Our Changing Planet FY 1995

The FY 1995 U.S. Global Change Research Program

Each global change issue is addressed through a process which strives to document, understand, predict, and assess the science in a way that yields results which are relevant to the needs of decision makers. A framework of program elements for coordinating the USGCRP has been developed that expands on these research activity streams, building on the research architecture presented in previous USGCRP documents. The figure on the preceeding page represents the current set of sub-elements within the USGCRP research framework. This framework is being used to evaluate the research balance among Program components and to identify Program gaps. Reviewing the Program by framework element also helps to ensure that the overall USGCRP is well integrated nationally and internationally, and that individual elements of the Program are receiving the required attention and levels of funding. The proposed and ongoing research programs of the USGCRP are discussed below in the context of this framework. Many of these programs are linked to international efforts to address global change, as described in Chapter 4.

Observing Global Change

Continuation of efforts to develop a comprehensive program of land-, ocean-, airborne, and satellite-based observations on a global scale is critical to understanding and predicting global change. Some recent accomplishments and future plans for the observing program are highlighted below: (also see Recent Accomplishments in Observing Global Change)

Space-Based Earth Observing System (EOS)

In order to advance scientific understanding of the entire Earth system and to develop a deeper comprehension of its components and the interactions among them, it is essential that long-term, comprehensive global observations are collected, archived, and analyzed. To achieve this goal, U.S. agencies are cooperating with other countries in developing an international Earth Observing System (EOS). EOS is a series of polar-orbiting and low-inclination satellites that will provide global observations of the land surface, biosphere, solid Earth, atmosphere, and oceans for a minimum of 15 years.

EOS will greatly enhance the ability to understand and predict the effects of many parts of the Earth system (see EOS Satellites and Mission Objectives). These include:

Data from EOS platforms will be made available through the EOS Data and Information System (EOSDIS), which is discussed in the Data Management section of this chapter. Many of the accomplishments and program highlights included in this chapter are directly related to EOS and the series of Earth Probe missions that have been established to complement the EOS platforms. These missions are being conducted with substantial international cooperation and participation from European, Canadian, Japanese, and other space agencies from around the globe. The EOS-AM Series is scheduled for launch in 1998.

Additional Space-Based Observations

Currently, space-based observations are providing data on the following variables that are crucial to monitoring and understanding global change:

Ozone and Other Trace Stratospheric Constituents
The continuous global monitoring of stratospheric ozone levels is extremely important in providing decision makers information that can be used in international ozone assessments and for monitoring the effects of the Montreal Protocol on global ozone levels (see figure). Analysis of data from the Total Ozone Mapping Spectrometer (TOMS) instrument on the Nimbus 7 satellite showed that globally averaged concentrations of total ozone had decreased to unprecedented low values beginning in mid-1992 and continuing through early 1993. With the loss of operation of the Nimbus 7 TOMS instrument in May 1993, following 14.5 years of operation, the TOMS measurement sequence is being continued using the TOMS instrument aboard a Russian Meteor-3 spacecraft launched in August 1991. The Meteor-3 TOMS mission continues to be an excellent model for Russian-U.S. cooperation. Data are received and independently processed by Russian and U.S. scientists. Due to close collaboration between the two groups, almost 100% of the data have been captured and processed.

Preliminary Meteor-3 TOMS results showed that the record low globally averaged total ozone amounts continued until the summer of 1993, when values began to approach pre-1992 values. The Meteor- 3 data are being reprocessed to improve their accuracy so that more quantitative comparisons can be made with data from Nimbus 7. Record low average total ozone amounts in the important 30-60 ° north latitude band, which encompasses most of the U.S. as well as Europe, were also observed in this period. It is thought that these low levels may have been caused, in part, by the eruption of the Philippine volcano Mt. Pinatubo in June 1992. Aerosol concentrations resulting from the Mt. Pinatubo eruption were tracked globally by SAGE II and correlate well with low ozone measurements. Because of its high sensitivity to aerosols, its 1Škm vertical resolution, and its inherent self-calibration, the SAGE II instrument has provided a valuable database useful for long-term studies of atmospheric aerosols. To sustain the observation record, follow-on TOMS instruments are being prepared for launch on an Earth Probes Satellite in 1994, and on the Japanese Advanced Earth Observing Satellite (ADEOS) mission scheduled for launch in February 1996.

The Upper Atmosphere Research Satellite (UARS) has been providing a wealth of new information about the stratosphere and mesosphere since it was deployed from the space shuttle Discovery in 1991. The UARS Microwave Limb Sounder (MLS) continues to provide global maps of ClO, the radical which is responsible for the Antarctic Ozone Hole. MLS measurements show the very high levels of ClO which are produced annually in the Antarctic and Arctic winter stratospheric vortices. Cryogenic Limb Array Etalon Spectrometer (CLAES) observations of the reservoir ClONO2 complement the MLS ClO observations. The springtime formation of ClONO2 in the Northern Hemisphere prevents the rapid ozone loss seen above Antarctica from taking place above the Arctic. The first global mapping of polar stratospheric clouds, which provide the surfaces needed for chemical reactions that release ClO from the chlorine reservoirs, have been provided by the Improved Stratospheric and Mesospheric Sounder (ISAMS) and by CLAES. Our understanding of the polar processes has also been increased by the UARS observations from these instruments.

The Space Shuttle has been an extremely effective platform for measuring trace stratospheric constituents. The second flight of the Atmospheric Laboratory for Applications and Science (ATLAS) took place aboard the Space Shuttle in April 1993, and a third flight is scheduled for October 1994. This will be the first flight of ATLAS during the peak of the ozone depletion season over Antarctica. In addition to the multiple instruments viewing the atmosphere, space plasma, and the Sun from ATLAS, this October mission will deploy the retrievable, German-built Shuttle Pallet Satellite (SPAS) carrying two instruments to make unique infrared measurements of the atmosphere and the first space-based observations of the critical chemical radical, OH. One ATLAS instrument, the Shuttle Solar Backscatter Ultraviolet Spectrometer (SSBUV), will also fly in March 1994 and will provide highly calibrated measurements in support of atmospheric ozone monitoring. In addition to U.S. developed instruments, the ATLAS/SSBUV payload includes instruments from Germany, France, and Belgium, with participation from Switzerland and the Netherlands.

Sea Level, Ocean Topography, and Ocean Color
TOPEX/Poseidon, a joint U.S./France mission, is making global sea level measurements with unprecedented accuracy, allowing scientists the first opportunity to analyze the full spectrum of global signals. The annual variation in hemispherically-averaged sea level was found to be larger in the Northern Hemisphere than Southern Hemisphere by a factor of two, reflecting the influence of the large land mass in the Northern Hemisphere. This asymmetry has not been observed in previous altimetry data due to orbital uncertainties.

TOPEX/Poseidon has also produced the first realistic, large-scale, global ocean dynamic topography. This dynamic topography has been found to improve the estimate of the general circulation of the North Atlantic Ocean based on in situ observations, by reducing the discrepancy between the estimate and the float observations. Preliminary results indicate that a global ocean tide model with an accuracy of 2 cm can be developed using the TOPEX/Poseidon data. The TOPEX/Poseidon data are also being assimilated into a global ocean GCM, and a global framework is being developed for integrating the WOCE and TOGA in situ data.

The Shuttle Imaging Radar-C (SIR-C) is scheduled for flights in April and August 1994 and will be used for geologic, hydrologic, and oceanographic studies. Because of its ability to image Earth through cloud cover and its sensitivity to surface roughness, soil moisture, and sea-ice-water contrast, it is useful in studies of geological features, canopy morphology, sea-ice dynamics, and ocean surface temperature. The Lidar-in-space Technology Experiment (LITE) will fly in September 1994 and demonstrate the utility of a space-based light detection and ranging (lidar) instrument for observations of aerosols, clouds, and surface albedo.

The development and launch of the Sea- viewing Wide-Field-of-view Sensor (SeaWiFS) will assist researchers in understanding the primary productivity of the upper oceans and the fluxes of carbon dioxide and other trace gases across the sea-air interface. SeaWiFS is scheduled to be launched in the Fall of 1994, and will provide the science community with the first space-based ocean color measurements since 1986.

Air/Sea Interactions
Surface winds over the oceans can significantly affect ocean currents, water vapor content in the atmosphere, and biogeochemical cycles. In order to acquire data crucial to understanding these interactions, the NASA Scatterometer (NSCAT) is currently being integrated and tested for inclusion in the Japanese ADEOS mission scheduled for launch in 1996. It is the only instrument currently under development that will be capable of acquiring measurements of wind direction and velocity under all weather conditions.

Solar Irradiance
Because total solar irradiance provides the driving force for the Earth's climate system, it is very important to establish and maintain a long-term record of this energy source. Active cavity radiometer instruments have been flown on a number of research satellites to initiate such a measurement record. The longest continuous record is the 14-year data set of the Nimbus-7 Earth Radiation Budget (ERB) solar measurements, which began in late 1978 and ended in early 1993. Overlapping that record are the Solar Maximum Mission (1980-1989) and the Earth Radiation Budget Experiment (1984- present) total solar irradiance measurements. In addition, an active cavity radiometer is currently operating on the Upper Atmosphere Research Satellite (UARS). Covering the 11-year solar cycle, these measurements show that on this time scale total solar irradiance variations are smaller than anthropogenic climate forcing and are too small to have a significant effect on climate. Nevertheless, it is important to maintain the data record because variability on longer time scales may be larger in magnitude and can potentially cause significant climate response. In fact, total solar irradiance variations are suspected of being one of the causes of past global climate changes on decades-to-century time scales. In the future, total solar irradiance measurements are planned on the Solar Heliospheric Observatory (SOHO) and EOS CHEM satellite missions.

Precipitation
Rainfall is one of the most important parameters which determines climate and, because it is one of the most variable, climate change. The dynamic and thermodynamic processes which generate rainfall are central to the dynamical, biological, and chemical processes in the atmosphere, in the oceans, and on the land surfaces. Latent heating, the primary internal source of energy for the atmosphere, occurs primarily during the process of condensation of water vapor to liquid water and its subsequent precipitation. It is thus essential to quantify the rainfall (and the energy it releases) in order to understand: (1) the dynamics that produce clouds, and circulations and convection that transport and mix minor constituents in the atmosphere; and (2) precipitation patterns that cool the land surfaces, nourish the biota, and generate the haline circulations in the oceans. The Tropical Rainfall Measuring Mission (TRMM), a joint mission between the U.S. and Japan, will aid substantially by quantifying the distribution of the two-thirds of global precipitation estimated to fall in the tropics and subtropics. TRMM is progressing toward a 1997 launch and a three-year mission life, and will provide data to improve climate models by quantifying the energy released by rainfall. This information is critical in understanding the ENSO phenomenon, which is responsible for interannual climate variations that produce drought, storms, and floods on a global scale.

Land Cover and Vegetation
USGCRP agencies cooperated with the European Space Agency, the International Geosphere-Biosphere Programme (IGBP), the informal Committee on Earth Observation Satellites (CEOS), and more than 26 foreign ground-receiving stations in an 18-month experimental program to collect 1 km resolution Advanced Very High Resolution Radiometer (AVHRR) data for each daily pass of Landsat over the Earth's surface. More than 22,000 AVHRR scenes (almost 2 terabytes of data) were collected and archived, and a prototype one-month data set of global vegetation condition was prepared. The data are being used to produce products such as global land cover maps and for monitoring seasonal vegetation condition (greenness) and changes. Based on its initial success, the program is continuing, complementing the operational programs that collect global AVHRR data at 4 and 16 km resolution primarily for oceanic and atmospheric applications.

The Landsat Pathfinder Program has acquired over 1,000 Landsat Multispectral Scanner and Thematic Mapper scenes of the world's tropical forests between the early 1970's and the present. These scenes are being analyzed to determine the extent of deforestation at three epochs, the late 70's, the middle 80's and the present. Current estimates of deforestation are considerably lower than earlier estimates, which were based on statistical data and lower resolution remote sensing. These results suggest that carbon emissions from the region are lower than previously thought, thus reducing somewhat the magnitude of the apparent "missing carbon sink."

Data from Landsat are essential for study of land-cover change and deforestation and their impact on degradation of animal habitats and biodiversity. Plans are underway to restore implementation and management of the Landsat program in light of the Landsat 6 failure in 1993. The final arrangements will likely call for establishing a long-term plan that accommodates the continuity of observations in a manner consistent with current Landsat data, and that allows modernization of the Thematic Mapper sensor by capitalizing on new technology to reduce its mass, volume, and cost. Landsat 7 is scheduled for launch in 1998.

Sea Ice Cover
Recent accomplishments have significantly enhanced the ability to monitor global sea-ice cover and to investigate more thoroughly key processes, such as albedo feedback and ocean density modification, that are important to global climate. A sea-ice atlas was recently published which extended the time series of sea-ice cover to include 1973-1976 and 1978-1987. Current work will yield the complete time series 1973-1993, enabling analysis for trends in sea-ice cover. Automated techniques used to monitor detailed sea-ice characteristics and ice motion from SAR data and to estimate ice- surface temperature from AVHRR data have also been developed.

Land- and Ocean-Based Observations

Most measurements of local and regional climatic variables are taken primarily for weather forecasting and other purposes, and are not described here. The USGCRP augments these many contributing efforts with several special programs.

Greenhouse Gases, Aerosols, and Ozone
The atmospheric burden of aerosols from human activities continue to be quite high. Anthropogenic aerosols include sulfate aerosols, which are formed primarily from sulfur dioxide emitted from major urban and industrial complexes, and carbon-containing aerosols, which are emitted from combustion of fossil fuels and from biomass burning. The impacts of an increasing atmospheric aerosol burden, on a regional scale, include reduced solar radiation at the surface (which can lead to cooling), and changes in atmospheric dynamics (which can lead to variations in seasonal rainfall and temperature patterns). Within the U.S., aerosol measurements are made routinely as part of air quality programs. In 1995, the USGCRP is proposing to enhance efforts to develop a global observational data base by contributing significantly to the Global Climate Observing System (GCOS), an international program proposed by the WMO, ICSU, UNEP, and UNESCO, that will support observations and research on atmospheric clouds, aerosols, water vapor, radiation budgets, and ozone, as well as on critical ocean and land parameters important to global change.

The atmospheric burden of natural aerosols was reduced in 1993. Both space- and ground-based measurements showed that the volcanic aerosols injected into the stratosphere by the June 1991 eruption of Mt. Pinatubo in the Philippines are finally being removed from the atmosphere by natural processes. This has resulted in the return of the global average temperature to the warmer levels typical of the 1980's, and to a reduction in the sharp decrease in ozone concentration in the lower stratosphere that is thought to have been caused by volcanic aerosols.

Research is ongoing to establish a baseline of information about naturally forming aerosols in remote maritime locations to which the climatology of aerosols in more populated areas can be compared. The program, a cooperative effort between government laboratories and universities, includes ship cruises to gather information about aerosol formation in ocean areas of both hemispheres, and the establishment of several monitoring stations in both continental and maritime areas to provide long time series of aerosol data.

Atmospheric concentrations of greenhouse gases and ozone- depleting substances are monitored through an informal worldwide network of in situ and flask-sampling sites. Long-term measurements, from which global trends are inferred, include carbon dioxide, methane, nitrous oxide, and halocarbons. Significant recent findings include the following: (1) Measurements at globally distributed USGCRP observatories have revealed a sharp increase in atmospheric concentrations of HCFC-22, a major CFC substitute, demonstrating that these substances are beginning to accumulate in the atmosphere. A marked inter-hemispheric gradient has also been observed. These data not only provide an important check on the human use and atmospheric fate of this compound as called for by the Montreal Protocol, but also yield new information on transport between the two hemispheres; (2) Thousands of globally distributed measurements have shown that the rate of increase of atmospheric methane slowed down substantially during the last decade, suggestive, but not conclusive of, changes in human emissions; and (3) Observations in 1993 confirm a significant reduction in the rate of increase in the atmospheric carbon dioxide concentration. Annual increases in the mean concentration of CO2 were smaller in the years 1991 and 1992 than in any other year since continuous monitoring was begun in 1957. By 1993, the annual rate was about 25% of what it had been over the past decade. While CO2 accumulation varies from year-to- year, the magnitude and persistence of this reduction are unprecedented in the modern record, and is thought to be due to increased carbon storage in the terrestrial biosphere. Whether these changes will persist is an important, unanswered question.

The USGCRP participates with other nations in a worldwide network of Dobson spectrometers that monitor atmospheric ozone concentrations. Ozonesondes are also used to determine the vertical distribution of ozone in the atmosphere. In addition, strong support is provided for development and deployment of the Network for the Detection of Stratospheric Change (NDSC) of the World Climate Research Programme (WCRP). This network is designed for observing and understanding the physical and chemical state of the stratosphere, with special emphasis on the depletion of stratospheric ozone.

Ocean-Climate Parameters
Movement toward the Global Climate Observing System (GCOS) will continue to be fostered in FY 1995. One USGCRP contribution to this international activity involves a program of long-term ocean observations, with an emphasis on in situ measurements of key ocean-climate parameters. The ocean module will be provided by the evolving Global Ocean Observing System (GOOS). In FY 1995, planned GCOS activities include making the current TOGA Observing System a permanent element of a long-term global observing program in support of routine predictions of ENSO events and their seasonal to interannual climate implications. Reconstruction of the long-term climate record will continue with the assembly of major data records, including precipitation and surface and subsurface ocean parameters. In addition to providing needed data sets for climate application studies, activities to provide correlative in situ data such as surface radiation, aerosol, and precipitation measurements will also continue as a step toward better understanding factors inducing change.

UV Radiation
Significant increases in ultraviolet (UV) radiation have been observed in conjunction with periods of intense ozone depletion. The ozone hole over Antarctica, which in 1993 produced the lowest values of ozone ever recorded on Earth, also allowed record levels of UV light to reach Antarctica. At one Antarctic monitoring site, UV- B, the part of the spectrum most harmful to life, has been recorded at levels 44 percent higher than in 1992. Investigations are now underway on the impact that the increased UV might have on life on and around Antarctica, and on whether animals and plants may have mechanisms to avoid harm from increased UV. Studies have already estimated that UV damage has reduced the productivity of ocean phytoplankton-tiny plants that comprise the base of the food chain- by 6% to 12% in areas affected by the ozone hole.

Substantial progress was made during FY 1993 in establishing a U.S. Interagency Ultraviolet (UV) Monitoring Network. Several Federal agencies are either currently operating or are developing UV monitoring networks. Because each of the individual agencies have different research and operational needs for UV data (e.g., concerns with effects on agriculture, on human health, and on fish and wildlife), each of these networks are using different types of instruments that best address their respective needs. The USGCRP's UV Panel is currently developing a UV monitoring plan to ensure that data collected by the individual agency networks are intercalibrated, interoperable, and easily available to the UV-data user community. A network calibration facility is being established in Boulder, Colorado to serve as the network's technical center. The UV Panel is also consulting with international organizations, including the World Meteorological Organization, to ensure that the U.S. UV monitoring efforts are coordinated with international programs. Version 1 of the UV monitoring plan is scheduled for completion in Spring 1994.

MANAGING GLOBAL CHANGE DATA AND INFORMATION

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 human affairs. Because global change issues are so broad, including human and natural forcing factors, ecological change, biodiversity, human interactions, and comprehensive assessments, the data and information management challenge is not only to archive, preserve, and make data available for individual research activities, but also to be able to combine data from various disciplines and disparate sources (see Recent Accomplishments in Global Change Data and Information Management. This capability to combine data and information into synthesized products will be a major factor in the ability of investigators worldwide to understand, predict, and analyze the multitude of issues related to the policy aspects of the program.

A major focus for data and information management efforts within the USGCRP is the development of the Global Change Data and Information System (GCDIS). The development of GCDIS is being coordinated with related activities within the U.S. Government (see U.S. Data Policy), including those of the Federal Geographic Data Committee and the emerging National Information Infrastructure, in particular with the Government Information Locator Service.

GCDIS will provide the infrastructure of the global change data and information management program. The U.S. Global Change Data and Information System Implementation Plan has been reviewed by the Committee on Geophysical and Environmental Data of the National Academy of Sciences and will be published in the spring of 1994. The GCDIS is a priority-driven system composed of individual agency systems made interoperable by the use of common standards and approaches, technology sharing, and data policy coordination. The GCDIS functions include setting priorities for individual data and information sets, identifying and/or developing those sets, and incorporating them and the necessary related services into GCDIS.

The Earth Observing System Data and Information System (EOSDIS), a component of GCDIS, is being built in an evolutionary manner, with new versions coming online to support launch of EOS platforms and to include technological innovations. EOSDIS Version 0, to be released in July 1994, will provide 'one-stop shopping' for data sets in the distributed data centers of EOSDIS, called Distributed Active Archive Centers (DAACs) (see figure). EOSDIS Version 1, scheduled for 1996, will provide faster, better user services and will include links to existing non-EOS data sets. In the pre-EOS time frame, EOSDIS will provide access to Pathfinder data sets, which are existing long-term satellite data sets used to generate consistent geophysical records.

Examples of other specific programs that contribute to GCDIS include the Geosystems Databases program, an effort to expand databases in the areas of documentation, networking, mass storage technology, and data intercomparisons. The Land Characterization and Data Management program will provide information about and access to global land data sets including vegetation index data derived from AVHRR data, Landsat Multi-Spectral Scanner/ Thematic Mapper (MSS/TM) data, and global cartographic and vegetation data. In addition, post-1978 Landsat MSS and TM data will continue to be converted to stable storage media.

GCDIS will also include a number of long-term, retrospective data sets that are critical for evaluating climate variability and for use in detecting changes in the global climate. These data sets include historical global marine meteorological observations, global upper air data, global and regional variations of temperature and precipitation, global oceanographic data, global baseline data on atmospheric trace constituents, and global aerosol and ozone data sets. Major progress has also been made in the reprocessing of satellite data to provide the scientific community access to a longer and more consistent record of satellite measurements.

The Global Change agencies are developing new techniques for producing needed data sets. For example, a pilot project, completed in early FY 1994, demonstrated the value of reassimilating available data to provide retrospective records. The pilot project reanalyzed atmospheric observations taken from May 1982 through September 1983. The sources of data included satellites, pilot balloons, aircraft, and surface observations. Follow-on projects will reanalyze data from the 1950's to the present.

The first version GCDIS will be available in April 1994, accompanied by two interagency pilot projects:

Efforts are underway to enhance the access of researchers and policy makers to socioeconomic and demographic data and information. New software programs are being developed that enable researchers to extract relevant information and conduct exploratory data analysis from the U.S. Census and its Public Use Microdata Samples (PUMS), which contain detailed socio-economic information based on 1% and 5% samples of the U.S. population. New databases are being developed that combine both physical and biological science data with socio-economic data. For example, worldwide data on income levels and product accounting now are linked with data on resources and soils. One valuable outcome of this new database is the ability to display agricultural land-use changes that are likely to result from changes in climatic conditions. Enhanced data and information products will contribute greatly to increasing understanding of global change.

Understanding Global Change

Advances in the worldwide understanding of global change come through analysis of data and results from existing data sets and studies of past changes in the global system, from current observing systems, from short- and long-term field experiments, and from simulations involving mathematical models. Process research focuses on fundamental processes and mechanisms that control the physical, chemical, biological, societal influences, and geological processes that govern Earth system behavior, including effects of global changes on natural systems and human activities. Improvements in the understanding of this wide range of processes are essential for improving the predictive models being developed to aid national and international policy makers in deciding which options to pursue in adapting to and mitigating impending changes (see Recent Accomplishments in Global Change Process Research).

Research within the USGCRP includes studies of the atmosphere, the ocean, the cryosphere (snow, ice, glaciers, etc.) (see figure), the lithosphere (land surface), and marine and terrestrial ecosystems. The domains and processes include a wide range of scales in time and space significant to understanding the Earth system.

In recognition of the importance of improving understanding of climate change and greenhouse warming, ozone depletion and UV radiation, and the large variations of the seasonal climate, modest augmentations of selected process research programs are proposed for FY 1995. These increases will enhance research on terrestrial ecology and on cloud and radiative transfer processes, and will continue to support research on global water cycles, atmospheric chemistry, and ocean ecology.

Climate and Hydrologic Systems

Research on climate and hydrologic systems has been one of the top priority science elements of the USGCRP over the last several years. This element includes research on processes that regulate the global energy and water cycles, including atmospheric radiation, clouds and precipitation, solar forcing, sea ice and sea level, the roles of the oceans and land-surface properties.

Clouds and Radiation
The first field site for the Atmospheric Radiation Measurement (ARM) Program, established in the area surrounding Lamont, Oklahoma, has started to provide detailed data for improving understanding of cloud and solar and infrared radiation processes in mid-latitude continental regions. This research is providing an intensive data set on cloud-radiation interactions, and will eventually lead to improved global atmospheric models for climate system research and prediction. The types of data being acquired include surface meteorological and radiation data, vertical profiles of the atmospheric parameters important to the atmospheric radiation balance, periodic aircraft-derived data on clouds and radiation, and satellite data from other programs that document the top of the atmosphere radiative fluxes.

Development of instrumentation for the ARM Program is extending the state-of-the-art in atmospheric remote sensing. The Multifilter Rotating Shadowband Radiometer, which represents one of the latest advances in surface-based radiometry, has been operating now for two years. In 1993, the newly developed Atmospheric Emitted Radiance Interferometer (AERI) Spectrometer was successfully deployed for testing. The measurements will be used to validate models simulating radiation fluxes and the profiles of water and other key atmospheric properties and constituents. Additional state-of-the-art instruments, including cloud- and aerosol-sensing lidar instruments and cloud particle radar systems, are now being developed for the ARM Program.

A mission using an Unmanned Aerospace Vehicle is planned in 1995 to measure solar and infrared radiation at the top of the troposphere through several diurnal cycles. Through the Strategic Environmental Research and Development Program (SERDP), measurements using the top-of-the-troposphere platform will be coordinated with ground-based instrument data from the ARM site.

The four-month field phase of the TOGA Coupled Ocean Atmosphere Response Experiment (TOGA COARE) was success-fully completed in February 1993. The unprecedented effort involved hundreds of scientists, students, and technicians from 20 nations to measure moisture, momentum, and heat fluxes between the ocean and atmosphere in the western Pacific Ocean warm pool. The resulting data set is being used to improve the understanding and modeling of the energy exchange between the ocean and the atmosphere. Variations in the extent and duration of the intense exchange of energy between the warm pool and the overlying atmosphere appear to induce climate variations over the entire Pacific basin and beyond.

The Central Equatorial Pacific Experiment (CEPEX) was conducted in March and April of 1993 to examine the validity of a hypothesized thermostat effect which may limit greenhouse warming (see figure). Deep intensive convection is observed to occur when tropical sea surface temperatures (SSTs) exceed about 27°C. This convection produces cirrus (ice particle clouds) anvils that spread out over millions of square kilometers. It is hypothesized that while cirrus clouds trap outgoing infrared radiation, they also reduce incoming solar radiation, the net effect being to stabilize SSTs, thereby acting in effect as a thermostat. CEPEX results will be available by the Spring of 1994.

Water and Energy Balance
Several projects which are part of the Global Energy and Water Experiment (GEWEX), of the WCRP, are contributing to the understanding of the diurnal and seasonal aspects of the water and energy balance. These studies are assessing the accuracy and resolution to which the components of the energy and water balances can be determined from in situ measurements, remote sensing retrievals, and the use of regional mesoscale climate models. As part of a series of regional studies taking place around the world, the GEWEX Continental-scale International Project (GCIP) is examining the energy budget and hydrological cycle of the Mississippi River watershed, which includes 44% of the land area of the continental U.S. and drains all or portions of 30 states. Other GEWEX projects include land-surface and cloud climatology studies using data from geostationary and polar-orbiting international satellites.

Sea Level
Melting of the Greenland and Antarctic ice sheets would raise sea level by some 70 meters, and yet it is still not known whether, as a whole, these ice sheets are currently growing larger or smaller. Comparison of Geosat and Seasat data suggest that parts of the southern Greenland ice sheet thickened by about 1.3 meters between 1978 and 1987, an average of 15 cm/year. Comparison of the aircraft laser data with surface measurements made in 1980 provides support for this result - this comparison suggests that the ice thickened by up to two meters between 1980 and 1993. Increases in the volume of the ice sheet could lead to a decrease in sea level; however, in the case of the Greenland ice sheet, the measured increases in thickness may be offset by ice sheet deterioration in marginal areas.

Airborne laser altimeters are being used to survey the Greenland ice sheet. Advances have been made in these airborne surveys so that they can now measure surface elevations on grounded ice sheets to an accuracy of tens of centimeters. Additionally, development of techniques for mapping ice sheets and measuring ice-stream motion from Landsat and SAR data has allowed compilation of the first SAR map of Greenland, which reveals a hitherto unknown ice stream some 50 km wide and 300 km long. These, and other achievements, will contribute towards development of a capability to monitor the mass balance of the polar ice sheets, and to understand what is causing observed thickening or thinning. In turn, this will lead to an improved ability to predict ice-sheet response to prescribed climate changes, and thus to estimate future changes in sea level.

Seasonal to Interannual Variability
The TOGA program, to conclude in 1994, has greatly enhanced understanding of the causes of seasonal to interannual fluctuations in the tropical Pacific. Analysis of results from the TOGA/COARE intensive observation period, coupled with model studies, are providing the basis for improving predictive capabilities. To extend the predictability of seasonal to interannual fluctuations beyond the tropical Pacific, the Global Ocean-Atmosphere-Land System (GOALS) program is being developed, which will contribute to the WCRP Climate Variability and Predictability Programme (CLIVAR). GOALS is intended to build upon the successes of ENSO research by extending predictability of seasonal to interannual fluctuations beyond the tropical Pacific to include the effects of the other tropical upper oceans, higher latitude upper oceans, and land surface processes. This program represents a focused U.S. effort to develop and improve models for forecasting seasonal to interannual precipitation anomalies like those in the Midwest last summer, seasons to years in advance.

World Ocean Circulation
Long term (decadal) changes in the ocean are being investigated through the World Ocean Circulation Experiment (WOCE) and the Atlantic Climate Change Program (ACCP). While it is known that the ocean and atmosphere interact strongly, the feedback mechanisms coupling them are inadequately understood. For example, it is believed that the ocean can act both as a heat sink and as a trap for atmospheric greenhouse gases, thereby slowing the rate of global warming. WOCE is designed to provide the data needed to improve and test the availability of models to predict long-term behavior of the ocean. ACCP, which contributes to the WCRP CLIVAR program, is focused on the particular relationship between the global climate and the Atlantic Ocean, the basin which has apparently been the most variable.

Improved understanding of the thermodynamics of the oceans is central to developing global models that predict the effects of global change on the Earth system as a whole. Evidence suggests that there has been a 35-year warming trend in the subtropical North Atlantic Ocean temperatures down to 2500 meters. There are also new estimates of vertical mixing in the ocean, and of heat transport across mid-latitudes in the South Pacific and South Atlantic, suggesting an imbalance between the Northern and Southern Hemispheres that may be compensated by changes in the Atlantic "conveyor belt" deep circulation. Changes in large-scale ocean circulation could be the cause of regional shifts in climate patterns.

Atmospheric Chemistry and Biogeochemical Dynamics

Quantitative understanding of the sources and sinks of atmospheric trace gases and aerosols and of the interactions which contribute to changes in biogeochemical processes are crucial for making reliable predictions of future concentrations of atmospheric greenhouse gases.

Carbon Dioxide
The annual increase in atmospheric concentrations of carbon dioxide is the difference between the emissions of CO2 from combustion of fossil fuels and biomass and uptake by oceans and the biosphere. It is believed that enhanced sinks for carbon are responsible for the recent slowdown in the CO2 increase in the atmosphere, but the exact cause remains unexplained (see Global Carbon Cycle).

Recent evidence suggests that in the short term, at least, the land sink may be larger than previously thought. Anomalies in surface temperature and precipitation may have allowed terrestrial ecosystems to accumulate more carbon in the period 1991 to 1993 than normally would have been the case. The cause of the anomaly is unclear, but the timing is coincident with the eruption of Mt. Pinatubo. One hypothesis is that lower temperatures at the Earth's surface temporarily reduced rates of respiration and thereby enhanced net carbon uptake.

Because few measurements of the carbon concentration in coastal oceans have been made, there is only limited understanding of the role of continental shelves in the exchange of carbon dioxide between the coastal shelf and the atmosphere above it, even though half of ocean photosynthesis is estimated to occur on continental shelves. A field research program is underway near Cape Hatteras, North Carolina that will provide important information for quantifying the processes which affect the cycling, flux, and storage of carbon and other biogenic elements at the land/ocean interface and for defining ocean-margin sources. Preliminary data on the CO2 gradient indicate that continental shelves such as the one near Cape Hatteras could be a relatively large sink for atmospheric carbon dioxide during certain times of the year.

To further refine estimates of the ocean sink, the Global Survey of CO2 in the Oceans (JGOFS) has now nearly completed its work in the Atlantic and Pacific Oceans, and is beginning work in the Indian Ocean. The Survey is being undertaken in conjunction with cruises of the World Ocean Circulation Experiment (WOCE). The goal of the survey is to obtain a high accuracy "snapshot" of the distribution of carbon dioxide within the world's oceans. An extensive data quality control program established at the start of the Survey included the provision of certified reference materials and certified analytical equipment. This has resulted in a data set of unprecedented accuracy.

The WOCE-CO2 survey data set will be used to calculate the exchange of CO2 between the ocean and the atmosphere. Together with models of the atmospheric transport of CO2, and with an improved understanding of the CO2 fertilization effect, these calculations will allow the locations and magnitudes of net sources or sinks of CO2 to be inferred on a planetary scale. The data set will also permit improved estimation of the uptake of fossil fuel CO2 by the oceans, both through modeling and through correlation with the distribution of other man-made compounds within the ocean.

Ozone
Ozone measurements suggest that tropospheric ozone derived from anthropogenic pollution may exceed that derived from natural sources over the North Atlantic. Long-range transport of continentally-derived precursors is estimated to account for as much ozone on a hemispheric scale as do natural processes. Because upper tropospheric ozone is an extremely potent greenhouse gas, national and international policy makers will need to consider global warming in the context of regional pollution abatement. These results were part of the IGBP International Global Atmospheric Chemistry (IGAC) Program to study the chemistry of the global atmosphere.

New areas of emphasis in ozone research include understanding the role of biomass burning and stratospheric inclusions in determining the high ozone concentrations seen over the South Atlantic. Field campaigns are underway in the tropics and at high northern latitudes designed to study boundary layer fluxes of ozone and exchanges with the free troposphere. Specific process research is being conducted on chemical mechanisms for ozone formation/destruction (sensitivity/uncertainty evaluation of known kinetics parameterizations and determination of unknown mechanisms); and on evaluations of the joint action of transport and chemistry in determining the state of mid-latitude, lower stratospheric ozone, through global models and other diagnostic tools.

Perfluorinated Hydrocarbons
Laboratory measurements have demonstrated that perfluorinated hydrocarbons (PFCs), which are greenhouse gases emitted as by-products of industrial processes such as aluminum production and proposed as CFC substitutes, persist in the atmosphere for thousands of years. As a result, their emissions into the atmosphere are essentially irreversible, and their contributions to global warming are inadequately characterized by short-time global warming potentials. Proper consideration of the environmental consequences of PFC emissions, therefore, imposes upon the national and international policy community a new requirement to grapple with extremely long-term effects. Refined methods for calculating ozone depletion potentials are being developed using atmospheric measurements rather than only model results.

Aerosols
Emissions into the atmosphere of aerosols, and gases that chemically react to form aerosols, can have direct effects both on the global radiation balance and on global atmospheric chemistry. Research on the physical and chemical characteristics of tropospheric aerosols is underway to determine whether changes in aerosol (and aerosol precursor) emissions may be, at least temporarily, hiding the warming effect of greenhouse gases. Research on the radiative effects of sulfate particles formed in the lower troposphere, mainly as a result of emissions from coal combustion, is important to understanding whether they may be, in the near term, counterbalancing the enhanced greenhouse effect of carbon dioxide. For aerosols emitted by biomass burning, the sign of their climatic effect is less certain, being dependent on the amount of black carbon in the aerosol. The absence of measurements confirming the predicted increase in land surface temperatures in the Northern Hemisphere appears to be most related to recent increases in the frequency of cloud cover. Recent studies suggest that the hemispheric asymmetry in this century's warming may be due, at least in part, to the anthropogenic aerosol emissions being largely in the Northern Hemisphere.

Methane
Atmospheric methane concentrations have been increasing at a reduced rate. The residence time of methane in the atmosphere has been found to be 25% longer than previously thought, however. Research is ongoing to quantify human-induced methane emissions from landfills, coal mines, natural gas systems, rice paddies, and biomass burning as well as natural emissions of methane from wetlands and other sources. The results of this research will provide baseline data to help understand the causes of the increasing concentrations of atmospheric methane and for identifying strategies for reducing emissions from various sources.

Ecological Systems and Dynamics

Regional measurements of CO2 uptake by forest vegetation suggest the net uptake of carbon worldwide could account for the estimated "missing" carbon in the global carbon budget. Based on almost two years of continuous measurements of CO2 exchange between the atmosphere and the vegetation and soils of Harvard Forest in eastern Massachusetts, the net annual uptake of carbon by the forest ecosystem was estimated to be as large as 4 tons per hectare. Confirmation of these results with other natural vegetation studies would support the use of forest management (including reforestation) as an interim mitigation strategy that is an environmentally attractive way of helping to reduce the buildup of atmospheric CO2. Uncertainties regarding the rate of deforestation, conversion of land to agricultural use, population growth, and land management practices make it difficult to estimate the extent to which forests can conserve or sequester large quantities of carbon on a global basis.

Five Boreal Ecosystem-Atmosphere Study (BOREAS) field campaigns will be conducted throughout 1994, starting with a winter campaign in February and ending with a September end-of-growing-season campaign. BOREAS is an international, multidisciplinary study to improve understanding of the exchange of gases, energy and water between the boreal forest biome and the atmosphere in order to clarify their roles in global change. It is sponsored jointly by agencies within the U.S. and Canadian Global Change Research Programs. Airborne and spaceborne remote sensing will be used to extend understanding of these processes from the local to regional scales.

Recent research has documented that the uptake of carbon by soils is a dynamic process that varies in relationship to soil age and type. Understanding the role of soils in the carbon cycle is critical to understanding how human activities, including agricultural and forestry practices, influence the fluxes of carbon from terrestrial ecosystems. Remotely sensed surface temperature over a 300m km- by-300 km region in western Montana has shown that the ratio of surface temperature to a normalized difference vegetation index can distinguish wet and dry conditions in a forest. This ratio may have applications in climate models, research on decomposition, and monitoring of fire conditions.

USGCRP Terrestrial Ecology Initiative
The USGCRP proposes to augment ecological research through a Terrestrial Ecological (TECO) initiative in FY 1995. The initiative will focus on the effects of global change (e.g., climate) on ecosystems, and the feedback effects of ecological processes on atmospheric composition (e.g., greenhouse gas concentrations) and climate. Its scope includes research on how ecological processes are affected by altered atmospheric CO2 and other trace gases, by altered climate conditions, and by changing land-use patterns - all in relation to constraints of other resources (e.g., nutrients, water, light, etc.). This initiative also includes research on how ecological systems affect the exchange of CO2 and other trace gases with the atmosphere and ultimately determine terrestrial sources and sinks of carbon.

Implementation of the TECO initiative would include:

Human Interactions

Human activities can greatly influence global change as well as be significantly influenced by global change. Changes in land use can be a major driving force of environmental change. Conversion of natural forests into croplands and human settlements, overgrazing of grasslands, intensive planting and fertilization of agricultural lands, and the world wide increase in population density can have significant impacts on the global carbon budget and fluxes of greenhouse gases. While the use of Landsat and other satellite data have been instrumental in monitoring land-cover change in many regions of the world, this type of observation does not provide detailed information about specific land management practices. The international Human Dimensions Programme plans to address questions regarding: (1) How has land cover been changed by human use over the last 300 years? (2) What are the major human causes of land-use change in different geographical and historical contexts? (3) How might these land-use changes affect land cover in the next 50 years? and (4) How might changes in climate and global biogeochemistry affect both land use and land cover?

The Consortium for International Earth Science Information Network (CIESIN) is supported by USGCRP agencies to assist in compiling global-scale time series and baseline data and information on the human component in global environmental change, to develop an advanced network for data access, to conduct research and analysis focusing on socioeconomic data, and to provide services through the Socioeconomic Data and Applications Center (SEDAC) Network to disseminate data. CIESIN has been working to develop informal international partnerships and an operational framework that allows user communities to share data and information electronically among international data archives and resource centers.

Earth System History

By reconstructing worldwide snapshots of past climates, scientists can test how effective climate models are in simulating past conditions and thereby improve the ability to model and predict the impacts of future changes in global climate. Evidence from ice cores, bogs, lake and ocean sediments, and glacial moraines document that the climate may have changed frequently and abruptly over the last few million years. Additionally, data from time series reveal previously unknown process relationships that help establish the rate of change within the climate system.

USGCRP agencies established the National Ice Core Laboratory at the Federal Center in Denver, Colorado. This is a facility for storing and studying ice cores recovered from the polar regions of the world.

Polar ice is an excellent recorder of climate history, and provides the only known continuous, direct recorder of paleoatmospheric composition. Recent results from the analysis of Greenland ice cores have revealed that rapid changes in climate may have occurred over time periods less than a decade, and that these changes are probably associated with "switching" between stable ocean modes, a "switch" that may have been triggered by sea-ice conditions.

Research is underway on marine and terrestrial climates and climate variability for a time interval during the Pliocene, about three million years ago, when the Earth was substantially warmer than it is today. This research is establishing a global data set for use in modeling experiments. The analyses indicate that a significant portion of high-latitude temperature changes during past climate changes are related to changes in oceanic heat transport.

Solid Earth Processes

Solid Earth research is directed toward understanding shorter time scale geological processes, such as hydrothermal circulation, which accounts for most of the heat loss from the interior of the Earth through the mid-ocean ridge system. Hydrothermal venting at mid-ocean ridges produces a wide variety of important effects in overlying water columns, including formation of turbulent, buoyant plumes, the introduction of chemicals and biota, and the modification of deep ocean circulation and mixing patterns.

Volcanic eruptions can contribute large quantities of gases and aerosols (see figure) to the Earth's atmosphere and have been linked to past climate change (see figure). The USGCRP Global Volcanism Program maintains: a database of the world's volcanoes and their known eruptions of the last 10,000 years; an archive of maps, photographs, and other historical documentation of the world's volcanoes; and a Global Volcanism Network, a network tracking and reporting current volcanic activity around the world.

Investigations of surface deposits show that sand dunes and sand sheets occur extensively on the semi-arid Great Plains. These wind generated deposits are now stable because of the presence of a sparse vegetation cover. Use of a dune mobility index, which incorporates wind strength and aridity factors, shows that increased temperature and reduced precipitation could mobilize the sand deposits throughout a significant area of the U.S. Great Plains. Research using geodetic observations has demonstrated a correlation between variations in atmospheric and oceanic circulation and variations in Earth dynamics. Systematic variations in Earth's angular momentum have been observed and correspond well with El Niñ o and La Niña events.

Solar Influences

Recent research conducted through the Solar Influences Program (SIP) suggests that the mesosphere and lower thermosphere are exceedingly sensitive to changes in greenhouse gas concentrations in the lower atmosphere - small variations in the greenhouse gas concentrations are predicted to cause large changes in the temperature of these tenuous high-altitude atmospheric regions. Unlike the lower atmosphere which is expected to warm by a few degrees Celsius, a doubling of greenhouse gas concentrations could cool the mesosphere and lower thermosphere by between 10 to 50° C. The increase in the occurrence of arctic noctilucent clouds in the mesosphere over the last 20 years indicates that such a cooling is already taking place. The influence of solar variability on global surface temperature changes may have been significantly underestimated.

Predicting Global Change

Models of the Earth system will provide the only rigorous means for developing quantitative projections of the interactions of atmospheric composition, climate, sea level, terrestrial and marine ecosystems, agriculture, water resources, and the effects of human activities. Models and related analysis activities provide the predictive link between the physical Earth system and the human dimensions of global change, including economics, social structure and evolution, and resource use and management. Enhanced activity in global modeling activities proposed for FY 1995 will build on recent advances (see Recent Accomplishments in Integrative Modeling and Prediction of the Earth System) in process studies and observations, with the goals of enhancing forecast capabilities for seasonal to interannual climate variations and strengthening the confidence that can be placed in longer-term climate projections and insights.

Earth System Modeling and Long-Term Prediction

Prediction activities contribute to the understanding of the interactions among the components of the Earth system, including: ocean circulation (see figure) and atmospheric interactions; atmospheric chemistry; potential consequences of emissions of carbon dioxide and other greenhouse gases on climate (see figure) and of chlorofluorocarbons and other gases that perturb the stratospheric ozone layer; changes in land use that alter water and biogeochemical balances; changes in biological systems on land and in the oceans; changes in sea level; and changes in how societal systems interact with the climate. Results from model simulations form the basis for the state-of-the- science assessments being conducted both nationally and internationally.

Research on the sensitivity and response of the Earth's climate to natural and human-induced perturbations to the radiation balance, including the effects on the climate due to changes in greenhouse gas concentrations, aerosol loading, and other factors will be conducted to support the 1994 and 1995 IPCC assessments. Researchers will use specific scenarios developed with global models to conduct comparison and evaluation studies of global change projections. Additional modeling studies will include: the climatic effects of aerosols, smoke and clouds; interannual variations in global and tropical water cycle; land use change and deforestation; and variations in atmospheric chemistry due to human activities, volcanic activity, and natural biogeochemical cycles. Results from model simulations are being compared with historical data sets to determine the extent of climate variability that can be explained by the models and their representation of the Earth system.

Accurate predictions of future global change depend on how well models can simulate the many components of the Earth system, including the oceans, atmosphere, land, and biosphere. Global and regional modeling programs are intensifying their efforts to include vegetation, biological productivity, soil processes, trace gas exchange, hydrology, atmospheric circulation and chemistry, radiation budgets, and ocean circulation. Research programs including the international Global Energy and Water Experiment (GEWEX) will provide the basis for these efforts to relate regional-scale to global-scale patterns and variables (especially precipitation, temperature, and surface roughness) that strongly influence land surface processes and their interactions with the atmosphere.

The Computer Hardware, Advanced Mathematics and Model Physics (CHAMMP) Program focuses on redesigning and rewriting models for use on the newly emerging, massively parallel computers to take advantage of their greatly increased speed and performance. CHAMMP is exploring the potential for using these new computers for century-scale climate projections and simulations and conducting analytic studies to further define the theoretical limits of climate predictability. Important improvements in the ability to run large- scale ocean and atmosphere models have been made with the continued development of high performance computers and improved algorithms and tools for model development.

Simulations from a high resolution ocean model implemented on a massively parallel computer, the first model to accurately simulate mesoscale eddies over the entire globe, compare favorably with satellite observations, demonstrating the model's ability to realistically simulate ocean circulation. The description of ocean eddies is a key factor for accurately characterizing fluctuations in the ocean circulation which contribute to climate change on the decadal and longer time scales. A version of this ocean model will be coupled to an atmospheric general circulation model for climate change research in order to contribute to the 1995 IPCC assessment.

USGCRP modeling activities will significantly augment programs that support the development of coupled models and test component models in ways that can provide deeper insights and improved projections of Earth system behavior. The USGCRP is sponsoring the development and initial testing of prototype Earth system models (ESMs) through the combined efforts of the Climate Dynamics and Experimental Prediction, Climate Modeling Analysis and Prediction, and Earth System Modeling and Global Analysis programs. These modeling efforts combine the atmosphere, oceans, land surfaces, and biogeochemistry into an adaptable and flexible system. The biogeochemical component of prototype ESMs are reproducing the seasonal variation in the atmospheric carbon dioxide record. These models are being applied to study the historical evolution of the CO2 concentration. Coupled atmosphere-ocean models are being used to investigate climate variability and climate change on time scales from seasons to centuries. Work sponsored by the USGCRP is progressing on developing realistic representations of land and natural resource interactions, vegetation, and regional land processes for inclusion in Earth system models. Detailed land surface models are being linked to coupled ocean-atmosphere system models, and early simulations suggest that significant relationships exist between ocean surface temperatures, atmospheric circulation patterns, and hydrologic conditions over mid-latitude continents. Sea-ice models are also being developed and incorporated into the ocean- atmosphere-land models, to yield more fully coupled climate system models.

Seasonal to Interannual Forecasting

Significant success has been demonstrated in forecasting large- scale changes in the sea surface temperature of the tropical Pacific Ocean, especially transitions into the ENSO warming events that dramatically alter precipitation patterns over much of the Pacific basin, including the southwestern United States. This improved understanding will provide both immediate and long-term benefits. On the short-term, the people and economies of the nation and world will benefit from being able to prepare for the consequences of the large natural climate fluctuations caused by ENSO events; on the longer-term, there will be better understanding of whether human activities could affect these fluctuations, which are the largest precipitation anomalies now affecting international agriculture and other human activities.

In FY 1995, the development, testing, improvement, and implementation of a quasi-operational experimental forecasting system on seasonal to interannual time scales will be extended through the establishment of a multinational network of centers to produce and distribute forecast guidance products. Activities sponsored through this network will include transfer of the products of predictive models to regional application centers around the world so that tailored regional predictions can be provided. Application of regional forecasts on time scales of interest to society are expected to aid in advance planning for agricultural production, resource use, and other societal activities.

Attribution and Reconciliation with Observations

The world is projected to warm a few degrees (Celsius) over the next century due to the increase in the concentrations of greenhouse gases. Such an increase would be about half of the rise that has taken the Earth from the glacial climate of 20,000 years ago to the warmth of the present. Some studies suggest that the effects on society and the natural environment may be very large and would require significant resources and lifestyle changes to prevent or ameliorate. It is therefore essential to understand the degree of confidence that can be placed in the model results. Models and observations are being tested and compared for a range of time periods. Such comparisons will provide a measure of the accuracy of model representations and an estimate of the confidence of model predictions.

The Atmospheric Model Intercomparison Project (AMIP), which contributes to the WCRP's CLIVAR program, is diagnosing the abilities of global atmospheric models to represent the present climatic state and the observed climatic variations over the recent past, specifically 1979 to 1988. About 30 modeling groups from around the world are carrying out test simulations. The set of runs will be completed in 1994 and the analysis of the runs in 1995. Disagreements with observations and with other models, including regional temperature biases, excessive precipitation, and abnormally strong winds, are being examined. Once this part of AMIP is completed, the focus will shift to examining the capabilities of ocean- atmosphere models to simulate climate variations and change.

To provide more complete data sets for continuing research on model fidelity, four-dimensional data assimilation techniques are being developed and used to combine many kinds of satellite and surface observations to produce carefully checked data products for research, monitoring, and applications. A prototype model-driven data assimilation system has been developed and used to produce a set of reanalyzed data fields for 1985-1989. These data will be used to study and test model simulations of the 1986-87 El Niñ o (warm event) and the La Niñ a (cold event) of 1988.

Model simulations of paleoclimatic changes are also underway to understand the ability of models to predict very long term climatic change and to understand the sensitivity of climate to past changes in atmospheric composition and radiative forcing [see earlier subsection on Earth system history]. These simulations and related analyses suggest that the modeled estimates of climate change are roughly correct, although problems in understanding the reasons for past climate changes limit the accuracy of the simulations that can be performed.

Of most importance, but hardest to accomplish, is to test model performance against the observed climatic changes of the past two hundred years. This is due in part to there being multiple influences that affect the climate, including: (1) human-induced changes in greenhouse gas concentrations, in ozone concentrations, in the atmospheric loading of sulfate, and biomass aerosols; and (2) natural induced changes in volcanic aerosol loading, in solar irradiance, and, possibly, in ocean circulation. It is especially difficult to construct a model test that can consider all of these factors together for comparison to the changing set of conditions since the start of the Industrial Revolution. The USGCRP agencies are engaged in a continuing effort to formulate an effective approach for carrying out such an analysis.

Evaluating The Consequences

Evaluating the consequences of global change includes determining and interpreting the environmental and societal impacts of global change, and understanding the potential for adaptation and mitigation to ameliorate adverse impacts (see Recent Accomplishments in Evaluating the Consequences of Global Change).

Environmental Impacts and Adaptation Mechanisms

The FY 1995 Program proposes to enhance research to improve fundamental understanding of physiological and ecological responses of plants and animals to global changes of climate, atmospheric gas concentrations, and increased UV-B radiation. The international Global Ocean Ecosystems Dynamics (GLOBEC) program examines the relationship between physical and biological oceanic processes that govern how the recruitment of marine fishes and zooplankton are linked to climatic change. Sensitivity analyses are being conducted to determine the effects of UV radiation on the oceanic carbon cycle in relation to global warming. Methodologies are being developed and validated for estimating the effects of global climate change on lake environmental conditions and fishery resources at a regional scale. The reproductive dynamics of fishery resources, such as sardine, anchovy, and mackerel stocks off the coasts of California, Chile, Spain, and West Africa are being examined.

New research will be initiated to further evaluate the potential impacts of climate change at the regional level (see figure). Recent modeling studies have successfully simulated winter precipitation at the local scale for a high-elevation, high-water-yielding mountain watershed in western Colorado by coupling regional/local scale atmospheric models to watershed models. These models helped investigate the effects of possible increases in temperature at Federally-managed reservoirs in western watersheds that might result from a doubling of atmospheric CO2. The results indicated that the effects of the temperature increases on aquatic ecosystems and fisheries could be significant.

Research on the global and regional effects of climate change on agriculture has shown that, for a moderate scenario of climate change accompanying a doubling of greenhouse gases, the production potential of global agriculture may not be seriously threatened. These results are sensitive to the positive direct effect of carbon dioxide fertilization on plant growth. These results also suggest agricultural production losses may be more severe in developing countries. Additional research in this area is proposed for FY 1995.

Studies are currently underway to determine how atmospheric deposition affects tree growth. The interactions of deposited pollutants with global change parameters (e.g., elevated CO2) and with biotic stresses (e.g., insect feeding) are also being investigated. These studies have demonstrated that pollutants such as ozone and elevated CO2 influence insect behavior, and hence forest health. New research is proposed to refine ecosystem response models and improve the ability to anticipate ecosystem fluctuations due to climate change.

Contributing research on the adaptation of natural ecosystems to global change includes forest health monitoring, studies on threatened, endangered, and sensitive species, and research into the physiological basis of resistance to drought, ultraviolet radiation, and other stresses for developing crop cultivars that can withstand climate change better than current cultivars. Modeling of the economic impact of climate change scenarios on forest inventories in the southern U.S. is also in progress.

Global change, particularly changes in land use, can have substantial impacts on the preservation of species diversity. Landsat images of Brazil, for example, have shown a large increase in the fragmentation of the habitat, a process that could reduce the number of plant and animal species (biodiversity). The area shown to be severely fragmented, and hence with potentially diminished biodiversity, was more than twice the area actually deforested.

Societal Impacts and Adaptation

Various sectoral analyses are planned to evaluate the consequences of climate change on human society. To meet the commitments of the President's Climate Change Action Plan, there is a need for increased understanding of the ability for communities to adapt to a warmer climate and to new policies that may be imposed to address the climate change issue. Research on how consumption patterns may change with a warming climate is necessary in developing response options. For example, options for responding to possible increases in average temperatures due to greenhouse warming must contrast the reduced demand for space- heating with the increased demand for space-cooling.

Uncertainty about the adaptability of societies to global change is due in part to uncertainty about future technological change. How will industrial development, future industrial and consumer products, and technological improvements change polluting emissions, help abatement of, and lead to adaptation to environmental changes? How will the supply and demand for goods and services change? Answers to these questions have implications both for predicting future global change and for evaluating the effectiveness of national and international government policies to reduce the impacts of change. Technological innovations and changing production patterns could greatly ameliorate or exacerbate both abatement and adaptation. Research on the innovation process and the subsequent diffusion of new technologies and products will be expanded to address these issues.

Significant research is being conducted to provide information about the health effects on humans of increased UV radiation and CFC substitutes. Health studies on the effects of increased UV exposure focus on the impacts on the immune system, aging process, sensitive tissues, and methods to reduce these harmful effects. The principal objectives of these studies are to promote an increased understanding of UV effects on target organs (e.g., eyes and skin) and the molecular changes that lead to these effects, and to help develop strategies to prevent the initiation of disease or to intervene before disease.

Animal models indicate that exposure to environmentally relevant doses of UV-B radiation can adversely affect the course of certain infectious diseases. Tests show that exposure to UV-B can drastically reduce survival time after exposure to lethal agents. Other research has shown that the ability of UV radiation to impair the development of cell-mediated immunity depends on the particular antigen administered, and that DNA is the primary target of UV radiation in the generation of systemic immunosuppression.

The global implications associated with seasonal to interannual variations in the climate include potential shifts in the patterns of drought, flooding, and severe storms. These events can have unfortunate social and economic consequences in developed countries, and often have disastrous consequences in developing countries with economies that are largely dependent upon their agricultural sectors as a major source of food, employment, and foreign exchange. Experimental predictions from ENSO models can be used to provide advance warning to decision makers, which allows them to adjust the type and timing of crop planting in anticipation of anomalous climate patterns associated with ENSO events.

Mitigation Strategies

Mitigation strategy research within the focused USGCRP includes: evaluation of CFC substitutes and the environmental implications of the proposed substitutes and their degradation products; the development of models for predicting responses of major agricultural crops to climate change and the development of management tools for ameliorating undesirable effects; and studies on reforestation of presently deforested areas in the tropics.

Research on replacements for chlorofluorocarbons (CFCs) is focused on understanding potential impacts on humans and the environment. Because the toxicity of many compounds is associated with their metabolism, the metabolism and toxicity of hydrochlorofluorocarbons (HCFCs) and hydrofluorocarbons (HFCs), known collectively as H(C)FCs, are being investigated. The available data indicate that compounds that are rapidly metabolized are more toxic than those that are slowly metabolized. For example, HCFC- 132b is very rapidly metabolized and yields metabolites that are very potent inhibitors of the enzymes used by the body to detoxify many drugs and chemicals. As a result, its development has been discontinued. Other research shows that the possibility exists that HCFC-123 may increase susceptibility to hepatitis in sensitive individuals. Finally, computer modeling studies of reactions of H(C)FCs are being conducted. The objective is to develop models that will allow prediction of the rates of metabolism of H(C)FCs and identification of H(C)FCs that are likely to be poorly metabolized and, therefore, have little toxic potential. Preliminary results of this research have been very promising, and the range of compounds to be tested has been expanded.

The biospheric transport and fate of CFC substitutes are also being investigated in order to assess likely future concentrations of these new chemicals in air, water bodies, and soils. Models are being developed to predict the potential ecological impacts of the substituted chemicals and their degradation products.

To ensure a continued abundant supply of food and fiber, research is being conducted on management tools for responding to the potentially undesirable effects of climate change on agricultural productivity. This research involves the development of methods for aggregating plant-scale models to make predictions of impacts at regional scales. Improved predictions of the response of terrestrial ecosystems to changes in temperature, rainfall, solar radiation, especially UV radiation, and changes in carbon dioxide concentrations will enable the development of management strategies for mitigating the adverse impacts caused by these changes.

A pilot project is underway in a tropical area severely affected by deforestation and consequent erosion to study the restoration of the fertility of degraded soils and the improvement of forest cover. The system combines small-scale tree farming, horticulture, fodder production, and animal husbandry. Future plans include the expansion of the area to explore economies of scale, and to test new tree and crop species.

A very substantial amount of climate change mitigation research is being conducted outside of the focused USGCRP. The Mitigation and Adaptation Directory, compiled by the CENR Subcommittee on Engineering and Technology Research, reported that approximately $25 million was spent on focused mitigation and adaptation research in FY 1993 and $78 million will be spent in FY 1994. In FY 1993, about $1 billion was spent in research contributing (but not necessarily targeted specifically for mitigation) to the development of mitigation technologies and $1.5 billion is planned for FY 1994. The proposed FY 1995 budget includes about $1.5 billion in contributing research on mitigation and adaptation. As described earlier in this document, about $280 million of specifically identified activities (not part of the USGCRP budget) are planned in FY 1995 associated with the commitments to reduce greenhouse gases as part of the Climate Change Action Plan.

There is over a half billion dollars of contributing funding, outside of the USGCRP focused program, proposed for greenhouse gas mitigation-related research in FY 1995. This includes: the development of more efficient combustion systems which include clean coal technologies, advanced turbine systems for natural gas, and fuel cell systems which operate on natural gas and coal based fuels; alternative energy research, including wind, solar, geothermal and photovoltaics; research on alternative vehicles and fuels, advanced materials research for new transportation technologies; research to develop more energy-efficient appliances, space heating and cooling equipment, and energy-efficient buildings; research on improving the efficiency of electricity transmission, storage, and distribution reducing the need for new production facilities; and research on reducing greenhouse gas emissions and developing more energy-efficient processes for the chemical, petroleum refining, paper, textiles, food processing, and other manufacturing industries.

DEVELOPING TOOLS FOR ASSESSING POLICIES AND OPTIONS

The USGCRP plans to expand its support of research designed to advance knowledge of the ways that human activities affect natural systems and the global environment. More support also will be given to research on the ways that changing environmental conditions affect humans and the many activities in which they engage. Just as humans influence global change through their activities, individuals and organizations can influence global change by making decisions that would enable them to reduce adverse impacts on the environment and to adapt more successfully to changing environmental conditions. The USGCRP will increase emphasis in FY 1995 on developing tools for assessing policies and options for dealing with global change (see Accomplishments in Developing Tools for Assessing Global Change Policies and Options).

A new emphasis will be placed on the examination of policies in innovative modeling frameworks to identify options that are available for responding to global change, and to analyze the relative strengths and weaknesses of those options. In order to be of more assistance to governments, USGCRP results need to be better communicated in a way that contributes directly to the formulation of domestic policy and to the development of international protocols and conventions. Enhanced research on assessing policies and options, therefore, will involve leading social, economic, and policy scientists, whose expertise is necessary to understand the dynamics and interactions of human activities with global change, and whose collaboration with natural scientists and engineers is required to develop effectively integrated tools and models. Such collaboration is essential for addressing issues such as predicting the diffusion of new energy-conserving technologies, refining feedbacks within general circulation models that link human-generated emissions with climate, and identifying management strategies that can help preserve natural resources and biodiversity.

In addition to conducting fundamental research on processes through which governments and other human institutions examine policies and options, the USGCRP will promote development of new analytic and decision-making tools and the collection of critical information needed in policy- and decision-making processes. Furthermore, the USGCRP will foster more thorough evaluation of adaptation and mitigation technologies. Most importantly, the USGCRP plans to accelerate the development of methods for conducting integrated assessments, and assist in the conduct of some focused national and international assessments on differing time and spatial scales.

The USGCRP's special emphasis on assessing policies and options in FY 1995 is based on improved communication among researchers and policy makers. New forms of cooperation, such as innovative partnerships among researchers and policy makers in different Federal agencies as well as in academia and the private sector, will be expanded and enhanced. To facilitate cooperative work, funding cycles and proposal reviews across agencies will be coordinated more closely.

Social, Economic, and Policy Science Research

A major part of the USGCRP's expanded research effort in FY 1995 will consist of increased research in the social, economic, and policy sciences. Among the most important uncertainties that researchers need to address are the processes through which people become aware of changes in environmental conditions and the ways that they change their behavior in response to those changes through voluntary and coordinated actions. While some effort will be focused on the dynamics of individual decision making, more emphasis will be given to exploring the ways that responses to environmental change are channeled through economic, political, and legal systems as well as through informal organizational structures.

Better knowledge of human-environmental interactions over longer time periods is needed. Many economic models, for example, rely on information gathered by observing the behavior of individuals or groups under specific circumstances. These perspectives are valuable, but they need to be augmented with understanding derived from longer-term anthropological, geographic, and sociological perspectives in order to more fully appreciate the implications of global change on people during the coming decades. Similarly, the changing nature of political institutions and protocols for developing international agreements may differ significantly in the future.

Special emphasis in the USGCRP during FY 1995 will be given to exploration of the processes through which policies are developed, implemented, and evaluated. Policy science research will examine the ways through which policy questions are framed, including the procedures through which the values of different resources and conditions are established. Different disciplines employ different methods for assigning values, and comparison of these approaches is necessary to determine how the concerns of different stakeholders may be reconciled. Attention also will be given to procedures through which different governments or other kinds of organizations work together to achieve common objectives. Through such research, policy science can provide insights into new approaches that may achieve a more lasting consensus.

Policy science research also will focus on the data, analytic, modeling, and computational needs of policy analysts. The appropriate elicitation and utilization of expert judgments to help fill crucial information gaps will be evaluated. Analytic approaches to be explored include the extraction of general information from case studies, identification of mechanisms for estimating parameters in models, and evaluation of the degree to which assumptions have been maintained in the development and validation of models.

Integrated Assessment Capabilities

The FY 1995 USGCRP budget proposes a marked increase in its support of activities to improve integrated assessment capabilities. These activities will support the policy process by bringing scientific research results into frameworks that are useful to national and international decision makers. The integrated frameworks will also identify priorities for natural and social science research programs by highlighting critical gaps in knowledge. Once they have been developed, integrated assessment procedures will help policy makers to carefully evaluate the potential implications of different options. For example, not only will decision makers be able to evaluate the direct and indirect impacts of new technologies on future greenhouse gas emissions, they also will be able to assess how different policies are likely to affect the rates at which new technologies are adopted.

Improvements in integrated assessment capabilities require investments in both integrated models and in the research that provides the foundation on which models are based. Integrated models that can be used to conduct comprehensive assessments and evaluate policies and other options require adaptation of reduced- form models, which are already under development for many natural systems. They also will require development of accounting mechanisms that will enable non-monetary factors to be included. New insights into integrated assessment modeling are resulting from evaluating modeling approaches that have already been developed and tested.

Some of the research to advance integrated assessment modeling capabilities will occur inside the Federal agencies, but most will be undertaken in academic and private-sector organizations. In addition to advancing methodological capabilities, case studies of their effectiveness will be undertaken. The impact of the Administration's Climate Change Action Plan for mitigating greenhouse gas emissions will be evaluated in order to provide a foundation for subsequent actions. Benefit-cost analyses will also be conducted of recommendations in Policy Implications of Greenhouse Warming, a 1991 study of the National Academy of Sciences undertaken in response to a provision of the Energy Policy Act.

The potential utility of integrated assessments already has been demonstrated through research on different strategies to reduce greenhouse gas emissions. A comparison of several models indicates that the use of carbon taxes to stabilize carbon dioxide emissions at current levels (by the year 2000) could result in costs of between 0.1% and 0.5% of the gross domestic product (GDP). The same models predict that a reduction of 20% in carbon dioxide emissions by 2010 could have associated costs of from 1.0% to 1.7% of the GDP. However, these models do not include the consideration of options such as the use of trees to sequester carbon. Research has shown that forestry options that encourage tree planting, although perhaps limited in scope, have costs that compare favorably with actions such as energy conservation and conversions to less carbon-intensive fuels. These models also assume that the revenues from the carbon taxes are redistributed in a neutral manner. However, recent research has shown that revenues from carbon taxes can be "recycled" in ways that can decrease GDP costs by offsetting other taxes. Finally, these analyses did not consider the recognized potential for improved market performance to provide emissions reductions at lower or possibly negative costs. Further research on these models is proposed for FY 1995.

Decision Tools and Information

An important area of USGCRP emphasis in FY 1995 will be the continued development of decision tools and analytic approaches to assist both short- and long-term needs of decision makers. In recognition of the fact that many responses to global change must be made at regional to national levels, many of these tools need to be local in character. Because of their sharply defined focus, these tools can be developed, tested, and disseminated quickly. As a result, many new decision tools can be directly employed to address specific problems while subsequent research assesses the degree to which they can be adapted for broader purposes. These new tools will enable national and international decision makers to address competing objectives and to analyze potential trade-offs among available options. There is particularly high demand for new decision tools that can be used in coastal zone management. Management of fisheries, flooding, erosion, water quality and allocation, and sea-level rise in coastal settings requires the development of adaptive strategies.

Recent successes in the refinement of decision-support tools have been possible through advances in knowledge of critical natural processes. As understanding of the frequency and scale of physical phenomena has increased, decision tools have been refined to reduce uncertainties about the socioeconomic consequences of environmental changes. One example is the improved predictive accuracy of the onset of an ENSO event. Using more accurate forecasts, resource managers have been able to alter management strategies for water use and agricultural practices to reduce economic impacts.

Another example of the value of improved decision tools is the incorporation of site-specific scientific information into economic models. Using new methods, regional distributions of environmental risks can be mapped more accurately, thereby assisting in urban planning and selecting locations for new transportation corridors and industrial facilities. Probability models are examples of successful decision tools which can, as an example, estimate the human impacts of severe rainstorms that reduce the stability of hillslopes. These models demonstrate how site-specific data applied in a regional context can assist emergency-response managers in prioritizing locations for evacuations when rainstorms become severe.

Resource Use and Management Tools

An important area of research in FY 1995 will be on resource use and management related to global change. This line of research directly supports the pursuit of sustainability. Resource issues are location and scale dependent, and numerous advances have been made in knowledge of the ways that resources are used and managed in local and regional settings. Many advances have resulted from more sophisticated use of remotely-sensed data (see figure). Important improvements have been made in the interpretation of satellite imagery for different areas where tropical rainforests abound, for example. When coupled with field-based studies of land-use and forest-regeneration processes, more complete understanding has been achieved of the successive stages of vegetation on sites where trees have been cleared or on which biomass burning has occurred. This research has shed light on natural, demographic, economic, and social factors that result in much more rapid regeneration in some locales than in others. This kind of knowledge is useful for designing more effective land use policies.

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