NOAA-ESRL posts an Annual Greenhouse Gas Index (AGGI) by setting a simple, understandable way to measure the warming-influence of long-lived trace gases and track changes each year.  The AGGI was designed to bridge the gap in understanding of changes in greenhouse gases (GHGs) that exists between scientists and the public.

The AGGI is directy proportional to the direct warming influence ("climate forcings") of the GHGs in the index.  The index quantifies the global climate forcings of CO2, CH4 (methane), N2O (nitrous oxide), CFC12, CFC11 and 15 minor GHGs.  In 2014, the five main GHGs accounted for about 96% of climate forcings by long-lived GHGs since 1750, the pre-industrial baseline used by the IPCC.  The remaining 15 minor halogenated gases contributed about 4%.  The index is based on measurements of long-lived greenhouse gases and, NOAA states, the index contains little uncertainty.

Changes in the AGGI are reported from 1979 (AGGI = 0.785) until present (2014: AGGI = 1.356).   The index uses 1990 as a baseline year with a value of 1.  The index increased every year since 1979.  The chart below shows the similar trajectory of CO2 and the AGGI.

NOAA Annual GHG Index

Source Graphic  NOAA Annual Greenhouse Gas Index (AGGI)



Global Average Abundances of Major, Long-Lived Greenhouse Gases

Global Average Concentrations for Major GHGs

Source Graphic  NOAA Annual Greenhouse Gas Index (AGGI) 





Butler, J.H. & Montzka, S.A. (2015) The NOAA Annual Greenhouse Gas Index (AGGI). Published online Spring 2015, retrieved October 5, 2015, from