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Climate Effects and Aircraft Contrail Mitigation | Events

Contrails form behind an aircraft and can persist, spread, and evolve into contrail cirrus when the atmosphere is supersaturated with ice. The scientific consensus is that contrails induce a net warming effect and that their global annual average net radiative forcing (RF) could be greater than the RF of cumulative aviation CO2emissions since its creation. Here, we simulate contrails in the North Atlantic with historical trajectory and five-year meteorological data to identify the set of factors associated with flights forming strongly warming/cooling contrails. There is significant interannual variability in the annual average net RF of trailing cirrus clouds in this region (204 – 280 mW m-2), and about 12% of all flights in this region are responsible for 80% of the annual contrail energy forcing. Flights with strongly heated contrails are more frequent: (i) in winter; (ii) between 3:00 p.m. and 4:00 a.m. UTC; (iii) when sailing near the tropopause and above low level clouds; and (iv) aircraft types with high non-volatile particulate matter (nvPM) emissions per unit distance flown. Based on these results, we discuss the pros and cons of potential mitigation solutions to minimize drag climate forcing, such as the use of cleaner-burning engines and sustainable aviation fuels, which reduce nvPM emissions from aircraft; and flight diversion strategies that re-route flights around regions where strongly warming contrails are expected to form.

Roger Teoh is from the Center for Transport Studies, Department of Civil and Environmental Engineering, Imperial College London.