September 06, 2019

Contrails And Climate Change

2 minutes

The white wispy trails of condensation produced by the exhaust from

aircraft engines have been the subject of a popular conspiracy theory for quite

a while. The story goes that the

long-lasting condensation trails are actually “chemtrails” composed of chemical

or biological agents left in the sky by aircraft and are intentionally sprayed

for a variety of nefarious purposes undisclosed to the general public. This story, of course, is nonsense.

But while contrails are not deliberate efforts to modify weather,

control population, manipulate psychology, or any of the other bizarre things

attributed to them, it turns out that they are having unfortunate effects on

the climate.

It turns out that contrails are creating an often-invisible thermal blanket of cloud across the planet that has a significant effect on atmospheric temperatures. Contrails are essentially human-made clouds that form above 25,000 feet where the air is moist and colder than -40 degrees Celsius. At times, contrails stick around in the sky, either as tight, white lines like chalk marks, or by spreading to create thin layers of ice clouds. At any one time, contrail-created clouds cover more than half a percent of global skies.

Research has shown that when contrails are around, nighttime

temperatures can go up appreciably.

After 9/11, when all U.S. flights were grounded for three days, the

difference between daytime and nighttime temperatures actually increased by

about 3 degrees Fahrenheit because nights were cooler.

The effects of aviation on climate, both from the CO2 emissions from aircraft engines and from these contrail effects are becoming an increasingly important issue. To complicate matters further, as aircraft engines become more efficient, they will create more, whiter, and longer-lasting contrails.

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Web Links

How Airplane Contrails Are Helping Make the Planet Warmer

Photo, posted May 15, 2012, courtesy of Mike Lewinski via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

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