Do contrails cool the atmosphere?
I read once that airplane contrails may cool the climate and that this effect was observed following the grounding of planes after the September 11 attacks. Could this effect be the basis for climate change mitigation?
Dave - I think there have been some studies done on this - there's one 3 or 4 years back - and I think they can either increase the temperature or decrease it, depending on where they are. If you're somewhere very, very sunny then they can actually reflect more heat out, than they reflect back in. I think on average, they reckon, especially in places like the UK, they tend to actually heat up the Earth more because they are acting as an insulating blanket, as cloud does, and so they actually, if anything, increase the temperature.