Last week, Gen. Charles Jacoby, commander of North American Aerospace Defense Command (NORAD) and United States Northern Command (NORTHCOM), said he “doesn’t care why it’s melting. It’s melting," in comments last week, the Hill reported .

And while debate in Congress continues about the human contribution to global warming — despite a nearly unanimous scientific consensus — military leaders are not keen on waiting for a political consensus.

"We have already seen these events unfold in other regions of the world, and there are worrying signs that climate change will create serious risks to stability in our own hemisphere," he said.

“The loss of glaciers will strain water supplies in several areas of our hemisphere,” said Secretary of Defense Chuck Hagel at a conference in Peru alongside the publication of the report. “Destruction and devastation from hurricanes can sow the seeds for instability. Droughts and crop failures can leave millions of people without any lifeline, and trigger waves of mass migration.”

The report develops a road map to adapt to the new reality of global food and water shortages, fast-spreading disease, interruptions to commercial activity, and mass migration and displacement. It calls for the military to integrate climate change risks into its strategic thinking in all its operations.

The U.S. Department of Defense (DoD) on Monday said in a report that climate change will exacerbate global instability, posing an immediate threat to national security.

An Arctic puzzle

The DoD says climate change has an especially immediate impact on U.S. security challenges in the Arctic.

“The opening of formerly-frozen Arctic sea lanes will increase the need for the Department to monitor events, safeguard freedom of navigation, and ensure stability in this resource-rich area,” the report reads.

Arctic adjacent countries have been competing for control of the region — which could lead to conflict if not addressed now, the report said.

“We see an Arctic that is melting, meaning that most likely a new sea lane will emerge,” Hagel said on Saturday at a news conference in Chile after a meeting with government officials. “We know that there are significant minerals and natural deposits of oil and natural gas there. That means nations will compete for those natural resources.”

The Arctic may be ice-free as soon as the summer of 2016, a paper from the U.S. Department of Energy and Navy scientists predicted last year. Just months before those predictions, President Barack Obama unveiled his national Arctic strategy meant to protect American interests in the region.

Jacoby said the melting Arctic ice has attracted Russia’s Navy, which has been more active in the area in recent years. As part of the rush to lay claim to the region, Russia famously planted a flag in the ice there in 2007 and later created a new arctic military command. Canada and Denmark have also claimed the North Pole and increased their military presence in the Arctic.

Even though it doesn’t border the Arctic, China has been eying potential new shipping lanes in the region that could cut costs for its exports, and has called on world leaders to declare any emerging sea lanes there “international territory” that could be shared by all nations, Defense News reported.