Story highlights Senior members of the military have argued climate change is a national security threat

A 2016 report warned climate change could ultimately cause nations to collapse

(CNN) As President Donald Trump contemplates withdrawing the US from the landmark Paris climate accord, he may be turning his back on some crucial national security views, starting with the opinion of his own Defense Secretary, James Mattis.

During his confirmation process in January, Mattis responded to a question from the Senate Armed Services Committee about whether climate change is a security threat, writing: "Climate change can be a driver of instability and the Department of Defense must pay attention to potential adverse impacts generated by this phenomenon."

Mattis went on to say, "climate change is a challenge that requires a broader, whole-of-government response," adding that he would "ensure that the Department of Defense plays its appropriate role within such a response by addressing national security aspects."

For those who follow Mattis' views on environmental challenges, it wasn't a surprise. In 2010, while still on active duty, his command issued a report on future trends facing the military. That report noted: "The impact of climate change, specifically global warming and its potential to cause natural disasters and other harmful phenomena such as rising sea levels, has become a concern."

A CNN military analyst, retired Lt. Gen. Mark Hertling, said climate change is a vital national security issue.

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