that earlier rendered the tropics uninhabitable; snow-making equipment has turned marginal mountains into thriving ski areas. While few of these are unalloyed improvements, and many have unwelcome impacts on ecosystems, they have reduced human vulnerabilities markedly. Moreover, it is unlikely that these trends will suddenly stop tomorrow. Thus, one of our societal challenges is to harness technology to improve monitoring and prediction and enhance adaptation in the face of potential abrupt climate change. A second challenge is to better understand the interactions and feedbacks between the natural and human-dominated systems, and the limitations of technology when dealing with ecosystem vulnerabilities.
Economic and ecological systems are extremely complex nonlinear systems. Both involve individual components (whether firms or organisms) which interact in ways where “everything depends on everything else.” Because of this complexity, economists and ecologists increasingly have turned to computerized numerical models to help understand the functioning of these large systems and to help predict the impacts of shocks or disturbances.
Over the last decade, these models have been deployed to help understand the potential impacts of climate change on economic and ecological systems. As a result, substantial advances have been made in understanding the way that economic and ecological systems may be affected by gradual climate change. One of the important developments in economics over the last decade has been the development of integrated-assessment economic models, which analyze the problem of global warming from an economic point of view. Integrated-assessment economic models are empirical computerized models that incorporate the major linkages between climate change and the economy. Dozens of modeling groups around the world have brought to bear the tools of economics, mathematical modeling, optimization, decision theory, and related disciplines to investigate the effects of accumulations of greenhouse gases as well as the costs and benefits of potential policy interventions such as emissions limitations or carbon taxes.7
As with economic impact studies, virtually all the studies undertaken by the integrated-assessment economic models community of scholars have