A new study by Harvard University researchers on greenhouse gas emissions in the US claims that the level of methane leaks into the atmosphere may be 50% higher than suggested by the Environmental Protection Agency (EPA).
The study claims that methane emissions from human activities such as natural gas production or livestock raising were twice as high, or higher, than EPA estimates, while in some south-central regions, emissions from fossil fuel extraction and refining may be up to five times higher than estimated.
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"Our numbers for the entire US are about a factor of 1.5 times larger than the EPA’s estimate," says the study's co-author Scot Miller, a doctoral student at Harvard University. He said that the numbers present a serious discrepancy, considering the hundreds of millions of tons of a very potent greenhouse gas going up every year.
The new study is based on data from some 13,000 measurements of atmospheric methane levels taken in 2007 and 2008, just as natural gas production from fracking was starting to ramp up.
The researchers then used weather data and other information to extrapolate the likely sources of the methane. They plan to use the data as a baseline to see how emissions have changed in more recent years.
"We don't know why there's such a discrepancy,” says co-author Steven Wofsy, an atmospheric and environmental professor at Harvard University's School of Engineering and Applied Science. He said it may be that the EPA is not measuring every possible source such as broken natural gas pipes that are leaking methane.
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“This discrepancy casts doubt on the agency's recent decision to downscale its estimate of national natural gas emissions by 25 to 30 percent, " the study concluded.
The authors are now examining more recent data, which would account for the sharp increase in oil and gas drilling in the US in recent years.
By. Joao Peixe of Oilprice.com