In 2004 the US Department of Defense commissioned a report prepared by GBN titled: An Abrupt Climate Change Scenario and Its Implications for United States National Security

Violence and disruption stemming from the stresses created by abrupt changes in the climate pose a different type of threat to national security than we are accustomed to today.

Military confrontation may be triggered by a desperate need for natural resources such as energy, food and water rather than by conflicts over ideology, religion, or national honor.

The shifting motivation for confrontation would alter which countries are most vulnerable and the existing warning signs for security threats.

Environmental Defense a leading national nonprofit organization concluded at that time:

In sum, the report emphasizes being prepared and strategically planning for a situation that is impossible to predict but is nevertheless not implausible. Climate change is occurring, it reminds us, and not taking action now to prevent future catastrophe could be a grave mistake.

Now, as recently reported by Adam Smallman via Dow Jones Newswire:

The U.S. Defense Department is understood to have received a fresh report that paints a picture of global temperature moves that are much sharper than many current projections, amplifying security and operational implications for the U.S. military, according to a person familiar with the matter. …

GBN co-founder and chairman Peter Schwartz Thursday refused to identify its client, but said it had prepared a report for a “U.S. national security entity” that features current secondary research that pointed toward “very large excursions from the mean” average global temperatures “to very hot or very cold.”

The report raises the prospect of more severe storms than currently experienced. The key consequence is worsening mass migration with a knock-on impact on services such as the U.S. Navy.

Schwartz said: “Central America and the Caribbean are going to be very, very hard hit by climate change. I work with the Navy. They’re going to have cope with large numbers of refugees.”

Bloomberg.com:
Climate Change More Extreme Than Thought, U.S. Study to Show
money.cnn.com:
The Pentagon’s Weather Nightmare - The climate could change radically, and fast. That would be the mother of all national security issues.