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Thematic Guide to Integrated Assessment Modeling
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Section 1: Introduction
In recent years, integrated assessment of climate change has generated increasing attention. Several major integrated assessment projects have begun in recent years, and many argue that an increased capacity to do integrated assessment is one of the crucial needs for wise policy-making on climate change and on related environmental risks. Integrated assessment has been a central priority of the U.S. Global Change Research Program (USGCRP) since 1994, and large sums are proposed for the activity, both in the United States and in other nations, over the next few years. But what does integrated assessment mean, how do you do it, and how do you tell when it is done well? This guide, by surveying current and historical projects in integrated assessment and identifying common themes and problems across the work, addresses these questions in a preliminary way.What Is Assessment?
The term "integrated assessment" has prompted much fruitless definitional debate, in part because it combines two concepts that are each subject to definitional confusion: What is assessment, and what does it mean for assessment to be integrated? This guide defines assessment, in contrast to pure research, as the presentation of knowledge derived from research to help individuals with responsibilities evaluate possible actions or think about a problem. This definition is not very restrictive, because the range of possible audiences, actions to help them evaluate, or (especially) problems to help them think about is broad enough to admit a huge diversity of assessment activity.Assessment normally does not mean doing new science, but rather assembling, summarizing, organizing, interpreting, and possibly reconciling pieces of existing knowledge, and communicating them so that an intelligent but inexpert policy-maker will find them relevant and helpful in their deliberations. What this goal requires is highly context-specific. It may be a simple exercise in the clear communication of information that is well-known and accepted to a specific research community. More often, however, it is synthetic. It may require expressing results in different forms or at different resolutions; drawing causal inferences from knowledge or data that lie outside the scope of the discipline that generated them (if you do X, then Y will (probably) happen); or combining propositions from different disciplines, of different degrees of confidence and verification. Because assessment serves decision needs, it may require statements of probability, or of the degree of confidence with which a certain contention can be held, that would be unacceptable within a disciplinary debate, for a variety of intellectual and sociological reasons.
What Is Integrated Assessment?
What does it mean for assessment to be integrated? Again, the answer is highly context-specific. The only general answer is that to be integrated is to present a broader set of information than standard research activity, more than typical good research from a single discipline. Some redundancy may be found here, because essentially all assessment requires some integration. Few issues of importance that any responsible person faces can be well-understood, and few significant choices well-advised, with reference only to the research content of a single discipline.But there are many possible ways for assessment to be integrated and degrees of integration. The standard view of integration refers to the causal chain that joins human actions to valued consequences. In assessment of climate change, this means assessment that considers the social and economic factors that drive emissions, the biogeochemical cycles and atmospheric chemistry that determines the fate of emissions, the resultant effect of emissions on climate globally and locally, and the impacts of climate change on managed and unmanaged ecosystems, and consequently on human activities and welfare. This view is commonly called "end-to-end" integration. It is reflected in the widely held view that integrated assessment of climate change means considering emissions and impacts together to permit a benefit-cost assessment: one that compares costs of responses to the impacts they prevent.
Many other dimensions of integration are also relevant, some that expand single links in this causal chain and some that characterize the process of doing assessment. For example, within single links of the causal chain you can integrate over contributing activities (by type of activity, sector, type of emission, location, and time) or over consequences (with roughly the same dimensions); or, examining the process of doing assessment rather than its substantive content, you can integrate over disciplines and analytical styles participating, or over sectors or interests granted representation within the process, or authority over its outcomes. What kinds of integration will be necessary for a successful assessment will depend on the job.
This guide defines integrated assessment broadly. The two defining characteristics are a) that it seeks to provide information of use to some significant decision-maker rather than merely advancing understanding for its own sake; and b) that it brings together a broader set of areas, methods, styles of study, or degrees of certainty, than would typically characterize a study of the same issue within the bounds of a single research discipline.
The guide undertakes a survey of the state of the craft of integrated assessment as it is being applied to climate change. In general, it concentrates on integrating projects and models . Several kinds of component studies being integrated as modules into integrated assessment studies are not discussed in this paper. These include energy-economic models, some of which have recently been applied to climate change to study economic consequences of emission-limitation measures; models of atmospheric chemistry or biogeochemical cycles; taxes, emission targets, or other measures to limit emissions of CO2. Several of these studies are being integrated as economic submodels into the broader integrated assessment projects discussed here and will be mentioned briefly in the discussion of their broader projects.
The next section is Section 2: Past Integrated Assessment Examples and Parallels.
