China's carbon emissions² have been substantially over estimated by international agencies for more than 10 years, according to research co-led by the University of East Anglia. From 2000-2013 China produced 2.9 gigatonnes less carbon than previous estimates of its cumulative³ emissions. The findings suggest that overestimates⁴ of China's emissions during this period may be larger than China's estimated total forest sink - a natural carbon store - in 1990-2007 (2.66 gigatonnes of carbon) or China's land carbon sink in 2000-2009 (2.6 gigatonnes of carbon).

 

Published tomorrow in the journal Nature, the revised estimates of China's carbon emissions were produced by an international team of researchers, led by Harvard University, UEA, the Chinese Academy of Sciences and Tsinghua University, in collaboration⁵ with 15 other international research institutions.

 

The team re-evaluated emissions from the burning of fossil fuels and cement production from 1950-2013. They used independently assessed activity data on the amounts of fuels burned and new measurements of emissions factors - the amount of carbon oxidised per unit of fuel consumed - for Chinese coal.

 

Nearly three-quarters of the growth in global carbon emissions from the burning of fossil fuels and cement production between 2010-2012 occurred in China. Yet estimates of Chinese emissions remain subject to large uncertainty⁶ due to conflicting assessments⁷ of energy consumption and emission¹ factors. Indeed, using different official sources of activity data and emissions factors can result in estimates that vary by up to 40 per cent in a given year.

 

Lead UK researcher Prof Dabo Guan, of UEA's School of International Development, said the key contributor to the new estimates was fuel quality, which for the first time was taken into consideration in establishing emission inventories⁸ - something the Intergovernmental Panel on Climate Change (IPCC) and most international data sources had not.

 

"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," said Prof Guan.

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