Climatologists are to meet in Oxford next week for a deeply depressing conference. Over three days they will discuss the world warming by potentially a calamitous 4°C as a result of human activities.

Such a temperature rise is about twice that forecast by the Intergovernmental Panel on Climate Change in 2007. Scientists and increasingly politicians concur that the 2°C predicted in that IPCC report is the level beyond which global warming may have dire consequences.