For the second time in a month, private consultants to the government are warning that human-driven warming of the climate poses risks to the national security of the United States.

A report, scheduled to be published on Monday but distributed to some reporters Saturday, said issues usually associated with the environment — like rising ocean levels, droughts and violent weather caused by global warming — were also national security concerns.

"Unlike the problems that we are used to dealing with, these will come upon us extremely slowly, but come they will, and they will be grinding and inexorable," Richard J. Truly, a retired U.S. Navy vice admiral and former NASA administrator, said in the report.

The effects of global warming, the study said, could lead to large-scale migrations, increased border tensions, the spread of disease and conflicts over food and water. All could lead to direct involvement by the U.S. military.

The report recommends that climate change be integrated into the nation's security strategies and says the United States "should commit to a stronger national and international role to help stabilize climate changes at levels that will avoid significant disruption to global security and stability."

The report, called "National Security and the Threat of Climate Change," was commissioned by the Center for Naval Analyses, a government-financed research group, and written by a group of retired generals and admirals called the Military Advisory Board.

In March, a report from the Global Business Network, which advises intelligence agencies and the Pentagon on occasion, concluded, among other things, that rising seas and more powerful storms could eventually generate unrest as crowded regions like Bangladesh's sinking delta become less habitable.

One of the authors of the report, Peter Schwartz, a consultant who studies climate risks and other trends for the Defense Department and other clients, said the climate system, jogged by a century-long buildup of heat-trapping gases, was likely to rock between extremes that could wreak havoc in poor countries with fragile societies.

"Just look at Somalia in the early 1990s," Schwartz said. "You had disruption driven by drought, leading to the collapse of a society, humanitarian relief efforts, and then disastrous U.S. military intervention. That event is prototypical of the future."

"Picture that in Central America or the Caribbean, which are just as likely," he said. "This is not distant, this is now. And we need to be preparing."

Other recent studies have shown that drought and scant water have already fueled conflicts in global hot spots like Afghanistan.