Formation and radiative forcing of contrail cirrus

Abstract

Aircraft-produced contrail cirrus clouds contribute to anthropogenic climate change. Observational data sets and modelling approaches have become available that clarify formation pathways close to the source aircraft and lead to estimates of the global distribution of their microphysical and optical properties. While contrail cirrus enhance the impact of natural clouds on climate, uncertainties remain regarding their properties and lifecycle. Progress in representing aircraft emissions, contrail cirrus and natural cirrus in global climate models together with tighter constraints on the sensitivity of the climate system will help judge efficiencies of and trade-offs between mitigation options.

The contribution of carbon dioxide emissions from the aviation sector to future climate change

“…Other climate agents directly emitted or affected by aircraft also contribute to the aviation total RF of climate on shorter time scales. This is in particular the case for aircraft NO x emissions affecting tropospheric ozone and the methane lifetime, emissions or formation of particles (black carbon, sulphates, nitrates) and, more importantly, formation of linear contrails and induced cloudiness (Karcher 2018). The aviation CO 2 RF of climate is estimated to represent 36%-51% of this total forcing including short-term climate forcers (Lee et al 2009, Grewe et al 2017, Karcher 2018.…”

“…This is in particular the case for aircraft NO x emissions affecting tropospheric ozone and the methane lifetime, emissions or formation of particles (black carbon, sulphates, nitrates) and, more importantly, formation of linear contrails and induced cloudiness (Karcher 2018). The aviation CO 2 RF of climate is estimated to represent 36%-51% of this total forcing including short-term climate forcers (Lee et al 2009, Grewe et al 2017, Karcher 2018. These additional terms are subject to large uncertainties and will be analysed in forthcoming studies with the OSCAR compact carbon cycle-climate change model in order to account for the different lifetimes of the various climate agents involved or with the more complex LMDz-INCA chemistry-climate model.…”

“…The aviation climate impact is quantified over the 1940-2050 period with an extension to 2100, according to updated aviation emission scenarios and for the two aforementioned RCP (RCP2.6 and RCP6.0) storylines for background of CO 2 concentration and climate future evolution. The contribution of CO 2 is estimated to represent 36%-51% of the total aviation RF of climate including short-term climate forcers (Lee et al 2009, Grewe et al 2017, Karcher 2018. However, due to its long residence time in the atmosphere, aviation CO 2 will have a major contribution on decadal time scales.…”

In Situ Observations of Ice Particle Losses in a Young Persistent Contrail

“…Cirrus clouds evolving from aircraft contrails cause the largest contribution to aviation-induced radiative forcing (Burkhardt & Kärcher, 2011;Kärcher, 2018). However, its quantification is affected by significant uncertainties, which underlines the importance to perform appropriate measurements to better understand processes governing contrail formation and evolution (Heymsfield et al, 2010).…”

“…Fluid-dynamical models (Huebsch & Lewellen, 2006;Unterstrasser, 2016) and measurements Schumann et al, 2013) have shown that aircraft wake dynamics can have marked effects on contrail properties. This includes the possibility of ice particle losses during the descent of wake vortices Geophysical Research Letters 10.1029/2018GL079390 forcing ice particle sublimation due to adiabatic heating even if the ambient air surrounding the contrail is ice-supersaturated (Kärcher, 2018;Paoli & Shariff, 2016). Assessing contrail properties toward the end of the vortex phase is of particular interest, as they affect properties of evolving contrail cirrus over hours (Unterstrasser & Gierens, 2010).…”