Are vapor trails from aircraft influencing the climate, and if so, should we worry?
Contrails, the man-made clouds left in the wake of jet aircraft, may actually alter climate, though to what degree remains unclear.
The sheer number of contrails generated on a typical day in busy air corridors can come as a shock. A NASA satellite took this enhanced infrared image of the southeastern U.S. on January 29, 2004.
In skies normally crosshatched with condensation trails, the only contrails seen in this image from September 12, 2001, were left by the plane returning President Bush to Washington from Nebraska and several escort fighters.
In this true-color satellite image shot above northwestern Europe, the contrast between skies with contrails and those without offers a striking sense of the influence these pseudo clouds might have on regional climate.