Contrails make the planet warmer:
https://e360.yale.edu/features/how-airplane-contrails-are-helping-make-the-planet-warmer
Didn't they find a 2C increase ~9/11 when there were virtually no planes in the sky over America?
Terry
As with clouds- it's complicated, rather, it's complex. The article posits that the clouds (contrails) produced by planes act as a blanket at night, resulting in a net warming effect. Tech changes to reduce CO2 emissions could result in thicker contrails, thus more insulation. Now, if planes were only allowed to fly in daytime...
"While CO2 accumulates in the atmosphere and has a long-lasting effect, contrails last a matter of hours at most, and their warming impact is temporary."
Regarding the 9/11 effect: "And after 9/11, when all commercial flights in the U.S. were grounded for three days, the diurnal temperature difference increased by up to 1.8 degrees C. The increase was strongest where air traffic was normally densest, said the study’s author, David Travis of the University of Wisconsin."
In other words, contrails do have a cooling effect during the day, and a warming effect at night. Which seems legit. The article does discount electrification of air travel, or the possibility we will decide to fly less, or that carbon taxes will drive behaviour away from flying.