The head of the U.S. Navy Pacific command says climate change is the biggest long-term security threat in the Pacific region. Although he faces concerns in North Korea, China, and Japan, Navy Admiral Samuel J. Locklear III said Friday that global warming “is probably the most likely thing that is going to happen… that will cripple the security environment, probably more likely than the other scenarios we all often talk about.”

Locklear noted that “You have the real potential here in the not-too-distant future of nations displaced by rising sea levels. Certainly weather patterns are more severe than they have been in the past.” Responding to humanitarian crises resulting from natural disasters is already a large part of the Pacific command’s duties. And Locklear is not the first to draw attention to climate change as a security threat. Members of Congress, the UN Security Council, and active and retired U.S. military leaders have also stressed the importance of climate change and its potential effects on national and international affairs.

Naturally, Locklear’s statements are drawing criticism. But for several years, experts at the Pentagon and intelligence agencies have been looking at the national security implications of climate change. Domestically, natural disasters, such as severe typhoons and hurricanes, put great operational strain on Pacific forces, but with severe weather occurring more frequently, the implications would also be much more severe, both nationally and internationally. In addition to extreme storms, severe weather would cause flooding and drought, which can produce water crises, food shortages, displacement, and vast infrastructure damage. Displacement can, among other issues, lead to religious conflict, political violence, and the spread of contagious disease.

And while the public climate change debate generally centers on finding substitutes for fossil fuels and reducing greenhouse gas emissions, lawmakers and officials are focusing more on the national security side of the argument as well. In 2008, the National Intelligence Council concluded that “climate change by itself would have significant geopolitical impacts around the world and would contribute to a host of problems, including poverty, environmental degradation and the weakening of national governments.”

Locklear said that the U.S. is working with other militaries to address the threat of global warming. “We have interjected into our multilateral dialogue – even with China and India – the imperative to kind of get military capabilities aligned [for] when the effects of climate change start to impact these massive populations,” he said. “If it goes bad, you could have hundreds of thousands of millions of people displaced and then security will start to crumble pretty quickly.”

Alisha Mims is a writer and researcher for Ring of Fire.