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View of the calving terminus of Dawes Glacier, a tidewater glacier that empties into the upper part of Endicott Arm, 80 miles southeast of Juneau, southeastern Alaska. Glaciers are one of the best indicators of regional and global climate change, because they are extremely sensitive to variations in mean annual temperature and precipitation. Glaciers can rapidly gain mass when the climate becomes cooler and more snowy, expanding in both volume and area; conversely, glaciers can quickly shrink in area and volume under warmer and less snowy climatic conditions. As global glacier ice volume changes over time, there is a concomitant rise or fall of sea level, as glaciers lose or gain mass. (Photograph by Donald Grybeck.)

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Interdisciplinary Science Elements

Recognizing that the standard, single-disciplinary approach to scientific research would provide too narrow a focus for those global change issues which cut across two or more disciplines, the CES identified the following seven interdisciplinary science elements on which to build an integrated understanding of the Earth.

Climate and Hydrologic Systems. Understanding the characteristics of the atmosphere, oceans, and land surface that in turn influence temperature, humidity, clouds, and precipitation is a high priority of global change research. These characteristics are extremely variable and, whether natural or human-induced, can have a profound and rapid impact on the habitability of many regions of the planet. Weaknesses in current research programs include sparse data for some regions; inadequate understanding of critical atmospheric, climatic, and hydrologic factors; and poor understanding of how energy is transferred in the atmosphere, oceans, and land. Of particular concern is the lack of understanding of cloud dynamics and their contributions to the climate system.

To improve our understanding of the interrelation between the climate system and the hydrologic cycle, studies will be conducted to learn more about how clouds affect the solar energy that enters and leaves the atmosphere, how the oceans transfer and redistribute that energy, and the rates at which water and energy are transported among the atmosphere, biosphere, and land and ocean surfaces. Global ice balance-how: much ice remains stored in polar ice caps

and glaciers - will play an important part in these studies, as will studies of river basins. The geographic interpretation of land-surface characteristics, particularly from remote-sensing data, will be a significant aspect of these studies.

Biogeochemical Dynamics. Many constituents of the atmosphere have the potential to influence climate, alter the amount and type of radiation that reaches the Earth's surface, and affect the use of nutrients by the biological community. In addition, chemical alteration of the hydrosphere and soils can affect local, regional, and global distributions of biological communities. Carbon dioxide in the atmosphere can enhance "greenhouse” effects, but it can also stimulate plant growth. Such complex interactions must be studied over time to better understand their relative importance.

Chlorofluorocarbons (CFC's) are greenhouse gases, but they also deplete ozone over the Antarctic and to a lesser extent over the Arctic. Ozone in the upper atmosphere filters harmful ultraviolet rays, thus protecting the Earth's biosphere. Ozone, however, is a corrosive gas when breathed by living creatures at the Earth's surface. The complex interactions of CFC's and other chemicals in the atmosphere, hydrosphere, and the land must be studied in detail because they

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Analyses of ice cores from Greenland and Antarctica (lightgray area) show that concentrations of carbon dioxide in the atmosphere have increased about 25 percent since the beginning of the Industrial Era in about 1760. Between 1957 (when systematic annual measurements were begun at Mauna Loa, Hawaii, by C.D. Keeling) and 1989, atmospheric CO2 has increased by about 12 percent (dark-gray area). (Modified from Siegenthaler and Oeschger, 1987, Biospheric CO2 emissions during the past 200 years reconstructed by deconvolution of ice core data: Tellus, v. 39B(1–2), p. 140–154.)

can significantly affect the biosphere, of which mankind is a part.

Ecological Systems and Dynamics. The biosphere is the aggregate of all living creatures that inhabit the numerous individual ecological niches in the Earth system. The response to change of individual species and complex ecological communities must be better understood in both natural and managed environments for us to be able to explain and predict reactions to biogeochemical changes, climatic variation, and other physical and chemical stresses. Ecological systems do not merely react to their environment, they alter it as well. What these alterations are and how fast they take place must be understood to ensure sound policies that can be used to manage the land and all that lives on it.

Earth System History. The Earth's past environments can be deciphered by careful analysis of the geologic record-including fossils, ice cores, tree rings, terrestrial and marine sediments, and other natural archives of earth-history data. Reconstructions of past climates and atmospheric chemical compositions, when compared with the ecological communities that existed during those times, provide an opportunity for estimating how future changes in the Earth's system will affect modern ecological systems, both terrestrial and marine. Studies of the Earth’s history also provide an opportunity to determine whether General Circulation Models (GCM's) of the climate provide realistic forecasts of the future. By running GCM's in a hindcasting

mode, using actual data derived from the geologic record, rather than in a forecasting mode, we can validate their usefulness in making public-policy decisions. Earth system history information also lets us see how the earth system responded to past changes in climate; thus, we will better understand, for example, the historic distribution of surfaceand ground-water resources, biological communities, and how the current distribution may be affected by future changes in the earth system.

Human Interactions. The rapidly growing human population is one of the strongest forces affecting the earth system. In the past, when populations were much smaller and technological sophistication was not at its present level, human impacts were highly localized, but people still caused lasting changes to the Earth's surface and the reduction of some living species to the point of extinction. Modern man has invented chemicals not known to nature and introduced them into the atmosphere, hydrosphere, cryosphere, biosphere, and the solid earth. Man also produces many chemicals found in nature. Modern technology can rapidly alter the Earth's surface morphology, vegetal cover, atmospheric constituents, and virtually all other facets of the environment. Determining which activities have positive and which have negative impacts is important. Studies of landuse practices, energy transformation, legal and regulatory requirements, and economic behavior must be conducted in order to understand the human impact on nature and what appropriate policy directions would be. Computer models that link growth and distribution of population, energy demands, changes in land use, and industrial productivity must then be developed to help decisionmakers better understand the implications of their policy decisions.

Solid Earth Processes. Tectonic activity, in which continents are being formed, moved, combined, and broken up, is the most extreme form of solid earth change. This process, slow as it is in human terms, alters coastlines, puts gases, aerosols, heat, and fluids into the atmosphere and oceans, and changes the elevation of the Earth's crust. Erosional, transport, and depositional processes, which are occurring constantly, move vast amounts

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of materials from all parts of the Earth's surface. Changes in the distribution of permafrost alter the amount of gases trapped in that frozen soil and can affect greenhouse gas concentrations in the atmosphere. This is important for our understanding of climate change and biogeochemical dynamics. Determining what part of alterations in coastlines is due to changes in sea level caused by climate variability-as compared to what part is caused by tectonic, erosional, or humaninduced actions—has tremendous implications for coastal communities. The role of the midocean ridge system and volcanoes must also be better understood because they affect chemical contents of the atmosphere and the hydrosphere. In addition, surficial processes are, in themselves, a feedback mechanism for global change because they affect the dynamics of the atmosphere boundary layer.

Solar Influences. The primary source of the Earth's energy is the Sun. It is now known that the Sun is a variable star; that is, the amount of energy it emits varies over time. Scientists believe that variations in solar energy reaching the atmosphere due to solar variation and the Earth's orbital dynamics played a major role in the largest climatic variation known-the waxing and waning of the Ice Ages. However, much more knowledge is needed to be able to identify what part of global climate change is due to “greenhouse gases” and what part is due to variations in the influx of solar energy. Models that couple the solar winds to the Earth's atmosphere energy balance must be developed. The interaction of various levels of the Earth's magnetosphere, ionosphere, and thermosphere must be defined and modeled. Various scales of interactions from molecular through global must be understood as they relate to the influx of solar radiation in various spectral bands. Also, how the varying spectral output of the Sun affects the atmospheric composition and the Earth's biosphere must be determined.

challenges for data management and information exchange. Vast amounts of data already exist, and much more data are being created as each new program gets underway. Effective management of all this data will provide a needed bridge between observations of global change and scientific understanding of those changes.

Some scientists have difficulty finding out who has what data and how good the data are. Working among their various CES-member agencies and through the helpful assistance of the Interagency Working Group on Data Management for Global Change, scientists are improving access to data and devising better means to handle the massive computerized banks of information. By using existing facilities, NASA, NOAA, NSF, DOE, and DOI will continue to develop and expand a Master Directory for Global Change Data. Hundreds of global change data sets already have been documented and entered. Bilateral agreements have been signed between NASA and NOAA and between NASA and the USGS for the development of data systems to manage satellite data.

An essential component of the overall approach to global change research is the careful blend of ground- and spacebased efforts that are an integral part of research, data gathering, and modeling activities. Of particular future importance is the agreement between the USGS and NASA to archive, process, and distribute all land-related data acquired by NASA's Earth Observing System (EOS), part of NASA's Mission to Planet Earth Program.

Clearly, the challenges of global change research are many. Through the unified federal approach outlined by the CES, those challenges can and will be met in the coming years. In characterizing its fundamental rationale for developing that unified approach, the CES said in its first report ("Our Changing Planet: A U.S. Strategy for Global Change Research,” 1989, p. 27), “In the coming decades, global change may well represent the most significant societal, environmental, and economic challenge facing this Nation and the world. The national goal of developing a predictive understanding of global change, is, in its truest sense, science in the service of mankind.”

Data Management Challenges

Although data management is not a science element, its importance cannot be overstated. The interdisciplinary, interagency, and international aspects of the science elements pose unprecedented

Role of the U.S. Geological Survey in Global Change Research

The strategy of the USGS Global Change Research Program is (1) to learn the basic scientific principles underlying various earth processes, (2) to determine how processes based on those scientific principles act in the environment, and (3) to use that knowledge to develop information and methods to help people manage resources wisely and fulfill their role as informed stewards of their environment.

By John A. Kelmelis

USGS Global Change Research Program

The U.S. Geological Survey has been conducting earth-science research for more than 110 years. Throughout that time the needs for earth-science information have grown. While early activities supported the expansion, exploration, and settlement of vast sections of the country and subsequent research was basic to development of the water, mineral, and land resources of those areas, emphasis has gradually shifted. The traditional needs still exist. It is still important to understand the details of the wide variety of natural resources held and needed by the country, but it is also important to ensure that the information gathered and the research conducted is useful to policy makers and the public in their responsibilities for making wise use of our finite resources. To this end, greater emphasis has been placed on natural hazards, environmental issues, and production of scientific data and research for the increasingly sophisticated needs of the Nation that the USGS serves.

This long history and evolutionary trend in earth-science research and information gathering has placed the USGS in a critical position as a member of the global change research community. Like each of the other Federal agencies doing focused global change research, the USGS fills a particular niche by conducting specialized research that reflects its own unique expertise. This research is linked to that of other organizations to form a network of integrated scientific programs and projects designed to observe, understand, and, ultimately, predict changes in the global environment. In addition, since much of what occurs on the global scale is caused by local and regional changes and will affect local and regional areas, much of the research must be conducted on those scales as well.

Building upon its strengths, the USGS has fashioned a research program that primarily emphasizes activities in the Committee on Earth Sciences' (CES) priority integrated science elements: Climate and Hydrologic Systems, Earth System History, and Solid Earth Processes. In addition, the USGS is conducting focused research in Biogeochemical Dynamics, Ecological Systems and Dynamics, and Human Interactions. Other USGS research programs and projects that are focused primarily on other issues also contribute to our overall understanding of global change in all of the science elements including Solar Influences.

In addition, because of specialized experience in geographic analysis and spatial data management, the USGS has taken a leadership role in integrating information in many science elements to characterize the land processes involved with global change and to develop methods to save, manage, and distribute global change land data.

Important Questions

The USGS program is attempting to answer a number of important questions in ways that will help our Nation and the world make better decisions for the future. Some of these questions areWhat were climates like in the past, and will climates on a regional and global scale be similar in the future? How is the hydrologic cycle affected by climate, and what are the appropriate scientific and societal responses to variations that might occur in the climate? What is the natural contribution of earth processes to short

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Human Interactions
Solid Earth Processes
Earth System History
Solid Earth Processes
Earth System History
Solid Earth Processes
Earth System History
Biogeochemical Dynamics
Earth System History
Climate and Hydrologic Systems
Solid Earth Processes
Earth System History
Climate and Hydrologic Systems
Climate and Hydrologic Systems
Biogeochemical Dynamics
Climate and Hydrologic Systems
Biogeochemical Dynamics
Ecological Systems and Dynamics
Human Interactions
Solid Earth Processes
Climate and Hydrologic Systems
Biogeochemical Dynamics
Ecological Systems and Dynamics
Human Interactions
Solid Earth Processes
Climate and Hydrologic Systems
Biogeochemical Dynamics
Ecological Systems and Dynamics
Earth System History
Human Interactions
Solid Earth Processes
Solar Influences

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and long-term climate changes? How are our coastlines changing? What portion of the change is caused by human activities, and what portion is caused by natural processes? How does the land surface respond to changes-human induced and natural-on local, regional, national, and global scales? Where will the data necessary to study global change come from, how will it be archived, and how will it be distributed? USGS global change efforts have been focused on conducting the research necessary to answer these questions. What were climates like in the past, and will climates on a regional and global scale be similar in the future?

To answer this question, the USGS has expanded major existing programs in Paleoclimates Research, Paleohydrology Research, and studies in Permafrost, Climates of Arid Regions, and Biogeochemistry. The research is directed at establishing the rate, frequencies, and magnitudes of climate change through analyses of the geologic record (including terrestrial and marine cores and related botanical and geochemical records). This

research provides information on the prehistoric natural variability of climate during the last thousands to millions of years. Emphasis is placed on creating a synoptic reconstruction of the Pliocene, about 5.2–1.6 million years ago, the last period when climates were significantly warmer than today. (See article, p. 43.) High resolution studies that can provide information on annual variability in climate are also being done of the recent past, and methods are being examined to extend these high resolution studies into the distant past. Some of the other topics to be studied include terrestrial coring, ice-core glaciology, paleoecology, isotopic analysis, desertification, marine paleoclimates, permafrost studies, and glacial history. How is the hydrologic cycle affected by climate, and what are the appropriate scientific and societal responses to variations that might occur in the climate?

The USGS program in Interaction of Climate and Hydrologic Systems is devoted to process-oriented studies based on intensive field investigations. Its purpose is to improve understanding and prediction of how the hydrologic system

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