Process-oriented analysis of aircraft soot-cirrus interactions constrains the climate impact of aviation

Kärcher, Bernd ORCIDiD
Mahrt, Fabian ORCIDiD
Marcolli, Claudia ORCIDiD

DOI: https://doi.org/10.1038/s43247-021-00175-x
Persistent URL: http://resolver.sub.uni-goettingen.de/purl?gldocs-11858/11344
Kärcher, Bernd; Mahrt, Fabian; Marcolli, Claudia, 2021: Process-oriented analysis of aircraft soot-cirrus interactions constrains the climate impact of aviation. In: Communications Earth & Environment, 2, 1, DOI: https://doi.org/10.1038/s43247-021-00175-x. 
 
Kärcher, Bernd; Institute of Atmospheric Physics, DLR Oberpfaffenhofen, Wessling, Germany
Mahrt, Fabian; Laboratory of Environmental Chemistry, Paul Scherrer Institute, Villigen, Switzerland
Marcolli, Claudia; Institute for Atmospheric and Climate Science, ETH, Zurich, Switzerland

Abstract

Fully accounting for the climate impact of aviation requires a process-level understanding of the impact of aircraft soot particle emissions on the formation of ice clouds. Assessing this impact with the help of global climate models remains elusive and direct observations are lacking. Here we use a high-resolution cirrus column model to investigate how aircraft-emitted soot particles, released after ice crystals sublimate at the end of the lifetime of contrails and contrail cirrus, perturb the formation of cirrus. By allying cloud simulations with a measurement-based description of soot-induced ice formation, we find that only a small fraction (<1%) of the soot particles succeeds in forming cloud ice alongside homogeneous freezing of liquid aerosol droplets. Thus, soot-perturbed and homogeneously-formed cirrus fundamentally do not differ in optical depth. Our results imply that climate model estimates of global radiative forcing from interactions between aircraft soot and large-scale cirrus may be overestimates. The improved scientific understanding reported here provides a process-based underpinning for improved climate model parametrizations and targeted field observations.


Only a small part of aircraft-soot–cirrus interactions succeeds in forming cloud ice, according to simulations with a numerical cirrus cloud model. This suggests that radiative forcing from aircraft soot may have been overestimated.