policy choices in the near term that will prepare the nation for events in later decades.

Our study includes the full range of potentially disruptive events that are becoming more likely because of climate change, whether or not a particular event can be unequivocally attributed to human-caused climate change rather than to natural variation. We made this choice because any such climate events can become disruptive and create a need for U.S. government action regardless of whether they can at this time be uniquely attributed to anthropogenic climate change.


Anthropogenic climate change can reasonably be expected to increase the frequency and intensity of a variety of potentially disruptive environmental events—slowly at first, but then more quickly. Some of this change is already discernible. Many of these events will stress communities, societies, governments, and the globally integrated systems that support human well-being. Science is unlikely ever to be able to predict the timing, magnitude, and precise location of these events a decade in advance, but much is already known that can inform security analysis, including details about the character of events that are becoming more likely and about the general trajectory of increasing risk.

Conclusion 3.11: Given the available scientific knowledge of the climate system, it is prudent for security analysts to expect climate surprises in the coming decade, including unexpected and potentially disruptive single events as well as conjunctions of events occurring simultaneously or in sequence, and for them to become progressively more serious and more frequent thereafter, most likely at an accelerating rate. The climate surprises may affect particular regions or globally integrated systems, such as grain markets, that provide for human well-being.

The conjunctions of events will likely include clusters of apparently unrelated climate events occurring closely in time, although perhaps widely separated geographically, which actually do have common causes; sequences or cascades of events in which a climate event precipitates a series of other physical or biological consequences in unexpected ways; and disruptions of globally connected systems, such as food markets, supply chains for strategic commodities, or global public health systems. The surprises are likely to appear first as unusually severe extensions of familiar experience.


1 Conclusions and recommendations are numbered to indicate the chapter where they appear and their ordering within that chapter.

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