Radiative Effects of contrails and contrail cirrus

Abstract

Contrails and contrail-cirrus contribute a large share to aviation’s greenhouse forcing and strategies to mitigate their adverse effects have been quested after for many years now. The magnitude of radiative forcing due to contrails and contrail-cirrus is yet uncertain and, surprisingly, many years of research and many measurement campaigns could not essentially reduce the uncertainty, often a pretext for non-action. After introducing the principles of radiative effects of contrails I will thus discuss the true meaning of the uncertainty of radiative forcing and will contrast it to natural variability. This shows that reduction of the mentioned uncertainty is unrelated to measures for avoidance of warming contrails. The pertinacious uncertainty can thus not honestly be taken as a reason for not to act against them. A good strategy for avoiding warming contrails needs a fast algorithm for computing the radiative effects of single contrails. A recent example will be presented.