THE SCIENCE OF ADAPTATION: A FRAMEWORK FOR ASSESSMENT B. SMIT 1 , I. BURTON 2,4 , R.J.T. KLEIN 3 and R. STREET 4 1 Department of Geography, University of Guelph, Ontario, N1L 1G8, Canada 2 Environmental Adaptation Research Group, University of Toronto 3 Potsdam Institute for Climate Impact Research, P.O. Box 601203, 14412 Potsdam, Germany 4 Environmental Adaptation Research Group, Atmospheric Environment Service, Ontario, M3H 5T4, Canada Abstract. This paper outlines what is meant by “adaptation” to climate change, and how it might be addressed in the IPCC Assessments. Two roles of adaptation in the climate change field are identified: adaptation as part of impact assessment (where the key ques- tion is: what adaptations are likely?), and adaptation as part of the policy response (where the central question is: what adaptations are recommended?). The concept of adaptation has been adopted in several fields including climate impact assessment and policy devel- opment, risk management, and natural hazards research. A framework for systematically defining adaptations is based on three questions: (i) adaptation to what? (ii) who or what adapts? and (iii) how does adaptation occur? The paper demonstrates that, for adaptation purposes, climate extremes and variability are integral parts of climate change, along with shifts in mean conditions. Attributes for differentiating adaptations include pur- posefulness, timing, temporal and spatial scope, effects, form and performance. The framework provides a guide for the treatment of adaptation in the IPCC assessments, both in the assessment of impacts and in the evaluation of adaptive policy options. Key words: adaptation, climate change, impact assessment, response options, vulnerability. 1. Introduction Much of the debate about climate change deals with its implications for natural and human systems, particularly where these are vulnerable to changes in climate, including the associated changes in frequency and intensity of extreme conditions. As a result, adaptation to climatic change and variability is now a fundamental concern, and is receiving increasing attention both in the climate change research community and in the ongoing international negotiations dealing with climate change. While the concept of adaptation is relatively new to the climate change research community, it has a longer history of use in such related fields as ecology, natural hazards and risk management. As analyses of adaptation to climate change and variability have become more common, researchers have proposed numerous types and forms of adaptation, characterized its processes and attributes, and identified a variety of applications. Thus, adaptations have been Mitigation and Adaptation Strategies for Global Change 4: 199–213, 1999. c 1999 Kluwer Academic Publishers. Printed in the Netherlands.