Global change research brings significant benefits to the nation and the world by providing a well-founded scientific understanding of the Earth system to ensure the availability of future resources essential for human survival, such as water, food, and fiber. The U.S. Global Change Research Program (USGCRP), along with its international partners, provides the foundation for expanding the ability to both predict and respond to extreme events such as floods, droughts, and heat waves. The USGCRP also aims to reduce vulnerabilities to changes in important environmental factors, such as climate, ultraviolet (UV) radiation at the Earth's surface, and land cover. Scientific knowledge is essential for informed decision making on environmental issues and to ensure the social and economic health of future generations. Thus the USGCRP is a critical investment for the future of this nation, its economy, and the health and safety of its citizens.

The USGCRP was created in 1989 and formalized in 1990 by the Global Change Research Act of 1990. Since that time, global change research has remained a key science initiative. Continuing to improve scientific understanding of the Earth system is a priority of the National Science and Technology Council's Committee on Environment and Natural Resources.


Global change encompasses the full range of natural and human- induced changes in the Earth's environment (see figure). Global change can be defined as changes in the global environment (including alterations in climate, land productivity, oceans or other water resources, atmospheric chemistry, and ecological systems) that may alter the capacity of the Earth to sustain life. Issues related to global change include:

Increased scientific knowledge of global change can reduce the vulnerabilities of human and ecological systems to major environmental changes. Scientific research provides the foundation for building a strong society through continued advances in improving human health and longevity, advancing economic growth and prosperity, and ensuring adequate food supplies and the availability and quality of fresh water.

Major economic losses occur annually from events such as drought, floods, and heat waves. The USGCRP supports research on seasonal to interannual climate change that helps to expand society's capabilities to anticipate and respond to such events. Better understanding of changes in temperature and precipitation patterns and their impacts on crops, forests, and human pathogens will enable society to be better prepared to cope with potentially costly future changes in climate on times scales of decades to centuries. Similar benefits will be evident with respect to enhanced knowledge about the impacts of increased UV levels associated with ozone depletion, changes in biological diversity, and changes in the productivity of land and water resources.

Major Scientific Challenges
Additional Challenges


The USGCRP focuses on the scientific study of the Earth system and its components. Comprehensive investigation of Earth system processes and their interactions is a complex scientific challenge. Human influences and interactions with the environment range from local to global and extend over time periods from days and seasons to as long as decades and centuries. Understanding these diverse scales and interactions requires the participation of an extensive community of scientists from a wide range of scientific disciplines and from all regions of the globe. Therefore, USGCRP activities are coordinated with other related national and international research programs.

USGCRP research is organized around a framework of observing, documenting, understanding, and predicting global change; assessing the consequences of these changes and the vulnerability of human and ecological systems to their potentially adverse impacts; and developing the tools and capabilities to conduct integrated assessments to synthesize and communicate this body of knowledge.

Observing Global Change

A coordinated program of land, ocean, airborne and satellite- based observing systems that measure and monitor different facets of the Earth system is central to documenting changes in the global environment and gaining a predictive understanding of them. The most comprehensive set of sensors for observing global change is a space-based observing system that is being planned and implemented by the U.S. in cooperation with many international partners (see box). Other space-based systems that are currently operating or being planned include operational weather satellites and satellites that measure ozone and other atmospheric chemicals, global sea level, topography, soil moisture, sea-ice dynamics, and ocean temperatures.

These space-based measurements are complemented and enhanced by many surface and airborne systems. For example, an extensive ocean observing system in the tropical Pacific is providing critical information on ocean-atmosphere interactions. Other in-situ systems measure important Earth system parameters such as greenhouse gases, aerosols, ozone, ultraviolet radiation, and land- atmosphere interactions.

Documenting Global Change

Global change research activities generate and require massive amounts of highly diverse data and information to document change, to improve understanding of global change processes, and to carry out integrated assessments of impacts on society. The scope of global change research is very broad, ranging from studies on ecological systems, biodiversity, ocean and atmospheric interactions, and the human dimensions of change, to the development of tools and methods for scientific assessment. Important data therefore need to be archived, preserved, and made available for individual research activities, and related data from various disciplines and disparate sources need to be identified and combined to maximize interpretation.

Providing access to comprehensive global change data and information in usable formats is vital to investigators worldwide. An interagency Global Change Data and Information System (GCDIS) is being implemented to accomplish this task (see box and discussion).

Understanding Global Change

Research on fundamental processes and mechanisms that control the physical, chemical, biological, and human processes that govern Earth-system behavior provides the foundation needed for predicting future changes and for analyzing potential consequences and impacts (see figure). Process research within the USGCRP includes studies of the atmosphere, ocean, cryosphere (snow, ice, glaciers, etc.), lithosphere (land surfaces), marine and terrestrial ecosystems, and the relationships among these components. Understanding the significance of these processes over a wide range of scales in time and space is especially important to predicting future change.

Ongoing programs include studies of clouds and of solar and infrared radiation processes; of the radiative effects of aerosols, especially sulfate particles; and of the interactions of both terrestrial and marine ecological processes with atmospheric composition and climate. The results of this research provide the basis for improved models for predicting future changes in climate and in ozone concentrations, changes in surface UV radiation levels, and changes in the global productivity of fisheries, forests, and agricultural lands.

Predicting Global Change

Global observations and process research studies help scientists develop and improve models that explain and reproduce past global changes and project future changes and their consequences. Accurate predictions of future global change depend on how well models can simulate the dynamics and interactions of the many components of the Earth system, including the oceans, atmosphere, land, and biosphere. Field and observation programs provide the basis for efforts to relate regional-scale and global-scale patterns and variables (especially precipitation, temperature, and surface roughness) and to compare model results with real world conditions.

Improvements in global environmental models are continually being made as modelers extend their efforts to include interactions of the climate system with vegetation, biological productivity, soil processes, trace gas exchange, hydrology, atmospheric circulation and chemistry, radiation budgets, and ocean circulation patterns. For example, recent climate models that incorporate the influence of atmospheric aerosols have been able to predict changes in climate over the last century that are similar to observed changes. These models predict that atmospheric aerosols currently are exerting a nonuniform cooling effect over the globe that is moderating, especially in industrialized regions, the predicted warming from increases in atmospheric greenhouse gas concentrations.

Analyzing Global Change Consequences

Evaluating the consequences of changes in the global environment includes determining and interpreting the economic, health, and environmental impacts of these changes and understanding the potential for adaptation to and mitigation of potential adverse impacts. Ongoing research efforts are focused on improving the understanding of the physiological and ecological responses of plants and animals to global changes in climate, atmospheric gas concentrations, increased UV radiation, changes in land cover, and changes in other environmental factors. These efforts include forest health monitoring; studies of threatened, endangered, and sensitive species; and research into the physiological basis of resistance to environmental stresses such as drought, UV radiation, and the introduction of new pest and predator species. Such programs enable scientists to develop more resistant crop cultivars that are less vulnerable to environmental changes.

Economic research programs are ongoing to analyze the interactions of environmental changes with societal changes, such as changes in consumption patterns, adjustments to technological developments and diffusion, and changing patterns of regional and global trade (see figure). Other programs important for evaluating the consequences of global change include those to evaluate substitutes for ozone depleting compounds, efforts to analyze the costs and benefits of a changing mix of energy supply, and projects to study the effectiveness of soil restoration and reforestation.

Developing Integrated Assessments

The USGCRP is continuing to provide strong support for the conduct of scientific assessments on issues of relevance to decision makers. An important aspect of this activity is the development of tools and methodologies for integrating data from the physical, biological, social, and economic sciences. Integrated assessments can help policy makers develop options for responding to global change by providing them with a comprehensive framework for evaluating the effects of different options. This same framework is also useful for identifying priorities for future research to increase scientific knowledge relevant to an issue.

The USGCRP has played a major role in supporting the contributions of U.S. scientists to the international assessment process. International assessments are carried out to develop a broad consensus on scientific findings from information gathered by tens of thousands of scientists throughout the world on issues of global interest. Examples of international assessments are those conducted by the United Nations Environment Programme (UNEP)/World Meteorological Organization (WMO) on ozone depletion and by the Intergovernmental Panel on Climate Change (IPCC) on climate change.

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Last updated 04/15/96