A Global Aviation Emission Inventory of Contrail-Processed nvPM Particles

The largest uncertainties in current estimates of the aviation contribution to anthropogenic climate forcing are associated with aerosol-cloud interactions, particularly the role of soot, i.e., non-volatile particulate matter (nvPM), as the ice-nucleating particle (INP). Contrail processing, where ice crystals form on aircraft-emitted nvPM particles and subsequently release these particles back into the atmosphere after sublimation, influences their ice nucleation efficiency. However, to date, no aircraft emission inventory includes contrail-processed aerosol particles. In this study, we present the first comprehensive global aircraft emission inventory of contrail-processed nvPM particles, based on robust contrail simulations from the CoCiP (Contrail Cirrus Prediction) model and GAIA, a high-resolution real-life aircraft emissions inventory for the years 2019–2021. Our results show that aviation emitted a total of 2.83 × 10²⁶ nvPM particles in 2019, with reductions of 48% and 41% in 2020 and 2021, respectively, due to COVID-19. During this period, the proportion of contrail-processed particles remained relatively consistent, with a slight reduction from 15% annually in 2019 to around 13% in 2020 and 2021. Approximately 75% of contrail-processed nvPM particles were processed by short-lived contrails. Spatially, the highest absolute concentrations of contrail-processed particles occurred over Europe and North America, while regions like the Arctic and North Atlantic exhibited the largest relative percentages due to favourable contrail formation conditions. Vertically, contrail-processed particles were primarily concentrated between 7 and 17 km, becoming increasingly dominant with altitude. Future work will focus on using this inventory in global climate models to estimate the impact of contrail processing on aviation aerosol-cloud interactions, contributing to reducing the uncertainties in aviation’s climate impact assessments.