"Contrails trap heat in the atmosphere by reflecting infrared radiation emitted from the Earth's surface."
I believe just the opposite of a study commisioned after 9-11.
The minimal airtraffic immediately after 9-11 proved conclusively how contrails coallesce into high Cirrus. The beliefs expressed by the researchers was that while the clouds may trap some heat in, they also serve as an umbrella reflecting much IR radiation out.
More study required for sure.
PT