Distinctive efficacies of the components contributing to total aviation climate impact

Abstract

Separate climate sensitivity simulations were run for all important non-CO2 radiative forcing contributions from aviation (except for contrail cirrus), aiming at the quantification of an individual efficacy parameter for each component. All simulations were performed with the same climate model, E39A. The necessity to scale the original perturbations complicates a straightforward determination of efficacy values, particularly for aviation ozone. The results presented here indicate that a radiative forcing from water vapour increase caused by supersonic aviation would have a similar efficacy than CO2. Ozone changes induced by subsonic aviation and methane changes appear to have an efficacy larger than CO2, but the enhancement is moderate (~1.05). For line-shaped contrails we find an efficacy substantially smaller (~0.6) than CO2 in agreement with previous results. The (small) water vapour increase expected from subsonic aviation shows reduced efficacy (~0.7), too. Similar studies with other climate models are desirable in view of probable model dependency.