China’s emissions have been overestimated, new calculations show

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China’s image as one of the major polluters in the world may be exaggerated to a certain extent, new calculations have shown and according to them the country’s emissions have been substantially over estimated by international agencies for more than 10 years.

The study, which possibly questions the methodologies adopted by Carbon Dioxide Information Analysis Centre (CDIAC) in the US and the Emissions Database for Global Atmospheric Research (EDGAR) in the EU, has considered for the first ever time – the amount of carbon oxidised per unit of fuel consumed – for Chinese coal.

Researchers suggested that none of the previous studies that taken this into consideration despite the fact that China is one of the major consumers of coal. 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 for Chinese coal.

Researchers found that from 2000-2013 China produced 2.9 gigatonnes less carbon than previous estimates of its cumulative emissions. 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 collaboration with 15 other international research institutions.

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

Researchers revealed that China burns much lower quality coal, such as brown coal, and these types of coal are known to have a lower heat value and carbon content compared to the coal burned in other major countries like the US and those in Europe.

Results of the new calculations suggested that Chinese CO2 emissions have been substantially over estimated in recent years. According to them though the total energy consumption in China was 10 per cent higher between 2000-2012 than the value reported by the country’s national statistics, their emission factors for Chinese coal were on average 40 per cent lower than the default levels recommended by the IPCC. Emissions from China’s cement production were 45 per cent less that recent estimates.

These revised estimate put China’s CO2 from fossil fuel combustion and cement production in 2013 at 2.49 gigatonnes of carbon – up to 14 per cent lower than the emissions reported by previous assessments, including those by CDIAC and EDGAR, which are the official data sources for the IPCC Fifth Assessment Report (AR5) – providing scientific evidence for climate change policy negotiations in Paris later this year. The figure is also about 10 per cent less than the estimate given for China in the most recent publication of the Global Carbon Project, which updates annually the global carbon emissions and their implications for future trends.

Prof Corinne Le Quéré, director of the Tyndall Centre for Climate Change Research at UEA, co-leads the publication of annual updates of emissions for the Global Carbon Project. She said there were a lot of uncertainties in Chinese data, especially given discrepancies between national and provincial figures.

“There is still a lot of work to do,” said Prof Le Quéré. “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.”