Executive Summary

Assessing accurately the current state of the global environment and increasing our predictive capabilities to aid in anticipating how this environment may evolve are enduring challenges to science. The U.S. Global Change Research Program (USGCRP) seeks to advance scientific understanding of the global environment, assist federal agencies in their missions, and provide reliable information for decision making. The scientific and societal motivations of the program remain compelling, and it should be aggressively pursued.

Future development of the USGCRP should be based on a set of guiding principles:

The USGCRP, furthermore, must be implemented as an integrated program of observations, process research, modeling, prediction, information management, and assessment. In order to achieve this, enhanced collaboration and cooperation are required among the scientific community, the Congress, federal agencies, and the Executive Office of the President to ensure that all elements of the program are considered in the context of the integrated program as a whole.

The program should focus on priority issues in four mature areas of Earth system science that are of great scientific and practical importance. Each area will require the contribution of a variety of traditional Earth science disciplines:

  1. Seasonal to interannual climate prediction: Improve prediction skills related to El Niñ o and expand predictive skills beyond the tropics to the extent possible; enhance understanding of land-atmosphere interactions; and establish an international research prototype prediction capability to garner multinational support and to provide benefits to participating countries where usable predictive skill has been demonstrated.

  2. Atmospheric chemistry: Enhance research and scientific assessment on tropospheric chemistry, including tropospheric ozone and its precursors; characterize global distributions of aerosols; monitor biogenic gases especially over continental areas; and continue monitoring and scientific assessment of ozone in the stratosphere, including links to climate.

  3. Ecosystems: Improve documentation, assessment, and understanding of the global carbon cycle; investigate the relationships among vegetation, climate, and land use; study the role of managed and natural ecosystems in the exchange of water, carbon dioxide, and biogenic gases; and provide for the inclusion of surface atmosphere processes and ecosystem dynamics in integrative models and scientific assessments.

  4. Decadal to centennial climate: document, investigate, and assess changes in forcing factors that influence climate; incorporate ocean, land, atmosphere, and ice processes and feedbacks in coupled models; document change through long-term monitoring and assessment of primary climate system characteristics; and investigate economic, technological, and demographic trends that affect the ability of natural and human systems to respond to climate variability and change.

These areas are at different stages of maturity. They have different levels of access to existing remotely sensed data, and each area can make unique contributions to the study of global change. In all these areas, linkages among the physical, natural, and social sciences should be enhanced, and effective U.S. participation in international global change research programs should be encouraged.

Observations of the Earth system play a key role in the USGCRP, and the program requires an integrated observational strategy based on scientific needs, the development and implementation of observing systems appropriate to those needs, scientific guidance, and the application of technological capabilities as appropriate. NASA's Earth Observing System (EOS) should reflect that integrated strategy.

Based on a series of reviews, the program has evolved from its original plans to a reshaped program that is more responsive to the science, more resilient, and more open to the introduction of new technology. There has been a shift from a fixed series of large- vehicle missions to a mixed fleet exploiting small to medium class spacecraft. However, any further structural changes to the near- term EOS missions would cause severe program dislocations. Further budgetary reductions or imposed constraints on technical options could require the elimination of key sensors, slips in schedule, loss of data continuity, and the elimination of advanced technology development that could enhance future research and lower costs.

However, continued evolution is essential. NASA, in concert with the USGCRP community, should consider carefully the observational strategy appropriate for the post-2004 era to ensure that the EOS strategy remains technologically current and scientifically relevant. In the meantime, as a result of technological advances, scientific insights, and programmatic evolution, NASA should move to rebalance the EOS program across space assets, in situ measurements, modeling and process studies, and the data and information management system through a set of feasible and cost- effective actions.

The proposed rebalancing of the programs would offer the potential for significant economies, (e.g., by focusing and simplifying the tropospheric component of the Chem-1 mission on ozone and its precursors, by streamlining the data downlink and initial processing of EOSDIS, and by employing a federation of partners in EOSDIS for product generation). The latter two potentially contribute the greatest savings, and the last offers significant new opportunities to research and private sector communities. To ensure scientific success, however, it will be necessary to direct the resources toward (1) expanding in situ observations, process studies, and large-scale modeling; and (2) developing advanced technology to reduce the costs of second- and third-generation missions and to open new scientific opportunities. With integrated, science-driven, and balanced scientific and observational elements, the USGCRP and NASA's MTPE/EOS program can continue to contribute importantly to ensuring our national welfare in a changing global environment.