A new study from NOAA, the National Oceanic Atmospheric Administration, puts a new twist on a tricky question about the impact of increased oil and gas production on greenhouse gas emissions. Scientists have detected increased rates of methane emissions globally since 2007. That uptick corresponds to the rapid boom in U.S. shale gas and shale oil production, and some hypothesized that the two could be connected. But it turns out that the correlation may not necessarily be a cause.