230989501A
  POLICY OPTIONS FOR STABILIZING GLOBAL CLIMATE
                            \
                              DRAFT




                      REPORT TO CONGRESS
                          Executive Summary
                    Uafted States Environmental Protection Agency



                     Office of Policy, Planning, and Evaluation










                             February 1989

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POLICY OPTIONS FOR STABILIZING  GLOBAL CLIMATE
                               DRAFT

                       REPORT TO CONGRESS
                           Executive Summary


                   Editors: Daniel A. Lashof and Dennis A. Tirpak
                    United States Environmental Protection Agency

                     Office of Policy, Planning, and Evaluation




                              February 1989
                                   S  Environmental Protection

                                  B^ion 5,           IL 1670
                                  230 S.
                                  Chicago

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                   DISCLAIMER

This  draft is being  circulated for review and comment and does not
necessarily reflect the official position of the U.S. Environmental Protection
Agency. Mention of trade names does not constitute an endorsement.

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                         SUMMARY TABLE OF CONTENTS
EXECUTIVE SUMMARY








VOLUME I (Bound under separate cover)








CHAPTER I:  INTRODUCTION	   1-1



CHAPTER II: GREENHOUSE GAS TRENDS	   II-l



CHAPTER HI: CLIMATIC CHANGE	   IIM



CHAPTER IV: HUMAN ACTIVITIES AFFECTING TRACE GASES AND CLIMATE	   IV-1



CHAPTER V: THINKING ABOUT THE FUTURE	   V-l



CHAPTER VI: SENSITIVITY ANALYSES	   VI-1








VOLUME II (Bound under separate cover)








CHAPTER VII: TECHNICAL OPTIONS FOR REDUCING GREENHOUSE GAS EMISSIONS    VII-1



CHAPTER VIII: POLICY OPTIONS  	VIII-1



CHAPTER IX: INTERNATIONAL COOPERATION TO REDUCE GREENHOUSE



            GAS EMISSIONS	   IX-1

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                              DETAILED TABLE OF CONTENTS
                                   EXECUTIVE SUMMARY
INTRODUCTION	   1
       Congressional Request for Reports	   1
       Previous Studies   	   2
       Goals of this Study	   4
       Approach Used to Prepare this Report	   6
       Limitations	   9

HUMAN IMPACT ON THE  CLIMATE SYSTEM  	  11
       The Greenhouse Gas Buildup 	  11
       The Impact of Greenhouse Gases on Global Climate	  17

SCENARIOS FOR POLICY ANALYSIS	  19
       Defining Scenarios	  19
       Scenarios with Unimpeded Emissions Growth  	  22
       The Impact of Policy Choices 	  29
       Sensitivity of Results to Alternative Assumptions 	  45

EMISSIONS REDUCTION STRATEGIES BY ACTIVITY	  54
       Energy Production and Use	  56
       Industrial Activity	  66
       Changes in  Land Use	  71
       Agricultural Practices	  75

THE NEED FOR POLICY RESPONSES  	  77
       A Wide Range of Policy Choices  	  78
       The Timing of Policy Responses	  79

FINDINGS   	  83

       I.  Uncertainties regarding climatic change are large, but there is a growing consensus
              in the scientific community that significant global warming due to anthropogenic
              greenhouse gas emissions is probable over  the next century, and that rapid climatic
              change is possible	  83

       II. Measures undertaken to limit greenhouse gas emissions would decrease the magnitude
              and speed of global warming, regardless of uncertainties about the response of the
              climate system	  85

       HI.  No single country or source will contribute more than a fraction  of the greenhouse
              gases that will warm the world; any overall solution will require cooperation of many
              countries and reductions in many sources	  87

       IV.  A wide range of policy choices is available to reduce greenhouse gas emissions while
              promoting economic  development, environmental, and social goals	89
                                              111

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                       DETAILED TABLE OF CONTENTS (Continued)


VOLUME I (Bound under separate cover)


                                      CHAPTER I

                                    INTRODUCTION

INTRODUCTION	   1-2
       The Earth's Climate and Global Change	   1-2

CONGRESSIONAL REQUEST FOR REPORTS  	   1-3
       Goals of this Study	   1-4
       Report Format  	   1-5

THE GREENHOUSE GASES	   1-8
       Carbon dioxide	   1-9
       Methane	   1-9
       Nitrous oxide  	  1-12
       Chlorofluorocarbons	  1-12
       Other gases influencing composition	  1-13

PREVIOUS STUDIES	  1-13
       Estimates of the Climatic Effects of Greenhouse Gas Buildup  	  1-14
       Studies of Future CO2 Emissions  	  1-15
       Studies of the Combined Effects of Greenhouse Gas Buildup	  1-20
       Major Uncertainties	  1-22
       Conclusions From Previous Studies 	  1-23

CURRENT NATIONAL AND INTERNATIONAL ACTIVrnES	  1-26
       National Research and Policy Activities	  1-26
       International Activities	  1-27

REFERENCES	  1-29


                                      CHAPTER II

                               GREENHOUSE GAS TRENDS


FINDINGS  	   H-2

INTRODUCTION	   H-5

CARBON DIOXIDE 	   H-7
       Concentration History and Geographic  Distribution  	   II-7
              Mauna Loa	   n-8
              Ice-core Data	   II-9
              GMCC Network	  11-10
                                           IV

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                        DETAILED TABLE OF CONTENTS (Continued)

       Sources and Sinks	  11-14
              Fossil Carbon Dioxide	  11-14
              Biospheric Cycle	  11-16
              Ocean Uptake  	  11-17
       Chemical and Radiative Properties/Interactions	  11-18

METHANE 	  11-22
       Concentration History and Geographic Distribution 	  11-22
       Sources and Sinks	  11-24
       Chemical and Radiative Properties/Interactions	  11-29

NITROUS OXIDE  	  11-30
       Concentration History and Geographic Distribution 	  11-30
       Sources and Sinks	  11-32
       Chemical and Radiative Properties/Interactions	  11-35

CHLOROFLUOROCARBONS (CFCs)	  11-36
       Concentration History and Geographic Distribution 	  11-36
       Sources and Sinks	  11-37
       Chemical and Radiative Properties/Interactions	  11-39

OZONE  	  n-40
       Concentration History and Geographic Distribution 	  11-40
       Sources and Sinks	  n-43
       Chemical and Radiative Properties/Interactions	  11-44

OTHER FACTORS AFFECTING COMPOSITION	  H-45
       Global Tropospheric Chemistry	  n-46
              Carbon Monoxide	  11-47
              Nitrogen Oxides	  n-48
       Stratospheric Ozone  and Circulation  	  11-49

CONCLUSION	  H-50

REFERENCES	  11-59


                                        CHAPTER III

                                     CLIMATIC CHANGE


FINDINGS 	  m-2

INTRODUCTION	  IH-4

CLIMATIC CHANGE IN CONTEXT	  IH-6

CLIMATE FORCINGS  	  ffl-8
       Solar  Luminosity	  ffl-12
       Orbital Parameters  	  m-13
       Volcanoes	  111-13
       Surface Properties	  HI-14
       The Role of Greenhouse Gases  	  m-14

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                       DETAILED TABLE OF CONTENTS (Continued)

       Internal Variations  ...............................................   111-15

PHYSICAL CLIMATE FEEDBACKS .........................................   HI-15
       Water Vapor - Greenhouse  ..........................................   IE- 17
       Snow and Ice [[[   ffl-17
       Clouds [[[   ffl-19

BIOGEOCHEMICAL CLIMATE FEEDBACKS  ..................................   ffl-20
       Release of Methane Hydrates  ........................................   m-20
       Oceanic Change   .................................................   IH-22
             Ocean Chemistry  ...........................................   HI-23
                   Mixing  .............................................   111-23
                   Biology and Circulation ..................................  ffl-24
       Changes in Terrestrial Biota .........................................  m-25
             Vegetation Albedo  ..........................................  IQ-25
             Carbon Storage  ............................................  IH-26
             Other Terrestrial Biotic Emissions ................................  111-26
             Summary .................................................  111-27

EQUILIBRIUM CLIMATE SENSITIVITY  .....................................  ffl-28

THE RATE OF CLIMATIC CHANGE   .......................................  ffl-31

CONCLUSION [[[  ffl-35

REFERENCES [[[  ffl-37


                                      CHAPTER IV

                      HUMAN ACTIVITIES AFFECTING TRACE GASES

                                     AND CLIMATE


FINDINGS  [[[  IV-2

INTRODUCTION [[[  IV-5

HISTORICAL OVERVIEW OF POPULATION TRENDS  ............................  IV-5
       Global Population Trends ............................................  IV-7
       Population Trends by Region ..........................................  IV-7
             IndustriflligfrH Countries  .......................................  IV- 10
             Developing Countries ........................................  FV-10

ENERGY CONSUMPTION  ...............................................  IV-12
       History of Fossil-Fuel Use ...........................................  IV-13
       Current Energy Use Patterns and Greenhouse Gas Emissions  ..................  IV- 18
             Emissions by Sector .........................................  IV-20

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                       DETAILED TABLE OF CONTENTS (Continued)


INDUSTRIAL PROCESSES	   IV-31
       Chlorofluorocarbons, Halons, and Chlorocarbons	   IV-33
             Historical Development aod Uses  	   FV-33
             The Montreal Protocol  	   IV-37
       Landfill Waste Disposal	   IV-40
       Cement Manufacture	   IV-43

LAND USE CHANGE	   IV-45
       Deforestation  	   IV-47
       Biomass Burning	   IV-50
       Wetland Loss 	   IV-51

AGRICULTURAL ACTIVITIES	   IV-55
       Enteric Fermentation In Domestic Animals	   IV-55
       Rice Cultivation   	   IV-56
       Use of Nitrogenous Fertilizer	   IV-61

IMPACT OF CLIMATIC CHANGE ON ANTHROPOGENIC EMISSIONS  	   IV-63

REFERENCES	   IV-67


                                      CHAPTER V

                             THINKING ABOUT THE FUTURE


FINDINGS  	   V-2

INTRODUCTION	   V-4

APPROACH TO ANALYZING FUTURE EMISSIONS  	   V-5
       Production	   V-7
       Consumption  	  V-ll

SCENARIOS FOR POLICY ANALYSIS	  V-13
       Scenarios with Unimpeded Emissions Growth  	  V-17
       Scenarios with Stabilizing Policies  	  V-21

ANALYTICAL FRAMEWORK  	  V-22
       Energy Module  	  V-25
       Industry Module	  V-26
       Agriculture Module  	  V-26
       Land Use and Natural Source Module  	  V-27
       Ocean Module	  V-27
       Atmospheric Composition and Temperature Module	  V-28
       Assumptions	  V-29
             Population Growth Rates	  V-29
             Economic Growth Rates  	  V-29
             Oil Prices  	  V-30
       Limitations	  V-30
                                          Vll

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                        DETAILED TABLE OF CONTENTS (Continued)


SCENARIO RESULTS  	  V-33
       Energy Sector   	  V-33
             End-use Consumption	  V-33
             Primary Energy Supply  	  V-39
             Greenhouse Gas Emissions From Energy Production and Use	  V-44
             Comparison to Previous Studies  	  V-45
       Industrial Processes	  V-56
             Halocarbon Emissions	  V-56
             Emissions From  Landfill? and Cement	  V-59
       Changes in Land Use	  V-60
       Agricultural Activities	  V-63
       Total Emissions  	  V-64
       Atmospheric Concentrations 	  V-71
       Global Temperature Increases	  V-76
       Comparison with General Circulation Model Results   	  V-81
       Relative Effectiveness of Selected Strategies  	  V-82

CONCLUSIONS	  V-82

REFERENCES	  V-87


                                       CHAPTER VI

                                 SENSITIVITY ANALYSES


FINDINGS  	  VI-3

INTRODUCTION	   VI-12

ASSUMPTIONS ABOUT THE MAGNITUDE AND TIMING OF GLOBAL
       CLIMATE STABILIZATION STRATEGIES	   VI-12
       No Participation by the Developing Countries 	   VI-13
       Delay in Adoption of Policies  	   VI-17

ASSUMPTIONS AFFECTING RATES  OF TECHNOLOGICAL CHANGE	   VI-18
       Availability of Non-Fossil Technologies 	   VI-18
       Cost and  Availability of Fossil Fuels   	   VI-22
              High Coal Prices  	   VI-22
             Alternative Oil and Natural Gas Supply Assumptions  	   VI-24
       Availability of Methanol-Fueled Vehicles  	   VI-29

ATMOSPHERIC COMPOSITION: COMPARISON OF MODEL RESULTS TO ESTIMATES
       OF HISTORICAL CONCENTRATIONS  	   VI-30

ASSUMPTIONS ABOUT TRACE-GAS SOURCES AND STRENGTHS 	   VI-34
       Methane Sources	   VI-35
       Nitrous Oxide Emissions From Fertilizer  	   VI-38
              Aohvdrpus Ammonia	   VI-38
              N-O Inching From Fertilizer  	   VI-39
       N2O Emissions From Combustion	   VI-39
                                           vui

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                        DETAILED TABLE OF CONTENTS (Continued)


UNCERTAINTIES IN THE GLOBAL CARBON CYCLE	   VI-41
       Unknown Sink In Carbon Cycle	   VI-43
       Amount of CO2 From Deforestation	   VI-44
       Alternative CO2 Models of Ocean Chemistry and Circulation	   VI-47

ASSUMPTIONS ABOUT CLIMATE SENSITIVITY AND TIMING	   VI-50
       Sensitivity of the Climate System	   VI-50
       Rate of Heat Diffusion	   VI-53

ASSUMPTIONS ABOUT ATMOSPHERIC CHEMISTRY: A COMPARISON OF MODELS   . . .   VI-54
       Model Descriptions  	   VI-56
              Assessment Model for Atmospheric Composition	   VI-56
              Isaksen Model	   VI-57
              Thompson et al. Model	   VI-58
       Results from the Common Scenarios 	   VI-59

EVALUATION OF UNCERTAINTIES  USING AMAC	   VI-67
       Atmospheric Lifetime of CFC-11  	   VI-67
       Interaction of Chlorine with Column Ozone	   VI-69
              Sensitivity of Tropospheric Ozone to CH4 Abundance  	   VI-69
              Sensitivity of OH to NOX	   VI-71

BIOGEOCHEMICAL FEEDBACKS	   VI-72
       Ocean Circulation	   VI-72
       Methane Feedbacks  	   VI-73
       Combined Feedbacks 	   VI-75

REFERENCES	   VI-78


VOLUME II (Bound under separate cover)


                                      CHAPTER VII

            TECHNICAL OPTIONS FOR REDUCING GREENHOUSE GAS EMISSIONS


PART ONE: ENERGY SERVICES	  VH-27

TRANSPORTATION SECTOR	  VII-32
       Near-Term Technical Options:  Industrialized Countries	  VII-36
              Light-Duty Vehicles	  VII-38
              Freight Transport Vehicles	  VII-49
              Aircraft	  VII-52
              Control of NOX and CO Emissions from Mobile Sources  	  VII-53
       Near-Term Technical Options:  Developing Countries 	  VII-55
              Fuel-Efficiency Improvements	  VII-57
              Improving Existing Vehicles 	  VII-58
              Alleviating Congestion ^nd Improving Roads	  VII-58
              Alternative Modes of Transportation  	  VII-59
              Alternative Fuels 	  VTI-60
       Near-Term Technical Options:  Soviet Bloc Countries	  VII-61


                                            ix

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                         DETAILED TABLE OF CONTENTS (Continued)


       Summary of Near-Term Technical Potential in the Transportation Sector	  VII-62
       Long-Term  Potential in the Transportation Sector  	  VII-63
              Urban Planning and Mass Transit	  VII-63
              Alternative Fuels  	  VII-65
              Expanded Use of Emerging Technologies	  VII-66

RESIDENTIAL/COMMERCIAL SECTOR	  VH-67
       Near-Term  Technical Options:  Industrialized Countries  	  VH-71
              Improvements in Space Conditioning	  VH-71
              Indoor Air Quality  	  VII-80
              Lighting  	  VH-81
              Appliances	  VII-83
       Near-Term  Technical Options:  Developing Countries  	  VII-83
              Increasing Efficiency of Fuelwood Use	  VH-85
              Substituting More Efficient  Fuels	  VH-87
              Retrofit Efficiency Measures for the Modern Sector	  VII-88
              New Home$ and Commercial Buildings  	  VII-89
       Near-Term  Technical Options:  Soviet Bloc Countries	  VII-90
       Summary of Near-Term Technical Potential in the Residential/Commercial Sector  ....  VII-91
       Long-Term  Potential in the  Residential/Commercial Sector	  VII-92

INDUSTRIAL SECTOR	  VII-93
       Near-Term  Technical Options:  Industrialized Countries  	  VII-98
              Accelerated Efficiency Improvements in Energy-Intensive Industries	  VII-98
              Aggreysive Efficiency Improvements of Other Industries  	VII-100
              Cogeneration	VH-101
       Near-Term  Technical Options:  Developing Countries  	VII-102
              Technological Leapfrogging	VH-103
              Alternative Fuels   	VII-104
              Retrofit Energy Efficiency Programs  	VII-105
              Agricultural Energy Use  	VII-106
       Near-Term  Technical Options:  Soviet Bloc Countries	VII-107
       Summary of Near-Term Technical Potential in the Industrial Sector	VII-111
       Long-Term Potential in the Industrial Sector	VH-112
              Structural Shifts  	VII-112
              Advanced Process Technologies	VII-113
              Non-fossil Energy	VII-115


PART TWO:  ENERGY SUPPLY  	VII-116

FOSSIL FUELS	VH-117
       Refurbishment of Existing Powerplants	VD-121
       Clean Coal Technologies  and Repowering 	VII-122
       Cogeneration	VII-123
       Natural Gas Substitution  	VH-124
               Natural Gas Use At Existing Powerplants	VII-124
               Advanced Gas-Fired Combustion Technologies  	VII-125
               Natural Gas Resource Limitations	VII-127
               Additional Gas Resources  	VII-130
       Emission Controls	VII-132
               NO.. Controls    	VH-132
               C02 Controls	VII-133

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                         DETAILED TABLE OF CONTENTS (Continued)


       Emerging Electricity Generation Technologies  	VII-134
              Fuel cells   	VII-134
              Mflgnetohydrodynamics (MHD)	VII-136

BIOMASS	VII-137
       Direct Firing of Biomass  	VII-138
       Charcoal Production  	VII-140
       Anaerobic Digestion	VII-141
       Gasification  	VII-142
       Liquid Fuels From Biomass  	\H-143
              Methanol	VH-143
              Ethanol	VII-145
              Other	VII-146

SOLAR ENERGY	VII-146
       Solar Thermal	VII-147
              Parabolic Troughs	VII-147
              Parabolic Dishes	VII-149
              Central Receivers	VII-149
              Solar Ponds	VII-150
       Solar photovoltaic	VII-150
              Crystalline Cells	VII-152
              Thin-Film Technologies	VII-153
              Multi-Junction Technologies	VII-154

ADDITIONAL PRIMARY  RENEWABLE ENERGY OPTIONS	VII-155
       Hydroelectric Power	VII-155
              Industrialized Countries	VII-155
              Developing Countries  	VII-157
       Wind Energy	VH-158
       Geothermal energy  	VII-159
       Ocean Energy	VH-162

NUCLEAR POWER  	VII-165
       Nuclear Fission	VII-165
       Nuclear Fusion	VII-170

ELECTRICAL SYSTEM OPERATION IMPROVEMENTS	VII-171
       Transmission and Distribution  	VII-171
              Superconductors	VII-172
       Storage Technologies  	VII-173
              Types of Storage Technologies  	VH-174

HYDROGEN	VH-176


PART THREE: INDUSTRY	VII-178

CFCs AND RELATED  COMPOUNDS	VII-178
       Technical Options For Reducing Emissions	VII-182
              Chemical Substitutes	VII-182
              Engineering Controls	       VII-184
              Product Substitutes	VII-185


                                             xi

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                         DETAILED TABLE OF CONTENTS (Continued)


       Summary of Technical Potential	VII-187

METHANE EMISSIONS FROM LANDFILLS	VII-187
       Methane Recovery	VH-190
       Recycling and Resource Recovery	W-192
       CO2 Emissions From Cement Production  	VII-193


PART FOUR:  FORESTRY  	VII-195

FORESTS AND CARBON EMISSIONS	VH-195

DEFORESTATION	VH-197

TECHNICAL CONTROL OPTIONS  	VH-202
       Reduce Demand for Forest Land and Products  	VII-206
              Option 1: Slow Deforestation bv Introducing Sustainable Forest Use Systems . .  . VII-209
              Option 2: Substitute Sustainable Agriculture for Swidden Forest Practices	VII-210
              Option 3: Reduce Demand For Other Land Uses That Have Deforestation
                      As A Byproduct 	VH-217
              Option 4: Increase Conversion  Efficiencies Of Technologies Using Fuelwood . .  . VH-218
              Option 5: Decrease Production of Disposable Forest Products	Vn-218
              Substitute durable wood or non-wood products for high-volume disposable
                      uses of wood  	VH-219
              Expand recycling programs  for forest products	VII-220
       Increase Supply of Forested Land and Forest Products	VII-220
              Option 1: Increase Forest Productivity:  Manage Temperate Forests For
                      Higher Yields	VII-220
               Option 2: Increase Forest Productivity:  Improve Natural Forest Management
                      of Tropical Little-Disturbed And Secondary Forests	Vn-222
              Option 3: Increase Forest Productivity:  Plantation Forests	VII-224
              Option 4: Improve Forest Harvesting Efficiency 	VII-228
              Option 5: Expand Current Tree Planting Programs in the Temperate Zone  .... VII-229
               Option 6: Reforest Surplus Agricultural Lands  	VII-231
               Option 7: Reforest Urban Areas  	VH-234
               Option 8: Afforestation for Highway Corridors	VQ-235
               Option 9: Reforest Tropical Countries	VII-236
               Obstacles to Large-Scale Reforestation in Industrialized Countries	VII-241
               Obstacles to Reforestation in Developing Countries  	VII-243
       Summary of Forestry Technical Control Options  	VII-244


PART FIVE:  AGRICULTURE	VH-249

RICE CULTIVATION	VH-252
       Existing Technologies and Management Practices	W-253
       Emerging Technologies	W-257
       Research Needs and Economic Considerations	W-258

USE OF NITROGENOUS FERTILIZER  	VH-259
       Existing Technologies and Management Practices	VQ-260
               Management Practices That Affect NgO Production	VH-260
               Technologies that Improve  Fertilization Efficiency  	VII-262


                                              xii

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                       DETAILED TABLE OF CONTENTS (Continued)


       Emerging Technologies	VII-263
       Research Needs and Economic Considerations	VII-264

ENTERIC FERMENTATION IN DOMESTIC ANIMALS  	VII-265
       Methane Emissions from Livestock  	VII-268
       Existing Technologies and Management Practices	VII-269
       Emerging Technologies	VII-272
       Research Needs and Economic Considerations	VII-273


                                     CHAPTER VIH

                                   POLICY OPTIONS


FINDINGS  	    Vffl-2

INTRODUCTION	    YIH-6

INTERNALIZING THE COST OF CLIMATE CHANGE RISKS  	    VHI-8
       Evidence of Market Response to Economic Incentives: Energy Pricing  	    VIII-9
       Financial Mechanisms to Promote Energy Efficiency	  VIII-14
       Creating Markets for Conservation  	  VDI-16
       Limits to Price-Oriented Policies  	  VITJ-IS

REGULATIONS AND STANDARDS  	  VTJI-22
       Existing Regulations that Restrict Greenhouse Gas Emissions  	  VHI-23
             Regulation of Chlorofluorocarbons	  Vin-24
             Energy Efficiency Standards	  VTII-25
             Air Pollution Regulations	  VHI-28
             Waste Management	  VTH-29
             Utility Regulation	  Vffl-31
       Existing Regulations that Encourage Emissions Reductions 	  VQI-35

RESEARCH AND  DEVELOPMENT  	  VHI-39
       Energy Research and Development	  VHI-40
       Global Forestry Research & Development	  Vm-45
       Research to Eliminate Emissions of CFCs	  Vni-46

INFORMATION AND TECHNICAL ASSISTANCE PROGRAMS	  VHI-47

CONSERVATION  EFFORTS BY FEDERAL AGENCIES  	  VIE-SO

STATE AND LOCAL EFFORTS	  VHI-52

PRIVATE SECTOR EFFORTS	  VIH-S?

COMPLEMENTARY STRATEGIES TO REDUCE GREENHOUSE GAS EMISSIONS	  Vffl-59

IMPLICATIONS OF POLICY CHOICES AND TIMING	  VIH-63
                                          xui

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                      DETAILED TABLE OF CONTENTS (Continued)


SENSITIVITY TESTS OF THE EFFECT OF ALTERNATIVE POLICIES ON
      GREENHOUSE GAS EMISSIONS: RISK TRADE-OFFS	  VHI-67
      Policies That Increase Greenhouse Gas Emissions 	  VHI-69
      Policies Designed to Reduce Greenhouse Gas Emissions  	  Vm-76
      Conclusions From the Sensitivity Tests	  Vffl-78

REFERENCES	  YIH-83


                                    CHAPTER IX

        INTERNATIONAL COOPERATION TO REDUCE GREENHOUSE GAS EMISSIONS


FINDINGS  	  IX-2

INTRODUCTION	  IX-4

THE CONTEXT FOR POLICIES INFLUENCING GREENHOUSE GAS EMISSIONS IN
DEVELOPING COUNTRIES  	  IX-5
      Economic Development and Energy Use  	  IX-7
      Oil Imports, Capital Shortages, and Energy Efficiency	   IX-13
      Greenhouse Gas Emissions and Technology Transfer  	   IX-17

STRATEGIES FOR REDUCING GREENHOUSE GAS EMISSIONS  	   IX-18
      International Lending and Bilateral Aid  	   IX-20
             U.S. Bilateral Assistance Programs 	   IX-21
             Policies and Programs of Multilateral Development Banks	   IX-24
      New Directions  	   IX-31

REDUCING GREENHOUSE GAS EMISSIONS IN EASTERN BLOC NATIONS 	   DC-33

US. LEADERSHIP TO PROMOTE INTERNATIONAL COOPERATION 	   IX-36
      Restricting CFCs to Protect the Ozone Layer	   IX-36
      International Efforts to Halt Tropical Deforestation  	   IX-38
      Ongoing Efforts Toward International Cooperation	   IX-42

REFERENCES	   IX-45
                                         XIV

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                                      LIST OF FIGURES
Executive Summary
                                                                                          Page
     1        Carbon Dioxide Concentrations at Mauna Loa and Fossil Fuel CO2 Emissions . .      3
     2        Structure of the Atmospheric Stabilization Framework  	      8
     3        Greenhouse Gas Contributions to Global Warming	      12
     4        Impact of CO? Emissions Reductions on Atmospheric Concentrations	      14
     5        Atmospheric Concentrations	      25
     6        Realized Wanning:  No Response Scenarios	      27
     7        Realized Warming:  No Response and Stabilizing Policy Scenarios  	      31
     8        Stabilizing Policy Strategies:  Decrease in Equilibrium Warming
              Commitment 	      34
     9        Rapid Reduction Strategies:  Additional Decrease in Equilibrium Warming
              Commitment 	      37
     10       Share of Greenhouse Gas Emissions by Region	      41
     11       Increase in Realized Warming When Developing Countries Do Not
              Participate	      43
     12       Increase in Realized Warming Due to Global Delay in Policy Adoption	      44
     13       Accelerated Emissions Cases:  Percent Increase  in Equilibrium Warming
              Commitment 	      46
     14       Impact of Climate Sensitivity on Realized Warming   	      48
     15       Activities Contributing to Global Wanning  	      55
     16       Primary Energy Supply by Type  	      58
     17       CO2 Emissions From Deforestation	      73


VOLUME I (bound under separate cover)
Chapter I

     1-1

     1-2
Carbon Dioxide Concentrations at Mauna Loa and Fossil Fuel CO2
Emissions 	     1-10
Impact of CO 2 Emissions Reductions on Atmospheric Concentrations	     1-11
Chapter II

     2-1        Greenhouse Gas Contributions to Global Warming	
     2-2        Carbon Dioxide Concentration 	
     2-3        CO2 Atmospheric Concentrations by Latitude 	
     2-4        The Carbon Cycle	
     2-5        Gas Absorption Bands	
     2-6        Methane Concentration  	
     2-7        Current Emissions  of Methane by Source	
     2-8        Nitrous Oxide Concentrations	
     2-9        Temperature Profile and Ozone Distribution in the Atmosphere
                                                                             II-6
                                                                            11-11
                                                                            11-12
                                                                            11-15
                                                                            H-20
                                                                            n-23
                                                                            11-25
                                                                            H-31
                                                                            11-41
                                              xv

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                                 LIST OF FIGURES (Continued)
                                                                                          Page
Chapter III

     3-1        Surface Air Temperature	    III-7
     3-2        Oxygen Isotope Record From Greenland Ice Cores  	    III-9
     3-3        Carbon Dioxide and Temperatures Records From Antarctic Ice Core  	   111-10
     3-4        Oxygen Isotope Record From Deep Sea Sediment-Cores	   III-ll
     3-5        Global Energy Balance  	   Ill-16
     3-6        Equilibrium Temperature Changes from Doubled CO?	   ID-IS
     3-7        Greenhouse Gas Feedback Processes	   in-21


Chapter IV

     4-1        Regional Contribution to  Greenhouse Warming ~  1980s	    IV-6
     4-2        Regional Population Growth -  1750-1985	    IV-8
     4-3        Global Energy Demand by Type ~ 1950-1985 	   IV-14
     4-4        COo Emissions Due to Fossil Fuel Consumption - 1860-1985  	   IV-16
     4-5        Global Commercial Energy  Demand by Region	   IV-17
     4-6        1985 Sectoral Energy Demand by Region	   IV-19
     4-7        Potential Future Energy Demand  	   IV-32
     4-8        Historical Production of CFC-11 and CFC-12 	   IV-36
     4-9        CFC-11 and CFC-12 Production/Use for Various Countries	   IV-39
     4-10      CO2 Emissions from Cement Production - 1950-1985	   IV-44
     4-11      Cement Production in Selected Countries - 1951-1985 	   IV-46
     4-12      Net Release of Carbon from Tropical Deforestation - 1980	   IV-48
     4-13      Wetland Area and Associated Methane Emissions  	   IV-53
     4-14      Trends in Domestic Animal Populations ~ 1890-1985  	   IV-57
     4-15      Rough Rice Production - 1984	   IV-59
     4-16      Rice Area Harvested ~ 1984  	   IV-60
     4-17      Nitrogen Fertilizer Consumption - 1984/1985 	   IV-64


Chapter V

     5-1        Total U.S. Energy Consumption per GNP  Dollar - 1900-1985	     V-8
     5-2       Consumption of Basic Materials  	    V-10
     5-3        Population by Region   	    V-19
     5-4        Structure of the Atmospheric Stabilization Framework 	    V-23
     5-5        Geopolitical Regions For Climate  Analyses	    V-24
     5-6       End-Use Fuel Demand by Region	    V-34
     5-7       End-Use Electricity Demand by Region	    V-35
     5-8       Share of End-Use Energy Demand by Sector 	    V-38
     5-9       Primary Energy Supply by Type  	    V-40
     5-10      Share of Primary Energy Supply by Type  	    V-41
     5-11      Energy Demand for Synthetic Fuel Production	    V-42
     5-12      Emissions of Major CFCs  	    V-58
     5-13      CO2  Emissions from Deforestation  	    V-62
     5-14      CO2  Emissions by Type	    V-66
     5-15      Share of CO2 Emissions  by Region	    V-68
     5-16      CH4  Emissions by Type	    V-69
                                               xvi

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                                 LIST OF FIGURES (Continued)

                                                                                           Page
     5-17      Share of CH4 Emissions by Region	    V-70
     5-18      Atmospheric  Concentrations	    V-72
     5-19      Realized and Equilibrium Warming	    V-77
     5-20      Relative Contribution to Warming by 2100  	    V-80
     5-21      Stabilizing Policy Strategies: Decrease in Equilibrium Warming Commitment  . . .    V-83
Chapter VI
     6-1        Increase in Realized Warming When Developing Countries Do Not
               Participate	   VI-16
     6-2        Increase in Realized Warming Due to Global Delay in Policy Adoption	   VI-19
     6-3        Availability of Non-Fossil Energy Options	   VI-21
     6-4        Impact  of 1% Per Year  Real Escalation in Coal Prices	   VI-23
     6-5        Impact  of Higher Oil Resources On Total Primary Energy Supply  	   VI-26
     6-6        Impact  of Higher Natural Gas Resources on Total Primary Energy Supply	   VI-28
     6-7        Realized Warming Through 1985	   VI-32
     6-8        Increase in Realized Warming Due to Changes in the Methane Budget	   VI-37
     6-9        Change in Atmospheric Concentration of N2O Due to Leaching	   VI-40
     6-10       Change in Atmospheric Concentration of N2O Due to Combustion	   VI-42
     6-11       Impact  on Realized Warming Due to Size of Unknown Sink	   VI-45
     6-12       CO2 From Deforestation Assuming High Biomass  	   VI-46
     6-13       Impact  of High Biomass Assumptions on Atmospheric Concentration of CO2 . . .   VI-48
     6-14       Comparison of Different Ocean  Models	   VI-51
     6-15       Impact  of Climate Sensitivity on Realized Warming  	   VI-52
     6-16       Change in Realized Warming Due to Rate of Ocean Heat Uptake	   VI-55
     6-17       Regional Differences for Urban  Areas With  Different Emissions of CO and
               NO  	   VI-64
     6-18       OH and Ozone Perturbations in the Isaksen and Hov Model	   VI-66
     6-19       Sensitivity of Atmospheric Concentration of CFC-11 to Its Lifetime	   VI-68
     6-20       Change in Realized Warming Due to Rate of Interaction of CLx With
               Ozone	   VI-70
     6-21       Increase in Realized Wanning Due to Change in Ocean Circulation	   VI-74
     6-22       Increase in Realized Warming Due to Methane  Feedbacks 	   VI-76
     6-23       Increase in Realized Warming Due to Change in Combined Feedbacks	   VI-77
                                              xvu

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                                 LIST OF FIGURES (Continued)
                                                                                           Page
VOLUME II (bound under separate cover)
Chapter VII

     7-1        Current Contribution to Global Warming	  VH-20
     7-2        Global Energy Use by End-Use  	  VH-28
     7-3        Secondary Energy Consumption by Region 	  Vn-30
     7-4        End-Use Energy Demand by Sector	  VH-33
     7-5        Transportation Energy Use by Region  	  VII-35
     7-6        Components of Transportation Energy Use in the OECD: 1985	  VII-37
     7-7        U.S. Residential/Commercial Energy Use	  VH-68
     7-8        Residential/Commercial Energy Use by Region	  VII-70
     7-9        Industrial Energy Use by Region	  VII-97
     7-10      Electricity Utility Demand by Fuel Type	VH-118
     7-11      Average Fossil Powerplant Efficiency	VII-120
     7-12      Strategies for Improving Efficiency of Biomass Use  	VII-139
     7-13      Basic Solar  Thermal Technologies	VH-148
     7-14      Photovoltaic Electricity Costs  	VH-151
     7-15      Nuclear Capital  Costs  	VH-167
     7-16      Industrial Process Contribution to Global Warming  	VII-179
     7-17      Emissions of Major CFC's	VH-180
     7-18      CH4 Emissions by Type	VII-188
     7-19      Movement of Tropical Forest Lands Among Stages of Deforestation and Potential
               Technical Response Options	W-198
     7-20      Population Growth, Road Building, and Deforestation in Amazonia	VII-201
     7-21      Model Agroforestry Farm Layout, Rwanda 	VII-214
     7-22      Agricultural  Practices Contribution to Global Warming	VII-250
     7-23      Trace Gas Emissions From Agricultural Activities  	VII-251


Chapter VIII

     8-1       Energy Intensity Reductions, 1973-1983	VIII-11
     8-2       U.S. Electricity Demand and Price	VIII-15
     8-3       Cost of Driving Versus Automotive Fuel Economy	Vm-21
     8-4       U.S. Carbon Monoxide Emissions 	VHI-30
     8-5       Changes in U.S. Renewable Energy  R&D Priorities Over Time  	VIH-42
     8-6       Cost of Potential Residential Electricity Conservation
               in Michigan by 2000	VHI-55
     8-7       U.S. Energy Consumption By Fuel Share  	Vffl-66
     8-8       Atmospheric Response to Emissions Cutoff	WI-68
     8-9       Actual and Projected U.S. Coal Production	Vffl-70
     8-10      Accelerated Emissions Cases: Percent Increase in Equilibrium Warming
               Commitment 	Vm-74
     8-11      Rapid Reduction Strategies: Additional Decrease in Equilibrium Warming
               Commitment 	Vm-79
                                               XVffl

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                               LIST OF FIGURES (Continued)



                                                                                       Page
Chapter IX



     9-1       Greenhouse Gas Emissions By Region	    IX-6
                                            xix

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                                        LIST OF TABLES
Executive Summary
    2
    3
    4
    5
    6
    7
    8
Approximate Reductions in Anthropogenic Emissions Required to Stabilize
Atmospheric Concentrations at Current Levels	
Overview of Scenario Assumptions	
Current and Projected Trace Gas Emissions Estimates  	
Scenario Results for Realized and Equilibrium Warming	
Examples of Policy Responses by the Year  2000	
Sensitivity Analysis:  Impact on Realized Warming and Equilibrium Warming
Key Global Indicators for Energy and CO,	
Major Chlorofluorocarbons,  Halons, and Chlorocarbons:  Statistics and Uses .
                                                                                            Page
15
21
24
33
39
50
61
68
VOLUME I (bound under separate cover)
Chapter II

    2-1         Radiative Forcing for a Uniform Increase in Trace Gases From Current Levels . .    11-21
    2-2         Trace Gas Data  	    H-51


Chapter IV

    4-1         Regional Demographic Indicators	    IV-9
    4-2         Emission Rate Differences by Sector   	    IV-21
    4-3         End-Use Energy Consumption Patterns for the Residential/Commercial
               Sectors  	    IV-24
    4-4         Carbon Dioxide Emission Rates for Conventional and Synthetic Fuels  	    FV-28
    4-5         Estimates of Global Fossil-Fuel Resources	    IV-30
    4-6         Major Halocarbons:  Statistics and Uses	    IV-34
    4-7         Estimated 1985 World Use of Potential Ozone-Depleting Substances	    IV-38
    4-8         Refuse Generation Rates in Selected  Cities	.'	    IV-42
    4-9         Land-Use:  1850-1980  	    FV-49
    4-10        Summary Data on Area and Biomass Burned   	    IV-52
    4-11        Nitrous Oxide Emissions by Fertilizer Type	    IV-62


Chapter V

    5-1         Overview of Scenario Assumptions	    V-14
    5-2         Economic Growth Assumptions	    V-18
    5-3         Key Global Indicators  	    V-46
    5-4         Comparison of No Response Scenarios and NEPP  	    V-48
    5-5         Comparison of Stabilizing Policy Scenarios and ESW	    V-49
    5-6         Summary of Various Primary Energy Forecasts for the Year 2050	   V-51
    5-7         Comparison of Energy-Related Trace-Gas Emissions Scenarios	    V-55
    5-8         Trace Gas Emissions	   V-65
    5-9         Comparison of Estimates of Trace-Gas Concentrations in 2030 and 2050  	   V-75
                                                xx

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                                  LIST OF TABLES (Continued)
                                                                                            Page
Chapter VI

    6-1
    6-2
    6-3
    6-4
    6-5
Impact of Sensitivity Analyses on Realized Warming and Equilibrium Warming
Comparison of Model Results to Concentrations in 1986	
Low and High Anthropogenic Impact Budgets for Methane  	
Comparison of Emission Estimates for  EPA #2, RCW and SCW Cases	
Comparison of Results from Atmospheric Chemistry Models for the Year 2050
Compared to 1985	
 VI-7
VI-33
VI-36
VI-60

VI-61
VOLUME II (bound under separate cover)

Chapter VII

    7-1        Key Technical Options by Region and Time Horizon  	  VTI-19
    7-2        High  Fuel Economy Prototype Vehicles  	  VII-39
    7-3        Actual New Passenger Car Fuel Efficiency	  VTI-40
    7-4        Summary of Energy Consumption and Conservation Potential With
              Major Residential Equipment  	  VII-84
    7-5        Reduction of Energy Intensity In the Basic Materials Industries   	  VII-95
    7-6        Energy Intensities of Selected Economies   	VII-108
    7-7        Innovation in Steel Proudction Technology	VH-110
    7-8        Total U.S. Gas Reserves  and Resources  	VTI-128
    7-9        CO^ Scrubber Costs  Compared to SO? Scrubber Costs	VII-135
    7-10       Estimates of Worldwide Geothermal Electric Power Capacity Potential  	VII-160
    7-11       Capacity of Direct Use Geothermal Plants in Operation - 1984	VII-163
    7-12       Geothermal Powerplants  On-Line as of 1985	VII-164
    7-13       Major Forestry Sector Strategies  for Stabilizing Climate Change  	VII-203
    7-14       Potential Forestry Strategies  and  Technical Options to Slow Climate Change .... VII-207
    7-15       Comparison of Land Required for Sustainable Swidden Versus Agricultural
              Practices  	VII-212
    7-16       Potential Carbon Fixation and Biomass Production Benefits from Agroforestry
              Systems	VD-216
    7-17       Natural and Managed Tropical Moist Forest Yields  	VII-223
    7-18       Productivity Increases Attributable to Intensive Plantation Management  	VII-227
    7-19       Summary of Major Tree  Planting Programs in the U.S	VII-230
    7-20       Estimates of CRP Program Acreage Necessary to Offset CO? Production from
              New Fossil Fuel-Fired Electric Plants, 1987-96, by Tree Species or Forest Type  .  . VII-233
    7-21       Estimates of Forest Acreage Required to  Offset Various CO? Emissions Goals  .  . VII-239
    7-22       Comparison of Selected Forest Sector Control Options:  Preliminary Estimates  .  . VII-245
    7-23       Overview of Two Social Forestry Projects  Proposed to Offset CO2 Emissions of
              a 180-MW Electric Plant in Connecticut	VH-248
    7-24       Water Regime and Modern Variety Adoption for Rice Production in Selected
              Asian Countries  	VII-256
    7-25       Average  Meat Yield  Per  Animal   	VH-267

Chapter VIII

    8-1        Energy Intensity of Selected  National Economies, 1973-85  	Vffl-12
    8-2        Payback  Periods in Years for Appliances,  1972-1980  	Vm-20
                                               xxi

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                                  LIST OF TABLES (Continued)

                                                                                            Page
   8-3        Appliance Efficiency Improvements Required by Law  	Vm-26
   8-4        Cogeneration Facilities	VIII-34
   8-5        Erodible Acreage Available to Offset CO2 Emissions From Electricity
              Production	Vm-37
   8-6        Government Efficiency Research and Development Budgets in OECD Member
              Countries, 1986	VHI-41
   8-7        Federal Energy Expenditures and Cost Avoidance, FY1985-FY1987	VHI-51
   8-8        Scenario Results for Realized and Equilibrium Wanning	VIII-82

Chapter IX

   9-1        1985 Population and Energy Use Data From Selected Countries	    IX-8
   9-2        Efficiency of Energy Use in Developing  Countries:  1984-1985  	   IX-10
   9-3        Potential for Electricity Conservation in  Brazil	   IX-12
   9-4        Net Oil Imports and Their Relation to Export Earnings for Eight Developing
              Countries, 1973-1984  	   IX-14
   9-5        Annual Investment in Energy Supply as  a Percent of Annual  Total Public
              Investment (Early 1980s)  	   DC-15
   9-6        World Bank Estimate of Capital Requirements for Commercial Energy in
              Developing Countries, 1982-1992  	   DC-16
   9-7        U.S. AID Forestry Expenditures by Region	   DC-23
   9-8        World Bank Energy Sector Loans in 1987	   DC-26
   9-9        Expenditures of Multilateral and Bilateral Aid Agencies in the Energy Area  ....   IX-27
   9-10       World Bank Energy Conservation Projects: Energy Sector Management
              Assistance Program (ESMAP) Energy Efficiency Initiatives	   IX-30
   9-11       Energy Use in the Soviet Union and Eastern Bloc	   IX-34
   9-12       Countries Responsible for Largest Share of Tropical Deforestation  	   IX-41
                                               xxu

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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. Climatic Change                                                   Daniel Lashof
                                                                              Alan Robock

Chapter IV. Human Activities Affecting Trace Gases and Climate                Barbara Braatz
                                                                                Craig Ebert

Chapter V.  Thinking About the Future                                          Daniel Lashof
                                                                              Leon Schipper

Chapter VI. Sensitivity Analyses                                                  Craig Ebert

Chapter VII. Technical Control Options                      Paul Schwengels (Energy  Services)
                                                          Michael Adler (Renewable Energy)
                                                                     Dillip Ahuja (Biomass)
                                                                Kenneth Andrasko (Forestry)
                                                                Lauretta Burke (Agriculture)
                                                                Craig Ebert (Energy Supply)
                                                              Joel Scheraga (Energy Supply)
                                                                   John Wells (Halocarbons)

Chapter VIII.  Policy Options                                                     Alan Miller

Chapter IX. International Cooperation to Reduce Greenhouse Gas Emissions        Alan Miller
                                                                             Jayant Sathaye

Appendix A. Model Descriptions                                               William Pepper

Appendix B.  Scenario Definitions                                                 Craig Ebert

Appendix C.  Results of Sensitivity Analyses                                        Craig Ebert
                                           xxui

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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 provided by  Susan MacMillan.  Technical,  graphics,  and typing assistance  was provided by



Courtney Dinsmore, Katey Donaldson, Donald Devost, Michael Green, Karen Zambri, Judy Koput,



Donna Whitlock, Margo Brown,  and Cheryl LaBrecque.








    Literally hundreds of other people have contributed to  this report, including the organizers and



attendants  at four workshops sponsored by EPA 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 others, Thomas Bath,  Deborah Bleviss, Gary Breitenbeck, William Chandler, Robert Friedman,



Howard  Geller, James Hansen, Tony Janetos,  Stan Johnson, Julian Jones, Michael Kavanaugh,



Andrew Lacis, Michael MacCracken, Elaine Matthews, William Nordhaus, Steven Piccot, Marc  Ross,



Stephen Schneider, Paul Steele, Pieter Tans, Thomas Wigley, Edward Williams, and Robert Williams.








    This  work was conducted  within  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.
                                            xxiv

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                                       Review Draft

                                   POLICY OPTIONS

                        FOR STABILIZING GLOBAL CLIMATE

                                     Executive Summary

INTRODUCTION	   1
       Congressional Request for Reports  	   1
       Previous Studies   	   2
       Goals of this Study	   4
       Approach Used to Prepare this Report	   6
       Limitations  	   9

HUMAN IMPACT ON THE CLIMATE SYSTEM	  11
       The Greenhouse Gas Buildup	  11
       The Impact of Greenhouse Gases  on Global Climate  	  17

SCENARIOS FOR POLICY ANALYSIS	  19
       Defining Scenarios  	  19
       Scenarios with Unimpeded Emissions Growth  	  22
       The Impact of Policy Choices  	  29
       Sensitivity of Results to Alternative Assumptions	  45

EMISSIONS REDUCTION STRATEGIES BY ACTIVITY	  54
       Energy Production and Use  	  56
       Industrial Activity	  66
       Changes in Land Use 	  71
       Agricultural Practices 	  75

THE NEED FOR POLICY RESPONSES	  77
       A Wide Range of Policy Choices  	  78
       The Timing of Policy Responses  	  79

FINDINGS  	  83

       I.  Uncertainties regarding climatic change are large, but there is a growing consensus
              in the scientific community that significant global warming due to anthropogenic
              greenhouse gas emissions  is probable over the next century, and that  rapid climatic
              change is possible	  83

       II. Measures undertaken to limit  greenhouse gas emissions would decrease the magnitude
              and speed of global warming, regardless of uncertainties about the  response of the
              climate system	  85

       III. No single country or source  will contribute more than a fraction of  the greenhouse
              gases that will warm the world; any overall solution will require cooperation of many
              countries and reductions in  many sources	  87

       IV.  A wide range  of policy choices is available to reduce greenhouse gas emissions while
              promoting economic development, environmental, and social goals	  89
   DRAFT - DO NOT QUOTE OR CITE         xxv                         February 21, 1989

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Policy Options for Stabilizing Global Climate - Review Draft                Executive Summary








INTRODUCTION








    The composition of the Earth's atmosphere is changing.  There is a growing scientific consensus



that the observed trends  and projected increases in the atmospheric concentrations of greenhouse



gases  will  alter   the  global   climate.     "Greenhouse"   gases  (carbon   dioxide,  methane,



chlorofluorocarbons, and  nitrous oxide, among others) in the atmosphere absorb heat that radiates



from the Earth's surface and emit some of this heat downward, warming the climate.  Without this



"greenhouse effect," the Earth would be about 30C (60F) 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.  Although the specific rate and magnitude of future climate change



is hard to predict, 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 private and public institutions.








Congressional Request for Reports








    To better define the potential effects of global  climate change and identify the options that are



available to influence the composition of the atmosphere and the rate of climatic change, Congress



asked the U.S. Environmental Protection Agency to undertake two studies on the greenhouse effect.



In one of these studies Congress directed EPA to include:







    "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









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Policy Options for Stabilizing Global Climate - Review Draft                Executive Summary






    gases such as methane and nitrous oxide; as well as the potential for and effects of reducing



    deforestation and increasing reforestation efforts."







This report responds to that request.  The second study was to focus on "the potential health and



environmental effects  of climate change."   A companion  report,  The Potential Effects of Climate



Change on the United  States, responds to the second request.








    This Executive  Summary describes  the goals established by  EPA for this study,  considering



previous work and our Congressional mandate.  The analytical framework developed for this study



is briefly described and its limitations are noted. We then summarize current understanding of the



greenhouse gases and their impact on global  climate.  A description of the scenarios that were



developed to explore the sensitivity of the climate system to policy choices is presented next.  The



results of this scenario analysis follows, emphasizing the relative  impact of various options.  The



technological and policy strategies that appear most promising for reducing greenhouse gas emissions



are then presented by major activity category:  energy production and use, other  industrial activities,



changes in land use, and agricultural practices.   The policy options that are available for promoting



these emission reduction strategies are then reviewed,  giving consideration to the timing of policy



responses to  the greenhouse gas buildup.  Finally, the major findings of this study are summarized.








Previous  Studies








    Atmospheric measurements indicating  that  the composition of the atmosphere is changing (e.g.,



Figure 1) have  led to  many assessments of  the potential magnitude  of future  greenhouse gas



emissions, future greenhouse gas  concentrations,  and  associated climatic changes.   A scientific



consensus has emerged  from these studies that increased concentrations of greenhouse gases will



result in climate change.  Moreover, there is serious risk that, in the absence  of policy responses,








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Policy Options for Stabilizing Global Climate - Review Draft
Executive Summary
                                   FIGURE 1



        CARBON DIOXIDE CONCENTRATION AT MAUNA LOA
                   AND FOSSIL FUEL  CO2 EMISSIONS
     310
                                                                        i! 5UO  O

                                                                             O
                                                                        uouo  t-
                                                                        55UO  w

                                                                             Ctf

                                                                        5000  g



                                                                        I 5UO  _j
                                                                             UJ

                                                                        1 QUO  Qt,


                                                                             J
                                                                        asoo  M
                                                                             OT
                                                                             OT
                                                                        3000  O
                                                                             fa.


                                                                        2500
      1856 I860  1982 1884 1888 1888 1870 1873 1874  1876 1878 1880  1982 1884 1888  1888
Figure  1.  The solid line depicts monthly concentrations  of atmospheric CO2 at Mauna  Loa
Observatory, Hawaii. The yearly oscillation is explained mainly by the annual cycle of photosynthesis
and respiration of plants in  the northern hemisphere.  The dashed line represents the annual
emissions of CO2, in units of carbon, due to fossil fuel combustion.
DRAFT - DO NOT QUOTE OR CITE
   February 21, 1989

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Policy Options for Stabilizing Global Climate - Review Draft                Executive Summary






greenhouse gas emissions will continue to increase due to population and economic growth, and that



sometime during the middle of the next century, the buildup of greenhouse gases will have a climatic



effect equivalent to doubling the concentration of carbon dioxide from preindustrial levels.







    A study  by the  U.S. National Academy  of Sciences in 1979  concluded that doubling  the



concentration of carbon dioxide relative  to the preindustrial atmosphere would result in an eventual



(equilibrium)  global warming of 1.5-4.5C.  Subsequent re-evaluations by the National Academy of



Sciences  (in 1983 and 1987), as well as the "State-of-the-Art" report issued by the U.S. Department



of Energy in  1985, have reaffirmed this estimate.  Recent general circulation model results and a



recent review conducted for the international Scientific Committee On Problems of the Environment



(SCOPE) suggest that a warming of 5.5C as a result of doubling carbon dioxide may be at least as



likely as  a warming of 1.50C.








    Only a few studies have examined potential policy responses to the greenhouse gas buildup. The



IEA/ORAU Long-Term Global Energy CO2 Model developed for the Department of Energy in 1983



was  used in  many of these studies, including EPA's 1983 report,  Can We  Delay a Greenhouse



Warming?  This study investigated  the extent to which  policy measures might influence the timing of



a 2C global warming. The IEA/ORAU model was  also used for important studies conducted at



the Massachusetts  Institute of Technology Energy Laboratory (in 1984) and the World Resources



Institute  (in 1987).  These studies concluded that policy choices could have a major influence on  the



total wanning that may be experienced  during the next century.








Goals of this Study








    Congress presented  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








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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 impact the rate and magnitude of climate change.  It is also necessary that the



scope of this study be global and the time horizon be more than a century, because of the long lags



built into both the economic and climatic systems (we chose  1985-2100 as the tune frame for the



analysis).  We cannot predict what the future will bring, but scenarios can be developed to explore



policy options.







Based on these considerations 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 wanning.
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Approach Used to  Prepare this Report








    To achieve these goals 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.  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.








    Based on the outcome of  this process, EPA developed an integrated analytical framework to



organize the data and assumptions required to  calculate (1) emissions of radiativety and chemically



active gases, (2) concentrations of greenhouse gases, and (3) changes in global 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.  It is the first attempt  to relate the underlying forces  (e.g., population growth,



economic growth, and technological change) to  the emissions of all the important greenhouse gases.



This framework makes it  possible to estimate the impact  of changes  in  these factors  on the



composition of the atmosphere and global temperatures.  In constructing  this framework, we used



the results of more sophisticated models of individual components as a basis for our analysis.  While



we believe that this framework generally reflects the current state of scientific knowledge, there are



important limitations (discussed below) that may affect the results of our analysis.








    Emissions of the greenhouse gases COj, CH4, N2O, and of a number of halocarbons are explicitly



calculated within the  framework based  on assumptions about activities that generate these gases, such








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 as energy production and consumption, industrial processes, agricultural practices, and deforestation.



 Emissions of CO and NO,, which are not themselves greenhouse gases, are also explicitly calculated,



 as  these  gases  can significantly alter  the  chemistry  of the atmosphere and  thus  affect the



 concentrations of the greenhouse gases.  The four emissions modules (Figure 2) use input data,



 including  scenario  specifications, for  population growth,  GNP, energy  efficiency,  agricultural



 productivity, and the rate of deforestation.  The Energy Module is based on the IEA/ORAU Long-



 Term Global Energy CO2 Model developed for the U.S. Department of Energy (modified considerably



 for this  study),  and on analysis of energy end-use patterns conducted by Lawrence Berkeley



 Laboratory and the World Resources Institute. EPA's CFC model, developed to assess stratospheric



 ozone depletion,  forms  the primary component of the Industry Module.  The Agriculture Module is



 based on the  Basic Linked System developed at the International  Institute of Applied Systems



 Analysis  and emissions coefficient estimates from the literature; and the  Land-Use and  Natural



 Source Module uses the Terrestrial Carbon Model developed at the Woods Hole Marine Biological



 Laboratory for CO2 emissions related to deforestation. Emissions  are estimated for nine regions  of



 the globe  and are calculated every 5  years from 1985  to 2025 and then every 25 years through 2100.








    In addition to the  emissions modules, there  are two concentration  modules.  Together these



 concentration modules estimate changes in global atmospheric concentrations  of the greenhouse gases



 based on the projected  emissions and changes in global temperatures that result from the calculated



 concentrations. The Atmospheric Composition Module consists of a highly simplified model of global



 chemistry developed by NASA and a parameterization of the impact  of changes in greenhouse gas



 concentrations on the  radiation balance of the Earth.   The  Ocean Module contains a modified



version of the Goddard  Institute for Space Studies ocean model that simultaneously calculates carbon



 dioxide and heat uptake. The Ocean Module  also  contains four additional models for carbon dioxide



uptake assembled by the Complex Systems Research Center  at the University of New Hampshire.



The calculated atmospheric trace-gas concentrations and temperature  changes affect the emissions









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Executive Summary
                            FIGURE 2

STRUCTURE OF THE ATMOSPHERIC STABILIZATION FRAMEWORK
Inputs
Base case
Assumptions
Resources
Population
Growth
Productivity
Technology

Alternative
Strategies


_fc^^
F
Emissions
orecasting
Modules
Energy

Industry

Agriculture

                                   Concentration
                                   Determination
                                     Modules
                                      Atmospheric

                                      Composition

                                        Ocean
       Outputs
                                                         Atmospheric

                                                        Concentrations
                                                            and
                                                         Temperature

                                                           Change
                              Feedbacks
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modules in the next time period. The estimates of global temperature change serve as indicators for



the rate and magnitude of global  change, but  it is  important  to keep in mind  that changes  in



precipitation and other factors may be as important as changes in global temperature, and that the



timing and magnitude of climatic changes at a regional level may differ significantly from the global



average.








Limitations








    This analytical framework attempts to incorporate some representation of the major processes



that will influence the rate and magnitude of greenhouse wanning 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:








           Economic growth rates are difficult to forecast and will strongly influence



            future greenhouse gas emissions.  Although there are factors cutting in both



            directions, emissions can generally be expected to be higher  if economic



            growth  is more  rapid.   Our  alternative  assumptions may  not adequately



            reflect the plausible range of possible growth  rates.







           Economic linkages are  not fully captured.  The type of economic analysis



            conducted cannot 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



            with regard to developing  countries, as it is unclear if they will be able to



            obtain the capital needed  to grow as fast or  develop the energy supplies



            assumed in some of the scenarios.








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          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



           scenarios  (see below for the  scenario definitions).   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 to be cost-



           effective,  but no attempt has been  made to rank the cost-effectiveness of



           each strategy or to estimate the government expenditures or total social costs



           or benefits 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
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           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 taking up 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.








HUMAN IMPACT ON THE CLIMATE SYSTEM








The Greenhouse Gas Buildup








    Many greenhouse gases are currently accumulating in the atmosphere.  The most important is



carbon dioxide (CO^, followed by methane (CH4),  chlorofluorocarbons  (CFCs),  and nitrous oxide



(N2O) (Figure 3).  Carbon dioxide is a fundamental product of burning  fossil fuels (coal, oil, and



gas), and is also released as a result of deforestation (Box  1).  The largest methane source is decay







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                     Executive Summary
                                FIGURE 3
 GREENHOUSE GAS CONTRIBUTIONS TO GLOBAL WARMING
                             1880-1980

                               Other(8%)
                  CFC-11&-12
                     (8%)

                  N20 (3%
                   CH4
                   (15%)
            CO2(66%)
                               1980s

                       Other(13%)
             CFC-11 &-12
                 (14%)
                                                 CO2 (49%)
                     CH4(18%)
Figure 3. 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.
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of organic matter in the absence of oxygen, while CFCs are produced only by the chemical industry.



The sources of nitrous oxide are not  well  characterized, but most are probably related to soil



processes.








    Stabilizing  emissions  of  greenhouse  gases  at  current levels  will  not  stabilize




concentrations.  Once  emitted, greenhouse gases remain in the atmosphere  for decades  to




centuries. At current emission levels, greenhouse gases are being released into the atmosphere faster



than they are being removed.  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 (ppm) by 2100, compared with about 350 ppm



today,  and about 290 ppm 100 years ago (Figure 4).  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.








    Drastic  cuts in emissions would be required to stabilize  atmospheric composition as shown in



Table 1 (see also, Box 1), and  even if all anthropogenic  emissions of  COj, 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, for the oceans to absorb enough carbon to reduce



the atmospheric concentration of  CO2 half way toward  its preindustrial value.  It would lso take



more than 50 years  before  excess  concentrations for CFCs and N2O declined by  half after  all



anthropogenic emissions were eliminated.
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                              Executive Summary
                                 FIGURE 4


             IMPACT OF C02 EMISSIONS REDUCTIONS

               ON ATMOSPHERIC CONCENTRATIONS
                              (Parts Per Million)
       500
       475  -
       450  -
   o
   _J
   ^  425

   DC
   UJ
   Q.
   V>
       400  -
        375  -
        350  -
        325
          1985   2000
2025
   2050

YEAR
2075
2100
Figure 4. 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.
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                                         TABLE 1

                     Approximate Reductions in Anthropogenic Emissions
              Required to Stabilize Atmospheric Concentrations at Current Levels
                          GAS	REDUCTION REQUIRED

                          Carbon Dioxide (CO2)          50-80%
                          Methane (CH4)                10-20%
                          Nitrous Oxide (N2O)           80-85%
                          Chlorofluorocarbons (CFCs)     75-100%
                          CO, NOs	Freeze	
                                          BOX1

                                     Greenhouse Gases

       Carbon dioxide.  Carbon dioxide (CO,) 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 snow an increase from 315 to 350
   parts per million by volume (Figure 1), Carbon dioxide concentrations ate currently increasing
   at a rate of about 0.4% per year, which is responsible lor about itall of current Increases In
   commitment to global warming from greenhouse gas buildup (Figure 3).  Both deforestation
   and fossil-fuel combustion have contributed to this rise.  Current emissions are estimated at
   5.5 bfllioa  tons of carbon (Pg  C) from fossil-fuel  combustion and  0,4-2,6 Pg C from
   deforestation.  Most of this carbon dioxide remains in the atmosphere- or is absorbed by the
   oceans.  Even though only about half of current emissions remain in the atmosphere, available
   models  of COa uptake by the ocean  suggest that  substantially more  than a 50% cut in
   emissions is required to stabilize concentrations at current levels;

       Methane.  The concentration of methane (CH4) has more titan doubled daring the last
   three  centuries.  Methane, which:  is currently  increasing  at a rate  of 1% per year, is
   responsible for  about T% of current increases in commitment to global warming.  There i&
   consider able uncertainty about the sources of methane, and the observed Increase is probably
   due to incjteases & a luteW of sources as  well as to change* k tropospheric chemistry.
   Increases in agricultural sources, particularly rice cultivation  and animal husbandry,  have
   probably been the most significant factor, but emissions from landfills and coal seams could
   play an important role in the future.   Of the major greenhouse  gases only methane
   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 this lifetime remains constant and that natural emissions
   do not change.  Whether this is the case will depend on changes in tropospheric chemistry as
   influenced by emissions of hydrocarbons and carbon monoxide, among others, and on whether
   global climate change itself affects methane emissions.
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                      The concentration of nitrous oxide (N2O) has increased by 5-10% since
   preindustrial times.  The cause of this increase is highly uncertain, but it appears that the use
   of nitrogenous fertilizer, land clearing, biomass burning, and fossil-fuel combustion nave all
   contributed. Each additional molecule of nitrous oxide has over 200 times as much impact
   on climate as additional molecules of carbon dioxide, and nitrous oxide  can also contribute to
   stratospheric ozone depletion.  Nitrous oxide is currently increasing at a rate of 0.25% per
   year, which represents an imbalance of about 30% between total emissions and  total losses.
   Nitrous oxide increases are responsible for roughly 6% of current increases Jn commitment
   to global warming.  Assuming that the observed increase in NjO concentrations is due to
   anthropogenic sources and that natural emissions have not changed* then aft 80-85% cut in
   anthropogenic emissions would be required to stabilize N2O at current levels.

       Hajpcarbons.  Chlorofluorocarbons (CFCs), currently the most important halocarbons,
   were introduced into the atmosphere for the first time during this century. The most common
   species are CFC-12 (CCy?^ and CFG-11 (CCIjF)> which had atmospheric concentrations in
   1586 of 392 and 225 parts per trillion by volume, respectively. While these concentrations are
   tiny compared with that of CO,, CFCs have as much as 20,000 times moire impact oa climate
   per additional molecule  and are increasing very rapidly-more than 4% per year since 1978.
   A focus of attention because of their potential to deplete stratospheric ozone, the increasing
   concentration of CFCs also represents about 15% of current increases i commitment to global
   warming*  For CFC-11  and CFC-12, cuts of 75% and 85%, respective^, of current global
   emissions would be required to stabilize concentrations. However because of growth in other
   compounds, in order to stabilize the total greenhouse Warming potential from all halocarbons,
   a phaseout of the fully halogenated compounds (those that do not contain hydrogen), a freeze
   on the use of methyl  chloroform^ and  a limit on the emissions of partiafly  halogenated
   substitutes would be required.

       Other gases influencing composition.  Emissions of carbon monoxide (CO) and nitrogen.
   oxides (NO*), among 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 stabilised,
   it might only be necessary  to freeze emissions of the short-lived gases at current levels to
           atmospheric composition,
    In preparing this  report,  EPA  did  not develop  scenarios that  achieve  zero  change  in

concentrations, instead we have focused on promising options that can significantly slow the rate of

greenhouse gas buildup and climatic change.
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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.







    The magnitude of future global warming will depend, in part, on how geophysical and biological



feedbacks enhance  the warming caused by  the additional infrared radiation absorbed by increasing



concentrations 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 climatic 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 preindustrial  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.







          If nothing else changed in the Earth's climate system except the doubling



           of CO2 (or the  equivalent in other  greenhouse  gases), average  global



           temperature would rise 1.2-1.3C.








          A strong scientific consensus exists that increased global temperatures would



           raise atmospheric levels of water vapor and change the vertical temperature








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            profile, raising the ultimate global warming caused by a doubling of CO2 to



            1.8-2.5C, if nothing other than these factors changed in the Earth's climate



            system.   Changes in snow and  ice cover are also expected to  enhance



            warming, raising the estimate  to 2-4C.







           General Circulation Models now generally project that the global  warming



            from doubling CO2 would cause changes in clouds that could enhance this



            warming to roughly 2.5 to  5.5C.  Uncertainties exist about this feedback,



            however.  There also exists the  possibility that the  cloud feedback will be



            negative and would diminish the warming somewhat, perhaps to 1.5'C.








           A variety of other  geophysical  and biogenic feedbacks exist that have



            generally been ignored 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.  When all such



            feedbacks are considered, it is possible that the actual climate sensitivity of



            the Earth could exceed 5.5C  for an initial doubling of CO2.







    Global wanning of just a few degrees would represent  a  enormous change  in climate.   The



difference in mean annual temperature between Boston and Washington is only 33C, and the



difference between Chicago  and Atlanta is 6.7C. The  total  global warming  since the peak of the



last ice age, 18,000 years ago, was only about 5C. That change  transformed the landscape of North



America; it  shifted the Atlantic ocean inland by about one-hundred miles, created the Great Lakes,



and changed the composition of forests  throughout the continent.
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    The potential future impacts of climatic change are difficult to predict and are beyond the scope



 of this report. 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



 findings of that study collectively suggest that the climatic changes associated with a global warming



 of roughly 2-4C would result in "a world that is different from the world that exists today.  Global



 climate change will have significant implications for natural ecosystems; for when,  where, and how



 we farm; for the availability of water to drink and water to run our  factories; 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."








 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 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



four scenarios of future patterns of economic development and technological change.  These scenarios



start with alternative assumptions about  the rate of  economic growth and policies that influence







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emissions.  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.







     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 technical change; the other,  called the Slowly Changing World



(SCW), represents a slower evolution of the world's economies. Two additional scenarios (referred



to as the "Stabilizing Policy" scenarios) start with the same economic and demographic assumptions,



but assume a world in which policies  to limit anthropogenic emissions have  been adopted.  These



scenarios are called the Slowly  Changing World with  Stabilizing  Policies  (SCWP) and the Rapidly



Changing World with Stabilizing Policies (RCWP).  An overview of the scenario assumptions is given



in Table  2.  In  all of the scenarios it  is assumed that the key national and international  political



institutions  evolve gradually, with no major upheavals.







    The various  assumptions that go into these scenarios are conceptually consistent, which leads to



partially offsetting impacts on greenhouse gas emissions.  For example, more rapid economic growth



in the RCW  compared to the  SCW scenario  is  assumed  to be  associated  with more  rapid



technological innovation  and replacement of older equipment,  which has higher greenhouse gas



emissions.  Similarly, rapid increases  in income  are assumed to be associated with  more  rapid



decreases in population growth rates.  In the Stabilizing Policy  scenarios it is assumed that  more



rapid reductions in greenhouse gas emissions per unit of activity are possible when economic growth



rates are higher. If such offsetting tendencies do not occur, and/or if economic growth is more rapid



than assumed in the  RCW and RCWP scenarios,  then the rate of greenhouse gas buildup would









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                           Executive Summary
                                        TABLE 2
                             Overview of Scenario Assumptions
            Slowlv Changing World
            Raoidlv Chanting 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
              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
            Rapidly 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 Phase-Out
              Rapid GNP Growth
          Moderated Population Growth
      Modest Energy Price Increases/Taxes
       Very Rapid Efficiency Improvements
         Rapid Solar /Biomass Penetration
              Rapid Reforestation
                CFC Phase-Out
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probably be higher than what is calculated for these scenarios.  Economic growth may also be lower



than is assumed in the SCW.







    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, some 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.  Our  procedure is to consider the major



economic and social  structures that determine the activities that give rise to trace-gas emissions.








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 climatic



change.   In this  scenario we assume that the aggregate level of economic activity (as measured by



GNP) increases relatively slowly on a global basis. Per capita income is stagnant for some time in



the developing regions that have very high population growth, with modest increases elsewhere.  Per



capita economic growth rates 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  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.   Because  of slack  demand, real  energy prices increase slowly.  Correspondingly, existing



capital stocks turn  over slowly and production efficiency in agriculture and industry improves at only
DRAFT - DO NOT QUOTE OR CITE        22                             February 21, 1989

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 Policy Options for Stabilizing Global Climate - Review Draft               Executive Summary






 a moderate rate.  The energy efficiency of buildings, vehicles, and consumer products also improve



 at a slow rate.







    In "A Rapidly Changing World" (RCW) rapid economic growth and technological change occurs



 with little attention given to the global environment. Per capita income rises rapidly in most regions



 and consumers demand increasing 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 occur due to 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 hi industrialized  countries and



 as industries such as steel, aluminum,  and auto-making grow in developing countries.  Population



 growth rates decline  more rapidly than hi 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.








    The No Response scenarios examined lead to substantial greenhouse gas buildup




and global  wanning.  The two worlds described  above lead to significant increases in carbon




 dioxide and trace gas emissions  (Table 3), large increases in greenhouse gas concentrations (Figure



5),  and substantial global warming.  Carbon dioxide concentrations reach twice their preindustrial



levels in about 2080 in the  SCW  scenario.   In the RCW this level is reached by 2055, and



concentrations more than  three  times  preindustrial values  are  reached  by 2100.    Methane



concentrations increase by almost a factor of 2 in the SCW and a factor of 2.6  in the RCW, with the







DRAFT - DO NOT QUOTE OR CITE        23                             February 21, 1989

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Policy Options for Stabilizing Global Climate - Review Draft
                           Executive Summary
                                        TABLES

                   Current and Projected Trace Gas Emissions Estimates

C02 (Pg Q*
sew
RCW
SCWP
RCWP
N20 (Tg N)b
sew
RCW
SCWP
RCWP
CH4 (Tg CH<)
sew
RCW
SCWP
RCWP
NO, (Tg N)
sew
RCW
SCWP
RCWP
CO (Tg C)
sew
RCW
SCWP
RCWP
CFC-12 (Gg)c
sew
RCW
SCWP
RCWP
CFC-22 (Gg)
sew
RCW
SCWP
RCWP
1985

5.9
5.9
5.9
5.9

11.3
11.3
11.3
11.3

514.4
510.5
514.4
510.5

53.3
53.2
53.3
53.2

502.3
502.0
502.3
502.0

363.8
363.8
363.8
363.8

73.8
73.8
73.8
73.8
2025

9.2
11.5
5.1
5.2

13.5
13.0
10.7
10.8

676.4
712.4
545.0
558.7

68.8
72.9
44.8
50.7

842.0
699.1
286.1
290.8

379.7
437.5
54.9
85.9

385.0
829.1
385.0
829.1
2100

11.4
25.5
3.1
4.5

12.1
15.0
10.7
10.9

815.9
1,089.0
484.7
508.0

70.1
118.2
42.6
43.8

603.5
1,207.1
250.9
244.9

410.8
493.1
66.0
86.6

794.8
2,795.6
794.8
2,795.6
1 1 Pg C = 1 billion metric tons of carbon.
b 1 Tg N = 1 million metric tons of nitrogen.
c 1 Gg = 1 thousand metric tons = 1 million kilograms.
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24
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   Policy Options for Stabilizing Global Climate - Review Draft
                    Executive Summary
                                        FIGURES
u 600
                      ATMOSPHERIC CONCENTRATIONS
                            (3.0 Degree Celsius Climate Sensitivity)
              CARBON DIOXIDE                                 METHANE
                (Parti Pr Million)
    1*86  2000     2025     20EO    207S    2100
                   VEAR
                                              3000
                                                             (Prt Per Billion!
 1985 2000    2026    2050    2076    2100
               VEAR
             NITROUS OXIDE
              (Prtf Pr Billion)
    1985 2000    2025    2060     2076     2100

                  VEAR
      CHLOROFLUOROCARBONS
      (Prli Pr Trillion o< CFC-12 Equivalent)
                                                      I	I	I	I
1986  2000    2025    2060    2076    2100
                YEAR
  DRAFT - DO NOT QUOTE OR CITE        25
                      February 21, 1989

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Policy Options for Stabilizing Global Climate - Review Draft                Executive Summary






most rapid growth occurring between 1985 and 2050.  The combined greenhouse effect of CFCs



increases to a greater extent, reaching 4.2 times 1985 levek by 2100 in the SCW and 6.5 times 1985



levek in the RCW, despite  assuming that  at  least  65% of developing countries and  95% of



industrialized countries participate in the Montreal Protocol to control emissions of these compounds.



Nitrous oxide concentrations also increase significantly,  primarily as a result of the current imbalance



between sources and sinks.  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.  These results are hi good agreement with recent studies that



have made less formal estimates based primarily on current trends in concentrations and/or emissions.



A notable exception is CFCs, for which we expect significantly lower concentrations as a result of the



recent Montreal  Protocol to control production of these compounds (see Production and Use of



Halocarbons).








    Even  the Slowfy Changing  World  scenario  is  calculated  to produce a 2-3C




temperature increase  during the next century.  In the SCW scenario, realized global warming




would increase by  1.0-1.5C between 2000 and 2050 and by 2-3C from 2000 to 2100  (temperature



ranges are based on a climate sensitivity of 2-4C unless otherwise noted; see Box 2; Figure 6).  The



maximum realized  rate of change associated with this scenario is 0.2-03C per decade, which occurs



sometime in  the  middle of the next century.   The total equilibrium  wanning commitment  is



substantially higher, reaching 3-6C by 2100 relative to preindustrial levels.








    Higher rates of economic growth are certainly the goal of most governments and  could lead to



higher rates of climatic change as illustrated by the RCW scenario. Compared with the SCW, the



rate of change during the next century would be more  than 50% greater in the RCW:  In the RCW



realized global warming  increases by 1.2-1.9C between 2000 and 2050, and by 3-5C between 2000
DRAFT - DO NOT QUOTE OR CITE        26                            February 21, 1989

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Policy Options for Stabilizing Global Climate - Review Draft
                              Executive Summary
                                 FIGURE 6



                         REALIZED WARMING

                      NO RESPONSE SCENARIOS


                (Degrees Celsius; 2.0 - 4.0 Degree Climate Sensitivity)
        5  \-
        4 |_
    UJ
    o   3
    v>
    UJ
    111
    cc
        2 J_
        1  (-
       1985      2000
2025
    2050


YEAR
2075
2100
 Figure 6. Shaded areas represent the range based on an equilibrium climate sensitivity to doubling

 C02 of 2-4C.
 DRAFT - DO NOT QUOTE OR CITE        27
                                  February 21, 1989

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Policy Options for Stabilizing Global Climate - Review Draft               Executive Summary
                                         BOX 2

                         Equilibrium and Realized Warming

   Equilibrium Warming Commitment

   The equilibrium warming commitment  for  any  given year is the eventual  increase in
   temperature that would occur at some point  in the future if atmospheric concentrations of
   greenhouse gases were to remain constant at that year's levels.

   Realized Warming

   Because the oceans have a large  seat  capacity  the temperature change realized in the
   atmosphere  lags considerably behind  the  equilibrium level (the difference  between the
   equilibrium wanning and the realized warming in any given year is called the unrealized
   warming}* Realized warming has been estimated with a simple model of ocean heat uptake.


   CBmale Sensitivity :

   Because the response of the climate system to changes in greenhouse gas concentrations is
   
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Policy Options for Stabilizing Global Climate - Review Draft               Executive Summary






The  Impact of Policy Choices








    Government policies  could significantly decrease or increase future warming. The




warming 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



is locked in, there is a wide range of possibilities.  It is prudent to begin to understand what impact



alternative economic development strategies  might have on future warming.








Scenarios with Stabilizing Policies








    Two alternative scenarios were constructed to  explore the impact of  policy choices aimed at



reducing the risk of  global wanning.   These  scenarios,  labelled Slowly Changing World with



Stabilizing Policies (SCWP) and Rapidly Changing World with Stabilizing Policies (RCWP) start with



the same economic and demographic assumptions used in 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 (which already assume  substantial efficiency improvements).  We also



assume  that efforts to  expand the use  of natural gas increase  its  share of primary energy supply



relative  to other fossil fuels in the near  term.  Research and development  investments in 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.



As  a  result, non-fossil energy sources meet  a  substantial fraction of total demand in later periods.



The existing protocol to reduce CFC and halon emissions is assumed to be strengthened,  leading to



a phase-out of fully-halogenated compounds  and a freeze on methyl chloroform. A global effort to











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Policy Options for Stabilizing Global Climate - Review Draft                Executive Summary





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.







    While the same general emissions reduction  strategies are assumed in  both  the SCWP and



RCWP  cases, the  degree  and speed of improvement are higher in the RCWP scenario because



technological innovation and capital stock replacement  are greater in this  case.  The policies



considered in these scenarios do not require changes in basic life styles. 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, the automobile efficiency assumptions are not inconsistent with the size



distribution of the  current  vehicle fleet.








    The impact of these policy assumptions is a substantial reduction in the rate of greenhouse gas



buildup,  but not  a  complete stabilization  of  the  atmosphere (Figure  5).    Carbon  dioxide



concentrations increase gradually  throughout  the time  frame of the  analysis despite declining



emissions, reaching a level  65% greater than preindustrial values by 2100, or approximately one-third



higher than  current levels.  Methane concentrations increase through about  2025,  after which they



level off and decline to roughly 1985 levels by 2100.  Weighted CFC  concentrations also increase



rapidly at first, but they are relatively stable after about 2010. Nitrous oxide concentrations increase



by an amount 40-50% less than the amount of increase in the  RCW and SCW cases.








    The  calculated  rate of climatic  change  in  the  Stabilizing Policy scenarios  is




between 0.6 and 1.4C per century,  or at  least 60%  less than in  the  corresponding




worlds  without a policy response to potential climatic change. Global temperatures in the




SCWP case increase by 0.4-0.8C from 2000 to 2050 and 0.6-1.1C from 2000 to 2100; corresponding



values are 0.5-0.9C and 0.8-1.4C in the RCWP case (Figure 7). Total equilibrium warming






DRAFT - DO NOT QUOTE OR CITE         30                            February 21, 1989

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 Policy Options for Stabilizing Global Climate - Review Draft
                       Executive Summary
                                 FIGURE 7
                         REALIZED WARMING:

       NO RESPONSE AND STABILIZING POLICY SCENARIOS

                  (Degrees Celsius; 2.0 - 4.0 Degree Climate Sensitivity)


         Slowly Changing Scenarios                 Rapidly Changing Scenarios
 V)

 ut
 o
 w
 ut
 o
 Ul
  1985 2000  2025  2050  2075   2100


                 YEAR
                                               I
                                                                J_
     1985 2000 2025  2050  2075  2100


                    YEAR
Figure 7. Shaded areas represent the range based on an equilibrium climate sensitivity to doubling

C02of2-4C.                                                              S
DRAFT - DO NOT QUOTE OR CITE
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February 21, 1989

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Policy Options for Stabilizing Global Climate - Review Draft                Executive Summary






commitment reaches 1.4-2.8C by 2100 in the SCWP case and 1.7-3.3C in the RCWP case, assuming



the climate sensitivity is 2-4C.  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 even the Stabilizing Policy scenarios could lead to extremely high climatic



change. It is also possible that the policies assumed in these scenarios could limit climatic change



to about 1"C if the true climate sensitivity of the Earth is low.








    If the risk of substantial climate change associated with the SCWP and RCWP scenarios is judged



to be unacceptable, more aggressive policies will be required. Therefore we have constructed a Rapid



Reduction case that examines the  effect of measures that might be imposed  to supplement  those



measures already  analyzed in the RCWP scenario.  This case implies that strategies that rapidly



reduce greenhouse gas emissions are adopted beginning in 1990 (see below).  In this scenario realized



wanning is limited to less than 2C and  the warming trend is reversed in the middle of the next



century. All of the scenario estimates for realized and equilibrium  wanning are tabulated in  Table



4 (including the results of an "Accelerated Emissions" scenario defined below).








The Relative Impact of Various Options  On Future Warming








    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 climatic change when combined.  This is illustrated in Figures 8 and 9, which show the




impact of  the key measures that account for the difference between the  RCW, RCWP, and  Rapid



Reduction cases.  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









DRAFT - DO NOT  QUOTE OR CITE         32                           February 21, 1989

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Policy Options for Stabilizing Global Climate - Review Draft
                           Executive Summary
                                       TABLE 4

                  Scenario Results For Realized And Equilibrium Warming
                                  (Degrees Centigrade)
Realized Warming - 2C Sensitivity
Accelerated Emissions
RCW
sew
RCWP
SCWP
Rapid Reduction
Realized Warming - 4C Sensitivity
Accelerated Emissions
RCW
sew
RCWP
SCWP
Rapid Reduction
Equilibrium Wanning Commitment - 2C Sensitivity
Accelerated Emissions
RCW
sew
RCWP
SCWP
Rapid Reduction
Equilibrium Warming Commitment - 4C Sensitivity
Accelerated Emissions
RCW
sew
RCWP
SCWP
Rapid Reduction
1985
0.5C
0.5
0.5
0.5
0.5
0.5
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
1.5
1.5
1.5
1.5
1.5
1.5
2000
o.rc
0.7
0.7
0.6
0.6
0.6
2000
1.0
0.9
0.9
0.9
0.9
0.9
2000
1.1
1.1
1.0
1.0
1.0
1.0
2000
2.2
2.1
2.1
2.0
1.9
1.9
2025
1.5C
1.2
1.1
0.9
0.9
0.8
2025
2.1
1.7
1.7
1.4
13
13
2025
2.4
1.7
1.6
1.3
1.2
1.1
2025
4.7
3.5
3.3
2.5
2.4
2.1
2050
2.8C
1.9
1.6
1.1
1.0
0.8
2050
4.1
2.8
25
1.8
1.7
1.4
2050
4.3
2.7
2.2
1.5
1.3
1.0
2050
>6
5.4
4.5
2.9
2.7
2.0
2075
45C
2.7
2.0
1.3
1.2
0.8
2075
>6
4.1
3.2
2.1
1.9
13
2075
>6
3.8
2.7
1.6
1.4
.9
2075
>6
>6
5.4
3.2
2.8
1.7
2100
>6C*
3.6
2.5
1.4
1.2
0.7
2100
>6
5.6
4.0
2.3
2.0
1.2
2100
>6
4.8
3.1
1.7
1.4
.7
2100
>6
>6
>6
3.3
2.8
1.3
* Estimates of warming greater than 6C represent extrapolations beyond the range tested in most
 climate models.
DRAFT - DO NOT QUOTE OR CITE
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   Policy Options for Stabilizing Global Climate - Review Draft             Executive Summary


                          STABILIZING POLICY STRATEGIES:

                DECREASE IN EQUILIBRIUM WARMING COMMITMENT
              a
 1. CFC Phaseout
 2. Reforestation
 3. Improved Transportation

     Efficiency0
 4. Other Efficiency Gains
 5. Energy Emissions Fee9
 6. Promote Natural Gas
                  9
  7. Emission Controls
  8. Solar Technologies
  9. Commercialized Blomass
 10. Agriculture, Landfills,

     and Cement
 11. Promote Nuclear
           k
     Power
                            Percent Reduction Relative to RCW Scenario
RCWP (Simultaneous

 Implementation of 1-11)
                                                                2050
                       2100
                                           10       15

                                               Percent
                    20
25
                                         65%
    Figure 8. 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.
    DRAFT - DO NOT QUOTE OR CITE
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                                                                  February 21, 1989

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 Policy Options for Stabilizing Global Climate ~ Review Draft                Executive Summary


                                    FIGURE 8 - NOTES

                      Impact Of Stabilizing Policies On Global Warming

 " 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 in developing countries.

 b 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 per year.

 c The average efficiency of new cars in the U.S. reaches 40 mpg (5.9 liters/100 km) by 2000.  Global
 fleet-average  automobile efficiency reaches 50 mpg  by 2025 (4.7 liters/100 km).

 d The rate of energy efficiency improvements in the residential, commercial, and industrial sectors
 are increased about  0.1-0.2  percentage pobts  by 2025  compared to the RCW, and about 03-0.4
 percentage points annually from 2025-2100.

 ' Emission fees are placed on fossil fuels  in proportion to carbon content.  Maximum production
 fees (1985$)  were $0.50/GJ for coal,  $036/GJ for oil, and  S023/GJ  for natural gas.  Maximum
 consumption  fees were 28% for coal, 20% for oil,  and  13%  for natural gas.  These fees  increased
 linearly from zero, with maximum consumption fees charged by 2025 and maximum production fees
 charged by 2050.

 ' Assumes that economic incentives  accelerate  exploration and production of natural gas, reducing
 the cost  of locating  and producing natural gas by an annual rate of .5% relative to the RCW
 scenario.  Incentives  for gas use for electricity generation increases gas share by 5% in  2025 and
 10% thereafter.

 1 Assumes more stringent NOX and CO controls on mobile and stationary sources including all gas
 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 uses oxidation catalysts  from 2000 to 2025); 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 NOX 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  NOX burners after 2000.

 h Assumes that low-cost solar technology is available by 2025 for  as little as 4.6 cents/kwh.

 1 Assumes the cost of  producing  and  converting biomass to modern fuels reaches  $4.00/gigajoule
 (1985$) for gas and $6.00/gigajoule (1985$) for liquids.  The maximum  amount of liquid or gaseous
 fuel available from biomass is 210 exajoules.

' 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 due to policies aimed
 at reducing waste and landfill gas  recovery; emissions in developing countries continue to grow until
2025 then remain flat  due to incorporation of the source policies. Technological improvements reduce
demand for cement by 25%.
DRAFT - DO NOT QUOTE OR CITE         35                            February 21, 1989

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Policy Options for Stabilizing Global Climate - Review Draft               Executive Summary


                            FIGURE 8 - NOTES (Continued)

                     Impact Of Stabilizing Policies On Global Wanning

k Assumes that the cost of nuclear technology declines by 0.5% per year.

1 Impact on 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 - Review Draft
                       Executive Summary
                    RAPID REDUCTION STRATEGIES:
ADDITIONAL DECREASE IN EQUILIBRIUM WARMING COMMITMENT
  1. Carbon Fee
  2. Consumption Tax
  3. High MPG Cars
  4. High Efficiency
     Buildings d
  5. High Efficiency
    Powerplants8


  6. High Blomass
  7. Coal Phaseout
               g
  8. Rapid Reforestation

Rapid Reduction Scenario

  (Simultaneous
  Implementation of 1-8)
                                   Additional Percent Reduction
                                    Relative to RCW Scenario
                                                             2050
                                                             2100
                                         10
           15
20
25
                                           Percent
 Figure 9.  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.
 DRAFT - DO NOT QUOTE OR CITE
37
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Policy Options for Stabilizing Global Climate - Review Draft               Executive Summary


                                   FIGURE 9 - NOTES

                   Impact Of Rapid Reduction Policies On Global Warming

1 High carbon emissions fees are imposed on the production of fossil fuels in proportion to the CO2
emissions potential. In this case, fees of $8.50/GJ were imposed on unconventional oil production,
$5.70/GJ on coal, $2.30/GJ on oil, and $1.10/GJ on natural gas.  These fee levels are specified in
1985$ and are phased in over the  period between 1985 and 2050.

b A percentage  excise tax, proportional to  the carbon content of the  fuel,  was  levied on fuel use.
Consumption taxes were also imposed in the RCWP case.  In this case, the tax on coal consumption
was increased from 28% of the  price to 40%; the tax on oil use was  increased  from  20% to 30%;
the tax on natural gas use was increased from 13% to 20%; the tax  on electricity use was increased
from 0 to 5%.  These taxes were  phased in and fully applied by 2025.

c 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.

d 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.

" Assumes that, by 2050, average power plant conversion efficiency improves by  50% relative to the
RCWP case.  In this  scenario the design efficiencies  of all types of generating plants  improve
significantly.  For example,  by 2025, oil-fired generating stations  achieve an  average  conversion
efficiency roughly equivalent  to that achieved by combined-cycle units  today.

' 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 half relative
to the assumptions in the RCWP  case.

g Environmental fees of about $20/GJ  (in  1985$) are phased in by 2050.  This  has the effect of
gradually making coal uncompetitive in  utility markets.

h 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.

1 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.
DRAFT - DO NOT QUOTE OR CITE         38                            February 21, 1989

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Policy Options for Stabilizing Global Climate - Review Draft                Executive Summary


                                         TABLES

                       Examples Of Policy Responses By The Year 2000

RCWP  Case

     New automobiles in the U.S. average 40 mpg

     New automobiles in the OECD use 3-way catalytic converters to reduce CO and NO, (current
      U.S. standard); 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

     Emission fees are placed on fossil fuels in proportion to carbon content~$2.50/ton on coal,
      $0.50/barrel on oil, $0.05/thousand cubic feet on  natural gas

     Research and development into solar photovoltaic technology allows solar to compete with oil
      and natural gas (DOE long-term policy goals)

    Available municipal solid waste and agricultural wastes are converted to useful energy

    Biomass  energy plantations  increase  current productivity by 65% (to 25  dry tons/hectare
      annually)

Rapid Reduction Case

     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 undertaken

    CFCs are phased out; production of methyl chloroform is frozen

    Emission fees are placed on fossil fuels in proportion to  carbon content~$29/ton on coal,
     $3.25/barrel on oil, $0.25/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
DRAFT - DO NOT QUOTE OR CITE        39                             February 21, 1989

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Policy Options for Stabilizing Global Climate - Review Draft               Executive Summary






reducing greenhouse gas emissions.  These policies are meant to illustrate potential policy responses;



a variety of policy combinations might achieve the reductions in global warming estimated in each



case.








    This  analysis  suggests   that  accelerated  energy  efficiency   improvements,   reforestation,



modernization of biomass use, and carbon emissions fees could have the largest impact  on the rate



of climatic change over the next few decades.  In the long run, advances in solar technology and



biomass  plantations  also play an essential role.  The measures that reduce the wanning to  the



greatest extent in the Rapid Reduction case relative to the RCWP case are those that change the fuel



mix  For example, imposing stiff carbon fees on the  production of fossil fuels,  and increasing the



assumed level of biomass availability.  Table 4 indicates that only the most aggressive policy case



ensures that the rate of warming will be below a tenth of a degree Celsius per decade.  This is still



about twice the average rate of wanning experienced over the last century.








    Because of the large potential for growth in their emissions, the participation  of




developing countries is crucial for stabilizing greenhouse gases.  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' contributions in greenhouse gas emissions also rise to about 50% in the SCW  (Figure 10).



We examined the implications for global warming if industrialized countries adopted climate stabilizing



policies without the participation of developing countries.  Stabilizing policies adopted by industrialized



countries, however,  are likely to affect the development path  of other countries  even if these other



countries do not  explicitly adopt such policies.  Therefore, we assumed that technological diffusion







DRAFT - DO NOT QUOTE OR CITE        40                             February 21, 1989

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Policy Options for Stabilizing Global Climate - Review Draft
          Executive Summary
                                  FIGURE 10

      SHARE OF GREENHOUSE GAS  EMISSIONS BY REGION
                   sew
                  SCWP
              2026    2060
                   VEAR
                                   (Percent)
     1986 2000   2026    2050    2076    2100
                           207C    2100
                                                         RCW
                                                                        Other Developing
                                                                         Chin, k CP Aii
                                                                         USSR  CP Europe
                                                                         Reil of OECD
                                                                         United Stetes
                                          1986 2000    2025    2050    2075    2100
                                                        RCWP
202S    20CO
    VEAR
DRAFT - DO NOT QUOTE OR CITE        41
            February 21, 1989

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Policy Options for Stabilizing Global Climate - Review Draft               Executive Summary






would result in energy efficiency improvements in developing countries at a rate between the rates



assumed in the No Response and Stabilizing Policy cases.  Some other factors, such as when the



cost of solar energy becomes competitive in developing countries, were also assumed to be between



the assumptions in these two scenarios.  With these assumptions, equilibrium warming commitment



in 2050 is about 40% higher compared to the scenarios with global cooperation (Figure 11). 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 warming remains.








   Delaying  the policy response to  the  greenhouse gas buildup would substantially




increase the global commitment to future  warming.  The Stabilizing Policy cases and the




Rapid Reduction case both assume that starting in 1990 action is taken to begin reducing  the rate



of greenhouse gas buildup, and that significant policies are in force by 2000.  It has been suggested



that any response should be  delayed until the current level of scientific uncertainty is substantially



reduced. The impact of such a course was investigated by assuming 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 hi the Stabilizing Policy cases.



The  result is a significant  increase in global warming  (Figure 12):   The  equilibrium warming



commitment in 2050 increases by about 40% compared to the scenarios  with policy implementation



beginning in 1990.








    Government policies could also significantly exacerbate climate change. 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 possibility is illustrated by a set of tests that were  conducted  starting with the



RCW scenario.  In this "Accelerated Emissions" case, several key parameters were varied as proxies
DRAFT - DO NOT QUOTE OR CITE         42                            February 21, 1989

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 Policy Options for Stabilizing Global Climate - Review Draft
                                                     Executive Summary
                                  FIGURE 11
                 INCREASE IN REALIZED WARMING

    WHEN DEVELOPING COUNTRIES DO NOT PARTICIPATE

                 (Degrees Celsius; Based on 3.0 Degree Sensitivity)
         SLOWLY CHANGING WORLD
                                       RAPIDLY CHANGING WORLD
2  3
w

UJ
o
M
UJ
UJ

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 Policy Options for Stabilizing Global Climate - Review Draft
                                                 Executive Summary
w
|  3
W
o
V)
5  2
                                  FIGURE 12
                 INCREASE IN REALIZED WARMING
          DUE TO GLOBAL DELAY IN POLICY ADOPTION
                  (Degrees Celsius; Based on 3.0 Degree Sensitivity)
          Slowly Changing World
                                    Rapidly Changing World
                           SCW
Global Delay
                          SCWP
                                         4 -
                                                                 RCW
                                                    Global Delay  /
                                                                  RCWP
  1985 2000  2025  2050   2075  2100    1985 2000  2025   2050  2075  2100
                 YEAR                                   YEAR
 Figure 12. 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.
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 Policy Options for Stabilizing Global Climate - Review Draft               Executive Summary








 for  currently  proposed  policies  (e.g.,  accelerated  development of  synfuels)  or  the possible



 consequences of government inaction or failure (e.g., high use of CFCs and deforestation).







    Figure 13 summarizes the results of these tests  as  compared with the RCW scenario.  The



 results are illustrated in terms of the incremental effect of each policy outcome on the equilibrium



 warming commitment in 2050 and 2100.   Figure 13  indicates that the measures that amplify the



 warming to the greatest extent are those that reduce the rate of efficiency improvement, 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 on the result in 2100. The impact of all of these policies in combination could be to increase



 the equilibrium warming commitment in 2050 by 60% compared with the RCW scenario.








 Sensitivity of Results to Alternative Assumptions








    Many factors could increase  or decrease future  warming.   The specific estimates of




 climatic change presented above are subject to a variety of uncertainties involving technological and



 economic assumptions as well as the response of the Earth-atmosphere system to perturbations.







    Many uncertainties regarding the response of the climate system, such as the role of clouds and



 sea ice changes, can be reflected by varying the climate sensitivity parameter. The results presented



 above were based on a  central estimate of 2-4C for  the equilibrium wanning from a doubling of



 the concentration of carbon dioxide.  Broadening  this range to  1.5-5.5C  has  one of the largest



impacts on estimates of future warming (Figure 14).  In the RCW scenario the range of realized



warming in 2050 increases from 1.9-2.8C  to  1.5-3.2C; the impact on equilibrium warming is much



greater, increasing the range of the commitment estimated in 2050 from 2.7-5.4C to 2.0-7.4C.









DRAFT - DO NOT QUOTE OR CITE        45                            February 21, 1989

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    Policy Options for Stabilizing Global Climate - Review Draft
Executive Summary
                                   FIGURE 13

                  ACCELERATED EMISSIONS CASES:
  PERCENT INCREASE IN EQUILIBRIUM WARMING COMMITMENT
 1. High CFC Emissions'
  2. Cheap Coal
 3. Cheap Synf uels
 4. Slow Efficiency
    Improvements'
 5. High Deforestation
  6. High-Cost Solar
 7. High-Cost Nuclear
Accelerated Emissions
  (Combination of 1-8)
                                Percent Increase From RCW Scenario
                                                              2050
                                                              2100
                      j	i   I  i   I   i  I   i   I  i   |   i   I  i   I   i
                   -10    0    10   20    30   40    50    60   70    80
                                            Percent
    DRAFT - DO NOT QUOTE OR CITE      46
  February 21, 1989

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Policy Options for Stabilizing Global Climate - Review Draft               Executive Summary
                                   FIGURE 13 - NOTES
                Impact Of Accelerated Emissions Policies On Global Warming


* 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
EPA's Regulatory Impact Assessment report.

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.

0 Assumes that  the price of  synthetic oil and gas could be reduced by 50% and commercialization
rapidly accelerated relative to the RCW case. This case assumes that the minimal production price
for synfuels can be achieved  in 20 years rather than the 30 years assumed in the RCW case.

d 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 efficiency improves at rates of
approximately 1-2% per year.  In the Slow Improvement  case the assumed rates  were reduced to
only 05-1.0% per year.  The lower rate of  improvement is similar to the assumptions  in recent
projections for the  Department of Energy's National Energy Policy Plan.

' Assumes annual deforestation increases at a rate equal to the rate of growth in population.

( Assumes that  solar  energy  remains  so expensive that the possibility of its making any significant
contribution to global energy supply is precluded.

* 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 $40 (1985$) per gigajoule (GJ) on the price of electricity supplied by nuclear power plants was
phased in by 2050.

h 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.
DRAFT - DO NOT QUOTE OR CITE        47                            February 21, 1989

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Policy Options for Stabilizing Global Climate - Review Draft
                     Executive Summary
                                FIGURE 14



             IMPACT OF CLIMATE SENSITIVITY ON
                        REALIZED WARMING
               (Degrees Celsius; 1.5-5.5 Degree Climate Sensitivity)
      Slowly Changing World Scenario
      Rapidly Changing World Scenario
                                            I
               I
I
                                                                     5.5
                                                                     4.0
                                                                     2.0

                                                                     1.5
 1985 2000  2025  2050  2075  2100   1985 2000   2025  2050  2075  2100
                  YEAR                                YEAR
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 Policy Options for Stabilizing Global Climate - Review Draft                Executive Summary








 There is a similar impact on warming estimates in the SCW.  The sensitivity of the results from the



 RCW scenario to a wide range of other assumptions has been tested; the results are summarized in



 Table 6.







    A variety of factors related  to technology, resources, and  emissions factors could significantly



 influence the projected warming.  Of these factors, the  largest impacts are  due to assumptions that



 affect the relative price of coal and non-fossil fuels in the future. If, in the absence of policies, non-



 fossil technology decreased in price much faster than we assumed  in  the RCW, or  coal prices



 increased much faster than we assumed in the RCW, then warming in 2100 could be as much as one-



 fourth lower than calculated for this scenario.  The impact of increasing the assumed availability of



 oil and gas was surprisingly low.  Larger supplies led to greater total demand and reductions in the



 share of energy supplied by coal and non-fossil fuels; these factors in combination left  greenhouse



 gas emissions and estimated wanning almost unchanged.  Had the assumed increase in gas availability



 been  coupled with policies  intended to encourage its use as a transition  fuel to a  non-fossil world,



 then a much larger impact  may have been seen.  Current sources of methane and nitrous oxide are



 quite  uncertain, but these uncertainties appear  to have only a modest impact on projected warming:



 up to 5% in the case of methane.








    The oceans and biosphere play  a major and highly uncertain role  in the climate




system.  Their ability to absorb CO2 and heat is a key determinant  of the rate and magnitude of




 climatic change (Table 6).   Alternative formulations of carbon dioxide absorption by the ocean and



 any other carbon sinks have a significant  impact on estimated climatic change.  A variety of ocean



 models with  very  different  structure produced  similar  estimates of  future  carbon  dioxide



concentrations, with  the  exception of the outcrop  (Siegenthaler)  model,  which  calculated lower



concentrations in 2100; if this model were correct, the equilibrium warming commitment in 2100









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Policy Options for Stabilizing Global Climate ~ Review Draft

                                      TABLE 6

                     Sensitivity Analysis:  Impact on Realized Warming
                               and Equilibrium Warming
                          (Percent change from RCW scenario)*
                                                                    Executive Summary
Sensitivity Case
 Assumptions
                                    2050
                                                                    2100
                           Realized
Equilibrium
Realized
                                             Equilibrium
TECHNOLOGY, RESOURCES, AND EMISSION FACTORS


                           -6 to -13%      -9 to -17%
Low Cost Non-Fossil
 Technology"
 -10



   1


-3 to 4
Fossil Resources

  High Coal Price6

  High Oil Supply"1

  High Gas Supply*

Alternative Starting
 Methane Budgets

N2O From Fertilizer

  High Emissions From
   Anhydrous Ammonia8

  High Emissions From
   Fertilizer Leaching"

High N2O From
 Combustion1

High Initial Biomass
 On Cleared Land"

OCEAN COZ AND HEAT UPTAKE

Alternative CO2 Modelsk

  Oeschger et al.1

  Bolin et al.m

  Bjorkstrom"

  Siegenthaler0
                -16 to -25%
                                            -3 to 5
                 -3 to 5
                                              -3

                                              -3

                                              -3

                                              -3
                -19 to -26%
-14
<-l to 1
1
-23
-1
-26
-2
                  -3 to 5

0 to
-0.1

0
-0.1
to 0
2
0
0 to -0.1
0 to 0.1
2
0
0
0
1
0
0
0
1
                                    -4

                                    -4

                                    -4

                                    -12
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                              February 21, 1989

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Policy Options for Stabilizing Global Climate - Review Draft

                                  TABLE 6 (continued)

                     Sensitivity Analysis:  Impact on Realized Warming
                                and Equilibrium Warming
                           (Percent change from RCW scenario)*
                           Executive Summary
Sensitivity Case
Assumptions
Alternative Unknown
Sink Assumptions'9
Heat Diffusion Rateq
2C Sensitivity
4C Sensitivity

Realized

-7 to 3

-17 to 11
-23 to 17
ATMOSPHERIC CHEMISTRY MODEL
CFC-11 Lifetime'
Chlorine/Col O3
Parameter"
Trop O3/CH4
Parameter'
OH/NO, Parameter"
FEEDBACKS
Ocean Circulation
Surprise"
2C Sensitivity
4C Sensitivity
CH< Hydrate and Wetland
Emissions*
2C Sensitivity
4C Sensitivity
Ocean Mixing, CH4
Emissions, Terrestrial
Biota"
2C Sensitivity
4C Sensitivity
-0.1 to 0.1
-4
1
-1 to 1


0
49

10
15

19
33
2050
Equilibrium

-8 to 3

0
0
ASSUMPTIONS
-0.1 to 0.1
-6
1
-2 to 1


0
4

11
16

14
31

Realized

-13 to 3

-14 to 9
-21 to 16

-0.1 to 0.1
-8
1
-2 to 1


35
62

12
18

22
43
2100
Equilibrium

-14 to 3

0
0

-0.1 to 0.1
-8
1
-2 to 1


4
11

12
19

15
33
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Policy Options for Stabilizing Global Climate - Review Draft                Executive Summary

                                         TABLE 6 - NOTES

*   The percent changes are  independent of the assumed climate sensitivity except where noted.

b   These ranges represent modest to optimistic assumptions about future commercial availability of
    non-fossil  technologies, e.g., solar photovoltaics, advanced nuclear power designs, and synthetic
    fuel production from biomass.  Solar photovoltaic costs decline to 4.6 cents/kwh (1985$) by 2020
    in the optimistic scenario and by 2050 in the modest assumptions.  Nuclear costs decline at an
    annual rate of 0.5% in the optimistic assumptions  and remain relatively flat in  the  modest
    assumptions compared to an  overall growth of 1.5 cents/kwh assumed in the RCW scenario.
    Assumes  that  the  cost  of  producing and  converting  biomass  to  modern fuels  reaches
    $4.00/gigajoule for gas and $6.00 (gigajoule) for liquids by 2020 in the optimistic assumptions and
    by 2050 in the modest assumptions.  The total amount of fuel available  from biomass is 210
    exajoules.

0   The impact of an escalation hi coal prices above the RCW case by about 1% annually from 1985
    to 2100.

d   The impact of an increase in  global oil resources to 25,000 exajoules, more  than double  the
    estimate in the RCW case, assuming proportionate increases in resource availability at each cost
    level.

"   The impact of an increase in global natural gas resources to 27,000 exajoules, more than 25
    times the estimate in the RCW case, assuming proportionate increases in resource availability at
    each cost level.

'   These  ranges represent  assumptions  about  the relative  sizes  of  anthropogenic  versus non-
    anthropogenic sources of methane emissions thereby affecting growth in  emissions over time,  i.e.,
    high  emission levels (373 Tg CH4)  from anthropogenic activities such as fuel production and
    landfilling with low emission levels (137 Tg CH4) from natural processes such as oceans and
    wetlands, versus low anthropogenic emissions (245 Tg CH4) with high natural emissions  (265 Tg
    CH4).

8   The impact of elevating the emission coefficient for the anhydrous ammonia fertilizer type (the
    percent of N evolved as N2O) from 0.5% to 2.0%.

h   The impact of assuming additional N2O emissions from fertilizer leaching into surface water  and
    ground water, modeled by increasing all the fertilizer emission coefficients by 1 percentage point.

1   The impact of higher emission coefficients for N2O from combustion; assumes that N2O emissions
    are about 25% of NO, emissions, thus the N2O  emissions from  combustion sources  in 1985
    equaled 2.3 Tg N, over two times the level assumed in the RCW case.

J    The impact of assuming a higher estimate for  the amount of carbon initially contained in forest
    vegetation and soils (roughly a 50-100% increase) and a more rapid rate of change in land use,
    resulting hi carbon emissions of 281 Pg  from 1980 to 2100 compared with 188 Pg C in the RCW
    scenario.

k   Realized warming was  not calculated in these tests.

1    This box-diffusion model represents the turnover of carbon below 75 meters as  a purely diffusive
    process.
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Policy Options for Stabilizing Global Climate - Review Draft                Executive Summary

                               TABLE 6 - NOTES (continued)

m   This is a 12-compartment regional model which divides the Atlantic and Pacific-Indian Oceans
    into surface-, intermediate-, deep-, and bottom-water compartments and divides the Arctic and
    Antarctic Oceans into surface- and deep-water compartments.

"   This is an advective-diffusive model that divides the ocean into cold and warm compartments;
    water downwells directly from the cold surface compartment into intermediate and deep  layers.

0   An outcrop-diffusion model that allows direct ventilation of the intermediate and deep oceans
    in high latitudes by incorporating an outcrop connecting all sublayers to the atmosphere.

p   These ranges represent the impact of alternative assumptions about the "unknown carbon sink"
    that absorbs the unaccounted-for carbon in the carbon cycle.  Two sensitivities were analyzed:
    1) a high case,  where the size of the unknown sink increases at the same rate as atmospheric
    CO2 levels  compared with preindustrial levels; and 2)  a low case, where the size decreases to
    zero exponentially at 2%  per year.

q   Heat diffusion in the oceans is modeled as a purely diffusive process.  To capture some of the
    uncertainty regarding actual  heat uptake, the base case eddy-diffusion coefficient of 0.55x10"*
    m2/sec was increased to  2x10"* and decreased to 2xlO"5 m /sec.   Climate sensitivity  had a
    measurable effect on these results, so this impact is illustrated as  well.

'    The atmospheric lifetime of CFC-11, 65 years b the RCW case, was varied from 55 to 75 years.
    Increases or decreases in the  atmospheric concentration of CFC-11, however, tend to  be offset
    by corresponding decreases or increases in atmospheric concentrations of other trace gases,  such
    as other CFCs and CH4.

'    The amount  of stratospheric  ozone  depletion  due to the chlorine contained  in CFCs  was
    increased from 0.03% to 0.20% decline in total column ozone/(ppb)2 of stratospheric  chlorine.

'    The rate at which tropospheric ozone  forms as a result of CH4 abundance is estimated with a
    parameter in the atmospheric composition model.  In the RCW case, this  variable for the
    Northern Hemisphere is a 2% change in tropospheric ozone for each percentage change in  CH4
    concentration; it was changed to 0.4% in the sensitivity analysis.

u    Tropospheric OH formation is affected by the level of  NOX emissions.  A 0.1% OH change for
    every 1% change in NO, emissions for the Northern Hemisphere was assumed in the RCW case;
    in the sensitivity analysis,  a range of 0.05% to 0.2% was evaluated.

v    For  this  analysis we assumed  that a 2C increase in  realized  warming would alter ocean
    circulation patterns sufficiently to shut off net uptake of CO2 and heat by the oceans.

w   We assumed that with each 1C increase in temperature, an additional 110 Tg CH4 from methane
    hydrates, 12 Tg  CH4 from bogs, and 7 Tg CH4 from rice cultivation would be released annually.

*    This case  illustrates the combined impact of several  types of biogeochemical feedbacks:  1)
    methane emissions  from hydrates,  bogs, and rice cultivation (see footnote above); 2) increased
    stability of the thermodine, thereby slowing the rate of heat and CO2 uptake of the deep ocean
    by 30% due to less mixing; 3)  vegetation albedo, which  is a decrease in global albedo as a result
    of changes in the distribution of terrestrial ecosystems by 0.06% per 1C warming; 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 1C warming; and 5) CO2 fertilization, which is an increase in the amount
    of carbon stored in the biosphere in response to higher CO2 concentrations by 0.3 Pg C per ppm.


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would be 12% lower than the estimate for the RCW scenario.  If higher CO2 concentrations greatly



fertilize the biosphere (removing some CO2 from  the  atmosphere), the equilibrium  warming



commitment in 2100 could be reduced by as much  as 14%.  In our highly simplified model of the



ocean,  heat uptake is controlled by a single diffusion parameter.  Adjusting this parameter over a



wide but plausible range of values has a large impact on the rate of warming, decreasing the warming



realized in 2100 in the RCW scenario by 14-21% or increasing it by 9-16% (for a climate sensitivity



to doubled CO2 of 2-4C).








    A speculative, but potentially important suggestion, is that the role of the  oceans could change



suddenly as one  consequence  of  climatic change.   To provide a preliminary indication of the



importance of this potential feedback process we have examined a hypothetical case in which warming



by 2C triggers a change in ocean circulation that prevents the ocean from absorbing any additional



CO2 or heat. The result is a dramatic increase in realized wanning by 40 to 60% in 2100.  Also



quite uncertain, but potentially important, are a number of other biogeochemical feedback processes,



such as release of methane contained in near-shore ocean sediments, changes in surface reflectivity



due to shifts in vegetation zones, and changes in biospheric carbon storage. Taken together, these



feedback processes could strongly amplify climatic change, increasing realized warming in 2100 by 20-



40% (assuming the climate sensitivity to doubled CO2 is 2-4C) (Table 5).








EMISSIONS REDUCTION  STRATEGIES BY ACTIVITY








    Many   individually modest sources  are  in  combination  responsible  for  the




greenhouse gas buildup.   Anthropogenic emissions of greenhouse gases can be categorized as




arising from energy production and use, industrial activity (including the use of CFCs), agricultural



practices, and changes in land-use  patterns (including deforestation) (Figure 15).  It is useful to
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Policy Options for Stabilizing Global Climate - Review Draft
                         Executive Summary
                                  FIGURE 15
       ACTIVITIES CONTRIBUTING TO GLOBAL WARMING
         Energy Use
       and Production
          (57%)
                CFCs
                (17%)
                                                              Other Industrial
                                                                  (3%)
                                                                Agricultural
                                                                 Practices
                                                                   (14%)
                                                         Land Use
                                                       Modification
                                                          (9%)
Figure 15. Estimated contribution to greenhouse warming for the 1980s, based upon each activity's
share of greenhouse gas emissions, weighted by the greenhouse gas contributions to global warming
shown in Figure 3.
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Policy Options for Stabilizing Global Climate - Review Draft                Executive Summary






examine current and potential future emissions and technical and policy options available for reducing



emissions in each of these sectors individually.








Energy Production  and Use








Past. Present, and Future Emissions








    The largest single factor affecting greenhouse gas emissions is the consumption of energy from



carbon-based fossil fuels.  Between  1950 and 1985 annual global primary energy consumption grew



from 80 to 290 exajoules (EJ),2 and  annual CO2 emissions grew from 1.6 to 5.2 petagrams of carbon



(Pg C).3 These CO2 emissions are the dominant reason for the increasing atmospheric concentrations



shown  in Figure  1.  Even though  emissions have  been relatively stable during  the last decade,



atmospheric concentrations have  continued their  steady rise  because CO2  emissions  remain



substantially greater than  uptake by the oceans  and  any other sinks.








    The almost four-fold  increase in energy consumption during the last 35 years was accompanied



by a significant shift in its global distribution.  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 percent, and developing



countries, 6 percent. 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  share to 32  percent and 15 percent, respectively.
    2 One exajoule = 1018 joules =  0.95 quadrillion British Thermal Units  = 0.95 Quad.




    3 One petagram = 1015 grams.




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    Developing  and Eastern Bloc Countries are potentially large  sources of future

 emissions. Growth in energy use is driven almost entirely by countries outside the OECD in all

 of the scenarios developed for this study. The OECD share of primary energy consumption falls to

 25% by 2100 in the SCW and to as  little as 17% in the RCW.4  Growth in demand outside the

 OECD nonetheless drives up global energy demand significantly in these scenarios. Total end-use

 energy demand increases from 220 EJ in 1985 to 320 EJ in 2025 in the SCW versus 420 EJ in the

 RCW.5



    Greater improvements in energy efficiency in the SCWP and RCWP  cases reduce end-use

 demand in 2025 by 13%  and 15%, respectively, relative to the No Response scenarios.   End-use

 demand in the Rapid Reduction scenario is 20% lower than in the RCW by 2025.  Increases in

 energy efficiency account  for about one-fourth of the wanning reduction in the RCWP versus the

 RCW case in 2050.



    While policies  affecting demand  will  have  the  largest  impact  on  near-term

greenhouse gas  emissions, changes  in  the supply mix are also critical in  influencing

 emissions over the  long term.  Global primary energy supply is shown by source for the four

 scenarios in Figure 16. Growth in primary energy consumption is substantially higher than growth

 in end-use energy demand because of increased  requirements for electricity  and synthetic  fuel

 production, which involve  substantial conversion losses.  This is most dramatic in the RCW, where
    4 Primary energy includes conversion losses, such as in electricity and synfuels production.  The
primary energy  equivalent of nuclear, hydro, and solar electricity is calculated on the  basis of the
average efficiency of fossil-fuel-fired power plants.

    5 End-use energy is based on final consumption, with electricity valued at 3.6 megajoules per
kilowatt-hour.

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Executive Summary
                                   FIGURE 16

                 PRIMARY  ENERGY SUPPLY BY TYPE
                                   (Exajoules)
                    SCW                                 RCW
       1986 2000    2025    20EO   2075    2100
       198S 2000    2026    20SO   2076    2100
                                                      202E    20EO    207S    2100

                                                          RCWP
                                                                          Reduction From
                                                                           No A**pons
                                                                           Scenario
                                                                  2076    2100
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primary energy consumption increases from 290 EJ in 1985 to 580 EJ in 2025 and 1410 EJ in 2100;



a 100% and 380% increase, respectively, compared with 90% and 260% increases in end-use demand.








    Carbon dioxide emissions could grow  by a factor of 2 to 5 during the next century




if Stabilizing policies are not adopted.  Heavy reliance on coal in both the SCW  and  RCW




scenarios leads to  large increases in both  CO2 and CH4 emissions.  In the SCW, energy-related



emissions of CO2 increase from 5.1 petagrams of carbon (Pg C) in 1985 to 7.2 Pg C in 2025 and 10.8



Pg C in 2100.  Emissions reach more than  twice this level in the RCW scenario: 10.1 and 24 Pg C



in 2025 and 2100, respectively.  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 this source increases to



86 Tg CH4 in 2025 and 160 Tg CH4 in  2100.  The corresponding values for the RCW  are 130 Tg



CH4 in 2025 and 360 Tg CH4 in 2100, about 20 and 30% of the total, respectively.








    Technical options are  available that,  if adopted,  could stabilize  carbon dioxide




emissions. The combination of higher efficiency and greater reliance on non-fossil fuels assumed




in the Stabilizing Policy scenarios substantially curtails CO2 and CH4 emissions.  In both  the SCWP



and RCWP cases, CO2 emissions from energy use reach only 5.5 Pg C in 2025, after which time they



decrease, reaching 3.2 and 4.3 Pg C by 2100 in the two cases, respectively.  Similarly, CH4 emissions



from fuel production remain relatively constant in both of these scenarios. Increased reliance on non-



fossil fuels in the RCWP is  responsible for about one-fourth of the reduction in  warming in this



scenario relative to the RCW in 2050.
    6 1 teragram  = 1012 grams.




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    Despite the large range of outcomes illustrated by the four scenarios discussed here, none of the



global rates of change are unprecedented (Table 7).  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.   Reductions  in the amount  of  carbon



emitted per unit  of energy consumed  (carbon intensity) varies  from  0.0  to  1.3% per year with



significant declines only apparent in the Stabilizing Policy cases. These values are not unprecedented,



as carbon intensity declined by an average of 1.5% per year between 1925 and 1985 due to increased



reliance on oil and gas in preference to coal (but coal is expected to regain  market share in the



future in the absence of policy changes).








    Energy-related emissions, other than of CO2 and CH4, 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



NOZ 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 or Inter-cooled Steam-Injected Gas Turbine



technology in utility and industrial  applications after 2000, with developing countries following after



2025.  Emission controls account for about 4% of the 2050 warming reduction in the RCWP relative



to the RCW.








Energy Technologies to Reduce Greenhouse Gas Emissions








    The introduction of technologies  and practices that use less energy  to accomplish




a given task will have the  largest impact  on global wanning in the near term.  We







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                          Executive Summary
                                      TABLE 7



                        Key Global Indicators for Energy and CO2
Parameter
GNP/capita
(1000 1988$)
Primary Energy
(EJ)

Fossil Fuel CO2
(PgC)


GNP/capita
(%/yr)
Energy/GNP
(%/yr)

Fossil Fuel COj/Energy
(%/yr)

Scenario 1985
SCW, SCWP 3.0
RCW, RCWP
SCW 290
RCW
SCWP
RCWP
SCW 5.1
RCW
SCWP
RCWP

SCW, SCWP
RCW, RCWP
SCW
RCW
SCWP
RCWP
SCW
RCW
SCWP
RCWP
2025
3.7
6.7
430
580
380
520
7.2
103
55

1985-2025
0.5
2.0
-1.1
-1.6
-13
-1.9
-0.1
0.0
-05
-1.3
2100
7.1
35.6
680
1410
550
940
11.1
24.4
32
4.3
2025-2100
0.9
2.3
-0.8
-1.4
-1.0
-1.8
-0.0
-0.0
-1.2
-1.1
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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). We list below examples of potential efficiency



improvements that can be made in the various sectors of the economy.








    Transportation -  A number  of technologies have already been demonstrated that could



    increase automobile fuel efficiency from current levels for new cars (25-33 mpg or 9.4-7.1



    liters/100 km) to  better than 50 mpg (4.7 liters/100 km); these technologies may pay for



    themselves hi  fuel savings over  the  lifetime of the vehicle.  Further improvements can



    increase fuel efficiency to more than 80 mpg (less than  3 liters/100 km), although they do



    not appear to be cost effective at current U.S. gasoline prices.  The RCWP scenario assumes



    that new cars in the industrialized countries achieve an average of 40 mpg (5.9 liters/100 km)



    by 2000. Global fleet average fuel efficiency reaches 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: new vehicles achieve an average of 50 mpg (4.7 liters/100



    km) by 2000.








    Residential and  Commercial -  Improved 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 new homes could technically be built that use only 10% of current average



    energy requirements.  About 20% of U.S. electricity is consumed for lighting, mainly in



    residential and commercial  buildings.  A combination  of currently available  advanced









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    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 is as much as 75%



    for fuel and 50% for electricity in the U.S.  Smaller improvements are assumed in other



    regions and in the SCWP scenario.








    Industrial Energy - Advanced industrial processes are available that can significantly reduce



    the energy required to produce basic materials.  This is especially true when combined with



    recycling.  For example, new technology developed in Sweden uses about half as much energy



    per unit of steel production as the current U.S. average.  Electric motors are estimated to



    account for about  70% of U.S.  industrial electricity use.  Several case studies  show that



    improved motors and motor controls are commercially available, which could reduce energy



    consumption by electric motors by at least 15% relative to current averages.








    Developing  countries can also significantly  improve energy  efficiency.  Per capita




energy consumption is very low in developing countries, but 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. Some of the technical options described



above may be directly applicable in  developing as well  as industrialized countries, while alternative



approaches suited to available resources will often be needed. In many cases improved management



of existing facilities could have large payoffs.








    Research  on non-fossil energy technologies  is a critical  need.  The development of




attractive non-fossil energy sources is critical to the success of any climate stabilization strategy over



the long term.  Increased penetration of solar  and advanced biomass technologies contribute little to







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reduced wanning in 2025, but they are responsible for 24% of the difference between the RCWP and



the RCW case in 2050,  and  over  30%  of this difference  in 2100.  The exact  mix of non-fossil



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.







    Hydro and Geothennal Power - 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 sites are limited and environmental and social impacts of large-



    scale projects must be considered carefully. Hydroelectric and geothermal power expands



    to  12% of global primary energy production in the SCWP scenario, but only maintains a



    roughly constant  share of the higher level of production in the RCWP case.








    Biomass Energy - 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 accounts of commercial energy use.  Current  and emerging technologies



    could vastly improve  the efficiency of biomass use.  In  the near term there is a substantial



    potential  to  obtain  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.  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



    21% of primary  energy needs in 2050 and 35% in 2100. Biomass  supplies  about 30% of



    primary energy by 2050 in the RCWP  scenario.









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    Solar Energy - There is a large range of solar options. Direct use of solar thermal energy,



    either passively or in active systems, is already commercial for many water and space heating



    applications.  Wind energy systems are also currently commercial for  some applications in



    some locations.   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. In the SCWP scenario solar sources of electricity



    are  equivalent to 9% of primary energy supply from 2050 onward.  A larger contribution is



    envisioned in the RCWP scenario:  15% in 2050, increasing to almost 20% in 2100.








    Nuclear Power  Nuclear fission produces about 5% of global primary energy supplies and



    its share is currently growing due to the completion of powerplants ordered during the 1970s.



    High cost and concerns about  safety, nuclear proliferation,  and radioactive waste disposal,



    however, have brought new orders 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  in  restoring public



    confidence in this energy source.  Nuclear power's contribution to primary energy supply



    increases to 8% in 2050 and 14% in 2100 in the SCWP case and 13% in 2050 and 20% in



    2100 in the RCWP case.
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Energy Policy  Options








    No  single policy approach by itself is likely to be both effective and acceptable as a means of



achieving  substantial reductions  in  greenhouse gas emissions from  energy production  and use.



Strategies appropriate for developing countries, for example, may be quite different from those that



are appropriate for the United States.  However, many complementary policy options are available



that offer differing relative advantages for reducing emissions.








    Proper pricing  of energy services may be most important.  It is  critical to  encourage both



increases in end-use efficiency and the development  of energy sources that emit no CO2.  Current



market prices of fossil fuels do not reflect the risk of climatic change and provide no assurance that



limiting greenhouse gas emissions will be a consideration in purchase and investment decisions.  A



direct means of providing  incentives  to  reduce  emissions  is to impose a fee on fossil fuels in



proportion to  their relative contribution to global  wanning.   Regulatory programs may  be  an



important complement when pricing  strategies are not effective, either because of market failures or



because  of inequitable  impacts  on  some  regions  or income groups.   Directing research  and



development priorities toward energy sources that emit no CO2 is essential to assure the availability



of attractive options over the longer  term.  Other important policy options include the selective use



of government procurement to stimulate markets and promote technological alternatives, and technical



assistance and information programs.








Industrial Activity








    Three significant non-energy  sources of greenhouse gases are associated with industrial activity:



the release of halocarbons during their production and use; methane emissions from waste disposal



in landfills; and carbon dioxide emissions from cement manufacture.







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Production and Use  of Halocarbons








    Chlorofluorocarbons,  halons,  and  chlorocarbons  (collectively,  halocarbons)  are man-made



chemicals containing carbon, chlorine, fluorine,  and bromine (HCFCs contain hydrogen as well).



Table  8  lists the major halocarbons with  their  chemical formulae and  major uses.  CFCs were



originally commercialized in the 1930s as non-toxic, non-flammable, and highly stable coolants for



refrigerators. They were  first used as propellants during World War n,  and as blowing agents for



foam products during the 1950s.  CFCs  are also  used in gas sterilization  of medical equipment and



instruments, solvent cleaning of manufactured parts, and miscellaneous other processes and products



such as liquid food freezing.  Halons were developed in the 1970s and  are used primarily as fire



extinguishants.   Chlorocarbons are  used primarily  as  solvents  and chemical  intermediates.  The



primary chlorocarbons are carbon tetrachloride and  methyl chloroform.   Production of halocarbons



has grown rapidly as  new uses have  developed.








    Halocarbons  have  been  identified  as a serious threat  to the stratospheric ozone layer.



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 when



"The Montreal Protocol on Substances That Deplete the Ozone Layer" (or the Montreal Protocol)



to reduce the use of CFCs and halons  was initialed.   The Montreal Protocol came into force  on



January 1,  1989, and has been  ratified by 31 countries, representing over 90% of  current world



consumption of these chemicals  (as of January 11, 1989).








    Further reductions  in CFCs  would be needed to stabilize 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







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                          Executive Summary
                                      TABLES

                  Major Chlorofluorocarbons, Halons, And Chlorocarbons:
                                  Statistics And Uses
Chemical
Chlorofluorocarbons
CFC-11 (CFC13)
CFC-12 (CF2Clj)
HCFC-22 (CHClFj)
CFC-113 (CjCljFj)
1986
Atmospheric
Concentration
(pptv)
226
392
-100
30-70
Atmospheric
Lifetime
(Years)
+32
75
-17
+289
111
-46
20
90
Current Annual
Atmospheric
Concentration
Growth Rates Major
(%/yr) Uses
4 Aerosols,
Foams
4 Aerosols,
Refrigeration
7 Refrigeration
11 Solvents
Halons (Bromofluorocarbons)
Halon-1211 (CBrCtty
Halon-1301 (CBrF3)
Chlorocarbons
Carbon tetrachloride
(ecu
Methyl chloroform
2
2

75-100
125
25
110

-50
5.5-10
> 10 Fire
extinguisher
> 10 Fire
extinguisher

1 Production of
CFC-11 and
CFC-12
7 Solvents
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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 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



5). Despite assuming that at least 65% of developing countries and 95% of industrialized countries



participate in the agreement, the total contribution of halocarbons to the greenhouse effect increases



by more than a factor of 4 in the SCW and by a factor of 6.5 in the RCW scenario by 2100.







    Promising chemical substitutes, engineering controls,  and process modifications have now been



identified that could eliminate most uses of CFCs.  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).   Even under these assumptions



total weighted halocarbon concentrations increase significantly from 1985 levels in part because the



chemical substitutes contribute significantly to greenhouse forcing,  but 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 6% of the decrease



in wanning in the RCWP compared with the RCW in 2050.








Waste Disposal








    Landfills are a small but potentially controllable source of methane. Waste disposal in  landfills



and open dumps generates methane when decomposition of the organic material becomes anaerobic;



approximately 80  percent of  urban solid wastes is currently disposed of in one  of  these  ways.








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Landfilling (compaction of wastes, followed by daily capping with a layer of clean earth) is most



common in industrialized countries, while open pit dumping is the most common "managed" disposal



method in developing countries (30-50% of solid wastes generated in  cities in developing countries



is currently uncollected).  Most of the decomposition in landfills and some of the decomposition in



open pits is anaerobic, resulting in annual methane emissions of 30-70 Tg CH4, about 10% of the



total source.








    Disposal of municipal solid waste in industrialized nations increased by 5%  per year during the



1960s, and by 2% per year in the 1970s.  Landfilling is  not  expected to increase very much in



industrialized countries in the future, but  it 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 growth of landfill methane emissions 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- and five-fold increase



in methane emissions in  the SCW and RCW scenarios, respectively,  reaching 13-15% of the total



methane budget by 2100.  The Stabilizing Policy scenarios assume that gas recovery systems and waste



reduction policies will be adopted, resulting in roughly constant global emissions from landfills.








Cement Making








    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.  Generally,  even more CO2 is emitted from the fuel



used to drive the process (these combustion emissions are 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 130 million tons in 1950 to about one billion tons currently. Thus, current








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CO2 emissions from calcining are 0.14 billion tons of carbon (0.14 Pg C).  The share of global



production in  industrialized countries has declined during this period, and this  trend is expected to



continue because demand in these countries is saturating.  Emissions of CO2 from cement making,



projected using the per capita income approach described in the Waste Disposal section, increase by



two- to three-fold in the SCW and RCW scenarios by the year 2100.  (Emissions remain less than



0.5 Pg C/yr in all cases.)   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 by



about a factor of 2.








Changes  in  Land Use








    Deforestation and biomass burning are significant sources of COj, CO, CH4, NOC and N2O.



Globally, the  world's forest and woodland areas have been  reduced by about 15%  since 1850,



primarily to accommodate the expansion  of cultivated lands.  The largest  decreases 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.  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.



Recent  analysis of remote  sensing data  from Brazil,  however, suggest  that in 1987, 8 Mha were



cleared in the  Brazilian Amazon alone.  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 0.4-2.6 Pg C, almost entirely from tropical countries.  This accounts for approximately 10-



30% of annual anthropogenic CO2 emissions  to the atmosphere. Of the  estimated net release of



carbon from tropical deforestation in 1980 about half was from Brazil, Indonesia,  Colombia, the



Ivory Coast, Thailand, and Laos.
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    Biomass burning, related to deforestation, shifting cultivation, burning agricultural waste, and



fuelwood use, contributes roughly 10-25% of total annual  CH< emissions, 5-15% of N2O emissions,



15-30% of NOX emissions, and 20-35% of the CO emissions.  In addition, biomass burning and land



clearing results in elevated biogenic emissions of NO, and  N2O from the soil for an extended period



after the burn.








    Most tropical forests could be lost during the next century.  The causes of deforestation




are complex and vary from country to country, making 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 continued poverty,  unsustainable



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 for  this scenario.  Under this assumption the  rate of tropical deforestation



increases from  11 million hectares per year  (Mha/yr) in 1980 to 34  Mha/yr  in 2047, when the



available area of forests in Asia  is exhausted.  As a result, CO2 emissions from deforestation increase



rapidly from 0.7 Pg C/yr to more than 2 Pg C/yr in  2047 before the Asian forests are exhausted.



Latin American and African forests are exhausted by 2075, reducing emissions drastically (Figure 17).







    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, before the  unprotected forest areas  of Latin America are



exhausted.   Total  emissions are almost  the same as in the SCW, but  they are spread out over a



longer  period.   Emissions are close to 1 Pg C/yr from 2000 to 2100.
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              CO2 EMISSIONS FROM DEFORESTATION


                         C02 From Deforestation
                               (Petagrams Carbon)
       - (a)
 o
 m
 cc.
 
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    Reforestation is a potentially cost-effective means of reducing net carbon dioxide emissions.  In



the Stabilizing Policy scenarios it is assumed that the biosphere is transformed from a source to a



sink for carbon by 2000.  A combination of policies succeed in stopping deforestation by 2025 while



up to 1000 Mha is reforested by 2100.  Forests reach their peak absorption of 0.7 Pg C/yr before



2025. (The land area required  depends on the productivity of the reforested land.  We have used



a conservative estimate; if the productivity were higher,  then less than 1000 Mha would be required



or the maximum sink would be more than 0.7 Pg C/y.)  The size of this sink declines gradually after



2025 as  forests reach their maximum size and extent. 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.  In addition, some fraction of the fallow agricultural



land in the temperate zone (250 Mha), planted  pasture in Latin America  (100 Mha),  and degraded



land in Africa and Asia (400 Mha) is assumed to be reforested.  Of the reforested  land, about 380



Mha is assumed to be in plantations, which is sufficient to produce the biomass energy requirements



of the RCWP case with the productivity goals established by the Department of Energy.








    Reversing deforestation could be a very cost-effective policy response  to potential




climatic  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 extremely low  in comparison to other options.   Furthermore, a



reforestation strategy could offer a stream of valuable ecological and economic benefits in addition



to reducing CO2 concentrations, such  as forest  products, maintenance of biodiversity, watershed



protection, nonpoint pollution reduction,  and  recreation.  Devising  successful forestry programs



presents unique challenges to scientists and policy makers 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







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 enormous impact on forestry. Reforestation accounts for almost one-fifth of the decrease in warming



 by 2050 in the RCWP versus the RCW scenarios.








 Agricultural Practices








    Three  agricultural activities contribute to atmospheric  concentrations of greenhouse gases in



 addition to those that have been discussed regarding changes in land use:  enteric fermentation in



 domestic animals; rice cultivation; and nitrogenous fertilizer use.








    Methane emissions from  animals may increase significantly over the next century.




 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. The highest CH4 losses are reported for ruminants (e.g., cattle, dairy cows, sheep,



 buffalo, and goats) in which 4-9%  of total energy intake is released as methane.  Of the annual



 global source of 400 to 600 Tg CH4, domestic animals contribute approximately 65-85 Tg.  Of these



 emissions  approximately 57% comes from cattle and 19% from dairy cows.  The  domestic animal



 population has increased considerably during the last century.  Between the early 1940s and 1960s,



 increases in global cattle populations averaged 2% per year.  Since the 1960s, the rate of increase



 has slowed somewhat, to  1.2%.  By comparison, the average annual increase  in global human



 population since the 1960s has been about  1.8%.  Future demand for agricultural products  will



 depend more on population than on income levels.  Based on a global agriculture model, methane



 emissions  from enteric fermentation are estimated to increase by about 125% from 1985 to 2100 in



 both the SCW and the RCW scenarios  as the much higher incomes in the RCW largely offset the



 somewhat  higher populations in the SCW.
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    Methane emissions from rice cultivation are likely to increase more slowly.  Methane produced



by anaerobic decomposition in flooded rice fields escapes to the atmosphere by bubbling up through



the water column, diffusing across the water/air interface, and 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, and fertilizer use. Rice fields are estimated



to contribute 60-170 Tg CH4 per year to the atmosphere, or approximately 10-30% of the global flux.



This large range reflects a paucity of data,  particularly from Asia, where 90% of rice cultivation



occurs.  From 1950 to 1984, 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 hectare.  Methane emissions are



probably primarily a  function of area under  cultivation  rather than  yield, although  yield  could



influence emissions, particularly if more organic matter is incorporated into the paddy soil  The land



area used for rice production, and thus the CH4 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%).








    Nitrous  oxide is released through microbial processes in soils, both through denitrification and



nitrification.  The use of nitrogenous fertilizer enhances N2O fluxes since some of the applied N is



converted to N2O and released to the atmosphere.  The amount of N2O released varies greatly and



depends on rainfall,  temperature, the type of  fertilizer applied,  mode of application, and soil



conditions.  Approximately 70 million  tons (70 Tg)  of nitrogen were applied in  the form  of



nitrogenous fertilizers worldwide in 1984-85. A preliminary estimate suggests that this produced N2O



emissions  of 0.14-2.4 Tg N out of the global source of 11-17 Tg  N per year.  Satisfying the demands



of increasing populations with a finite amount of land  requires more intensive cultivation resulting



in a 160% increase in fertilizer use between 1985 and 2100 in both the SCW and RCW scenarios.








    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








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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 implementation of these options 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, fertilizer use is



assumed to shift  away from those types with the highest emissions after 2000.  The result of these



assumptions is substantially lower agricultural emissions in the policy scenarios relative to the No



Response scenarios. Emissions grow by less than a factor of 2 in all cases, and methane emissions



from rice remain roughly constant until 2075, after which time they fall by about 20% as the global



population stabilizes. Reduced emissions from agriculture, landfills, and cement manufacture accounts



for 10% of the reduced warming in the RCWP compared with the RCW scenario in  2050.








THE NEED FOR POLICY RESPONSES








    The prospect of global climate change presents policy makers with a unique challenge.  The



potential scale of the problem is unprecedented.  Many choices are available and the  consequences



of these choices will be profound.








    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
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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.








A Wide Range  of Policy Choices








    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. 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.








          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 necessary to



           impose  emission fees on  these  sources  according  to their  relative



           contribution to global warming in order to  accomplish this goal.  This would



           also raise revenues that could finance other programs.  The degree to which



           such fees are accepted will vary among countries, but acceptability would be



           enhanced if fees were 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







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            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.







           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.  Other policy options



            include  redirecting research  and  development priorities  in  favor  of



            technologies that could reduce greenhouse gas  emissions,  information



            programs to build understanding of the problems  and solutions, and the



            selective  use  of  government  procurement  to  promote  markets for



            technological alternatives.








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








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strategies that involve widespread and long-term shifts in technological development.  In this situation



it  may appear to be prudent to delay action to stabilize 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.








    Policy development and implementation can be a lengthy process, particularly at




the  international level  Any decision to respond to  the greenhouse gas buildup cannot be




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 fundamental components of the global




economy (transportation, heating and cooling buildings, industrial production, land clearing, etc.), such



that reducing  emissions by curtailing  these activities would be highly  disruptive and  undesirable.



While a large menu of promising technologies  have been identified 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 for



innovative technologies to be brought  to market is unpredictable, but is usually 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  can be higher in rapidly developing countries,  and may be










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influenced by government policies, once industrial infrastructure is built, it will be many years before



it is replaced.








   Industrialized and developing countries could limit the buildup of greenhouse gases




in a  manner consistent  with  economic development and  other environmental and




social goals.   The justification for policies that reduce greenhouse gas  emissions may be much




greater than it would appear from a narrow examination of costs and climatic benefits.  Most of the



measures proposed to  reduce emissions ~ increasing energy efficiency, reversing deforestation, and



reducing use of CFCs, for example -- are already of substantial public interest; global wanning is



often simply another reason for promoting these policies. Many energy efficiency measures are cost-



effective, but a number of institutional barriers and  market failures would need to be overcome  to



facilitate their  adoption.  Benefits include reductions in conventional pollutants, increased energy



security, and reductions  in the balance of payments deficit, as well as reduced risk of wanning.



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.  Reductions



in CFC production beyond those called for in the Montreal  Protocol would probably be most



significant  in reducing  the risk of stratospheric ozone depletion,  and would also make an important



contribution to reducing the  risk of climatic change. Some of the options discussed here, such  as



reduced agricultural emissions, improved biomass production, and heavy reliance on photovoltaics



would require  further research and development  to  assure their  availability.   Relatively  small



investments in  such research could yield important payoffs.  The incremental cost of taking actions



to limit  global warming today may therefore be modest.








   The OECD countries can play  a leadership role  in bringing about reductions  in




emissions by  Other countries.  Despite great differences between the OECD countries and other









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countries in sources of emissions and the economic and social constraints on policies to limit them,



initiatives by the U.S. and OECD countries can have a significant global impact.  U.S. leadership has



made important contributions to recent international environmental agreements such as the Montreal



Protocol on substances that deplete the ozone layer and the Tropical Forest Action Plan. The U.S.



is committed to playing a leadership role in the Intergovernmental Panel on Climate Change recently



organized  by  the World  Meteorological  Organization  and  the   United Nations  Environment



Programme.  Finally, the U.S. can use its bilateral aid and its influence in multilateral development



banks to encourage economic development consistent with reducing the buildup of greenhouse gases.







    In contrast to the common notion that limiting global wanning would require great sacrifices, we



find that many of the policy options that are available for reducing greenhouse gas emissions appear



to be attractive in many respects.   Policies  to begin  reducing greenhouse gas  emissions must be



carefully considered now, notwithstanding the many uncertainties, because the risks of delaying action



appear to be large, and the costs of reducing emissions are likely to  increase as the time allowed for



these reductions is shortened.
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                                      FINDINGS
I.   Uncertainties regarding  climatic change  are  large,  but there is a  growing
consensus in  the scientific community  that  significant  global warming due to
anthropogenic greenhouse gas emissions is probable over the next  century, and
that rapid climatic  change is possible.

          A scientific  consensus has emerged that greenhouse gases are increasing in
           concentration in the  atmosphere, that, even with a freeze in emissions
           concentrations will continue to increase, and that, as a result, warming and
           climate change are likely to occur.

          Uncertainties about  global warming abound.  The greatest uncertainties
           concern the ultimate  magnitude and timing of wanning and the implications
           of that warming for the Earth's climate system, environment, and economies.
           The warming that can be expected for a given increase in greenhouse gas
           concentrations is uncertain due to our inadequate understanding of the
           climate  system.  For  the  benchmark  case  of  doubling carbon dioxide
           concentrations from preindustrial levels, the equilibrium increase in global
           average temperature  would most likely be in the range of 2-4C, and could
           be as little as 1.5C or as much as 5.5C.

          A variety of geochemical and biogenic processes  that could significantly
           affect the response of the climate system to greenhouse gas increases have

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           generally been neglected in estimating potential future wanning.  When all



           such feedbacks are considered, it is possible that the actual sensitivity of the



           Earth's climate system to increased greenhouse gases could exceed S.5C



           for an initial doubling of CO2.







          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.  Assuming that the climate sensitivity to doubling CO2 is 2-4C,



           the Earth  is already committed to a total  warming of about  0.7-1.50C



           relative to the preindustrial era.  The Earth has wanned by 03-0.7C during



           the last century, which is consistent with expectations given the uncertain



           delay caused by ocean heat  uptake.








          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 33C, and the total global wanning  since the peak of



           the last ice age, 18,000 years ago, was only about 5C.







          Global temperature  change estimates are only indicators for the rate and



           magnitude  of climatic  change.   Climatic changes  at  the regional  level



           associated with global wanning will vary in both magnitude and timing and



           changes in precipitation and other factors will be  as important as changes



           in temperature.
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II.  Measures undertaken to limit  greenhouse gas emissions would decrease  the
magnitude  and speed of global warming, regardless of uncertainties about  the
response of the climate  system.

          Scenario  analyses indicates that  greenhouse gas concentrations will show
           large increases whether the rate of future economic growth and technological
           change is rapid  (the  "Rapidly Changing  World")  or slow (the "Slowly
           Changing World").  Fossil fuel would play a relatively larger role in raising
           greenhouse gases in a Rapidly Changing World while agricultural activities
           and deforestation would play a relatively larger role for the Slowly Changing
           World.

          If no policies to limit  greenhouse gas  emissions  are  undertaken, the
           equivalent of a doubling of CO2 occurs between 2030 and 2040 in these
           scenarios.

          The  equilibrium  warming commitment for a Rapidly Changing  World
           without policies to limit greenhouse  gas emissions is estimated to be 1-2C
           by 2000,  3-5C by 2050,  and 5-10C by 2100 (assuming  that the climate
           sensitivity to doubling CO2 is  2-4C).  For a Slowly Changing World the
           equilibrium warming commitment is estimated to be 1-2C by 2000, 2-4C
           by 2050, and 3-6C by 2100.  Estimated warming commitments greater than
           5C may not be fully realized because  the strength of  some positive
           feedback  mechanisms may decline as the Earth warms.
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          The realized warming in a Rapidly Changing World, without policies to limit



           greenhouse gas emissions, is estimated to be 2-3C by 2050, and 4-6C by



           2100 (assuming that the climate sensitivity to doubling CO2 is 2-4C).  In



           a Slowly Changing  World realized warming is estimated to be about 2C



           by 2050 and 3-4C by 2100.








          The early application of existing and emerging technologies included in this



           study could lower the commitment to global wanning in 2025 by about one-



           fourth, and the rate of climatic change during the next century could be



           reduced by at least 60%.








          Although delaying action would allow time to increase knowledge of risks



           and refine the choice of policies, it could reduce the effectiveness of policy



           responses. If industrialized countries delay implementation of any response



           to global warming until 2010 and developing countries delay until 2025, the



           equilibrium warming commitment in 2050 could increase by 30-40%.







          Stabilizing the commitment to  global  warming  would require cuts  in



           emissions from  present levels  so significant that currently available and



           emerging technologies are insufficient to achieve this goal.  Consequently,



           stabilization would require very rapid introduction of existing and emerging



           technologies  and very significant investments in research and development



           for advanced technologies that reduce greenhouse gas emissions. With such



           action, equilibrium  wanning commitment might  peak at 1-2C in  2025 and



           realized warming may not exceed 1.4"C if the climate sensitivity to doubling



           CO2 is 2-4C.









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          If the  climate sensitivity of the Earth to increases in greenhouse gases is
           low, then early application of existing and emerging technologies to limit
           greenhouse gases could prevent an equilibrium  warming commitment of
           greater than  2C within a  century.   If, on the  other hand, the true
           temperature sensitivity of the  Earth  to doubling CO2 is 5.5C or even
           greater, then  without  very  rapid application of existing and emerging
           technologies and  development  of new  technologies,  the  Earth could  be
           committed to a global wanning of more than  3C by as early as 2010 even
           with application of many  existing and emerging technologies  to limit
           greenhouse gases.
III.  No  single country  or source will  contribute more  than a  fraction of the
greenhouse gases  that will warm the  world;  any overall  solution  will require
cooperation of many countries  and reductions in many sources.

          The U.S. is currently the largest contributor to the greenhouse gas buildup,
           but its share of global emissions is only about  one-fifth of the  total. The
           rest of the OECD and the East Bloc each contribute a similar amount.
           The relative contribution of the U.S. and OECD  countries to total global
           emissions is likely to decrease over the next century.

          Per capita emissions in developing countries are currently very low, but the
           share  of total emissions contributed by developing countries is expected to


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           increase significantly in the future, and becomes more than 50% by 2025 in



           the scenarios analyzed.







          All nations will need to adopt measures to slow the buildup of greenhouse



           gases, if climate change is to be effectively limited.  If developing countries



           do  not adopt climate stabilizing policies, then  the  equilibrium warming



           commitment in 2050 could increase by about 40% compared to scenarios in



           which there is global cooperation.








          Technologies developed in the OECD nations could enhance the ability of



           developing nations to reduce emissions. Efforts to develop technologies that



           are more efficient and that produce energy from sources other  than fossil



           fuel can make a significant difference in ultimate greenhouse gas emissions



           throughout the world.








          Energy production  and use  is currently  responsible for almost 60% of



           increases  in the greenhouse effect, followed by chlorofluorocarbons (about



           20%),  and  agricultural practices and  deforestation  (roughly 10%  each).



           Even the largest source categories, such as automobiles or utilities, however,



           represent less than  30% each of total greenhouse gas emissions.








          In the immediate term  the most effective options  to reduce commitments



           to greenhouse warming are  to further reduce chlorofluorocarbons,  apply



           already attractive energy-efficiency technologies, and reduce and then reverse



           deforestation.    Longer-term  approaches   for  reducing  the  warming



           commitment  would  emerge  from  immediate investments  to develop









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           technologies that lower the cost  of producing goods and services without



           producing  as high  levels  of  greenhouse  gas  emissions.   Promising



           technologies include advanced materials, thin-film photovoltaics, and biomass-



           fired turbines.







          Neither energy efficiency nor  non-fossil fuels alone would be sufficient to



           greatly limit  greenhouse gas  emissions  in the long term;  both will be



           necessary.
IV.   A  wide  range  of  policy  choices  is  available  to  reduce greenhouse  gas




emissions while promoting economic development, environmental, and social goals.








          Industrialized and developing countries could limit the buildup of greenhouse



           gases in a  manner  consistent with  economic development and  other



           environmental and social goals. In industrialized countries, acid rain, urban



           ozone, and dependence on imported energy could be reduced as part of an



           overall strategy that reduces greenhouse gas emissions.  Energy  efficiency



           improvements are already essential in developing countries to reduce capital



           requirements for  the power sector, and efforts  to halt deforestation  will



           provide  many long-run economic and environmental benefits.








          If limiting the greenhouse gas  buildup 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 risks of climate change.







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          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 necessary to



           impose  emission fees on  these  sources  according  to  their  relative



           contribution to global warming in order to accomplish this goal. This would



           also raise revenues that could finance other programs.  The degree to which



           such fees are accepted will  vary among countries, but acceptability would be



           enhanced if fees were 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 such as those designed 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.








          The best ways to avoid producing greenhouse gases cannot be anticipated;



           accelerated  investment in a range of options is  necessary if policy makers



           want to  assure that  better and  less costly options will be  available in the



           future.
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                 Government policy is already exerting considerable influence on the rate of



                  growth in greenhouse gases.  Policies adopted to reduce CFC production will



                  reduce the rate of greenhouse gas buildup.  Policies that have been adopted



                  or are under consideration to promote greater use of coal, reduce required



                  improvements in automobile  efficiency, and subsidize electricity consumption,



                  may  significantly  accelerate the  rate  of greenhouse gas emissions.   A



                  combination of  factors  that increase  greenhouse  gas  emissions could



                  accelerate  commitments to  global warming by as  much as 60% in  2050



                  relative to  the Rapidly Changing World scenario.








                 U.S.  leadership  has  made important  contributions to recent international



                  environmental agreements, such as the Montreal Protocol on Substances that



                  Deplete the Ozone Layer and the Tropical Forest Action Plan.  The U.S.



                  government is committed to playing a key role in  the Intergovernmental



                  Panel on Climatic Change  (IPCC) established under UNEP  and WMO



                  auspices.   The U.S.  can  also  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.  Finally, domestic initiatives could foster international



                  cooperation by demonstrating a commitment  to respond to global climatic



                  change.
       DRAFT - DO NOT QUOTE OR CITE         91                            February 21, 1989




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