In a new study, Voigt et al. directly measured ice particle sizes and numbers in 14 contrails from 9 different aircraft of the present-day commercial fleet, including the largest operating passenger aircraft. They obtained an extensive data set of contrails from which they determined the contrail optical depth, a measure of how much light is attenuated by these man-made clouds.
They use their measurements to estimate that the radiative forcing of line-shaped contrails is about 15.9 milliwatts per square meter, which represents a small positive contribution to the anthropogenic global warming. Yet an expected doubling of aircraft passenger transport within the coming two decades will enhance contrail effects on the atmosphere. The detailed contrail measurements will help modelers working to assess the actual and future impact of aviation on climate.
Geophysical Research Letters, doi:10.1029/2011GL047189, 2011
Title: Extinction and optical depth of contrails
Authors: C. Voigt: Institut fr Physik der Atmosphre, Deutsches Zentrum fr Luft- und Raumfahrt, Oberpfaffenhofen, Germany; and Institut fr Physik der Atmosphre, Johannes-Gutenberg University, Mainz, Germany;
U. Schumann, P. Jessberger, T. Jurkat, and A. Petzold: Institut fr Physik der Atmosphre, Deutsches Zentrum fr Luft- und Raumfahrt, Oberpfaffenhofen, Germany;
J.-F. Gayet: LaMP, University Blaise Pascal, Clermont-Ferrand, France;
M. Krmer: IEK-7, Institute for Energy and Climate Research, Forschungszentrum Jlich, Jlich, Germany;
T. Thornberry and D. W. Fahey; Chemical Sciences Division, Earth System
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American Geophysical Union