Global Warming: Significant Shortcomings of Computer Climate Models

31 ELR 10432 | Environmental Law Reporter | copyright © 2001 | All rights reserved

31 ELR 10432 | Environmental Law Reporter | copyright © 2001 | All rights reserved

Global Warming: Significant Shortcomings of Computer Climate Models
Robert C. Barnard and Donald L. Morgan
Robert C. Barnard is Of Counsel to, and Donald L. Morgan is Senior Partner in, the Washington, D.C., law firm Cleary, Gottlieb, Steen & Hamilton.

[31 ELR 10432]

The 1997 Kyoto Protocol provides for a 5% reduction in 1990 levels of greenhouse gases by 2008-2012 in order to stem global warming. The developed nations have agreed to specific greenhouse gas reduction levels; the U.S. quota reduction is 7%.¹ The Kyoto Protocol also provides broad objectives, the details of which are to be worked by the Conference of the Parties.

Computer climate models are used to develop forecasts of future climate changes in order to provide a basis to assess impacts of climate changes and to devise mitigation of, or adjustment to, such changes. Thus, computer climate models must be reliable and accurate if we are to plan intelligently and responsibly for our world's future. Unfortunately, current climate models are inadequate. Two recent major reports, although drafts for external review, provide insight on the shortcomings of existing climate models.

The first draft report, Third Assessment Report by the Intergovernmental Panel on Climate Change (Draft Third IPCC Report),² was prepared by the Intergovernmental Panel on Climate Change (IPCC), which is the designated science advisor to the Parties to the Kyoto Protocol. The second, U.S. National Assessment: The Potential Consequences of Climate Variability and Change (Draft USGCRP Report),³ was prepared under the auspices of the U.S. Global Climate Research Program (USGCRP) by a committee chartered under the Federal Advisory Committee Act, the "National Assessment on Climate Change Synthesis Team." Both reports acknowledge that uncertainties and gaps exist in the current scientific global climate information. Neither report uses climate models to project the levels of greenhouse gases in 2100. In both cases the projected levels of greenhouse gases in 2100 are derived from estimates in the "literature" that are compiled into what are referred to as "scenarios." The scenarios reflect an increase in the levels of greenhouse gases—carbon dioxide (CO₂), for example, is projected to be at least doubled. Climate models are used to analyze the scenarios and to calculate the increase in temperature on the scenario-assumed greenhouse gas levels in 2100.

The Draft Third IPCC Report uses six scenarios and models. The scenarios are based on a division of the world into four regions, so there is virtually no spatial or regional detail. Based on this methodology, the report calculates an increase in global temperature in 2100 as 1 degree Celsius (° C) to 4.5° C and an increase in air temperature from 1° C to 5° C.

The Draft GCRP Report uses an IPCC scenario and two models. The report relates to the United States and reflects some regional studies. Consequently, the report provides more spatial detail. The two models reflect differences in the way in which the climate forcing factors are incorporated. One model projects a damp climate and an increase in temperature of 1° C. The second projects a dry climate and a temperature increase of 4° C.

Both reports agree that the climate models have important shortcomings. This Dialogue is being written to urge that the Conference of Parties take into account the impact of the uncertainties due to the shortcomings—biases—in the models from the way the climate forcing factors are incorporated and the uncertainties from the methodology using scenario-assumed levels of greenhouse gases in 2100 to derive the estimates of projected temperature increases.

We urge that the Conference of the Parties should consider the important shortcomings of the current computer climate models and consider appropriate action to support development of more satisfactory models. We advocate development of climate models that will incorporate all information on land, sea, and air and will provide a sound scientific basis for more reliable predictions of future change in the climate, sometimes referred to as prognostic "coupled general circulation" models.

The Kyoto Protocol Provides a Mechanism for Upgrading of Current Climate Models

The Parties to the 1997 Kyoto Protocol agreed to cut emissions of greenhouse gases—principally CO₂—5% below 1990 levels. The 39 Annex B countries, which include all the major developed nations, agreed to specific cuts; the United States agreed to a cut of 7% below the 1990 level.⁴ The details of these general agreements are to be worked out by a Conference of the Parties under Article 9 of the Kyoto Protocol, which provides that the Conference of the Parties shall periodically review the Kyoto Protocol "in the light of [31 ELR 10433] the best available scientific information and assessment of climate change and its impacts as well as relevant technical, social and economic information…. Based on those reviews, the Conference of the Parties … shall take appropriate action."

For example, for the November 2000 Conference of the Parties (COP-6), the United States proposed detailed procedures for evaluating carbon sequestration sinks from the improved management of land use, land use change, and forests to be applied as credit against the quota reduction. The U.S. presentation included a decision text proposed for adoption by the Conference of the Parties.⁵ Carbon sinks are climate forcing factors that should be included in climate models.

Background: The National Academy of Sciences Report

The importance of developing scientifically sound global climate models was a critical recommendation of the National Academy of Sciences' (NAS') 1999 review of state-of-the-art climate science (NAS Report).⁶ The 595-page report was prepared by two distinguished panels: The Committee on Global Change, and the Board on Sustainable Development Policy Division of the National Research Council. The report reviewed climate research in the past decade. Based on that review, the NAS Report recommended a 10-year comprehensive research program to provide a sound basis for assessing the causes of climate change, as well as the development of sound mitigation science so "that mitigation measures [address] the underlying causes."⁷

The NAS Report was prepared pursuant to the designation of the NAS as the official scientific advisor to the U.S. Global Research Program by the Global Change Research Act of 1990.

The NAS Report acknowledges that modest achievements in predicting changes in climate have been made:

We have begun to make considerable progress in characterizing patterns of climate variability, with one notable accomplishment being the prediction of the most recent El Nino event well in advance of its greatest impacts. And, although on a very limited basis, we have begun to investigate the possible impact of various climate change scenarios on terrestrial systems by using global models of those systems.⁸

The NAS Report, however, also stresses the importance of developing more reliable computer climate models:

The possibility of major changes in the global environment due to human influence presents a difficult challenge to the research community: to relate causes and effects and to project the course of changes on a global scale and for many decades. Approaches based purely on observations are inadequate for predictions …. We, therefore, need models—numerical representations of the Earth system—to express our understanding of the many components of the system, how they interact, how they respond to perturbations, and how they feed back to provide dynamical controls on overall system behavior. It is thus evident that the study of global environmental changes—their causes, their impacts, and strategies for mitigation—inescapably requires models that encompass the mutual interactions of the principal components of the Earth system.⁹

The NAS Report concludes that "such models are in rudimentary form today."¹⁰

The NAS Report also sets forth detailed recommendations for global climate models that meet the needs of policy and decisionmaking. The report's "Modeling" chapter contains careful analysis of the data that should be incorporated in the model and the characteristics and form of the necessary improvements in current models.¹¹ It is not possible to summarize briefly the detail and scope of the recommended improvements. However, an indication of the detailed recommendations is provided by the following "Summary":

As the USGCRP is preparing to enter its second decade, the integrative phase, the strategy for the coming decade must establish techniques for coupling and integration of physical, biogeochemical, and the human dimension subsystem models in preparation for the construction of integrated prognostic Earth system models. The strategy should include four aspects, each of which will contribute to an overall objective of developing the prognostic modeling capacity essential to the needs of the USGCRP. These aspects are at different levels of organization: the first is at the component level where work, though advanced, is still required. The second level is at the subsystem level and focuses on the issues of boundary compatibility across key interfaces highlighted in this chapter. This will require modeling workshops involving intercomparisons of like subsystem models and intercomparisons involving coupling between adjacent subsystem models (which must match boundary conditions and fluxes). Issues of the adequacy of data for testing a rejection will be third level focuses on simple Earth system models, wherein models are compared to highlight differences in coupling techniques, interelement fluxes across key boundaries, and sensitivity studies to reveal the differences between models and the relative importance of individual system parameters. It sets the stage for the fourth level, which will be at the Earth system science level with richly developed components. Here the challenges will be significant.

This chapter focuses on level two: subsystem integration and linkage. Subsystem integration involves at least four key linkages: land-atmosphere, land-ocean, ocean-atmosphere, and atmospheric physics with atmospheric chemistry. In addition to this complexity, there is the essential component of the human dimension to global environmental change.¹²

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It is significant that the USGCRP, in its October 1999 report to Congress, referred to the NAS Report and announced its intention to develop a decade-long comprehensive research program in consultation with the NAS. The program included the development of improved climate models.¹³ No specific progress has been published.

The Draft Third IPCC Report

Terminology

It is helpful to clarify terminology in order to understand the comments in the Draft Third IPCC Report relating to possible human impact on the climate. The report distinguishes the terms "detection" and "attribution" of a climate change:

Detection is the process of demonstrating that an observed change is significantly different (in a statistical sense) than can be explained by natural variability. Attribution is the process of establishing cause and effect, including assessment of competing hypotheses…. Detection studies demonstrate whether or not an observed change is highly unusual in a statistical sense, but does not necessarily mean that we understand its causes. The attribution of climate change to anthropogenic causes involves statistical analysis and careful assessment of multiple line of evidence ….¹⁴

The distinction is important because the terms used determine how findings relating to human effects on the environment are characterized by the IPCC. The distinction between "detection" and "attribution" distinguishes statistical association "detection" from cause "attribution."

Thus it is important to note that the Draft Third IPCC Report concludes that there has been a "discernable human influence" on global climate. The term "attribution" is not used:

From the body of evidence since IPCC (1996) we conclude that there has been a discernable human influence on global climate. Studies are beginning to separate the contribution to observed climate change attributable to individual influences, both anthropogenic and natural. This work suggests that anthropogenic greenhouse gases are a substantial contributor to observed warning over the past 30 years. However the accuracy of these estimates continues to be limited by uncertainties in estimates of internal variability, natural and anthropogenic forcing, and the climate response to external forcing.¹⁵

The Draft Third IPCC Report does not attempt to quantify "discernable human influence," and it falls short of a finding of attribution or cause.

Models and SRES Scenarios

The concept of "long-term emission scenarios," as referred to by the IPCC, was originally developed by the IPCC for its first reports in 1990 and 1992. In 1995 these scenarios were evaluated, and in 1996, due to significant changes in understanding of the driving forces of emissions, the IPCC decided to develop a new set of scenarios. The result is a February 18, 2000, report, Summary for Policymakers: Special Report on Emission Scenarios, referred to as the SRES Report, prepared as a Special Report of Working Group III of the IPCC.

"Future greenhouse gas (GHG) emissions are the product of very complex dynamic systems, determined by driving forces such as demographic development, socio-economic development, and technological change. The future evolution is highly uncertain."¹⁶ Thus, in 1990 and 1992, a "set of scenarios was developed to represent the range of driving forces in the scenario literature so as to reflect current understanding about underlying uncertainties."¹⁷ "Scenarios are alternate images of how the future might unfold and are an appropriate tool with which to analyze how driving forces may influence emission outcomes and to assess the associated uncertainties…. [Nevertheless,] the possibility that any single emission path will occur as described in scenarios is highly uncertain."¹⁸

Two characteristics of the new emission scenarios stand out. First, in the new scenarios, emissions were "provided aggregated into four world regions and global totals." There were no regional or spatial details. In addition, "no feedback effects of future climate change on emissions from biosphere and energy" were assumed.¹⁹ Second, an argument has been made that one important effect of global warming would be coastal flooding as a result of a potential 4 to 6 meter rise in ocean levels from the melting of the West Antarctic Ice Sheet. The Draft IPCC Third Report concludes: "The majority view is now that a major loss of grounded ice and associated sea level rise is unlikely during the 21st century."²⁰ The report also concludes that the decay period for the Greenland Ice Sheet would take more than 1,000 years.²¹ Yet the potential threat of coastal and island flooding from deglaciation of the West Antarctic Ice Sheet and the Greenland Ice Sheet was not discussed in the SRES Report.

The SRES Report consists of 40 different "scenarios" with 4 different "story lines" (referred to as "families") that were developed by 6 IPCC Working Group teams:

Four different narrative storylines were developed to describe consistently the relationship between emission driving forces and their evolution and add context for the scenario quantification. Each story line represents different demographic, social, economic, technological and environmental developments, which may be viewed positively by some people and negatively by others.²²

The range of the selected numbers used in the scenarios is illustrated by the fact that total carbon emissions from all sources in each scenario varied from "approximately 770 GTC [Gigatonnes of Carbon] to approximately 2,540 GTC."²³ The lower figure assumed a doubling of CO₂ in the [31 ELR 10435] atmosphere. Global population figures varied from 8.7 billion in 2050 and declining toward 7 billion in 2100, to 15 billion in 2100.²⁴ Other numbers showed similar broad variations:

There is no single most likely, "central" or "best guess" scenario, either with respect to SRES scenarios or to the underlying scenario literature. Probabilities or likelihood are not assigned to individual SRES scenarios. None of the SRES scenarios represents an estimate of a central tendency for all driving forces or emissions, such as mean or median, and none should be interpreted as such. The distribution of scenarios provides a useful context for understanding the relative position of a scenario but does not represent the likelihood of its occurrence.²⁵

A set of six "representations" or "marker" scenarios were selected by the Working Group to illustrate all scenario groups: one from each "family" plus two additional ones that were selected by the Working Group as "representative." The Working Group used different models to analyze the six representative scenarios.

Based on these six scenarios and the different models used, the Draft Third IPCC Report estimated increases in the global-ocean-atmospheric temperature from 1990 to 2100 to be about 2.5° C, with a range of 1.5° C to 4.5° C.²⁶ The estimated surface air temperature increase ranged from about 1° C to 5° C.²⁷

Uncertain Models, Uncertain Results

The Draft Third IPCC Report comments:

By the end of the next century, the range in projected temperatures due to differences in SRES emission scenarios is similar to that due to the uncertainties in the models. Further uncertainties arise due to uncertainties in the relative forcing, notably that due to anthropogenic aerosols.²⁸

A section of the report discusses existing models and their limitations and the results of the SRES Report²⁹:

There is a strong need for improved understanding, and representation in models of the non-linear processes in the atmosphere, land and oceans. Among these important non-linear processes are the roles of aerosols and clouds, the thermohaline circulation and sea ice. There are other broad non-linear components, such as the biogeochemical system and, in particular, the carbon system, the hydrological cycle, and the chemistry of the atmosphere.³⁰

The report specifically comments: "As has been the case since IPCC (1990), probably the greatest uncertainty in the future projections of climate arises from clouds and their interaction with radiation."³¹ The 1999 NAS Report, cited above, agrees. "The importance of clouds is best summarized by the recent Working Group 1 report of the IPCC: The single largest uncertainty in determining climate sensitivity to either natural or anthropogenic changes are clouds and their effects on radiation and their role in the hydrological cycle."³²

A revised summary of the Draft Third IPCC Report is reported to be circulating to the Parties for comment. The final approximately 1,000-page report is expected to be released to the public in the spring. A reporter for the New York Times who has seen the revised summary states that the expected increase in the temperature in 2100 has risen somewhat because of a projected reduction in sulfur dioxide and the consequent reduction in cooling sulfate aerosols. Also, a rise in ocean levels will continue due to thermal expansion even if CO₂ emissions are reduced. The summary is reported to express the need for further research.³³

The Draft USGCRP Report

Unlike the Draft Third IPCC Report, the Draft USGCRP Report addresses potential consequences in the United States from climate changes. It also presents an overview of a number of regional studies. The report, however, has limited coverage: water, agriculture, human health, coastal areas, and marine resources. It does not cover energy, transportation, urban areas, or wildlife. Two primary computer climate models are used in the report; both analyze an IPCC 2100 "business as usual" scenario with an increase in greenhouse gases including a 1% per year increase in CO₂ and growing sulfur emissions.³⁴ The report emphasizes that such assumptions are not predictions:

State-of-the-art climate models have been used to generate climate change scenarios. These scenarios are not predictions of the future. Rather, they are plausible quantitative representations of climate change over the next century…. Climate models have uncertainties but are the best tools available for thinking systematically about climate change."³⁵

The report also points out that alternative models dealing with the same facts offer differing estimates depending on how the climate forcing factors are incorporated into the model. The two primary models, the report states, produce a four-fold range in the projected temperature increase in the next century: 1° C and 4° C.

While the physical principles driving these models are similar, they differ in how they represent the effects of some important processes. Therefore, the two primary models paint different views of the future. On average over the [United States], the Hadley Model projects a much wetter climate than does the Canadian Model, while the Canadian Model projects a greater increase in temperature than does the Hadley Model. Both models are plausible, given the current understanding. By using these two models, a plausible range of future climate change is captured, with one model being near the lower end and the other near the upper end of projected temperature changes over the [United States]. In all climate [31 ELR 10436] models, increases in temperature for the [United States] are significantly higher than the global average temperature increase.³⁶

There is no definite date for the publication of the Final GCRP Report. Litigation has been filed seeking to enjoin the publication of the final report, alleging that the Draft USGCRP Report was prepared in violation of the Federal Advisory Committee Act.³⁷ At the time this Dialogue was written, no resolution of the litigation has been announced.

Comment and Outlook

Both the IPCC and the GCRP calculate possible temperature change based on models and scenario assumptions. The calculated temperature increases do not reflect the uncertainties involved in the calculated values and, as the Draft USGCRP Report states, should not be regarded as "predictions."

We refer briefly to comments by climate modelers on the shortcomings of existing models and the nature of improvements in data and in models that are required to provide sounder scientific estimates of probable climate change.

Two recent articles illustrate the views of model experts regarding the shortcomings of current models used by the IPCC and the USGCRP. First, a review article in Science by Richard Kerr, a Science reporter who focuses on global warming issues, offers the following appraisal of computer results:

Even the best models today can say little that's reliable about climate change at the regional level, never mind at the scale of a congressional district. Their picture of future climate is fuzzy—they might lump together San Francisco and Los Angeles because the models have such coarse geographic resolution—and the realism of such meteorological phenomena as clouds and precipitation is compromised by the inevitable simplifications of simulating the world in a computer.³⁸

The Kerr article quotes model experts on the shortcoming of the spatial resolution by computer models:

"For the most part, these sorts of models give a warming," says modeler Filippo Giorgi, "but they tend to give very different predictions, especially at the regional level, and there's no way to say one should be believed over another." Giorgi and his colleague Raquel Francisco of the Abdus Salam International Center for Theoretical Physics in Trieste, Italy, recently evaluated the uncertainties in [5] coupled climate models—including the [2] used in the national assessment—within 23 regions, the continental United States comprising roughly [3] regions. Giorgi concludes that as the scale of prediction shrinks, reliability drops until for small regions "the model data are not believable at all."

Add in uncertainties external to the models, such as population and economic growth rates, says modeler Jerry D. Mahlman, director of [the National Oceanic and Atmospheric Administration's] Geophysical Fluid Dynamics Laboratory in Princeton, New Jersey, and the details of future climate recede toward unintelligibility. Some people in Congress and the policy community had "almost silly expectations there would be enormously useful, small-scale specifics, if you just got the right model. But the right modeldoesn't exist," says Mahlman.³⁹

The second is an article by Hartmut A. Grassi, a model expert in the well regarded Max Plank Institute for Meteorology in Germany.⁴⁰ Grassi criticizes the simplified scenarios, such as the USGCRP's assumption of a 1% annual increase of CO₂.⁴¹ Grassi comments that despite major glaciations, an earth without continental ice sheets, a sun with increasing luminosity, and a five-fold variation in CO₂ concentration, the mean surface temperature has remained in comparatively narrow bounds of about plus or minus 5° C as compared to the current mean. He adds, "we need to understand the negative feedback that stabilizes climate and thus keeps Earth a living planet."

After careful review of the requirements for improvement of coupled general circulation models to integrate the information from atmospheric, land, and ocean systems, Grassi offers the following outlook:

In about a decade, coupled atmosphere-ocean-land models (CGCMs) assimilating near-real-time data from the global observing system (including the ocean interior) will (i) predict the probability of certain climate anomalies, to the extent possible, for many regions over season(s), year(s), and possibly even a decade; (ii) allow the attribution of a large part of observed climate variability and change to natural and/or anthropogenic causes; (iii) project future climate more realistically and thus allow better regional projections of climate change impacts; and (iv) be a firmer basis for Earth system models that describe the feedbacks of societies to climate anomaly predictions and emerging climate change patterns.⁴²

Following that summary, Grassi lists what in his view are the general requirements for improvement of the models:

. more as well as more precise global observations of the composition, thermodynamic structure and dynamics of the atmosphere as well as ocean and land parameters through satellite remote sensing;

. improved parameterization of physical and chemical processes in the atmosphere and at the surface, especially for clouds and vegetation;

. the growth of computing power by an order of magnitude every six years if current trends continue;

. assimilation of all, including asynoptic, observations in forecast or climate models; and

. more sophisticated numerical techniques that need less computer time despite improved descriptions of advection and diffusion, thereby not requiring 16 times more computing power if the grid size is halved, but only about 10 times more.⁴³

Grassi urges the creation of a network of climate research centers to facilitate worldwide dissemination of climate information and to foster further progress in developing the improved coupled general circulation models.

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These illustrative comments are cited to support the point that the shortcomings in the existing models should be on the agenda of the meeting of the Conferenceof the Parties to be held in 2002. Improved models to incorporate and integrate the vast amounts of data and advances in scientific understanding of climate forcing factors will provide the Kyoto Protocol Parties with a much sounder basis to have, in the words of the NAS Report, "confidence that the mitigation measures were addressing the underlying causes."

Conclusion

Computer climate models are the indispensable tools to integrate both the historical record of climate variability, and the existing and the vastly growing body of terrestrial, atmospheric, and ocean weather observations in order to provide a sound basis for predictions for changes in climate. In particular the models must provide a sound basis for mitigation decisions, i.e., supply a quantitative basis for reasonable estimates of the contribution to climate changes attributed to human activity as distinguished from changes due to natural causes. Effective mitigation measures address causes attributed to human activity as distinguished from natural causes. Such appropriate models do not yet exist.

Armed with the information as to the shortcomings of computer climate models, one would expect the Conference of the Parties to provide strong support for the research programs proposed by the NAS and the USGCRP. The Conference of the Parties should also be expected to support the development of a program to facilitate and validate the development of appropriate coupled climate models that will incorporate not only the vast amount of new earth observations, new data on historical changes in climate, and the effect of the hydrological cycle on climate (evaporation, rainfall, and clouds), but also feedback from the driving forces that influence climate. The reports referred to above demonstrate the urgency of bringing this matter to the attention of the Conference of the Parties for priority consideration and action.

1. Kyoto Protocol to the United Nations Framework Convention on Climate Change, Dec. 10, 1997, U.N. Doc. FCCC/CP/197/L. 7/Add. 1, art. 3.1 & Annex B, reprinted in 37 I.L.M. 22 (1998) [hereinafter Kyoto Protocol].

2. INTERGOVERNMENTAL PANEL ON CLIMATE CHANGE, THIRD ASSESSMENT REPORT BY THE INTERGOVERNMENTAL PANEL ON CLIMATE CHANGE (Apr. 15, 2000) [hereinafter DRAFT THIRD IPCC REPORT]. The Intergovernmental Panel on Climate Change (IPCC) draft report is some 1,000 pages long. The references in this Dialogue are to a two-part summary: an 11-page "Summary for Policymakers"; and a 70-page "Technical Summary."

3. U.S. GLOBAL CLIMATE RESEARCH PROGRAM, NATIONAL ASSESSMENT: THE POTENTIAL CONSEQUENCES OF CLIMATE VARIABILITY AND CHANGE (June 12, 2000) [hereinafter DRAET USGCRP REPORT].

4. Kyoto Protocol, Annex B.

5. United States Submission for Land-Use, Land-Use Changes, and Forestry, Aug. 1, 2000. Proposed Decision Text for COP-6 (Convention of the Parties that was scheduled for November 2000), pp. 62-75 of the U.S. Submission. So far as we are aware, the topic of computer climate models was not on the COP-6 agenda nor was it the subject discussed at the meeting.

6. NATIONAL ACADEMY OF SCIENCES, GLOBAL ENVIRONMENTAL CHANGE: RESEARCH PATHWAYS FOR THE NEXT DECADE (National Academy Press 1999) [hereinafter NAS REPORT]. See also Robert C. Barnard & Donald L. Morgan, The National Academy of Science Offers a New Framework for Addressing Global Warming Issues, 31 REG. TOXICOLOGY & PHARMACOLOGY 112 (2000); Robert C. Barnard & Donald L. Morgan, The Basic Science Issue in Global Warming Is Whether Human Activity Is Forcing Changes in Climate, RISK POL'Y REP., May 15, 2000, at 33-35.

7. NAS REPORT, supra note 6, at x.

8. Id. at xi.

9. Id. at 445.

10. Id. at 446.

11. Id. at 445-516.

12. Id. at 497-98.

13. U.S. GLOBAL. CLIMATE RESEARCH PROGRAM, UNITED STATES: TAKING ACTION ON CLIMATE CHANGE (Oct. 1999).

14. DRAFT THIRD IPCC REPORT, TECHNICAL SUMMARY, supra note 2 at 26 (emphasis in original).

15. DRAFT THIRD IPCC REPORT, SUMMARY FOR POLICYMAKERS, supra note 2, at 5 (emphasis in original).

16. INTERGOVERNMENTAL PANEL ON CLIMATE CHANGE, SUMMARY FOR POLICYMAKERS: SPECIAL REPORT ON EMISSION SCENARIOS (SRES) 3 (Feb. 18, 2000) (emphasis omitted) [hereinafter SRES REPORT].

17. DRAFT THIRD IPCC REPORT, supra note 2, at 3 (emphasis in original).

18. SRES REPORT, supra note 16, at 3 (emphasis omitted).

19. Id.

20. DRAFT THIRD IPCC REPORT, supra note 2, at 7.

21. Id.

22. SRES REPORT, supra note 16, at 3 (emphasis in original).

23. Id. at 9.

24. Id. at 5.

25. Id. at 10 (emphasis in original).

26. DRAFT THIRD IPCC REPORT, SUMMARY FOR POLICYMAKERS, supra note 2, at 6.

27. Id.

28. Id.

29. DRAFT THIRD IPCC REPORT, TECHNICAL SUMMARY supra note 2, at 18.

30. Id. at 38 (emphasis in original).

31. Id. at 20.

32. NAS REPORT, supra note 6, at 476.

33. Andrew C. Revkin. A Shift in Stance on Global Warming Theory: International Panel Highlights Role of Humans in Climate Change, N.Y. TIMES, Oct. 26, 2000, at A18.

34. DRAFT USGCRP REPORT, supra note 3, at 14.

35. Id. at 3 (emphasis added).

36. Id. at 14 (emphasis added).

37. Competitive Enter. Inst. v. Clinton, No. 00-02383 (RU) (D.D.C. filed Oct. 1, 2000).

38. Richard Kerr, Dueling Models: Future U.S. Climate Uncertain, 288 SCIENCE 2113 (2000).

39. Id.

40. Hartmut A. Grassi, Status and Improvements of Coupled General Circulation Models, 288 SCIENCE 1911 (2000).

41. Id. at 1995.

42. Id. at 1996.

43. Id.