Model-based estimates of aviation’s climate impacts have found that contrails contribute 36%–81% of aviation’s instantaneous radiative forcing. These estimates depend on the accuracy of meteorological data provided by reanalyses like ECMWF Reanalysis 5th Generation (ERA5) and Modern Era Retrospective analysis for Research and Applications V2 (MERRA-2). Using data from 793 044 radiosondes, we find persistent contrails forming at cruise altitudes in 30° N–60° S are overestimated by factors of 2.0 and 3.5 for ERA5 and MERRA-2, respectively. Seasonal and inter-annual trends are well-reproduced by both models (R2 = 0.79 and 0.74). We also find a contrail lifetime metric is overestimated by 17% in ERA5 and 45% in MERRA-2. Finally, the reanalyses incorrectly identify individual regions that could form persistent contrails 87% and 52% of the time, respectively. These results suggest that contrail models currently overestimate the number and lifetime of persistent contrails. Additional observations are needed for future models in order to provide locally accurate estimates of contrails or to support mitigation strategies.

Aviation emissions have been found to cause5%of global anthropogenic radiative forcing and ∼16 000 premature deaths annually due to impaired air quality. When aiming to reduce these impacts, decision makers often face trade-offs between different emission species or impacts in different times and locations. To inform rational decision-making, this study computes aviation’s marginal climate and air quality impacts per tonne of species emitted and accounts for the altitude, location, and chemical composition of emissions. Climate impacts are calculated using a reduced-order climate model, and air quality-related health impacts are quantified using marginal atmospheric sensitivities to emissions from the adjoint of the global chemistry-transport model GEOS-Chem in combination with concentration response functions and the value of statistical life. The results indicate that 90% of the global impacts per unit of fuel burn are attributable to cruise emissions, and that 64% of all damages are the result of air quality impacts. Furthermore, nitrogen oxides (NOx), carbon dioxide (CO2), and contrails are collectively responsible for 97% of the total impact. Applying our result metrics to an example, we find that a 20%NOx stringency scenario for new aircraft would reduce the net atmospheric impacts by 700mUSD during the first year of operation, even if theNOx emission reductions cause a small increase inCO2 emissions of 2%. In such a way, the damage metrics can be used to rapidly evaluate the atmospheric impacts of market growth as well as emissions trade-offs of aviation-related policies or technology improvements.