By 2020, China will have cut the equivalent of 2.5 giga tons worth of CO2 emissions thanks to its 40 to 45 carbon intensity target, a reduction that is three times that of 0.8 giga tons worth of the CO2 emissions the US will cut during the same period, the report said.

China has pledged greater cuts in greenhouse gas emissions than the US, as calculated by the secretariat of the UN Framework Convention on Climate Change.

In contrast, China accounts for 8.62 percent of cumulative emissions and has about 20 percent of the world's population.

Although the US has less than five percent of the global population, it accounts for 29 percent of the global cumulative emissions (between 1850 and 2006) that are causing climate change, according to the report, which is based on calculations from the World Resources Institute.