President Barack Obama’s plan to fight global warming underestimates pollution from natural gas, according to scientists studying how leaks affect the climate.
The U.S. Environmental Protection Agency this week proposed requiring power plants to cut greenhouse-gas emissions 30 percent from their 2005 levels by 2030, largely by burning natural gas instead of coal.
Researchers from Cornell University, Stanford University and the U.S. National Oceanic and Atmospheric Administration agree with the EPA that natural gas emits about half as much carbon dioxide as coal when burned to produce electricity. The issue is that methane leaks while natural gas is being extracted, processed and transported, and methane causes more warming than equivalent amounts of carbon dioxide, they said.
“Converting to natural gas plants, which is what this latest rule is likely to do, will actually aggravate climate change, not make things better,” said Robert Howarth, a professor of ecology and environmental biology at Cornell in Ithaca, New York, and the co-author of a 2011 study published in the journal Climatic Change Letters. “It’s well enough established to suggest the EPA is on the wrong side of the science.”
The EPA is evaluating how studies can be used to update its methane emission estimates, including how regional data might fit into a national picture, Liz Purchia, an agency spokeswoman, said in an e-mailed statement. More information will come from government, academic and industry researchers, she said.
“We’re confident that natural gas can play an important role in cutting carbon pollution from power plants, along with energy efficiency, renewable energy and other technologies,” Purchia said in the e-mail. The agency is taking steps to reduce methane emissions and to better measure and monitor those emissions, she said.
While studies suggest the EPA is underestimating methane leaks, it’s not yet certain whether those leaks are big enough to offset the advantage to the climate of natural gas over coal, said Rob Jackson, a Stanford earth sciences professor.
“These rules will almost certainly lead to increased natural gas use for electricity, which highlights the need to cut methane leaks from natural gas infrastructure,” Jackson said. “If methane emissions from natural gas extraction are higher than the EPA estimates, then the climate benefits of switching from coal to natural gas is smaller than they think.”
Obama, who calls natural gas a bridge to a cleaner energy future, is taking a political risk with the country’s boldest single step to restrain rising global temperatures.
His plan conflicts with mounting evidence from peer-reviewed scientific research and data collected by other government agencies that suggest swapping coal for natural gas has little to no net benefits for the climate.
When researchers from NOAA’s Earth System Research Laboratory measured methane from oil and gas sites in Colorado, the amounts were three times greater than predicted, according to a May study published by the Journal of Geophysical Research: Atmospheres.
“You don’t get natural gas at the gas-fired power plant out of a bottle -- it comes out of thousands of wells, and those wells are dirty,” said Anthony Ingraffea, a Cornell civil and environmental engineering professor and co-author of the 2011 study. “You don’t win, you lose, in the climate change battle if you switch from coal to methane.”
The EPA could be underestimating methane emissions by as much as 50 percent, according to a November 2013 study in the Proceedings of the National Academy of Sciences. A nationwide atmospheric test, published in February in the journal Science by a team led by Stanford Professor Adam Brandt, came to a similar conclusion. The leaks from drilling and transporting natural gas would erase the benefits of using the fuel to power vehicles, the authors said.
The EPA is not only underestimating the amount of methane that leaks, but also the effect of that gas, Ingraffea said. The agency says methane is 21 times more potent than carbon dioxide in warming the planet over a 100-year period, using a 1990s estimate from the Geneva-based Intergovernmental Panel on Climate Change. The United Nations group, which was awarded a Nobel Peace Prize in 2007, has since revised the figure to 34 times.
Starting next year, the EPA will increase its estimate to 25 times, reflecting the update from the UN’s 2007 climate change report. The agency plans to provide methane estimates in tons so researchers can calculate their own estimates of the gas’s effects on global temperatures, according to Purchia’s e-mailed statement.
In March, the Obama administration pledged to work with utilities to curb leaks from the transport and distribution of natural gas and called for the EPA to determine whether rules on drilling are needed. The agency published five technical papers on methane emissions from oil and gas in April and will decide how to proceed this fall. If it decides to develop new regulations, it would finish them in 2016.
The Bureau of Land Management is also developing controls on releasing or burning off gas from drilling operations on federal property, due later this year.
Fixing leaks sometimes pays for itself because companies can sell the gas that would otherwise be wasted, according to the Clean Air Task Force, an environmental group that supports the Obama’s plan. Even if leaks were double the EPA’s estimates, they would still only offset about 5 or 6 percent of the reduced emissions from power plants switching to natural gas because coal also seeps methane, said David McCabe, an atmospheric scientist at the Washington-based organization.
“You really need to look at the net effect of everything that comes out,” said Drew Shindell, a researcher in New York at the National Aeronautics and Space Administration Goddard Institute for Space Studies. “If you switch to natural gas but have extremely leaky systems, you wouldn’t do nearly as much good as you thought you would.”
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