WASHINGTON (AP) — 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.