What is the chance of effective action to curb climate change? “Not much” is the answer. This is not because the costs of action would be prohibitive, at least according to the report on climate change by Sir Nicholas Stern published last week.* It is because the obstacles to achieving the necessary global co-operation are so steep. Sceptics worry that costly action is likely. But believers in climate change have far better reason to be worried.

The report produced by Sir Nicholas last week called for efforts to stabilise greenhouse gas concentrations at between 450 and 550 parts per million by 2050. By then, global emissions would have to be at least 25 per cent below current levels, even though the world economy may be between three and four times bigger.