Keywords: Methane-2009.png en Methane concentration in the atmosphere as measured at the Mauna Loa Observatory ppb http //www esrl noaa gov/gmd/webdata/ccgg/iadv/graph/mlo/mlo_ch4_ts_obs_03397 png NOAA 2009-12-12 PD-USGov Mauna Loa Observatory 19 5362° North / 155 5763° West Methane Greenhouse gases Earth's atmosphere |