WMO Greenhouse Gas Bulletin - No.13: The State of Greenhouse Gases in the Atmosphere Based on Global Observations through 2016

The report shows that globally averaged surface mole fractions(2) calculated from this in situ network for CO2, methane (CH4) and nitrous oxide (N2O) reached new highs in 2016, with CO2 at 403.3 ± 0.1 ppm, CH4 at 1 853 ± 2 ppb(3) and N2O at 328.9 ± 0.1 ppb. These values constitute, respectively, 145%, 257% and 122% of pre-industrial (before 1750) levels. The record increase of 3.3 ppm in CO2 from 2015 to 2016 was larger than the previous record increase, observed from 2012 to 2013, and the average growth rate over the last decade. The El Niño event in 2015/2016 contributed to the increased growth rate through complex two-way interactions between climate change and the carbon cycle. The increase of CH4 from 2015 to 2016 was slightly smaller than that observed from 2014 to 2015, but larger than the average over the last decade. The increase of N2O from 2015 to 2016 was also slightly smaller than that observed from 2014 to 2015 and the average growth rate over the past 10 years. The National Oceanic and Atmospheric Administration (NOAA) Annual Greenhouse Gas Index (AGGI) [3, 4] shows that from 1990 to 2016, radiative forcing by long-lived greenhouse gases (LLGHGs) increased by 40%, with CO2 accounting for about 80% of this increase.