NOAA Earth System Research Laboratory, James.H.Butler; Stephen.A.Montzka; Updated Spring 2014.

“The Annual Green House Gas Index (AGGI) is a measure of the warming influence of long-lived trace gases and how that influence is changing each year. The index was designed to enhance the connection between scientists and society by providing a normalized standard that can be easily understood and followed. The warming influence of long-lived greenhouse gases is well understood by scientists and has been reported by NOAA through a range of national and international assessments. Nevertheless, the language of scientists often eludes policy makers, educators, and the general public. This index is designed to help bridge that gap. The AGGI provides a way for this warming influence to be presented as a simple index…Increases in the abundance of atmospheric greenhouse gases since the industrial revolution are mainly the result of human activity and are largely responsible for the observed increases in global temperature [IPCC 2007]. However, climate projections have model uncertainties that overwhelm the uncertainties in greenhouse gas measurements. We present here an index that is directly proportional to the direct warming influence (also know as climate forcing) supplied from these gases. Because it is based on the observed amounts of long-lived greenhouse gases in the atmosphere, this index contains relatively little uncertainty.”