jetcloud

"Gazing into a clear blue Wisconsin sky, David Travis was amazed by what he did not see: not one fluffy airliner contrail.: Not that day or in the two days that followed the 9/11 terror attacks, when commercial airliners in the United States were grounded.
For Dr. Travis, a climatologist at the University of Wisconsin at Whitewater, that tragedy had a tiny silver lining. A sky without jet contrails became a once-in-a-lifetime opportunity to see if the skinny, man-made clouds really did affect climate, as he had long suspected."