Gwynne Dyer:

"When British foreign secretary David Miliband revealed the latest numbers from the Met Office’s Hadley Centre (the U.K.’s national weather service) last October, predicting that a world in which emissions go unchecked may see a 4-degree-Celsius rise in average global temperature by 2060, he simply said: “We cannot cope with a 4-degree world.”

Actually, Britain probably could cope. As an island, cooled by the surrounding ocean, it would be only 3 degrees warmer, which means that it would probably still be able to grow enough food to feed itself. That is vital in a 4-degrees-warmer world, because almost nobody will be exporting food anymore.

Oceans cover two-thirds of the planet’s surface and are cooler than the land, so the average temperature over most land areas is higher than the “average global temperature”. The Hadley Centre predicts that a global average of plus-4 degrees means average temperatures 5 to 6 degrees higher in China, India, Southeast Asia, and most of Africa, and up to 8 degrees higher in the Amazon (which would burn, of course).

The result would be a 40-percent fall in world wheat and corn production and a 30-percent fall in rice by 2060—in a world that would, by then, have to feed 2 billion more people. So there would be mass starvation, and waves of desperate refugees trying to move to some country where they can still feed their kids."