then we need to work very hard on doing that, and that is a technological option we should pursue.

Well, in summary, I think there is no doubt that human activities are altering atmospheric composition, that model studies and paleoclimatic studies indicate that is going to lead to significant changes in climate, that there is a potential for important impacts in that regard. You can argue about how the impacts relate to economic costs, and that is a very difficult issue.

I think, as I said earlier, what has happened in the United States is there has not been enough effort to try and synthesize and integrate all of the different points and to consider the critiques and put them together with the adherence, that there has been a tendency in U.S. scientific activities to fractionate to smaller and smaller projects in more and more places. I do not think this has been very helpful. So, I would encourage and have been encouraging the Committee on Earth and Environmental Sciences in some sense to focus at some of the major centers. Some of those include the National Center for Atmospheric Research. They include Goddard. They include the University of California system, of which Livermore and Los Alamos are a part and the various campuses. There are some places that are trying to get started in that regard, that are trying to address various aspects of the problem, but it is not happening I think as much as it should. I would urge more effort in that regard.

Thank you.

[The prepared statement of Dr. MacCracken follows:]

PREPARED STATEMENT OF DR. MICHAEL C. MACCRACKEN, DIVISION LEADER, ATMOSPHERIC AND GEOPHYSICAL SCIENCES DIVISION, LAWRENCE LIVERMORE NATIONAL LABORATORY, LIVERMORE, CA

Mr. Chairman, members of the Committee, my name is Michael MacCracken. I am Division Leader for Atmospheric and Geophysical Sciences at the Lawrence Livermore National Laboratory in Livermore, California. It is a pleasure and a challenge to be invited before you to provide perspective on what is known and not known about the effects of human activities, particularly greenhouse gases, on climate and the environment. My oral presentation will be drawn from my written text, which I request be included in the record. Two written reports and two books of which I was an author or major contributor have also been submitted to the committee staff. 1 2 3 4

As Division Leader at LLNL, I oversee a $20M per year research program supported by DOE, NASA, EPA, DOD and other governmental and private organizations, a program that has rather extensive collaborations with scientists in the university community and other laboratories. The primary focus of our efforts is to simulate, understand, and project the consequences to the climate and environment arising from the release of a wide range of substances into the atmosphere. Examples include radionuclides that might be released from accidents at a nuclear reactor or during weapons transport; aerosols released by the Kuwaiti oilfield fires, biomass burning, or created by emissions of sulfur oxides; chlorofluorocarbon releases that affect the ozone layer; and emissions of carbon dioxide and other greenhouse gases that affect the climate.

"Ten Key Questions Indicating the Level of Current Uncertainty in Forecasting Climatic Change," LLNL report UCRL-ID-106243, February 1991.

2 "The Environmental Dilemma of Fossil Fuels," LLNL report UCRL-106406, April 1992, copy attached.

3 Energy and Climate Change, Report of the DOE Multi-Laboratory Climate Change Committee, Lewis Publishers, Boca Raton, FL, 161 pp.

* Prospects for Future Climate, A Special US/USSR Report on Climate and Climate Change, Lewis Publishers, Boca Raton, FL, 270 pp.

3

As further background, I was one of the original promoters in 1975 of a carbon dioxide research program in the Energy Research and Development Administration (ERDA), the predecessor to the Department of Energy (DOE), and I have been an advisor to their program for about fifteen years, helping provide perspective, interpretation, and integration of scientific results. In 1990, I chaired a multi-laboratory committee of DOE laboratory scientists that prepared the review report Enerey and Climate Change at the request of DOE and in support of their preparation of the National Energy Strategy. I currently serve as chief scientist for the Department of Energy's Computer Hardware, Advanced Mathematics, and Model Physics (CHAMMP) program.5 This program is working to develop, verify and apply a new generation of climate models that takes full advantage of the new massively parallel computers being developed and applied by the High Performance Computing and Communications Program. I also participated, as a scientific advisor to the U.S. delegation at the IPCC Working Group I meeting in Guangzhou, P.R.C., where I contributed to development of the latest in a series of improving efforts to state the scientific consensus on the climatic effects of greenhouse gases; I commend the report to your attention.6

With this background, I want to indicate that, while I have solicited comments on my draft statement from DOE and within LLNL, these views represent my own perspective on the status of scientific understanding of greenhouse gas induced climate change, and, very briefly, on consequent impacts and possible responses.

In thinking about the greenhouse gas issue, it is important to consider separately (1) the direct climatic and chemical effects,

(2) the consequent impacts on the biosphere and on human activities, and (3) the possible responses and options to address the climatic effects and environmental impacts in the broader societal and economic context.

It is my belief that mixing of these three aspects of the issue has been an important contributor to the heated debate on this issue. For example, because the issue of impacts is so difficult, there has often been a tendency to jump from the clear indication that the climate is and will be changing to the consideration of policy options. Much of the controversy about the greenhouse issue arises because of differing perspectives among those who make the jump. Those who are cautious about endangering the environment focus on possible extrapolations from what is known. Those who are cautious about endangering the economy focus on the limitations of scientific understanding. Both sides paint what the other side says in extremes (and there always seem to be apocalyptic statements that can be quoted); then each side takes devastating pot-shots at the opposing side's positions. It should not be surprising then that discourse is filled with differing portrayals of the science or that surveys which ask questions with particular slants or phrasing get differing and divergent results.

7

In the few minutes that I have available I want to present what I view as the plausible middle ground, a centrist position that arises from our attempt, as one of several major modeling centers around the country, to provide a perspective that integrates across the research done at Livermore and elsewhere, both research and comments supportive and critical of this issue. I offer six tenets on which I believe there is broad agreement, even if there are differences on the quantitative details. For each of these statements, the attachment to my written testimony offers supporting points and appropriate qualifications. I would hope that these aspects could be discussed more fully in the questions and responses that follow. The six tenets on which I believe there is broad agreement are:

1. Atmospheric composition is changing as a result of human activities, with carbon dioxide levels up 25% and methane concentrations having doubled since the beginning of the Industrial Revolution and the expansion of agriculture. 2. Atmospheric composition is an important determinant of controls the Earth's temperature and the overall climate.

3. Despite their shortcomings, computer models have many strengths and are the best tools available for understanding and projecting climatic change.

4. Model calculations indicate that past and anticipated changes in atmospheric composition are committing the world to significant climatic change. Regional details, however, remain quite uncertain.

5 Building on Advanced Climate Model, Program Plan for the CHAMMP Climate Modeling Program, DOE report DOE/ER-0479T, December 1990.

Intergovernmental Panel on Climate Change, Working Group I 1992 Supplement, 1992.

7 Kaula, W.M., and D.L. Anderson, 1991, "What is AGU's Proper Role in Society?", EOS, 72,

5. Although global warming of 0.3 to 0.6 has occurred, quantitative association of the observed warming with the greenhouse gas-induced climatic change is not yet sufficient to significantly reduce uncertainties about the details of future warming. With the improving quantification of the moderating effects of aerosols on global warming, however, the models and observations are no longer in troubling conflict.

6. Although future warming may be somewhat intermittent due to natural climatic variations induced by volcanic eruptions and air-sea interactions, the warming influences of greenhouse gases over the next several decades are likely to increasingly exceed the cooling influences of aerosols from fossil fuel combustion, of aerosols from biomass burning, and of ozone depletion.

Although not directly the subject of this hearing, what is known and uncertain about climatic effects is often invoked in statements about possible impacts and potential responses. With the set of stipulations about climatic results that I have just enumerated, I would add the following two points about impacts and options:

7. The potential environmental and societal impacts of changes in climate and atmospheric composition are relatively uncertain, due in part to uncertainties in climate model results, in part to poor understanding of impacts and limited development of impact methodologies, and in part to uncertainties about how future society and technology will evolve. Overall, although agricultural productivity may improve in some situations, there will be negative impacts in many regions on water resources, coastal habitats, ecological systems, health, and in many nations with one crop economies.

8. With fossil fuels supplying greater than 80% of the world's energy and with the global population growing rapidly, there is no single alternative energy system ready to take over as a global energy source. Developing approaches to energy supply that take advantage of the regional climate characteristics may be an important step in moving toward a more environmentally sustainable energy system. Research that builds flexibility and a range of energy options would help prepare for the future, as well as being essential for U.S. competitiveness.

SUMMARY

In summary, when evaluations are not overly burdened by either economic or environmental biases, I believe that scientific understanding can be expressed in a way that can be widely supported and that properly express the importance of the problem. There is definitive evidence that human activities are altering atmospheric composition. Model results and paleoclimatic analyses are both consistent with the proposition that past and future changes in composition are and will continue to lead to alteration of the global climate and environment to an extent not experienced by human societies-a 3 °C global warming, to which society may be committed by the middle of the next century, last prevailed about three million years ago. While the rate of warming will likely be moderated somewhat over the next few decades by the presence of aerosols, there has been no plausible set of changes proposed or implemented in the models that can make the warming go away.

The research program that has been initiated, which has emphasized a wide set of process studies and observations, will provide important information to help improve our understanding. To help pull all of these new results together, I believe there also needs to be accelerated modeling efforts that focus on development of Earth System models. This task can best be accomplished through expanding activities at major modeling centers where core teams of researchers can be coupled to the focused research conducted by individual scientists and small research groups. Such efforts are starting, but are not yet well funded. With such integrating efforts and with more research on environmental and economic impacts, statements concerning projected changes should become less contentious, assessments will become more complete, and the information base for considering and implementing response options will become increasingly more detailed and useful.

The dilemma that you face is that there is no doubt that the nearly 6 billion people on Earth will cause some climatic and environmental impacts and no doubt that energy and technology are essential to provision of vital services for society. It should not be surprising that these different priorities create controversy and difficulty in facing the challenge of choosing a long-term path that minimizes both the environmental impacts and the economic costs. Viewing the development of a flexible set of technological options as an economic opportunity, as some nations are starting to do, may provide a win-win situation.

Thank you.

[Attachment]

GLOBAL CLIMATE CHANGE: Overview of KNOWNS AND UNCERTAINTIES

1. Atmospheric composition is changing as a result of human activities, with carbon dioxide levels up 25% and methane concentrations having doubled since the beginning of the Industrial Revolution and the expansion of agriculture.

Strong observational evidence demonstrates that human activities are leading to increasing atmospheric concentrations of carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and chlorofluorocarbons (CFCs) and their replacements.

Although details about the deforestation source and the vegetation, soil, and oceanic sinks of CO2 are not well quantified, the largest uncertainty about future CO2 concentrations arises due to uncertainties in forecasting future energy use and technologies. There is no doubt that the concentration of CO2 will continue to increase unless future emissions are reduced by more than 60% below current levels and that the concentration of CH4 will continue to increase unless future human-induced emissions are decreased 15-20%.8 The cause of the N2O increase is less certain, but may be due to increased use of fertilizers to stimulate agricultural productivity.

The best model simulations, which are in reasonable agreement with observations, indicate that the changing concentrations of CFCs, nitrogen oxides, methane, carbon monoxide, and other gases are affecting atmospheric chemistry. Induced changes include depletion of ozone (O3) in the stratosphere (about 10-40 miles altitude) and enhancement in the troposphere in the Northern Hemisphere (below 7-10 miles altitude). In addition, the CFCs and methane exert a direct greenhouse effect. Sustaining the steady cutbacks in CFC production is essential to alleviating both ozone depletion and to prevent augmentation of greenhouse effects.

The sulfate aerosol concentration is enhanced in the Northern Hemisphere, particularly as a result of industrial and power-generating activities associated with fossil fuel combustion and the resulting sulfur dioxide (SO2) emissions. These aerosols scatter sunlight back to space and may increase cloud reflectivity. Both of these effects tend to cool the climate (or to moderate warming).

The concentration of light-scattering aerosols in near equatorial latitudes is strongly influenced by emissions from biomass burning; these aerosols may also modify cloud radiative characteristics. Like sulfate aerosols, these apparently tend to cool the climate.

2. Atmospheric composition is an important determinant of the Earth's temperature and the overall climate.

Were there no atmosphere, the Earth's temperature would be like that of the Moon, with exceedingly cold temperatures at night and very warm temperatures during the day. Working with the oceans, the Earth's atmosphere transforms the climate to the much more moderate conditions to which society has become accustomed.

Satellite and laboratory data confirm the ability of water vapor,9 CO2, CH4, CFCs, O3, and other gases to absorb infrared (heat) radiation emitted from the surface and to re-emit a significant fraction downward, creating a strong warming (greenhouse) effect at the surface. Because of the greenhouse effect, the surface receives about twice as much energy per day from downward infrared radiation as it does from incoming solar radiation.

Increases in the concentrations of these greenhouse gases will enhance the trapping of infrared radiation and its re-emission to the surface. The increased energy at the surface will lead to warming and increased evaporation of surface moisture and ocean waters. The enhanced atmospheric water vapor concentration will further enhance the trapping of infrared radiation and global warming.

Satellite data demonstrate that the ability of clouds to reflect solar radiation tends to moderate somewhat the strong trapping effect of these greenhouse gases. Small changes in cloud cover could contribute relatively large changes in radiative fluxes; such changes could be in either direction so could either amplify or moderate, but not reverse, greenhouse warming. Cloud changes are usually a result of changes in atmospheric circulation, and cloud cover does not simply increase due to increased water vapor in the atmosphere.

8 See Intergovernmental Panel on Climate Change 1990 report.

9 The water vapor concentration of the atmosphere is determined by surface temperature and atmospheric transport and removal processes. Water vapor is the largest contributor to the greenhouse trapping of infrared radiation; without the trapping of the other gases, however, its concentration would be significantly lower.

Changes in ozone concentration alter the Earth's radiative balance. The depletion in lower stratospheric ozone tends to reduce the greenhouse trapping effect, especially in high latitudes, thereby compensating for at least some of the greenhouse effect of the CFCs that contributed to the ozone depletion.

Light-colored sulfate and biogenic aerosols tend to scatter solar radiation back to space and may alter scattering characteristics or extent of clouds, generally tending to counter the trapping effect of greenhouse gases and moderating their warming effect.

Another human-induced factor that affects the climate is modification of the land surface (e.g., deforestation, agriculture, urbanization, etc.). Such effects have primarily local to regional scale effects.

3. Despite their shortcomings, computer models have many strengths and are the best tools available for understanding and projecting climatic change.

There is no comparable or fully understood geological analog of the past that would help in projecting the effects of future changes in atmospheric composition on climate; climate models provide the only viable alternative. However, paleoclimatic data do suggest that large variations in the atmospheric CO2 concentration have been associated with large variations in the Earth's climate. If the climate models are overly sensitive to greenhouse gases, then it would be difficult to explain these large changes in climate, even accounting for changes in the Earth's orbit, in the extent and heights of mountain ranges, in the position and extent of continents, and in the circulation of the oceans.

Climate models are computer-based constructs that seek to encompass our fullest practical and theoretical understanding of the climate system, taking full advantage of the most advanced supercomputers (and soon, through DOE's CHAMMP program, of massively parallel computers). Even with such resources, utilizing the fastest computers, the leading climate models divide up the globe into boxes roughly the size of the states of Colorado or Wyoming and represent the weather within the state (or in a region from San Francisco to Reno) using one value of the temperature, one value of the windspeed, and one value for precipitation. Although clearly inadequate for simulating regional climatic conditions, such models do seem to represent many important features of the global climate. Refining resolution is resource intensive: to double the spatial resolution requires about ten times more computer time.

The performance of climate models is checked using a wide variety of tests. For example, studies of critical processes under field and laboratory conditions provide important insights into the representations of atmospheric radiation, cloud interactions, etc. To carry out such verification tests, the U.S. Global Change Research Program sponsors a large number of coordinated field and modeling studies; for example, DOE's Atmospheric Radiation Measurement (ARM) program is set up to gather the needed data and to improve treatment of clouds and radiation. Tests are also made to evaluate model performance in simulating the seasonal cycle, interannual climate variations, and climatic changes evident in the geological record (e.g., ice age cycling). A series of model vs. model and model vs. data comparison efforts are underway to better understand various aspects of model performance. For example, with DOE support, scientists at LLNL are leading an international comparison of 30 atmospheric models from nine countries, 10 all attempting to simulate the decade 1979 to 1988, which exhibited large seasonal variations of drought, precipitation, etc. The results of this study and of many associated analyses of model performance should become increasingly available in 1993. However, there is no test that can fully and independently check all aspects of the models, so there can and will always be criticisms that the models remain incomplete. Deciding when verification will be sufficient is therefore a very difficult and controversial question.

When model results for the present climate are compared to observations, the climate models generally do well at simulating large-scale climatic features, particularly during the winter season. The models do less well at simulating the summer season, especially the surface temperatures and the amount and distribution of precipitation. Unfortunately, it is usually regional, summertime climates where rainfall is most important that are of greatest importance in estimating agricultural and ecological impacts.

There has been only limited coupling of atmospheric and oceanic models, and virtually no accounting of the interactions between the climate and the biosphere. This

10 The DOE-sponsored Program for Climate Model Diagnosis and Intercomparison (PCMDI) project includes groups from 30 countries: U.S. (15, although some are variants of the same model), Australia (2), Canada (1), China (1), France (2), Germany (1), Japan (2), Russia (3), United Kingdom (2), and European Center for Medium-Range Weather Forecasts (1).