GWP20

GWP20 stands for Global Warming Potential over a 20-year horizon. It is a metric used to compare the climate impact of greenhouse gases relative to carbon dioxide, expressing the integrated radiative forcing that a kilogram of a gas would produce over a 20-year period in relation to a kilogram of CO2.

The calculation of GWP20 mirrors that of GWP in general: it combines the gas-specific radiative efficiency with its atmospheric lifetime to estimate how much warming a given emission contributes within 20 years. Because gases differ in how long they persist in the atmosphere, GWP20 emphasizes the near-term warming potential, giving short-lived gases a comparatively larger weight than at longer horizons.

GWP20 is used in some analyses of near-term climate policy, life-cycle assessment, and research focusing on short-lived climate pollutants. It is not as universally standardized or widely adopted as GWP100, and there is no single official global GWP20 value set. Different climate models and data sources can yield different numbers for the same gas, depending on assumptions about emissions timing, lifetimes, and spectral absorption.

Because the horizon is shorter than 100 years, GWP20 highlights the near-term impacts of gases such as methane more strongly than GWP100 does. CO2 remains the baseline with a GWP of 1 by definition, while other gases diverge more markedly across horizons.

Limitations of GWP20 include its sensitivity to assumed lifetimes and emission scenarios, potential inconsistencies across calculations, and the fact that it does not capture non-linear climate feedbacks or policy contexts. It is not a substitute for GWP100 in standard policy frameworks but serves as a complementary tool for evaluating short-term climate effects.