Aviation contrail climate effects in the North Atlantic from 2016 to 2021

• Published in: Atmospheric Chemistry and Physics
• Main Authors: R. Teoh, U. Schumann, E. Gryspeerdt, M. Shapiro, J. Molloy, G. Koudis, C. Voigt, M. E. J. Stettler
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2022
• Subjects: Physics; QC1-999; Chemistry; QD1-999; North Atlantic
• Online Access: https://doi.org/10.5194/acp-22-10919-2022; https://doaj.org/article/ab128052834348d2bd791d8dcce30884

Around 5 % of anthropogenic radiative forcing (RF) is attributed to aviation CO 2 and non-CO 2 impacts. This paper quantifies aviation emissions and contrail climate forcing in the North Atlantic, one of the world's busiest air traffic corridors, over 5 years. Between 2016 and 2019, growth in CO 2 ( +3.13 % yr −1 ) and nitrogen oxide emissions ( +4.5 % yr −1 ) outpaced increases in flight distance ( +3.05 % yr −1 ). Over the same period, the annual mean contrail cirrus net RF (204–280 mW m −2 ) showed significant inter-annual variability caused by variations in meteorology. Responses to COVID-19 caused significant reductions in flight distance travelled ( −66 % ), CO 2 emissions ( −71 % ) and the contrail net RF ( −66 % ) compared with the prior 1-year period. Around 12 % of all flights in this region cause 80 % of the annual contrail energy forcing, and the factors associated with strongly warming/cooling contrails include seasonal changes in meteorology and radiation, time of day, background cloud fields, and engine-specific non-volatile particulate matter (nvPM) emissions. Strongly warming contrails in this region are generally formed in wintertime, close to the tropopause, between 15:00 and 04:00 UTC, and above low-level clouds. The most strongly cooling contrails occur in the spring, in the upper troposphere, between 06:00 and 15:00 UTC, and without lower-level clouds. Uncertainty in the contrail cirrus net RF (216–238 mW m −2 ) arising from meteorology in 2019 is smaller than the inter-annual variability. The contrail RF estimates are most sensitive to the humidity fields, followed by nvPM emissions and aircraft mass assumptions. This longitudinal evaluation of aviation contrail impacts contributes a quantified understanding of inter-annual variability and informs strategies for contrail mitigation.