Intermodel comparison of the atmospheric composition changes due to emissions from a future supersonic aircraft fleet

Abstract. Commercial supersonic aircraft may return in the near future, offering reduced travel times while flying higher in the atmosphere than present-day aircraft. Their emissions can change the composition of the atmosphere, particularly in the concentration and spatial distribution of ozone, aerosols, and greenhouse gases, posing risks to both the climate and public health. We present a comprehensive multi-model assessment of the impact of a supersonic fleet on a 2050 atmosphere using four state-of-the-art atmospheric models (EMAC, GEOS-Chem, LMDZ-INCA, MOZART-3). We show that the adoption of a fleet with a NO_x emissions index of 4.6 g(NO₂)/kg(fuel) leads to a model-mean stratospheric H₂O burden of +61.34 Tg for 46.2 Tg of annual H₂O emissions, and an ozone column loss of -0.11 %. With a NO_x emissions index of 13.8 g(NO₂)/kg(fuel) the average ozone column loss increases to -0.31 %. A lower cruise altitude and speed reduces the mean H₂O burden to +9.34 Tg and instead leads to an ozone column increase of +0.02 %. Compared to the most recent multi-model assessment (2007), we find better agreement between the models, especially for the ozone response. Disagreement in H₂O perturbation lifetimes remains, potentially driven by differences in vertical model resolutions. Our results reaffirm that emissions from a supersonic aircraft fleet will lead to global changes in atmospheric composition, which can be reduced by adopting lower cruise altitudes and lowering NO_x emissions.