Alternative climate metrics to the Global Warming Potential are more suitable for assessing aviation non-CO₂ effects

A growing body of research has highlighted the major contribution of aviation non-CO₂ emissions and effects to anthropogenic climate change. Regulation of these emissions (e.g., in the EU Emissions Trading System) requires the use of a climate metric, but choosing a suitable one is challenging due to high uncertainties, varying atmospheric lifetimes and efficacies, and dependence on emission location and altitude. Using the AirClim model, the study explores alternatives to the conventional Global Warming Potential (GWP) by analysing neutrality, temporal stability, compatibility and simplicity of existing climate metrics and performing a trade-off. The authors find that using the temperature-based Average Temperature Response (ATR) or an Efficacy-weighted GWP (EGWP) would enable a more accurate assessment of existing and future aircraft, including those powered by novel aviation fuels. They recommend further research into the potential use of the EGWP and into updated efficacy estimates for aviation non-CO₂ emissions.