Unlttd St*t» Offt<5» Of th* Admlnl*tr»tor EPA-SAB-EC-*9-034
Envfronmtntml Protection Sel»nc* Advisory Bo*rd S«pt»mb«r 1989
Afl»ncy Washington, DC 20480
E PA Report of the Global
Climate Change
Subcommittee
Review of the Report
to Congress:
Policy Options for
Stabilizing
Global Climate
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STATES ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D C. 204SQ
September 15, 1989
The Honorable William K. Reilly
Administrator
U,S. Environmental Protection Agency
401 M street, S.W.
Washington, DC 20460
RE: Policy Options for
Stabilizing Global Climate
Dear Mr. Reilly:
we are pleased to transmit via this letter-the report of
the Science Advisory Board's Global Climate Change
Subcommittee concerning their review of the Agency's second
report to Congress on Global Climate Change. This draft
report, Policy Options for Stabilizing Global _C.Iiaate. was
reviewed by the Subcommittee on April 4-5, 1989 with comments
offered directly to EPA staff.
The Subcommittee commends EPA for its portrayal of policy
options for stabilizing global climate. Our overall reaction
to the draft stabilizing Report is generally positive. This
report represents, to our knowledge, the most comprehensive
effort to date to deal with the full range of radiatively
active or greenhouse gases (carbon dioxide, methane, nitrous
oxide, chlorofluorocarbons, ozone) over a time period
extending out to the year 2100.
The publication of this report is timely, with the United
states in the position to provide leadership in defining and
implementing policy options that can contribute to stabilising
global climate. The analysis in the Stabilizing Report
indicates that some of the most important aspects of these
options can be foreseen now, even though many important
uncertainties remain*- both in the scientific understanding of
the extent and character of global climate chang*, and in the
problems and promise of the policy opportunities. With
appropriate revisions, we believe that th« report will
contribute significantly toward increased understanding of the
character and magnitude of the task of setting policies to
stabilize global climate.
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We appreciate the opportunity to provide our comments on
this important national and international environmental
problem.
Sincerely,
0. Warner North
Chairman
Global climate Change
Subcommittee
Science Advisory Board
^L^w
/ —--~~
Raymond C. Loehr
Chairman
Executive Committee
Science Advisory Board
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ABSTRACT
This report presents the views of the U.S. Environmental
Protection Agency's Science Advisory Board concerning its review
of the EPA1a draft report to Congress entitled: "Policy options for
Stabilizing Global Climate". The Board commends EPA for its
portrayal of policy options for stabilizing global climate. The
draft stabilizing Report represents, to the Board's knowledge, the
most comprehensive effort to date to deal with the full range of
radiatively active or greenhouse gases (carbon dioxide, methane,
nitrous oxide, chlorofluorocarbons, ozone) over a time period
extending out to the year 2100, This report provides worldwide
projections of the emissions of these gases under plausible future
scenarios and examines the effects of policy options in reducing
emissions levels. Some of the most important aspects of these
options can be foreseen now, even though many important
uncertainties remain, both in the scientific understanding of the
extent and character of global climate change, and in the problems
and promise of the policy opportunities. with appropriate
revisions, the Board believes that the report will contribute
significantly toward increased understanding of the character and
magnitude of the task of developing policy options to stabilize
global climate. Furthermore, the Board believes that assessment of
the potential effects of global climate change, the evaluation of
stabilizing options, and the research on climate change, effects,
technologies that may reduce emission rates, and on the
institutional and implementation issues in deploying these
technologies should all be pursued immediately and vigorously as
part of a coordinated program, within EPA, the Federal Government,
and through international organizations.
Key Words; Greenhouse Gas; Global Climate Change; Policy Options
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NOTICE
This report has been written as part of the activities of the
Science Advisory Board, a public advisory group providing
extramural scientific information and advice to the Administrator
and other officials of the U.S. Environmental Protection Agency.
The Board is structured to provide a balanced expert assessment of
scientific matters related to problems facing the Agency. This
report has not been reviewed for approval by the Agency; and,
hence, the contents of this report do not necessarily represent the
views and policies of the Environmental Protection Agency or other
agencies in the Federal Government. Mention of trade names or
commercial products does not constitute a recommendation for use.
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U.S. Environmental Protection Agency
Science Advisory Board
Global Cliaate Chancre
Chairman
Dr. D, Warner North, Decision Focus inc., Los Altos, California
Members
Dr. Robert Dickinson, National center for Atmospheric Research,
Boulder, Colorado
Dr. Brian Flannery, Exxon Research and Engineering Co., Annandale,
New Jersey
Dr, Mark Harwell, Center for Environmental Research, Cornell
University, Ithaca, New York
Dr. George Hidy, Environment Division, Electric Power Research
Institute, Palo Alto, California
Mr. Marc Ledbetter, 'American Council for An Energy Efficient
Economy, Washington, DC
Dr. William Mooraaw, World Resources Institute, Washington, D.c.
Dr. Harold Mooney, Department of Biological sciences, Stanford
University, Stanford, California
Or, William Nierenberg, scripps Institution of oceanography,
La Jolla, California
Dr* John Reilly, Economic Research Services, United States
Department of Agriculture, Washington, DC
Dr. Milton Russell, University of Tennessee, Knoxville, Tennessee
and Oak Midge National Laboratory, oak Ridge, Tennessee
Dr. Robert Watson, national Aeronautics and Space Administration,
Washington, DC
Dr. Jack White, New«¥ork State Energy Research and Development
Authority, Albany, Sew York
Dr. Robert Williams, center for Energy and Environmental studies,
Princeton University, Princeton, Mew Jersey
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i Advj^LQgv Boftfd Staff
Mr. A. Robert PLaaJc, Designated Federal Official, Science Advisory
Board (A-101F), Office of the Administrator, U.S.
Environmental Protection Agency, 401 M Street, SW»
Washington, DC 20460
Ms, Carolyn Qsborne, Staff Secretary, Science Advisory Board
(A-101F), Office of the Administratort U.S. Environmental
Protection Agency, 401 M Street, SW, Washington, DC 20460
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TABLE OP CONTENTS
1.0 EXECUTIVE SUMMARY ......... I
2.0 INTRODUCTION . . . 4
2.1 Background ........... 4
2.2 Charge to the Subcommittee . 5
2-3 Review Process and Format of this Report . 5
3.0 STRENGTHS AND WEAKNESSES OF THE STABILIZING
REPORT ........... . . 6
3.1 strengths and Significant Findings .... 6
3.2 Weaknesses , ................ s
3.3 The Need for Further Planning and
Analysis ................. 9
4.0 COMMENTS ON THE EXECUTIVE SUMMAR¥ ....... 10
5.0 COMMENTS ON CHAPTERS I THROUGH IV ....... 11
5.1 General Comments ....... 11
5.2 Comments on Chapter 1 .14
5.3 Comments on Chapter II 15
S.4 Comments on Chapter III 15
5.5 Comments on Chapter IV .......... 17
6.0 COMMENTS ON CHAPTER VII ............ 17
7.0 COMMENTS ON CHAPTERS V, VI, VIII, IX ..... 19
8.0 SUMMARY WITH RESPECT TO THE SUBCOMMITTEE•S
CHARGE .,.»,... .... 23
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i.o
The United States Environmental Protection Agency (EPA) has
been asked by Congress to report on the potential environmental and
health effects of global climate change and the choices the global
community may need to consider in order to limit and adapt to
potential global warming. The two reports that EPA is preparing
in response to this request are the Potential Effects of Global
Climate Change qn the United Stages and PQ 1 icv Options for
Stabilizing Global Climate. The EPA has asked its Science Advisory
Board (SAB) to establish a review panel to evaluate these reports.
The SAB established the Global Climate Change Subcommittee
with the charge to review these two reports in draft form and
evaluate their technical adequacy, uncertainties, and consistency
of recommendations with the findings contained in the reports. The
EPA plans to incorporate SAB comments in their revision of the two
reports before they are finalized and transmitted to Congress, The
SAB report on the first document, Potential Effects of Global
Climate change on jfchja United States was released in April 1989 (See
U.S. EPA Report, £PA-SAB-EC-a9-0l6, April 198t) . The present SAB
report presents the conclusions and recommendations of the
Subcommittee on its review of the second report , Policy Options for
stab i 1, i z i ng G 1 oba 1 __c 1 ima t e (known hereinafter as the stabilizing
Report) .
The Subcommittee commends EPA for its portrayal of policy
options for stabilizing global climate. Our overall reaction to
the draft stabilizing report and th« presentations made to the
Subcommittee on April 4-5, list are generally positive. This
report represents, to our Knowledge,, the most comprehensive effort
to date to deal with the full range of radiatively active or
greenhouse gases (carbon dioxide, methane, nitrous oxide,
chlorof luorocarbona , ozone) over a time period eactending out to the
year 2100. The report provides worldwide projections of the
emissions of these gases under plausible future scenarios and
examines the effects of policy options in reducing emissions
levels. Major weaknesses of the draft report lie in Chapters VIII
and IX, which focus rather narrowly on near-term options to reduce
energy demand, with relatively minimal discussions of research and
development and opportunities for United states leadership through
international cooperation,* and the failure of the "report to provide
sufficient information on the costs or possible trade-offs involved
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in choosing between, and implementing various stabilizing options.
with appropriate'' revisions, we believe that'"th* report will
contribute significantly toward increased understanding of the
character and magnitude of the task of setting policies to
stabilize global climate.
The draft stabilizing Report summarizes calculations
indicating that a reduction of at least 50% from today's rat* of
worldwide emissions of carbon dioxide and substantial reductions
in emission rates for other greenhouse gases are needed to
stabilize the concentrations of these gases at their current levels
in the atmosphere (Executive Summary, Figure 4, p. 141 Table 1, p.
15). The draft Stabilizing Report states that such large
reductions in emissions are judged to be infeasible (Executive
Summary, p, S6):
Stabilizing the commitment to global warming would
require cuts in emissions so significant that currently
available and emerging technologies are insufficient to
achieve this goal.
The report, therefore, examines policies that could stabilize
the rate of emissions. rather than atmospheric concentrations of
the radiatively important gases at levels roughly comparable to
those prevailing today, under scenarios that reflect plausible
estimates of world population growth and economic development
through the next century. The policies are intended to stabilize
global climate at an altered level of radiative balance,
corresponding to an increase in realized global average temperature
of one or two degrees Celsius by the year 2100 and a long-term
equilibrium commitment to a global average warning somewhat higher",
in the range of 1.4 to 3.3°C (Appendix B, fable B-152, B-153) * The
report notes that an equilibrium warming commitment of 0.1 to 1.5*c
relative to the preindustrial era is expected due to emissions up
to the present time, and that continued emissions during the next
several decades at projected levels could lead to an equilibrium
warming commitment in the range of 1 to 3°C.
The analysis presented in the report uses realized global
average temperature over time and long-term equilibrium commitment
to'global average warming as indicators to describe the magnitude
of global climate change. (The long-term equilibrium warming
commitment is the amount of warming projected to occur for a given
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4
composition of'the atmosphere if this composition wer* to remained
constant over time and the atmosphere, oceans, and land masses
reached thermal equilibrium.) As is discussed in the Effects
Report and its review by the SAB, regional variations in
temperature, precipitation, and extreme climatic events may b* more
appropriate measures of climate change impacts, but forecasts of
such impacts are at present extremely imprecise,
Alteration of the level of carbon dioxide and other
radiattvely active gases in the Earth's atmosphere has the
potential to change the climate,* the scientific information now
available does not permit precis* prediction of the character and
magnitude of the climate changes. Large uncertainties in measures
of climate change are likely to persist, even with foreseeable
improvements in the General circulation Models used to investigate
the climate consequences of alteration in atmospheric composition.
The evaluation of stabilizing options must be done in the face of
large uncertainties about the character and magnitude of climate
change? these uncertainties add to the difficulty of the evaluation
process for stabilizing options but they should not preclude such
evaluation from being undertaken. The scientific information now
available on the potential for global climate changes suggests that
the evaluation of stabilizing options should be vigorously pursued
now, rather than delayed while further scientific research attempts
to reduce the uncertainties.
The analysis in the Stabilizing Report compares scenarios with
continued large increases in emissions of radiatively active gases
as the result of worldwide population growth and economic
development during the coming century with scenarios in which
stabilizing policies reduce or reverse these increases in
emissions. The comparison is therefor* between scenarios with an
accelerating increase in atmospheric concentration levels from
increasing emissions of radiatively active gases, and scenarios in
which the extent of the increase in atmospheric concentration
levels is reduced by holding worldwide emissions to approximately
the levels occurring at the present time* While the change in
atmospheric composition from current emission rates may result in
significant alterations in climate, the scenarios involving
continued Increases fa emission rates during th« next century could
lead to much greater alteration in th* radiative balance and in
climate.
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The proposed., policies needed,.,- to achieve,, r the objective of
stabilizing emission rates"' at approximately' eunrent levels
represent perhaps the most ambitious and comprehensive sustained
effort to manage human activity that has ever been attempted in
peacetime. These proposed policies would involve massive changes
in energy, land use, and other economic sectors on a worldwide
scale. Policies intended to stabilize atmospheric concentrations
of radiatively active gases at lower levels will involve even
greater alterations in worldwide human activity.
The United States is in a position to provide leadership in
defining and implementing policy options that can contribute to
stabilizing global climate. The analysis in the Stabilizing Report
indicates that some of the most important aspects of these options
can be foreseen now, even though many important uncertainties
remain, both in the scientific understanding of the extent and
character of global climate change, and in the problems and promise
of the policy opportunities. Congress and the American people
should consider what actions should be taken now to provide such
leadership on this global problem. The stabilizing Report provides
a good point of departure for discussion of the role that the
United States should play in achieving the stabilization of global
climate. However, the report is lacking in analyses of economic and
social costs or tradeoffs associated with the policy choices, so
that it must be regarded as only an initial step in formulating
policy options.
2»Q IHTRODPCTIOH
2.1
In early 1988, the EPA's Office of Policy, Planning and
Evaluation (OPPE) requested that the Science Advisory Board (SAB)
establish a review panel to examine the two EPA reports to congress
on global climate change. These are The Potential Effects of
Global Climate Change on the United States (Effects Report) and
Policy Options for Stabi^|zin
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Stabilizing Report was released to the Subcommittee in March 1989,
with subsequent .public review April 4-5, 1989 in Washington, DC.
2.2 g*i«ra« to
The subcommittee has been tasked with the responsibility to
review the two draft EPA reports to Congress and to provide advice
to the Agency on the following:
Assessment of the technical adequacy of the two reports,
especially the degree to which they address the
environmental and other effects of climate change.
Identification of areas of uncertainty in the reports,
and the degree to which this uncertainty nay affect the
recommendat ions .
Consistency of the recommendations with the findings
contained in the reports. Specifically (for the
stabilizing Report) , are policy options identified that,
if implemented, would stabilize current levels of
atmospheric greenhouse gas concentrations.
other related issues that the Subcommittee believes
should be addressed.
2-3 aevie* Proeeaa and Format ef thia
The Subcommittee's tas)c was to review the draft Stabilizing
Report and to provide advice to EPA on means to improve it, not to
provide ongoing oversight of the document as it may evolve from the
point of the review. At the April 4-5, 1989 meeting, the Agency
staff were provided with detailed comments on each chapter of the
report. Following th« meeting, they were provided with detailed
written comments and a transcript of the meeting.
This report contains information compiled from the meeting
transcript and from written comments submitted by each Subcommittee
member. Editorial items are generally omitted since they have
already been provided to EPA. The Subcommittee * s primary goal is
to summarize the maiS* points of our advie* to EPA, not to reiterate
all the advice given to EPA at the public me*eting and in our
written comments.
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This report^ . contains eight major divisions; an Executive
summary (1.0) which highlights' 'the major is*u«» we vish ' to
emphasize* an Introduction (2.0) which provides a discussion of the
background and purpose of this reviewi an Overview (3.0) which
presents a broad discussion of the conclusions of the Subcommittee;
and four sections which review individual chapters or groups of
chapters of the Stabilizing Report. The first of these sections
(4.0) contains our review of the Executive Summary; the second
section (5.0) contains our review of Chapters I through IV? the
third section (6.0) contains our review of Chapter VTI; the fourth
section (7.0) contains our review of Chapters V, VI, VIII, and IX;
and the final section (8.0) contains our summary with respect to
the charge of the Subcommittee.
3.0 jgaENSTlfl_JJ^JglJpgJg|^8 Oi; .^jJB-jBTMIIilglKq REPORT
The stabilizing Report in its current draft form has many
strengths and some significant deficiencies in need of remedy*.
These are summarized below.
3«* Strengths and
The report is written in a style that is technically sound yet
readily comprehensible for most readers. The first four chapters
provide a good overview of scientific knowledge regarding the
build-up of radiatively active gases in the atmosphere and the
potential for climate alteration on a regional and global scale.
chapter vn provides a lengthy compendium of technical options for
reducing emissions of these gases. While the specific
characteristics of these options are subject to debate , the chapter
provides an excellent introduction for readers unfamiliar with
these options. Extensive critical review of the specific options
by both proponents and skeptics will improve the basis for
evaluation of the options. In our judgment, EPA is to be commended
for the extent to which they have organized this material to
facilitate such critical examination. However, Chapter VII
primarily serves as background concerning technology. The material
in the chapter is not directly used in the scenarios.
The analysis presented in chapters V and VI forms the core of
the report. EPA has done a good job of formulating the analysis
in terms of a small number of future scenarios, which are not
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claimed to be'accurate predictions, but rather consistent cases
describing future changes in population and economic development,
A slowly changing world (SOW) and a rapidly changing world (RCff)
are examined with and without a set of stabilising option* or
policy. Each of the four resulting scenarios are evaluated using
a set of modules for energy, industry, agriculture, and land
use/natural sources to project emissions over tine. An ocean
module and an atmospheric composition/temperature module are used
to project how the emissions will translate into potential climate
change, using the simplified measures of realized global average
warming and equilibrium commitment to global average warming. The
logical framework for this analysis is readily comprehensible, and
the methodology and major assumptions are clearly stated. The
sensitivity analysis of Chapter VI provides important insights
regarding the extent to which the results depend on specific models
and assumptions,
The analysis results indicate that the single most important
determinant of emissions is the level of energy demand and the
combination of sources used to supply that energy. Carbon dioxide
accounts for more than 65% of increased commitments to global
warming in all the scenarios (Figure 5-20, p. V-8Q), and energy
dominates deforestation in the magnitude of COZ emissions. In the
two non-policy scenarios the use of coal as a source of primary
energy expands greatly, partially as the result of extensive
development of coal-based synthetic fuelsi in the two stabilizing
policy scenarios world coal use expands very little, and other
energy sources meet the increased energy demands projected for the
next century (Figure 5-9, p. V-40), Population (Figure 5-3, p»
v-19) and economic development are important determinants of the
end-use fuel demand (Figure 5-6, p» V-34), and in all scenarios the
regional allocation of CO2 emissions shows a rapid increase in the
share attributed to developing countries. The degree of
participation by developing countries in stabilizing policies is
one of th« most important factors in determining the extent of
global climate change by the year 2100 (p. VI-3). Technologies and
capital from the United states and other OECD countries could
enhance the ability of the developing nations to reduce emissions.
Efforts to develop technologies that are more efficient and that
produce energy from sources other than fossil fuel will be critical
to achieving emissions reductions from nations throughout the world
(p. 88). Sensitivity analysis (Figure 5-21, p. V-83? Table 6-1, p.
VI-7) indicates that reduction in many sources and cooperation by
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many countries will b« needed to have a major impact in
emissions (Finding m, p. 57), sensitivity analysis further
indicates that the results of the analysis are less sensitive to
some of the inany assumptions used in the ocean CQ2 module and the
atmospheric composition/temperature module (Table 6-1, p. VI-7).
However, the timing and the magnitude of temperature change depend
directly on the assumed temperature sensitivity to doubled coz and
the rate 'of heat uptake by oceans. The analytical results depend
on the models and data used, and these data and models clearly
warrant further investigation.
3,2 Weaknesses
The Stabilizing Report should begin with a discussion of the
analytical approaches and the choice of stabilizing options to be
examined. An Executive Summary of 91 pages is too long to hold the
interest of many readers, and we recommend a shortened version
emphasizing the analysis of stabilizing options rather than the
science issues discussed in chapters I-IV. Detailed documentation
of the data base, the analytical modules used in Chapters v and VI,
and analytical results (e.g», energy prices) is urgently needed*
The Subcommittee understands' that EPA is producing such
documentation. The flow of the policy chapters (V, VI, VIII, and
IX) is broken by the lengthy discussion of technical options in
Chapter VII; this chapter might be moved up to follow chapter IV
or made an appendix. A concluding chapter summarizing the evidence
in support of the findings (pages S3-91 of the Executive Summary)
would be a useful addition to the Report,
A major weaJcness of the draft report lies in Chapters VIII and
IX. These chapters focus rather narrowly on near-term options to
reduce energy demand, with relatively minimal discussions of RiD
and opportunities for United State* leadership through
international cooperation. The Subcommittee believes that these
chapters should be expanded to include more detailed discussion of
opportunities for development, technology transfer, and
commercialization of technologies to enhance energy efficiency and
replace dependence on fossil fuels, especially in developing
countries. These chapters should be more closely integrated with
Chapters V and VI .^ They should giv« the reader a sense of
priorities, not .just a list of possibilities,, and they should
indicate further steps needed for more detailed analysis of both
domestic and international options.
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A second major weakness in the report la thart it provide*
little information on the costs or possible trade-offs involved in
choosing between and implementing various stabilizing options. The
discussion of Chapter VII and the analysis of Chapters V and VI
indicates that the stabilizing policies will have substantial
impacts on energy prices, land use, agriculture, and industrial
development, h summary of costs would be an extremely useful
addition to this draft report and the appropriate focus of a major
effort in further EPA study of stabilizing options.
3-3 Tlte Meed for Further Planning and Analysis
The Stabilizing Report is an appropriate response from EPA to
the request made of it by Congress. The analysis and findings may
disappoint those who had hoped that stabilizing the atmosphere to
avoid climate change could be accomplished with modest efforts by
the us in cooperation with other industrialized nations. The
findings indicate that stabilizing the atmosphere nay be possible
only in the next century, at concentration levels of radiatively
active gases that may alter climate in significant ways, and then
only as the result of a great effort by many nations involving high
levels of innovation . It seems clear that investigation on the
effects of global climate change, stabilizing options, and research
planning relating to both effects and technological innovation
should be undertaken in a coordinated fashion, and that the United
states Government should commit significant resources to such
integrated planning as a follow-on effort to the two Reports to
Congress prepared by EPA. t
Concern over the prospect of global climate change is now
widespread in the united states and in many other nations, and
numerous international study efforts are being launched. The two
EPA Reports to Congress should make important contributions; they
represent perhaps the most extensive investigations on effects and
stabilizing options yet undertaken toy any nation or international
group. But the level of analysis and investigation that they
represent ia regarded as an initial effort. The insights from
these reports should be used to guide much more extensive
investigations on global climate change effects in the United
States and in other eeuntries, on stabilising policies that can be
implemented with existing technologies, and on the potential for
research and development to develop new technologies for further
reductions in emissions at affordable costs.
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What l*vet:,;p£; climate stabilization i» needed, and what level
can the , nations of the world afford, consistent with their
aspirations for economic and sociai development? Both the process
of selecting policies and the process of implementing policies will
be difficult; selection and implementation decisions will evolve
over decades based on the actions of many nations. The United
States has the technical and analytical skills and resources to
play a leading role in investigating the threat posed by global
climate change and in developing options for responding to this
threat. United States leadership in scientific research,
planning, and technological innovation can provide a basis for
better decision making by the United States and by many other
nations. The SAB Global Climate Subcommittee commends both EPA and
its Congressional sponsors for the progress achieved so far in the
two reports to Congress. We urge that expanded planning and
analysis efforts on global climate change be vigorously pursued by
the Federal Government both directly and through participation in
international studies.
4.0 aaCMEOTjEL.OBLJCHg- UEgCSTTgl.. SUMMARY
At 91 pages, the draft Executive Summary is not a summary but
a short report, and it is sufficiently long and complex to deter
many readers. The findings at the end of this section should be
placed at the beginning. This "summary of the summary11 especially
should be carefully reexamined to assure that it reflects the most
important conclusions from the report and that its tone is
appropriate. Specific examples of wording problems, inappropriate
tone, and poorly supported conclusions were discussed by
Subcommittee members at the meeting, April 4-5.
The Executive summary should include a more explicit
discussion of why EPA chose to focus on options that stabilize
emission rates rather than the much more stringent options needed
to stabilize atmospheric concentrations. The basis for the numbers
in Table 1 aa model-based estimates should be made evident, and the
implications for the feasibility of stabilization at various levels
need exposition.
The Executive Summary might focus more on the methods and
conclusions regarding stabilizing options and less on the
scientific knowledge of how radiatively active gasea affect
climate. The latter material ha* been the subject of many other
10
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studies, and the first four chapters provide » good review for th«
unfamiliar reader. The sensitivity analysis (Table 6, its
footnotes, and associated text) seems overly lencfthy for the
Executive Summary. The implication of the sensitivity analysis is
that uncertainty in the level of future coal use has a large impact
on projected climate change. The projected extent of climate
change as represented by equilibrium warming commitment is less
sensitive to many of the modeling assumptions for ocean C02 and
heat uptake, atmospheric chemistry, and, feedbacks. Th«se important
results could be presented more clearly and with less detail.
5,0 COMMENTS ON CHAPTERS I THROUGH IV
5»l General Comments
Overall, these four chapters do a good job of assembling and
describing a broad range of relevant scientific information dealing
with current knowledge of nature's response to increasing levels
of greenhouse gases. The inclusion of all major gases in a common
framework is a significant and important extension of previous
work, in the text, both the status and uncertainty of the science
are well described. However, many of the cautions and caveats are
lost in the statements of Findings and Conclusions that accompany
each chapter. The Subcommittee had a number of editorial comments
concerning slight inconsistencies of information from place to
place, and dealing with clarity of presentation, but basically we
felt that the science was veil described. We find the liberal use
of graphs and figures add to the clarity of presentation. However,
the captions for many of the figures could be enhanced to provide
better explanations of what the figure illustrate. In some cases
it may be appropriate to box the figure with mora lengthy
explanatory text. This approach would be particularly useful for
figures drawn from the Chapter I through IV material that appear
in the Executive Summary,
The Subcommittee had two substantive concerns about the
description of the science. First, the principal methodology
relies on model output that focuses exclusively on global
temperature change as a surrogate for climate change. While the
report acknowledges fchat temperature change per so is not the sole
measure of impact, nor arguably the most meaningful, this point
needs to be amplified considerably. Second, while the report
properly focuses on scenarios through 2100, it would be useful and
11
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important to include a discussion of what ia known concerning
longer range climate change, in fact, we held a useful discussion
of this topic during our review meeting. Policy discussion should
recognize the potential that buildup of greenhouse gases may have
very long-tern consequences for climate, because the residence
times for greenhouse gases in the atmosphere are long.
The report discusses a methodology based on simplified,
integrated models to generate scenarios of climate change through
the year 2100, These models incorporate not only nature's response
but also the social and economic activities driving future
emissions of greenhouse gases. Principal input to the models is
the specification of scenarios, including assumptions and judgments
about population growth, economic growth, and demand for and
availability of various technologies for energy supply. Principal
output from the models is the variation of globally averaged
temperature with time, which is taken as a surrogate for climate
change. Change is driven by emission of greenhouse gases from
future human activities that are derived from a series of economic
models (described in later chapters). The accumulation and
interaction of atmospheric greenhouse gases serve as input to the
models of physical climate change. To describe the physics and
chemistry, the report implements a simplified model of atmospheric
chemistry, a parameterized representation of radiative forcing from
greenhouse gases, and a one-dimensional transient model of
temperature change that accounts for the flow of heat (and CO2)
between the 'atmosphere and oceans*
At this time the use of linked, simplified models is probably
the best available methodology to examine scenarios of climate
change that support analysis of policy options. These are not the
full-fledged models of atmospheric chemistry or oceanic and
atmospheric circulation most often cited as fivinf forecasts of
future climate impacts. Simplified models like these have been
used often in th« past to assess the basic picture of climate
change witfc time in a manner that captures aany important features
of far more complex models. while complex models include
substantially more detail and resolution in their description of
atmospheric chemistry, radiative transfer, and climate, their use
for integrative anajyreis is prohibitively costly and cumbersome,
especially if l^rge numbers of sensitivity cases are to be
investigated. Yet simple models are deceptive in "results and their
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validity? a comparison with more sophisticated and detailed models
is warranted for. calibration.
This report for the .first time puts a complete act of models
together in a unified package that integrates treatment of all the
major trace gases responsible for greenhouse forcing. The report
builds from previous efforts, utilizing sensible approaches and
best available results from more complex models. The report also
does an excellent job of describing major areas of uncertainty, and
in showing the dependence of results on uncertainty in the science
that can be captured in their modelinf framework.
The report recognizes that temperature change alone is not the
sole measure of impacts from climate change, but this point should
be amplified extensively. Far more than global average
temperature, changes in sea level, the hydrological cycle, and
climate variability (e.g., the frequency of drought or intense
storms) are the more relevant variables to assess impacts in
particular regions. However, these variables are far more
uncertain in model predictions. Assessment of policy options to
respond to potential effects on agriculture, ecosystems, or human
impacts require far more information than is available from global
temperature change alone. Also, impacts will be differently
distributed across the globe at locations and times that are
difficult to predict. The Subcommittee is concerned that by
placing so much emphasis on global temperature, the non-expert
reader might be led to guestionable conclusions about the
effectiveness of policies. For example, one might conclude that
reducing the temperature increase by half could reduce impacts by
half, and that would be a naive and misleading conclusion.
We found the choice of four scenarios to be useful and
illuminating. However, the narrative description of results, the
lack of certain analyses, and the lack of a base case make it
difficult to unravel sensitivities that allow one to understand the
meaning of the results. For instance, there is limited analysis
of the range over which policies might b» varied, the impediments
to implementation, or the possible trade-off between various
approaches. Also it appears that even the assumptions in the
non-policy scenarios^ already may include overly optimistic
projections concerning the pace of implementatipn of efficiency
steps in end-use applications of energy, and concerning the
availability of alternate (non-fossil fuel) sources of energy. The
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net effect may well be to underestimate the magnitude of societal
response that night be required to limit future climate change.
5.2 comwMi.1b.aL oa
This chapter does a good job of summarizing the genesis and
goals of this study. The Subcommittee notes that the report does
not actually respond to the Congressional charge to examine
policies that stabilize levels of greenhouse gases at current
concentrations in the atmosphere, and this should be acknowledged
more clearly in the introduction. It might well be stated that the
goal nay be presumptuous, since we do not completely understand
Nature's cycles well enough to know if humans can indeed control
the atmospheric composition. Also, water vapor, the dominant
greenhouse gas, is not directly controlled by human activities.
However, current knowledge allows us to make some estimate of the
magnitude of emission control, and time, for atmospheric
composition to equilibrate. Admittedly the long-term estimates
involve large uncertainly that must be described. It may well be
true that to accomplish this objective is not possible without
unacceptable and unworkable international actions and sacrifices.
Nevertheless, working backward from that goal would provide an
important bound on what policy changes would accomplish.
While reasonably complete in the review of prior studies, the
Introduction should acknowledge the proceedings of the Villach
Workshop, "Developing policies for responding to climate change",
Also, the report does not cite or describe proposals produced in
the Canadian climate Conference, the Hamburg Conference, or indeed
in several recent Sills submitted to Congress, which already make
specific calls for target reductions ^ in 'emissions, and other steps,
The stabilizing Report could contribute to a better understanding
of those proposals.
The Introduction should also clarify what the report does not
dot provide cost estimates, or analyses of the policy proposals
that would allow one to judge th* trade-off between on* or another,
including costs and societal impacts. Nor does the report address
the issues associated with implementation of policies in the United
states and globally I*- At th« outset it should b* acknowledged, in
the context of setting policy, that science cannot yet provide
meaningful criteria to differentiate among impacts associated with
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different rat* a and magnitudes of climate change, That should b*
stated a» an important goal to aid futur« policy analyses.
5.3
This is an excellent compilation and summary of the science
concerning the data and understanding of the buildup of the most
important greenhouse gases, our comments concerning this chapter
were mostly editorial concerning details of presentation and
consistency of description.
we recommend that the discussion of sources and sinks should
acknowledge the lacK of quantitative understanding of the current
buildup of carbon dioxide in the atmosphere. There is an imbalance
between known sources and sinks that night be masking a large
unknown sink for C02. That is to say: compared vith emission
rates, the buildup of atmospheric C02 is smaller than we can
readily explain. This topic is discussed in later chapters, but
should be brought out here as a major scientific uncertainty in the
greenhouse issue. When processes that control atmospheric C02 are
not clearly understood, it is difficult to predict the
effectiveness of policies to limit C0| emissions. It is possible
in the future that analyses of changing isotopie ratios in
atmospheric CQ2 may distinguish between competing sources of
carbon: anthropogenic additions from older fossil fuel carbon
versus changes in younger sources associated with the biosphere.
This chapter suggests that natural sources and sinks remain
in balance, implying that anthropogenic emissions account for the
entire buildup of C02, but that is an assumption, not a statement
of certain scientific knowledge. Moreover, climate change might
induce changes in the natural cycles that would lead to further
imbalance, increasing or decreasing future rates of buildup.
5,4 Conrnent* on Chapter n
Chapter III addresses the data and model results for the
analysis of climate change. This is a crucial section, since it
describes th* extent to which w* can accurat*ly predict climate
change, given changes in atmospheric composition, with our present
capabilities, and it Enumerates the many difficulties that must be
overcome in order for our predictive capabilities to improve. The
chapter includes a discussion of the older paleoclimate data, as
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wen as attempts ..£o reconstruct th* relatively recent past from
archived measurements. . Basic scientific understanding and mo»t
aspects of uncertainty are discussed well within the bulfc of the
chapter. However, the summary statements in the finding* and
conclusions do not reflect fully the state of uncertainty.
Perhaps the most important information in this context is the
record of historical temperature change, which is reasonably
described in the text. While the text states that the gradual
warming seen over the past century is not inconsistent with the
increase in greenhouse gases over the period, it properly calls
attention to the cooling trend for the United States in the data
between 1940-1375 as evidence that other factors must be operating,
Some effort has been made to attempt to sort out effects of known
or assumed influences on climate variation, for instance work by
Hansen and by Gilliland in the early 1980*s. However, their
studies served to indicate how difficult it would be to remove
these effects with certainty. The findings in the summary
statements (perhaps incorrectly) portray the record of warming over
the past 100 years as qualitatively consistent with expectations
from greenhouse models. Mention should be made of published
analyses, most recently by lamanathan, that another decade or two
of observation will be required to confirm models, if warming
occurs as the models now predict. As yet, it is premature to argue
that increases in greenhouse gases explain the record of
temperature change, considering the extent of natural variability.
While there are many speculative proposals concerning feedback
processes that could amplify or reduce future climate change, the
chapter focuses .its remarks on mechanisms that could amplify
greenhouse warming, while ignoring those that might reduce warming.
For example, the findings and text describe possible
bio-geochemical feedbacks that might enhance emission of greenhouse
gases, while ignoring the possibility that higher levels of
atmospheric CO2 might stimulate biospheric growth rates, thus
reducing the future buildup of co2 in the atmosphere. Similarly,
the chapter does not describe the work by Somerville on possible
changes in the microphysical properties of clouds, which would
enhance reflection of sunlight and reduce future warming. Finally,
it is somewhat misleading to refer to several feedback processes
as having been ignorftt in past scientific studies; a more accurate
characterization would be that many processes have been suggested
that may influence climate feedback, but they are still too little
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understood to-.be incorporated quantitatively into models. In this
regard it is not yet possible to distinguish whether physical or
biogeochenical mechanisms will be most important in determining
ultimate effects, as current scientific understanding is not yet
that precise.
The discussion of realized versus equilibrium temperature
change is important and relevant. However, an additional point
should be made clearly: it will be very difficult to establish
ultimate equilibrium climate sensitivity from direct observation.
Models to date, and for the foreseeable future, are likely to
remain sufficiently uncertain that they will need to be calibrated
against observational data. However, measurement can only assess
realized temperature change. In the models, a variety of values
for sensitivity (equilibrium temperature change) , in combination
with an ocean model producing the appropriate delay, can result in
identical amounts of realized warming at a particular date. This
means it will be quite difficult to establish ultimate climate
impacts from given levels of atmospheric greenhouses gases.
5.5 Com»ep|ji g_
This chapter summarizes a great deal of information concerning
anthropogenic emission rates of greenhouse gases. We suggest that
emissions should be characterized as contributing to greenhouse
radiative forcing, rather than contributing to warming. The
relation of the concentrations of radiative active gases to wanning
is complex and, as yet, poorly understood. Th« use of global
average warming as predicted with a simplified model is an
appropriate indicator, or summary measure, for this initial effort
at investigating stabilizing options. It should be clearly
explained that we have relatively poor ability to predict global
average warming, and that more complex characterizations of climate
change will be needed to assess the seriousness of the potential
impacts.
«.0 COMMBKT8 OH CHAPTER
There was some discussion concerning whether or not this large
chapter should be left in the middle of the draft Stabilizing
Report or moved to the back as an appendix. Some members of the
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Subcommittee felt .....that it created'too much separation between the
related issues f in the chapters on either side, while others
suggested that this chapter was too important to t»e relegated to
an appendix. The chapter is well written and provides much useful
information. Nevertheless, we noted unevenness in both the levels
of detail and documentation.
Our major comments in the Energy Services Section concern fuel
economy and the way the chapter relates to the scenarios analysis.
We are concerned about the levels of automotive fuel economy
assumed in the analysis. For the year 2000, fifty mpg may toe an
overestimate of what can be achieved for new cars without affecting
comfort or lifestyle , although it-is certainly achievable on a
small scale or demonstration basis. A more reasonable figure for
what could he achieved with a large implementation program might
be 40 mpf. (However by 2025 or later, automotive fuel economy
could be 50 mpg or.even higher.) In addition, the report should
mention the difference between nominal and real fuel economy. This
difference for new cars is at least as important as degradation in
fuel economy over the.life of an automobile.
The Subcommittee questioned how information presented in this
chapter was incorporated into the scenario analysis. The chapter
presents information on many different technologies, especially
non-fossil fuel energy technologies such as solar, biomass,
nuclear, and technologies for improving the efficiency with which
energy materials are transported, ' converted from one font to
another, and applied to meet end-use needs* For many of these
technologies, the potential impediments to more extensive use merit
further discussion. For example, the safety issue, the waste
disposal issue, and the risks of diversion of nuclear fuel
materials to weapons or terrorism are widely regarded as posing
formidable problems for extensive worldwide use of nuclear power*
Similarly, water and land availability and soil conditions may
limit the extent that biomass technologies can toe used in some
areas of the world.
There should be more information presented in Chapter vn on
the basis for the choice of energy efficiencies and other
parameters used in the analysis of Chapter V. Such discussion is
important for the sensitivity cases, as well as the four main
scenarios. " The reader should have an appreciation for why these
cases are sensible choices for investigation, given the summary
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provided in Chapter VII on the potentials and problems for the
various technologies.
Further discussion is also needed on other topics in the
section on energy supply. Examples include: natural gaa reserves
in other parts of the world such as in the Soviet Union; production
of liquid fuels such as ethanol and methanol, and electric power
generation from biomass; and assessment of plausible implementation
scenarios for the wide range of emerging solar technologies.
In the Forestry Section, also, there is insufficient attention
given to the impediments to implementing the policy alternatives
discussed, especially at the international level. In particular,
cultural, economic, social, and other factors make it difficult
merely to plant trees on a massive scale in many countries. What
is needed is an agrofore-stry-societal system that seeks not just
to maximize carbon dioxide alleviation, but more importantly, seeks
to establish economically robust and long-standing practices that
can replace slash and burn agriculture with forestry, that can
identify polycultures consisting of various trees that would be of
direct economic benefit to the local populace and therefore would
stand a chance of being accepted by them, rather than trying to
introduce economically risky monocultures of trees whose only
purpose is to sequester carbon,
Similar comments apply to the Agriculture Section,
Specifically, there is insufficient discussion of potential
feedbacks (e.g., how climate change might change rates of
methanogenesis); how issues of scale of implementation are
important; and what are the impediments to implementing changes in
farming practices. This section also needs more discussion of
limitations in the data base; for instance, very little is known
about methane production in rice paddies in actual practice in
Asia, yet that is likely a dominant agricultural source of
methane.
7.0 COMH^NTfl ON CHAPTERS V, VI,VIII* 11
Given the greatTfereadth and complexity of the- material covered
in these four chapters, it would be useful to add a short chapter
at the end of the report to summarize the important insights from
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the examination' of stabilizing'-'option* to support the finding*
stated in the Executive Summary.
The modeling system for scenario evaluation that is described
in Chapter V represents a commendable innovation in its
comprehensiveness and its balance'of appropriate level of detail.
The major weakness is the lack of detailed documentation for the
set of analysis modules, the extensive data base required, and the
details of the results for the scenarios examined.
The energy modeling in particular appears to be a major step
forward in marrying top-down and bottom-up approaches. The
approach permits a projection of energy end-use demands by region
based on population and economic development assumptions, and then
a calculation of how alternative energy supplies would be allocated
to meet these demands. The top-down aspects involve substantial
aggregation within regions, among fuel forms, and among
technologies* The choice of demand levels, income elasticities,
price elasticities, resource supplies, and technology costs will
have a major influence on the resulting projections of energy use
and emissions. These choices can be a subject for considerable
debate among energy experts, and the diversity of opinion expressed
by members of the Subcommittee is a microcosm for what can be
expected from the larger community.
In future exercises of this type, it is desirable to expand
the most important aspects of the model (use of coal versus
substitutes including conservation) and examine factors determining
technology choice rather ,than aggregate elasticities. The
advantage of the existing system' is that it provides a systematic
and comprehensive accounting of energy supply and demand as these
evolve over time, by region, and under different assumptions for
policy. It therefore facilitates careful examination of how
conclusions regarding the impact of policies in reducing emissions
depend on specific model assumptions and data. Such examination
should lead to important insights regarding stabilizing options
relating to energy use. The analysis presented in the EPA Report
is appropriately viewed as a good beginning in this process. To
progress further, analysts outside 'of EPA will need access to
detailed technical documentation of the modules, the data bases,
the' scenario results (energy' quantities and prices: over time), and
perhaps the computer codes used in EPA's analysis.
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A major theme needing increased emphasis in th«*« four
chapters i* the importance of energy R40, particularly on
technologies that reduce the level of coal use. For many
countries, coal will be the most accessible and least costly
alternative for energy in the 21st century. Its use, however,
results in even higher CQ2 emissions than from natural gas or
petroleura, which have been the most important energy sources for
the 20th century. A mix of technologies to avoid expanded coal use
is a critical component of policy for stabilizing emissions. These
technologies include alternative means for electric power
generation such as solar photovoltaics and nuclear power, higher
efficiencies and conservation initiatives, and use of taiomass
fuels. Commercialization of these technologies in both
industrialized and developing countries will involve substantial
effort, for there are Many formidable problems to be overcome.
Among these are the acceptability of expanded use of nuclear power,
the land use and water availability problems associated with
biomass, and the increased costs of alternatives compared to the
use of coal for power generation and synthetic fuels. Another area
deserving careful investigation is the development of less
energy-intensive methods for basic materials processing such as
steel, cement, glass, and fertilizers.
The analysis of chapter V and VI indicates the need for
careful reassessment of energy R&D with respect to minimizing
emissions of carbon dioxide and other radiatively important gases.
The Subcommittee believes that exploration of opportunities for
energy technology development and commercialization is an important
topic for this report and for future studies on stabilization. An
important aspect to be addressed is how the energy needs of
developing countries will be met. The successful commercialization
of the technologies needed to reduce emissions will require capital
and technical knowledge that are readily available in the United
States and other industrialized countries but scarce in developing
countries. Successful commercialization will also require that the
technologi»» fit with culture, institutions, and infrastructure
needs of these countries. The report should devote more discussion
to these issues, and examples of innovation in energy policy in the
United states and in other countries would be useful for
illustration. A ntffiber of such examples were discussed at the
subcommittee meeting April 4-5, 1989, A policy option that
deserves further investigation is establishment of technology
transfer centers in Third World countries. These centers would
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provide technical assistance to •encourage adoption of energy-
efficient and renewable energy technologies.
While in general chapters V and VI are carefully written, in
some places the tone needs to be more dispassionate and scientific.
The discussion should not five the appearance of advocacy of policy
alternatives, but .rather describe the alternatives, their potential
to reduce emissions, and the potential impediments to their
implementation, without including value judgments on the
desirability of the alternatives.
The sensitivity analysis is useful, as it can provide
important insights into the robustness of the conclusions drawn
from the analysis of the scenarios. The choice of the sensitivity
cases, their presentation in tables and figures, and the
accompanying text should be revised to highlight the major findings
and insights 'rather than a presentation of a large number of
detailed results. It may be appropriate to replace the material
in the draft report with a less detailed version and place in an
Appendix a comprehensive annotated set of sensitivity ease results.
A graphical presentation on the response of the four
alternative ocean/atmosphere interaction models to increased CQ2
was given to the Subcommittee at its meeting on April 5, This
material will be a useful addition to the report. Some attention
to the evaluation of scenarios with and without stabilizing policy
in the post-2100 period would also be a useful addition to the
report, one issue of concern is the potential for additional sea
level rise in the post-2100 period from the melting of glacial ice.
Chapters vill and IX need extensive revision. These chapters
were intended as an overview of a range of policy options, but
their focus is too limited to' near-term alternatives for reducing
energy use. These chapters do not build on the modeling results of
chapters V and VI, taut rather reflect the judgment of energy
experts at EPA workshops. The Subcommittee believes that far more
attention should be given , in the report to energy RID and
commercialization options and to examination of means to facilitate
emissions reduction in developing countries that are consistent
with the aspirations ^»f these countries for energy, development and
economic growth. •
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Th« discussion of policy initiatives for near-term reduction
in energy use has useful aspects but also som* limitations. The
discussion la a compendium of ideas, with relatively little
rationale for selection of options or setting priorities among the
options. Members of the Subcommittee questioned whether the
material presented had the appropriate level of detail and balance.
For example, the increased number of light trucks in the United
States vehicle fleet has significant implications for fuel economy
that should be discussed. More emphasis might be placed on "gas
guzzler" and fuel tax initiatives, as opposed to the extensive
consideration given to regulation through fuel economy standards.
More discussion is needed on the experience in the United States
and European countries with policy initiatives, particularly
problems to be overcome.
The policy options for stabilization are not limited to those
that can be implemented in the next decade. Some of the most
important actions that the United States might undertake involve
the development of new technologies, institutions, and incentives
that will permit large reductions in emissions in the 21st century.
Decisions to deploy these technologies, alter institutions, or
create new incentives are not necessary now. These decisions can
be made at a later time, when scientific research should give a
clearer picture of the consequences of global climate change, and
research on these longer-term policy initiatives should give
additional information on their problems and promise. However, to
support decisions in the early 21st century on stabilization, such
investigations need to be pursued vigorously during the remainder
of this century.
8"Q SUMMARY WITH RE5PBCT TO THE 80BCQMMITTEE'8 CHARGE
In general, the technical adequacy of the draft stabilizing
Report is good; the report will be extremely useful as a compendium
of information relevant to the assessment of stabilising options,
and the basic analysis framework is appropriate. The main technical
deficiencies are the lack of documentation of the chapter V
analysis models and detailed results,* the omissions in Chapters
VIII and IX, especially on R4D, technology, transfer, and
commercialization? and the lack of cost information on the
technologies and stabilizing options.
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The draft stabilizing Report does a reason*bl« job of
presenting uncertainties, especially on the scientific issu** in
Chapters I through IV. it could do more in discussing
uncertainties in the extent to which new and emerging technologies
can contribute to reducing emission rates of the radiative active
gases.
The draft Stabilizing Report presents findings and
conclusions, rather than recommendations; in most cases, these
findings and conclusions are supported by the material assembled
in the text. The Report does not address stabilizing atmospheric
concentrations of greenhouse gases at levels near the present
composition of the atmosphere: the authors judged this to be an
infeasible goal, and the Subcommittee agrees with this judgment.
The problem of stabilizing emission rates of these greenhouse gases
and limiting the extent of potential climate change in th* next
century appears to be formidably difficult? the problem of
stabilizing atmospheric concentrations will be far more difficult.
The Subcommittee believes that assessment of the potential
effects of global climate change, evaluation of stabilizing
options, and research on climate change, on effects, on
technologies that may reduce emission rates, and on the
institutional and implementation issues in deploying these
technologies should all be pursued immediately and vigorously as
part of a coordinated program, within EPA, within the federal
government, , and through international organizations. The global
climate change work accomplished by EPA that the Science Advisory
Board has reviewed should be a useful initial step toward this
program of coordinated planning and research.
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