
energy-pricing reform in developing countries.
However, a recent U.S. AID analysis concludes
that such efforts have often failed because of
fears that reforms will be economically and
politically destabilizing. Effective pricing
reform, however, does not necessarily require
radical reorganization of economies. Hungary,
for example, has achieved substantial
improvements in agricultural productivity by
creating economic incentives while maintaining
a primary role for cooperatives (Chandler,
1986). Further study may help identify ways to
overcome this problem, but a realistic
expectation may be gradual price increases and
structural reform to reduce future interference
in energy markets (U.S. AID, 1988a).
Improvements in energy efficiency in
developing countries may not lead to emission
reductions in absolute terms because the
energy made available may meet unmet needs
and pent-up demands. This is consistent with
efforts to promote economic growth but
implies that even highly successful
conservation programs may not prevent
substantial emissions growth in these
countries. In the long run, however, there will
be less emissions than would be the case with
continued inefficient use of energy. Similarly,
pricing reform may not always lead to reduced
emissions of greenhouse gases. For example,
removing subsidies for kerosene and liquified
petroleum gas may push some consumers back
to inefficient use of traditional fuels (Leach,
1987, 1988), This may promote deforestation
and a net increase in CO2 emissions if the
only alternative is wood from freshly felled
trees. Continued subsidies for modern
cooking fuels for some transition period might
be desirable to reduce CO2 emissions.
Several financial strategies can promote
improved industrial efficiency by increasing the
capital available for desired investments. One
traditional financial approach is to allocate
capital for designated purposes, such as
improving energy efficiency, sometimes at
subsidized rates. Power sector loans also
could be tied to stringent conservation targets
that involve utilities in promoting
conservation, as is currently done in some
industrialized countries. Governments also
sometimes deliberately seek to increase
competition within the industrial sector,
sometimes inviting foreign collaboration, as a
way of forcing companies to increase capital
spending.
As capital becomes expensive,
governments have begun to tap into private
capital markets by floating bonds in targeted
funds (e.g., the Korean, Taiwanese, or Indian
funds introduced in international markets).
Domestic markets are being tapped as well in
similar ways. Governments could target
private capital for proven technologies and
government funds for investment in novel, yet
economic, energy conservation schemes
specially targeted to reduce CO2 emissions.
Industrialized countries may help by inducing
banks to reduce the interest charged for
investment targeted for CO2 emissions
abatement strategies.
Another possible innovative approach is
for governments to allow the release of so-
called "black money" funds locked away by
private individuals to evade taxes, if directed to
investments for CO2 emissions abatement. In
some countries black money may account for
30-40% of total gross domestic product
(Woodall, 1988). Placing this money in
circulation would mean that governments
would have to forego or reduce taxes on these
VIIM2
-------
Chapter VIII: International Cooperation
would have to forego or reduce taxes on these
funds, in effect conceding that they would not
collect them anyway without substantial
increase in enforcement.
International Lending and Bilateral Aid
The U.S. can help developing countries
reduce their greenhouse gas emissions through
its foreign aid programs and contributions to
the World Bank and other MDBs. Although
all such programs (U.S. and foreign) address
only a small percentage of total investment in
developing countries, they can exert
disproportionate influence because they
leverage much greater amounts of funds and
certify the financial merit of particular
technologies and projects.
U.S. Bilateral Assistance Programs
Most U.S. non-military bilateral
assistance is administered by U.S. AID,
including energy- and forestry-related
assistance. U.S. AID has attempted to
improve its sensitivity to environmental
concerns in recent years and estimates that it
now spends over $100 million for activities
aimed at conserving natural resources (U.S.
AID, 1987). The Agency has expanded the
number of environmental professionals and
established an Office of Forestry,
Environment, and Natural Resources.
Most U.S. AID support for energy is
provided through regional and national
programs, although a few projects are funded
through a central Office of Energy. Some
coordination is also encouraged by an Agency
Sector Council for Energy and Natural
Resources. Energy-related funding for the
past five years has averaged slightly less than
$200 million per year; the fiscal year (FY)
1986 budget included $254 million for energy
projects in 23 countries, of which S180 million
was spent for electric power (U.S. AID,
1988a).
U.S. AID has funded some analysis of
promising projects for biomass fuels that
indicate the possibilities for redirecting some
bilateral assistance to more effectively promote
rational energy planning and development and
adoption of improved technology. The Multi-
Agency Working Group on Power Sector
Innovation, coordinated by U.S. AID'S Office
of Energy, was organized in 1987 to promote
cooperation among international institutions
involved in power sector development. U.S.
AID has proposed using this group and the
International Development Assistance
Committee to focus greater attention on the
energy/environment relationship (U.S. AID,
1988b). Proposals have also been made to
expand the scope of the Consultative Group
on International Agricultural Research -- a
highly successful international consortium of
lenders for improving crop yields and
production in developing countries -- to
encompass agroforestry, bioenergy, and
tropical ecology.
Current U.S. AID priorities are to
identify projects that utilize indigenous energy
resources and that have the greatest potential
for replication. U.S. AID will attempt to
broker technical and financial assistance for
promising projects, emphasizing private sector
participation. U.S. AID'S funding priorities
are also shifting toward the poorest nations,
which generally implies countries with lower
energy growth rates, although sometimes high
rates of deforestation (Gray et al., 1988). U.S.
AID is proposing to give greater attention to
the environmental implications of the energy
sector.
U.S. AID has steadily upgraded its
commitment to forestry in recent years, from
about $20 million in 1979 to $56.2 million for
146 projects in FY 1987 (U.S. AID, 1987;
Stowe, 1987; see Table 8-7). Agroforestry has
been emphasized along with training and
institution building. A large amount of
support has been given to tree planting and
forestry-related activities through the Food for
Peace Program (PL 480). The program is
responsible for direct tree planting on an
estimated 1.5 million hectares in 53 countries
during the early 1980s (Joyce and Burwell,
1985) and for 38 tree-planting projects in 23
countries in FY 1987, mostly in Africa (U.S.
AID, 1988c). Combining bilateral and food-
aid assistance, U.S. AID'S tropical forestry
programs exceeded $82 million in FY 1987.
U.S. AID has also been a strong supporter of
the Tropical Forestry Action Plan.
If the U.S. seeks to promote reductions
in greenhouse gas emissions in developing
YIII-13
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Policy Options for Stabilizing Global Climate
TABLE 8-7
U.S. AID Forestry Expenditures by Region
Number of Number of
Countries Projects
With Active
Region Projects in FY 1987
Africa 23 45
Asia/Near East 11 39
Latin America/
Caribbean 12 46
Central Bureaus NA 16
Totals 46 146
LOP
Forestry
Number of Number Obligations3
New Starts Completed (in $1,000)
3 3 95,150
1 6 273,212
3 8 140,241
0 0 78,103
7 17 5586,706
FY 1987
Forestry
Obligationsb
(in $1,000)
13,960
17,337
17,398
7,488
556,183
a LOP = Life of Project. Many forestry projects are components of larger natural resource and
agricultural projects. To determine the forestry component, a percentage of the total LOP funding was
estimated for significant forestry activities based on judgments made by U.S. AID staff and contractors.
Projects can receive funding obligations at any time during the life of the project.
b To arrive at estimates for FY 1987 forestry obligations, the total 1987 LOP obligations were multiplied
by the percentage estimated for forestry activities.
Source: U.S. AID, 1988c.
YIII-14
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Chapter VIII: International Cooperation
countries, U.S. AID would logically play a
major role. Section 106 of the Foreign
Assistance Act already authorizes U.S. AID
programs to promote renewable energy and
improvements in energy efficiency. Several
proposals have been made for greatly
expanded efforts in this area. A working
group of the Atlantic Council of the United
States and the Member Committee of the U.S.
World Energy Conference recommended
expanding U.S. AID's energy assistance
programs to promote greater private-sector
investment. They suggest using the revolving
loan fund and grant program administered by
the Bureau for Private Enterprise to make
energy loans; its current priority is agri-
business (Gray et al., 1988).
Another recent study by the American
Council for an Energy-Efficient Economy
proposes that U.S. AID'S energy budget be
increased to S50-S100 million per year. The
authors would redirect aid programs away
from support of specific projects in favor of
building the capabilities of individuals and
institutions within developing nations. They
conclude that increasing private-sector
involvement should be a high priority, noting
that U.S. companies could be encouraged to
market energy-efficient technologies with the
assistance of the Overseas Private Investment
Corporation, the Export-Import Bank, and the
Trade and Development Program (Chandler et
al., 1988).
U.S. AID is not the only U.S. agency
involved in bilateral assistance. For example,
both the Department of Agriculture and the
Peace Corps support international cooperative
forestry programs. The former has an Office
of International Cooperation and
Development exclusively devoted to
international activities and also funds some
research (Stowe, 1987).
Policies and Programs of Multilateral
Development Banks
The U.S. contributes over $1 billion to
MDBs annually, an amount that leverages
many times as much actual borrowing through
co-financing and other arrangements. Much of
the activity of these banks is directly or
indirectly related to greenhouse gas emissions
through loans for energy projects, forestry, and
agriculture (see Table 8-8). U.S. influence on
these institutions is substantial, though they
are not controlled by the U.S. government.
Voting on each bank's board is through a
board of directors whose membership is
proportional to the size of contributions,
giving the U.S. roughly 15% in the World
Bank (World Bank, 1987). (U.S.
recommendations on specific loans, however,
have been outvoted.) The U.S. is the largest
contributor to the World Bank, and the World
Bank president has traditionally been an
American. Congress has directed use of the
U.S. "voice and vote" to promote several
selected policies, such as human rights
concerns and the use of "light capital
technologies" (22 U.S. Code Sec. 262f and
262d).
The MDBs are able to influence the
policies of developing countries to some
degree, because loans and aid tend to be
offered on relatively favorable terms and
because bank support can help countries
obtain credit from lenders. MDB lending has
taken on even greater significance as the debt
burden and capital requirements of developing
countries have grown enormously in recent
years. This influence has been used in ways
that have had both positive and negative
impacts on the energy and forestry sectors.
For example, the World Bank has been a
strong advocate of energy-pricing reforms
(World Bank, 1983; Goldemberg et al., 1988).
However, studies have also documented
numerous MDB projects that lead directly and
indirectly to deforestation, including roads,
dams, tree crop plantations, and agricultural
settlements (Repetto, 1988).
About one-fourth of World Bank
lending, nearly $4 billion, goes to energy-
related projects. The rate for other MDBs
ranges from 9% by the African Development
Bank to 34% for the Asian Development Bank
(Gray et al., 1988). Traditionally, a majority
of this funding has gone for development of
very large power projects (see Table 8-9). By
one estimate, over 90% of multilateral and
bilateral energy assistance has been for large
systems for the generation, transmission, and
distribution of electricity. New and renewable
energy sources have received about 3%, and
VIII-15
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Policy Options for Stabilizing Global Climate
TABLE 8-8
Gross Disbursements of Development Banks in
Forestry Projects in 1986-1988
(million U.S. dollars)
BANK
World Bank
African Development Bank
Asian Development Bank
Inter American Development Bank
TOTAL
1986
122.3
2.7
9.0
8.5
142.5
1987
127.0
5.0
11.6
7.5
151.1
1988
129.8
1.0*
75.0
6.8
212.6
* Rough Estimate
Source: FAO, 1989.
TABLE 8-9
World Bank Energy Sector Loans in 1987
(million U.S. dollars)
Oil/gas/coal
Hydroelectric
Total
Eastern &
Southern
Africa
20.0
63.0
83.0
Western
Africa
15.0
6.3
21.3
East Asia
& Pacific
0.0
684.8
684.8
South
Asia
548.0
1,312.0
1,860.0
Europe,
Middle
East &
N. Africa
0.0
527.0
527.0
Latin
America &
Caribbean
104.4
423.8
528.2
Total
687.4
3,016.9
3,704.3
Source: World Bank, 1987.
VIII-16
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Chapter VIII: International Cooperation
end-use efficiency measures less than 1% of
total energy-related loans (Goldemberg et al.,
1987; see Table 8-10).
The World Bank has had a major role
in financing energy sector expansion in the
developing countries that are growing most
rapidly and relying most heavily on fossil fuels,
including China, India, and Pakistan. Coal
resources in these countries are often
characterized by low heating values, and the
generation and distribution of electricity is
typically much less efficient than in the
industrialized countries. Bank projects,
therefore, represent a large share of carbon
emissions from developing countries.
In 1987 the World Bank announced a
general commitment to upgrade its support for
environmental analysis and programs (World
Bank, 1987). The Bank has created a new
environmental department, increased environ-
mental staff, and begun a process of preparing
environmental assessments on about 30
developing countries. Special attention is
being given to identifying regional
environmental projects in Africa. Support for
tropical forest conservation and development
has also been made a high priority; funds will
increase from $152 million in FY 1987 to $350
million in FY 1989. In September 1989, the
World Bank announced a policy to give
greater attention to the global wanning
implications of its projects, although without
indicating any change in funding priorities at
this time.
Some power sector loans have important
conservation components. For example, a
recent loan to Zimbabwe includes $44 million
to upgrade generating equipment, rehabilitate
transmission lines, and train workers to
increase total output (World Bank News, 1988).
The Bank has used its influence to support
energy-pricing reforms and the elimination of
subsidies and has funded a small number of
conservation programs through its Energy
Sector Management Assistance Program (see
Table 8-11). Some industrialization loans may
also result in substantial improvements in
energy efficiency, although such improvements
are not a primary purpose for these loans.
The Bank plans to maintain energy
loans as a relatively constant percentage of its
total lending (Gray "et al., 1988). However,
recognizing that capital needs for energy in
developing countries are expected to grow
much faster than available funding, the Bank
plans to increase its analytical, policy, and
technical advisory roles and to become more
of a catalyst for funds from non-Bank sources.
The World Bank, like U.S. AID, plans to give
more attention to private power generation
and other innovative means of financing new
power sources.
A World Bank representative at a U.S.
Environmental Protection Agency (U.S. EPA)
workshop cited several obstacles to increased
support for conservation (WRI, 1988). One is
that the Bank traditionally has found it
difficult to fund relatively small projects; ways
must be found to package them as an element
of a larger loan. (This was done in the case of
a large power loan to Brazil, which included
$2 million for analysis of conservation
opportunities.) Implementation of projects
that require actions by many individuals is
similarly perceived as difficult. Some of the
most inefficient industries may be judged
uneconomic and, therefore, inappropriate
candidates for loans. Finally, the recipient
governments have to be interested in
conservation and must possess the necessary
technical skills to implement conservation
programs.
Another problem is the availability of
proven technology suited to the needs of
developing countries. As discussed above, the
technological needs of developing countries
differ from those of industrialized countries in
many areas. However, lending criteria tend to
discourage the search for new or innovative
technologies by restricting financing to
practices that have been fully proven in
practice (Daffern, 1987). This practice reflects
an understandable desire to minimize risks,
but the effect is often to finance equipment
that is not the most efficient. Promising
alternatives that would utilize biomass and
other local resources are also neglected
because the technologies are not widely used
in the industrialized countries (Williams,
1988).
VUI-17
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Policy Options for Stabilizing Global Climate
TABLE 8-10
Energy-Related Expenditures of Multilateral and Bilateral Aid Institutions
(millions of current dollars)
Conventional
Power Generation
(Hydro, Nuclear,
Thermal),
Transmission;
Distribution;
Power Sector
Studies
Fossil Fuels
Recovery
(includes
Studies and
Training)
New and
Renewable
Energy
Sources
(includes
Geothermal,
Fuelwood)
Technical
Assistance,
Energy
Planning,
Other
Total
Energy
Aid
MULTILATERAL AID
World Bank
(FY 1978-Dec. 1978) 5,210
Inter-American Development Bank
(FY 1972-FY 1978) 2,596
Asian Development Bank
(FY 1972-FY 1978) 1,183
European Development Fund
(to May 1978) 141
U.N. Development Programme
(to Jan. 1979) 72
U.N. Center for Natural
Resources, Energy and Transport
(to Jan. 1979) 3
BILATERAL AID
French Aid
(1976-1979) 229
Canadian International Development
Agency
(1978-1979, 1979-1980) 88
German Aid
(1970-1980) 1,925
Kuwait Fund
(FY 1973-FY 1978) 437
Netherlands-Dutch Development
Cooperation
(1970-1980) 119
U.K. Overseas Devel. Admin.
(1973-1980) 146
U.S. AID
305
158
21
23
16
0
41
99
71
170
29
30
81
Source: Hoffman and Johnson, 1981, in Goldemberg et al., 1987.
VIIM8
13
48
5,686
2,758
1,204
150
137
17
280
91
2,095
536
198
149
(FY 1978-FY 1980)
Grand Total
Percentage in Each Sector
403
12,719
91
2
757
5
96
437
3
46
121
1
546
14,033
100
-------
Chapter VIII: International Cooperation
TABLE 8-11
World Bank Energy Conservation Projects:
Energy Sector Management Assistance Program
Energy Efficiency Initiatives
Industrial Energy Efficiency
Program Design and Institutional Support (Senegal, Ghana)
Energy Audits (Syria)
Training of Local Staff (Tanzania)
Power Efficiency (Many Countries)
• Design of Programs to Reduce Technical and Non-Technical Losses
• Pre-Feasibility Studies for Life Extension and Rehabilitation Projects
• Utility Organization Studies
Electricity Savings in Buildings
• Energy Efficient Building Code (Jamaica)
• Appliance Labeling (Jamaica)
Household Energy Savings
• Household Energy Strategy Studies
• Improved Cookstoves Projects
• Improved Charcoaling
Energy-Environmental Studies
• Energy Supply Options to Steel Industry in Carajas Region (Brazil)
Source: WRI, 1988.
VIII-19
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Policy Options for Stabilizing Global Climate
New Directions
The possibility of redirecting bilateral
aid and World Bank loans to facilitate energy
conservation and other strategies to reduce
greenhouse gas emissions was discussed at the
U.S. EPA workshop on developing country
issues. One proposed remedy is a shift in
Bank energy sector lending to general energy
programs as opposed to specific projects as a
way of facilitating more funding of demand-
side efforts (Goldemberg et al., 1988). This
proposal may be difficult to implement but
may receive more attention as capital
constraints lead to greater interest in
conservation.
A recent study of innovative financing
mechanisms by the World Resources Institute
(WRI) proposes that the MDBs place greater
emphasis on promoting policy reforms in
conjunction with loan agreements to protect
natural resources. The authors suggest that
the international development agencies
identify and analyze the effects of tax, tariff,
credit, and pricing policies, as well as the
terms and administration of concession
agreements, on the use of resources (Repetto,
1988).
A possible strategy for creating an
economic incentive for protection of tropical
forests is to pay affected nations an annual fee
for custodial services -- protection from
squatters and illegal development -- in
proportion to the areas under protection
(Rubinoff, 1985). Agreements to protect 100
million hectares, or roughly 10% of the
world's remaining moist tropical forest, might
cost approximately S3 billion. The status of
reserves would be monitored and payments
adjusted accordingly. In this way tropical
countries would be paid for some management
costs, reflecting some of the benefits thereby
provided to the rest of the world.
Section 119 of the Foreign Assistance
Act requires U.S. AID to prepare
environmental assessments of its major
actions, including effects on the global
environment.1 U.S. AID is also specifically
directed to consider the impacts of its
programs on tropical forests (22 CFR §
2151(a), (p); see also Stowe, 1987).
The importance of these issues is
suggested by increasing Congressional interest
(Stowe, 1987; Rich, 1985). Section 539 of
Public Law 99-591 directs the Secretary of the
Treasury to instruct U.S. Executive Directors
in each of the multilateral development banks
to take a number of steps to support
environmental reform measures and also
requires the Treasury Department to report on
progress toward these objectives (U.S.
Treasury Department, 1988). The
Department's most recent report provides
mixed reviews of the MDBs' responsiveness to
environmental concerns. As already noted, the
World Bank announced a higher priority for
environmental concerns in 1987, but the report
states that "The Bank has not moved
effectively in the area of energy conservation."
REDUCING GREENHOUSE GAS
EMISSIONS IN THE USSR AND EASTERN
EUROPE
The Soviet Union is the second largest
source of carbon dioxide emissions and
together with Eastern European nations is
likely to remain a significant contributor to
global greenhouse gas emissions in the years
to come (see Figure 8-1). The energy policies
of these countries will therefore have an
important influence on the greenhouse
problem.
The Soviet Union has enormous energy
resources, although most of them, including
half the world's accessible coal, are in
relatively remote areas of Siberia. Soviet oil
production is roughly equal to the total
production of all Middle Eastern countries
combined, and the Soviets also rank first in
gas production and third in coal production.
Coal was the dominant energy source until the
late 1950s but declined to less than 30% in
1977 with the growth in oil production (see
Table 8-12). Future plans call for increasing
reliance on natural gas and nuclear power and
renewed growth in coal use; large coal-burning
powerplants and coal slurry pipelines are now
under construction. Other Eastern European
nations, particularly Poland, East Germany,
and Czechoslovakia, are even more dependent
on coal (WRI and IIED, 1988).
VIII-20
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Chapter VIII: International Cooperation
TABLE 8-12
Energy Use in the Soviet Union and Eastern Europe
(petajoulcs)
Liquid Fuels*
Eastern Europe
Bulgaria
Czechoslovakia
East Germany
Hungary
Poland
Romania
Subtotal
U.S.S.R.
Total
1970
346
371
483
223
301
406
2,080
9,283
11,363
1980
575
668
690
424
610
688
3,655
14,770
18,425
1985
562
567
632
392
512
760
3.4Z5
14,450
17,875
Solid Fuels
1970
570
1,792
2,602
496
2,878
410
8,748
12,933
21,681
1980
615
1,861
2,523
374
4,230
689
10,292
14,440
24,732
1985
672
1,878
2,856
373
4,170
813
10,762
14,596
25,358
Gaseous Fuels'1
1970
17
79
22
121
222
971
1,432
6,611
8,043
1980
148
298
302
364
363
1,507
2,982
13,209
16,191
1985
216
330
288
393
363
1,599
3,189
19,761
22,950
Electricity0
1970
7
25
8
13
7
1
61
442
503
1980
49
40
54
27
11
47
228
811
1,039
1985
71
71
53
63
6
51
315
1,257
1,572
1970
940
2,267
3,065
853
3,408
1,788
12,321
29,270
41,591
Total
1980
1,387
2,867
3,569
1,189
5,214
2,931
17,157
43,229
60,386
1985
1,521
2,846
3,829
1,221
5,05 1
3,223
17,691
50,065
67,756
' All petroleum products and natural gas liquids.
b Natural gas, manufactured gas, coke-oven gas, and blast furnace gas.
c Hydro, nuclear, and geothermal power.
Source: WRI, 1988.
VIII-21
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Policy Options for Stabilizing Global Climate
The energy intensity of the Soviet
economy changed relatively little between 1970
and 1985, in contrast to the substantial
reductions achieved during the same period in
the U.S. and other industrialized nations. The
government has become increasingly interested
in energy conservation because of the growing
capital and fuel costs of energy production.
More than 20% of national capital investments
and 14% of primary energy resources are
consumed by the energy supply system (NAS,
1987). Oil is also a valuable export
commodity, and at current production rates
known reserves may be exhausted by the year
2000. Siberian reserves may be large, but
production costs will be much higher (WRI
and IIED, 1988).
According to recent reports,
improvements in energy efficiency continue to
be elusive in the Soviet economy (Gustafson,
1989). Industry does not pay market prices for
energy and, therefore, has little economic
incentive to conserve. However, the
government is gradually increasing fuel costs
within the Soviet economy, and recent
economic reforms may give industry greater
incentive to conserve (NAS, 1987).
Energy pricing and planning in Eastern
Europe is complicated by trade agreements
with the USSR. These countries have
provided labor for construction on Soviet oil
and gas projects in return for options to
purchase oil at a price equal to the average
price paid for Soviet oil exports over the
previous five years - a rewarding arrangement
when prices were rising, but unattractive at
recent low oil prices (WRI and IIED, 1988).
The Soviet Union and United States
currently have cooperative agreements on both
climate change and energy conservation. The
U.S.-USSR Agreement on Cooperation in the
Field of Environmental Protection lists
numerous projects on atmospheric science.
The first U.S.-USSR Symposium on Energy
Conservation was held in Moscow in June
1985, and several meetings followed, the most
recent in October 1988. A program of
cooperative research has been developed,
administered in the U.S. by the National
Academy of Sciences (NAS, 1987,1988). The
Soviet Union also has independently expressed
strong interest in global climate change
problems. At the November 1988 meeting on
global climate issues in Geneva sponsored by
WMO and UNEP, the Soviet Union agreed to
chair a panel on the effects of climate change.
U.S. LEADERSHIP TO PROMOTE
INTERNATIONAL COOPERATION
The international and bilateral
cooperation already in place has established a
solid foundation for discussion of policy
responses. However, there is much that needs
to be done before this discussion and analysis
leads to agreement on necessary actions.
Several precedents suggest that U.S. leadership
can help achieve agreement on response
strategies. Two important sources of
greenhouse gas emissions, the use of CFCs and
tropical deforestation, have already been the
subject of international agreements that should
moderate global wanning. In both cases,
action was taken for reasons largely unrelated
to climate change, but examination of the
evolution of these agreements may suggest
factors conducive to agreement on climate
change.
Restricting CFCs to Protect the Ozone Layer
In September 1987, because of growing
concern about the effect of CFCs on
stratospheric ozone, 24 nations signed an
agreement in Montreal (the Montreal
Protocol) to reduce emissions of CFCs. As of
February 1,1991, 68 countries had ratified the
Protocol. The reductions are to be
achieved through a phaseout process, which
began with a freeze (effective July 1, 1989,
six months after the Protocol went into
effect) and requires a 20% reduction of 1986
levels by July 1993. The U.S. ratified the
Montreal Protocol on April 21, 1988. U.S.
EPA issued regulations consistent with the
requirements of the Protocol on August 1,
1988 (Federal Register, 1988). The London
Amendments to the Protocol accelerate the
reduction schedule, calling for a 50%
reduction of 1986 levels by 1995 and a
total phaseout by 2000. For a description of
the terms of the Protocol and U.S.
regulations, see REGULATIONS AND
STANDARDS in Chapter VII.
Aside from its direct impact on reducing
emissions of important greenhouse gases, the
VOI-22
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Chapter VIII: International Cooperation
terms of the Protocol and the process that led
up to the agreement offer some valuable
insights for cooperation to address climate
change. Developing nations, whose current
CFC use is only about 15% of total use
worldwide, were concerned that emissions
reductions might hinder their economic
growth. Therefore, to encourage their
participation, Article 5 of the Protocol allows
countries with CFC consumption less than 0.3
kg per capita to delay compliance by ten years
as long as they do not exceed that amount
(U.S. CFC consumption was more than 1
kg/capita in 1985). The industrialized
countries also agreed to provide technical
assistance and financial aid in support of
developing countries' efforts to adopt CFC
alternatives.
The Protocol was negotiated over a two-
year period, but the foundations were laid over
a period of a decade or more. Intergovern-
mental meetings were first held in 1977 and
1978 (Stoel et al., 1980). A consensus-building
scientific process, the Coordinating Committee
on the Ozone Layer, was created by the UNEP
Governing Council in 1977. The Council
decided to convene a working group of legal
and technical experts in 1981, and the first
meeting took place in January 1982. When
agreement on proposals for action at first
proved impossible, the participants came to
an agreement in March 1985 that provided a
framework for scientific cooperation: the
Vienna Convention for Protection of the
Ozone Layer. The Convention also committed
the signatories to hold workshops and
exchange information as the basis for further
efforts to achieve a protocol.
Some of the factors that facilitated the
Protocol may provide some insight into
possible strategies for future efforts to achieve
agreements to reduce greenhouse gases
(Benedick, 1987). The existence of an
international scientific consensus report
prepared under WMO auspices, Atmospheric
Ozone 1985, helped achieve consensus about
the underlying seriousness of the problem.
The workshop process, which facilitated
informal negotiations, proved to be very
conducive to consensus building. UNEP
served a valuable organizing role and provided
a valuable objective international forum.
According to the chief U.S. negotiator,
U.S. leadership had a major role: "The treaty
as eventually signed was based upon the
structure and concept advanced by the United
States late last year" (Benedick, 1987). In
addition to governmental efforts, such as a
series of diplomatic initiatives, the U.S. role
includes industry actions to take responsibility
and to express support for the proposed
emission controls, efforts undertaken by public
interest groups to inform the public, and
threats of unilateral action and trade sanctions
by members of Congress.
International Efforts to Halt Tropical
Deforestation
There has also been substantial recent
international cooperation on the problem of
tropical deforestation. These efforts are of
substantial interest because of some of the
similar obstacles faced in solving the tropical
deforestation problem and the larger
greenhouse problem. In both cases, there is a
need for industrialized countries to help
developing countries implement policy changes
that may be costly and difficult. Mechanisms
for achieving international cooperation must
be found, substantial amounts of financial
assistance must be provided to developing
countries, and politically difficult policy
choices must be made.
The Tropical Forestry Action Plan
(TFAP) is a promising response to this
challenge (WRI, 1985; FAO, WRI, World
Bank, UNDP, 1987). TFAP was developed by
a consortium of institutions concerned about
tropical deforestation, including the U.N. Food
and Agriculture Organization (FAO), the U.N.
Development Programme (UNDP), the World
Bank, WRI, and representatives of more than
60 tropical countries. The task force that
drafted TFAP included Brazil's Secretary of
the Environment and one of India's former
Secretaries of the Environment. The broad
and highly visible sponsorship of TFAP has
helped to highlight the important benefits
provided by tropical forests and to draw
attention to their accelerating loss. Equally
important, TFAP offers the broad outlines of
a solution, including regional and functional
budget proposals. The total budget calls for
S8 billion over a five-year period.
VIII-23
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Policy Options for Stabilizing Global Climate
TFAP has become a focal point for
cooperative efforts by bilateral aid agencies
and has influenced World Bank policies (Wolf,
1988; Stowe, 1987).2 Ultimately, TFAP's
success depends on the cooperation and
support of the affected developing countries,
and many of them are preparing national
action plans and increasing national support
for reforestation (WRI and IIED, 1988),
The International Tropical Timber
Organization (ITTO) is another important
vehicle for north-south cooperation on tropical
forest management. ITTO was created by a
March 1985 agreement reached under the
auspices of the U.N. Conference on Trade and
Development, primarily as a commodity
agreement to facilitate economic use of
tropical timber; its purposes include
"expansion and diversification of international
trade," a "long-term increase in consumption,"
and greater access to international markets.
However, unlike traditional commodity
agreements, ITTO explicitly recognizes the
importance of the premise of sustainable use
to conservation efforts and management
policies. The connection has thus been made
between conservation, economic development,
and the export of resources to industrialized
countries (Wolf, 1988; Forster, 1986).
The importance given to promoting
cooperation between tropical nations and
industrialized consumers of tropical hardwoods
is evident in the ITTO organization. The
headquarters is in Japan, a very large
consumer, and the executive director is from
Malaysia, an important producer. Another
promising sign is that at the first meeting in
April 1987, Japan announced a pledge of $2
million for research on reforestation and
sustainable management.
The ITTO also acts as a forum for
addressing the link between policies of
industrial countries and resource exploitation
in developing countries. A recent WRI study
concludes that "industrial-country trade
barriers in the forest products sector have
been partially responsible for inappropriate
investments and patterns of exploitation in the
Third World Forest industries.
[Negotiations between exporting and
importing countries should reduce tariff
escalation and non-tariff barriers to processed
wood imports from the tropical countries, and
rationalize incentives to forest industries in the
Third World" (Repetto, 1988).
Looking toward the future, increased
international cooperative efforts will be
necessary if tropical deforestation is to be
halted and reversed. Professor Pedro Sanchez
of North Carolina State University has
recently outlined a possible framework for a
program to achieve this goal (Sanchez, 1988).
Dr. Sanchez notes that 12 countries account
for three-fourths of the net carbon emissions
from clearing primary forests; 10 more account
for much of the remainder (see Table 8-13).
Efforts could be made to engage the leaders of
these countries in a dialogue to discuss specific
program agreements targeted to deforestation
"hot spots," where technology transfer and
government policies would be focused - an
approach that is consistent with the TFAP's
emphasis on national planning.
Ongoing Efforts Toward International
Cooperation
Some important first steps to promote
international action have already been taken in
the last few years, and a foundation for
international cooperation now exists. Several
meetings without formal governmental status
established a basis for international scientific
cooperation. A conference on the status of
the greenhouse problem organized by UNEP,
WMO, and the International Council of
Scientific Unions was held in October 1985 in
Villach, Austria, and was attended by experts
from 29 countries, including representatives
from several U.S. agencies. Among their
conclusions were recommendations that
"scientists and policy-makers . . . begin an
active collaboration to explore the
effectiveness of alternative policies and
adjustments." In response to the
recommendations, a small task force was
created to advise on needed domestic and
international actions and to evaluate the need
for a global convention.
The government of Canada convened a
non-governmental meeting on The Changing
Atmosphere" in June 1988, which was attended
by more than 300 experts from 46 countries
and several United Nations' organizations.
The Conference Statement that came out of
VIII-24
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Chapter VIII: International Cooperation
TABLE 8-13
Countries Responsible for Largest Share
of Tropical Deforestation
Country Net Carbon Emissions in 1980
From Primary Forests
(million tons)
Brazil 207
Colombia 85
Indonesia 70
Malaysia 50
C6te d'lvoire 47
Mexico 33
Thailand 33
Peru 31
Nigeria 29
Ecuador 28
Zaire 26
Philippines 21
Source: Sanchez, 1988.
Vffl-25
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Policy Options for Stabilizing Global Climate
the meeting urges development of an Action
Plan for the Protection of the Atmosphere, in
addition to several specific proposals for
government policy, including the following:
• reduce CO2 emissions by 20% of 1988
levels by the year 2005, half by reducing energy
demand and half by changing the sources of
energy;
• direct energy R&D budgets to energy
options that would greatly reduce CO2
emissions;
• initiate development of a comprehensive
global convention as a framework for
protocols on the protection of the atmosphere;
and
• establish a World Atmosphere Fund,
financed in part by a levy on fossil-fuel
consumption in industrialized countries, to
help finance the Action Plan.
UNEP and WMO have continued their
activities since the 1985 Villach meeting. The
IPCC, organized by UNEP and WMO, met in
November 1988 with representatives from over
40 countries. Participants agreed to establish
three committees: the first, chaired by the
United Kingdom, was to assess the state of
scientific knowledge on the greenhouse issue;
the second, chaired by the Soviet Union, was
to assess social and economic effects from
global warming; and the third, chaired by the
United States, was to evaluate potential
response strategies.
In October 1989 the Response
Strategies Working Group identified an
emerging consensus on the value of a
framework climate convention to be modeled
after the Vienna Convention on the Protection
of the Ozone Layer. There was, however,
disagreement concerning the timing of such a
convention and the extent to which it should
be more specific concerning goals and
obligations, particularly provisions to address
financial aid and technology transfer. These
issues and provisions to reduce greenhouse gas
emissions may be left for later protocols as
was also done in the Vienna Convention. In
the Fall of 1990, the IPCC submitted its
report.
Outside the IPCC process, global
warming has been addressed in several other
important international forums such as the
U.N. General Assembly, which convened the
Intergovernmental Negotiating Committee for
a Framework Convention on Climate Change.
The first meeting was held in Chantilly,
Virginia in February 1991. A communique
that arose out of the July 1989 Paris meeting
of the seven heads of state of the seven largest
western economies (the "G-7") also included
statements about the need to address global
wanning. The government of the Netherlands
convened in November 1989 a conference of
environmental ministers who addressed the
problems of atmospheric pollution and
climatic change. Their statement recognized
the need to stabilize emissions of greenhouse
gases from industrialized nations "as soon as
possible, at levels to be considered by the
IPCC and the Second World Climate
Conference of November 1990," noting that
many nations support the goal of stabilizing
CO2 emissions at the latest by the year 2000
(See Box 8-1).
The U.S. also has important bilateral
cooperation with some of the other nations
that emit large amounts of greenhouse gases,
particularly the USSR and the People's
Republic of China. (These three countries
account for over 40% of the current
commitment to global warming.) U.S.-Soviet
cooperative efforts include studies of future
climates, climate studies in the Arctic,
measurements of methane and ozone change
in the polar regions, and analysis of possible
response strategies. The joint communique
released after the Reagan-Gorbachev Summit
emphasized the high level of interest in
cooperation on the greenhouse issue:
The two leaders approved a
bilateral initiative to pursue joint
studies in global climate and
environmental changes through
cooperation in areas of mutual
concern . . . there will be a
detailed study on the climate of the
future. The two sides will continue
to promote broad international
and bilateral cooperation in the
increasingly important area of
global climate and environmental
change.
VHI-26
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Chapter VIII: International Cooperation
Box 8-1. Sweden's Policy on Global Wanning
Sweden is one of the countries that is most committed to reducing its emissions of
greenhouse gases. Sweden has banned the use of CFCs by 1994, much faster than the 50%
reduction required in 1995 by the London Amendments to the Montreal Protocol, and in
1988 decided that CO2 emissions should not increase above current levels. The CO2 cap will
be particularly difficult to maintain because Sweden has also decided to phase out its
nuclear reactors -- 50% of its electricity supply -- by 2010. Increased hydropower is also
not permitted. To support the necessary research and changes in economic activities, the
government created an Environmental Charge Commission to assess possible
implementation of charges on air pollutants. In October 1989, the Commission presented
an interim report proposing that emissions of CO2 be subject to a charge amounting to 3.8
cents per kilogram of CO2. The charge would apply to ail fossil fuels, including gasoline.
Other energy taxes would be reduced. The Commission estimates that the tax would reduce
CO2 emissions by 5-10 million tons by the year 2000 relative to what they otherwise would
have been.
Source: Carding, 1989.
The U.S. and Soviet Union are also
engaged in some cooperative activities
designed to promote energy conservation. For
example, the U.S. National Academy of
Sciences and the Soviet Academy of Sciences
have a cooperative program on energy
conservation that includes some comparative
evaluation of building codes and other energy
conservation programs in addition to exchange
of technical information.
The U.S. government has also initiated
cooperative research on climate change with
the People's Republic of China, now the
world's largest user of coal. Potential areas
for cooperative research include exchange of
information and development of data on
future energy development paths, emissions
from rice fields and other sources, and
concentrations of trace gases in remote
regions.
CONCLUSION
Responding to the risks of climate
change will require unprecedented global
cooperation. Recent experience with
negotiations to protect the ozone layer, the
Tropical Forestry Action Plan, and programs
of U.S. AID'S Office of Energy and the World
Bank's Energy Sector Management Program
provides a helpful starting point. A series of
international meetings over the last two years
have built a consensus that a convention on
climate change is desirable, and the
Intergovernmental Panel on Climate Change is
playing an important role in assessing climate
science, the potential impacts of climate
change, and the available policy options. U.S.
leadership has played, and will continue to
play, an essential role.
VIII-27
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Policy Options for Stabilizing Global Climate
NOTES
1. U.S. AID procedures for preparing
environmental assessments are published in
the Code of Federal Regulations, Volume 22,
Part 216.
2. Periodic reports on progress implementing
the Action Plan are available from the TFAP
Coordinator, FAO Forestry Department, Via
delle Terme di Caracalla, 00100 Rome, Italy.
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Note:
Daniel Lashof, co-editor of Policy Options for Stabilizirg Global Climate, Raport to
Congrats (U.S. Environmental Protection Agency, Washington, D.C., 1991), is now with
the Natural Resources Defense Council.
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