"Looking back, I underestimated the risks. The planet and the atmosphere seem to be absorbing less carbon than we expected, and emissions are rising pretty strongly. This is potentially so dangerous that we have to act strongly. Do we want to play Russian roulette with two bullets or one?" stated Stern.

The Stern Review estimated a 75% chance that global temperatures would rise by between two and three degrees above the long-term average. Stern, who heads up the Grantham Research Institute on Climate Change and the Environment at the London School of Economics, says he now believes we are heading for four degrees of warming or more.

A November 2012 World Bank report, Turn Down the Heat: Why a 4°C Warmer World Must be Avoided, warns that a world that is 4°C warmer would be marked by extreme heat-waves, declining global food stocks, loss of ecosystems and biodiversity, and life-threatening sea level rise.