China's emissions overestimated: Is America back on top?

China’s greenhouse gas emissions since 2000 have been much lower than previously estimated, says a new study. In 2007, China overtook the US as the world’s largest emitter of greenhouse gases.

Andy Wong/AP/File
A man rides an electric bike across a street shrouded by haze in Beijing, Jan. 10, 2012. China's carbon emissions may be less than previously estimated, a new study claims.

New research reveals China’s carbon emissions were overestimated for more than a decade by international agencies.

According to the study, published in the current issue of Nature, China emitted 2.9 gigatons less carbon from 2000 to 2013 than previous estimates. 

The paper said 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.

The researchers, led by Dabo Guan, chair of climate change economics at the University of East Anglia in England, analyzed coal used as fuel in China, and found that it is generally less rich in carbon and is burned less efficiently than scientists had assumed.

The study examined fuel quality in great detail – something the authors say is missing from other estimates.

"While China is the largest coal consumer in the world, 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," Professor Guan said.

China has never been forthright about annual carbon emissions, so “international organizations have to make larger assumptions” than are required for other key nations, Glen Peters, another author of the study, told The New York Times.

Indeed, the study found that China's total energy consumption since 2000 was 10 percent higher than the government reported – but that even so, emissions for Chinese coal were on average 40 percent lower than the default values recommended by the Intergovernmental Panel on Climate Change.

But China still has a long way to go.

“This doesn’t change the fact that China is still the largest emitter in the world,” Guan told the Times. “But it shows we need to know a more accurate base line for emissions, not only for China but also for the other emissions giants.”

A recent study attributed a startling new death toll to China’s toxic air problem. The study by researchers from Berkeley Earth indicated that air pollution is killing more than 4,000 people in China per day. That’s about 1.6 million every year, or 17 percent of all deaths.

China overtook the United States as the world’s largest emitter of greenhouse gases in 2007 – and has retained that spot ever since. But last year, the country pledged to cut emissions by 2030 through improved enforcement efforts and by increasing its use of renewable, zero-emission energy sources to 20 percent of its total energy budget.

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