Adaptation to Global Warming: Do Climate Models Tell Us What We Need to Know? Author(s): Naomi Oreskes, David A. Stainforth, Leonard A. Smith Source: Philosophy of Science, Vol. 77, No. 5 (December 2010), pp. 1012-1028 Published by: The University of Chicago Press on behalf of the Philosophy of Science Association Stable URL: http://www.jstor.org/stable/10.1086/657428 . Accessed: 19/02/2011 12:34 Your use of the JSTOR archive indicates your acceptance of JSTOR's Terms and Conditions of Use, available at . http://www.jstor.org/page/info/about/policies/terms.jsp. JSTOR's Terms and Conditions of Use provides, in part, that unless you have obtained prior permission, you may not download an entire issue of a journal or multiple copies of articles, and you may use content in the JSTOR archive only for your personal, non-commercial use. Please contact the publisher regarding any further use of this work. 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Smith† Scientific experts have confirmed that anthropogenic warming is underway, and some degree of adaptation is now unavoidable. However, the details of impacts on the scale of climate change at which humans would have to prepare for and adjust to them are still the subject of considerable research, inquiry, and debate. Planning for adaptation requires information on the scale over which human organizations and institutions have authority and capacity, yet the general circulation models lack forecasting skill at these scales, and attempts to “downscale” climate models are still in the early stages of development. Because we do not know what adaptations will be required, we cannot say whether they will be harder or easier—more expensive or less—than emissions control. Whatever improvements in regional predictive capacity may come about in the future, the lack of current predictive capacity on the relevant scale is a strong argument for why we must both control greenhouse gas emissions and prepare to adapt. 1. Introduction. In recent years, there has been growing discussion in scientific and policy circles of the need for adaptation to climate change. These arguments take various forms, the most reasonable of which is that climate change is already under way, and even with a strong program of greenhouse gas mitigation, we will be facing further unavoidable changes arising from the long residence time of greenhouse gases in the atmosphere (IPCC 2007; Solomon et al. 2007).1 However, this is not a new insight: the UN Framework Convention on Climate Change, adopted at the Rio †To contact the authors, please write to: Naomi Oreskes, Department of History, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92092; e-mail: [email protected]. 1. See Pachauri and Reisinger (2007) for a synthesis of three Intergovernmental Panel on Climate Change (IPCC) working groups. Philosophy of Science, 77 (December 2010) pp. 1012–1028. 0031-8248/2010/7705-0037$10.00 Copyright 2010 by the Philosophy of Science Association. All rights reserved. 1012 ADAPTATION TO GLOBAL WARMING 1013 Earth Summit in Rio de Janiero in 1992, acknowledged even then that responding to climate change would involve some degree of adaptation.2 Today, as we look to the future, it is not a question of either/or— mitigation or adaptation—it is a matter of both/and. We will need to mitigate to avoid the worst case scenarios for future climate change, and we will need to adapt to the climate change that is now unavoidable because of our past and current use of greenhouse gases and changes in land use. All of this is taken as given among most scientists and others now involved in climate science and policy. Lately, however, some have been suggesting that adaptation is the preferred route to dealing with climate change. Adaptation, some argue, is more politically realistic and will be more cost effective and less economically disruptive than emissions control. This argument has been particularly promoted by the libertarian think tank, the CATO Institute, but some environmentalists accept it as well (e.g., Schellenberger and Nordhaus 2007).3 When the Los Angeles Times summarized the views of advocates of adaptation, they glossed it this way: “Just deal with it” (Zarembo 2008). This gloss might be viewed as a bit misleading, because by and large advocates of adaptation are not arguing for simply responding to changes after they occur; they are arguing for preparing to adapt. But arguments for preparing for the consequences of global warming—rather than trying to prevent them—rest on the as- sumption that we know what “they” are. That is to say, they rest on the assumption that we can reliably anticipate the changes to which we will be adapting and therefore that we can sensibly plan for those changes. Do climate models give us the information we would need to accurately estimate the costs of adaptation and effectively prepare for the conse- quences of climate change? In this article, we argue that they do not. First, while climate models consistently suggest that the mean global temperature of the planet will rise, mean global temperature is not what any one person, state, or nation will be adapting to. Human beings will be adapting to changes in the weather at the places where they live and a host of concomitant local effects of climate change that ensue from such changes. While there is broad consensus on the expected change in average global temperature, there is much less agreement between models regard- ing these local changes and concomitant effects. In particular, there is widespread divergence in model simulations of the impact of global warm- 2. For background on the UN Framework Convention on Climate Change, see http:// unfccc.int/2860.php. For its text, see United Nations (1992). 3. One of CATO’s longtime spokesmen on the subject, Patrick Michaels, has recently made a point of stressing human adaptive capacity (see, e.g., Davis et al. 2005; Michaels and Balling 2009). 1014 NAOMI ORESKES ET AL. ing on regional precipitation, a variable that is at least as important for human activities as temperature, if not much more so. Furthermore, mod- els show systematic errors in the global mean temperature similar in mag- nitude to the size of the historical change we are seeking to understand. Models do not agree on the absolute value of the twentieth-century global warming temperature, but they do show close agreement on the size of the change over the past century. That is to say, while scientists agree that warming is underway, and broadly agree on the amount of anthropogenic change that has occurred to date, when we get down to the details of future changes and therefore anticipated future states, there is much less clarity and therefore much less agreement. Second, there is a gap between the scale on which models produce consistent information and the scale on which humans act. Planning for adaptation requires information on the scale over which human organi- zations and institutions have authority and power: towns, cities, states, provinces, and nations. The IPCC argues that current global circulation models (GCMs), with typical horizontal resolutions of 100–500 kilome- ters, provide “credible quantitative estimates of future climate change, particularly at continental scales and above”; phrasing that nods to the debates in the modeling community over their forecast skill on subcon- tinental scales (IPCC 2000).4 Thus, while the reality of mean global warm- ing is essentially undisputed, the future impacts on the scale at which humans would have to prepare for and adjust to them are still the subject of considerable research, inquiry, and debate (Oreskes 2004, 2007). Third, existing models are unable to simulate realistically (much less evaluate the likelihood of) extreme outcomes—a rapid disintegration of the West Antarctic Ice Sheet, for example, a major dieback of the Amazon, or a sudden increase in release of stored greenhouse gases from arctic permafrost. Yet, from a moral, ethical, and practical standpoint, our think- ing must consider the finite (that is to say, nonzero) possibility that such outcomes may occur (Gardiner 2004). Our global models give us little relevant information regarding such perhaps unlikely, but potentially grave, impacts. One thing, however, is virtually certain: the less we mitigate, the more we shall have to adapt. Furthermore, the less we mitigate, the more likely we are to face challenges that surpass our capacity to adapt without pain and suffering. Broadly speaking, the greater the burden of greenhouse gases in the atmosphere and the oceans, the greater the environmental impact will be. So the less we control those gases, the more likely it is that the ensuing climate changes will be difficult to manage. If we do 4. Resolution has improved since 2000, but the basic argument remains valid (IPCC 2000). ADAPTATION TO GLOBAL WARMING 1015 nothing at all, the odds of catastrophic outcomes increase substantially, and in the face of such outcomes our ability to “just deal with it” may well vanish entirely.