China’s carbon emissions overestimated
Chinas carbon emissions may be significantly lower than previously thought about 14% less in 2013 than estimated by the Chinese government and others, according to research published this week in Nature (Z. Liu et al. Nature 524, 335338; 2015). The analysis draws on data from more than 4,200 Chinese mines including new measurements of the energy content of coal among other sources.
At the beginning of the project we thought that the emissions might be higher than existing estimates, says Zhu Liu, an ecologist at Harvard University in Cambridge, Massachusetts, and lead author of the study. We were very surprised.
His teams findings do not unseat China from its position as the worlds largest emitter of carbon dioxide. Even when the lower estimate is taken into account, Chinas carbon output for 2013 is still more than two-thirds higher than that of the United States, the second-largest emitter. But the study underscores long-standing uncertainties in the methods with which scientists calculate the emissions of individual nations, and how much carbon cycles through the atmosphere and into oceans and ecosystems. For comparison, the cumulative reduction in Chinese emissions outlined in the study roughly 2.9 billion tonnes from 2000 to 2013 is larger than the estimated amount of carbon that the worlds forests pulled out of the atmosphere from 1990 to 2007.
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The Chinese government releases data on energy consumption and production at the provincial and national levels, but those statistics often conflict with each other, and are revised frequently. Liu and his team analysed government data on energy production and on exports and imports of coal, oil and gas. They found that Chinas fossil-fuel use was 10% above the official government estimate, but that the countrys overall emissions were lower once Chinas reliance on low-quality coal from domestic mines was taken into account. This is because lower-quality coal contains less carbon than higher-quality deposits, so burning it produces less energy and less heat-trapping CO2.
http://www.nature.com/news/china-s-carbon-emissions-overestimated-1.18199