Global Warming Potential

Global warming potential (GWP) is a measure of how much a given mass of greenhouse gas is estimated to contribute to global warming. It is a relative scale which compares the gas in question to that of the same mass of carbon dioxide (whose GWP is by definition 1). A GWP is calculated over a specific time interval and the value of this must be stated whenever a GWP is quoted or else the value is meaningless.
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The ratio of the warming caused by a substance to the warming caused by a similar mass of carbon dioxide. CFC-12, for example, has a GWP of 8,500, while water has a GWP of zero. (See: Class I Substance and Class II Substance.)

The index used to translate the level of emissions of various gases into a common measure in order to compare the relative radiative forcing of different gases without directly calculating the changes in atmospheric concentrations. GWPs are calculated as the ratio of the radiative forcing that would result from the emissions of one kilogram of a greenhouse gas to that from emission of one kilogram of carbon dioxide over a period of time (usually 100 years). The chart below shows the original GWPs (assigned in 1990) and the most recent GWPs (assigned in 1996) for the most important greenhouse gases. GASGWP 1990GWP 1996 Carbon Dioxide11 Methane2221 Nitrous Oxide270310 HFC-134a1,2001,300 HFC-2310,00011,700 HFC-152a150140 HCF-125NA*2,800 PFCs**5,4007,850 SF6NA*23,900 * Not Applicable. GWP was not yet estimated for this gas. **This figure is an average GWP for the two PFCs, CF4 and C2F6. See radiative forcing, carbon equivalent, carbon dioxide equivalent.