Contrails

Q: How is a contrail formed when a jet airplane is flying high overhead?

A: Contrails are condensation trails. Like the exhaust from a car's tailpipe during cold conditions, contrails from when the hot air from a jet's exhaust cools and the water in it condenses into a cloud.

Jet contrails create an estimated 20% cloud increase in heavy air traffic corridors with the best weather dynamics, cold moist upper troposphere air. This does not include the South or Southwest. The clouds decrease solar energy, which cools Earth's surface and reduces the Earth's energy losses resulting in warming.

The three days follwing 9/11 climatologists found temperatures fluctuated by 2.16ºF more without air travel than when normal flight patterns prevailed. The greatest change occurred in areas with the greatest contrail coverage, Midwest, Northeast, and, to a lesser extent, Pacific Northwest.

From 1975-1994 North America temperatures rose by almost 0.5ºF per decade aided by increased cirrus clouds due to air traffic. NASA scientists estimate contrails/cirrus clouds will enhance the greenhouse effect by increasing surface and lower atmospheric temperatures by 0.36ºF to 0.54ºF per decade.