New Scientist: Levels of climate-warming methane – a greenhouse gas 25 times as potent as carbon dioxide – rose abruptly in Earth’s atmosphere last year, and we don’t know why. The concentration of methane, the primary component of natural gas, in the atmosphere has more than doubled since pre-industrial times, but remained largely stable over the last decade or so before rising in 2007, researchers said. This stability in methane levels had led scientists to believe that emissions of the gas …