There has been speculation about the possibility of anthropogenic global warming since at least the late nineteenth century (Arrhenius 1896, 1908). At times the prospect of such a warming has been welcomed, for it has been thought that it would increase agricultural productivity and delay the onset of the next Ice Age (Callendar 1938). Other times, and more recently, the prospect of global warming has been the stuff of “doomsday narratives,” as various writers have focused on the possibility of widespread drought, flood, famine, and economic and political dislocations that might result from a “greenhouse warming”-induced climate change (Flavin 1989). Although high-level meetings have been convened to discuss the greenhouse effect since at least 1963 (see Conservation Foundation 1963), the emergence of a rough, international consensus about the likelihood and extent of anthropogenic global warming began with a National Academy Report in 1983 (National Academy of Sciences/National Research Council 1983) and meetings in Villach, Austria, and Bellagio, Italy, in 1985 (World Climate Program 1985) and in Toronto, Canada, in 1988 (Conference Statement 1988). The most recent influential statement of the consensus holds that although there are uncertainties, a doubling of atmospheric carbon dioxide from its preindustrial baseline is likely to lead to a 2.5 °C increase in the earth’s mean surface temperature by the middle of the twenty-first century (IPCC 1990). (Interestingly, this estimate is within the range predicted by Arrhenius 1896.) This increase is expected to have a profound impact on climate and therefore on plants, animals, and human activities of all kinds. Moreover, there is no reason to suppose that without policy interventions, atmospheric carbon dioxide will stabilize at twice preindustrial levels. According to the IPCC (1990), we would need immediate 60 percent reductions in net emissions in order to stabilize at a carbon dioxide doubling by the end of the twenty-first century. Since these reductions are very unlikely to occur, we may well see increases of 4 °C by the end of the twenty-first century.