NASA scientists have found that cirrus clouds, formed by
contrails from aircraft engine exhaust, are capable of
increasing average surface temperatures enough to account for a
warming trend in the United States that occurred between 1975
and 1994. According to Patrick Minnis, a senior research
scientist at NASA’s Langley Research Center in Hampton, Va.,
there has been a one percent per decade increase in cirrus cloud
cover over the United States, likely due to air traffic. Cirrus
clouds exert a warming influence on the surface by allowing most
of the Sun’s rays to pass through but then trapping some of the
resulting heat emitted by the surface and lower atmosphere.
Using a general circulation model, Minnis estimates that cirrus
clouds from contrails increased the temperatures of the lower
atmosphere by anywhere from 0.36 to 0.54°F per decade. Minnis’s
results show good agreement with weather service data, which
reveal that the temperature of the surface and lower atmosphere
rose by almost 0.5°F per decade bet