Cross-posted from the Wonk Room. This is the first in a three-part interview with economist Lord Nicholas Stern on climate policy.

Lord Nicholas Stern, one of the world’s most prominent climate economists, believes that failure to address global warming could eventually lead to World War III. In 2006, he produced the “Stern Review” on behalf of the British government, clearly laying out the potentially catastrophic economic consequences of failing to address climate pollution. Since then, the scientific understanding of the damages from global warming has grown, and Stern has warned that his report “underestimated the risks.”

In an exclusive interview with ThinkProgress, Stern described his current understanding of the stark consequences of inaction, which defy the scope of standard economic language. If no global policy to cut carbon pollution is enacted, there is about a 50 percent risk that global temperatures would rise above levels not seen for 30 million years by 2100, an extraordinary rate of change. The “potentially immense” consequences of this radical transformation of our planet, Stern explained, include the “serious risk of global war”:

The temperature increases, the temperature changes of this kind, transform where people can be. In the upwards direction, you’re going to get some areas that become deserts, probably most of southern Europe. Others that are inundated: Florida, Bangladesh, and so on.

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The point is that climate change will change the lives and livelihoods and where you can live all across the globe. We live where we live because of patterns of climate, where the rivers are, where the seashores are. That’s what determines where we are.

What we’re talking about here — this the cost of inaction, the cost of not doing much — is a transformation of where we can be. Over a hundred, 120 years, we can’t be that precise, a serious risk of global war, really, because you’ve got hundreds of millions of people, perhaps billions of people moving. That’s the cost of inaction. It’s potentially immense. [Emphasis mine.]

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Watch it:

The global climate system gives us both life and death, feeding civilizations and smashing them. Our fossil fuel pollution has already altered that system, pushing it out of natural balance. With the pollution we have already generated, the world now has 25 to 50 million climate refugees.

If we do not change course, and continue to increase the burning of coal and oil as multinational energy companies desire, we will fundamentally transform the very land we live on, the water we drink, the air we breathe in ways that are beyond our ken. The U.S. military dryly describes these consequences as a “threat multiplier.” If we are to learn anything from history, these are the kinds of threats that lead to war, and geometrically growing global warming brings threats on a global scale.

Stern, a professor at the London School of Economics, was visiting the United States to receive the Leontief economic prize from the Tufts University Global Development and Environment Institute for his work on the economics of climate change.