Tuesday, February 2, 2010

Airplane contrails and their effect on temperatures

Good grief - what next?
Contrails from airplanes impact temperatures at Earth's surface. But do they raise or lower them?
Maybe you did some airplane travel over the holidays, and maybe, once your plane reached cruising altitude, you noticed the vapor trails from other jetliners crisscrossing your path. Or possibly one day recently, you simply looked up and noticed many thin, white clouds crisscrossing the sky.
These are contrails, perhaps one of the most directly observable ways human activity can change the weather. They form when, as exhaust spews from jet engines, moisture condenses on particles of soot in the subfreezing air.

They usually appear above 26,000 feet where the air is less than -40 C (also -40 F.) But factors besides altitude also play a role in their formation. Depending on how much moisture is in air, for example, contrails last shorter or longer. Moisture availability also dictates whether they form at all, and how much they grow after formation.
As it turns out, they also impact temperatures at Earth's surface, although by how much and in which direction — up or down — is still being worked out. Read more.

No comments:

Post a Comment