Global Warming: Emission Reductions Possible as Scientific Uncertainties Are Resolved

Published by the Government Accountability Office on 1990-09-28.

Below is a raw (and likely hideous) rendition of the original report. (PDF)

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     Resources, Community, and
     Economic Development  Division


     September Z&l990

     The Honorable Mike Synar
     Chairman, Environment, Energy, and
       Natural Resources Subcommittee,
     Committee on Government Operations
     House of Representatives

     Dear Mr. Chairman:

     This report provides an overview of federal research on global warming and identifies policy
     issues for dealing with climate change. It is intended to provide a framework for
     understanding the science and policy issues concerning global climate change.

     As agreed, unless you publicly release its contents earlier, we will make no further
     distribution of this report until 30 days from the date of this letter. At that time, we will
     send copies to the Administrator of EPA, Members of Congress, and other interested parties.
     We will make copies available to others upon request. If you have any questions about the
     report, please call Richard L. Hembra, Director, Environmental Protection Issues, at (202)
     275-6 111. Other major contributors are listed in appendix V.

     Sincerely yours,

      Assistant Comptroller General
Executive Summ~

                     Growth in industry, agriculture, and transportation over the last several
Purpose              centuries has resulted in the increase in “greenhouse” gases, which may
                     produce long-term and perhaps dramatic changes in global climate. The
                     results of this increase may be higher sea levels and changes in agricul-
                     tural productivity and in ecosystems.

                     In response to a request by the Chairman, Environment, Energy, and
                     Natural Resources Subcommittee, House Committee on Government
                     Operations, this report

                   + describes what is known and not known about greenhouse gases,
                   . examines the strengths and limitations of est,imates of enhanced global
                     warming, and
                   . identifies possible policy responses.

                     Gases, such as carbon dioxide, methane, chlorofluorocarbons (CFCS), and
Background           nitrous oxide are building in the atmosphere, where they trap heat and
                     cause the earth to warm. This phenomenon is enhancing the natural
                     greenhouse effect that maintains the earth’s current average tempera-
                     ture at about 60 degrees Fahrenheit.

                     To understand the effect of increases in greenhouse gases, scientists use
                     complex computer models, known as general circulation models, to ana-
                     lyze future climate changes. Four federal agencies operate or fund such
                     models: the Department of Energy (DOE), the National Aeronautics and
                     Space Administration (NASA), the National Oceanic and Atmospheric
                     Administration (~‘oAA), and the National Science Foundation (NSF). Addi-
                     tional research on global climate change is conducted primarily by these
                     agencies and the U.S. Department of Agriculture, the Environmental
                     Protection Agency (EPA), and the U.S. Geological Survey. Funding
                     devoted primarily to research in climate change by these seven agencies       j
                     was over $660 million in fiscal year 1990. The administration’s budget
                     for fiscal year 1991 proposed increasing funding to over $1 billion.

                     Industrial and agricultural activities are causing the atmospheric con-
Results in Brief     centrations of some greenhouse gases to exceed historic levels. Without
                     action now, these concentrations are expected to grow, although the rate
                     of increase is uncertain. From their review of computer modeling
                     results, most climate scientists agree that the climate’s response to this
                     growth will be an increased average temperature over the next 100

                     Page 2                                         GAO/RCED9O-58   Global Wan&g
                          Executive   Summary

                          years. They do not concur, however, on the timing and magnitude of this
                          change or on the associated regional climate changes.

                          While research should reduce these scientific uncertainties, quick fixes
                          or easy answers are unlikely to emerge. Rather, research results are
                          expected to continue pointing to the need for a comprehensive multina-
                          tional, multidecade response strategy. In the meantime, however, many
                          agree that certain actions can be justified because they have benefits in
                          addition to reducing greenhouse gases. Reducing CFCS is an example of
                          one such activity already underway, and more can be done in other
                          areas, such as improving energy efficiency.

Principal Findings

Causesof Global Warming   Concentrations of greenhouse gases are increasing primarily because of
                          fossil fuel combustion and the use of nitrogen fertilizers and CFCS. Green-
                          house gases are expected to increase because of these activities,
                          although at an uncertain rate.

                          Carbon dioxide is responsible for about half of the contribution green-
                          house gases make to global warming. Since the beginning of the indus-
                          trial revolution, the level of carbon dioxide has increased about 25
                          percent and is approaching the maximum amount that scientists believe
                          has occurred naturally over the past million years. According to DOE,
                          difficulties in estimating future levels may be due, in part, to problems
                          in modeling fossil fuel emissions on a loo-year time scale and uncertain-
                          ties in modeling natural ocean and terrestrial processes that emit carbon
                          dioxide and remove it from the atmosphere.

                          To better estimate the growth of greenhouse gases, scientists have iden-
                          tified the need for (1) further research on the chemical, biological, and
                          geophysical processes that. affect changes in atmospheric concentrations
                          and (2) improved, long-term monitoring of atmospheric trends. Federal
                          agency scientists expect that the research they have planned and are
                          undertaking will produce more precise estimates of increases in green-
                          house gases. These estimates, in turn, should help researchers and
                          policymakers to understand how and when these gases may affect the
                          climate and to devise strategies to limit their growth.

                          Page   3                                       GAO,‘BCED-!+!I-68   Global Warming
                              Executive   Summary

Estimates of the Effects of   According to current estimates of climate change made by five general                  ;
                              circulation models, the average global temperature will increase by 3 to               1
GreenhouseGaseson             9 degrees Fahrenheit over the next century, assuming a doubling of the
Future Climate                effect of greenhouse gases. Even the lower of these estimates could be
                              the most rapid temperature increase the earth has ever experienced.
                              Although such temperature increases have not yet been detected, some
                              scientists believe that the warming could soon become noticeable to the
                              average person.
                              Some models also predict (1) greater warming near the poles than
                              around the equator, (2) changing rainfall patterns, and (3) rising sea
                              levels. However, the models are inconsistent on regional climate changes              I
                              and specific time frames for changes. For example, a NOAA model esti-
                              mated that summers would be drier than normal in the southeastern
                              United States, while a NASA model estimated the opposite.

                              Limitations in the models affect their accuracy and are responsible for
                              their differing results. First, general circulation models divide the earth           1
                              into a gridwork of boxes, each usually 300 miles square. The large area               1
                              covered by a box means that small-scale meteorological phenomena,
                              such as thunderstorms and clouds, cannot be included in the models or                 i’
                              must be simplified, and that variations in temperature and rainfall, for
                              example, cannot be taken into account. Second, processes that may
                              amplify warming or cooling effects are inadequately incorporated into
                              the models. For example, the manner in which the models simplify com-              1
                              plex interactions between the ocean and atmosphere accounts for some              11
                              differences in their estimates.
                              Ongoing and planned research is addressing these limitations and is
                              expected to improve estimates of climate change. Plans include (1)
                              research to better understand climate processes, (2) long-term measure-           :
                              ments of climate change, and (3) more computer resources. Improved
                              estimates will help policymakers to develop a strategy to mitigate or
                              prepare for possible climate changes.                                             I

Policy Issues                 Although the extent, magnitude, and timing of global warming are
                              uncertain, past and current emissions of greenhouse gases probably
                              make warming unavoidable. National and international policymakers
                              are discussing ways to reduce man-made emissions and to adapt to pos-
                              sible impacts of global climate change and risks that may result from             i
                              delaying action. By acting now to reduce greenhouse gas emissions

                              Page 4                                          GAO/RCED-90-68   Global Warming

                  rather than waiting for better information, policymakers may minimize
                  potentially harmful changes to the environment.

                  Developing a worldwide strategy to slow global warming will be eco-
                  nomically and politically contentious because it will involve a decreased
                  reliance on fossil fuels, which currently provide over 75 percent of the
                  world’s energy. Fossil fuel consumption can be reduced by improving
                  the efficiency of energy use or by replacing fossil fuels with alternative
                  energy sources, such as solar or nuclear power.

                  In preparing for global warming, policymakers must therefore weigh the
                  risk of more adverse impacts by delaying action while they wait for
                  additional scientific information against prematurely taking costly
                  actions that may prove unwarranted. Nevertheless, it has been argued
                  that actions can be taken now to reduce greenhouse gas emissions that
                  will have other benefits, such as lessening dependence on foreign oil and
                  improving air quality.

                  This report was intended to describe global warming research and policy
Recommendations   issues and thus contains no recommendations,

                          and EPA generally agreed that the report was useful to policy-
Agency Comments   NASA
                  makers, but NASA, DOE, and NOAA recommended including more current
                  information. This report was therefore updated to reflect the final
                  report of the Intergovernmental Panel on Climate Change, to be issued
                  later this year. EPA also recommended adding information on the effects
                  of climate on living systems, but GAO'S intent in this report was to focus
                  initially on estimates and causes of global climate change. NOAA and DOE
                  advised including information on costs and benefits of emissions reduc-
                  tion. Recognizing that economic tradeoffs have to be considered in any
                  emission reduction strategy, GAO nevertheless believes that actions could
                  be implemented now that have benefits beyond reducing emissions

                  Page 6                                         GAO/RCEIM04V3   GlobalWarming


Executive Summary                                                                                      2
Chapter 1                                                                                             10
Introduction                Background                                                                10
                            Objectives, Scope, and Methodology                                        16

Chapter 2                                                                                             19
Greenhouse Gases            Agreement Exists on the Greenhouse Effect of Certain                      19
Increasing at               Future Growth of Greenhouse Gases Uncertain                               22
Uncertain Rate              Keed for Improved Understanding of Processes                              27
                                Controlling Greenhouse Gases and for Better Data
                            GAO’s Observations                                                        28
                            Agencies’ Comments                                                        28

Chapter 3                                                                                             30
Global Warming              Estimates by Climate Models                                               30
Estimates   Expected   to   Models’ Limitations                                                       34
                            Implications of the Models’ Limitations                                   38
Improve as Research         Requirements to Improve GCMs                                              39
Continues                   GAO’s Observations                                                        42
                            Agencies’ Comments                                                        42

Chapter 4                                                                                        ,. 44
Policy Framework to         Nature of the Problem                                                ’    44
                            Actions to Respond to Global Warming                                      47
Address Global              U.S. Options to Reduce Greenhouse Gas Emissions                           56
Climate Change              Timing of Responses to Global Warming                                     57
                            GAO’s Observations                                                        58
                            Agencies’ Comments                                                        59

Appendixes                  Appendix    I: DOE’s Comments                                             60
                            Appendix    II: EPA’s Comments                                            62
                            Appendix    III: NASA’s Comments                                          66
                            Appendix    IV: NOAA’s Comments                                           68
                            Appendix    V: Major Contributors to This Report                          72

 Tables                     Table 1.I : Federal Agencies* Budgets for Research on                     15
                                Global Climate Change

                            Page 6                                         GAO/RCEtHMMS   Global Warming

          Table 2.1: Summary of Information on Several                                 21
              Greenhouse Gases
          Table 2.2: Annual Growth Rates and Sources of                                24
              Greenhouse Gases
          Table 3.1: Average Global Warming Estimated by GCMs                          31
              for a Doubling of Carbon Dioxide
          Table 3.2: GFDL Estimates of Climate Change                                  33

Figures   Figure 1.1: How the Greenhouse Effect Works                                  11
          Figure 1.2: How One General Circulation Model Works                          13
          Figure 2.1: Contributions of Greenhouse Gases to Global                      20
               Warming During the 1980s
          Figure 2.2: Carbon Dioxide Levels and Temperature                            22
               Changes Over the Last 160,000 Years
          Figure 2,3: Concentration of Atmospheric Carbon Dioxide                      23
               at Mauna Loa Observatory, Hawaii
          Figure 3. I: Precipitation Estimates for the Southeastern                34
               United States
          Figure 3.2: GCM Grids (Measuring 4 by 5 Degrees) Over                    35
               the United States
          Figure 4.1: Regional Contributions to the Greenhouse                     45
               Effect During the 1980s
          Figure 4.2: Activities Contributing to Global Warming                    46
          Figure 4.3: Gains in Energy Efficiency in the United                     50
               States From 1973 to 1988

          Page 7                                        GAO/‘RC~SII   Global Wanuing


CFC        chlorofluorocarbon
DOE        Department of Energy
WI         Department of the Interior
EPA        Environmental Protection Agency
ERBE       Earth Radiation Budget Experiment
FEMA       Federal Emergency Management Agency
GAO        General Accounting Office
GCM        general circulation model
GFDL       Geophysical Fluid Dynamics Laboratory
GISS       Goddard Institute for Space Studies
GNP        gross national product
IPCC       Intergovernmental Panel on Climate Change
NASA       National Aeronautics and Space Administration
KCAR       National Center for Atmospheric Research
KOAA       National Oceanic and Atmospheric Administration
NSF        National Science Foundation
OSU        Oregon State University
PPMV       parts per million by volume
TRMM       Tropical Rainfall Measuring Mission
USDA       U.S. Department of Agriculture
USGS       U.S. Geological Survey

Page 8                                        GAO/RCmNcIB    Global WarmIng
Page 9   GAO/RCED-90-58   Global Warming

              Growth in industry, agriculture, and transportation for over a century
              has resulted in the buildup of heat-trapping “greenhouse gases” that
              may be creating an unprecedented, worldwide environmental problem.
              As the earth warms rapidly under the effect of these greenhouse gases,
              species may become extinct, sea levels may rise, and weather and agri-
              cultural patterns may be altered. Given such potential changes, scien-
              tists and policymakers around the world are examining what can be
              done to prevent or mitigate an enhancement of the greenhouse effect.

              Climate and weather are determined by complex interactions of the
Background    atmosphere, land surface, snow, sea ice, and oceans, involving the
              exchange of energy within and among these components. These interac-
              tions vary considerably from day to day, month to month, and year to
              year. Changes in the amount of energy emitted by the sun, changes in
              the atmospheric composition (because of volcanic eruptions and emis-
              sions of aerosols and greenhouse gases), and changes in the earth’s sur-
              face (such as deforestation) can also cause the earth’s energy balance,
              and, hence, climate to vary.

              Greenhouse gases-such as water vapor, carbon dioxide, methane,
              nitrous oxide, and ozone-occur naturally in the atmosphere. They
              serve as a figurative thermal blanket that absorbs the earth’s infrared
              radiation and re-radiates it downward, trapping part of the heat that
              would otherwise radiate into space. (See fig. 1.1.) This process warms
              the earth’s surface and lower atmosphere so that an average global tem-
              perature of about 60 degrees Fahrenheit is maintained. Many scientists
              and policymakers are concerned, however, that if concentrations of
              these natural greenhouse gases and synthetically produced chloroflouro-
              carbons (CFC) increase, the atmospheric temperature will also increase.

              Page 10                                       GAO/RCED-9f.68   Global Warning
                                            Chapter 1

Figure 1 .l : How the Greenhouse   Effect

                                            Source, Based on W R. Moomaw, “The Basis of the Greenhouse Effect” (Washington, D C World
                                            Resources Institute, Sept. 16, 1988), p. 2, and J B. Smith and D.A. Tlrpak (eds.), The Potential Effects of
                                            Global Climate Change on the Unlted States, EnvIronmenta! Prolecllon Agency, draft (Washington, D C
                                            Ott 1988), p. 2-3.

Computer Modeling of                        Scientists use complex computer models, called general circulation
Climate Change                              models (GCM), as one means of estimating climate changes based on vari-
                                            ations in greenhouse gases.’ GCMS apply equations representing basic
                                            physical laws, such as the conservation of energy, to the atmosphere,
                                            oceans, and ice sheets. These basic laws are then combined with more
                                            detailed processes, such as the reflectivity of clouds.

                                            These equations are too complex to be solved exactly; consequently,
                                            modelers create a discrete number of grid boxes around the globe in
                                            which solutions to the equations are approximated, as shown in figure
                                            1.2. Roughly, the grid boxes in some GCMS are about 300 miles by 300
                                            miles. The size of the grid box determines the level of analysis (resolu-
                                            tion). Anything that occurs on a smaller scale is not explicitly treated in

                                            ‘EPA has noted that several other modeling and analytical techmques are used to study climate
                                            changes, such as radiative-convective models and chemical models. Like GCMs, each analytical tool
                                            has its strengths, weaknesses, and domain of usefulness.

                                            Page 11                                                              GAO/RCED-90-58      Global Warming

the model, but is instead approximated within each grid box. These grid
boxes allow scientists to compromise between the need to include rele-
vant processes and interactions and the need to run the models on avail-
able computers in reasonable periods of time. Even so, 1 year of modeled
time on a GCM might take 26 hours of super-computer time; thus, each
complete run would normally take thousands of computer hours.

Page 12                                      GAO/RCED90-68   Global Warming
                                             Chapter 1

Figure 1.2: How One General Circulation   Model Works


   l Earth is divided into a gridwork of 1,920
   “boxes” about 300 miles on a side.

   l The atmosphere     above each box is divided
   into 9 layers.

   l    The ocean under each box is divided into
       12 layers.

   l Each layer’s program includes initial                  Ocean
   conditions (such as winds and temperature)               Surface
   and formulas for basic physical laws (such
   as the conservation of energy).

   9 The computer calculates how processes in
   each layer affect conditions in each                                                                                           12 Layers
   neighboring layer and feeds that data into                Ocean
   adjoining layers.                                          Floor

   * The computer repeatedly recalculates as
   modeled days pass into months. As
   seasons change, it varies the amount of

                                             Source Based on W Booth, “Computers     and ‘Greenhouse Effect’ The Genesis of UnderstandIng,”   The
                                             Washlngton Post, June 12, 1989, p A3.

                                             Page 13                                                         GAO/RCED-90-68     Global Warming
                             Chapter 1

                             Because different modelers use different methods to approximate
                             processes that affect clouds, oceans, and seasonal cycles, each GCM dif-
                             fers somewhat in its computational structure. For example, some GCMS
                             have day/night cycles, while others do not. In addition, most GCMS use
                             very simple representations of the ocean (for example, representations
                             not including ocean currents), each in its own way.

                             Several groups of scientists have been developing GCMSover the past 2
                             decades. In 1975, researchers at the National Oceanic and Atmospheric
                             Administration’s (NOAA) Geophysical Fluid Dynamics Laboratory
                             reported the first attempt to use a full GCM to study carbon dioxide-
                             induced climate change. Today, several federal agencies are using GCMS
                             to study the potential climate impacts of increasing greenhouse gases:
                             the National Aeronautics and Space Administration’s (NASA) Goddard
                             Institute for Space Studies, NOAA’s Geophysical Fluid Dynamics Labora-
                             tory, the National Science Foundation’s (NSF) National Center for Atmos-
                             pheric Research, and DOE-funded research at Oregon State University.2

Federal Involvement in       Federal research on global climate change is conducted primarily by
                             seven federal agencies. All of this research relates directly or indirectly
Global Climate Change        to the global warming issue. Research by these agencies encompasses
Research                     the chemical, biological, and physical processes that affect climate
                             change; the influence of human activities on global climate and vice                                   i
                             versa; and ways to adapt to or limit global climate change.3 Specifically,

                         l   the Department of Energy (DOE) focuses on energy technology develop-
                             ment, atmospheric research, modeling analysis, impact analysis, and
                             economic analysis for potential responses;
                         l   the Environmental Protection Agency (EPA) evaluates options to slow
                             the rate of global climate change, assesses the effectiveness of such
                             options in protecting environmental resources, and assesses feedback
                             effects involving greenhouse gases;

                             2The Oregon State University model is now run by the University of Illinois. Other groups in the
                             United States running GCMs include the University of California at Los Angeles, Colorado State Uni-
                             versity, and XASA’s Goddard Space Flight Center. However, these groups do not study long-ten-o
                             climate change with their models.

                             3Recently GAO examined federal agencies’ coordination and U.S. participation in international activ-
                             ities conckning global warming activities (Global Warming: Administration Approach Cautious
                             Pending Validation of Threat, GAO/NSLAD-90-63, Jan. 8, 1990) and DOE’s research activities on
                             global warming (Greenhouse Effect: DOE’sPrograms and Activities Relevant to the Global Warm%
                             Phenomenon, GAO/RCED-90-74BR, Mar. 5,199O).

                             Page 14                                                         GAO/RCED-90-58     Global Wamdng
                                                 Chapter 1


                                             . NASA is responsible for earth science research from space, including
                                               broad scientific studies of the planet as an integrated system;
                                             . the Department of Commerce’s NOM emphasizes improving estimates of
                                               climate change and the regional implications of that change, including
                                               climate research and modeling, oceanic and atmospheric monitoring and
                                               analysis, and the collection and management of climate data;
                                             . NSF’S Global Geosciences Program supports university-based basic
                                               research in earth, atmospheric, and ocean sciences;
                                             l the U.S. Department of Agriculture (USDA) researches the climate’s
                                               impact on agriculture and ecological systems and the impact of those
                                               systems on the climate; and
                                             l the Department of the Interior’s (DOI) U.S. Geological Survey (USGS)
                                               researches past climate changes and processes related to climate change,
                                               such as the interaction of hydrologic and ecological systems with

                                                 The funding devoted primarily to research on climate change by these
                                                 agencies in fiscal year 1990 was approximately $660 million, and the
                                                 proposed budget for fiscal year 1991 would increase funding to over $1
                                                 billion. Table 1.1 shows each agency’s share of the research budget for
                                                 fiscal year 1990 and the proposed budget for fiscal year 1991.

Table 1.1: Federal Agencies’ Budgets   for
Research on Global Climate Change                Dollars   in Milllons
                                                                                 -.----         .__.
                                                                                                  - __...
                                                 Agency                  -.-..                              Fiscal year 1990          Fiscal year 1991
                                                 DOI                                                                   $133                        $43.7
                                                 DOE                                                                     50 0                        66.0
                                                 EPA                                                                     154                         24.0
                                                 NASA                                                                  488 6                       661 .o
                                                 NOAA                                                                    180                         87.0
                                                 NSF                                                                     55 0                       103.0
                                                 USDA      -~                                                            21.2                        47.4
                                                 Total                                                                $661.5                    $1032.1
                                                 Note. The U S Global Change Research Program includes climate, ecological, btogeochemical. and
                                                 solld earth processes: human acttvltles that affect such processes: and the sun’s influence on the earth
                                                 Enhanced global warmlng IS an Important element In this research program.

                                                 Sources Committee on Earth Science and EPA

                                                 4Several other agencies are involved in this issue. The Department of State is the lead agency for
                                                 coordinating and setting policy for U.S. participation in international programs, and the National
                                                 Academy of Sciences’ Committee on Global Change is the federal advisory body for establishing pri-
                                                 orities for research on global climate change.

                                                 Page 15                                                            GAO/RCED!WSS        Global Warmlug
                             Chapter 1

                             Federal research on global warming is coordinated by the Committee on
                             Earth Sciences, an interagency group of the Federal Coordination
                             Council for Science, Engineering, and Technology, under the direction of
                             the President’s Science Advisor.

                             The Chairman, Environment, Energy, and Natural Resources Subcom-
Objectives, Scope, and       mittee, House Committee on Government Operations, requested that we
Methodology                  examine the science and policy issues concerning climate change. Specif-
                             ically, our objectives were to

                         4 describe what is known and not known about greenhouse gases,
                         l describe the strengths and limitations of models used to estimate global
                           warming, and
                         l identify possible policy responses.

                             In fulfilling the first two objectives, we interviewed officials and
                             reviewed relevant studies and reports at NSF headquarters and the NSF-
                             funded National Center for Atmospheric Research; DOE headquarters
                             and the Do&funded climate research program at Lawrence Livermore
                             National Laboratory; NASA headquarters, Goddard Space Flight Center,
                             and Goddard Institute of Space Studies; and NOAA headquarters and its
                             National Climate Program Office, Geophysical Fluid Dynamic Labora-
                             tory, and Aeronomy Laboratory. In addition, we interviewed officials at
                             the Committee on Earth Sciences, EPA, the National Academy of Sci-
                             ences, USDA, and USGS.However, we did not inventory all federal
                             research being conducted on global warming because of the large
                             number of projects currently underway and the breadth of topics being
                             studied. Furthermore, new findings based on this research are fre-
                             quently being reported in the scientific literature. This report discusses
                             research reported as of October 1989. It was updated to reflect more
                             recent findings as appropriate.

                             In addition, we attended several major conferences on climate change
                             and spoke with representatives of several nonfederal organizations
                             involved in global warming studies for information on the causes,
                             effects, and estimates of global warming: Columbia University’s Lamont-
                             Doherty Geological Observatory, the Environmental Defense Fund, the
                             Joint Oceanographic Institutions, the National Academy of Sciences’
                             Committee on Global Change, the Natural Resources Defense Council,
                             the Pacific Institute, Resources for the Future, the University Corpora-
                             tion for Atmospheric Research, the University of Maryland’s Laboratory

                             Page 16                                        GAO/lUXlNM8   Global Rhrdu~~
Chapter 1

for Coastal Research, the [Jniversity of Virginia, and the World
Resources Institute.

In addressing the first objective, we gathered information on the life
spans, rates of growth, sources, and radiative effects of greenhouse
gases. We obtained information on research that is needed to address
areas of uncertainty.

To pursue the second objective, we gathered information on general cir-
culation models, which are a basis for climate change estimates. We
compared the findings of four climate models funded by federal agen-
cies--NOAA’s Geophysical Fluid Dynamics Laboratory, NASA’SGoddard
Institute of Space Studies, NSF’SNational Center for Atmospheric
Research, and Oregon State llniversity (funded by NSFand WE)-and
obtained opinions from the researchers at these institutions and others
in the scientific community on the models’ strengths and limitations.5 We
chose these four modeling groups because they were identified as the
only federally funded groups using general circulation models to study
long-term climate change. Where appropriate, we also included findings
from the climate model run by the United Kingdom’s Meteorological
Office. In meetings with the modeling groups, we also discussed uncer-
tainties surrounding the causes and effects of global warming. In addi-
tion, WCvisited Lawrence Livermore National Laboratory, which
conducts research on climate modeling, including a project comparing
climate models. At Lawrence Livermore Laboratory, we obtained infor-
mation on how the various models used to estimate climate change COEI-
pare in structure and output. We also reviewed the draft executive
summary of a report by the Intergovernmental Panel on Climate Change
(IIYX) containing a scientific assessment of climate change.

As part of our second objective, we assessed how research on the effects
of climate change is influenced by limitations in the climate models.
Using one of the most certain effects of global warming, a rise in sea
level, as a case study, we gathered information on how well effects can
be assessed, given the uncertainties in forecasting climate change. We
interviewed scientists at EPA,Joint Oceanographic Institutions, and the
University of Maryland’s Coastal Research Laboratory who have been
studying the rise in sea lcvcl associated with climate change. We gath-
ered information on the effects of a rise in sea level, the populations

“We did not interview researchers at Oregon State University. During our review, the chief rlimate
modelers left the university. (km.sxxpently, the university no longer xmducts climate research.

Page 17                                                          GAO/RCED-9@58      Global Warming
Chapter    1

that would be most greatly affected, and time frames for the expected

To address our third objective, we obtained information on policy issues
from the following environmental and industry groups: the American
Nuclear Energy Council, the American Petroleum Institute, the Center
for Energy and Environmental Studies at Princeton IJniversity, the Cli-
mate Institute, the Edison Electric Institute, the Electric Power Research
Institute, the Environmental and Energy Study Institute, the Motor
Vehicle Manufacturers Association, the National Association of Manu-
facturers, the Kational Coal Association, the Natural Resources Defense
Council, Public Citizen, Renew America, Resources for the Future, the
Solar Energy Industries Association, the ITS. Public Interest Research
Group, and Worldwatch Institute. We also discussed responses to global
warming with officials at federal agencies, particularly EPA and IK)E.

Our work was conducted between November 1988 and October 1989 in
accordance with generally accepted government auditing standards.
Information was updated through August 1990. DOE, EPA, NASA, NOAA,
and NSF were given the opportunity to comment on a draft of this report.
NSF declined to respond. The other agencies’ responses are in appendixes
I through IV.

Page 18                                        GAO/RCED-90-58   Global Warming
Chapter 2

GreenhouseGasesIncreasing at Uncertain Rate

                           Fossil fuel combustion and other human activities are emitting gases
                           into the atmosphere that could result in long-term changes to global cli-
                           mate. The increased atmospheric warming that may be caused by these
                           gases is known as an enhanced greenhouse effect, which, until recently,
                           was believed to be caused solely by increases in carbon dioxide. It is now
                           known that other gases- such as methane, CFCS,nitrous oxide, and
                           ozone-in the lower atmosphere, when taken together, are also very
                           important and may soon surpass carbon dioxide as the primary contrib-
                           utors to enhanced global warming. The atmospheric concentrations of
                           these gases are increasing, although their future rates of growth are
                           uncertain because the biological, physical, and chemical processes that
                           regulate their atmospheric concentrations are not fully understood, The
                           sources of CFCS and carbon dioxide have been identified better than the
                           sources of the other greenhouse gases. The research being undertaken
                           and planned by several federal agencies is expected to help resolve the
                           uncertainties surrounding the sources and processes that regulate the
                           concentration of greenhouse gases.

                           For nearly 100 years, scientists have known that a buildup of carbon
Agreement Exists on        dioxide in the atmosphere has the potential to warm the earth by
the Greenhouse Effect      enhancing the natural greenhouse effect that maintains the average
of Certain Gases           global temperature at about 60 degrees Fahrenheit. Over the past 10
                           years, however, awareness has grown in the scientific community that
                           other greenhouse gases, when taken together, have a warming effect
                           comparable to that of carbon dioxide. Almost all climate scientists
                           believe that increases in greenhouse gases are very likely to raise the
                           average global temperature. This belief is based on calculations derived
                           from well-established physical principles and is supported, in part, by
                           the study of other planets and by analyses of past glacial and intergla-
                           cial climates on earth that show a close relationship between changes in
                           global temperature and changes in the atmospheric concentration of
                           some greenhouse gases,

Carbon Dioxide Is          Scientists estimate that during the 1980s about half of the greenhouse
Responsible for Half the   gases’ contribution to global warming was due to increases in carbon
                           dioxide and half was due to increases in the other greenhouse gases
Enhanced Greenhouse        combined (see fig. 2.1). The relative contribution of each gas to
Warming                    increased atmospheric heating is determined by its ability to absorb
                           infrared radiation and its atmospheric abundance. Atmospheric abun-
                           dance is determined by the quantities being emitted and the lifespan of
                           the gases in the atmosphere. For example, methane is about 25 times

                           Page 19                                        GAO/RCED90-58   Global Wamhg
                                          Chapter 2
                                          Greenhouse Gases Increasing      at
                                          Uncertain Rate

                                          more efficient per molecule in absorbing infrared radiation than carbon
                                          dioxide, but its contribution to atmospheric warming is currently much
                                          lower than carbon dioxide because methane is not as abundant.

Figure 2.1: Contributions of Greenhouse
Gases to Global Warming During the


                                                                                                  Carbon Dioxide

                                                    I                                            CFCs
                                          Note: The “Other” category Includes halons, tropospheric ozone, and stratosphenc water vapor. The
                                          percentages are based on eshates    of Increases in concentration of each gas during the 1980s.
                                          Source. D.A. Lashof and D A Tlrpak (eds ), Policy Options for Stabllizlng Global Climate, EPA, draft
                                          (Washington. D.C Feb 1989), p. 11-M.

                                          Table 2.1 summarizes information on the atmospheric concentration,
                                          lifetime, and atmospheric heating contribution of several greenhouse
                                          gases. It is based on a 1988 DOEreport that evaluated the current scien-
                                          tific understanding of basic information on numerous greenhouse gases
                                          and a similar report by EPA.’

                                          ‘This information has been updated to reflect more recent findings by the Intergovernmental Panel
                                          on Climate Change.

                                          Page 20                                                           GAO/RCED-go-58     Global   Warming
                                       Chapter 2
                                       Greenhouse Gases Increasing      at
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Table 2.1: Summary of InfOrmatiOn on
Several Greenhouse Gases                                                                                                         Atmospheric
                                                                                      Atmospheric                                per molecule
                                                                                     concentration        Atmospheric               relative to
                                       Greenhouse gas                                       (ppmv)”   lifetime (years)         carbon dioxide
                                       Carbon dioxide                                            353           50to 200                         1
                                       Methane                                                    172            7to10                About25
                                       Nitrous oxtde                                             0.31         About150               About230
                                       CFC-11                                                0.00028                  65          Abo;t 16,000
                                       _ I-~    ~~~~~~~ ~~~
                                       CFC-12                                               0.000484                130           AboutZ1,OOO
                                       aParts per million by volume.
                                       Sources. D.J Wuebbles and J Edmonds, A Primer on Greenhouse Gases, U.S. Department of Energy,
                                       Office of Energy Research (WashIngton. D.C : March 19t38), pp 2-39, and Lashof and Tlrpak, Poky
                                       OptIons for Stablllzlng Global Clrmafe, pp. II-29 to 11-39.This informatIon has been updated in “policy-
                                       makers Summary of the Scientific Assessment of Climate Change,” IPCC, draft (May 25. l%O), p. 7.

Historic Increases in                  Most scientists believe that the eventual response to increases in green-
                                       house gases will very likely be, on average, global warming. There is
Carbon Dioxide Have Been               historic evidence, based on analyses of air samples trapped in ice, that
Associated With Climate                long-term changes in temperature are correlated with changes in the
Change                                 atmospheric concentration of carbon dioxide. Analyses indicate that the
                                       carbon dioxide level varied between a low near 200 parts per million in
                                       cold, glacial times and a high near 280 parts per million (but currently
                                       about 350 parts per million) in warm, interglacial times. Recent analyses
                                       show direct evidence of these trends over the last 160,000 years.2 As
                                       shown in figure 2.2, two large increases in temperature and carbon
                                       dioxide occurred about 15,000 years ago and nearly 140,000 years ago.
                                       The low carbon dioxide concentrations generally correspond to the gla-
                                       cial conditions that prevailed for most of the last 100,000 years.
                                       Whether the level of carbon dioxide was a response to or contributed to
                                       the temperature changes is uncertain.

                                       *.J. M. Barnola et al., “Vostnk Ice Core Provides 160,000-year Record of Atmospheric CO”,” e,
                                       vol. 329 (1987). pp, 408-14.

                                       Page 21                                                             GAO/RCED-90~5B      Global Warming
                                        Chapter    2
                                        Greenhouse       Gases Increasing      at
                                        Uncertain      Rate

Figure 2.2: Carbon Dioxide Levels and
Temperature Changes Over the Last       I
160,bOO Years      -


                                        c        240
                                        8        220






                                                         vi0                    ii0        so                io                   0

                                                         Age: Thousands     of Years                                    Present

                                        Source, Barnola et al., “Vosak Ice Core Prowdes 160,000-Year Record,” p. 410

                                        The atmospheric concentration of carbon dioxide has been increasing at
Future Growth of                        least since the beginning of the industrial revolution. The concentrations
Greenhouse Gases                        of other greenhouse gases are also increasing. Estimates of future
                                        atmospheric levels of carbon dioxide and some of the other greenhouse
Uncertain                               gases, however, are uncertain primarily because the future emission
                                        rates are uncertain.

Carbon Dioxide Levels                   Carbon dioxide-produced    by fossil fuel combustion, deforestation,
Increasing                              cement manufacture, and respiration by living organisms-has
                                        increased in the atmosphere by about 25 percent since the beginning of

                                        Page 22                                                          GAO/RCED904S     Global WarmIng
                                                                            Chapter    2
                                                                            Greenhouse       Gases   Increasing           at
                                                                            Uncertain Rate

                                                                            the industrial revolution. Measurements taken by NOAA since 1958 reveal
                                                                            a continuous and possibly accelerating increase in the mean annual con-
                                                                            centration, as shown in figure 2.3. In 1958, the concentration was about
                                                                            315 parts per million; and in 1988, it was over 350 parts per million.
                                                                            According to a DOE study, all of the increase is due to human activities,
                                                                            predominantly fossil fuel combustion.3

Figure 2.3: Concentration               of Atmospheric                 Carbon Dioxide          at Mauna Loa Observatory,                                Hawaii
360      CO2 Concmlmtlon         (Pad       pr     Ull3on)




300                                        -.-.-..-m,.-.-__                                                   -..-.--.,                   ..-,,,., .,

      1958   ‘99   ‘99   ‘61   ‘62   ‘63         ‘64   ‘95    ‘I36   ‘67    ‘68   ‘69   70    71     m    m         74         ‘79   79     77          78   79   ‘99   ‘81   ‘82   ‘93   ‘84   ‘95      ‘88    ‘87   ‘88

                                                                           Note, The annual cycle shown in the figure IS a result of the seasonal photosynthetIc actlvrty In the
                                                                           Northern Hemisphere. That is, during the growing season more carbon dioxide IS drawn out of the
                                                                           atmosphere by photosynthesizlng plants than is released Into rt by resplratlon: In winter, the opposite is
                                                                           Source NOAA.

                                                                           Records at other NOAA sites, such as Antarctica, confirm that this
                                                                           increase is a global phenomenon. These records indicate that the carbon
                                                                           dioxide concentration in the atmosphere has increased by nearly 10 per-
                                                                           cent during the last quarter century and is approaching the apparent

                                                                           3D. J. Wuebbles and J. Edmonds, + Primer, p. 8. According to comments received from NOAA, this
                                                                           statement is somewhat strong in light of the present understanding of natural sources and “sinks” in
                                                                           the global carbon cycle. A major debate is currently underway on whether a m&or Northern Hemi-
                                                                           sphere “sink” exists.

                                                                           Page 23                                                                                      GAO/RCED-9668           Global         Warming
                                     Chapter 2
                                     Greenhouse Gases Increasing     at
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                                     limits of natural variation characteristic of the glacial-interglacial                            cycles
                                     of the past million years.4

Other GreenhouseGases                According to published reports, other greenhouse gases are similarly
Also Increasing                      increasing in concentration. (See table 2.2.) Although these gases occur
                                     naturally (except CFCS), their increases are caused nearly exclusively by
                                     human activities.

Table 2.2: Annual Growth Rates and
Sources   of Greenhouse Gases                                             Annual growth
                                     Gas                                  rate (percent)            Sources
                                     Carbon dioxide                       About 0 5                 Fossil fuel combustion
                                                                                                    Cement manufacturing
                                     Methane                              0.9                       Wetlands
                                                                                                    Rce paddies
                                                                                                    Cattle and sheep
                                                                                                    Biomass burninga
                                                                                                    Natural gas and mlninq losses
                                                                                                    Solid waste              -
                                     Nitrous   oxide                      0.25                      Fossil fuel combustion
                                                                                                    Fertilized and cultivated SOIIS
                                                                                                    Biomass burninga
                                     CFCs                                 4                         Refrigerator   coolants,     air
                                                                                                      conditioner coolants, insulating
                                                                                                      and packing foam, and aerosol
                                     Ozone                                Uncertain                 Chemical interactlons of hydro-
                                                                                                      carbons, carbon monoxide,
                                                                                                      methane, and nitronen oxide
                                     aBiomass is dry organic matter
                                     Sources: Smith and Tirpak, Potential Effects of Global Climate Change on the United States, pp 2-4, Z-
                                     10, and 2-l 1; and WuebbIes and Edmonds, Primer on Greenhouse Gases, pp. K-40. This informahon
                                     has been updated in “Policymakers Summary,” IPCC, p. 7.

                                     For example, the methane concentration increased in the atmosphere by
                                     about 1 percent per year from the early 1950s through the early 1980s.5
                                     Analyses of air trapped in ice indicate that the atmospheric concentra-
                                     tion of methane started increasing over the last several hundred years,
                                     after being constant for 10,000 years or more. It has increased to

                                     4R.H. Gammon, et al., “History of Carbon Dioxide in the Atmosphere,” in J.R. Trabalka(ed.), Atmos-
                                     pheric Carbon Dioxide and the Global Carbon Cycle, DOE (Washington, DC.: Dec. 1985), p. 27. The
                                     authors discuss the evolution of the concentration of carbon dioxide in the earth’s atmosphere during
                                     the last 100 million years

                                     ‘Wuebbles and Edmonds, Primer on Greenhouse Gases,p. 22.

                                     Page 24                                                           GAO/RCRB9MS             Global Warming
                      Chapter 2
                      Greenhouse Gases Increasing     at
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                      approximately double the natural levels of several centuries ago. Since
                      this increase corresponds with the growth of the human population and
                      industrial society, it is believed to be a result of increased methane emis-
                      sions from the expansion of rice agriculture, the raising of ruminant ani-
                      mals such as cattle and sheep, the storage of organic waste in landfills,
                      and the mining and use of fossil fuels.

Estimates of Future   It is uncertain whether the current growth rate in the atmospheric con-
                      centrations of carbon dioxide and other greenhouse gases will continue,
Atmosphe ric Levels   according to scientists.” In some cases, uncertainty is due to insufficient
Uncertain             understanding of the natural processes that affect their atmospheric
                      levels and/or difficulties in predicting human activities a century from

                      Although the sources of carbon dioxide and CFCS have been identified
                      better than the sources of other greenhouse gases, uncertainties still
                      remain in predicting future atmospheric concentrations. For example,
                      according to a DOE study, the principal uncertainty hampering accurate
                      estimates of atmospheric carbon dioxide levels a century from now is
                      the future rate of emissions from fossil fuel combustion.7 Some of the
                      largest uncertainties surrounding future emissions concern future eco-
                      nomic and population growth rates. Uncertainties in projected energy
                      use and choices of energy technologies are factors that make such fore-
                      casts difficult.

                      Additionally, DOEreported that estimates are hampered by unknowns
                      about the role the biosphere and oceans play in regulating carbon
                      dioxide concentration in the atmosphere. Calculations of worldwide
                      fossil fuel usage indicate that over twice as much carbon dioxide is
                      injected into the atmosphere yearly than can be accounted for by the
                      increases in atmospheric concentration that are being measured at
                      observation stations. The remaining carbon dioxide, scientists believe, is
                      being removed by the photosynthesis of green plants and by the chem-
                      ical and biological interaction of the ocean with the atmosphere. There
                      are uncertainties, however, in apportioning the amounts of carbon

                      %PA concurs that estimates of the future growth of greenhouse gas emissions are uncertain, How-
                      ever, EPA notes that projections of future emissions are being made and used by the United States
                      and other countries for planning purposes. EPA further states that these projections are reasonable
                      scenarios for the future, and using these scenarios, the United States and other countries can begin to
                      plan and determine the types of reductions that will be necessary to limit greenhouse gas emissions,

                      7M.P. Farrell (ed.), Master Index for the Carbon Dioxide Research Stateaf-the-Art Report Series,
                      DOE, Office of Energy Research (Washington, D.C.: Mar. 1987), p. 6.

                      Page 25                                                           GAO/RCEDSO-58       Global Warming
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    Greenhouse     Gases   Increasing   at
    Uncertain Rate

    dioxide being removed from the atmosphere between plants and the
    oceans, although most atmospheric scientists believe that removal by
    the ocean is substantially larger.

    Future growth in the atmospheric concentration of methane is also
    uncertain, according to a report by DOE, because of insufficient data on
    the amount of methane emitted by natural and man-made sources.* As a
    result, the ranges estimated for individual sources are large. For
    example, according t,o the DOE report, wetlands are emitting between 60
    billion and 160 billion metric tons of methane per year, and rice paddies
    are emitting between 40 billion and 100 billion metric tons per year.
    Additionally, growth rates are uncertain because enhanced global
    warming could possibly increase the release into the atmosphere of large
    quantities of methane frozen in the ice and soil in arctic and subarctic

    Uncertainties also surround scientists’ understanding of the future
    growth rates of other greenhouse gases. For example:

. Although the sources of nitrous oxide have been reasonably identified,
  the processes and conditions under which more or less nitrous oxide is
  released from the soil need to be better understood.g
l Measurement techniques for determining reliable, long-term global ozone
  trends need to be developed,‘”

    Despite uncertainties in the sources and rates of future growth, the
    Director of NOAA’S Aeronomy Laboratory predicts that within the next
    decade the greenhouse gases other than carbon dioxide, when taken
    together, will surpass carbon dioxide as the primary contributors to
    potential global warming.‘]

    8Wuebbles and Edmonds, Primer        on   Greenhouse Gases, pp. 20-25

    “P.M. Vitousek, “Perspectives on the Nitrogen Cycle,” in 1989 Global Change Institute on Trace Gases
    and the Riosphere, Office for Interdisciplinary Earth Studies, University Corporation for Atmos-
    pheric Research, draft (rloulder, Co.: Jan 1989), p. 9.
    “Wuebbles and Edmonds, Primer on Greenhouse Gases,p. 18.

    l’ln its recent scientific assessment,IPCC asserted with confidence that carbon dioxide has been
    responsible for over half the enhanced greenhouse effect in the past and is likely to contribute as
    much in the future. See “Pohcymakers Summary,” FCC, p. 1.

    Page 26                                                             GAO/RCED-90-58 Global Warming
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                            Greenhouse Gases Increasing     at
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                            Scientists have identified two areas where further work is needed to
Need for Improved           improve their understanding of greenhouse gases:
Understanding of
Processes Controlling   l
                            Better experimental and theoretical understanding of the biological,
                            chemical, and geophysical processes that control the emission and
Greenhouse Gases and        uptake of greenhouse gases.
for Better Data         l   Better observational data bases.

                            The need for a better understanding of the processes that control the
                            emission and removal of greenhouse gases was repeatedly mentioned by
                            scientists we interviewed and in published reports. For example, the
                            National Academy of Sciences identified the need to improve the under-
                            standing of primary ecosystem processes that determine the movement
                            of greenhouse gases between the land and atmosphere. DOE cited the
                            need to better understand the processes that release into and remove
                            from the atmosphere carbon dioxide and other greenhouse gases.

                            Improved observational data on the atmospheric concentration of green-
                            house gases, particularly long-term monitoring, will provide data to
                            improve scientists’ understanding of these processes. According to scien-
                            tists we spoke with, the observational data could be improved by the
                            addition of monitoring stations and more vertical measurements of the
                            gases’ atmospheric concentrations+ Current measurements are taken
                            predominantly at ground level, and measurements of the distribution of
                            greenhouse gases with altitude would improve scientists’ knowledge of
                            the sources of these gases and the processes that remove them from the
                            atmosphere. Additionally, the monitoring techniques for ozone in the
                            lower atmosphere need to be improved to determine ozone’s annual
                            growth rate (see table 2.2).

                            The research underway or planned at several federal agencies addresses
                            these needs and is expected to improve scientists’ understanding of
                            greenhouse gases. The U.S. Global Change Research Program recognizes
                            the need for more process studies and improved observational data and
                            has proposed new research or augmentations to existing research to
                            address these needs.‘* For example, the Global Ocean Flux Study-
                            undertaken jointly by LIOE, NASA, NOAA,and NSF-was expanded in fiscal

                            12The U.S. Global Change Research Program was developed by the Committee on Earth Sciencesas
                            part of the President’s fiscal year 1990 budget for research on global climate change. This program
                            sets forth a comprehensive plan for such research to be undertaken by DOE, EPA, NASA, NC&A,
                            NSF, USDA, and USGS.The program assessescurrent agency programs, identifies the highest priority
                            areas of needed research, and outlines research initiatives for fiscal year 1990 and/or augmentations
                            by federal agency. The Committee on Earth Sciences expects to update this plan yearly.

                            Page 27                                                          GAO/‘RCED-BMg       Global Wamdng
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                     Greenhouse Gases Increasing    at
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                     year 1990 to focus on processes controlling the global marine carbon
                     cycle, emphasizing the biological processes that control the movement of
                     carbon into and out of the ocean, This work is proposed to be funded at
                     $5.8 million in fiscal year 1990.

                     In addition, NOAA'S Radiatively Important Trace Species Program under-
                     takes laboratory and field studies to better understand the greenhouse
                     gases other than carbon dioxide and maintains long-term measurements
                     of these gases. There are plans to expand the program in fiscal year
                     1990 to set up monitoring stations to measure ozone concentrations in
                     the lower atmosphere and to measure over time the distribution of ozone
                     and other greenhouse gases at different altitudes.

                      Atmospheric concentrations of greenhouse gases such as carbon dioxide,
GAO’s Observations    methane, CFCS, and nitrous oxide are increasing, and some are
                      approaching or have already exceeded historic levels. However, esti-
                     mates of future atmospheric levels cannot be strongly relied upon
                      because the sources of some of these gases and the processes that affect
                     their atmospheric concentration are not adequately understood.
                     Problems with the estimates add another degree of uncertainty to pro-
                     jections of future climate change. ‘3 These estimates are discussed in
                     chapter 3.

                     The research being planned and undertaken by federal agencies is
                     intended to reduce these uncertainties and improve estimates of future
                     atmospheric levels of greenhouse gases. Improved estimates are impor-
                     tant to understand how and when greenhouse gases may affect the cli-
                     mate and to determine strategies to limit their growth. Such strategies
                     are discussed in chapter 4.

                     EPA commented, in general, that this report represents a substantial com-
Agencies’ Comments   pilation of ongoing work and achieves a well-balanced view of the
                     issues. However, EPA said that some issues presented in this chapter
                     required further elaboration. Where appropriate in the chapter, we have
                     included additional points provided by EPA on

                     13EPAemphasized, however, that there is a strong scientific consensusthat    there   will be an increase
                     in concentrations of greenhouse gases resulting in increased temperatures.

                     Page 28                                                         GAO/RCED-SO-68         Global Wamdng
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l   the use of emission scenarios by the United States and other countries
    for planning purposes despite the uncertainties in estimates of future
    growth of greenhouse gas emissions and
l   the strong scientific consensus that there will be an increase in the con-
    centration of greenhouse gases resulting in increased temperature.

    KASAapplauded our efforts to address the complex and important issues
    concerning global warming, but believed that the depth and timeliness of
    the report were handicapped in two ways. First, the executive summary
    oversimplified the diverse and complex issues that were presented in
    the body of the report. NASA urged a careful reading of the main body of
    the report to understand issues such as the distinction between defores-
    tation and fossil fuel burning as sources of carbon dioxide at different
    times in history and the uncertainties regarding the loss mechanisms for
    carbon dioxide! which are discussed in chapter 2.

    Second, NASA believed that the report was limited by having to treat a
    rapidly evolving body of scientific knowledge while being constrained to
    rely on published material. In particular, NASA referred to a draft report
    by IPCC that will be released later this year. According to NASA, this
    report will present important new findings on estimates of the atmos-
    pheric lifetime of carbon dioxide, discussed in chapter 2, as well as sev-
    eral other issues discussed in chapter 3. DOE and EPA also commented
    that information from the IPCC report should be included in this report.

    Although the IPCC report is not issued, we were able to obtain a draft of
    the executive summary. We have updated information in the text-such
    as the atmospheric lifetime of carbon dioxide-to reflect these recent

    NASA also believed that this chapter neglected other factors that affect
    the earth’s energy balance and hence climate. We agreed with this point
    and added that information to chapter 1.

    Page 29                                         GAO/RCED-9M8   Global Warming
Chapter 3

Global Warming Estimates Expected to                                                             linprove

as ResearchContinues

                        Scientists use mathematical models-general circulation models (GCM)-
                        to estimate the effect of greenhouse gases on the future global climate.
                        These models agree that the average global temperature will increase
                        over the next 100 years. There is little consensus, however, on the spe-
                        cific magnitude, timing, and regional distribution of this climate change.

                        This lack of consensus on the specifics of climate change is due to the
                        limitations of the models themselves. GCMS are rough approximations of
                        the atmosphere-ocean system and do not fully treat many important cli-
                        mate processes. The limitations affect not only the consensus among
                        models but also diminish the usefulness of their results for research on
                        the effects of climate change. The models’ limitations are expected to
                        decrease over the next 5 to 10 years if improvements are made in data,
                        computing power, and scientists’ understanding of the processes

                        Five major GCMS estimate that with the radiative equivalent of a doub-
Estimates by Climate    ling of carbon dioxide, the average global temperature will increase over
Models                  the next century.l The amount of warming estimated varies from 1.6 to
                        5.2 degrees Celsius. The models also estimate greater warming near the
                        poles, changing rainfall patterns, and rising sea levels. However, there is
                        little consensus on many aspects of temporal or regional changes.

Evaluations of Models   To evaluate how well the models estimate climate change, modelers
                        have tested their ability to reproduce some features of today’s climate
                        and past climates. According to most scientists, the models are generally
                        accurate in reproducing today’s climate and seasonal cycle on a global
                        scale. Modelers have also assessed the ability of GCMS to reproduce past
                        climates and have found that the models do well at simulating a few
                        features of ancient paleoclimates. The successful simulation of past cli-
                        mate cycles, coupled with successful simulations of general features of
                        the relatively warm present climate, indicates to researchers that the
                        models are capable of estimating a wide range of climatic conditions.

                        ‘The radiative equivalent of a doubling of carbon dioxide means that the radiative effects of other
                        greenhouse gases are included in the models by assuming that their increases are part of the carbon
                        dioxide doubling. Modelers usually instantaneously double carbon dioxide as a convenient future see-
                        nario. Most models estimate that such a doubling could occur sometime during the twenty-first cen-
                        tury. These estimates, however, are uncertain, as discussed in ch. 2. Recently, some models-
                        including those at NASA, the Geophysical Fluid Dynamics Laboratory, and the National Center for
                        Atmospheric Research-have used more realistic incremental increases in greenhouse gases to study
                        the effect of their gradual accumulation on climate.

                        Page 30                                                         GAO/RCED9@68 Global Warming
                                      Chapter 3
                                      Global Warming Estimates Expected   to
                                      Improve as Research Continues

                                      This capability provides more confidence in the results of these models
                                      when they are used to study carbon dioxide-induced climate change.

                                      In many assessments, however, the models do not perform well, such as
                                      in testing the representations of individual physical components of the
                                      models. For example, a model may estimate average cloudiness well, but
                                      represent the amount of warming produced by clouds poorly. In addi-
                                      tion, the models’ ability to represent regional climate shows results that
                                      vary not only in magnitude but even in the direction of change for many
                                      regions. These assessments expose several of the models’ limitations:
                                      They are inconsistent in estimating regional effects and representing
                                      small-scale processes, such as clouds. These and other limitations in
                                      GCMS are discussed later in this chapter.

Unprecedented                         For the radiative equivalent of a doubling of atmospheric carbon dioxide
                                      (which could occur as early as 2030), the models estimate a 1.6- to 5.2-
Temperature In.creases                degree Celsius (3- to g-degree Fahrenheit) warming, as shown in table
                                      3.1. For comparison, the warmest time during the past 100,000 years
                                      was only about 1 degree Celsius warmer than today. That is, if a doub-
                                      ling of carbon dioxide raises the temperature by even the low estimate
                                      of 1.6 degrees Celsius, the results will be beyond the range of any
                                      changes in average temperature that have existed during recent history,
                                      and the rate of temperature increase could be the most rapid the earth
                                      has ever experienced.

Table 3.1: Average Global Warming
Estimated by GCMs for a Doubling of                                                            Estimated warming by
Carbon Dioxide                        Research institution                                    GCM (degrees Celsius)
                                      United Kingdom Meteorologica Office                                           5.2
                                      Goddard lnstrtute for Space Studies                                           4.2
                                      Geophywal Fluid Dynamics Laboratory                                           4.0
                                      Oregon State University                                                       2.8
                                      Natlonal Center for Atmospheric Research                                      1.6

                                      Although these models point to substantial warming by the middle of
                                      the next century, the interim increases in temperature are uncertain.
                                      Researchers at Goddard Institute for Space Studies (GISS) have shown
                                      that their model indicated a tendency toward warming in the 198Os, but
                                      that in most regions the warming shown by the model was less than the
                                      natural variability. This variability-weather     fluctuations from year to
                                      year-provides      some cool years despite the slight overall warming trend
                                      and makes the detection of global warming difficult over the span of a

                                      Page 3 1                                        GAO/RCED-9@68   Global   Warming
                            chapter 3
                            Global Warming EMmates Expected         t.a
                            Improve aa Research Continues

                            few years. In the 199Os, according to the GISS model, the warming will be
                            comparable to the variability of many regions, and by the 2OlOs, the
                            entire globe will experience noticeable warming. Thus, although the
                            effects of greenhouse warming have not been large enough to date to
                            distinguish from natural variation, some scientists believe that the
                            warming could soon become detectable by scientists and more noticeable
                            to the average personS

Other Features of Climate   Modelers are less certain about the timing, magnitude, specific features,
                            and effects of the warming than they are about the estimate that
Change Estimated by         warming will occur. The Director of the Geophysical Fluid Dynamics
Models                      Laboratory (GFDL) provided his estimates of the probability of certain
                            climate changes, derived from the GF’DL model and observational anal-
                            yses. The results shown in table 3.2 suggest that changes such as
                            increasing arctic warming and increasing global precipitation are very
                            probable in a world where the amount, of carbon dioxide has doubled. As
                            the earth warms, sea ice and snow cover in the arctic region may melt,
                            thereby reducing surface reflectivity and allowing still more absorption
                            of solar radiation, which would further warm this region. Global
                            average precipitation is also expected to increase as evaporation

                            %ee J. Hansen, et al., “Prediction of Near-Term Climate Evolution: What Can We Tell De&ion-
                            Makers Now?” in Preparing for Climate Change, Proceedings of the First North American Conference
                            on Preparing for Climate Change (Washington, D.C.: Government Institutes, Inc., Oct. 27-29, 1987),
                            pp. 36-47. Other scientists caution that there is room for doubting such predictions.

                            3Researchers at GISS have found that greenhouse warming may increase the frequency of conditions
                            of extreme moisture as well as extreme drought. They report that the impact of global warming on
                            droughts and storms provides no evidence that there will be regional “winners” if greenhouse gases
                            continue to increase rapidly. This finding has not been substantiated by other models and, therefore,
                            is controversial

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Table 3.2: GFDL Estimates   of Climate
Change                                   Expected effect                                                                  Confidence0
                                         Global average surface warming                                                   Very probable
                                         Global averaae orecioitation increase                                            Verv orobable
                                         Arctic winter surface warmina                                                    Verv orobable
                                         Reduction of sea ice --.”     _.~.~- -                                           Very probable
                                         Northern high latitude -..--.--.--
                                                                 precipita:,on increase                                   Probable
                                         Summercontinental dryness/warming                                                Probable
                                         Rise in global mean sea level                                                    Probable
                                         Realonat veaetatron chanaes                                                      Unceriain
                                         Tropical storm Increases                                                         Uncertain
                                         Details of next 25 years                                                         Uncertain
                                         a”Very probable,” effect has more than a go-percent chance of occurring: “probable,”  effect has more
                                         than about a 67.percent chance of occurring; “uncertain,” effect has been hypothesized but evidence
                                         for its occurrence is Inadequate.
                                         Source: Testimony by Dr Jerry Mahlman, Director, GFDL. before the House CommIttee on Appropria-
                                         hens, Subcommittee on Foreign Operattons, Export Financing and Related Programs, Feb. 21, 1989

GCMs Lack Agreement on                   Although GCMS agree on some global average variables, the effects of
                                         increased amounts of greenhouse gases are less clear on a regional level.
Regional Estimates                       All models show an increase in global average temperature, but the
                                         regional temperature changes estimated often differ substantially in
                                         magnitude. For example, the GISS, GFDL, and Oregon State University
                                         (0s~) models all estimate an average warming over the United States.
                                         However, the annual average increase in temperature ranges from 3
                                         degrees Celsius for osu, to 4.3 degrees Celsius for GISS, to 5.1 degrees
                                         CekiUS for GFDL.

                                         The models also disagree on regional precipitation, as shown in figure
                                         3.1. Although all three models estimate that the average annual precipi-
                                         tation in the United States will increase, their estimates of regional and
                                         seasonal distribution varied greatly. For example, one version of the
                                         GFDL model estimated that summers in the southeastern United States
                                         would be drier than normal, whereas a GISS model estimated that condi-
                                         tions would be wetter. This lack of agreement on regional impacts limits
                                         the models’ usefulness for studying local climate changes.4

                                         4Agreement on regional effects, however, would not ensure accuracy. Independent measures are
                                         needed to verify the models’ estimates.

                                         Page 33                                                           GAO,‘RCED-90-58    Global Warming
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Figure 3.1: Precipitation Estimates   for
the Southeastern United States              0.7    Change In Millimeters   par Day

                                            -. 6

                                                   Wllller                 Summer           Annwl

                                                   n         GISS

                                            Source: Smith and Tirpak, Potential Effects of Global Climate Change In the United States, p 6-l 1

                                            According to scientists we spoke with, several limitations in the models
Models’ Limitations                         affect the accuracy of their estimates and are responsible for the lack of
                                            agreement among models. Because no model contains sufficient detail to
                                            simulate the atmosphere’s full complexity, results are approximate and
                                            vary from model to model. CXMS do not perform calculations for every
                                            part of the earth’s surface or atmosphere because the amount of data
                                            and computer capacity required would be prohibitive. Instead, calcula-
                                            tions are solved at widely spaced grids, which preclude many important
                                            small-scale climate phenomena from being included. In addition, the
                                            models do not fully treat a number of feedback processes that could
                                            intensify or lessen global warming, such as changes in cloud cover. Simi-
                                            larly, ocean processes may alter climate change, but are omitted by
                                            many of the GCMS’ simplified representations.

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Grids Are Widely Spaced                   According to scientists we met with, a primary limitation of GCMs is their
                                          use of widely spaced grids. GCMSgive outputs in grid boxes that vary in
Within the GCMs                           size from 4 degrees by 5 degrees to as much as 8 degrees by 10 degrees.
                                          Figure 3.2 shows 4-degree by 5-degree grid boxes from a GCM overlaid on
                                          a map of the United States. The grid boxes are about as large in scale as
                                          Colorado. Within each box, the actual climate may vary considerably.
                                          For example, the weather in western Nevada may be quite different
                                          from San Francisco, but both are in the same grid box, as seen in the
                                          shaded area. GCMSdo not account for variations within each grid box,
                                          but instead estimate average climate conditions for the entire box. Thus,
                                          GCMS provide a single value for temperature, rainfall, and other vari-
                                          ables for the entire grid box.

Figure 3.2: GCM Grids (Measuring 4 by 5
Degrees) Over the United States


                                          Low resolution affects not only the precision of the output but also its
                                          usefulness. Since the output is a set of variables for an area about 300
                                          miles by 300 miles, these data cannot be used to analyze smaller regions
                                          unless additional methods are applied. Low resolution also limits the
                                          ability of planners to use data from the GCMSin developing adaptation
                                          strategies. The primary obstacle to obtaining regional resolution is com-
                                          puting power. For example, 60-mile grid spacing would take 500 times
                                          the current computing power.

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Models Describe Natural    According to the scientists we spoke with, a second fundamental
                           problem in developing climate models has been the accurate representa-
Processesin a Simplified   tion of key processes, known as parameterization. Because important
Manner                     variables, such as clouds, do not occur on scales as large as a GCM grid,
                           scientists approximate their effects. Climate models include a number of
                           parameterizations, such as the role of clouds for water and energy
                           transfer in the atmosphere. Scientists are still learning how to incorpo-
                           rate processes on small spatial and temporal scales into the large-scale
                           models. As yet, they have not resolved how small-scale processes
                           interact with large-scale processes; consequently, the influence of the
                           regional features on the global system is uncertain.

Models Poorly Represent    Introducing greenhouse gases into the atmosphere causes the earth’s
                           system to seek a new equilibrium climate in several ways. Often called
or Omit Important          climate feedbacks, these responses include changes in water vapor, ice
Processes                  cover, clouds, vegetation, and the oceans, The net effect of these feed-
                           backs, some amplifying warming and some cooling, determines the new
                           equilibrium climate reached after an increase in greenhouse gases.
                           According to the scientists we spoke with, some feedbacks are incorpo-
                           rated well in the models, some are poorly represented, and others are
                           omitted. For example, one researcher has pointed out that the models
                           ignore some mitigating or cooling factors, such as sulfur dioxide emis-
                           sions from coal-burning power plants. Sulfur dioxide could cause clouds
                           to brighten and reflect incoming solar radiation away from the earth.5
                           Until these feedbacks are understood and incorporated into the models,
                           estimating global temperature increases accurately is difficult.

                           Clouds are the most uncertain feedback in the climate models, according
                           to climate modelers, yet they have the potential to amplify or diminish
                           the warming significantly.” All clouds act, to some extent, as “reflecting
                           blankets,” simultaneously cooling the earth by reflecting incoming sun-
                           light back into space and warming the earth by preventing the earth’s
                           heat from escaping. In general, however, low cloud coverage or depth
                           produces a net cooling effect, while high clouds have more of a warming
                           effect. According to scientists at GISS, some models show an increase in
                           high clouds with doubled carbon dioxide and thus estimate more
                           warming. However, clouds are often handled simply by GCMS. For

                           5As another example of limitations in GCMs, EPA noted that they do not include the possible effects
                           of biogenic feedbacks.
                           “D. Lashof The Dynamic Greenhouse: Feedback ProcessesThat May Influence Future Concentrations
                           of Atmospheric Trace Gases and Climatic Change, EPA (Washington, DC.: Jan. 4, 1989), p. 7.

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                        example, in the GFDL model, if 90 percent or more humidity is estimated
                        in a grid box, it has cloud coverage. Thus, there are large uncertainties
                        about how clouds will really behave, and the different modeling groups
                        that we spoke with put little confidence in their models’ ability to
                        account for cloud feedback.

Exclusion of the Deep   Ocean processes can affect climate change from increases in greenhouse
                        gases in several ways. For example, the ocean’s absorption of carbon
Ocean                   dioxide would lower the amount retained in the atmosphere and, thus,
                        lessen the extent of greenhouse warming. In addition, possible changes
                        in ocean currents would alter the global distribution of heat. Until
                        recently, atmospheric GCMS included only simplified representations of
                        oceans in which oceans were assumed to have no currents, to instanta-
                        neously mix with the upper ocean, and to do little more than absorb and
                        conduct heat. Modelers are now attempting to join an independent ocean
                        circulation model with one for the atmosphere. In recent years, more
                        complex representations of the oceans have been developed by GFDL, the
                        National Center for Atmospheric Research (NCAR), and osu. A recent
                        NCAR model, for example, considers ocean circulation and estimates a
                        global warming of only 1.6 degrees Celsius from a doubling of green-
                        house gases.

                        According to scientists at GFDL, GISS, and NCAR, fully coupled ocean-
                        atmosphere models would take into account heat transport and other
                        interactions throughout the ocean, rather than just at the surface.
                        Including these interactions is important because the ocean’s huge heat-
                        absorption capacity could potentially slow the effect of atmospheric
                        warming. A coupled ocean-atmosphere model run by osu in 1984 esti-
                        mated that there would be a lag of 50 years or more before the tempera-
                        ture increase from greenhouse gases was realized.7 In addition, scientists
                        at GFDL estimated that there would be a lag in the warming at the South
                        Pole because of effects calculated by their model’s deep ocean compo-
                        nent. Specifically, because of the upwelling of cold, deep ocean water,
                        the surface waters around Antarctica would fail to warm for several
                        hundred years, keeping the sea surface temperature at Antarctica cooler
                        than estimated by previous models.

                        7J. Norris, “To Predict Pace and Extent of Global Change Better Computer Models Are Needed,” -NSF
                        News (Feb. 1989), p. 6.

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                      The limitations in GCMShave hindered scientists’ ability to use the
Implications of the   models’ estimates for research on the effects of global warming. The
Models’ Limitations   models’ coarse resolution hinders researchers’ ability to study regional
                      effects, and the crude parameterization of key climate processes limits
                      the precision of the warming estimates. Improved estimates are needed
                      to help policymakers at the federal, state, and local levels develop better
                      strategies for adapting to climate change.

                      One of the most certain effects of global warming is a rise in sea level,
                      but a reliable, accurate estimate of the possible rate of potential increase
                      is not available. Currently, the best estimate of the rise in sea level by
                      the year 2050 is about 30 centimeters, but the uncertainties surrounding
                      this estimate allow the possibility of a rise of as much as 70 centimeters,
                      or perhaps none at alLa Global warming contributes to this rise in sea
                      level in three primary ways- thermal expansion of the oceans, melting
                      of mountain glaciers, and melting or sliding of ice sheets into the oceans.
                      Estimates of potential thermal expansion are only as good as the esti-
                      mates for ocean circulation and the potential average surface warming
                      of the earth, and are. therefore, affected by the models’ limitations. In
                      addition, because ocean currents and ice sheets are not incorporated
                      well in the models, the melting threshold of these sheets is relatively
                      unknown, Finally, without regional representation of warming trends, it
                      is difficult to estimate how much mountain glacier or ice melting will

                      The extent of the rise in sea level is also uncertain because there is con-
                      siderable uncertainty about when to expect the increased warming and
                      the rate at which the warming will occur. Analysis of the rise in sea
                      level needs to include the timing of the warming because that will affect
                      how much the oceans expand and whether ice sheets and glaciers break
                      up. However, the precise timing of climate change is still unknown
                      because of uncertainties surrounding future releases of greenhouse
                      gases and the limitations of the climate models.

                      Federal, state, and local officials need accurate estimates of the rise in
                      sea level and of its timing to evaluate individual projects in coastal
                      zones. Parties that could be affected by a rise in sea level need to deter-
                      mine whether the impacts will require changes in their operations and
                      how much these changes will cost. EPA estimates that it may cost
                      between $73 billion and $111 billion (cumulative capital costs in 1985

                      ‘M.F. Meier, “Reduced Rise in Sea Level,” Nature, vol. 343 (-Jan. 1I, 1990), pp.115.116.

                      Page 38                                                        GAO,‘RCED-!#0-68   Global Warmiug
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                  dollars) to protect developed coastal areas in the United States against
                  inundation and erosion from a 1-meter rise in sea level.

                  For example, it was reported that Charleston, South Carolina, is
                  designing a new storm drainage system that will cost about $4.8 million,
                  and what the capacity of the system should be depends in part on what
                  the rise in sea level will be.g For an additional $270,000, larger pipes
                  could be installed to accommodate the 30-centimeter rise in sea level
                  expected by 2025. Without the larger storm runoff system, and
                  assuming the 30-centimeter increase, the system would require a $2.4-
                  million retrofit, The city has to decide whether to invest in a larger
                  storm runoff system in anticipation of a future rise in sea level, or to
                  choose the less expensive system that would meet its needs if there is no
                  significant rise.

                  On the federal level, several agencies need estimates of the rise in sea
                  level to effectively implement their programs. The Army Corps of Engi-
                  neers will need to consider the rise in sea level before developing future
                  coastal projects, such as beach restoration, which costs millions of dol-
                  lars. In addition, the Federal Emergency Management Agency (FEMA)
                  provides federal flood insurance to coastal properties worth billions of
                  dollars. FEMA needs to anticipate the rise in sea level in order to adjust
                  its policies and insurance rates

                  Until GCMS are improved, the models’ results will be useful only as “sce-
                  nario” climate variables-numbers    used to build possible scenarios of
                  future climate, upon which impact analyses can be based. Improved esti-
                  mates from GCMS are needed to aid policymakers in developing effective
                  adaptation strategies for climate change.

                  The limitations in WMs-coarse resolution and exclusion of key climate
Requirements to   processes-are expected to decrease over the next 5 to 10 years,
Improve GCMs      according to scientists we spoke with. The rate of improvement depends
                  on additional research to better understand climate change, increased
                  computer capacity, and additional observational data. The scientists we
                  spoke with generally agree that improvements in the models are likely
                  and estimates should improve with time.

                  ‘J.G. Titus, “Greenhouse Effect, sea Level Rise, and Coastal Zone Management,” Coastal Zone Mar-
                  agement Journal, vol. 14 (1986), pp. 163-164.

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ResearchNeeds        To improve their understanding of climate change, according to scien-
                     tists, science will need to advance in many research areas, such as cli-
                     mate modeling, biological modeling, atmospheric chemistry, and
                     oceanography. Furthermore, additional scientists will be needed to
                     ensure that research in these areas advances.

                     Graduate students need to be attracted to climate change research to
                     ensure that an adequate number of scientists will be working on the
                     problem in the coming decades, according to the Director of GISS. He
                     emphasized that a variety of specialists-including   field observation
                     gatherers, modelers of hydrologic cycles, and atmospheric scientists-
                     are needed to gain a better understanding of these issues.

Observational Data   Most scientists we spoke with emphasized the need for extensive, long-
                     term observational programs to provide data on climate systems. These
                     climate data are needed to improve the climate processes included in the
                     models and to evaluate the results of the models by comparing them to
                     the current climate. For instance, better ocean models require more mea-
                     surements of ocean processes, and improved forecasts of regional vege-
                     tation require better data on its distribution and changes. Both satellite
                     and ground-based data on climate change need to be gathered for
                     decades to gain a continuous record. Climate processes represented in
                     GCMS cannot be evaluated without observational data and studies of
                     these processes in the present climate.

                     For example, many modelers have been working on improving the repre-
                     sentation of clouds in GcMs, one of the weakest components of the
                     models. To evaluate their estimates of cloud behavior, modelers need to
                     compare their modeled clouds with observations of clouds in the present
                     climate. A recent observational program, funded by NASA and NOAA, the
                     Earth Radiation Budget Experiment (ERBE), has been collecting satellite
                     data on the radiative balance of the earth.‘* Until ERBE, observations
                     around the globe were insufficient to determine whether clouds cooled
                     or warmed the earth. Data obtained from the ERBE program have given
                     scientists a basis to begin improving their modeled clouds.

                     loThe radiative balance of the earth is the balance between radiation gained from the sun and radia-
                     tion lost through re-radiation from the earth. The balance between radiation lost and gained depends
                     upon the concentration of greenhouse gases in the atmosphere.

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                      Similarly, NASA has studied the feasibility of implementing a satellite
                      program for measuring tropical rainfall-the     Tropical Rainfall Mea-
                      suring Mission (TRMM). Atmospheric circulation is in large part deter-
                      mined by the energy released by precipitation; consequently, an
                      accurate measurement of global precipitation is essential for under-
                      standing how the global climate system operates. The amount of precipi-
                      tation falling on the earth at many specific locations may be 2 or 3 times
                      more or less than current estimates, according to NASA scientists. TRMM
                      would help fill that informational gap and increase scientists’ under-
                      standing of precipitation patterns and of how to simulate them in cli-
                      mate models and how to estimate changes in precipitation in response to
                      other climate changes. The planned TRMM project will be undertaken
                     jointly by the United States and Japan, costing each nation about $150

Computer Resources   The development of models and improvements in regional estimates of
                     climate change are also affected by computing power. The largest
                     supercomputers available are saturated by today’s GCMS, despite their
                     vast simplifications. Some improvements in models, such as increased
                     resolution and ocean-atmosphere coupling, cannot be made without
                     increased computing power.

                     Scientists are hampered in their attempt to improve the models’ resolu-
                     tion because smaller-scale models require more computing time and
                     capacity and, thus, are becoming more expensive. To reduce grid sizes
                     by half would require 8 times the number of calculations on a supercom-
                     puter and 16 times the number of calculations if vertical resolution were
                     made correspondingly finer.

                     In addition, running completely coupled atmospheric and oceanic models
                     for a sufficient number of simulated years to adequately describe cli-
                     mate change is not yet possible, in part because there is no computer
                     powerful enough to deal with the necessary data. Some researchers
                     believe that massively parallel supercomputers are needed to improve
                     the models’ estimates.

                     Two modeling groups we met with, GFDL and NCAR, are planning to obtain
                     more current supercomputers for modeling. Expected benefits from
                     their updated computers include improved resolution in GCMS, more real-
                     istic atmosphere-ocean climate models, better treatment of clouds and

                     ’ ‘According to MSA, this project is in the planning stage. A start-up date has not been determined.

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                     chemistry, better assessments of regional climate change, and better
                     explanation of observational trends. Nonetheless, the modelers at GFDL
                     expect to saturate the new supercomputers quickly, and significant com-
                     putational compromises will still be necessary to run GCMS. The Director
                     of GFDL explained that although an increase in computing power will
                     give modelers the opportunity to research new pieces of the climate
                     change problem, the climate system’s overall complexity is greater than
                     could be handled by any supercomputer currently being planned.

                     Although estimates from GCMS are now limited by computer resources,
GAO’s Observations   data, and scientists’ understanding of climate processes, these estimates
                     indicate that greenhouse gases will increase the average global tempera-
                     ture over the next. century. The extent, magnitude, and timing of these
                     changes are uncertain! but are the subject of current and planned
                     research. With better estimates, policymakers and scientists will be able
                     to improve their understanding of the impact of climate change on
                     diverse areas, including agricultural productivity, water resources,
                     human health, and the environment. Such information will assist policy-
                     makers in developing strategies to prepare for, prevent, or limit the
                     effects that are likely to occur with climate change.

                     EPA noted several limitations in this chapter. First, EPA noted that the
Agencies’ Comments   report surveys what is known about the physical climate but not what is
                     known about the response of living organisms to climate change. EPA
                     pointed out that as the earth’s temperature warms, biogenic feedbacks
                     can be triggered that may affect the warming. For example, as global
                     temperatures increase, tundra areas could melt, releasing trapped
                     methane, which in turn would enhance the greenhouse effect. In addi-
                     tion, EPA noted that information on the response of ecosystems to cli-
                     mate change will be valuable in developing strategies for adapting to
                     environmental changes induced by a changing climate.

                     We agree with EPA on the importance of understanding the effect of cli-
                     mat.e change not only on ecosystems but also on other important areas,
                     such as agriculture, water resources, and human health. But before
                     addressing these issues, we believed it was important to examine first
                     the causes of the greenhouse effect and estimates of climate change,
                     which we focused on in this initial effort

                     NASA noted that some information presented in this chapter is oversim-
                     plified in the executive summary, specifically the meaning of the use of

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an “equivalent” doubling of carbon dioxide by modelers. In addition,
NASA said that we omitted discussing that global ocean circulation
models are more poorly developed than atmospheric circulation models.
We agree with NASA that this is an important issue. We mentioned ocean
circulation models in our discussion of the limitations of GCMS. Our pur-
pose, however, was to examine atmospheric GCMS, not ocean models.

NOAA commented that this report represents a summary of recent, but
not current, findings of individual groups rather than a true scientific
consensus on global warmingal Further, NOAAnoted that a forthcoming
IPCC assessment will provide a more up-to-date evaluation of global
change than this report. In particular, NOAA noted that our temperature
ranges (5 to 8 degrees Fahrenheit) for global warming were higher than
the current best estimates (3 to 8 degrees Fahrenheit). Similarly, DOE
noted that the estimates we reported could include the results of more
recent studies. To reflect these more recent estimates, we have included
information from IPCC'S executive summary where appropriate. Further-
more, we added estimates from a model by the United Kingdom Meteor-
ological Office and more recent model results from ICAR's model, thereby
expanding the temperature range cited to 3 to 9 degrees Fahrenheit.

NOAAfurther stated that the report assumes that effects of global
warming will occur and that they will be negative, even though there is
uncertainty in many areas. NOAAalso asserted that new findings suggest
that future changes may not be as severe as indicated. DOEalso com-
mented that the report should discuss the potential for beneficial
impacts of climate change. This report examines only one potential
impact-a rise in sea level-as an example of the implications of limita-
tions in GCMS. We used this example because experts told us that it was
one of the most certain effects. We carefully pointed out that estimates
of a rise in sea level are uncertain. We have modified our reported esti-
mate of the extent of the expected rise in sea 1eveI to about 30 centime-
ters to reflect more recent findings.

DOE stated that the executive summary’s discussion of chapter 3 would
be strengthened if estimates of the effects of greenhouse gases on past
and current climates were added. We did not include such information in
this chapter or the executive summary’s discussion of this chapter
because we discuss it in chapter 2.

12Wewere surprisedby this comment, since previous comments from NOAA scientists we interviewed
described the report as well written and thoughtful, and as doing a good job of capturing the main-
stream of scientific thought.

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Chapter 4

Policy Fhmework to Address Global
Climate Change

                        Depending on its extent, magnitude, and timing, global warming could
                        have a profound effect on many aspects of everyday life. While many of
                        global warming’s possible consequences may not manifest themselves
                        until well into the next century, policymakers are faced with examining
                        how best to respond now as well as in the long term,

                        Policymakers face several challenges in preparing for global warming.
                        First, their responses need to take into consideration the global scope of
                        the problem: All nations emit greenhouse gases, and all will experience
                        the impacts. Second, the scientific uncertainties make it difficult to
                        ascertain the correct response because the climate may change more or
                        less than anticipated and may even change in unanticipated ways. Fur-
                        thermore, the regional effects are projected to be uneven. Third, and
                        perhaps more importantly, policymakers must weigh the risk of more
                        adverse impacts by delaying action while they wait for additional scien-
                        tific information against prematurely taking costly actions that may
                        prove unwarranted.

                        Nonetheless, we found that some environmental and industrial organiza-
                        tions support taking actions now to reduce greenhouse gas emissions
                        rather than waiting until the earth is committed to potentially harmful
                        warming. They reason that actions now will have benefits in addition to
                        reducing greenhouse gases, Reductions of some greenhouse gases, such
                        as CFCS, are in fact already underway.

                        Global warming and its potential impacts on society and the environ-
Nature of the Problem   ment are international problems whose exact nature is unknown
                        because of the scientific uncertainties discussed in chapters 2 and 3.
                        Since greenhouse gases have already been released, we may be com-
                        mitted to a l- or 2-degree Celsius increase in the average global tempera-
                        ture. Concern about accelerated global climate change has focused
                        national and international attention on the potential for reducing emis-
                        sions from man-made sources and adapting to the possible impacts of
                        global climate change.

                        Any comprehensive, long-term solution will require the cooperation of
                        many countries and reductions in many sources. All countries contribute
                        to greenhouse gas emissions and share some responsibility for their con-
                        tinued growth. As shown in figure 4.1, the United States and Western
                        Europe account for about 35 percent of the greenhouse gas emissions.
                        Since the early 197Os, however, their emissions have generally remained
                        stable, while the emissions of developing countries have steadily

                        Page 44                                        GAO/BCED-!MM8   Global Warming
                                            Chapter 4
                                            Policy Framework    to Address Global
                                            Climate Change

                                            increased. Because the United States is a major contributor of green-
                                            house gas emissions, some believe it should be a leader in developing
                                            responses to the problem, including assisting developing countries in
                                            limiting their contributions to greenhouse gas emissions.

Figure 4.1: Regional Contributions to the
Greenhouse Effect During the 1980s
                                                                                                     Rest of World

                                                                                                     United States

                                                                                           -         European Economic Cdmmunity




                                            Source    Policy OptIons far Stabdlzing Global Climate,” EPA, briefing paper (March 1989), p. 5.

                                            Industrial and agricultural activities by these nations are responsible for
                                            the increases in greenhouse gases. As shown in figure 4.2, these activi-
                                            ties include energy production and use, industrial activities (including
                                            the use of CFCS), agricultural practices, and changes in land use
                                            (including deforestation).

                                            Page 45                                                             GAO/RCED9068        Global Warming
                                             Chapter 4
                                             Policy Pramework    to Address Global
                                             Climate Change

Figure 4.2: Activities   Contributing   to
Global Warming

                                                                   1                                 2kr     Industrial Activities

                                                                                                      Energy Use and Production

                                                         1                                           CFCs

                                             Source: Lashof and Tlrpak, Pohcy Options for Stabilizing Global Climate, p. 55.

International Panel on                       To develop an international response to t;he threat of global warming,
                                             the United States and over 35 other nations and international organiza-
Global Warming                               tions are participating in IPCC.The panel was established in 1988 by the
Established                                  World Meteorological Organization and the United Nations Environment
                                             Programme. The panel’s goals are to (1) review and assess the science
                                             relevant to climate change, (2) assess the possible environmental and
                                             socioeconomic impacts of climate change, and (3) identify potential
                                             response strategies. To address these goals, the panel established three
                                             working groups in 1988. The United States chairs the working group
                                             addressing response strategies and has representatives in the two other
                                             working groups. These working groups were scheduled to complete their
                                             work and report their results in June 1990. IPCC had plans to complete
                                             its overall report by late August or early September 1990.

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Legislation Proposed to   The threat of global warming has become the subject of policy debate in
                          the United States. The 1Olst Congress has introduced over 20 bills on
Address Global Warming    global warming. These bills generally propose measures to reduce green-
                          house gas emissions and/or studies to examine responses to the effects
                          of global warming. Several bills define federal agencies’ responsibilities
                          for dealing with these issues. In addition, the Congress passed the Global
                          Climate Protection Act of 1987, which, among other things, requires
                          that the President, through EPA, develop and propose to the Congress a
                          coordinated national policy on global climate change. The Congress fur-
                          ther requested that EPA report on the potential effects of global climate
                          change and on policies to reduce the emission of greenhouse gases.’ In
                          addition, the 1Olst Congress is considering the reauthorization of the
                          Clean Air Act, which could have implications for reducing greenhouse
                          gas emissions, particularly CFCS.

                          The scientific uncertainties surrounding possible global warming make it
Actions to Respond to     difficult for policymakers to determine the correct responses to it,
Global Warming            Potential strategies for responding to climate change fall into two cate-
                          gories. Adaptation strategies adjust the environment or our ways of
                          using it to reduce the consequences of a changing climate. Limitation
                          strategies control or stop the growth of greenhouse gas concentrations
                          in the atmosphere and limit climate change. These two responses are
                          complementary, not mutually exclusive. Because past and current emis-
                          sions probably make a warming of several degrees Celsius unavoidable,
                          some adaptation will be necessary. On the other hand, slowing the rate
                          of global warming would make it easier for society to adapt. WhiIe limi-
                          tation strategies require worldwide cooperation, adapting to the conse-
                          quences of global warming do not.

                          Although control or abatement of greenhouse gas emissions is the most
                          certain way of minimizing or avoiding climate change, it seems unlikely
                          that this will happen before some greenhouse warming occurs. Several
                          areas may be particularly affected by climate change. For example,
                          increased temperatures and changes in precipitation could result in
                          rising sea levels, which might erode or inundate coastal areas; dieback
                          of forests; changes in agricultural productivity; scarcity of water
                          resources; increased energy demand; further air pollution; and health

                          ‘Smith and Tirpak, Potential Effects of Global Climate Change on the United States, and Lashof and
                          Tirpak, Policy Options for Stabilizing Global Climate.

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Adaptive Strategies     A wide range of adaptive responses to global warming can be pursued:
                        avoiding development in unprotected coastal areas, developing more
                        heat-resistant strains of crops, planting heat- and drought-resistant
                        trees, using water resources more efficiently, and establishing corridors
                        for plant and wildlife migration. Because localities will differ in how
                        they are affected by climate changes, adaptive measures can be pursued
                        at the local, state, and national levels. Private citizens and companies
                        can relocate or modify their operations. Communities and states can
                        undertake public works or enact planning measures. National govern-
                        ments can support all of these activities. Above all, adaptive measures
                        will require flexibility in program management to respond to unforeseen
                        climate changes.

Limitation Strategies   Regardless of the scientific uncertainties, measures to limit current
                        greenhouse gas emissions would decrease the magnitude and the speed
                        of global warming. In developing priorities on limiting emissions of
                        greenhouse gases, policymakers need to consider the relative importance
                        of the gases and the practicability of controlling them. As discussed in
                        chapter 2, carbon dioxide is responsible for about half of the potential
                        for increase in atmospheric temperature. As a result, current discussions
                        at the national and the international level generally center on how to
                        control carbon dioxide. Methods being discussed include increased
                        energy efficiency, which is considered by many groups we spoke with to
                        be the most practical solution; increased use of renewable energy
                        sources; limited deforestation; and increased use of nuclear energy,
                        which is considered a solution more viable in the distant future than in
                        the near future.

Energy Efficiency       An effective strategy to slow global warming will involve moving away
                        from reliance on fossil fuels, which currently provide over 75 percent of
                        the world’s energy. This adjustment can be achieved by using energy
                        more efficiently, which reduces the amount of fuels that must be
                        burned, or by replacing fossil fuels with alternative energy sources, such
                        as solar or nuclear power.

                        According to Worldwatch Institute, improved energy efficiency has the
                        immediate potential to cut fossil fuel use at a rate of at least 2 percent
                        annually in industrial countries, with a commensurate reduction in
                        carbon dioxide emissions. Energy-efficient actions include improving the
                        efficiency of devices that use electricity-such   as appliances, lighting

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devices, and buildings-            and improving energy efficiency in the trans-
portation sector.2

Currently, 64 percent of the world’s electricity is produced by using
fossil fuels (chiefly coal), accounting for 27 percent of global carbon
emissions from fossil fuels (1.5 billion tons annually). Many uses of elec-
tricity can become more efficient. For example, with current technolo-
gies, electric motors can be made at least 40 percent more efficient, and
refrigerators 75 percent more efficient.

The potential of energy efficiency to reduce greenhouse gas emissions is
also evident in transportation. Transportation emissions worldwide add
more than 700 million tons of carbon to the atmosphere annually.
Increasing the fuel efficiency of cars would lower carbon emissions. For
example, one report estimates that doubling the fuel efficiency of a typ-
ical car to 50 miles per gallon could reduce its carbon emissions by half,
while lowering the annual gasoline fuel bill by almost $400.3

The United States realized gains in energy efficiency during the 1970s
and 1980s (see fig. 4.3) without drastic or abrupt changes in lifestyle.
Some environmental groups believe that the United States can achieve
even greater efficiency gains. Compared with cJapan, for example, the
United States consumed roughly 60 percent more energy per dollar of
national income.4

% Flavin “Slowing Global Warming: A Worldwide Strategy” (Washington, D.C., Worldwatch Insti-
tute, Oct. i989), p. 34.

%. Flavin and A. Duming, “Building on Success The Age of Energy Efficiency” (Washington, DC.:
Worldwatch Institute, Mar, 19&Q%),
                                 p. 56.

4According to the International Energy Agency, in 1987 the United States’ energy use was 0.31 (total
final consumption in tons of oil equivalent per thousand dollars of gross domestic product) compared
with Japan’s use of 0.19. International Energy Agency, “Energy Policies and Programmes of IRA
Countries: 1988 Review,” (Paris: 1989).

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 Figure 4.3: Gains in Energy Efficiency    in the United States From 1973 to 1989
28   Erwgy   Cmaumod   per Dollar   GNP’


                                                 aEnergy consumed IS measured In thousand British thermal units Gross national product (GNP) is mea-
                                                 sured In 1982 constant dollars.
                                                 Source, DOE, Monthly Energy Review (May 1989), p 18.

                                                 However, several obstacles stand in the way of increasing energy effi-
                                                 ciency, according to some of the groups we interviewed. These obstacles
                                                 include the relatively low cost of some fossil fuel energy, such as gaso-
                                                 line, in the United States, compared with costs in other countries;
                                                 choices by energy consumers that focus on short-term costs; and rela-
                                                 tively low levels of federal funding for research and development,

                                                 According to some environmental groups, the price of energy does not
                                                 reflect its true social cost. They note that energy prices do not reflect
                                                 the cost to society associated with polluting emissions from fossil fuels.
                                                 These groups favor taxes on fossil fuels to bring prices closer to the
                                                 social cost. Additionally, they point out that the United States’ gasoline
                                                 prices are considerably lower than those in the rest of the industrialized

                                                 Advocates of energy conservation also point to the choices made by
                                                 energy consumers that do not take into consideration total long-term
                                                 costs. For example, consumers may buy less energy-efficient appliances
                                                 because their purchase prices are lower, even when the life-cycle costs

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                           of higher-priced, energy-efficient appliances are lower.5 Consumers may
                           have insufficient information on technological advances and may put
                           economic considerations first in making choices about energy efficiency.

                           Similarly, businesses may fail to invest in energy conservation projects
                           with relatively high financial returns in the long term. This failure to
                           invest may be caused by policies and institutions that encourage energy
                           demand. For example, utilities have been regulated in a way that makes
                           demand growth attractive for investors and, hence, makes sales attrac-
                           tive to utility managers and investors.

                           These obstacIes may be addressed by a variety of programs to promote
                           conservation. For example, electric utility companies have promoted
                           programs to increase consumers’ efficient use of energy, such as
                           offering rebates for using energy-efficient appliances, developing home
                           weatherization programs, and disseminating information to consumers
                           on energy-efficient choices.

                           Finally, the steady decrease during the 1980s in federal funds for
                           research and development of energy-efficient technologies may be
                           another obstacle to improved energy efficiency. DOE’s funding for energy
                           conservation research and development dropped from $325 million in
                           1979 to $129 million in 1988.”

Renewable Energy Sources   Replacing fossil fuels with increased use of renewable energy sources-
                           such as solar cells (photovoltaics), solar thermal energy, wind, geo-
                           thermal energy, and biomass-would        also reduce the emission of green-
                           house gases7 In 1988, renewable energy provided about 9 percent of the
                           total energy used in the United States. By the year 2000, one report esti-
                           mates that it may provide almost 15 percent of the United States’ total

                           5Life-cycle costs include the purchase price plus operating and maintenance costs expressed in con-
                           stant dollars over the lifetime of the appliance, less its scrap value at the end of its lifetime.

                           “These amounts are expressed in 1982 constant dollars.
                           7Solar and wmd technologies convert these resources into usable high-temperature heat or electricity.
                           Geothermal energy comes from the ireat contained in underground rocks and fluids. Biomass energy
                           is produced from the combustion of organic materials, such as plants. Although the combustion of
                           biomass produces carbon dioxide, the regrowth of biomass to replace what is harvested absorbs
                           carbon dioxide from the atmosphere. As a result, there is no net increase in carbon dioxide.

                           Page 6 1                                                         GAO,‘RCED9@68      Global Warming
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        projected energy needs, displacing over 500 million tons of carbon

        Renewable energy, which is perceived to have a benign effect on the
        environment, is used to produce heat and electricity as described in the
        following examples.”

    l   Photovoltaic cells provide electricity to consumer products, such as cal-
        culators and watches, and to remote locations that have no access to
        electricity. It was reported in 1989 that U.S.-manufactured solar cells
        provide approximately 30 megawatts of electrical capacity.lO As of 1989,
        there were at least 1.2 million buildings in the United States that incor-
        porated some aspect of solar building design, such as solar hot water
        heaters, Solar thermal power is estimated to have produced about 500
        million kilowatt-hours of electricity in 1989.l’
l       In the United States, wind-powered turbines generate approximately 1.8
        billion kilowatt-hours of electricity annually.
l       Geothermal energy is currently used by the United States and several
        other countries to generate direct heat and electricity. In 1988, geo-
        thermal power plants in the United States produced about 20.9 billion
        kilowatt-hours of electricity.
l       Residential wood burning made up about 40 percent of the total wood
        energy used in 1988. Biomass electricity plants that burn sugar cane res-
        idues provided 58 percent and 33 percent of all electricity generated on
        the Hawaiian islands of Kauai and Hawaii, respectively, in 1985.

        The high cost of most renewable energy sources, compared with the cost
        of fossil fuel sources, is considered an obstacle to their increased use.
        For example, according to the Council for Renewable Energy Education,
        electricity from coal-fired power plants costs less (6.8 cents per kilo-
        watt-hour) than electricity generated from solar thermal sources (10
        cents per kilowatt-hour), biomass (8 cents per kilowatt-hour), and wind

        *N. Rader, Power Surge: The Status and Near-Term Potential of Renewable Energy Technologies
        (Washington, DC.: Public Citizen, May 1989), pp. II-2 and III-l.
        ‘EPA has commented that the benign effect of renewable energy is not simply a perception. While the
        use of renewable energy sources does have environmental impacts, they tend to be far less serious,
        more localized, and often easier to address than those caused by the use of fossil fuels,

        “Rader, Power Surge, p. II-36

        “Solar thermal electric power plants basically use mirrors to focus sunlight to heat a fluid that is
        then used to produce steam to run a conventional electric turbine.

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                (6.9 cents per kilowatt-hour). On the other hand, they estimate that elec-
                tricity from geothermal sources and hydropower is cheaper (6.5 and 4.5
                cents per kilowatt- hour, respectively).

                Furthermore, each renewable energy source has specific disadvantages
                that may pose obstacles to its increased USC.For example, photovoltaic
                power stations require large land areas, currently about IO acres per
                megawatt.12 Wind-powered turbines provide intermittent power because
                they generate electricity only when the wind blows. Geological stress
                associated with drilling geothermal projects may contribute to land sub-
                sidence and sink holes. Residential wood burning creates air pollution
                problems, such as the emission of particulates because of incomplete

                EPA  has pointed out that these limitations may have solutions or may not
                exist in all regions of the country. For example, there is abundant land
                in the southwest United States for solar energy installations, and the
                geothermal industry has developed methods of extracting energy to
                limit geothermal stress. Furthermore, EPA has noted that additional
                research for renewable energy would lead to greater implementation of
                these techniques.

Reforestation   According to EPA, changes in land use-including deforestation, the
                burning or ckaring of forest land for other uses, such as agriculture-
                are responsible for about 10 percent of the greenhouse gas emissions
                contributing to global warming. l3 Reforestation of these lands, on the
                other hand, absorbs carbon dioxide from the atmosphere and buys time
                for other policy actions to be implemented. Reforestation could be imple-
                mented by such actions as swapping assumptions of debt with devcl-
                oping countries for environmentally sound programs like reforestation
                and, in the United States, using IJSDA’S Conservation Reserve Program
                for the reforestation of highly erodible cropland.14

                “According to MlE, however, photovoltaic power plants use nearly the same amount of land as
                conventional plants when operations, constrution, extraction, and transportation are taken into

                “‘Rurning fnrest land r&ascs stored carbon dioxide fmm the trees. Clearing forest land removes
                trees that would absorb carbon dioxide fmm the atmosphere through photosynthesis.

                 ‘“The Conservation Hcserve Program assists farmers in converting erodibIe and environmentally sen-
                sitive cropland into forests or grassland. Some organizations that we spoke with bchevc this program
                is the logical place to begin a national reforestation plan to offset carbon dioxide emissions.

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                 One obstacle to reforestation is resistance by developing countries,
                 Many developing countries see few alternatives to clearing forest as a
                 way to earn hard currency, to spur regional economic development, and
                 to open new areas for settlement. For example, in Brazil much forest
                 land has been cleared because government subsidies encourage cattle
                 ranching, even though ranching erodes pasture land and, consequently,
                 the projects are abandoned within a few years.

                 Other obstacles to reforestation include the extensive area required for
                 planting and the question of who will pay for the reforestation. For
                 example, a DOE researcher estimated that the United States would need
                 to plant trees on an area 50 percent larger than its total land area to
                 offset its contribution to carbon dioxide emissions.15 He concluded that
                 the United States cannot absorb all its carbon dioxide with a reforesta-
                 tion program alone and that reforestation should be viewed as a short-
                 term measure that allows time to find alternatives to fossil fuels.

Nuclear Energy   Nuclear energy is a controversial solution to global warming. Proponents
                 of nuclear energy point out that nuclear power plants can decrease the
                 greenhouse effect by substituting nuclear power for fossil fuels to gen-
                 erate electricity. According to one report, nuclear power plants reduced
                 the United States’ emissions from burning fossil fuels in 1987 by almost
                 9 percent and global emissions by over 7 percent.“’

                 Opponents of nuclear energy cite costs, problems in disposing of radioac-
                 tive waste, and the lack of acceptance by the public as the main obsta-
                 cles to the increased use of nuclear energy. Advocates of nuclear energy,
                 on the other hand, believe these problems will be dealt with by the next
                 generation of nuclear technology, which is now under research and
                 development. This new technology, however, is not expected to be in
                 production before the year 2010. Therefore, advocates view nuclear
                 energy as a longer-term strategy for responding to global warming.17

                 ““The Role of U.S. Forestry in Addresing the CO, Greenhouse Problem,” remarks by Gregg Marland
                 before the Senate Committee on Energy and Natural Resources, Sept. 19, 1988, pp. l-2.

                 “U.S. Council for Energy Awareness, Greenhouse Fact Sheet, undated.

                 17DOEhas noted that nuclear power is currently considered a viable option in many countries. In the
                 United States, DOE anticipates that new reactor options may be available as early as 1995 to resolve
                 many technological and operational concerns.

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Strategies to Control   Although they are currently responsible for about half the potential for
                        temperature increase, greenhouse gases other than carbon dioxide,
GreenhouseGasesOthe     when taken together, may surpass carbon dioxide as the primary con-
Than Carbon Dioxide     tributors to potential warming within the next decade (see ch. 2). Strate-
                        gies to reduce energy consumption and production will also reduce the
                        emission of other greenhouse gases, such as methane and nitrous oxide,
                        in addition to carbon dioxide. Other policies can be targeted to specific

                        For example, landfills are a small but potentially controllable source of
                        methane. Waste disposal in landfills and open dumps generates methane
                        when organic material decomposes. These emissions can be reduced by
                        methane recovery systems and by the minimization of wastes.

                        EPA  commented that reducing methane from landfills can have a rela-
                        tively large impact, since only a lo- to 20-percent reduction in methane
                        emissions is required to stabilize atmospheric concentrations. Other
                        areas EPA mentioned for reducing emissions include coal mining activi-
                        ties, animal wastes, and livestock.

                        Several agricultural activities are sources of methane and nitrous oxide
                        emissions: digestive processes in domestic animaIs such as sheep and
                        cattle, rice cultivation, and the use of nitrogenous fertilizer. Several
                        techniques-such       as feed additives for cattle, changes in water manage-
                        ment in rice production, and fertilizer coatings-have been identified
                        for reducing methane and nitrous oxide emissions from these sources.
                        According to EPA, however, these techniques require further research
                        and demonstration before they can be implemented.

                        The production and use of CFCS will be limited by the Montreal Protocol,
                        signed in 1987 by 24 dozen nations. I8 The United States ratified the pro-
                        tocol in April 1988. Under the protocol, the world’s industrial nations
                        agreed to halve production and consumption of CFCS in a decade, to peri-
                        odically assess the protocol’s control measures, and to make changes in

                        IsThe purpose of the Montreal Protocol on Substances That Deplete the Ozone Layer is to reduce
                        WCs because they destroy ozone in the upper atmosphere. In the Iower atmosphere, however, CFCs
                        act as a greenhouse gas, and the protocol, therefore, has the additional benefit of reducing greenhouse
                        gas emissions.

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                         the controls if necessary. In 1989, the United States and several Euro-
                         pean countries agreed to completely eliminate CFCS by 2000.19United
                         States legislators have added such language to the proposed
                         reauthorization of the Clean Air Act.

                         The federal government can use several methods to encourage activities
U.S. Options to Reduce   that reduce the emission of greenhouse gases. As mentioned earlier,
Greenhouse Gas           energy pricing to promote conservation, further research and develop-
Emissions                ment of energy-efficient technologies, and information programs for
                         energy consumers would help to overcome some of the obstacles that
                         hinder limiting the emission of greenhouse gases. In addition, the federal
                         government already has several regulations and programs that affect
                         greenhouse gas emissions, such as air pollution control laws, restrictions
                         on the use of WCS,regulation of investments and rates charged by utili-
                         ties, and energy efficiency standards for automobiles and appliances.
                         These programs were adopted for reasons unrelated to climate change,
                         but could be modified to reduce greenhouse gas emissions even further.

                         Similarly, DOE has been tasked with developing a national energy
                         strategy that could be specifically targeted to reduce greenhouse gas
                         emissions. This strategy is to be completed by December 1990 for the
                         President’s consideration. The strategy will address global climate
                         change within a comprehensive set of energy and other national goals.
                         According to DOE,this plan is expected to serve as a blueprint for energy
                         decisions, providing a choice of competitively priced, clean-energy sup-
                         plies. The strategy will generate several energy policy options, illustrate
                         how each option will be implemented at the program level, and indicate
                         the program’s funding requirements. Furthermore, the strategy is
                         expected to contain specific recommendations on how to best balance
                         concerns for energy, economic, and environmental requirements. DOE is
                         developing models for the strategy that will project the impacts of
                         various energy options on such issues as global warming.

                         In addition, the federal government needs to examine policies and pro-
                         grams that may inadvertently exacerbate the threat of global warming.
                         For example, “scrubbers” may be used on electric power plants to
                         reduce sulfur dioxide emissions and thereby limit acid rain. IIowever,

                         “‘According to EPA, the protocol’s impact on global climate is difficult to determine because (1) WCs
                         that are already in the atmosphere will remain there for about 100 years and (2) the effect on climate
                         of substitutes for WCs remains unknown. However, according to NOAA, these substitutes have much
                         shorter lifespans, although their greenhouse potential is roughly the same as CEYZson a molecule-per-
                         molecule basis.

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                      scrubbers will increase carbon dioxide emissions by reducing the effi-
                      ciency of power plants. Another policy, to reduce the production and use
                      of CFCS as part of the Montreal Protocol agreement, could unintention-
                      ally increase the emissions of other greenhouse gases Some substitutes
                      for CFCS are less energy-efficient and, therefore, could result in increased
                      carbon dioxide emissions.

                      Responses to global warming require a combination of immediate and
Timing of Responses   long-term policies. For example, pricing and regulatory strategies may
to Global Warming     be effective in the short term, while government-supported research,
                      development, and information programs may reduce greenhouse gas
                      emissions in the long run. Actions now may be desirable for several rea-
                      sons: Some actions cannot be implemented immediately for political and
                      economic reasons once it is agreed they are needed, and concentrations
                      of greenhouse gases will decline only gradually even after actions are
                      implemented. Many organization officials that we spoke with support
                      taking actions to reduce greenhouse gas emissions as soon as possible,
                      rather than waiting until the earth is committed to potentially harmful
                      warming. Furthermore, some organizations believe that actions in the
                      near future should emphasize activities that have benefits in addition to
                      reducing the emission of greenhouse gases.

                      If policymakers wait until the scientific uncertainties are reduced to
                      respond to global warming, they risk committing the earth to even more
                      warming. Once greenhouse gases have entered the atmosphere, they
                      continue to affect the climate for decades. If all man-made emissions of
                      carbon dioxide were eliminated now, it could take more than a century
                      for the oceans to absorb enough carbon to reduce the atmospheric con-
                      centration of carbon dioxide even halfway toward its preindustrial
                      value. With continued emissions, the time required to reduce excess con-
                      centrations by the same percentage increases even more. In addition, the
                      climate’s response to increases in greenhouse gases will be delayed
                      because the ocean has a limited capacity for absorbing heat. Similarly, in
                      response to decreases in greenhouse gases, temperatures will also cool
                      more slowly because of the ocean’s effect on climate,

                      Furthermore, policy development and implementation can be a lengthy
                      process, particularly at the international level. For example, it took
                      roughly a decade to develop and ratify the Montreal Protocol, and it
                      may take even longer to reach agreement on other greenhouse gases,
                      such as carbon dioxide, because the emission sources are more diverse

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                     and more countries are involved. In addition, implementing new technol-
                     ogies to reduce greenhouse gas emissions may take many years. For
                     example, the next generation of nuclear energy technology, which is
                     now under research and development, is not expected to be in produc-
                     tion before the year 2010.

                     While ongoing and planned research is expected to help reduce some of
GAO’s Observations   the scientific uncertainties surrounding global climate change, quick
                     fixes or easy answers are unlikely to emerge. Rather, research results
                     are anticipated to continue pointing to the need for developing a com-
                     prehensive multinational, multidecade response strategy requiring a mix
                     of near-term and long-term actions. In the near term, there is a growing
                     recognition that certain actions can be justified because they have bene-
                     fits in addition to reducing greenhouse gases. Reducing CFCS is an
                     example of such an action already underway. Other actions, such as
                     national efficiency standards for new appliances and similar improve-
                     ments in energy efficiency, can have a near-term impact on reducing
                     greenhouse gas emissions and, while progress has been made, more can
                     be done. Also, the current situation in the Persian Gulf highlights the
                     need to lessen dependence on foreign oil, and such measures as
                     increasing the domestic use of renewable energy and energy-efficient
                     technologies would help to achieve this goal. Other actions that make
                     sense for other reasons and would help to reduce the effects of global
                     warming include: promoting investments in energy-efficient technology
                     to reduce energy costs and to meet the need for new generating capacity;
                     and promoting waste reduction and recycling as alternatives to land dis-
                     posal to address the high cost and environmental risks associated with
                     traditional disposal methods.

                     Long-term solutions, however, raise broad issues that need to be consid-
                     ered on national and international levels in developing a comprehensive
                     strategy to deal with global warming. For example, what acceptable
                     alternatives to fossil fuel use are available to mitigate the projected
                     global warming? How does the relatively low price of fossil fuel energy
                     hinder increased energy efficiency and the use of alternative energy
                     sources, such as solar energy? Will the public accept changes in lifestyle
                     that may be necessary to decrease the emission of greenhouse gases?
                     What is the potential, among so many nations, for achieving cooperation
                     and coordinated action in a timely, effective manner? Will the industri-
                     alized world be able to work with and understand the special needs of
                     developing countries in decreasing their fossil fuel emissions? Who can
                     and will pay for policies to reduce greenhouse gas emissions? What

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                     actions, if any, need to be taken to adapt to’s changing climate? What
                     are the estimated costs of actions to reduce greenhouse gas emissions
                     and adapt tg climate change?

                     Despite such unresolved issues, our work suggests that actions such as
                     increasing energy efficiency make sense for other reasons as well and
                     should be implemented on both the national and the international level.
                     More importantly, the threat of enhanced global warming in and of itself
                     should serve as a catalyst to take action now.

                     EPA agrees that there are many opportunities for reducing the emission
Agencies’ Comments   of greenhouse gases at low costs, including opportunities to improve
                     energy efficiency and to increase the use of renewable energy. However,
                     EPA believed that this chapter omitted any reference to the international
                     consensus on the urgent need for a framework convention on climate
                     change and the United States’ active role in that process. We agree that
                     this is an important issue but excluded it from this report because the
                     llnited States’ international efforts concerning global warming were
                     addressed in a recently issued GAO report, Global Warming: Administra-
                     tion Approach Cautious Pending Validation of Threat (GAO/NSIAD-90-63).

                     In addition, EPA felt that several issues had not been addressed in this
                     chapter or needed further elaboration. Where appropriate, we have
                     included additional information provided by EPA on (1) renewable
                     energy sources and (2) strategies for reducing methane emissions.

                     KOAAstated that the report should include a chapter surveying estimates
                     of the net economic costs associated with global warming and the eco-
                     nomic costs of mitigation and adaptation strategies. Similarly, QOE
                     believed that the report should discuss the costs and benefits of
                     reducing emissions. We recognize that there are economic trade-offs that
                     must be considered in any emissions reductions strategy, However, we
                     found that certain actions, such as improvements in energy efficiency,
                     have benefits in addition to reducing greenhouse gas emissions and
                     could be implemented now.

                     DOE also said that our discussion of the potential for nuclear energy to
                     reduce greenhouse gas emissions should be made more factual and con-
                     sistent with the discussion of other technologies. We know of no infor-
                     mation in the section that is not factual; however, we have expanded
                     that. discussion by adding DOE'S specific comments.
                     KASA did not comment on this chapter.

                     Page 59                                         GAO/RCED-90-68   Global Warming
Appendix I

DOE’s Comments

                                      The Under Secretary     of Energy
                                            Washington,DC 20585

                                             Iaarch 29, 1990

             Mr. Richard L. Hembra
             Environmental   Protection Issues
             United States General Accounting        Office
             Washington,   DC 20548
             Dear Mr. Hembra:
             Thank you for the opportunity      to comment on the draft General
             Accounting  Office   (GAO) Report:       llGlobal Warming:   Emission
             Reductions  Possible    While Scientific       Uncertainties Being
             Resolved."    Department of Energy comments are detailed          in the two
             enclosures  to this letter:     Enclosure       1 - General Comments, and
             Enclosure  2 - Specific     Comments.
             Among the Department's     primary   concerns      detailed        in the
             enclosures are:
             0    a discussion    of costs and benefits     of emissions  reductions
                  should be included       in this report to provide a more
                  comprehensive    analytical     framework for a government strategy
                  on climate    change:
             0     the report would be strengthened        if historical   and more
                   recent climate     data were considered    in the discussion     of the
                   effects   of increased    greenhouse gas concentrations      on
                   potential   climate    change:
             0    the results    of models providing     estimated    changes to global
                  average temperature      in Table 3.1 and the accompanying
                  discussion    should be more complete,      especially    reflecting
                  recent model results       where cloud and ocean effects        are more
                  realistically    simulated;
             0    the discussion  of appropriate  criteria   for near-term                    actions
                  to reduce greenhouse gas emissions should emphasize                        actions
                  that also serve other policy   objectives;
             0     the report should    discuss the potential             for   beneficial
                   impacts of climate    change: and

                   Page60                                                       GAO/RCRD9@68GlobalWarming
        Appendix I
        DOE’s Comments


0       discussion       of the potential     for nuclear energy to reduce
        greenhouse       gas emissions    should be made more factual   and
        consistent       with the discussion     of other technologies.
Your report     indicated     that it relies    on data available through
last October.        Yet, as our comments note, some of the information
contained     in the report is already out of date because of
recently-announced        scientific  discoveries.
Over the next six months, the Intergovernmental              Panel on Climate
Change (IPCC) will     report on our scientific         understanding      of
global climate    change, the potential      impacts of global climate
change, and the economics of various         response strategies         to
potential  climate    change.     Given the IPCC activities,         and other
ongoing global climate       change-related   activity,      it will   be
virtually  impossible     for this report to remain current.
Publishing   the report now, however, will         convey the impression
that it represents     the best and most recent information            that is
available,   an impressions     that will   not be correct.
We suggest that holding     the report in draft    over the next several
months will  allow GAO to incorporate      more current   scientific  and
economic research results.       The Department of Energy would be
pleased to work with you in such an endeavor,        which we believe
would result   in a better,    more useful report.
Also, enclosed is the Executive   Summary of the Department's
Atmospheric  Radiation Measurement (ARM) Program Plan.      The ARM
Program should improve the treatment     of cloud radiative  forcing
and feedbacks on the General Circulation     Models.
We would     be happy to discuss        any of our comments with    you.

                                  John C. Tuck

        Page61                                              GAO,‘RCEIHO-68    Global Warming
Appendix II

EPA’s Comments

              g* * Fs5           UNITED   STATES   ENVIRONMENTAL          PROTECTION         AGENCY
              p&;                                  WASHINGTON.     D.C.    20460

               8,   ..&”

                                                                                                    OFFICE     OF
                                                                                   POLICY,    PLANNlNG       AND    EVALUATtON

                    Mr. Richard L. Hembra
                    Director,   Environmental     Protection Issues
                    Resources,   Community, and Economic Development                          Division
                    General Accounting     Office
                    Washington,   D.C.   20548
                    Dear Mr. Hembra:
                          The Environmental         Protection   Agency (EPA) has reviewed the
                    General     Accounting     Office     (GAO) draft   report  entitled     "Global
                    Warming:          Emission       Reductions    Possible    While     Scientific
                    Uncertainties     Being Resolved" (GAO/RCED-90-58).        In accordance with
                    Public Law 96-226, I am hereby providing          the formal Agency response
                    to the draft     report.
                            The GAO draft report represents         a substantial          compilaticn    of
                    ongoing work, and achieves a well balanced view of the issues.                        In
                    particular,          it notes   the current      limitations         in atmospheric
                    modeling       and the uncertainties     about global        climate     change which
                    follow      from those limitations,     while recognizing          that actions      can
                    be taken now to begin reducing             greenhouse        gas emissions.          The
                    report also notes that many of the key policy questions                     are yet to
                    be answered, such as whether individuals              will    be willing     to change
                    their     lifestyles     and how policies      to reduce emissions              will  be
                          While  the report        examines    many of the current           issues
                    surrounding  global    warming, its usefulness        could be strengthened
                    by expanding    it beyond a description           of the current     state    of
                    knowledge to describe      the range of activities        and progress being
                    made to answer many of the questions         it poses.     Our understanding
                    of the issues continues      to improve rapidly,       and a better   sense of
                    where the basic     research     and policy    analysis     is heading would
                    improve key decision     makers' abilities      to provide proper guidance
                    and support.
                          Some general    comments on the content    of the report    follow;
                    page-by-page     comments are enclosed. In addition,   the draft copies
                    being   returned    to you under separate     cover contain    editorial
                    comments in the margins.

                           Page 62                                                              GAO/RCED-90-68            Global Warming
        Appendix II
        EPA's Comments

Scope of the Report
       A major     limitation       of the draft     report is that it is limited
to surveying      what is known about the physical                 climate       system.     An
equally     important       and challenging      task is to survey what is known
about the response of living              systems to climate            change.      Biogenic
feedbacks can be triggered              as the earth's         temperature        warms.     An
example of such a feedback is methane release                         from tundra areas.
With these feedbacks,            some scientists      estimate     that average global
temperatures         could increase       by 14 degrees Fahrenheit                  or more.
While     estimates        are uncertain,         such information             is valuable
because, as the draft             acknowledges,      climate     will     probably      change
to some degree.          Policy makers require          such Information          to balance
costs    and benefits          of mitigation        actions.          In addition,        this
information      will      assist    in developing        adaptation       strategies       for
environmental         changes induced by a changing climate.                      The nearly
complete omission of this important                area of environmental             xesponse
limits    the overall        usefulness    of the report.
       The draft     report    emphasizes the use of general circulation
models ( "yy      r but does not recognize           the usefulness   of other
modeling            analytical      techniques,     for    example, radiative-
convective    models and chemistry       models.   Like GCMs, each analytical
tool    has its       strengths,      weaknesses     and general    domain     of
usefulness.      Their omission from this draft creates the misleading
impression    that the only scientific        means of studying the influence
of increasing      greenhouse gas concentrations         is through the use of
GCMs. Chapter 2 and the Executive               Summary should be expanded to
cover non-GCM analytical         tools.
        One limitation        of the GCMs is that they do not include                the
possible      effects      of biogenic      feedbacks,       as discussed        above.
Another is their lack of credibility             in predicting     regional    climate
change.     However, this does not mean that they should be abandoned
for regional        scale predictions.          The results     of modeled global
climate    change must make qualitative               sense on smaller         spatial
scales.     Some recent satellite          radiation     budget experiments        have
shown that there is an encouraging               consistency     between model and
observed     climate       sensitivity.       It is clear        that    progress      in
understanding         climate      change can come only         from observations
complementing       modeling studies.

       Page63                                                         GACJ,'RCED-!3@SSGlobalWarmIng
       EPA’s Comments

Estimates     of Greenhouse        Gas Emissions
        The report correctly       notes that estimates    of future growth of
greenhouse gas emissions          are uncertain.      However, it is important
to note that projections            are being made by the U.S.         and other
countries      based on a number of assumptions             about energy use,
population      growth, and economic productivity.          These are the same
type of projections         (with the same uncertainties)         that are made
every day in planning          processes,     and this is being performed as
part     of the IPCC (Intergovernmental             Panel of Climate       Change)
process.        These projections        are reasonable     scenarios     for the
future,    and based on these scenarios,          the U.S. and other countries
can begin to plan and determine            the types of reductions      that will
be necessary       to limit   emissions     of greenhouse gases.      A range of
estimates     is available     for the IPCC report and may be cited in the
GAO report.
        Further,       it    should      be emphasized       that    there       is strong
scientific         consensus        that    there    will      be an increase                 Fn
concentrations            of   greenhouse       gases     resulting       in       increased
temperatures.             While     model limitations          do not allow             us to
accurately        predict      the extent       and timing        of the temperature
increase,        evidence      of warming above natural              variability          will
probably     become apparent early in the next century.
Emissions     Reductions
        The Agency          agrees     with     the GAO that             there      are many
opportunities         for reducing        emissions       of greenhouse gases at low
costs.      As indicated          in the draft        report,      these include        energy
efficiency       and increased         use of renewable           energies.         They also
include     reducing       methane from landfills.               The GAO report         states
that this is a relatively             small source.          However, reducing methane
from landfills         can have a relatively            large impact since only a 10
to 20 percent            reduction      in methane emissions               is required       to
stabilize      atmospheric         concentrations.           Other areas for reducing
emissions       include      coal mining         activities,         animal     wastes,     and
livestock.        In addition,       measures to increase sinks for atmospheric
carbon through          sequestration       or other biological            means should be
mentioned.          The report       should observe that these opportunities
exist and that in some cases additional                     research,     particularly      for
renewable      energy, would lead to greater                   implementation         of these

        Page 64                                                        GAO/RCED-9&5BGlobalWansing
                     Appendix II
                     EPA’s Comments

                     While there are disadvantages           to different        types of renewable
              energies,     these limitations        may have solutions         or may not exist in
              all regions of the country.              For example, there is abundant land
              in the southwest United States for solar energy installations,                        and
              the geothermal         industry      has developed         methods of extracting
              geothermal      energy to limit         geothermal     stress.        Thus, renewable
              energies    may play      a large role in regional              strategies     to limit
Now on p 52   emissions      of greenhouse gases.           Further,       on page 57, the draft
              report     states     that      renewable     energy      is     "perceived"      to be
              environmentally       benign.       This is not simply a perception.                While
              the use of renewable              energy    sources     does have environmental
              impacts,     they tend to be far less serious,                  more localized,       and
              often easier to address than those caused by fossil                       fuel u8e.
              International        Policy     Framework
                      Finally,       the report's         discussion       in Chapter 4 of a "policy
              framework to address global climate                     change" omits      any reference       of
              the international             consensus on the urgent need for a framework
              convention        on climate       change and the United States'              active role in
              that process.           Further,      the discussion         of the timing of responses
Now on p.57   to global warming (on page 64 of the draft report)                          also appears to
              ignore a significant             commitment by industrialized             nations as stated
              in paragraph          16 of the Noordwijk               Declarationr        "Industrialized
              nations      agree that...        stabilization         [of greenhouse gas emissions,
               'while    ensuring       stable development of the world economy,']                      should
              be achieved by them as soon as possible,                      at levels to be considered
              by the IPCC and the second World Climate Conference                               of November
              1990."        Similarly,        in paragraph         29, the Declaration            "urges all
              involved         or to be involved                 in     the     [framework      convention]
              negotiations         to do their        utmost to conclude these negotiations                  to
              ensure adoption of the convention                    as early as 1991 if possible            and
              no later          than at the Conference                   of the United          Nations      on
              Environment         and Development            in 1992."         The Administration          has
              offered     to host the first            negotiating       session for a global climate
              convention        and continues        to support an acceleration             in analysis      of
              targets     and options         as identified         at the Noordwijk        Conference.
                     Thank you for          the opportunity       to respond     to the draft        report.

                                                                  Assistant      Administrator


                     Page 65                                                         GAO/RCED-9048      Global Warming
Appendix III

NASA’s Comments

               Washington, D.C.

                                                                                       April    21, 1990

               Mr. Richard L. Hembra
               Director,   Environmental Protection    Issues
               United States General Accounting     Office
               Washington,   DC 20548

               Dear   Mr.    Hembra:

                     The National    Aeronautics    and Space Administration    (NASA)
               appreciates   the opportunity      to review and cormnent on the
               General Accounting     Office    (GAO) draft report entitled,   u
               1         :
               Uncertainties    Being Resolved (GAO/RCED-90-58).
                     NASA applauds the efforts      by the GAO to address the very
               complex and important      issues related    to global warming. There
               is a compelling    need to help policy     makers understand     the
               complexities    and uncertainties    surrounding    these issues so that
               governments can make informed decisions          and take actions that
               are soundly based.     The report has the potential       to help meet
               this need.
                         Unfortunately,       the depth and timeliness               of the report are
               handicapped         in two ways.       First,     page limitations           prescribed
               for GAO reports            lead to a treatment         of the issues in the
               Executive        Summary in a manner that risks presenting                      the diverse
               and complex problems related                to understanding           and forecasting
               global warming in an oversimplified                   manner.         Consequently,       a
               careful       reading of the main body of the report will                       be
               essential        for anyone who wishes to begin to understand,                       for
               example, the distinctions              between deforestation              and fossil      fuel
               burning       as sources of carbon dioxide              at different         times in
               history,       the uncertainties         regarding      the loss mechanisms for
               carbon dioxide,            the uncertainties        regarding       the sources of
               methane and nitrous            oxide, and the meaning of the use of an
               'equivalent"          doubling    of carbon dioxide           by modellers.         Even in
               the main text,           report length constraints             have apparently         forced
               the GAO authors to neglect               important      considerations          such as the
               relative       roles of additional          radiative       forcing     agents other
               than greenhouse gases (e.g. aerosols,                     albedo,      solar
               variability)         and the relatively         poor state of development of
               global ocean circulation             models compared to global atmospheric
               circulation         models.

                      Page66                                                          GAO/RCED-9048GlohalWam1@


        Second, the report is limited        by having to treat a rapidly
evolving      body of scientific     knowledge while being constrained
to rely on material       already available        in the published
literature.       A major new report by the Intergovernmental              Panel
on Climate Change (IPCC) is now undergoing               review for release
later     this year.    That report is likely         to present important
new findings      and improved assesements of key questions             such as
the range of temperature         increases   predicted      by high resolution
models, estimates       of the atmospheric      lifetime     of carbon
dioxide,      and the use of coupled ocean-atmosphere           models.
Consequently,       we must remember to encourage interested            readers
to study also the IPCC report when it becomes available.
       Finally,      I want to express my appreciation       for the
opportunity       for members of NASA's technical      staff    and your
audit staff       to have a number of very positive       and constructive
discussions       during our review of the draft     report.

                                           Assistant    Deputy Administrator

Atmendix IV

NOAA’s Comments

                                                                   u#mnc      ETATEE    DmPARTMmrr    OF GOMMIRCE
                                                                   wuhlngton    O.C. 20230

                    Mr. Richard L. Hembra
                    Director,   Environmental  Protection     Issues
                    Resources,   Community, and Economic Development                       Division
                    United States General Accounting      Office
                    Washington,   D.C.   20548

                    Dear    Mr. Hembra:
                    Thank you for your letter      requesting    the Department's       comments on
                    the draft General Accounting       Office report     entitled    Global
                    Warminu:      Emission Rsduc!       Possible    while Scientific
                    Uncertainties      Beina &g~&&     (GAOjRCED-90-58).
                   Due to the time constraints,              we have only been able to give this
                   draft GAO report a cursory review.                We do have some difficulty
                   with the report        in that it does not represent              a true scientific
                   consensus of global warming phenomena; rather,                      it is a summary of
                   recent,    but not current,         findings    of individual         groups. As such,
                   the report,    written      by non-scientists,         tends to over-simplify       a
                   real and very complex scientific              issue, thereby potentially
                   distorting    policy     deliberation.        For example,        the report cites a
                   much higher temperature           range (5-8 degrees F) than the current
                   best estimates       (3-8 degrees F) and does not address the recent
                   model findings       of hemispheric        temperature     differences.
                    The    report makes an assumption that the effects         will  occur and
                    that they will        be negative,   even though there is, as yet,
                    uncertainty        in many areas.    The new findings   suggest that future
                    changes may not be as severe as indicated.            Indeed, the United
                    States is only just embarking on a major research program to
                    attain     a better    understanding   of the entire  climate   system.
                   It is also very important                  to note that an internationally-
                   acknowledged assessment                  of the science,      response strategies,   and
                   impacts of global change                  will  be forthcoming      this summer from the
                   Intergovernmental       Panel            on Climate Change.        These assessments
                   have been made by experts                   in relevant   fields    and will  be a more
                   up-to-date    evaluation     of           global change than this GAO report.

              75 Years Slimulallng   America’s   Progress   * 1913-1988

                             Page68                                                         GAO/RCED9@68GlobalWarming
                     NOAA's Chnments

              We agree with the issue formulation          offered    by GAO--that policy
              makers must "weigh the risk of more adverse impactsl' against
              taking *'costly   actions I' that may prove unwarranted.
              Unfortunately,    the report does not follow         through by analyzing
              information    on the economic costs of global warming essential            in
              calculating    the costs of mitigation      or adaptation     strategies,
              though some estimates     have been developed by private           sector and
              government analysts.      Nor does the report offer any analytic
              framework for evaluating       these issues.
              As the need for policy         makers to consider   economic effects    is
              critical,     we recommend that GAO add a chapter to the report
              surveying     estimates    of the net economic costs associated      with
              global warming and the economic costs of mitigation             and
              adaptation     strategies.      At a minimum, we feel that GAO should
              explicitly     indicate    that economic information     is required   before
              policy     makers can judge whether proposed actions        are warranted.
              The specific     view offered   by GAO that its work "shows that"
              actions    such as increasing     energy efficiency      "makes sense for
              other reasons"      is not supported by the discussion         or evidence in
              the draft report.       Though noting that lVsome environmental           groups"
              believe    that the price of energy 18does not reflect           its true
              social   cOst*l, no further    evidence is offered       to indicate    that the
              true social     cost of energy is higher than current          prices.     We
              recommend that this concJ.usion either          be deleted or that the
              supporting     work be included    in the report.

              Additional,     specific    comments follow:
                 3                    . ..half of the expected temperature    (l'potential
                                     temperature"    has a precise scientific     meaning;
                                     its use as a phrase should be avoided in this
                 4                   This is inconsistent     with the body of the text.
                                     What is really    said is the ensemble of
                                     greenhouse gases are expected to increase       such
                                     that their   net effect   is radiativelv eauivalent
                                     to a doubling   of CO* itself.
Now on 0.16    13                    Greater mention of the central         role of CES on
                                     the interagency     is warranted.      Rather than
                                     simple coordination,     CES has put together       an
                                     overall   program together     with joint    agency
                                     budget submissions.      Overall    research priorities
                                     have been developed with the concurrence           of the
                                     NAS Committee on Global Chanqe.

                     Page69                                                GAO/RCED90-SSGlobalWarn&q
                            Appendix IV
                            NOAA’s Comments


Nowonp    17.       14                   .f.     Geophysical           Fluid    Dynamics...
Nowonp    17.       14                   "Joint  Oceans Institute"                should be Joint
                                         oceanographic  Institutions,                 Inc.
Now on p. 18        15                   . . . objective,         we obtained...
Now on p. 23        21                   Despite the DOE reference,        the statement that
                                         "all of the increase        [in atmospheric  carbon
                                         dioxide]     is due to human activities"     is a bit
                                         strong in light       of our present understanding    of
                                         natural     sources and sinks in the global carbon
                                         cycle.      A major debate is currently     underway as
                                         to whether a major Northern Hemisphere
                                         terrestrial      sink exists.
Now on p, 30.       29, footnote         This is not right      (see pg.4,Par.2,lns.3-4
                                         comments above).       you might try:      (lns.2-4,
                                         . ..that    the effect  of a suite of trace gases
                                         acts to change the infrared       radiative       forcing             by
                                         an amount equivalent      to that which would be
                                         produced by a doubling      of COz only.        Modelers
                    30                    . ..according         to most scientists,...
Deleted             30, footnote          . ..Sulfur        dioxide     could    cause clouds       to...
                    31                   The model results      cited in Table 3.1 are, I
                                         believe,   equilibrium      calculations.        Therefore
                                         they cannot give information            on timing of
                                         projected   warming.      Other model calculations
                                         cited in the text are indeed time-dependent;                         the
                                         difference   should be spelled          out.
Now on p. 31        32                   . . . scientists        at GISS...
Now on p. 34.       36                   . ..phenomena...
Now on pp. 40-41    44                   If the discussion  of current and future climate-
                                         related  satellite plans is needed, mention of
                                         only ERRE and TPMM is quite a short list.       What
                                         about EOS? This is by far the largest     single
                                         item in the U.S. Global Change Research Program.
Now on pp, 44-60.   47-66                It is beyond NOAA's scope to comment directly        on
                                         policy    recommendations.     However, a few points
                                         of detail     are noted below.

                            Page 70                                                           GAO/RCEIMO-58   Global Wuming
                      Appendix ISJ
                      NOAA’s Comments


Now on p, 55     61                    This statement    is only partially         correct.    It is
                                       only the combustion-related       pieces of the
                                       methane (natural    gas losses) and nitrous          oxide
                                       that are directly    related   to carbon dioxide
                                       controls.   The agricultural,       fertilizer,      and
                                       animal sources probably dominate.
Now or- p. 56    62,footnote           The climate       and ozone effects       anticipated     from
                                       HCFC's and related        compounds are already rather
                                       well characterized.         Roughly, their         greenhouse
                                       potential      is the same as CFC’s on a molecule-
                                       per-molecule       basis.   Their appeal is because
                                       they have much shorter         lifetimes.         This reduces
                                       their     concentrations    for a given source strength
                                       and allows less reactive           chlorine     to be
                                       liberated      in the active ozone layer.

                We appreciate   this     opportunity      to comment on the draft         report.

                      Page 71                                                    GAO,‘RCED-9&68     Global Warming

Major Contributors to This Report

                        Peter F. Guerrero, Associate Director
Resources,              William F. McGee, Assistant Director
Community, and          Teresa F. Spisak, Evaluator-in-Charge
                        Angela R. Crump, Evaluator
Economic                Cynthia L. Jorgenson, Evaluator
Development Division,   Philip G. Farah, Economist
Washington, DC.

(089443)                Page 72                                 GAO/RCED-90-68   Global Warming
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