A standard infrared satellite image shows cloud coverage (left). a double-wavelength infrared image reveals the underlying contrails (right).

In 2002, using data collected during the three-day grounding of all aircraft in the U.S. after 9/11, scientists discovered that contrails–the wispy white streaks that trail jets–were narrowing the natural day-night temperature cycle in well-trafficked areas. Now a NASA study indicates that warmed-up nights are outpacing cooled-down days. In the U.S., for example, detailed atmospheric modeling suggests that contrails could account for a climate-warming trend–just under 0.3