According to a study published by Nature magazine on Wednesday, organizations like the European Union's Emissions Database for Global Atmospheric Research (EDGAR) have overestimated China's emissions by as much as 14 percent by using default conversion rates that should not apply in China.

From 2000 to 2013, the country produced nearly three billion tons less carbon than previously thought. That is a figure that is equivalent to roughly a third of current global annual emissions.

The new estimate, however, does not change China's rank as the world's top carbon polluter.

"China's total emissions as a country are still well above the second big emitter, which is the United States," said Corinne Le Quere, director of the Tyndall Centre for Climate Change Research in East Anglia, in the United Kingdom.

Still far more than in US and EU

Roughly 70 percent of China's total greenhouse gas emissions come from coal, far more than in the United States or the European Union.

Previous calculations did not sufficiently take into account the fact that China -- which consumes nearly as much coal as the rest of the world combined -- produces and uses a particularly poor grade of the fossil fuel.

"China burns much lower quality coal, which has a lower heat value and carbon content compared to the coal burned in the US and Europe," explained co-author Dabo Guan, a researcher at Tsinghua University in Beijing.

Even if this "dirtier" coal creates more local air pollution, in other words, its lower energy content also translates into lower carbon dioxide emissions.

It also does not change the overall climate picture. Scientists have long tracked the atmospheric increase in heat-trapping carbon dioxide with great precision.

China giving more efforts in gathering data

The error, in this case, comes from the difficulty of measuring China's massive consumption of coal, said the study, published in the peer-reviewed journal Nature.

While there is no official figure for Chinese carbon emissions last year, estimates stand at around 9-10 billion tons, while forecasts for 2030 range anywhere between 11 billion and 20 billion tons.

Another factor that allowed for the new, more accurate estimate is China's efforts in gathering data, experts say.

"Good accounting is hard enough for a single factory, but for a nation the size of China the sheer number and diversity of emissions sources" makes it a monumental task, said Dave Reay, a professor of carbon management at the University of Edinburgh.

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av/jil (AFP, Reuters)