WASHINGTON, D.C. —
The United States is spewing 50 percent more methane — a potent heat-trapping gas — than the federal government estimates, a new comprehensive scientific study says. Much of it is coming from just three states: Texas, Oklahoma and Kansas.
That means methane may be a bigger global warming issue than thought, scientists say. Methane is 21 times more potent at trapping heat than carbon dioxide, the most abundant global warming gas, although it doesn’t stay in the air as long.
Much of that extra methane, also called natural gas, seems to be coming from livestock, including manure, belches, and flatulence, as well as leaks from refining and drilling for oil and gas, the study says. It was published Monday in the Proceedings of the National Academy of Science.
The study estimates that in 2008, the U.S. poured 49 million tons of methane into the air. That means U.S. methane emissions trapped about as much heat as all the carbon dioxide pollution coming from cars, trucks, and planes in the country in six months.
That’s more than the 32 million tons estimated by the U.S. Environmental Protection Administration or the nearly 29 million tons reckoned by the European Commission.
“Something is very much off in the inventories,” said study co-author Anna Michalak, an Earth scientist at the Carnegie Institution for Science in Stanford, Calif. “The total U.S. impact on the world’s energy budget is different than we thought, and it’s worse.”
EPA spokeswoman Alisha Johnson said her agency hasn’t had time to go through the study yet, but hopes it will help “refine our estimates going forward.”
While the world has a good handle on how much carbon dioxide is pumped into the air, scientists have been more baffled by methane emissions. They have had to use computer models to estimate how much methane is going into that air.