Feb. 1 (UPI) -- The amount of methane and ethane emitted by the oil and gas industry in recent decades has been underestimated.
According to researchers at the International Institute for Applied Systems Analysis, in Austria, oil production released greater amounts of methane and ethane between 1980 and 2012 than scientists previously thought.
"In an oil reservoir, there is a layer of gas above the oil which has a methane content of 50 to 85 percent," IIASA researcher Lena Hoglund-Isaksson said in a news release. "When you pump the oil to the surface this associated gas will also escape."
In the United States, most of the gas is recovered. Most of the rest is burned, with a relatively small amount leaked into the atmosphere. Gas operations in other parts of the world aren't as efficient, but researchers have failed to account for global differences in gas production when previously calculating emissions.
"Existing global bottom-up emission inventories of methane used rather simplistic approaches for estimating methane from oil production, merely taking the few direct measurements that exist from North American oil fields and scaling them with oil production worldwide," said Hoglund-Isaksson.
In the study, researchers took a more exacting approach, recognizing global difference in gas production technologies. They shared their findings in the journal Environmental Research Letters.
Methane and ethane emissions have remained relatively stable since 2005. Over the past decade, gas capture technologies have improved. However, increased shale gas drilling has offset reductions.
Researchers say there remains room for improvement in methane emissions monitoring.
"To improve the data, a close collaboration between the scientific measurement community and the oil and gas industry would be needed to make more direct measurements available from different parts of the world," Hoglund-Isaksson said.
Previous studies have shown even small leaks at gas extraction sites can add up. Still, most of the blame lies with the biggest leakers. Researchers in the United States have also found oil and gas operations routinely underestimate their contributions to methane emissions.
Scientists estimate up to 25 percent of man-made global warming is triggered by methane emissions.