Contrails: Controversial Clouds Cuing Climate Change?

Contrails, artificial clouds of condensed water vapor created by aircraft, can be beautiful but these sleek sky streaks may not be as harmless as they appear.

Jet Steam In The Jet Stream

(image via: U.S. Air Force)

The United States Air Force C-141B Starlifter above certainly looks spectacular as it roars through Antarctica’s dry and cloudless skies but its appearance leaves a few worrisome questions in its wake… mainly, what’s the deal with the quartet of instant artificial clouds the jet’s leaving in its wake?

(images via:

They’re contrails: “condensation trails”, made up of condensed water vapor that becomes visible once it’s exhausted from an aircraft’s hot engine and rapidly cools in the upper atmosphere’s chilly air. Not only jets create contrails; anyone whose watched a wave of World War II bombers in a war movie will recall the multiple white contrails streaming behind the fleet of high-flying Flying Fortresses and the curlicue clouds marking the fighter aircraft tasked with shooting them down.

(image via: Contrail Science)

Contrails from jet aircraft, however, are thicker, longer, and more persistent because while piston-engined aircraft expel water vapor in their exhaust, jet engines are all about sucking in air, burning it with fuel, and expelling it forcefully to create thrust. That’s a lot of air moving at great rates of speed and with enormous volume per engine!

(images via: Wikimedia and NASA)

While ambient atmospheric conditions such as wind speed, wind shear, relative humidity and regional air pressure can and do affect the formation of contrails, the contrails themselves can (and do!) affect ambient atmospheric conditions relating to air temperatures and the amount of sunlight that reaches the ground. Can a few skinny contrails really affect the climate locally, regionally and even globally? No… but a LOT of contrails certainly can, and there certainly are a lot of contrails in the air!


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