Measurements of atmospheric methane in US higher than estimated

New York Times : The first comprehensive direct measurement of atmospheric methane levels in the US has revealed that actual levels are 1.5 to 1.7 times higher than estimates made by the Environmental Protection Agency and an international greenhouse gas monitoring effort. Scot Miller of Harvard University and his colleagues used ground and aerial samples collected from 2007 to 2008 and combined them with computer models to determine the overall US levels of methane. The EPA and other groups made their calculations by using unit-based estimates of methane release from oil and gas drilling and animals. Leaks from drilling operations are one of the major sources of atmospheric methane. Because of increased controls on oil and gas drilling that were put in place in 2008, the researchers are hoping that measurements from more recent years will provide an even clearer picture of the amount of methane above the US.