This article provides a short note on Global Warming Potential (GWP).
Global warming potential is an estimate of how much a given mass of any of the aforementioned green-house gases will contribute to the hazards of global warming. The efficiency of the molecules and the atmospheric lifetime of the gas determine the global warming potential of the particular green-house gas.
The global warming potential (GWP) depends on both the efficiency of the molecules as a green-house gas and its atmospheric lifetime. GWP is measured relative to the same mass of CO2 and evaluated for a specific timescale.
Thus, if a gas has a high radiative forcing but also a short lifetime, it will have a large GWP on a 20 year scale but a small one on a 100 year scale. Conversely, if a molecule has a longer atmospheric lifetime than CO2 its GWP will increase with the timescale considered.
Carbon dioxide has a variable atmospheric lifetime, and cannot be specified precisely. Carbon dioxide is defined to have a GWP of 1 over all time periods.
Methane has an atmospheric lifetime of 12 ± 13 years and a GWP of 72 over 20 years, 25 over 100 years and 7.6 over 500 years. The decrease in GWP at longer time is because methane is degraded to water and CO2 through chemical reactions in the atmosphere.
GWP relative to CO2 for several green-house gases are given in table 3.