Contrails are the trails of condensed water vapor that follow an airplane at a high enough and cold enough altitude. They became a visible presence in World War II and were part of newsreels of allied bombers hitting Germany and dog fights over the English countryside. There was more than just an aesthetic side to the new, high clouds in the sky, though. Post-9/11 During the attacks on September 11, 2001, FAA controllers, “Did the only thing they could think of to try to control the situation: ordering every aircraft in U.S. airspace, about 4,000 of them, to land somewhere, anywhere, immediately.” “Canadian officials followed. Airports in Atlantic Canada quickly filled with thousands of bewildered people who had been flying west across the Atlantic from Europe, but found themselves stranded in Goose Bay, Labrador or Stephenville, [Newfoundland].” Following this mass grounding, an observable cooling took place. Andrew Carleton, a geographer at Pennsylvania State University recalled his observations at the time. “I remember walking …
