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What does CO2e mean, and what is GWP?
CO2e — carbon dioxide equivalent — is a common unit that lets different greenhouse gases be added together. Each gas is converted using its Global Warming Potential, or GWP: the number of times more warming it causes than the same mass of CO2 over 100 years.
Methane has a GWP of about 28, so one tonne of methane is reported as roughly 28 tonnes of CO2e. Some refrigerants run into the thousands. This is why a small refrigerant leak can dominate a small business’s Scope 1.
GWP values are revised as the science improves, and each revision comes from an IPCC assessment report. AR5 and AR6 are the two currently in circulation. Because the values differ, two reports using different GWP bases are not strictly comparable, which is why the basis has to be stated.
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Last reviewed 2026-09-04