Global warming poses a "serious threat to America's national security" and the military should act now to minimize the destabilizing consequences of rising temperatures, a panel of retired generals and admirals warned Monday.
Shortages of food and water could cause weak governments to collapse, increasingly severe natural disasters could draw U.S. forces into humanitarian missions in volatile areas, and melting Arctic ice could spark territorial disputes over shipping routes and natural resources.
Even the effectiveness of sonar used by American submarines could be at risk if parts of the oceans become less salty.
The 63-page report describes climate change as a "threat multiplier" that makes dangerous situations around the world all the more menacing.
"We will pay for this one way or another," said retired Marine Gen. Anthony C. Zinni, who commanded U.S. forces in the Middle East. "We will pay to reduce greenhouse gas emissions today ... or we'll pay the price later in military terms. And that will involve human lives."
Other experts who were not involved in the report said national security concerns, though real, were probably not the most significant threats posed by global warming.
"Everything's a national security issue these days," said Scott Barrett, director of the International Policy Program at Johns Hopkins School of Advanced International Studies. "It's a bit of a marketing ploy."
The report, produced by the Center for Naval Analysis, a federally funded nonprofit research and analysis organization based in Alexandria, Va., was overseen by an 11-member military advisory board chaired by former Army Chief of Staff Gen. Gordon R. Sullivan.
It was funded by the Rockefeller Family Fund, the Bipartisan Policy Center and other foundations.
The report's release came on the eve of a United Nations Security Council debate on climate change beginning today.
"Global warming's impacts on natural resources and climate systems may create the fiercest battle our world has ever seen," said Rep. Edward J. Markey (D-Mass.), chair of the newly formed House Select Committee on Energy Independence and Global Warming. Markey will introduce legislation to fund climate change planning by the Department of Defense.
Those battles may force the demise of weak governments in the developing world, creating power vacuums for terrorist groups to exploit, the report found.
Deteriorating conditions in Africa and the Middle East could prompt a wave of migration to Europe. As a result, the report said, some of America's most dependable allies could find themselves too distracted to participate in international coalitions or other efforts aimed at preventing regional conflicts.
Other experts called those risks unlikely. Climate change will certainly lead to more failed states, but it is not clear that the result would be an increase in terrorism, said Steve Weber, director of the Institute of International Studies at UC Berkeley.
The Sept. 11 hijackers "came from Saudi Arabia, not the floodplains of Bangladesh," he said.
He also downplayed the notion that migration spurred by climate change would be an important factor in U.S.-European relations.
But Weber agreed with the report's authors that the opening of shipping channels through the now-frozen Arctic could become a significant source of conflict.
"There aren't well-specified and agreed-on rules as to who owns what," he said. Russia, which has lots of land above the Arctic Circle, and China, which does not, could have very different views about how to address access to new waterways there. "There could be some pretty big fights over that," he said.
When the American military does deploy, the logistics will be more complicated than in the past. Widespread droughts will require massive transportation of water to troops stationed in foreign countries, the report found.
In addition, increased storm activity will impair normal maintenance and repairs of military equipment, and coastal flooding could inundate some key U.S. bases, such as Naval Air Station Pensacola in Florida and the Naval Support Facility at Diego Garcia in the Indian Ocean.
To lessen the impact, the panel said, climate change should be woven into national security and defense strategies, and the military should take a stronger role in reducing its own contribution to global warming.
The Department of Defense did not return calls seeking comment on the report.
Roger Pielke Jr., director of the University of Colorado's Center for Science and Technology Policy Research, applauded the panel's concern about climate change but said its recommendations were too general to be of much use.
"This report seems to me to be about the political need to respond to climate change via energy policy and not about practical policy advice to the military," he said.