China has left USA lagging behind in its spending on clean energy-but it still has much to do if it is to shake off its sooty tag.

According to a study released by washington based think tank Worldwatch Institute, China has ploughed more than $10bn-£5bn on renewables energy last year - double the amount  invested by the US in 2006. China is set to meet its targets of 15-per-cent energy from renewables by 2020, up from 8-per-cent. Eric Martinot has said, "I think targets are realistic, even conservative based on what they have done so far".

However China emits seventy-percent of its energy from coal compared with less than 25-per-cent in the US.