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Research and Systematic Observation

The Second Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) finds that continuing anthropogenic emissions of carbon dioxide, methane, chlorofluorocarbons, and other greenhouse gases will lead to significant changes in climate, adverse consequences for environmental and natural resource systems, and increasing risks to and impacts on human health, water resources, coastal communities, forests, and agriculture. While the report presents many important results, it also recognizes many important uncertainties and knowledge gaps that pose significant challenges to meeting the qualifications enumerated in the Framework Convention on Climate Change (FCCC). Specifically, Article 2 notes that actions taken should achieve:

¼ stabilization of greenhouse gas concentrations at a level that would prevent dangerous anthropogenic interference with the climate system. Such a level should be achieved within a time frame sufficient to allow ecosystems to adapt naturally to climate change, to ensure that food production is not threatened, and to enable economic development to proceed in a sustainable manner.

Even though the United States is significantly cutting back spending to balance the national budget, appropriations for the U.S. Global Change Research Program have remained nearly constant, at about $1.8 billion.

This sustained high-level funding has been possible because the executive and legislative branches of the U.S. government understand the importance of global environmental change issues to ensuring our continued economic prosperity, reducing human exposure to health-related stresses, and protecting the vitality of our natural resources.

This chapter describes U.S. support of research related to improving climate predictions, assessing the impacts of climate change and the potential to mitigate and adapt to its effects, and enhancing capabilities to analyze and project the socioeconomic implications of climate change. It also reports on U.S. participation in international research efforts and U.S. capacity-building in developing countries.

Research Relating to the Prediction of Climate Change

One hundred years ago, rising CO₂ emissions spurred the Swedish scientist Svante Arrhenius to develop the first quantitative estimate of potential climate change from an enhanced greenhouse effect. That estimate is only slightly higher than current estimates for the global average change.

A central goal of the U.S. Global Change Research Program's research activities is improving regional and temporal resolution for predicting how climate will change over decades to centuries, and what its implications will be for society and the environment. The following sections and various Research Program publications describe current program efforts toward achieving this goal's six interlocking objectives.

Quantifying Natural and Human-Induced Factors Forcing Climate Change

Historical and geological records provide important insights into the natural factors that caused major changes in the climates of the past. Human activities have also been affecting atmospheric composition since the start of the Industrial Revolution more than two centuries ago. Current concentrations of CO₂ are about 30 percent above preindustrial levels as a result of the combustion of coal, oil, and natural gas and the clearing and plowing of land for cultivation. And methane concentrations are more than twice their preindustrial levels due to land- and energy-related activities.

The most important human-induced factors that are forcing climate change include gases and aerosols (small particles) that are modifying the Earth's atmospheric radiation (heat) balance. Changes in the land's surface and its vegetation are also altering the Earth's reflectivity and hydrology. Quantifying the character and trends in these climate-forcing factors is vital to understanding the causes of past changes, to predicting future changes more accurately, and to creating a basis for quantifying the effects of various mitigation options.

Recent research sponsored by the U.S. Global Change Research Program indicates that atmospheric aerosols--largely those emitted from human activities--exert a nonuniform cooling effect over the globe. On average, this effect may be counterbalancing about half of the expected warming from increased concentrations of greenhouse gases. The Research Program will continue to support studies of the cycles of greenhouse gases and of the generation and distribution of aerosols. In particular, the studies will focus on the role of terrestrial systems in carbon uptake, so as to refine understanding of the global carbon cycle. Observational studies of volcanic and solar variability will also be carried out to document the natural factors that influence climate.

Characterizing the Natural Variability of Climate

The paleoclimatic record reconstructed from ice cores and other sources of data provides evidence that the Earth's long-term climate varied significantly prior to about ten thousand years ago. Since then, long-term climate has been relatively stable, especially over the past few thousand years. It is important to understand why this is the case and what the prospects may be for returning to a significantly more variable climate.

Although long-term climate has been stable, the evidence suggests that, during the last glacial period, shorter-term climate changes occurred over just a few decades. Data from the past thousand years suggest that there have been interdecadal swings in climate, creating periods of drought in some regions and excessive moisture in others. Determining the character and causes of climate variability is thus essential as context for detecting climate changes and for determining the extent to which they are due to human activities. The national components of the international Climate Variations and Predictability and Past Global Changes program are being designed to improve understanding of natural changes in climate.

Recent research sponsored by the U.S. Global Change Research Program has provided information on past changes in the Earth's climate (from ice cores, lake-level data, and other indicators). Evidence suggests that the melting of numerous icebergs associated with glacial retreat could perturb ocean circulation patterns and result in relatively abrupt climate shifts over periods as short as decades. The research activities will even more intensively focus on interactions involving the coupled atmosphere-ocean-ice system. The coupled processes appear to be important contributors to natural variations in climate on inter- and multi-decadal time scales.

The U.S. Research Program will also sponsor studies of solar variability as a climate-forcing factor on these same time scales. Efforts will continue to reconstruct past climates of the Earth, for comparison with the warm climates being experienced today.

Quantifying Climate System Processes and Feedbacks

A quantitative understanding of the climate system and the mechanisms and feedback processes that characterize its state is essential for determining how the atmosphere, oceans, and land surface will be affected by the projected changes in greenhouse gases, aerosols, land cover, and other factors that are changing the Earth's infrared radiation balance.

Available knowledge clearly indicates that changes in the radiation balance can be amplified or moderated by various climate feedback mechanisms, including water vapor, cloud, and sea ice feedbacks. These mechanisms control how strongly or weakly climate will respond to human-induced changes in forcing factors, and how rapidly or slowly the Earth's climate will change. Reducing uncertainty about the magnitude of climate feedbacks is thus critical to more accurately predicting how climate will change in response to alternative emission scenarios for greenhouse gases, and more accurately estimating regional patterns of climate change.

New and unexpected research results in U.S.-sponsored research programs indicate that significantly more solar radiation may be absorbed by the atmosphere, particularly under cloudy conditions, than is currently predicted by theory and climate models. Because this result is inconsistent with current understanding and hence controversial, it requires further observational confirmation. If confirmed, these new findings will require understanding the processes responsible for the currently unpredicted atmospheric solar absorption and a reanalysis of the Earth's radiation balance. The end result could be a significant improvement in climate models.

Improving Model Predictions of Climate Change

Because of the historical uniqueness of the ongoing human-induced changes in atmospheric composition, predictions of future conditions for particular scenarios require the use of numerical, computer-based Earth system models. Over the past ten years, as a result of the Research Program's sponsorship, atmospheric general circulation models (GCMs) have improved significantly. More accurate simulations of past climate conditions are helping to increase confidence in the models by providing explanations for past changes and by quantifying human influences on recent climate.

These ocean and atmospheric models have strong potential for continuing advances through improved representations of critical climate processes and finer model resolution for regional-scale predictions. However, today's GCMs need to be augmented by representations of the land surface, vegetation, chemistry, and the cryosphere (glaciers, snow, and ice), and must be based on a comprehensive scientific understanding of the functioning of the climate system.

The comprehensive understanding needed to create and apply these augmented models is developing rapidly through the observational, process, and modeling studies being conducted at several U.S. modeling centers. Research in support of this objective will continue to emphasize: incorporation of carefully tested modules in climate models; enhanced use of the most powerful computers; coupling of atmospheric, oceanic, and land surface components of the Earth's system; and testing and comparison of model simulations with observations as a means to evaluate the confidence that can be placed in model results. Studies to detect human-induced climate change will also be continued with additional studies of the contributions of various factors to climate change.

Observing and Monitoring the Climate System

For the first time, the world community is capable of implementing an integrated global observing system that would provide future generations with a stronger basis for sustaining economic development while ensuring a healthy environment. Maintaining and enhancing a global observing capability are critical to the international assessments of global change needed for guiding international policymaking.

Once missed, the opportunity for direct observations will be lost forever. Delays in deploying instruments and temporary cessations of observations present significant obstacles to advances in understanding, and postpone the gathering of data necessary for identifying the trends and mechanisms causing and influencing environmental change.

Over the past few years, the scientific community has been determining what measurements are needed and how best to make the observations. The United States has been participating in the planning efforts undertaken by the international scientific committees for the Global Climate Observing System, the Global Ocean Observing System, the Global Terrestrial Observing System, and the Committee on Earth-Observation Satellites.

The U.S. Global Change Research Program is also actively involved in a cooperative international effort to design and implement a strategy for an integrated global observing system. The U.S. contribution to the satellite component of this integrated system will draw upon the resources of the National Aeronautics and Space Administration (NASA), the National Oceanic and Atmospheric Administration (NOAA), and the Department of Defense (DoD). The NASA component will be carried out through the Earth-Observing System series of satellites, the centerpiece of NASA's Mission to Planet Earth and NASA's contribution to the Research Program. The NOAA and DoD contributions will be made through their operational weather satellite programs, a future component of which is being coordinated through the National Polar-Orbiting Environmental Satellite System program. (Because their principal justification is for operational applications, these contributions are not included within the Research Program's budget.) In addition, NASA and NOAA have established joint projects with the space agencies of Canada, Europe, Japan, and Russia to acquire, process, and share the satellite environmental data collected by these agencies.

To complement the enhancement of the satellite observing system, each nation will need to monitor surface conditions within its borders. Toward this end, the Committee on Environment and Natural Resources, working through its National Environmental Monitoring and Research Initiative, is increasing the coordination of U.S. environmental monitoring and related research networks. This initiative, which is proceeding with both national and regional planning activities, is expected to begin a process that, when fully developed, will provide the needed baseline information for documenting how U.S. ecosystems are being affected by environmental fluctuations and changes over periods from seasons to decades and longer.

The meteorological and environmental monitoring networks being supported include:

• the network of surface and upper-air meteorological observation stations implemented by the United States and other nations under the aegis of the international World Weather Watch;
• the NOAA, NASA, and Environmental Protection Agency (EPA) networks of observing stations under the Global Atmosphere Watch, which provide observations of the concentrations of greenhouse gases and ozone-depleting substances;
• the internationally sponsored array of moored and drifting buoys that monitor surface and subsurface temperatures in the tropical Pacific Ocean to help detect the onset of El Niño events;
• the U.S. Department of Agriculture (USDA), Department of the Interior (DOI), and EPA networks that monitor the conditions of forests and other vegetation, soils, runoff, and water resources;
• NOAA's Surface Radiation Budget Network, which provides continuous measurements of the upward and downward components of visible and infrared radiation; and
• the UV radiation network of stations maintained by USDA, EPA, and NSF, which provide reference measurements for the United States and the polar regions that are starting to indicate the effects of ozone depletion.

Conducting Climate Assessments

Because climate is such a pervasive influence in human affairs, climate studies must be able to assemble and systematically evaluate diverse sets of information. The United States, through the U.S. Global Change Research Program, has joined other nations in participating in and supporting the IPCC as the mechanism for organizing climate change assessments.

Research Program agencies have assisted other nations in understanding their vulnerability to climate change through national studies and participation in the IPCC process. The Research Program will continue to participate actively in international assessments of climate change through the IPCC, and is planning comprehensive studies of national implications of climate change. In addition, research results will be provided to national and state-level planners and decision makers so that regional vulnerability can be evaluated.

Research on Impacts and Adaptation

Since the early 1980s, the United States has been conducting research on the potential impacts of climate change and options for adapting to those impacts. The U.S. Global Change Research Program's objective for impacts and adaptation research is to "develop improved measures of the sensitivity, vulnerability, and adaptability of natural ecological systems and managed resource systems and project the consequences of climate change and long-term variations of the climate."

Research on adaptation can be divided into two categories: (1) reactive adaptation, involving typical steps people may take in responding to changing climate (e.g., erecting dikes and switching crops); and (2) anticipatory adaptation, necessitating the enactment of policies perhaps many decades in advance of serious climate change (e.g., rolling easements that allow wetlands to migrate inland as sea level rises, or acquisition of land for future reservoir construction).

The most comprehensive research on impacts has focused on agriculture, forests, water resources, coastal zones, and human health, each of which is briefly discussed in this section. At present, more research focuses on the impacts of climate change than on adaptation options, although these two aspects may be examined in conjunction.

Agriculture and Forests

U.S. research on understanding the effects of global change on terrestrial systems includes studies of the interactions between terrestrial ecosystems and the atmosphere; the contributions of agricultural sources of methyl bromide to stratospheric ozone depletion, and possible substitutes for this fumigant; methane generation and nitrous oxide release; soil properties, including moisture, erosion, organic matter, nutrient fluxes, and microbes; the relationship of global change to forest and range fires, insects, and plant pathogens; agricultural management systems; and ground truthing of satellite measurements.

The United States also sponsors significant research on the effects of global climate change on the nation's and the world's agricultural food- and fiber-production systems, and forest and forest ecosystems. Programs include long-term studies addressing the structure, function, and management of forest and grassland ecosystems; research in applied sciences, including soils, climate, food and fiber crops, pest management, forests, fish and wildlife, and social sciences; implementation of ecosystem management on the national forests and grasslands; and human interaction with natural resources.

Water Resources

Numerous studies are under way on the effects of climate change on water resources. Overall, the studies focusing on GCM-based hydrologic sensitivity analyses and climate change vulnerability impact analyses have provided very little useful information for current water management decisions. The GCM output is still at too coarse a scale and is too inconsistent to be of value to the practitioners. Work to improve the GCMs and enhance their capabilities is under way to provide the information needed for long-term watershed planning and management, influencing design standards for levees and dams, and improving the basis for reservoir operations.

Ongoing studies of regional and national water management policies and procedures are exploring options for responding to both long-term and, more recently, short-term climate variability and resource demands. Most of the research uses a GCM-based sensitivity analysis framework, and some studies are using the latest 1995 IPCC transient scenarios.

These studies dovetail with the development of adaptive management techniques needed to complement those associated with possible larger impacts under more extreme scenarios. Hence, the U.S.-Canada Fluctuating Great Lake Levels Study, the Missouri River and Columbia River reallocation and regulation studies, the Florida Everglades Ecosystem Restoration study, and other agency initiatives reflect a heightened responsiveness to sound and innovative water management practices that strive to achieve sustainable development. Advanced methods, improved data sources, and knowledge about the interaction of ecosystems, hydrology, and climate are now being incorporated into the planning and design of comprehensive, long-term solutions. Climate variability and changes are becoming central elements of those designs and long-term plans.

Coastal Zones

The IPCC estimates that climate change is likely to add 15-95 centimeters (about 6-38 inches) to sea level by the year 2100. The United States is involved in research to further quantify sea level rise, its effects, and possible adaptive responses. Some monitoring of current trends is under way: gauges are recording tides at dozens of sites across the nation, and some coastal states are monitoring beach erosion rates.

A basic assessment of how much land and wetlands would be lost to various scenarios of sea level rise was largely completed by 1990, using scenarios of 50, 100, and 200 centimeters (20, 40, and 80 inches, respectively). The recent downward revision of sea level scenarios may imply a need to estimate the resources at risk from a 25-centimeter (10-inch) rise. Wetland erosion rates are only being monitored at a few isolated locations where erosion is unusually high, such as Louisiana and Blackwater Wildlife Refuge. More research on the ability of wetlands to keep up with an accelerating rise in sea level is necessary, and the rate at which rising sea level is leading to the replacement of natural shorelines with bulkheads should be monitored.

The implications of sea level rise for floodplain boundaries have been assessed for some specific locations. The National Flood Insurance Program has estimated the increased flood damages and flood insurance rates resulting from 30- and 90-centimeter (12- and 36-inch) rises in relative sea level. Research has also been conducted on the effects of sea level rise on saltwater intrusion in Delaware and San Francisco Bays, two of the four major U.S. water bodies whose water supplies appear to be most vulnerable to climate change. And various research grants have been provided to marine laboratories to assess the implications of warmer estuarine temperatures.

EPA has funded assessments of the cost of holding back the sea with a combination of dikes and beach nourishment, and the cost of abandoning areas due to sea level rises of 50, 100, and 200 centimeters. A new study funded by the electric power industry applies a cost-benefit model to estimate the costs of sea level rises of 33, 66, and 100 centimeters (13, 26, and 40 inches) on the assumption that areas will be abandoned or protected, depending on which is most cost-effective. And recent interest in the possibility of more intense storms along the coast has led to the Council on Environmental Quality's coordination of an interagency series of studies to better determine the vulnerability of coastal communities and the insurance industry to climate change.

The United States also is engaged in a number of assessments of how communities can best adapt to sea level rise. The U.S. Coastal Zone Management Act requires states to develop strategies for responding to sea level rise. Thus far, a number of states have only estimated the loss of land under different scenarios. EPA has conducted legal research on possible avenues for ensuring that wetlands and beaches are able to survive rising sea level by migrating inland without infringing upon the private property interests of coastal property owners. In many cases, the appropriate adaptive response depends on the probability that the sea will rise by a given magnitude. Therefore, EPA has recently developed a probability distribution estimate of future sea level rise.

Human Health

Research into the relationships between climate change and human health has focused on three areas:

• identification and analysis of recent regional and local changes in climate to establish a causal link between climate and health and as analogs for future climate change impacts;
• development and validation of methods--ranging from extrapolation of empirical epidemiological dose-response data to integrated mathematical models--to forecast health impacts of climate change; and
• incorporation of health-related measurements in global, regional, and local monitoring activities.

Researchers have taken advantage of naturally occurring short-term fluctuations in climate, such as heat waves, to examine the effects of short-term exposures to extreme temperatures on human mortality. This research is being extended to include heat-related illnesses; weather-related mortality and morbidity in winter; confounding factors, such as air conditioning use, demographic characteristics, and mortality displacement; and the potential synergistic effects of air pollution.

Similarly, the El Niño/Southern Oscillation (ENSO) phenomenon continues to be studied, both as an analog for long-term climate change and to examine health consequences. For example, ENSO-related algal blooms serve as potential "environmental reservoirs" for microbes that cause cholera in humans. Insects and rodents have increased following the mild, wet winters associated wit El Niño, with impacts occurring in areas where these animals act as pests in agriculture or as vectors for such diseases as malaria.

Integrated assessment models are being improved and expanded to cover a wider range of diseases mediated by ecological processes. For example, researchers are linking top-down health assessment models to dynamic life-history models to forecast changes in the epidemic potential of dengue-carrying mosquitos. Satellite/remote-sensing and geographic information systems (GIS) are being used to explore infectious diseases, such as Lyme disease, hantavirus pulmonary syndrome, and cholera. Field studies are also being undertaken to evaluate suspected climate-disease linkages. Efforts are under way to further clarify and validate direct weather-related impacts on human health and, where possible, to extrapolate these to expected future climate changes.

The U.S. National Academy of Sciences is beginning a study of climate, infectious disease, and health. This study will critically evaluate the data behind suspected links between climate and health; identify useful weather, climate, and ecosystem information products and tools that can assist disease prevention and mitigation efforts; and suggest a global, multidisciplinary, international research strategy. Hot-Weather/Health Watch Warning Systems have been developed and implemented to facilitate emergency responses to extreme heat. Ongoing efforts are incorporating health indicators into global observing systems, to improve existing health monitoring systems and to apply communications technology in order to gather disease data more quickly and efficiently.