ferent but potentially dangerous shifts in the intensity of the monsoon are plausible, with the changes possibly occurring with a transition time of only a year or so. From a security perspective it may make sense to take each of the model-projected futures through a what-if scenario mode. Similarly, projections of the West African monsoon point to a Sahel (the east–west stretch of Africa south of the Sahara desert and north of the Sudanian savannahs) that is either wetter or drier or else has no average change in rainfall but has a doubling of the number of anomalously dry years (Lenton et al., 2008)—three scenarios that could be examined in terms of their social and political implications.
The purpose of this study is to help improve the ability of the U.S. intelligence community and other interested actors to foresee security risks that may arise from climate change and its interactions with other social, economic, and political processes. Thus, we are concerned with climate risks to the extent that they may affect security risks.
Improved foresight can inform several kinds of policy responses: (1) responses to reduce climate risks (i.e., the risks that potentially harmful climate events will occur); (2) responses to reduce the exposure of people or valued assets to potentially harmful climate events; (3) responses to reduce susceptibility to harm from such events; and (4) responses that assist in the coping, response, and recovery processes after harmful events occur. We are aware of debates about how such policy responses should be organized and by whom. These questions are beyond the scope of our study, as are questions about how best to reduce the risks of occurrence of harmful climate events. Our focus is on anticipating security risks related to climate processes, understanding the roles of climatic and other factors in the dynamics of these risks, and informing decision makers about the nature of these risks and the opportunities for reducing them. We hope the study will, by improving understanding of the risks, provide a better basis for informed debate about which policy responses are most advisable. We have focused the study in three important ways, as outlined below.
Focus on Vulnerability to Climate Events
Although each of the scenario types that have been mentioned in climate–security studies is potentially significant for national security, this study focuses on scenarios involving the vulnerability of human populations, institutions, and life-supporting systems to harm from climate events, in which the harm has the potential to set events in motion that lead to security concerns. As discussed above, these scenarios in which climate events