[palmer]

The vapor trails you see in the sky are water vapor. They actually cause global warming, net. They reflect some sunlight back to space during the day, but reflect heat back to earth 24x7.

In general high clouds (with cold tops) cause global warming and low cloud with low warm tops cause global cooling, although there are other factors like seaonality (e.g. when there's no sun in high latitude winter, then clouds almost always cause warming). Another factor is what is beneath the clouds. Snow is a great reflector of solar energy, and clouds are usually darker than snow as seen from space.

[Enlightened1]

Vapor trails from what? I know the contrails from jets quickly dissipate.

They do not sit in the stratosphere for hours and slowly spread out from horizon to horizon. That is Geoengineering for you.