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

• Published in: Atmospheric Chemistry and Physics
• Main Authors: Teoh, R, Schumann, U, Gryspeerdt, E, Shapiro, M, Molloy, J, Koudis, G, Voigt, C, Stettler, MEJ
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2022
• Subjects: Science & Technology; Life Sciences & Biomedicine; Physical Sciences; Environmental Sciences; Meteorology & Atmospheric Sciences; Environmental Sciences & Ecology; PERSISTENT CONTRAILS; ICE SUPERSATURATION; LOWER STRATOSPHERE; CIRRUS; EMISSIONS; VALIDATION; IMPACTS; NUMBER; MODEL; NOX; 0201 Astronomical and Space Sciences; 0401 Atmospheric Sciences; North Atlantic
• Online Access: http://hdl.handle.net/10044/1/99894; https://doi.org/10.5194/acp-22-10919-2022

Around 5 % of anthropogenic radiative forcing (RF) is attributed to aviation CO2 and non-CO2 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 CO2 (+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 %), CO2 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.