Air travel has officially made clear blue skies a thing of the past. It seems rare to look up these days without finding a crisscross of contrails outlining the solid blue. Even worse, scientists have found that contrails are contributing significantly to global warming by helping to trap infrared energy in the atmosphere.

But now researchers at the University of Reading think they have found a solution to both problems. They have shown that by adding a negligible distance to the length of flights, contrails can be significantly reduced and their impact on global warming lessened, reports the BBC

Contrails, or vapor trails, are formed when planes fly through very cold, moist air and the exhausts from their engines condense. Some of them can be extremely long in length, stretching for nearly 100 miles. They can sometimes hang in the air for more than 24 hours before fully dissipating. Research has shown that the negative impact of contrails on global warming is even greater than a plane's carbon emissions.

It has long been known that contrails can be limited when planes fly at lower altitudes, but since this increases flying time, it also means burning significantly more fuel. But this leaves open a pressing question: Can the benefits of curbing contrails outweigh the negative impact of burning more fuel? The Reading researchers sought to calculate the answer.

Their study found that by simply re-routing flights in strategic ways, the increase in flight length required to significantly reduce contrails could be minor. For instance, avoiding a major contrail on a flight between New York and London would only add roughly 14 miles to the journey.

"You think that you have to do some really huge distance to avoid these contrails," said lead author Dr. Emma Irvine. "But because of the way the Earth curves, you can actually have quite small extra distances added onto the flight to avoid some really large contrails."

Of course, the precise adjustments required for flights to avoid generating long contrails will depend on the type of aircraft and the specific conditions present on the day of the flight, but these are easy factors to calculate. 

"The key things you need to know are the temperature of the air and how moist it is, these are things we forecast at the moment, so the information is already in there," explained Irvine.

Although there are a number of legislative measures in place around the world to curb carbon emissions from aircraft, there are currently no measures in place aimed at reducing contrails. This, the Reading researchers claim, is something that needs to change. They hope that their study will help to provide some of the hows and whys such measures should be implemented.

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