U.S. emissions of methane — a greenhouse gas — are probably 50 percent higher than current estimates show, according to a study published yesterday in the Proceedings of the National Academy of Science. The study estimated emissions in 2007 and 2008, using measurements on the ground, in telecommunications towers and from aircraft for a comprehensive inventory of the second most abundant greenhouse gas after carbon dioxide. It found that the U.S. now underestimates methane releases from the raising of livestock and the extraction of oil and natural gas. That may mean methane has a bigger role in climate change than now thought, as state officials and the U.S. Environmental Protection Agency consider new rules designed to limit emissions that may lead to global warming. “Methane is a powerful climate change pollutant, and the study gives greater impetus to the EPA and states to establish stronger standards to reduce leaks […]