Carbon trading was worth about $64bn last year, after a sharp rise in numbers of transactions in the fledgling market for greenhouse gases, the World Bank reckons.

In its annual review of the emissions trading market, it said the value of trades more than doubled from 2006 to 2007. The European Union’s emissions trading scheme (EU ETS) made up the bulk of the market, as it has done since its inception in January 2005.