Aircraft exhaust causes cirrus cloud formation

[verdigris]

In an edition of the New Scientist it says:
"The streams of water vapour and ice particles that form behind an aircraft, called contrails, are known to create cirrus clouds. These clouds can trap heat radiating from the Earth's surface and thus add to global warming"

How big an addition to global warming?

 

[sneez]

Cirrus clouds may trap heat and they may also reflect sun light therefore cool the atm. There is now ongoing research on the EXACT composition of cirrus clouds in which there is possbility of cirrus clounds to be in some instances made of supercooled water droplets. That would have implication on its own.

So strictly speaking, we do not know. But there are papers which estimated it, with some reasonable assumptions.

There has to be more data on cirrus clouds climatology, their thickness, can they be treated as black bodies, temperature dependence on particle radius, and above all, it all has to be incorporated into global circulation model (which has its own issues), etc...

There is lots of work to be done here.

 

[Andre]

Some of the work done:

http://www.atmos-chem-phys.net/5/2155/2005/acp-5-2155-2005.pdf
http://www.livescience.com/environment/050126_contrail_climate.html

The satellite temps of the lower troposphere show a increasing deviation between the hemispheres, the south is not warming, the north is taking everything. The bulk of the airline traffic is on the northern hemisphere. Worth investigating.