We've been through a kind of cultural revolution in the last two years over global warming. Hardly anyone seriously disputes the science any more (though I'm sure I'll hear from some who do), and whatever the outcome of the November election we may even get significant U.S. legislation next year for the first time. It took us 20 years to get to this point, and now we have to figure out what our priorities are going to be for the next 20 years. One of those is to start planning for the humanitarian emergencies and political instability that will hit the countries most at risk from sea-level rise, drought, and rising temperatures. Bangladesh, for instance, is going to lose 12-15% of its national territory, and 10 million people or more will be driven from their homes. Rice and other crop production in Asia is likely to decline by 10 percent or so, in part because of glacial melt in the Himalayas. The impact on agriculture from drought in Africa will be even worse.

Now the national security establishment has begun to sit up, take notice, and issue some ominous warnings. It started last year with two widely publicized reports, the first a Pentagon-commissioned study of the future impact of climate change by consultants from the Global Business Network, and then, a few weeks later, a report from the Center for Naval Analyses signed by a group of 11 retired generals and admirals. Now it's the turn of the intelligence community, with a June 24 report outlining some of the dire political and social consequences of climate change.

You can see all this as positive in one sense: they do heighten the sense of urgency and sharpen the focus on that 20-year perspective I mentioned. And there may well be some new allies and new arguments here for the environmental community. But we'll need to proceed with extreme caution, because the impulse behind many of these developments may have less to do with reducing the impact of global warming than with finding new ways of fighting the next round of the so-called War on Terror. Listen to Tom Fingar, deputy director of intelligence, presenting the June 24  report. Climate change is likely to "increase the pool of potential recruits for terrorism." And worse, changing energy policies "may affect U.S. national security interests even more than the physical impacts of climate change itself."

Yes, national security is at stake here. But first and foremost it's the national security of Bangladeshis and Indians, of Malians and Sudanese. Figure out the response to their predicament - which starts with the transformation of our energy policies - and our national security is likely to follow.