Lord Stern  who wrote the UK   government-commissioned review on climate change in 2006 which was thought of as the reference work on the subject says he underestimated the risks, and should have been more "blunt" about the threat posed to the economy by rising temperatures . Speaking at Davos, Stern said 

 "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. Some of the effects are coming through more quickly than we thought then."

The Stern review pointed to a 75% chance that global temperatures would rise by between two and three degrees above the long-term average but he says he now believes we are "on track for something like four ".

Had he known how things would go  he says, "I think I would have been a bit more blunt. I would have been much more strong about the risks of a four- or five-degree rise."

He said some countries, including China, had now started to grasp the seriousness of the risks, but governments should now act forcefully to shift their economies towards less energy-intensive, more environmentally sustainable technologies.

"This is potentially so dangerous that we have to act strongly. Do we want to play Russian roulette with two bullets or one? These risks for many people are existential."

He called also for more investment in green economies "It's a very exciting growth story' he said.