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What is a Contrail?

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  • Written By: Mary McMahon
  • Edited By: Bronwyn Harris
  • Last Modified Date: 05 December 2016
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A contrail is a distinctive streak of cloud formed by a jet engine in certain atmospheric conditions. Contrails tend to form very high up in the atmosphere, and they can linger for hours in some cases, sometimes promoting the development of cirrus clouds. In some communities, there is a great deal of controversy over contrails, with some people believing that they are harmful to the environment, while others believe that their effect is probably negligible.

The term “contrail” is simply a contraction of “condensation trail,” and that's exactly what a contrail is: a trail of condensation created by the interaction between a jet and the environment it passes through. One type of contrail is formed by warm, moist air which passes through the engines of a jet and then comes into contact with cold air, causing the water to precipitate out and condense. Contrails can also be caused by the reduction in air pressure associated with the wings of jets, which causes the air to cool down, promoting condensation and the formation of a contrail.

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Classically, contrails appear in the form of large white streaks of cloud in the sky which slowly dissipate. Passing jets can also form what is known as a distrail, where the plane essentially slices through a cloud, leaving a stripe of clear sky behind. Some people say that distrails look sort of as though someone had taken a sponge and wiped a section of the sky clean; many distrails are also associated with contrails, which form inside the distrail.

Because jets are so heavily used around the world, there is some fear that contrails could be having an impact on global climate, and satellite images taken when conditions are ripe for the formation of contrails seem to be supportive of this idea, showing how a network of contrails can develop into cloud cover which would cool the Earth. Some people have also suggested that contrails are laden with chemical pollutants associated with jet aircraft.

While there certainly are cases in which a contrail can join with other contrails and create artificial cirrus clouds, which would obviously impact weather conditions, there are plenty of other cases in which contrails fail to form, or dissipate so quickly that they do not impact the environment. Of far greater concern is the jet fuel used to power these planes, which most certainly does generate pollutants which harm the environment.

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allenJo
Post 4

@NathanG - I’ve seen contrail pictures, and when they crisscross each other they resemble a massive matrix. Perhaps they’re not as big as some clouds but they can linger for hours and form clouds. How long is too long before they impact the environment? I don’t know. But I do believe that they have some effect.

NathanG
Post 3

@David09 - Conspiracy theories like that are clearly silly as you point out. But I think that unwarranted fear about supposedly legitimate concerns is just as ludicrous.

Take the whole idea that a contrail tarp could envelop the Earth and affect climate change. How seriously can we take this argument? First of all, whatever “clouds” may form from the contrails don’t last very long.

Secondly, it would take a lot of jet airplanes flying a very long time to bring about such an expansive cloud cover. These airplanes would have to travel in close proximity to each other to make the cloud cover contiguous as well.

David09
Post 2

Believe it or not, there are some conspiracy theories that surround the use of contrails in jet airplanes. Some people believe that an above top secret program exists whereby the government is seeding our cities with chemicals that affect the general population.

I am not clear as to the agenda behind this alleged conspiracy, whether it’s mind control or whatever. Imagine the great lengths (and expense) the government would have to go through to do this!

Personally, I believe if you want to manipulate the masses, just use the media. It’s far cheaper, and far more effective in my opinion.

anon83922
Post 1

wow. This information is great. can i use some of this for my essay?

Moderator's reply: You certainly can use this, as long as you cite wiseGEEK as your source, and use the author's name, found at the bottom of every wiseGEEK article. This article was written by S.E. Smith.

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