Strategic Plan for the
Climate Change
Science Program
Final Report, July 2003

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Vision for the Program and Highlights of the Scientific Strategic Plan

Acronyms, Abbreviations,
and Units

Footnote 1

Parenthetical references indicate the chapter and question where additional information on this research can be found.

Footnote 2

"On a periodic basis (not less frequently than every 4 years) the Council, through the Committee, shall prepare and submit to the President and the Congress an assessment which:

1. Integrates, evaluates, and interprets the findings of the Program and discusses the scientific uncertainties associated with such findings,

2. Analyzes the effects of global change on the natural environment, agriculture, energy production and use, land and water resources, transportation, human health and welfare, human social systems, and biological diversity; and

3. Analyzes current trends in global change, both human-induced and natural, and projects major trends for the subsequent 25 to 100 years."

(from Section 106).

Chapter 2 describes the Climate Change Science Program's (CCSP) overall approach to climate research on different components of the Earth system and the integration of this research to achieve Program objectives. This chapter expands on CCSP's five goals (see Chapter 1 and Box 2-1), including a brief overview of current scientific understanding, and illustrates the relationship between these goals and the Program's interdisciplinary research elements and cross-cutting activities. Tables listing topics to be covered by CCSP synthesis and assessment products are included and indicate the target time frame for completion of each product. These products will fulfill the requirements for updated synthesis and assessment contained in Section 106 ("Scientific Assessment") of the Global Change Research Act of 1990.

This chapter of the plan also includes research products, milestones, and activities, which are grouped under research focus areas for each goal. These are given here as examples and are not meant to constitute exhaustive lists; completion dates are not provided in this chapter, but are in related discussions in Chapters 3-9, and range from 2004 to beyond 2007 (greater than 4 years). Other sections of this chapter discuss integration of research to give a comprehensive picture of the cumulative effects of natural processes and human activities on the future evolution of climate and related systems.

CCSP's goals span the chain of climate-related issues including natural climate conditions and variability; forces that influence climate; cycles and processes that affect atmospheric concentrations of greenhouse gases and aerosols; climate responses; consequences for ecosystems, society, and our Nation's economy; and application of knowledge to decisionmaking. This comprehensive characterization provides a useful organizing scheme for examining key climate change issues. CCSP research must focus on the full range of these complex issues if it is to lay the basis for informed discussion and decisionmaking.

The following text explains the five CCSP goals. The discussion of each goal includes a set of topics to be addressed by synthesis and assessment products related to the goal during the next 4 years (see also section 4 of this chapter), and examples of key research activities to be carried out in moving toward the goal, with links to the discussion of research activities in subsequent chapters. Near-term synthesis and assessment products will draw on a large body of research either already completed or currently underway throughout the CCSP, in addition to new research results as they become available. Over time, CCSP research activities and the development of new synthesis and assessment products will evolve in partnership, as scientific research progresses and as new questions related to policymaking, planning, and adaptive management arise.

The climate system is highly variable, with average conditions changing significantly over the span of seasons, years, decades, and even longer timescales. Examining the period since the industrial revolution, when human activities started to significantly alter the Earth's land surface and increase the atmospheric concentrations of greenhouse gases (GHGs) and aerosols, an increasing body of evidence gives a picture of a warming world and other related changes. A key issue is whether there is a cause and effect relationship between these developments. The Intergovernmental Panel on Climate Change (IPCC) and the National Research Council (NRC) have independently concluded (in the words of the NRC) that "changes observed over the last several decades are likely mostly due to human activities," but that "a causal linkage between the buildup of greenhouse gases in the atmosphere and the observed climate changes during the 20^th century cannot be unequivocally established" (NRC, 2001a). Uncertainty about natural oscillations in climate on scales of several decades or longer and inconsistencies in the temperature profiles of different data sets are critical scientific questions that must be addressed to improve confidence in the understanding of how and why climate has changed.

El Nino-Southern Oscillation (ENSO) is a widely-recognized, large-scale climate oscillation in the equatorial Pacific Ocean that changes phase every few years, with significant implications for resource and disaster management. There are other climate cycles that last decades, centuries, and even millennia, as revealed in studies of the Earth's climate history. Recently improved (but still imperfect) capacity to forecast ENSO has yielded significant benefits in the United States and other countries, enabling decisionmakers to prepare for impacts.

Improved data and information on the climate system's natural variability and recent changes are needed to increase confidence in studies that seek to detect and attribute changes in climate to particular causes. Expanded observations, modeling, and data/information system capabilities will also improve society's ability to respond to the fluctuations and changes in the environment -- whether natural or human-induced -- that the nation and the world will face in the next 20 to 30 years and beyond. Substantial amounts of data are already collected through both an extensive observations system developed under the USGCRP and a set of operational monitoring systems used for weather forecasting and other uses (that historically were not identified as part of the USGCRP). New technologies can extend existing observation and monitoring networks and improve accessibility to these data, with benefits for both scientific understanding and resource management.

Focus 1.1: Better understand natural long-term cycles in climate (e.g., Pacific Decadal Variability (PDV), North Atlantic Oscillation (NAO)).

Focus 1.2: Improve and harness the capability to forecast El Niño-La Niña and other seasonal-to-interannual cycles of variability

Focus 1.3: Sharpen understanding of climate extremes through improved observations, analysis, and modeling, and determine whether any changes in their frequency or intensity lie outside the range of natural variability

Focus 1.4: Increase confidence in the understanding of how and why climate has changed

Focus 1.5: Expand observations and data/information system capabilities

Combustion of fossil fuels, changes in land cover and land use, and industrial activities produce greenhouse gases and aerosols and alter the composition of the atmosphere and important physical and biological properties of the Earth's surface. For example, the atmospheric concentration of carbon dioxide (CO₂) has increased approximately 30 percent since the mid 18^th century (see Figure 2-2). The current level of atmospheric carbon dioxide (CO₂) has not been exceeded during at least the past 420,000 years (the span measurable in ice cores). Atmospheric concentrations of other greenhouse gases [methane (CH₄), tropospheric ozone (O₃), nitrous oxide (N₂O), and halocarbons (e.g., chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), and hydrofluorocarbons (HFCs))] have also increased. For example, methane concentrations have more than doubled and the concentrations of industrially produced molecules have increased against a zero natural background. In the case of chlorine, the amount of chlorine in the stratosphere has essentially quintupled due to this human release.

These changes have several important climatic effects. Greenhouse gases (which remain in the atmosphere for years to millennia) have a warming influence on climate, while aerosols (which usually remain in the atmosphere for weeks to months) have both warming and cooling effects that can be quantified only poorly at present (see Figure 2-3). Research conducted as part of the CCSP will reduce uncertainty about the sources and sinks of GHGs and emissions of aerosols and their precursors, their climate effects, and the implications of controls on aerosol emissions for both climate and air quality at regional and local scales.

Figure 2-3: Global mean radiative forcing of the climate system and degree of certainty (see Chapter 3 and the Figure 3-2 Annex C entry for more detail). Source: Adapted from IPCC (2001a).

Changes in land cover and use affect climate directly, for example by altering the Earth's albedo, or reflectivity. They also affect ecosystems and biological processes that contribute to carbon sources and sinks, emissions of other greenhouse gases, and the potential for land use changes to alter regional hydrology. Several CCSP initiatives, including accelerated research on the carbon cycle under the CCRI, will develop needed information for policymaking and improved carbon management.

Emissions of some sets of industrial compounds also contribute to depletion of the stratospheric ozone layer and increased exposure to ultraviolet radiation (which contributes to skin cancers, eye diseases, and possibly other environmental problems). Many of these same ozone-depleting gases are also significant greenhouse gases. The CCSP will monitor the recovery of the ozone layer and long-term changes in the industrial compounds and stratospheric conditions that bring about stratospheric ozone depletion.

Future human contributions to climate forcing and potential associated environmental changes will depend on rates and levels of population change, economic growth, development and diffusion of technologies, and other dynamics in human systems. These developments are unpredictable over the long timescales relevant for climate change research. However, "If..., then..." scenario experiments, if carefully constructed, can make it possible to explore the potential implications of different technological, economic, and institutional conditions for future emissions, climate, and living standards. Improving the approach to developing and using these scenarios, in cooperation with the Climate Change Technology Program (CCTP), is a priority for the CCSP. The program will work with the CCTP to explore the climate and related implications of different technology portfolios in order to provide information for decisionmaking and to enable the United States to continue its work within the United Nations Framework Convention on Climate Change. In conjunction with research on the carbon cycle and other biogeochemical cycles, improved scenario-based analyses hold the promise of increasing our understanding of potential future forcing of climate, as called for by the NRC.

Focus 2.1: Reduce uncertainties about the sources and sinks of GHGs, emissions of aerosols and their precursors, and their climate effects

Focus 2.2: Monitor the recovery of the ozone layer and improve the understanding of the interactions of climate change, ozone depletion, tropospheric pollution, and other atmospheric issues

Focus 2.3: Increase knowledge of the interactions among emissions, long-range atmospheric transport, and transformations of atmospheric pollutants, and their response to air quality management strategies

Focus 2.4: Develop information on the carbon cycle, land cover and use, and biological/ecological processes by helping to quantify net emissions of carbon dioxide, methane, and other greenhouse gases, thereby improving the evaluation of carbon sequestration strategies and alternative response options

Focus 2.5 Improve capabilities to develop and apply emissions and related scenarios for conducting "If..., then..." analyses in cooperation with the CCTP

While there is a great deal known about the mechanisms that affect the response of the climate system to changes in natural and human influences, many basic questions remain to be addressed. There is also a high level of uncertainty regarding precisely how much climate will change overall and in specific regions (see Figure 2-4). Current models project significantly different increases in global average surface temperature, from approximately 1^oC to more than 5^oC during the 21^st century. This range of uncertainty incorporates both different estimates of climate sensitivity (the increase in temperature that results from a doubling of atmospheric concentrations of CO₂ for example) and a wide range in projections of future greenhouse gas emissions. A primary objective of the CCSP is to build on existing information and scientific capacity to sharpen qualitative and quantitative understanding through observations, data assimilation, and modeling activities.

CCSP-supported process research will address basic climate system properties and interactions, including improving characterization of the circulation and interaction of energy in the atmosphere and oceans. It will also seek to reduce uncertainties regarding a number of "feedbacks" or secondary changes caused by the initial influence that can either reinforce or dampen the initial effect of greenhouse gases and aerosols. These feedbacks include changes in the amount and distribution of water vapor, changes in extent of ice and the Earth's reflectivity, changes in cloud properties, and changes in biological and ecological systems that could significantly change emissions or absorption of greenhouse gases (see Figure 2-5).

Figure 2-5: Major components needed to understand the climate system and climate change. Source: Adapted from IPCC (2001a).

A cause for concern about which there is considerable uncertainty is the potential for changes in extreme events, and rapid, discontinuous changes in climate. Such changes could have profound effects on the environment and human well-being because the time available for adaptation would be limited. The historical record of past climates revealed through the study of ancient ice cores and other paleoclimate data indicates that the climate system can change relatively rapidly in response to internal processes or rapidly changing external forcing. Increasing our understanding of the conditions that could give rise to events such as rapid changes in ocean circulation is a key aspect of CCSP-supported research.

Incorporation of this basic process-level knowledge into climate and ecosystems models holds promise for improving our ability to forecast and project climate phenomena. Climate models seek to quantitatively simulate the behavior of the climate system and its response to changes in forcing. They vary in complexity and uses, but in the most complex, various components of the climate system (atmosphere, oceans, biosphere, hydrosphere, and cryosphere) are coupled together to study the evolution of the entire Earth system. Research indicates that there are limits to the predictability of regional and local scale phenomena. At this point, modeled projections of the future regional impacts of global climate change are often contradictory and are not sufficiently reliable tools for planning. Alternative methods such as use of climate analogue scenarios and weather generators may sometimes be employed for these purposes.

Focus 3.1: Improve characterization of the circulation of the atmosphere and oceans and their interactions through fluxes of energy and materials

Focus 3.2: Improve understanding of key "feedbacks" including changes in the amount and distribution of water vapor, extent of ice and the Earth's reflectivity, cloud properties, and biological and ecological systems

Focus 3.3: Increase understanding of the conditions that could give rise to events such as rapid changes in ocean circulation due to changes in temperature and salinity gradients

Focus 3.4: Accelerate incorporation of improved knowledge of climate processes and feedbacks into climate models to reduce uncertainty in projections of climate sensitivity, changes in climate, and related conditions such as sea level

Focus 3.5: Improve national capacity to develop and apply climate models

Seasonal to annual variability in climate has been connected to impacts on almost every aspect of human life: agricultural yields, water resources, energy demand and supply, transportation, price fluctuations, fishery yields, forest fires, human health and welfare, and many others. Long timescale natural climate cycles and potential future human-induced changes in climate could have additional effects, including altering the lengths of growing seasons, the sustainability of water resource management systems, the geographical ranges of plant and animal species, biodiversity, estuarine and ocean productivity, and the incidence of disturbance regimes that affect both natural and human-made environments. Potential benefits and risks have been identified for a number of systems and activities. Improving our ability to assess potential vulnerability and resilience to future variations and changes in climate and environmental conditions could enable governments, businesses, and communities to reduce negative impacts and seize opportunities to benefit from changing conditions by adapting infrastructure, activities, and plans.

The potential effects of climate variability and change on ecosystems and human activities will not be determined solely by their sensitivity and adaptability, but also by multiple, cumulative interactions among physical, ecological, economic, and social conditions. For example, some crops and plants that might otherwise experience reductions in productivity as a result of changes in climate alone could actually experience increased growth and productivity as a result of increases in atmospheric CO₂ concentrations and nutrients (from deposition and runoff). Other species and ecosystems, which could to adjust to climate change alone, might be endangered when land use and other factors interfere with adaptive mechanisms such as migration. Interacting factors must be identified and understood to develop accurate projections of effects. The CO₂ "fertilization effect" (increased plant growth due to higher atmospheric CO₂ concentrations), nitrogen deposition, disturbance (e.g., fire, pest infestations), land cover fragmentation (see Figure 2-6), air pollution, and other factors affect the functioning (e.g., water use efficiency, biomass allocation) and composition of natural and managed ecosystems over long periods of time. Similarly, estuarine and coastal ecosystems face multiple-stressor problems associated with point source and non-point source pollution, increased sedimentation resulting from poor land-use practices, invasive species and sea-level rise. Multiple stressors affecting marine ecosystems include natural climate variations (e.g., ENSO and PDV cycles), fishing, and changes in ocean productivity brought on by uncertain causes. The interactions are even more complex when one examines the interactions of biophysical and socioeconomic systems. CCSP research will examine the implications of multiple interacting changes to improve projections of effects.

Figure 2-6: Land cover maps of the Chicago Metropolitan Region. These maps, created with LANDSAT imagery from 1972, 1985, and 1997, document changes in several categories of land cover and land use. Source: NASA and Y.Q. Wang, University of Rhode Island.

Evaluation of the potential impacts associated with different atmospheric concentrations of greenhouse gases and aerosols is an important input to weighing the costs and benefits associated with different climate policies. Further research is required to integrate still limited understanding of effects of different concentration levels, and the influence of human activities on concentrations, and to develop methods for aggregating and comparing impacts across different sectors and settings.

Focus 4.1: Improve knowledge of the sensitivity of ecosystems and economic sectors to global climate variability and change

Focus 4.2: Identify and provide scientific inputs for evaluating adaptation options, in cooperation with mission-oriented agencies and other resource managers

Focus 4.3: Improve understanding of how changes in ecosystems (including managed ecosystems such as croplands) and human infrastructure interact over long periods of time

The first four CCSP goals focus on the key issues of understanding natural climate conditions and variability, forces that influence climate, climate responses, and implications for human systems and natural environments. CCSP research will focus on this full range of issues in order to lay the basis for informed discussion and decisionmaking. The fifth CCSP goal focuses on the way that this scientific information is used for support of decision needs.

Over the last decade, the USGCRP has enlisted federal and external experts to develop a variety of products and resources for decision support. These include methods and tools for integrated assessment (including a variety of quantitative integrated assessment models); state of science syntheses and assessments of climate variability and change; international assessments of stratospheric ozone depletion; applications of Earth science observations and data; experiments for application of ENSO forecasts in a variety of regions and economic sectors; and advisory committee assessments of the potential vulnerabilities and opportunities arising from climate change in different regions and sectors of the United States.

These products of the first decade have evoked much commentary, both positive and negative. Formal evaluations of the processes and products of some of these activities have been conducted by the NRC. CCSP's decision support activities will respond to the relevant recommendations of the NRC in reports such as Global Environmental Change: Research Pathways for the Next Decade (NRC, 1999a), Climate Change Science: An Analysis of Some Key Questions (NRC, 2001a), and The Science of Regional and Global Change: Putting Knowledge to Work (NRC, 2001e). The Program will also encourage further evaluation and learning from these experiences in order to structure decision support processes and products that use existing knowledge to the best effect while communicating the limits of this knowledge.

CCSP activities in support of its fifth goal will improve the nation's and global community's understanding of the nature and extent of the challenges inherent in climate change and develop improved resources for evaluating options for adaptation and mitigation. Fulfilling this goal will require development of a variety of resources including observations, databases, data and model products, scenarios, a variety of visualization products, and improved approaches for interacting with users. Research in many of the program elements holds promise of yielding decision support information and products. Improved resources for decision support also require a concerted focus on the processes through which information is developed and applied to support decisionmaking in different areas.

Areas of decisionmaking to be supported by the CCSP include adaptive management, planning, and policy. Each of these categories will have its own unique set of stakeholders and will require different decision support processes and tools that will be recognized in the implementation of CCSP decision support activities. CCSP will engage both decisionmakers and members of the research community in the development of processes well suited to both the state of science and decisionmaking needs. In addition to supporting decisionmaking, the decision support activities of the CCSP will also help to identify key knowledge gaps and provide feedback to researchers that will guide the evolution of the CCSP agenda.

Focus 5.1: Support informed public discussion of issues of particular importance to U.S. decisions by conducting research and providing scientific synthesis and assessment reports

Focus 5.2: Support adaptive management and planning for resources and physical infrastructure sensitive to climate variability and change; build new partnerships with public and private sector entities that can benefit both research and decisionmaking

Focus 5.3: Support policymaking by conducting comparative analyses and evaluations of the socioeconomic and environmental consequences of response options

The interdisciplinary research elements of the CCSP partition the overall Earth system and the issue of climate change into discrete and manageable sets of research problems. While partitioning the problem is necessary for both research and program management purposes, it carries with it the potential to divert attention from critical questions that are beyond the scope of the individual research elements, instead emphasizing lower priority issues that reside completely within a single research area. Thus, a key challenge facing the CCSP is engaging in integrated planning that "puts back together" the pieces of the Earth system and fosters problem-driven interdisciplinary research. This is especially true for "critical dependencies," topics for which progress in one research element is only possible if related research is first completed in other areas. The CCSP will need to foster integration across research elements and disciplines; among basic research and supporting activities such as observations, modeling, and data management; in the development of comprehensive climate models; and between participating departments and agencies if it is to achieve its objectives.

Scientifically, integration is essential for understanding how the Earth system functions and will evolve in response to future forcing. This is because of the inherent interconnectedness among components of the Earth system. In particular, the existence of feedback loops in the Earth system creates the need to work across disciplinary boundaries. For some issues, it will be necessary to coordinate and integrate across all of the CCSP program elements. One example that illustrates how the different research elements may help address a key uncertainty is given in Box 2-2, focused on the question of the evolution of the global distribution of atmospheric methane.

Because the components of the Earth system interact continuously, research in one program element often has a critical dependency with work in other elements. Critical dependencies can involve insights from process studies, data flows, model components, and other research and operational activities.

The most obvious set of critical dependencies is in the area of observational data. In many cases, observations of the underlying physical state of the Earth system (e.g., temperature, precipitation history) are required before questions about climate or global change can be addressed. Another example is information on land cover and land use, which also forms the basis for many studies of hydrology, biogeochemical cycling, and ecosystems research. Chapters 3-9 describe both the inputs that each research element needs from other program elements and the products that each expects to produce to support goals in other research areas. A challenge for the CCSP will be to coordinate production of information required to satisfy these critical dependencies so that they meet requirements and are sequenced properly. The CCSP will coordinate development of implementation plans for the research elements to meet this challenge. Box 2-3 lists illustrative examples of "Critical Dependencies" from the research elements.

Just as meeting the objectives of the CCSP will require integration across the research elements described in the ensuing chapters (3-9), so will it require coordination and integration of the different approaches employed by the scientific community in addressing these major challenges -- basic research, surface-based networks, field-based process studies, global satellite observations, computational modeling, data management, assessment, and decision support. It is worth emphasizing that many of the surface-based networks and some of the global satellite observations are carried out as part of operational monitoring programs not previously considered as part of the USGCRP, and which may not even now be identified in the CCSP budget. Clearly, our nation's effort to provide comprehensive, integrated answers to the questions posed in this plan will require integrated use of all such data and approaches.

Basic research provides the intellectual framework of the entire global change research enterprise. From laboratory descriptions of critical physical, chemical, and biological processes, to determination of appropriate standards and calibration procedures, to approaches for simulation, analysis, visualization, etc., of data, research serves as the basis on which advances in observing and modeling depend. It also includes the necessary social science and related research that provides the data and models needed to include effects of human inputs and response into the CCSP program.

Surface-based monitoring networks provide a distributed, accurate, and potentially high-frequency method for obtaining environmental data. They also allow the network managers to concentrate observing power in regions where it is most needed. As noted above, many of these are managed as part of operational monitoring programs and do not report as part of the USGCRP. They also provide critical validation information for satellite-derived observations.

Field-based process studies allow the combined use of surface-based measurements and transportable platforms (ships, aircraft, balloons, etc.), and also provide opportunities to define intermediate spatial scales between the local scales best studied with surface-based networks and the larger spatial scales typically observed with satellite instruments. By virtue of being able to comprehensively sample a large number of environmental variables associated with a particular issue, they are excellent for providing data sets that can be used to quantitatively test process models that ultimately support the development of parameterizations that can be incorporated into larger-scale models.

Global satellite observations allow for frequent observations over most if not all of the Earth's surface, and allow one to make measurements in regions for which in situ data are not available. Successful implementation of satellite observing programs requires validation with surface-based networks and with more focused in situ observations. Process representation in models will be derived from knowledge gained in the field-based process studies. It is important that research observations be integrated with those of operational monitoring programs not traditionally considered part of the USGCRP.

Computational modeling provides a way in which information about the potential future of one or more elements of the Earth system can be expected to evolve, based on assumptions about naturally-occurring and human-induced forcings. The models to be used in this way can be tested in a retrospective sense by comparing observed data on Earth system evolution (obtained from surface- and space-based observing systems as well as field-based process studies) and the known forcings; conversely, the models can also be used in an inverse set with the observations to infer present and historical forcings. Computational models can also be integrated with observational data in data assimilation systems to provide accurate and geophysically (and increasingly biogeochemically) consistent data sets of the distribution and fluctuations of key environmental variables. The assimilation process is also critical for initializing the global models and for their evaluation.

Data management is a critically important component of the CCSP for two reasons. First, it is necessary to provide active, long-term stewardship for the large volumes and multiplicity of types and sources of data. Second, it provides the means to distribute the data to a growing group of users, going far beyond the traditional scientific research community to the broader set of users who are making the policy and resource management decisions.

Scientific assessment provides the opportunity for researchers to go back and critically assess the status of their knowledge, sharpen the questions they are trying to answer, and then provide a "feedback loop" to the research process so that the research of the future will better identify and address key uncertainties and knowledge gaps. Part of the assessment process may involve detailed study of the observational data sets, process knowledge, or modeling systems developed under the CCSP to resolve discrepancies and competing approaches. End-to-end assessment is broader in that it can involve going back to the basic building blocks of a research area, assessing status and progress, and then looking at the implications of the results of this analysis for a variety of end states, including many relevant decision support applications. Assessment used to support decisions is an iterative analytic process that engages both researchers and interested stakeholders in the evaluation and interpretation of the interactions of natural and socio-economic systems. These assessments typically consist of four elements: problem formulation, analysis, characterization of consequences, and communication of results.

Decision support is the set of processes that includes interdisciplinary research, product development, communication, and operational services that provide timely and useful information to address challenges and questions confronting those who need to make policy and/or resource management decisions. In addition to the emphasis on the quality and robustness of scientific information for providing decision support, there is typically a premium on timeliness, resolution, comprehensiveness, and effective communication of levels of scientific confidence and certainty.

Computational models are particularly important in integrating our knowledge of the Earth system, providing both a quantitative way of assessing the accuracy of the system and of projecting its future evolution (see Figure 2-7). It is important that the models used for projecting future conditions include the full range of processes linking the Earth system's components, and thus the feedback processes that are so important in determining the Earth's behavior. Such models become complex, requiring the integration efforts of large teams of scientists (both Earth system scientists and computational scientists), and require significant amounts of computing capability, together with human and data resources for the archiving and distributing of their results.

Figure 2-7: The development of climate models over the last 25 years showing how the different components are first developed separately and later coupled into comprehensive climate models. Source: IPCC (2001a).

These models should have a number of important attributes:

Within the CCSP, multiple agencies have responsibilities in a number of the areas outlined above, so it is crucial that the agencies work together to optimize results, minimize duplication, and capitalize on their expertise, experience, and capabilities. The way in which this will be done is outlined in detail in Chapter 16 for federal agencies, while the relationship between U.S. and international activities is discussed in Chapter 15. The details of the CCSP structure, including the creation of interagency working groups, community-based science steering groups, and management-level interactions within the CCSP agencies and at higher levels are explained in Chapter 16.

In this section we note as examples some of the things that agencies working together through the CCSP will strive to do to assure the necessary linkages between program elements:

The CCSP will provide a variety of synthesis and assessment products on an ongoing basis as discussed. These products will support both policymaking and adaptive management. The overall approach to decision support is described in Chapter 11 of this Plan. This section integrates the earlier discussion in this chapter and summarizes the synthesis and assessment products that the CCSP will generate.

The 1990 Global Change Research Act provides the overall framework for the conduct and management of the interagency research program on climate and global change, and Section 106 of the act defines requirements for scientific assessments.² To comply with the terms of Section 106, the CCSP will produce assessments that focus on a variety of science and policy issues important for public discussion and decisionmaking. The assessments will be composed of syntheses, reports, and integrated analyses that the CCSP will complete over the next 4 years. The subjects to be addressed are listed in Table 2-1. This approach takes account of the need for assessments on the full range of issues spanning all CCSP objectives and will provide a "snapshot" of knowledge of the environmental and socioeconomic aspects of climate variability and change. The products will support specific groups or decision contexts across the full range of issues addressed by the CCSP, and where appropriate, the CCTP.

National policymaking focuses on many issues, but in this case involves integrating information from forcings and climate response to impacts and the costs and benefits of different response strategies. Synthesis of scientific data and results with economic information, demographic trends, technical specifications, etc. is essential for producing useful information on responding to the challenges posed by climate variability and change. How much information needs to be integrated depends on the specific issue or question that is being addressed and the type of decision that is being supported.

One highly important issue to be addressed at a national level is the challenge of developing new technologies to reduce the projected growth in greenhouse gas emissions. This requires integrating information from the natural sciences, engineering, and the economic and social sciences. The CCSP will work closely with the CCTP in incorporating information on portfolios of different technologies in evaluations of the implications of different response options through "If..., then..." scenario analyses, integrated assessment, and other approaches to comparative evaluation. This will facilitate understanding needs for development of new technologies.

There are, of course, uncertainties associated with all of this information, so when knowledge is integrated, information about the degree of certainty/uncertainty associated with it must also be carried forward. CCSP's decision support activities will address this essential requirement by communicating uncertainties in a manner appropriate to the decision context. CCSP's work program also includes research to improve methods for taking account of uncertainty in research and analysis, assessing the implications of uncertainty for decisionmaking, and communicating uncertainty to different audiences.

The comprehensive structure of CCSP's goals will help to ensure that the program sponsors research and provides support for decisionmaking on the full range of issues associated with variability and change in climate and related systems.