The military is bracing for a global warming crisis that will cause sea levels to rise by at least 12 to 18 inches over the next 20 to 50 years.
That will put at risk port facilities around the world, including some that are critical to the military, such as San Diego, Hawaii and Norfolk, Virginia.
Inside the U.S., more severe weather — hurricanes, tornadoes and wildfires fueled by drought — will cause catastrophic damage that will likely require more frequent support from the National Guard.
Abroad, warming seas will change the face of the map, most dramatically in the Arctic, where polar ice caps are melting. That means the U.S. Navy will face new zones of competition with big rivals like China and Russia as new sea lanes emerge and new fossil fuel and mineral deposits become accessible.
In light of those developments, the Pentagon for the first time is laying out a "Climate Change Adaptation Roadmap," which details how the U.S. military will prepare and respond to the fallout from global warming.
"In our defense strategy, we refer to climate change as a 'threat multiplier' because it has the potential to exacerbate many of the challenges we are dealing with today, from infectious disease to terrorism. We are already beginning to see some of these impacts," Defense Secretary Chuck Hagel wrote in the introduction to the 20-page document.
On Monday, at an international meeting of defense ministers in Peru, Hagel unveiled the report, which outlines a long list of sweeping potential changes for the Defense Department:
■ Humanitarian assistance missions likely will become far more frequent.
■ For the Marine Corps, rising sea levels could make it harder to mount amphibious landings.
■ For the Air Force, changing weather patterns may make it harder to fly or conduct overflight for intelligence, surveillance and reconnaissance missions.
■ For the Navy, new ship technology might be needed to operate in the icy-but-navigable waters of the Arctic.
■ The Army could be called upon to help manage instability caused by flooding of densely populated coastal areas, where mass-migration creates turmoil and a breeding ground for extremist groups.
■ Environmental changes can create new health risks for troops, for example by enlarging infectious disease zones and boosting demand for health services, health surveillance or personal protective equipment.
■ On installations, flooding and erosion will threaten both the military's infrastructure and training areas.
■ Bases in the drought-prone West will have to consider new water management programs; drought may lead to more dust that threatens military equipment and in turn require more maintenance or increased equipment costs.
The Pentagon is nearing completion on an assessment of the vulnerability of more than 7,000 bases and installations around the globe, the report said, and senior leaders are ordering a review of all budget plans, war game scenarios and off-the-shelf operational contingency plans to determine if they need revisions in light of projected impact of global warming.
The release of the report Monday follows a related document that Hagel unveiled last year outlining a new strategy for the Arctic region. U.S. officials estimate the Arctic holds 13 percent of the world's undiscovered oil reserves and 30 percent of undiscovered gas deposits.
Hagel said scientists are "converging toward a consensus" on the issue of global warming and he urged decision-makers inside and outside the military to set aside the intense political debate over the issue.
"Politics or ideology must not get in the way of sound planning. Our armed forces must prepare for a future with a wide spectrum of possible threats, weighing risks and probabilities to ensure that we will continue to keep our country secure," Hagel wrote.
Andrew Tilghman is the executive editor for Military Times. He is a former Military Times Pentagon reporter and served as a Middle East correspondent for the Stars and Stripes. Before covering the military, he worked as a reporter for the Houston Chronicle in Texas, the Albany Times Union in New York and The Associated Press in Milwaukee.