LONDON — About two years ago, I realized that the military in various countries were starting to do climate-change scenarios in-house — scenarios that started with the scientific predictions about rising temperatures, falling crop yields and other physical effects, and examined what that would do to politics and strategy.

The scenarios predicted the proliferation of failed states because governments could not feed their people; waves of climate refugees washing up against the borders of more fortunate countries; even wars between countries that shared the same rivers.

So I started interviewing everybody I could get access to — not only senior military people but scientists, diplomats and politicians. About 70 interviews, a dozen countries and 18 months later, I have reached four conclusions that I didn’t suspect when I began the process:

Scientists are really scared. Their observations over the past two or three years suggest that everything is happening a lot faster than their climate models predicted. This creates a dilemma for them, because for the past decade they have been struggling against a well-funded campaign that cast doubt on the phenomenon of climate change.

Finally, people and even governments are listening. Even in the United States, the world headquarters of climate- change denial, 85 percent of the population now sees climate change as a major issue, and both presidential candidates in last month’s election promised 80 percent cuts in American emissions of greenhouse gases by 2050.

The scientists are understandably reluctant at this point to announce publicly that their predictions were wrong — that it’s really much worse and the targets will have to be revised. Most of them are waiting for overwhelming proof that climate change really is moving faster, even though they are already privately convinced that it is.

So, governments, though awakened to the danger at last, are still working to the wrong emissions target. The real requirement to avoid runaway global warming is probably 80 percent cuts by 2030, and almost no burning whatever of fossil fuels (coal, gas and oil) by 2050.

The generals are right. Food is the key issue, and world food supply is already very tight. We have eaten up about two-thirds of the world grain reserve in the past five years, leaving only 50 days’ worth in store. Even a 1 degree C rise in average global temperature will take a major bite out of food production in almost all the countries that are closer to the equator than to the poles, and that includes almost all of the planet’s breadbaskets.

So the international grain market will wither for lack of supplies. Countries that can no longer feed their people will not be able to buy their way out of trouble by importing grain from elsewhere, even if they have the money.

Starving refugees will flood across borders, whole nations will collapse into anarchy — and some countries may make a grab for their neighbors’ land or water.

These are scenarios that the Pentagon and other military planning staffs are examining now. They could start to come true as little as 15 or 20 years down the road. If this kind of breakdown becomes widespread, there will be little chance of making or keeping global agreements to curb greenhouse gas emissions and avoid further warming.

There is a point of no return after which warming becomes unstoppable. And we are probably going to sail right through it. It is the point at which anthropogenic (human-caused) warming triggers huge releases of carbon dioxide from warming oceans, or similar releases of both carbon dioxide and methane from melting permafrost, or both. Most climate scientists think that point lies not far beyond 2 degrees C hotter.

Once that point is passed, the human race loses control: Cutting our own emissions may not stop the warming. Yet we are almost certainly going to miss our deadline. We cannot get the 10 lost years back, and by the time a new global agreement to replace the Kyoto accord is negotiated and put into effect, there will probably not be enough time left to stop the warming short of the point where we must not go.

We will have to cheat. In the past two years, various scientists have suggested several “geo-engineering” techniques for holding the temperature down directly. We might put a kind of temporary chemical sunscreen in the stratosphere by seeding it with sulfur particles, for example, or we could artificially thicken low-lying maritime clouds to reflect more sunlight. These are not permanent solutions; merely ways of winning more time to cut our emissions without triggering runaway warming in the meanwhile.

The situation is getting very grave, and we are probably going to see the first experiments with these techniques within five years. There is a way through this crisis, but it isn’t easy and there is no guarantee of success.

As the Irishman said to the lost traveler: If that’s where you want to go, Sir, I wouldn’t start from here.

Gwynne Dyer is a London-based independent journalist and historian.

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