Reading a scientific paper on the train this weekend, I found, to my amazement, that my hands were shaking. This has never happened to me before, but nor have I ever read anything like it. Published by a team led by James Hansen at NASA, it suggests that the grim reports issued by the Intergovernmental Panel on Climate Change could be absurdly optimistic.

The geological record suggests that ice at the poles does not melt in a gradual and linear fashion, but flips suddenly from one state to another. When temperatures increased to 2-3 degrees Celsius above today's level 3.5 million years ago, sea levels rose not by 59 cm but by 25 meters.

Hansen and his team find it "implausible" that the expected warming before 2100 "would permit a West Antarctic ice sheet of present size to survive even for a century."

As well as drowning most of the world's centers of population, a sudden disintegration could lead to much higher rises in global temperature

less ice means less heat reflected