The Intergovernmental Panel on Climate Change defined global warming potential in 2021 as an index measuring radiative forcing following the emission of a unit mass of a given substance. This definition accumulates the effect over a chosen time horizon relative to carbon dioxide which serves as the reference substance with a GWP value of exactly one.
Methane exhibits a GWP of 83 over a twenty-year period according to the IPCC Sixth Assessment Report from 2021 and drops to a GWP of 30 when measured over one hundred years. Sulfur hexafluoride shows the opposite pattern with a GWP of 17,500 over two decades and 23,500 over a century while nitrous oxide maintains a lifetime of 109 years resulting in consistent high values across different scales.
The Kigali Amendment adopted on the 15th of October 2016 set global phase-down targets for hydrofluorocarbons. This agreement requires countries to use GWP-100 values published in the IPCC Fourth Assessment Report to maintain one comparison metric instead of changing values with new reports.
Sulfur hexafluoride stays in the atmosphere for 3,200 years making it extremely persistent while methane persists for approximately twelve years and nitrous oxide remains for about 109 years. Carbon dioxide has an atmospheric lifetime that cannot be given as a single number due to complex cycles.
Scientists determine global warming potential by analyzing infrared absorption spectra and atmospheric decay rates where radiative forcing capacity represents energy absorbed per unit area and time that would otherwise escape to space. The formula integrates absorbance across wavenumber intervals of ten inverse centimeters and uses corresponding quantities for the reference gas carbon dioxide in the denominator of the calculation.