In a report commissioned by the U.S. intelligence community, the National Research Council has concluded that the acceleration of climate change means "disruptive environmental events" will occur with increasing frequency and growing impact on national and global security. The study, titled Climate and Social Stress: Implications for Security Analysis, was prepared by a team led by John Steinbruner, director of the University of Maryland's Center for International and Security Studies.
The study's summary states:
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 discern- ible. 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.
The New York Times summarizes the report and includes comments from Steinbruner in an article here.