Jet contrails major contributor to aviation's effect on climate
Cirrus clouds generated from the contrails of jets may be the cause of more atmospheric warming today than all the CO2 emitted by the aviation industry since the beginning of flight.
Aviation is responsible for about 5% of man-made climate change effects, and that proportion could triple by 2050 according to some projections. Least understood is the role of aircraft exhausts in forming clouds.
If conditions are right, then hot and moist air from the jet engine exhaust meets cold air in the upper atmosphere, and forms fine, but short-lived cirrus clouds which trap the planet's heat. Perhaps a third of the climate effects of aircraft, or 1.5% of all anthropogenic climate change could be due to contrail effects. Smarter jet engines could be a solution.
Writing in the first issue of the journal Nature Climate Change, Ulrike Burkhardt and Bernd Karcher of the Institute for Atmospheric Physics, German Aerospace, in Germany told Earth Times, 'Contrails represent the largest single climate-forcing agent due to aviation. We have produced a global model that quantifies the effect of these clouds on the planet's climate, To do this we had to separate cirrus clouds that formed naturally and those formed in the wake of jets.'
The work is important because if the team's model of how these clouds form are correct, then contrail generated cloud effects must be included when looking for ways of mitigating the impact of our continuing love of flying.
'There may be some easy options to reduce contrail formation, for example changes in flight altitudes, or rerouting aircraft away from areas where the contrails will form, but either of these could have the negative effect of generating additional emissions so more research is required,' added Burkhardt. Future improvements in jet engines or the development of alternative fuels might also help diminish aviation's effect on climate.
UK Met Office climate scientist and expert on the impact of aviation on climate, Olivier Boucher commented, 'The study provides a basis to investigate technological solutions to reduce contrail formation and growth. It might be possible to design smarter jet engines, with reduced emissions of particles and water content in the exhaust, which could reduce contrail formation,' he said, 'Allied with operational changes in the aviation industry and more research to understand contrails, the impact of an ever increasing aviation industry on our climate might be mitigated.'