The effects of aircraft on climate and pollution. Part II: 20-year impacts of exhaust from all commercial aircraft worldwide treated individually at the subgrid scale

This study examines the 20-year impacts of emissions from all commercial aircraft flights worldwide on climate, cloudiness, and atmospheric composition. Aircraft emissions from each individual flight worldwide were modeled to evolve from the subgrid to grid scale with the global model described and evaluated in Part I of this study. Simulations with and without aircraft emissions were run for 20 years. Aircraft emissions were found to be responsible for similar to 6% of Arctic surface global warming to date, similar to 1.3% of total surface global warming, and similar to 4% of global upper tropospheric warming. Arctic warming due to aircraft slightly decreased Arctic sea ice area. Longer simulations should result in more warming due to the further increase in CO2. Aircraft increased atmospheric stability below cruise altitude and decreased it above cruise altitude. The increase in stability decreased cumulus convection in favor of increased stratiform cloudiness. Aircraft increased total cloud fraction on average. Aircraft increased surface and upper tropospheric ozone by similar to 0.4% and similar to 2.5%, respectively and surface and upper-tropospheric peroxyacetyl nitrate (PAN) by similar to 0.1% and similar to 5%, respectively. Aircraft emissions increased tropospheric OH, decreasing column CO and CH4 by similar to 1.7% and similar to 0.9%, respectively. Aircraft emissions increased human mortality worldwide by similar to 620 (-240 to 4770) deaths per year, with half due to ozone and the rest to particulate matter less than 2.5 micrometers in diameter (PM2.5).