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riods of cooling in the steady rise. There is, however, no basis to suspect that increasing greenhouse gas concentrations can lead to a long-term cooling.

Predicting the future evolution of the climate is a several part problem: (1) what will be the changes in emissions and other aspects of human activities (these changes depend on societal and technological forecasting); (2) what will be the changes in atmospheric composition; in other natural forcing factors (volcanic eruptions, etc.), and in climate (these changes depend mainly on physics and chemistry); and (3) how will natural and human systems respond to affect emissions and other boundary conditions affecting the atmosphere (these feedbacks have both biological and political aspects). With respect to our capabilities for prediction, the accuracy of societal and technological forecasting decreases rapidly as we extend into the future; the useful accuracy of our ability to predict climatic change, however, is best at intermediate to long times (several decades and beyond), even though the accuracy of our understanding of feedbacks is quite limited. Thus, we likely have some predictive skill for intermediate periods (e.g., temperature change of 1-3 °C middle of the next century) on large scales (e.g., global) assuming business-as-usual. Research will improve our skill to make more regionally resolved and time-resolved forecasts (e.g., via DOE'S CHAMMP, ARM, and PCMDI programs) and to test various scenarios of future possibilities, but precise prediction-as opposed to general projection-will remain very problematic.

The climatic response to emissions starts immediately, but can take time to be detected in the observational record depending on its relative magnitude. Very strong volcanic eruptions show their effects in several months to a year because they are so large; because the greenhouse gas increase is small each year, but cumulative, it has taken about a century for it to start to become evident (especially because other human activities are likely helping to, at least temporarily, hide its influence).

In the absence of other factors, once they are emitted, greenhouse gases commit the Earth to some change. At present, the greenhouse gas emissions each decade are projected to be committing the Earth to a warming of at least 0.1 °C, and perhaps as much as 0.3 °C or more; with increasing emissions, this rate of commitment is rising slowly, but steadily. For perspective the global temperature change from glacial to interglacial conditions was roughly 3-5 C°, so the present commitment is about 5% of that change per decade.

Question 3. Some say that we should wait for greater certainty in the science of global climate change before taking steps to mitigate emissions. Will we ever have perfect knowledge on the rate and timing of global climate change? What should be done to reduce uncertainties and how long will it take?

Scientific research will lead to increasing confidence in projections of how future climate will respond to projected changes in emissions. We will never have absolute certainty, however, in that all we can do is improve our models by testing them against a wider and tougher range of case studies. There is not, however, any comparable situation to what is occurring, and there is no way to conduct a comprehensive global-scale experiment in a laboratory, so there will always be limitations in what we can know about the future. An important task of DOE's CHAMMP program is to identify the limits to predictability that we can expect to approach.

The US Global Change Research Program is seeking aggressively to reduce uncertainties as a means of reducing the polarization over the issue.

(1) The largest uncertainties concerning the forcing of future climatic change involve limitations in our understanding of the carbon budget and stratospheric ozone change. While the latter issue is being dealt with, greater emphasis on the role of terrestrial ecosystems is needed to resolve the carbon balance.

(2) The largest uncertainty concerning the magnitude of climatic change is due to uncertainties about cloud-radiation interactions. To improve estimates, programs (including especially DOE's ARM program) are focused on this issue.

(3) The largest uncertainty concerning the rate of climatic change is due to treatment of the oceans. The WOCE and TOGA programs as well as modeling programs are underway to improve treatment of the oceans.

(4) The largest uncertainty in the regional pattern of climatic change likely arises from the poor spatial resolution of the models. DOE's CHAMMP program, for example, is underway to apply massively parallel computers to permit increased resolution.

(5) The largest uncertainty concerning detection of climatic change likely involves aerosols from sulfur dioxide emissions and biomass burning. New programs focused on aerosols are being developed. A new DOE program is proposed to look at the detection issue.

(6) The most important limitation in placing confidence in the models is the lack of systematic testing of the models and shortcomings in the data to test the models. DOE's PCMDI has enlisted almost 30 modeling groups from around the world in a series of common test runs and analyses and is assembling data sets against which to better compare models. Internationally, plans are also being developed for an improved global observing system to provide needed data.

(7) The most important limitation in estimating the importance of the problem is caused by the low level of support for ecosystem and impact studies. More effort is needed (see May 5 testimony to House of Representatives by R. VanHook of ORNL). There is no easy cure to improving our understanding. It will take concerted effort that continually focuses attention on the most important causes of uncertainty (an important rationale for new program development and expansion being used by DOE). The NIGEC centers could also play an important role by focusing on regional impact assessments.

It will also take an increasing effort to synthesize and intercompare results from different programs, an effort that is lagging in the U.S. An important step would be greater emphasis on development and testing of Earth System models at a few modeling centers or laboratories in the U.S., with each reaching out extensively to include and collaborate with the many focused research programs now underway. Question 4. Is there a correlation between sunspot cycles and the Earth's temperatures? If such a correlation exists, would that negate the theory relating CO2 emissions to global climate change?

The Sun's energy drives the climate, so variations in solar activity should affect the climate. There have been attempts for several hundred years to correlate sunspot activity with climatic change. There has been significant difficulty with such relationships because, until the last ten years, there have been no satellite measurements relating the solar energy output (which drives the climate) to sunspots. Satellite measurements now indicate that solar energy variations with the sunspot cycle are quite small compared to the energy variations caused by the increases in concentration of greenhouse gases. Thus, while there should be a sunspot-climate variation (and it is a variation rather than a change in that there is not thought to be a significant and persistent trend over the last millennium), it should be smaller than the enhancement of the greenhouse effect.

The recent suggestion that the interval between sunspot cycle peaks is nearly perfectly correlated to the temperature trend is thus quantitatively and mechanistically unacceptable because it postulates a large response to a relatively small forcing (solar variation) and a non existent response to a larger forcing (greenhouse gases). In addition, the solar effect postulated occurs instantaneously, which is not how the climate is thought to respond (nor how it does respond to volcanic eruptions). If the sunspot hypothesis were current, it also becomes very difficult to understand why past climates, on average, have changed at all. If the climate were indeed as sensitive to the solar forcing as the authors suggest, then the greenhouse effect must be taken even more seriously than current models suggest.

Question 5. Climate models differ in their predictions of regional and global temperature changes. What accounts for these discrepancies in the model's findings? What level of confidence do we have in our findings?

The DOE Program in Climate Model Diagnosis and Intercomparison (PCMDI) project has launched an intensive international model intercomparison study to address this question. Part of the difference occurs because, with computational resources less than what are really needed by a factor of at least a million, different modeling groups make different approximations to representing the climate given the computational resources that they have. By promoting use of massively parallel computers, DOE's CHAMMP program is trying to reduce the need for making such drastic compromises in representing climate system processes.

A second problem is limitations in our understanding of critical processes. The most important uncertainties arise from lack of adequate understanding about cloud processes and interaction with atmospheric radiation. Other critical aspects concern representation of the land surface and ocean circulation.

It is also important to realize that models do many things quite well, especially the newest models that have finer spatial resolution. Some of the differences that the media highlights arise from comparing new models (which tend to agree better with each other) with older models (which tended to disagree more with each other). An intense effort is underway as part of DOE's PCMDI program to standardize testing and to compare model simulations against observations for the period 1979 to 1988.

In spite of model shortcomings (on which scientists actually tend to focus their attention), combining understanding from studies of recent and paleo-climates and

from modeling, there are important predictions related to the enhanced greenhouse effect in which we can place varying degrees of confidence (these results are drawn in part from a listing by Dr. Jerry Mahlman, NOAA/GFDL):

Certain: Greenhouse gas concentrations are rising and these gases are affecting the infrared radiation balance by increased absorption and re-emission. Virtually certain (no credible alternative): The change in the infrared radiation balance will lead to (and is leading to) large stratospheric cooling.

Very probable (9 out of 10 chance): Global warming will be in the range of a few degrees for a CO2 doubling. Associated with this warming will be an increase in global precipitation, a reduction in polar sea ice, and intensified warming during the Arctic cold season. There will be a continuing rise in sea level at at least the current rate of 1-2 cm/decade (about half inch per decade). Probable (2 out of 3 chance): An increase in precipitation in the Arctic and drying of midlatitude continental areas in summer. Moderated warming in low latitudes.

Uncertain (hypothesized, but insufficient evidence): Regional climatic changes greater than the global change, regional precipitation increases and decreases, an increase in tropical storms, regional changes in vegetation. Also uncertain is the warming (or even occasional cooling) rate for the next few decades. Question 6. What are the feedback effects of clouds, oceans, ecosystems, and the polar ice caps? Are these feedback mechanisms likely to slow or accelerate global climate change?

The climate includes a wide possibility of interacting processes that can either amplify (positive feedbacks) or moderate (negative feedbacks) the direct radiative (warming) effects of the increase in CO2 and greenhouse gas concentrations. Present understanding is as follows:

(1) Clouds: The cloud effect is quite complex, depending on cloud type, season, latitude, etc. It appears likely that clouds create an amplifying effect (positive feedback) in most regions, but a neutral or moderating effect (negative feedback) in low latitudes.

(2) Oceans: Oceans tend to moderate the rate at which the climate will respond, but probably do not have much influence on the magnitude of the change. Because the ocean circulation may change, however, oceans do introduce the potential for surprises.

(3) Ecosystems: There are many interactions involving biological systems, and the net effect is uncertain. The biosphere may take up carbon at an increasing rate, moderating the effect for at least some period. Warming of permafrost regions may lead to increased release of methane from peat decomposition, which would amplify the warming. There are many other possibilities.

(4) Polar ice caps (Greenland and Antarctica): The ice caps tend to moderate the rate of climatic change. Warming over Greenland may accelerate melting and sea level rise, but the rise may be delayed for decades to centuries by refreezing of the meltwater in the ice. Warming over Antarctica may actually lead to increased snow accumulation and, for at least some decades or even longer, moderate the rate of increase of sea level.

(5) Sea ice: The global scale climatic effect of the melting of sea ice is likely quite small, but the local effect can be quite large, restricting the intense near-surface atmospheric cooling that occurs when sea ice forms in fall or winter. Delayed freezing of the Arctic would likely allow increased precipitation over adjacent land areas, even increasing winter snowfall, but it is likely that, with warmer temperatures, the additional snowfall it would melt away each summer (although this is not certain). Earlier melting of the sea ice each spring would provide more moisture for low stratus clouds, which may compensate for the lower surface albedo due to the sea ice melting.

(6) Snow cover on land: With warming, it is likely that snow cover will melt back earlier in spring, allowing increased solar absorption (except where clouds increase) and probably cause earlier drying of mid-continental regions, allowing an increase in summer temperatures. As for sea ice, the effect will be more regional than global.

RESPONSE OF MICHAEL C. MACCRACKEN TO SENATOR DOMENICI'S QUESTION ABOUT

BUDGET PRIORITIES

I want to emphasize at the outset that these opinions are my own and not those of DOE, the Lawrence Livermore National Laboratory, or the University of California. Understanding the coupled climate-environment system is arguably the most complex scientific challenge facing society, made so in large part because there is no

parallel system that can be tested in a laboratory. The system also affects us all, and all of us have experience with it, making it essential that scientists must not only understand the system, but also must be able to explain all essential aspects of the system to the public. At the same time, vital societal activities are changing the system, necessitating that results be provided with some reasonable certainty.

To improve understanding of the system, it is vital that there be a broad-based, well financed program that includes, as does the U.S. Global Change Research Program (USGCRP) components including processes (to better understand how specific aspects of the system work), monitoring and observations (to document how the system is working), modeling (to incorporate scientific understanding and to be able to project future conditions), and assessments (to provide an integrated perspective). There is thus much to be done, even without getting into areas of impacts and resource analysis.

The Department of Energy program began in the late-1970s, and it is the aspect of the USGCRP with which I am most familiar and on which I feel qualified to comment. Over this entire period, their program has attempted to focus on working to resolve the most important uncertainties, particularly those for which their style of a combined and focused laboratory-university research program is best suited. The DOE global change research program has been strengthened the past several years with new programs, all but NIGEC being thoroughly and regularly reviewed and drawing on both laboratory and university participation. I will comment on six aspects of the DOE program, including NIGEC.

(1) The Atmospheric Radiation Measurement (ARM) program is DOE's largest program. ARM focuses on the role of clouds in trapping and reflecting radiation, widely recognized as the most important contributor to amplifying or moderating the magnitude of climatic change induced by the greenhouse gases alone. The USGCRP lists the uncertainty in cloud-radiation interactions as the most important uncertainty to resolve. The ARM program is critical to gathering and interpreting the data needed to determine whether the warming the next century will be modest or quite sizable. The program has just opened its first field site in the midwestern U.S.; this will be an important test area and, with increasing funding, will lay the groundwork for sites in other critical areas (e.g., the tropical Pacific) over the next few years. Cutbacks in ARM would be disastrous.

(2) The Computer Hardware, Advanced Mathematics, and Model Physics (CHAMMP) program is adapting and redesigning climate models for use on the new massively parallel computer architectures being encouraged by the High Performance Computing and Communications Program (HPCCP). The goals are an increase in effective model speed by a factor of ten thousand over ten years and to understand the spatial and temporal limits of climate predictability. It is only with such an advance that we will be able to approach making regional climate projections. Growth of this program has been significant on a percentage basis, but the actual model transfer component of the program (the real workhorse part of the project) still supports fewer than ten physicists and computation scientists spread across four of the DOE laboratories (ANL, LANL, LLNL, ORNL). Continued growth in this program is essential.

(3) There are several very important components of the DOE Core Program. Model intercomparison studies in the mid-1980s first raised the issue of the disagreements among models; it is by resolving these disagreements that progress is being made. The Program for Climate Model Diagnosis and Intercomparison (PCMDI), based at LLNL, is running two important international model comparison studies. One, involving about 30 groups from around the world is evaluating how well models simulate the observed changes during the period 1979 to 1988; this is a vital check of the accuracy of model simulations. The second comparison, involving about 20 of the groups, is looking at the modeling of climate feedbacks (and was the project that pointed to the need for the ARM program). On the agenda for the future are comparisons of ocean models and coupled ocean-atmosphere models. This project merits increasing support.

Other important aspects of the Core Program include study of the carbon cycle, including an ocean carbon survey to help better understand where the missing quarter of the emitted carbon dioxide is going, an information and analysis center to provide an interface to the public, and study of the response of vegetation to increased carbon dioxide (which is generally positive where nutrients and water are not limiting). These programs all need and deserve some growth.

Due to requirements to divert funds to NIGEC (see below), a proposed component of the core program focusing on analysis of impacts on societal resources (e.g., water, coastal wetlands, etc.) had to be drastically cut back a few years ago. Not having a program understanding the societal importance of the climate changes is

an important gap in the DOE program and a weakpoint in the U.S. program. Analysis of impacts is not easy, but DOE had, after ten years effort, finally figured out a workable approach—the Congressional redirecting of funds for NIGEC essentially killed it.

(4) Several new programs are proposed for start-up. To augment in situ and remote measurements at the ARM surface sites, development of UAVs (unmanned aerospace vehicles) and an ARMsat (small satellite) would lead relatively quickly to platforms that could make measurements at the tropopause and in space that are critical to understanding cloud-radiation interactions. NASA is reportedly going to look more intensely at small satellites already an indication of the importance and success of the planning initiatives in this area over the past 18 months by DOE and its laboratories. The key question for ARMsat is whether DOE's budget can handle this new initiative. UAVs capable of extended flights are on the drawing boards, and a modest DOE program is proposed and could pay important dividends.

Planning has also been initiated for a modeling and observation program aimed at providing definitive detection of the greenhouse component of climate change. This program would seek the greenhouse "fingerprint" in a combined data and modeling program. Like the other programs, the intent of this new effort is to focus intensely on a major uncertainty not being adequately addressed by any other USGCRP program.

(5) DOE's educational initiative in the greenhouse area includes support for graduate and postdoctoral fellows and for development of curriculum materials for grades K to 12. The fellows program allows the awardees to undertake their research at qualified universities and laboratories of all agencies (a distinction of the DOE program as compared to NSF). This new program is quickly becoming an important source of highly qualified young scientists.

High school curriculum materials developed and tested in classrooms are now being disseminated to other teachers through workshops led by the mentor teachers who developed the program. Materials for lower grade levels are now in the testing stage. The teachers have developed a cross-disciplinary and cross-grade level curriculum, which is at least as hard to accomplish at the high school as at the college level-yet they are being very warmly received as teachers perspectives are being broadened. These efforts deserve increasing support, both to train future scientists and to educate the youth of our nation.

(6) The National Institute for Global Environmental Change (NIGEC) has been growing at Congressional behest, unfortunately generally at the expense of the very high priority DOE programs mentioned above. Aside from the severe financial implications, it is important to recognize that NIGEC is not a good fit within DOE, being a program virtually exclusively university based and not being under the technical control of DOE. What has been set up are six funding centers having, in some respects overlapping scientific objectives and very little central effort to integrate the activities into a cohesive whole (as is done for all of DOE's other programs). There is no clear scientific rationale for having regional centers when most of the issues being investigated have global implications (and are generally within NSF's scientific areas). All of the funding decisions are made at the local level, such that even NSF has greater control over the projects it funds.

A conceivable rationale for regional centers would be to look at regional impacts of climate change (e.g., the southeastern center looking at the effects of sea level rise along the Gulf coast, or impacts on the pine plantations, etc.), but such research has been only a minor focus. While at least a reasonable percentage of the projects are of useful quality, if they could qualify, NSF would be a better avenue for comparing and coordinating university projects with global implications (e.g., methane emissions from rice paddies, etc.). I believe it is quite counterproductive to reduce funding to the focused DOE global change research programs (which all fund university programs, but in a better focused way) in order to increment NIGEC. If for political reasons DOE must support a set of regional centers, I would urge shifting of their focus to regional impact issues and possibly associating each of the centers with a DOE laboratory to help assure a tighter focus to the DOE mission.

With respect to the national global change program, I want to offer a final comment on the overall USGCRP. To gain CEES and Congressional support, it seems that a never-ending set of new programs must be established, all with new names. This has led to considerable fractionation of the efforts, rather than to strengthening of the overall program by increasing funding for the already on-going programs. As a consequence, every scientist is spending more and more time writing more and more proposals to more and more new programs; everyone's nerves are becoming more frazzled and less time is being devoted to actually doing science. In addition, achieving critical mass is becoming harder and harder, requiring combinations of

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