WMO Greenhouse Gas Bulletin - No.7: The State of Greenhouse Gases in the Atmosphere Based on Global Observations through 2010

The report shows that the globally averaged mixing ratios of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) reached new highs in 2010, with CO2 at 389.0 ppm,[2] CH4 at 1808 ppb and N2O at 323.2 ppb. These values are greater than those in pre-industrial times (before 1750) by 39%, 158% and 20%, respectively. Atmospheric increases of CO2 and N2O from 2009 to 2010 are consistent with recent years, but they are higher than both those observed from 2008 to 2009 and those averaged over the past 10 years. Atmospheric CH4 continues to increase, consistent with the past three years. The NOAA Annual Greenhouse Gas Index shows that from 1990 to 2010 radiative forcing by long-lived greenhouse gases increased by 29%, with CO2 accounting for nearly 80% of this increase. Radiative forcing of N2O exceeded that of CFC-12, making N2O the third most important longlived greenhouse gas.