Reduced Carbon Emission Estimates from Fossil Fuel Combustion and Cement Production in China

China is the world's largest emitter of CO2 emissions, has per capita CO2 emissions 50 percent higher than the world average, and in the last decade emissions have grown at 5–10 percent per year. To keep the global temperature increase to below 2°C above pre-industrial levels requires unprecedented emission reductions from China.

A new international study, led by Zhu Liu from Harvard Kennedy School's Belfer Center for Science and International Affairs and published in the journal Nature, finds that Chinese CO2 emissions may be more than 10 percent lower than previously estimated in most international datasets. Zhu Liu and colleagues reassessed China's carbon emissions from the burning of fossil fuels and the production of cement between 1950–2013 using new measurements of emission factors (the amount of carbon oxidized per unit of fuel consumed) and updated energy consumption data. They estimate that China's emissions were 14 percent lower than estimates by the Emission Database for Global Atmospheric Research in 2013 and 12 percent lower than the latest inventory China reported to the United Nations Framework Convention on Climate Change in 2005. The authors attribute the difference mainly to the emission factors used to estimate emissions from coal combustion, and that the emission factors for coal were on average 40 percent lower than the default values recommended by the Intergovernmental Panel on Climate Change. Emissions from cement production were 32–45 perecnt lower than previous estimates.

The findings suggest that overestimation of China's emissions in 2000–2013 may be larger than China's estimated total forest sink in 1990–2007 or China's land carbon sink in 2000–2009. The revisions of the Chinese emissions are substantial enough that they may lead to adjustments in the Global Carbon Cycle.