Global Warming Potential (GWP)
Warming caused by a gas over a time horizon, relative to the same mass of CO₂.
Formula
Variables
Example
Methane has a 100-year GWP of about 28× CO₂
How it works
Global Warming Potential compares the climate impact of a pulse of a gas to the impact of the same mass of carbon dioxide over a chosen time horizon. It works by integrating radiative forcing over time: a gas with higher radiative efficiency warms more per unit mass, but a gas that disappears quickly contributes less warming later on. The denominator uses CO₂ as the reference, so the result is a relative index that depends on both how strongly the gas absorbs infrared radiation and how long it remains in the atmosphere.
When to use it
Use GWP when you need to compare greenhouse gases in climate policy, emissions inventories, or life-cycle assessments. It is especially useful for converting mixed-gas emissions into CO₂-equivalent terms over a specified horizon such as 20, 100, or 500 years.
Worked example, step by step
Suppose a 100-year assessment compares 1 kg of nitrous oxide (N₂O) to 1 kg of CO₂. Assume the integrated warming effect of 1 kg N₂O over 100 years is 2.98 times that of 1 kg CO₂. So, GWP = (warming from N₂O over 100 years) / (warming from CO₂ over 100 years) GWP = 2.98 / 1 GWP = 2.98 Therefore, 1 kg of N₂O has a 100-year GWP of about 298 relative to CO₂ when expressed on the standard mass basis used in climate accounting.
Common mistakes to avoid
- Mixing up the time horizon and comparing gases over different horizons without stating it
- Treating GWP as a fixed property of a gas, even though it changes with the chosen time horizon
- Confusing radiative efficiency with atmospheric lifetime and assuming one alone determines the final GWP
Did You Know?
GWP lets very different gases be compared on a single "CO₂-equivalent" scale.
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