Every crisis, Sigmund Freud said, is potentially a stimulus to the positive side of the personality and an opportunity to start afresh. Today we are facing two global crises in tandem – the economic recession and climate change. Both are deeply worrying, but what is their relationship likely to be?

Freud’s point has not gone unnoticed by the scientists gathering in Copenhagen this week, nor by political leaders. Following the example of Barack Obama, many have signed up to the idea of a climate change new deal. Investment in low-carbon technologies, the insulation of buildings and public transport, it is reasoned, can also make a key contribution to getting the economy moving again.

Nick Stern, in his celebrated review on the economics of climate change, argues that such measures should make up at least 20% of the funding provided for recovery plans. Obama’s proposals fall some way short of that. But other countries are allocating much more. South Korea, for instance, is devoting two-thirds of its recovery package to such ends.