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Concept
Global warming potential
Summary
Global warming potential (GWP) is a measure of how much infrared thermal radiation a greenhouse gas added to the atmosphere would absorb over a given time frame, as a multiple of the radiation that would be absorbed by the same mass of added carbon dioxide (). GWP is 1 for . For other gases it depends on how strongly the gas absorbs infrared thermal radiation, how quickly the gas leaves the atmosphere, and the time frame being considered. The carbon dioxide equivalent (e or eq or -e) is calculated from GWP. For any gas, it is the mass of that would warm the earth as much as the mass of that gas. Thus it provides a common scale for measuring the climate effects of different gases. It is calculated as GWP times mass of the other gas.
Methane has GWP (over 20 years) of 81.2 meaning that, for example, a leak of a tonne of methane is equivalent to emitting 81.2 tonnes of carbon dioxide. Similarly a tonne of nitrous oxide, from manure or paddy fields for example, is equivalent to 273 tonnes of carbon dioxide.
Carbon dioxide is the reference. It has a GWP of 1 regardless of the time period used. emissions cause increases in atmospheric concentrations of that will last thousands of years.
Estimates of GWP values over 20, 100 and 500 years are periodically compiled and revised in reports from the Intergovernmental Panel on Climate Change. The most recent report is the IPCC Sixth Assessment Report (Working Group I) from 2023. Earlier reports were the Second Assessment Report (1995), Third Assessment Report (2001), Fourth Assessment Report (2007) and Fifth Assessment Report (2013).
Though recent reports reflect more scientific accuracy, countries and companies continue to use SAR and AR4 values for reasons of comparison in their emission reports. AR5 has skipped 500 year values but introduced GWP estimations including the climate-carbon feedback (f) with a large amount of uncertainty.
The IPCC lists many other substances not shown here. Some have high GWP but only a low concentration in the atmosphere.
Official source
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