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China's Carbon Emissions Have Been Overestimated for Over 10 Years

A new paper by a joint research team comprising scientists from the Shanghai Advanced Research Institute of the Chinese Academy of Sciences (SARI-CAS), Harvard University, Tsinghua University and 21 other research institutions at home and abroad was published in the prestige science journal Nature (Z. Liu, DB. Guan, W. Wei. et al Nature 524, 335–338; 2015) on August 20. A press conference hosted by Dr. Nick Campbell, executive editor of Nature, was held on August 19 to announce the results.


In the paper entitled “Reduced carbon emission estimates from fossil fuel combustion and cement production in China,” the joint team reevaluated China’s carbon emissions using updated energy consumption and clinker production data and two new comprehensive sets of measured emission factors for Chinese coal. The “apparent consumption approach” adopted by the team calculates consumption from a mass balance of domestic fuel production, international trade and international fuelling instead of depending upon energy consumption data, which previous studies have shown to be not very reliable. The results are surprising. They show that Chinese CO2 emissions have been substantially overestimated in recent years: In fact, they are 14 percent less than the estimate in the Emissions Database for Global Atmospheric Research (EDGAR) version 4.2 for 2013. (Note that EDGAR has been adopted by the Intergovernmental Panel on Climate Change as the emission baseline.) In addition, over the period from 2000 to 2013, revised estimates are 2.9 gigatonnes of carbon less than previous estimates of China’s cumulative carbon emissions.



“At the beginning of the project we thought that the emissions might be higher than existing estimates,” said Zhu Liu, an ecologist at Harvard University and lead author of the study. “We were very surprised,” said Dr. Liu. He noted that according to various emission scenarios intended to limit the global temperature increase by 2?C within this century, China’s room to increase emissions is 25-70 percent more than previously estimated.


China is the world's biggest carbon emitter and its emissions account for 25 percent of the entire global amount. However, global CO2 emissions data is mainly provided by various international organizations and databases (e.g., IEA, EDGAR, CDIAC, EIA and CAIT) and China has little influence on these databases. “This is probably the best available estimate of emissions from coal burning in China and that is an important contribution,” said Gregg Marland, a geologist at Appalachian State University and a co-author of the study. The study, funded by Climate Change: Carbon Budget and Relevant Issues, a CAS Strategic Priority Program, will help China to voice its opinions in global energy, economic and environmental policy-making and in international negotiations. In the mean time, the results provide valuable basic data China can use to further carry out carbon emissions reduction and air pollution treatment.


Based on the paper, the estimate of how much CO2 will be produced by burning Chinese coal is around 40 percent less per unit than the figures adopted by the Intergovernmental Panel on Climate Change (IPCC). The coal measurements were collected from mine reports and from a project sponsored by the Chinese Academy of Sciences that assesses the country’s cumulative carbon emissions and carbon uptake by ecosystems across China. “All the data is based on real measurement and analysis of more than 700 coal samples from different places in China, which accounts for 97 percent of the national coal emission categories,” said Professor Wei Wei of SARI-CAS. “The lower heating value of Chinese coal reflects its generally low quality and high ash content, and the carbon contained is much lower compared with developed countries and the average world level, which implies that there is not that much CO2 emission in China’s coal.”






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