For years, the buzz on the Web has been that contrails -- or “chemtrails,” in conspiracy-theorist lingo -- are part of some top-secret government project to control the weather. The National Oceanic and Atmospheric Administration, however, explains that that they’re simply long, wispy streams of condensation, created when hot, humid air in the exhaust from jet aircraft engines mixes with extremely cold (-40 F and below) air at high altitudes that has a lower vapor pressure.

Far from being a malevolent portent of the New World Order, they’re basically water vapor -- just another mundane, harmless curiosity of the modern technological age.

VIDEO: What’s It Like to Ride in a Fighter Jet? Find Out

Or maybe not. As it turns out, contrails aren’t really so benign. Researchers have discovered that, combined with the carbon dioxide spewed by jet exhaust, they actually contribute significantly to global warming.

Contrails can spread and combine to form ice-filled artificial cirrus clouds that trap reflected solar energy and keep it from going back into space. Contrails also block sunlight, too, but the heat-trapping effect is greater.

BLOG: Viral Video Claims to Prove ‘Chemtrails’ Conspiracy

In some busy air corridors, contrails can increase the cloud cover by as much as 20 percent, according to NOAA. A 2011 Nature article reported that at any one moment, contrails contribute more to global warming than all the carbon dioxide that’s been spewed by planes since the Wright Brothers.

Fortunately, a new study by researchers at Great Britain’s University of Reading, published in the journal Environmental Research Letters suggests that tinkering with aircraft flight plans and making them slightly longer at lower altitudes -- where the temperature and vapor pressure are higher -- could significantly reduce the formation of contrails, without burning so much additional fuel that the increased C02 would cancel out the benefit.

via BBC News

Photo: Jets create contrails in the sky in northern France. Credit: Lamiot, via Wikimedia Commons