Appendix B

Capacity of U.S. Climate Modeling to Support Climate Change Assessment Activities

EXECUTIVE SUMMARY

The U.S. government has pending before it the ratification of the Kyoto Protocol, an agreement to limit the emissions of greenhouse gases (GHGs), which is largely based on the threat GHGs pose to the global climate. Such an agreement would have significant economic and national security implications, and therefore any national policy decisions regarding this issue should rely in part on the best possible suite of scenarios from climate models.

The U.S. climate modeling research community is a world leader in intermediate and smaller 1 climate modeling efforts—research that has been instrumental in improving the understanding of specific components of the climate system. Somewhat in contrast, the United States has been less prominent in producing high-end climate modeling results, which have been featured in recent international assessments of the impacts of climate change. The fact that U.S. contributions of these state-of-the-art results have been relatively sparse has prompted a number of prominent climate researchers to question the current organization and support of climate modeling research in the United States, and has led, ultimately, to this report.

1  

An example of what is referred to in this document as a small modeling effort is one using a global, stand-alone atmospheric climate model at R15 (~4.5° × 7.5°) resolution; an example of an intermediate effort is one using a global, stand-alone atmospheric climate model at T42 (2.8° × 2.8°) resolution; an example of a large or high-end modeling effort is one using a global, coupled T42 atmospheric/2° × 2° oceanic model (or finer resolution) for centennial-scale simulations of transient climate change.



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Improving the Effectiveness of U.S. Climate Modeling Appendix B Capacity of U.S. Climate Modeling to Support Climate Change Assessment Activities EXECUTIVE SUMMARY The U.S. government has pending before it the ratification of the Kyoto Protocol, an agreement to limit the emissions of greenhouse gases (GHGs), which is largely based on the threat GHGs pose to the global climate. Such an agreement would have significant economic and national security implications, and therefore any national policy decisions regarding this issue should rely in part on the best possible suite of scenarios from climate models. The U.S. climate modeling research community is a world leader in intermediate and smaller 1 climate modeling efforts—research that has been instrumental in improving the understanding of specific components of the climate system. Somewhat in contrast, the United States has been less prominent in producing high-end climate modeling results, which have been featured in recent international assessments of the impacts of climate change. The fact that U.S. contributions of these state-of-the-art results have been relatively sparse has prompted a number of prominent climate researchers to question the current organization and support of climate modeling research in the United States, and has led, ultimately, to this report. 1   An example of what is referred to in this document as a small modeling effort is one using a global, stand-alone atmospheric climate model at R15 (~4.5° × 7.5°) resolution; an example of an intermediate effort is one using a global, stand-alone atmospheric climate model at T42 (2.8° × 2.8°) resolution; an example of a large or high-end modeling effort is one using a global, coupled T42 atmospheric/2° × 2° oceanic model (or finer resolution) for centennial-scale simulations of transient climate change.

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Improving the Effectiveness of U.S. Climate Modeling In this evaluation of U.S. climate modeling efforts, the Climate Research Committee (CRC) was asked by USGCRP agency program managers to address three key questions, which form the basis for the NRC Statement of Task (Appendix B) for this report: Do USGCRP agencies have a coordinated approach for prioritizing from a national perspective their climate modeling research and assessment efforts? Are resources allocated effectively to address such priorities? A related question that the report addresses is whether currently available resources in the United States are adequate for the purpose of high-end climate modeling. How can the U.S. climate modeling community make more efficient use of its available resources? Regarding the first question — the CRC has reached the conclusion that although individual federal agencies may have established well-defined priorities for climate modeling research, there is no integrated national strategy designed to encourage climate modeling that specifically addresses, for example, the objectives of the USGCRP, the needs for comprehensive contributions to the IPCC science base, and the priorities developed by the CRC in its chapter in the Board on Atmospheric Sciences and Climate's report, Atmospheric Sciences Entering the Twenty-First Century (NRC, 1998a). We suggest that the science-driven climate modeling agenda, which has been largely shaped by individual investigators, has been reasonably effective in advancing the frontiers of science, but has not been adequately responsive to the immediate needs of the broader community (e.g., the “impacts” and “policy” communities). With respect to the second question — we find that compared with intermediate and smaller modeling efforts, insufficient human and computational resources are being devoted to high-end, computer intensive, comprehensive modeling, perhaps, in part, because of the absence of a nationally-coordinated modeling strategy. Consequently, in contrast to some of the foreign modeling centers, U.S. modeling centers have found it difficult to perform coupled atmosphere–ocean climate change scenario simulations at the spatial resolutions relevant to certain national policy decisions (e.g., finer than 500 km × 800 km). The recognized strengths of U.S. intermediate modeling capabilities (see, e.g., the sizable contributions from the U.S. coarse-resolution climate modeling efforts in the IPCC reports) have not been effectively harnessed in the development of high-end, U.S.-based models. For instance, leading Earth system modeling efforts in the United States suffer from a computationally limited ability to test and run models in a timely fashion. The ability of the climate community to acquire state-of-the-art mainframes is severely ham-

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Improving the Effectiveness of U.S. Climate Modeling pered by a Department of Commerce “antidumping order” prescribing a financial penalty in excess of 400 percent for the purchase of the world's most powerful commercial supercomputers, which are Japanese in origin. The climate community has not been provided with the financial or computational resources to overcome this barrier and has, therefore, been unable to fully capitalize on the scientific potential within the United States. Not only is insufficient access to powerful computers hampering scientific progress in understanding fundamental climate processes, it is also limiting the ability to perform simulations of direct relevance to policy decisions related to human influences on climate. However, at least as important as the insufficiency of computing resources are the lack of national coordination and insufficient funding of human resources. Regarding the third question — the CRC finds that: A national set of goals and objectives that are agreed to by the USGCRP agencies is essential. A concerted effort by the relevant agencies is needed to establish a coordinated national strategy for climate modeling. In order to optimally use existing scientific capabilities, adequate resources, including greatly improved supercomputing capabilities, need to be provided to the climate modeling community. The reliance of the United States upon other countries for high-end climate modeling must be redressed. In order to avoid the aforementioned problem regarding priority setting, the USGCRP could assume increased responsibility for identifying, from an interagency perspective, any gaps or imbalances in the research priorities established by the individual agencies. At present, however, this is made difficult because some agencies have excluded from their USGCRP budgets the computational and human resources to support comprehensive, coupled atmosphere-ocean climate modeling efforts on par with those in several foreign countries. Although an entirely top-down management approach for climate modeling is viewed as undesirable, national economic and security interests nevertheless require a more comprehensive national strategy for setting priorities, and improving and applying climate models. An effective national approach to climate modeling should ensure that available resources are allocated appropriately according to agreed upon science research and societal priorities and are efficiently utilized by the modeling community. We acknowledge that justification for and design of such a strategy would require a more complete evaluation of the current status of climate modeling in the United States than was possible in developing this report. Development of such a strategy should take place with full involvement of climate modelers within academia and the national climate research

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Improving the Effectiveness of U.S. Climate Modeling centers, along with users of climate modeling results and agency program managers. Climate modeling in the U.S. promotes a healthy competition among various groups, but without better coordination of research among national laboratories and between them and the academic community, it may be difficult to optimally utilize available human and high-end computer resources. In particular, standardization of model output, model evaluation tools, and modular programming structures can facilitate model development and minimize duplication of effort, with the possibility that prudent standardization may yield some cost savings. High-end modeling coordination could also be enhanced through refereed workshops to discuss the pertinent scientific and associated societal issues and to recommend priorities. Effective collaborative linkages between process studies and modeling groups should also be encouraged to facilitate the difficult task of developing, implementing, and testing new model parameterizations. In addition, increased coordination of research-based and operational modeling activities will help ensure that expertise in these two communities is shared. These are but a few of the types of coordinating activities that should be vigorously and consistently pursued. The CRC finds that the United States lags behind other countries in its ability to model long-term climate change. Those deficiencies limit the ability of the United States: to predict future climate states and thus: assess the national and international value and impact of climate change; formulate policies that will be consistent with national objectives and be compatible with global commitments; to most effectively advance understanding of the underlying scientific issues pertaining to climate variability and change. Although collaboration and free and open information and data exchange with foreign modeling centers are critical, it is inappropriate for the United States to rely heavily upon foreign centers to provide high-end modeling capabilities. There are a number of reasons for this, including the following: U.S. scientists do not necessarily have full, open, and timely access to output from European models, particularly as the commercial value of these predictions and scenarios increases in the future. 2 2   U.S. researchers do, however, currently have access to output from most simulations of transient climate change produced by foreign models.

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Improving the Effectiveness of U.S. Climate Modeling Decisions that might substantially affect the U.S. economy might be made based upon considerations of simulations (e.g., nested-grid runs) produced by countries with different priorities than those of the United States. they may miss opportunities to gain valuable insights into the underlying processes that are critical to subsequent modeling investigations. In this regard the issue of accessibility is much more than just a commercial and political issue; in order to most effectively advance the science in the United States, researchers need to have access to both model output and the models themselves to iteratively diagnose the output, advance our knowledge of climate, and improve the models ' predictive capabilities. There are currently relatively few modeling centers anywhere in the world capable of producing moderate resolution (e.g., 250–300 km grid spacing), transient climate simulations. The differences in simulated climate produced by each of these models' different structures help to bound the range of outcomes that the climate system might produce given a certain forcing scenario. Thus, the state of climate modeling throughout the world is such that the addition or removal of even a single model could affect the confidence levels assigned to certain scenarios of future climate change. In other words, not only would the United States benefit from enhancements in its modeling capabilities, the international community would benefit from these efforts as well. The marginal benefits from only modestly increased investments in comprehensive models in the United States could be very large, because, if properly coordinated, the enhanced emphasis on high-end modeling could be built upon the excellent existing U.S. strength in small and intermediate modeling. Thus, to facilitate future climate assessments, climate treaty negotiations, and our understanding and predictions of climate, it is appropriate to develop a national climate modeling strategy that includes the provision of adequate computational and human resources and is integrated across agencies.