On a clear day you can usually spot a white trail from an airplane in the sky.

They might be fun to look at, but they could also be the reason more solar radiation is reaching our surface, scientists have warned

Researchers have found new data that suggests the layer of crystals left from the contrails is causing a more diffused type of light.

There isn't enough data to support how much of an effect the icy haze left by airplanes has had, but researchers believe it might be altering the climate system.

"This haze is caused by airplanes, and it is gradually whitening blue skies," said Charles Long of NOAA's Earth System Research Laboratory, at a press conference this week at the American Geophysical Union Fall Meeting.

"We might be actually conducting some unintentional geoengineering here."

This theory comes from a previous study of how much sunlight reaches Earth's surface.

From the 1950s to the 1980s, the sun's light seemed to deem then started coming back in full force, proving that energy isn't constant.

When scientists looked for a cause, they tried linking these changes to the sun's variable output, said Martin Wild of the Institute for Atmospheric and Climate Science at ETH Zurich during the press conference.

But they couldn't find any correlations.

"If it's not the sun, it must be the atmosphere' responsible for the change," he said.

Tremendous amounts of aerosols were sent into our atmosphere in the mid-20th century, which ultimately blocked some of the sun's energy.

This was caused by the soaring levels of pollution, but once highly populated countries like the U.S. and Europe decreased their amount of pollution, including the amount of aerosols, and the sun appeared to slightly brighten.

In addition to these findings, Long and his colleagues found that some of the sun's light travels directly on the Earth's surface, but some of it gets scattered while travelling through the atmosphere.

With less pollution, this diffuse light should have decreased, but instead it appeared to be increasing.

"We've got a mystery here," Long said.

"There must be something in the atmosphere scattering the sun's light."

"Small ice particles fit the bill."

He believes air traffic is the reason for all these particles, as exhaust from an airplane engine has aerosols and water vapor.

It's extremely cold high in the atmosphere and these particles serve as nuclei for ice crystals, which form the bright contrails seen flowing behind a plane.

Some of these contrails have been found to contribute to climate change, according to other scientists.

A contrail may disappear, but it leaves behind a thin, icy haze.

Although the sky looks clear, the particles are still there until they eventually fall out of the atmosphere.

While still in the sky, the particles scatter the sun's light in a similar way as in other geoengineering projects.

"It seems quite possible that [Long is] seeing something that's real," said Kevin Trenberth of the National Center for Atmospheric Research. But there's a lot more work that needs to be done to verify the find and make a connection to the climate.

Skies aren't clear all the time, and why they are clear one day and not the next could matter.

"The reason for the clear sky is a factor [Long] needs to explore more," Trenbeth says.

Long has admitted that his study creates far more questions than it does answers.

Currently, he has only gathered serious data from only one spot in Oklahoma and there could be less sky whitening in places that don't get as much air traffic.