But since then China has restated its commitment to achieving a 40-45% reduction in carbon emissions per unit of GDP by 2020 compared with 2005.

ECONOMIST: Chinese foreign policy

If the American Senate were to pass a climate bill that put a significant cost on carbon, and thus provided cuts of the same size as those expected under the cap-and-trade bill which passed the House of Representatives last year, America would be widely seen as having raised the stakes with a commitment to a reduction of just under 2 billion tonnes of carbon dioxide.

ECONOMIST: What countries are currently offering on climate