A popular radio comedy series in 1940s Britain featured a sketch in which two excessively polite gentlemen would find themselves unable to pass through a doorway, paralysed by their own good manners. "After you, Claude," one would say. "No, after you, Cecil," came the reply. It could go on for quite a long time.

That is exactly what negotiating international action on climate change feels like, according to David Miliband, the UK's environment minister. “It's an ‘After you, Claude' situation,” he says of the discussions on the international Kyoto protocol. No country wants to be first in taking action to cut their greenhouse emissions for fear that other governments will fail to follow. So they find ways to stall, while their greenhouse gas output climbs steadily skywards.

According to some of the world's leading scientists, climate change poses a bigger threat to future prosperity than wars or terrorism. Yet governments remain reluctant to address this threat because any country acting alone to curb its greenhouse gas emissions, without similar commitments by other governments, risks damaging the competitiveness of its industries. The result: paralysis.

“There is a collective action problem internationally,” says Mr Miliband. “You have to break this logjam.” Attempts to break the logjam are indeed under way, but the risks are high. Many of the government ministers from around the world, meeting at United Nations talks on climate change in Nairobi last month, were wary of committing their countries to farreaching emissions reduction programmes unless they could be sure that large emitters such as the US and China were also taking on such commitments.