GWP100

GWP100, or the 100-year Global Warming Potential, is a metric used to compare the warming impact of greenhouse gases relative to carbon dioxide over a 100-year time horizon. It expresses the integrated radiative forcing per unit mass of a gas over a century, with CO2 assigned a GWP of 1. A gas with a higher GWP100 contributes more warming than CO2 per tonne over the same period.

GWP100 values are derived from climate-model simulations and emissions scenarios compiled by assessments such as the IPCC. Common examples include methane (CH4) with a GWP100 around 28, nitrous oxide (N2O) around 265, and sulfur hexafluoride (SF6) around 23,500; many fluorinated gases span wide ranges. The exact numbers vary by gas and by assessment, and the choice of a 100-year horizon is itself a policy and scientific assumption. The metric reflects both the gas’s atmospheric lifetime and its radiative efficiency.

GWP100 is widely used to convert non-CO2 emissions into CO2-equivalents (CO2e) for national inventories, policy planning, carbon accounting, and life-cycle assessment.

Limitations include its dependence on the chosen time horizon, simplifications of climate response, and timing of emissions. Because short-lived gases can appear more or less impactful depending on horizon, and because GWP does not capture all aspects of climate change, complementary metrics such as alternative time horizons or approaches like GWP* have been proposed.