Climate change: China's carbon emissions have been overestimated for over 10 years

China's carbon emissions have been substantially overestimated by scientists for over a decade, giving the nation a bad reputation it did not necessarily deserve. A study of China's emissions shows it produced 2.9 gigatonnes less carbon than indicated by previous estimates.

Researchers from the University of East Anglia, Harvard University, the Chinese Academy of Sciences and Tsinghua University re-evaluated emissions from the burning of fossil fuels and cement production between 1950 and 2013, using independently assessed activity data on the total amounts of fuels burned, as well as new measurements of emission factors.

Their findings, which were published in the journal Nature, estimated that China's emissions were 14% lower than those estimated by the Emission Database for Global Atmospheric Research in 2013. They were also 12% lower than the last inventory China reported to the United Nations Framework Convention on Climate Change. They also suggest the overestimation between 2000 and 2013 could be larger than China's total forest sink (a natural carbon store) or China's land carbon sink.

While the findings showed the country's total energy consumption between 2000 and 2012 was 10% higher than China reported in its national statistics, emission factors for coal were 40% lower than the levels recommended by the IPCC.

Lead UK researcher Dabo Guan said the biggest contributor to the new estimates is to do with coal consumption: "China is the largest coal consumer in the world, but it burns much lower quality coal, such as brown coal, which has a lower heat value and carbon content compared to the coal burned in the US and Europe. China is one of the first countries to conduct a comprehensive survey for its coal qualities and a global effort is required to help other major coal users, such as India and Indonesia, understand their physical coal consumptions as well as the quality of their coal types.

"Our results suggest that Chinese CO2 emissions have been substantially overestimated in recent years. Evaluating progress towards countries' commitments to reduce CO2 emissions depends upon improving the accuracy of annual emissions estimates and reducing related uncertainties. These findings represent progress towards improving estimates of annual global carbon emissions."

However, Corinne Le Quéré, who co-led the publication of annual updates of emissions for the Global Carbon Project, warned there are still huge uncertainties in data from China on its CO2 emissions: "There is still a lot of work to do. The strong message here is that as we refine our estimates of carbon emissions we get closer to an accurate picture of what is going on and we can improve our climate projections and better inform policy on climate change."

More about China's emissions