posted 08-12-2002 12:15 PM            

They have published a report regarding the increase in temperature related to the grounding of aircraft on and around the 11th of Sept 2001.
David Travis at the University of Wisconsin-Whitewater.

August 08, 2002
Vapour trails' effects confirmed
The difference in daily temperatures caused by the vapour trails from aeroplanes has been confirmed as a result of research conducted during the enforced grounding of passenger aircraft in the US after the 11th September terrorist attacks.

'Clouds formed by the water vapour in the exhaust from jet planes have a small but significant effect on daily temperatures, a new study confirms.'

'The grounding of commercial flights for three days after last September's terrorist attacks in the United States gave David Travis at the University of Wisconsin-Whitewater and colleagues a chance they never thought they'd have: to study the true impact that contrails from jet engines have on our climate.' (Nature)

The difference between temperatures with vapour trails present and vapour trails absent was found to be about 1 degree Celsius. Comparing the three days before and after the enforced grounding, the difference was even greater, at about 1.8 degrees Celsius.