Global Warming Potential (GWP) Calculator

GWP is a measure of how much total energy a given mass of a greenhouse gas traps in the atmosphere over a chosen time horizon (usually 20 or 100 years), relative to the same mass of CO2, which is defined as GWP = 1. A gas with GWP = 25 traps roughly 25 times more energy per kilogram than CO2 over that horizon.

Per IPCC AR6, fossil methane has a GWP100 of about 29.8 and a GWP20 of about 82.5. Biogenic (non-fossil) methane is slightly lower, at about 27.0 (GWP100) and 79.7 (GWP20), because fossil methane's carbon adds a small extra CO2-oxidation forcing that biogenic methane does not.

IPCC AR6 gives N2O a GWP100 of about 273, meaning one tonne of N2O has roughly the same 100-year warming effect as 273 tonnes of CO2. N2O's GWP20 is similar, around 273, because its long atmospheric lifetime (about 109 years) means its relative forcing does not change sharply between the two horizons.

CO2e = mass of gas x GWP. The mass is entered in tonnes and the GWP is either a preset IPCC AR6 value selected from the gas dropdown or a custom value you type in directly. The result is the CO2-equivalent mass in tonnes CO2e.

Sulfur hexafluoride (SF6) has a GWP100 of about 25,200 because it absorbs infrared radiation strongly and persists in the atmosphere for roughly 3,200 years, compared to about 12 years for methane and 109 years for N2O. A gas that barely breaks down keeps contributing to warming for far longer, which the 100-year GWP captures as a much larger cumulative effect.

GWP100 integrates a gas's radiative effect over 100 years and is the standard used in most national emissions inventories and climate policy. GWP20 integrates over only 20 years, which weights short-lived, potent gases like methane much more heavily because their effect is concentrated in the near term rather than spread over a century.

The values are IPCC AR6 central estimates, but the IPCC itself reports GWP with real uncertainty, generally plus or minus 30 to 40 percent depending on the gas, because of uncertainties in atmospheric lifetime and radiative efficiency measurements. Treat every GWP figure here as an illustrative central estimate, not an exact constant.

Yes. Select Custom / other gas from the dropdown and type in the GWP value for your gas of interest, sourced from an IPCC assessment report or a national inventory guideline (such as the IPCC AR6 GWP tables, which list dozens of additional fluorinated gases).

GWP is defined as a ratio relative to CO2's own warming effect over the same time horizon, so CO2 divided by itself always equals 1 by construction. This does not mean CO2 has a small warming effect; it means every other gas's GWP is expressed as a multiple of CO2's own substantial effect.

No. CO2e (carbon dioxide equivalent) is a common accounting unit that converts the warming effect of any greenhouse gas into the mass of CO2 that would cause the same warming over the chosen time horizon. A report stating total emissions in CO2e is combining CO2, methane, N2O, and other gases into one comparable number, not reporting only actual CO2 released.

Successive IPCC reports periodically revise GWP values as scientific understanding of atmospheric lifetimes, radiative efficiencies, and background CO2 concentrations improves. HFC-134a's AR6 GWP100 of about 1,526 is lower than earlier assessment report figures, which is why it always matters to specify which IPCC report a cited GWP value comes from.