Global Warming Potential (GWP)
Global warming potential (GWP) is a metric that compares the warming effect of a greenhouse gas relative to CO₂ over a specified time horizon, typically 100 years (GWP-100). It is published by the IPCC and used to convert different greenhouse gases into CO₂ equivalent for emissions inventories.
Each greenhouse gas absorbs different amounts of infrared radiation and persists in the atmosphere for different lengths of time. GWP captures both factors into a single number: how much energy one tonne of a gas will absorb over a given period compared to one tonne of CO₂.
Key GWP-100 values from the IPCC Sixth Assessment Report (AR6): CO₂ = 1, CH₄ (methane) = 27.9, N₂O (nitrous oxide) = 273, SF₆ (sulfur hexafluoride) = 25,200, HFC-134a = 1,530, R-410A = 2,088. GWP-20 values (20-year horizon) are higher for short-lived gases like methane (GWP-20 for CH₄ = 80.8).
GWP values are updated with each IPCC Assessment Report, and different frameworks may specify different report versions. For example, SBTi currently uses AR5 values while CSRD references AR6. Carbon accounting platforms must track which GWP values apply to each reporting requirement and apply them consistently.
The choice of time horizon matters. GWP-100 is the standard, but GWP-20 better captures the urgency of reducing short-lived but potent gases like methane. Some frameworks and jurisdictions are beginning to adopt GWP* or GWP-20 for specific reporting purposes.
Frequently asked questions
What is global warming potential (GWP)? +
GWP is an IPCC metric that compares how much warming one tonne of a greenhouse gas causes relative to one tonne of CO₂ over a specified period, usually 100 years. It is used to convert all GHGs into CO₂ equivalent for standardized emissions reporting.
What is the GWP of methane? +
Using IPCC AR6 values, methane (CH₄) has a GWP-100 of 27.9, meaning one tonne of methane has the same warming effect as 27.9 tonnes of CO₂ over 100 years. Over 20 years (GWP-20), methane's value is 80.8 due to its higher short-term potency.
Related terms
tCO₂e (Tonnes of CO₂ Equivalent)
tCO₂e — tonnes of carbon dioxide equivalent — is the standard unit for expressing greenhouse gas emissions. It normalizes different greenhouse gases (methane, nitrous oxide, HFCs, etc.) to their equivalent warming impact relative to CO₂ using global warming potentials (GWPs), allowing them to be summed into a single comparable metric.
Emission Factor
An emission factor is a coefficient that converts an activity measurement — such as litres of fuel burned, kilowatt-hours of electricity consumed, or dollars spent on a commodity — into a quantity of greenhouse gas emissions, typically expressed in kilograms or tonnes of CO₂ equivalent (tCO₂e).
GHG Protocol
The GHG Protocol is the world's most widely used greenhouse gas accounting standard. Developed by the World Resources Institute (WRI) and the World Business Council for Sustainable Development (WBCSD), it provides frameworks for organizations, cities, and countries to measure and manage their emissions across three scopes.
Carbon Accounting
Carbon accounting is the systematic process of measuring, recording, and reporting the greenhouse gas (GHG) emissions produced by an organization, product, or activity. It follows standardized methodologies — most commonly the GHG Protocol — to quantify emissions across Scope 1 (direct), Scope 2 (purchased energy), and Scope 3 (value chain) categories, producing an auditable inventory that underpins disclosure, reduction planning, and regulatory compliance.