The political problem with climate change is that it veers from the apocalyptic to the trivial. Glaciers are melting, so turn off the red button on the television. It is still possible that discussion at the Copenhagen summit could produce the pragmatic deal that is the intermediate point between idealism and fatalism.
Success will require great ambition. Lord Stern, the author of the Government’s weightiest tome on climate change, has said that global greenhouse gas emissions, currently 47 gigatons, need to be at 44 gigatons by 2020 to get on course to hold the rise in global temperature this century to 2C. Hitting this target would require all the signatory nations to consent to the upper end of their professed targets.