It seems unlikely that pledges made at last year’s UN summit in Copenhagen will keep global warming below 2C, according to a study in the journal Nature. In fact, analysts at the Potsdam Institute for Climate Impacts Research in Germany suggest that a rise of at least 3C by 2100 is likely.

To make matters worse, many countries, including EU members and China, have pledged slower carbon curbs than they have already been achieving. Some commentators have remarked that these pledges are in fact nothing more than vague statements of intent.

"There's a big mismatch between the ambitious goal, which is 2C... and the emissions reductions," said Potsdam's Malte Meinshausen. “It is like racing towards the cliff and hoping you stop just before it.”

Between now and 2020, global emissions are likely to rise by 10-20%, they calculate, and the chances of passing 3C by 2100 are now much more likely.

According to the Intergovernmental Panel on Climate Change (IPCC), this will cause a number of serious problems including:

• Falls in crop yields across most of the world
• Further damage to coral reefs
• Disruption of water supplies for hundreds of millions of people

In the UK, the current government’s intention to press ahead with an extra runway at Heathrow would, if implemented, make its carbon reduction targets almost impossible.