A Forbes article this weekend makes clear the Pentagon has regarded global warming as a national security threat since the 1980s:
“The Military Advisory Board is dismayed that discussions of climate change have become so polarizing and have receded from the arena of informed public discourse and debate.
“While the causes of climate change and its impacts continue to be argued or ignored in our nation, the linkage between changes in our climate and national security has been obscured. Political concerns and budgetary limitations cannot be allowed to dominate what is essentially a salient national security concern for our nation. Our Congress, the administration, and all who are charged with planning and assuring our security should take up the challenge of confronting the coming changes to our environment.”
“Our Military Advisory Board concluded that ‘coordinated and well-executed actions to limit heat-trapping gases and increase resilience to help prevent and protect against the worst projected climate change impacts are required — now.’ Whatever your thoughts on the relative human and natural influences on climate change, ignoring our military is not prudent. They understand the dangers of not being prepared.”
In other words, if you’re a global warming denier, you’re not merely a crank, you’re also a national security threat and un-American. The Military Advisory Board said it more politely than I just did, but they’re saying the same thing, with only a little reading between the lines. If you disagree with this message, don’t complain to me, 
argue with the Pentagon. I’m only the guy who delivers the telegram.