Love the web.. here's the links:

Summary: http://www.ems.org/climate/exec_pentagon_climatechange.pdf
Full report: http://www.ems.org/climate/pentagon_climatechange.pdf

This Defense Department study, obtained by the media in February 2004, looked at the impact of abrupt climate change on national security. Abrupt climate change is a worst-case scenario, which scientists consider a plausible, though uncertain, consequence of global warming. It draws heavily from a National Academy of Sciences report published in 2002 which said the likelihood of crossing a threshold that triggers abrupt climate change grows when the climate is pushed hardest by rapid loading of the atmosphere with heat-trapping pollution.

The authors of the report ordered by the Pentagon say that such a scenario could lead to global food and water shortages that would drive widespread migrations and border conflicts worldwide. While scientists believe this extreme scenario has a low probability, the serious economic, health, and environmental effects expected from mainstream mid-range global warming forecasts are much more certain and fully support prompt action to cut heat-trapping emissions. The very high consequences that would result from the scenarios reported to the Pentagon reinforce the importance of action now to reduce these emissions.