Climate Change: Annual greenhouse gas index

Among the most basic questions about global warming is how much are human-produced greenhouse gases influencing the climate today compared to the past? To answer this question, NOAA developed the Annual Greenhouse Gas Index ("AGGI" for short). Updated yearly, the AGGI calculates the combined warming influence of the most important long-lived greenhouse gases: carbon dioxide, methane, nitrous oxide*, and a number of industrial chemicals used in cooling and refrigeration, aerosol sprays, and other processes. The total direct heating influence in a given year is compared to conditions in 1990—the year that countries who signed the U.N. Kyoto Protocol agreed to use as a benchmark for their efforts to reduce emissions. [Correction: Feb 25, 2025. A previous version of this page incorrectly identified the gas as nitrous dioxide.]

The AGGI—short for Annual Greenhouse Gas Index—reports the combined warming influence of all long-lived greenhouse gases as a fraction of their influence in 1990. NOAA Climate.gov graph, based on data from NOAA Global Monitoring Lab.

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