although some also included projections to the end of the century. Given that these were not academic reports, the basis for the groups’ judgments and the level of confidence associated with them were usually not specified in detail. Without attempting a comprehensive review, this section seeks to provide a summary of frequently occurring themes and arguments about climate–security connections from major government reports (Fingar, 2008; U.S. Department of Defense, 2010; White House, 2010; Defense Science Board, 2011) and from some of the best-known examples in the mainstream policy literature (Busby, 2007; Center for Naval Analysis, 2007; Lennon et al., 2007; Center for Climate and Energy Solutions, 2009; Carmen et al., 2010; International Institute for Strategic Studies, 2011; Treverton et al., 2012). For some key statements from these studies, see Box 1-2.

These government and policy documents reflect a number of important common elements. Above all, the connections between climate and security are not presumed to be direct; they are seen as complicated and contingent, with the effects of climate events felt through their consequences for other factors that then affect security. For example, the 2010 QDR concludes:

While climate change alone does not cause conflict, it may act as an accelerant of instability or conflict, placing a burden to respond on civilian institutions and militaries around the world. In addition, extreme weather events may lead to increased demands for defense support to civil authorities for humanitarian assistance or disaster response both within the United States and overseas. (U.S. Department of Defense, 2010:85)

The most frequently cited potential climate events include sea-level rise, the shrinking of glaciers and the Arctic icecap, an increase in extreme weather events, and increasingly intense droughts, floods, and heat waves. The scenarios and examples presented in the above reports address broad consequences for fundamental societal needs such as food, health, and water and also the likely implications for specific regions and countries. Although the reports generally agree that future climate events are likely to increase tensions and political instability within and between states and perhaps also increase internal conflicts, they do not forecast an increase in interstate conflict.

Taken together, the most commonly cited climate–security scenarios in these reports result from failures or shortcomings of human systems in adapting to a changing climate; that is, they turn on the vulnerabilities of these systems to climate events. In these scenarios climate events cause harm to various support systems for human life and well-being by exceeding the ability of these systems to cope. Depending on other social, economic, political, and environmental factors, the harm may result in larger-scale political and social outcomes that are of concern for U.S. national security. All of the reports include some scenarios of this sort, although different re-

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