WASHINGTON, Oct. 13, 2016 - Global methane emissions from fossil fuel development are up to 60 percent greater than estimated by previous studies, according to a new report.
But the analysis shows that fossil fuel facilities are not directly responsible for the increased rate of global atmospheric methane emissions measured between 2007 and 2013 – estimated at some 28 million tons per year.
The study, led by scientists from the National Oceanic and Atmospheric Administration (NOAA) and the Cooperative Institute for Research in Environmental Sciences (CIRES), found that fossil fuel activities contribute between 132 million and 165 million tons of the 623 million tons, or about 20-25 percent, of methane emitted by all sources every year.
“We recognize the findings might seem counterintuitive,” says lead author Stefan Schwietzke, a scientist with CIRES at the University of Colorado, Boulder, working in NOAA’s Earth System Research Laboratory.
The research, recently published in the journal Nature, analyzed the “largest database of methane measurements ever assembled” to determine how much methane is coming from fossil fuel development, as well as other sources – like natural geologic sources, microbial activity and biomass burning.
So, what’s causing the global increase in atmospheric methane levels?
The research points to natural or human-caused microbial sources as the cause of between 364 million to 419 million tons of methane released to the atmosphere each year, or 58 to 67 percent.
“We believe methane produced by microbial sources – cows, agriculture, landfills, wetlands and fresh waters – are responsible for the increase, but we cannot yet pinpoint which are the primary drivers,” Schwietzke says.
“If the methane is mainly coming from cows or ag, then we could potentially do something about it. If it’s coming from decaying vegetation in wetlands or fresh waters, then a warming climate could be the culprit, which means that it could be part of a self-reinforcing feedback loop leading to more climate change. Those are big ifs, and we need to figure them out.”
Schwietzke says that future research would benefit from enlarging the database to add samples from microbial sources, reducing uncertainty about contributions from all methane sources, including fossil fuels. More data, he says, would help better quantify the individual sources.
After carbon dioxide, methane is the second largest contributor to global warming, the researchers say, and while not as abundant or as long-lived as CO2, methane is 28 times more effective at trapping heat in the Earth’s atmosphere over a 100-year time span.
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