Modeling impacts and adaptation in global IAMs

Integrated assessment models (IAMs) of climate change combine dynamic descriptions of the energy-economy system, the climate system, and climate impacts to support the formulation of global, and possibly regional, climate policy. Originally they have been designed to inform mitigation policy but some of them are now applied in the context of adaptation policy as well. This article reviews the modeling of climate impacts and adaptation in global IAMs, including both models with an economic focus and models with a science focus. Key advances in the representation of climate impacts in IAMs during the last decade include improved consideration of differences in impacts across regions, the development of nonmonetary reduced-form climate impact models, and coupling of global IAMs with regional and sectoral impact models to assess climate change together with other sustainability issues. Further advances include a stronger focus on probabilistic analysis and attempt at considering large-scale climate instabilities. Adaptation has received only limited attention in global IAMs so far, mostly due to the mismatch in spatial scales at which mitigation and adaptation decisions are generally made. Some recent IAMs attempt to identify optimal levels of adaptation in climate-sensitive sectors or do include adaptation to climate change explicitly as a decision variable. The main reason for the consideration of adaptation in global welfare-maximizing IAMs is to assess the sensitivity of mitigation targets to different assumptions about the magnitude and effectiveness of adaptation. IAMs with geographically explicit impact models may also provide information that is useful for adaptation planning. (C) 2010 John Wiley & Sons, Ltd. WIREs Clim Change 2010 1 288-303