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.

The WMO Global Atmosphere Watch Programme coordinates systematic observations and analysis of atmospheric composition, including greenhouse gases and other trace species. The GAW CO2, CH4 and N2O networks are comprehensive and baseline networks of the Global Climate Observing System (GCOS). Measurement data are reported by participating countries and archived and distributed by the World Data Centre for Greenhouse Gases (WDCGG) at the Japan Meteorological Agency. Statistics on global atmospheric abundances in 2010 and changes in abundance since 2009 and 1750 for the three major greenhouse gases are obtained from a global analysis (GAW Report No. 184) of datasets that are traceable to the WMO World Reference Standard. Data from mobile stations, with the exception of NOAA flask sampling in the Pacific, are not used for this global analysis.

The three greenhouse gases summarized in the table have been increasing in the atmosphere since the beginning of the industrial era. Their atmospheric abundances are directly connected with human activity, unlike water vapour, which is the most important greenhouse gas but whose abundance is controlled by fast climate feedbacks. They are generally much longer lived in the atmosphere than water vapour. The three primary greenhouse gases are not only closely linked to anthropogenic activities, but they also have strong interactions with the biosphere and the oceans. Chemical reactions in the atmosphere affect their abundances as well.

World Meteorological Organization Greenhouse Gas Bulletin No. 7, 21 November 2011