The findings have especially great significance because the U.S. Environmental Protection Agency (EPA) has been grappling with the uncertainty over how much methane is escaping from the nation’s growing shale gas production. (See related “Quiz: What You Don’t Know About Natural Gas.”)

Faced with an onslaught of criticism from the industry that it had overestimated the fugitive emissions, the EPA this year incorporated the industry’s own studies to downgrade its estimate of U.S. methane emissions by 25 to 30 percent. But the study published Monday in the Proceedings of the National Academy of Sciences (PNAS), based on the relatively new data gathered from monitoring stations on tall towers and on aircraft, indicate that U.S. methane emissions instead are