Fri, Aug 21, 2015 - Page 6 News List

China’s carbon emissions ‘overstated’

‘LOWER THAN ASSUMED’:A study found China’s share of carbon emissions through coal may be 10% lower than thought, although it remains the world’s largest emitter

NY Times News Service, HONG KONG

Scientists may have been overestimating China’s emissions of carbon dioxide, the main greenhouse gas driving global warming, by more than 10 percent, because of inaccurate assumptions about the country’s coal-burning, according to a study published on Wednesday.

The study’s finding, published in the journal Nature, does not mean that the total level of greenhouse gases in the atmosphere is any lower than scientists had thought. That accumulation is measured independently.

Rather, the finding may affect discussions of how much responsibility China bears for global warming, compared with other nations.

“This doesn’t change the fact that China is still the largest emitter in the world,” said Dabo Guan (關達博), a professor of climate-change economics at the University of East Anglia in England who is one of the paper’s two dozen authors, in a telephone interview from Beijing. “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.”

The study looked in detail at the 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. That means that each tonne of burned coal yields less carbon dioxide than had been thought (as well as less energy, and more ash).

China’s proposed commitments to curtail its emissions of greenhouse gases are crucial to a new international agreement on global warming, which governments hope to reach in Paris late this year. Climate change is also expected to figure in talks between US President Barack Obama and Chinese President Xi Jinping (習近平), when Xi visits the US next month.

Xi last year promised that China’s emissions of carbon dioxide would stop growing by about 2030. Yet uncertainty surrounds just how much of the gas is billowing now from China’s power plants, boilers, motor vehicles and industrial plants.

The scientists behind the new study said they analyzed more detailed information about China’s coal quality, combustion performance across industries and total energy consumption than had previously been used.

“We measured thousands of samples of coal from mines across China and found that the carbon content of the coal being burned in China is actually much lower than what has been assumed in previous estimates of emissions,” Steven Davis, a greenhouse gas scientist at the University of California, Irvine, and one of the authors, said in e-mailed answers to questions.

Estimating a country’s carbon dioxide emissions entails some scientific detective work. Researchers start with information about fossil fuel consumption, and then assess how much carbon is contained in those fuels and what fraction of that carbon is actually combusted and ends up in the atmosphere.

China does not publish official data on annual greenhouse-gas emissions, so “international organizations have to make larger assumptions” than are required for other major countries, said another author of the study, Center for International Climate and Environmental Research-Oslo senior researcher Glen Peters.

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