Engineering techniques to deflect sunlight from the face of the earth could reduce global warming for just 5 per cent of the cost of cutting carbon emissions, according to a paper published today by two climate change economists.

The paper comes ahead of a meeting in Copenhagen in December, where governments will discuss cutting carbon emissions to fight climate change. It concludes that using the lowest cost technologies, such as making clouds whiter to reflect sunlight, could achieve the same cooling effect as emissions cuts being discussed by the United Nations for only about $9bn (€6bn, £5bn).