WMO Greenhouse Gas Bulletin - No.11: The State of Greenhouse Gases in the Atmosphere Based on Global Observations through 2014

The report shows that the globally averaged mole fractions of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) reached new highs in 2014, with CO2 at 397.7±0.1 ppm, CH4 at 1833±1 ppb[2] and N2O at 327.1±0.1 ppb. These values constitute, respectively, 143%, 254% and 121% of pre-industrial (1750) levels. The atmospheric increase of CO2 from 2013 to 2014 was close to that averaged over the past 10 years. For both CH4 and N2O the increases from 2013 to 2014 were larger than that observed from 2012 to 2013 and the mean rates over the past 10 years. The National Oceanic and Atmospheric Administration (NOAA) Annual Greenhouse Gas Index shows that from 1990 to 2014 radiative forcing by long-lived greenhouse gases (LLGHGs) increased by 36%, with CO2 accounting for about 80% of this increase.