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Thematic Guide to Integrated Assessment Modeling



Climatic Impact Assessment Program (CIAP)

Probably the first major project in integrated assessment of an environmental issue was the Climatic Impact Assessment Program (CIAP), which investigated potential atmospheric impacts of the proposed American supersonic transport aircraft (SST) in the early 1970s. Though climate change was part of CIAP's mandate, most of their work focused on potential SST-caused depletion of the stratospheric ozone layer and on resultant increases in ground-level ultraviolet (UV) radiation and accompanying ecosystem damages and health risks. (For further information on the effects of ozone depletion and increased ultraviolet radiation, see the CIESIN Thematic Guide on Ozone Depletion and Global Environmental Change.) The mission statement reflected the intended broad policy-oriented perspective of the study: "in order to determine regulatory constraints on flight in the stratosphere such that no adverse environmental effects result, CIAP will assess ... the impact on man, plants, and animals of climatic changes which may occur from the operation of a worldwide stratospheric fleet as projected to 1990." The project was established by Congress in 1971 under the authority of the Department of Transportation (DOT), with a $20 million budget and a three-year deadline. DOT supervised the effort and provided the project leader, but the project involved hundreds of researchers (Grobecker, Coroniti, and Cannon 1974).

With a huge mandate and a short deadline, CIAP was a crash program. Much of the basic knowledge needed for an assessment was lacking, so the study sponsored extensive basic research on the stratosphere, on jet engine emissions and potential design modifications to mitigate them, and on effects of emissions in perturbing the stratosphere. In addition, many of the atmospheric trace constituents implicated in possible harm from the SST had never been measured, so CIAP sponsored projects to measure them.

The study was structured in six separate modules, with a simple straight-line flow diagram representing assumed causal relations between them. Teams on the six modules worked in parallel, studying the behavior of their area under a specified range of input parameters from other parts of the system. Integration of the study took place late in the process, in the sequential project of writing the six huge summary monographs that were the study's main product. Because this task was organized sequentially, the two studies at the downstream end of the causal chain--biological impacts and economic and social impacts--had insufficient time to complete their work. In particular, the economic impacts team never received quantitative estimates from the biological study team of the effect of increased UV radiation on plants. (For further information on the effects of increased UV radiation on plants, see the CIESIN Thematic Guide on Ozone Depletion, Ultraviolet-B Effects on Terrestrial Plants.)

CIAP was clearly an integrated assessment, though the bulk of its contribution came from supporting fundamental new research when it found that information it needed was unavailable. CIAP defined a coherent and effective integrating framework to guide the research efforts of separate teams and to compel a highly successful level of cross-disciplinary collaboration. Even with the division into six modules, each module still required participation from people on both sides of the disciplinary divide that was most salient at the time, dynamicists and chemists (Glantz, Robinson, and Krenz 1985). Component studies were integrated, not by a single formal integrating model, but by a simple representation of causal links between modules and careful definition of what information each module needed from the others. Many models were developed and used within the component studies--indeed, some researchers objected that CIAP could have made an even greater contribution by doing more observation and less modeling--but these were integrated across modules judgmentally, not formally.

Reaction to CIAP focused principally on three elements: criticism of the predictable weaknesses of assessment components operating under impossible mandates and deadlines; an intense controversy over the report's hurriedly written and allegedly misleading executive summary; and praise for the study's enormous contribution to the development of a community of atmospheric science researchers. The CIAP report also raised some basic questions about how to do integrated assessment, but these were not clearly or satisfactorily resolved, and these issues attracted relatively little public attention. The report and executive summary express a traditional view of the relationship between assessment and policy: They assert that their work presents an objective analysis of facts and that they are presenting them to policy-makers to weigh in view of the appropriate political values and to make decisions. But this attempt to draw a clean line and stand firmly on one side of it is at variance with much of the report's contents, which clearly endorse international policy action to regulate stratospheric flight (though refrain from advocating any particular form of regulation). Moreover, the report includes a 600-page volume of "economic and social impacts" in which are proposed a variety of sophisticated assessment techniques that strongly mix objective knowledge with elicitation of opinion, preferences, and values.


The next section is U.S. Department of Energy Program in the Late 1970s.





Parson, E.A. and K. Fisher-Vanden, Searching for Integrated Assessment: A Preliminary Investigation of Methods, Models, and Projects in the Integrated Assessment of Global Climatic Change. Consortium for International Earth Science Information Network (CIESIN). University Center, Mich. 1995.


Suggested Citation

Center for International Earth Science Information Network (CIESIN). 1995. Thematic Guide to Integrated Assessment Modeling of Climate Change [online]. Palisades, NY: CIESIN. Available at [accessed DATE].



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