E3G, the climate change think-tank that published the report, said reforestation, low-carbon transport, improvements in energy efficiency and investments in renewable power had put the country on a considerably lower trajectory of greenhouse gas emissions than would be expected under “business as usual”.

“China has made significant headway,” said Matthew Findlay, the programme leader at E3G. “But it must meet the targets in its five-year plan and toughen those policies in future plans.”

E3G measured national wealth per unit of carbon emissions to find out which countries would be most competitive under carbon limits. Its finding suggests that if China continued at this pace of improvement it would be able to meet the demands of developed nations at the Copenhagen talks in December, which are intended to forge a new international agreement on climate change.

Rich countries want emerging economies including China and India to take measures such as improving the efficiency of power generation and encouraging development of renewables. Only if such measures are agreed will rich countries provide funds to help poorer nations to cut emissions and adapt to the effects of climate change.

Beijing is already taking such measures under its five-year economic plan.

China's carbon dioxide output is likely to be 40 per cent higher in 2020 than today because of its expected economic growth. But emissions would rise twice as fast if China pursued the high-carbon economic growth of the past.

The “carbon dioxide intensity of gross domestic product” in China will halve in the next decade, the report says. This means China will be able to curb the growth of its emissions between now and 2020 to the extent necessary to hold global temperatures to no more than 2°C above pre-industrial levels. Such a temperature rise is seen as the limit of safety, beyond which the effects of climate change become irreversible.

But the analysis also pointed to a possible problem in that China's rate of emissions reduction slowed from 2000 to 2005 before recovering from 2005 on, owing to improvements in energy efficiency.