An era of ice that has gripped Earth's poles for 35 million years could come to an end as extreme global warming really begins to bite. Previously unknown sources of positive feedback - including "hyperwarming" that was last seen on Earth half a billion years ago - may push global temperatures high enough to send Earth into a hothouse state with tropical forests growing close to the poles.
Climate scientists typically limit themselves to the 21st century when predicting how human activity will affect global temperatures. The latest predictions are bolder, though: the first systematic forecasts through to 2300 are beginning to arrive.
Via Szabolcs Kósa