LEARNING FROM INTEGRATED ASSESSMENT OF CLIMATE-CHANGE

The objective of integrated assessment of climate change is to put ava ilable knowledge together in order to evaluate what has been learned, policy implications, and research needs. This paper summarizes insight s gained from five years of integrated assessment activity at Carnegie Mellon. After an introduction, in Section 2 we ask: who are the clima te decision makers? We conclude that they are a diffuse and often dive rgent group spread all over the world whose decisions are primarily dr iven by local non-climate considerations. Insights are illustrated wit h results from the ICAM-2 model. In Section 3 we ask: what is the clim ate problem? In addition to the conventional answer, we note that in a democracy the problem is whatever voters and their elected representa tives think it is. Results from studies of public understanding are re ported. Several other specific issues that define the problem, includi ng the treatment of aerosols and alternative indices for comparing gre enhouse gases, are discussed. In Section 4 we discuss studies of clima te impacts, focusing on coastal zones, the terrestrial biosphere and h uman health. Particular attention is placed on the roles of adaptation , value change, and technological innovation. In Section 5 selected po licy issues are discussed. We conclude by noting that equity has recei ved too little attention in past work. We argue that many conventional tools for policy analysis are not adequate to deal with climate probl ems. Values that change, and mixed levels of uncertainty, pose particu larly important challenges for the future.