What metric compares a greenhouse gas's warming effect with carbon dioxide?

What metric compares a greenhouse gas’s warming effect with carbon dioxide? Global warming potential is the metric that compares a greenhouse gas’s warming effect with carbon dioxide.

Usually abbreviated GWP, this index compares the time-integrated radiative forcing from emitting a unit mass of a gas with that from the same mass of carbon dioxide. It combines two important properties: how effectively the gas absorbs infrared radiation and how long it persists in the atmosphere.

The time horizon matters. GWP-20 emphasizes effects over 20 years, while GWP-100 averages the comparison over a century. Short-lived gases can have especially high values over a short horizon, but their relative value generally falls over longer periods as they are removed from the atmosphere.

GWP is not the same as atmospheric concentration, lifetime, or instantaneous warming strength. It is a comparison tool used to express emissions as carbon-dioxide equivalents. Policymakers and scientists use it in inventories, though alternative metrics can produce different comparisons depending on the purpose.