“More than half the experts think there is a more than 10 per chance we’ll get five degrees C warming under that scenario,” he says. “And five degrees C is gigantic,” says Keith, noting it is enough to “knock out” the Greenland and Antarctic ice sheets. The meltwater would eventually raise sea level by as much as 100 metres.
The experts seem to be having a little difficulty with their maths. Temperatures have risen a whopping 0.7C over the last 120 ppm CO2 – but just for fun, let’s pretend that the next 150 ppm increase really did raise temperatures by 5C. What would that do to Antarctica? As you can see below, it would move the summer 0°C line inwards maybe 50 miles. At least 95% of the ice sheet would remain below freezing all year round. Ice does not melt below freezing. Warmer winter temperatures would mean more snow.