BOX 2-2
A Risk-Analytic Approach to Climate Events and Stresses

Risk is typically defined as the severity of an undesired outcome multiplied by the likelihood of its occurrence. Climate change alters both the likelihood of occurrence and the likely severity of certain events that may degrade human life-supporting systems. Changes in these systems may in turn alter the likelihood and severity of social disruption, stress on political systems, and events of potential importance to U.S. national security—violent internal or international conflict, state failure, and so forth.

Social conditions and social changes affect the exposure and vulnerability of human populations and societies to climate events and thus the risks associated with these events. They also shape the responses of social systems when such events occur, further influencing the risks of political and social stress.

It is essential to think about climate and security in terms of risks because it is beyond the capacity of today’s science to predict specific climatic events or their social or political consequences years or even months in advance. However, the natural and social sciences can help the intelligence and national security communities understand whether, where, and to what extent the risks of these effects are changing and how to reduce them.

The security risks posed by climate change are multidimensional. The overall risk may depend on attributes of:

Climate events:

1.   Types of climate events (e.g., floods, crop failures, and disease outbreaks)

2.   The likelihoods of the events

indicators of exposure, susceptibility, or the likelihood of successful coping and response, either of socioeconomic systems or of the resource bases on which human populations in critical regions depend.

A third approach emphasizes the analysis of system vulnerabilities. Such an analysis might be focused, for example, on the social and political capabilities and weaknesses of particular regimes both generally and in the face of expected climate events. It would ask how capable a particular regime is of dealing with its routine challenges and then consider how able it would be to deal with additional stresses, specifically those that might arise from future climate events. The focus for a particular country, region, or system should be on the examination of potentially disruptive climate events that have a reasonable likelihood of arising there in the coming years—that is, a set of plausible worst cases—along with various ways that the regime might address such problems (e.g., hardening infrastructure,



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