“Among the future trends that will impact our national security is climate change,” said Secretary of Defense Chuck Hagel in 2014. “Rising global temperatures, changing precipitation patterns, climbing sea levels, and more extreme weather events will intensify the challenges of global instability, hunger, poverty, and conflict. By taking a proactive, flexible approach to assessment, analysis, and adaptation, the Defense Department will keep pace with a changing climate, minimize its impacts on our missions, and continue to protect our national security.”
The statement was part of the 2014 release of the Department of Defense 2014 Climate Change Adaptation Roadmap.
The Department of Defense sees climate change as a “threat multiplier”, making worse many of the challenges we already face. Global stability is threatened by many elements of changing weather and sea level rise. A sea level rise of 1 meter, which is probable by 2100, would affect over 100 million people. And 2 meters, which is possible by 2100 would affect >180 million people, who would need to go somewhere else. Most of those affected are in lowlands of South and SE Asia and the SE U.S. Threats to food supply caused by changing climate (which is already happening) further exacerbates the threat of political instability.