Contrail height varies with global warming

Contrails appear more in the winter when the air temperature is colder. The usual height at which jets create contrails is higher in the summer when the air is warmer and lower in the winter. This means, as global warming takes effect, contrail will be less and less likely to appear.

This picture is taken in the middle of a calm winter day. The lake was so flat you could see the contrails in the reflection. Note that the contrails are persistent. The older ones are broader while the newer ones are thin. In the summer, jets make few contrails or contrails that only extend a few miles or less behind the aircraft.

Why Fly?

Does flying contribute to global warming? That depends, contrails made by high altitude jets in the winter months tend to be persistant and grow in width. In the northeast U.S. they can become a high altitude overcast because of the dense air traffic in the area. Does this actually cause a cooling effect in the region? Some experts say the cloud cover holds in the heat and thus contributes to global warming.