Environment

Simple contrail-curtailing measures may help reduce climate change

Simple contrail-curtailing mea...
According to a new study, moving 1.7 percent of flights 2,000 feet higher or lower could reduce the warming effect of contrails by 59 percent
According to a new study, moving 1.7 percent of flights 2,000 feet higher or lower could reduce the warming effect of contrails by 59 percent
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According to a new study, moving 1.7 percent of flights 2,000 feet higher or lower could reduce the warming effect of contrails by 59 percent
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According to a new study, moving 1.7 percent of flights 2,000 feet higher or lower could reduce the warming effect of contrails by 59 percent

Although they're really just ice crystals, the contrails left by high-flying airliners are nonetheless not entirely innocuous. According to a new study, however, changing the altitude of flights by just 2,000 feet could greatly reduce their effect on the environment.

Condensational trails (aka contrails) form when moisture in cold air condenses on the black carbon particles found in hot aircraft exhaust, forming ice particles. The resulting ice-particle trails appear white and fluffy from the ground, and they typically only last for a few minutes.

Sometimes, however, they spread and mix with neighboring contrails – or with naturally-occurring cirrus clouds – forming what are known as "contrail cirrus" clouds. These may stick around for up to 18 hours.

As they do so, they trap heat emitted by the earth, keeping it from leaving the planet's atmosphere. This creates an imbalance called "radiative forcing," in which the amount of heat-causing radiation reaching the earth from the sun exceeds the amount of heat that escapes back into outer space.

According to previous research, aircraft-caused radiative forcing may have as much of a warming effect on the climate as the cumulative carbon dioxide (CO2) emissions of the entire aviation industry.

With that in mind, scientists from Imperial College London developed a computer model based on data from the airspace over Japan. Among other things, they determined that 80 percent of the radiative forcing in the region was caused by just two percent of the flights.

This was because those particular planes were flying through particularly humid layers of air, that were very conducive to the formation of contrails. By moving most of the offending aircraft 2,000 feet (610 m) higher or lower, though – thus getting them out of those layers – the model indicated that radiative forcing in the area could be reduced by 59 percent.

It was also found that altering the flights in this manner would cause the planes to use slightly under 10 percent more fuel, thus producing more CO2 emissions. Nonetheless, the reduction in radiative forcing was said to far outweigh the slight increase in greenhouse gases – especially if only select flights were moved.

"According to our study, changing the altitude of a small number of flights could significantly reduce the climate effects of aviation contrails," says Dr. Marc Stettler, lead author of a paper on the research. "This new method could very quickly reduce the overall climate impact of the aviation industry."

The paper was recently published in the journal Environmental Science & Technology.

Sources: Imperial College London, American Chemical Society

12 comments
christopher
If it can trap it coming up from below, then by definition it's also going to reflect back whatever's coming down from above too - so the net effect is nothing.
Trylon
And then there are the conspiracy theorists who say there are no such things as contrail cirrus clouds. They'll insist that those are actually "chemtrails."
aksdad
Ummm... clouds (even cirrus clouds) REFLECT the sun during the day, cooling the earth. At night clouds have no sun to reflect so they end up blocking infrared radiation from escaping to space, trapping heat. Clouds in the daytime cool. Clouds at night warm.
Cobrarog
Seems to me, those contrails (clouds) are stopping the suns rays up there, thus shading the lower atmosphere and earth. Who is to say, those contrails are not mitigating global warming to some extent? Why not use that wasted money on heat reflecting materials on roof tops and highways, thus reflecting all that heat back up instead of being absorbed?
alan c
This, along with the eagle slicing drone knock-down idea is the dumbest thing I've seen on New Atlas. Who wants 'planes to use nearly 10% more fuel? Who ever felt warmer when the sun was obscured by clouds? Who has ever seen a sky obscured by contrails? Also, the moisture is in the exhaust , it is a product of combustion.
Brian M
This really only applies to night flights or at least contrails that last into the dark period for the area.
Otherwise "global dimming" which gives a cooling effect is the dominate one as witnessed in the change in temperatures after the 911 attack when aircraft in the US were grounded. This grounding caused a 1 degree change in the difference between night and day temperatures.

Perhaps only night flights could be re-directed to minimise the negative effects of the contrails?l

There is also another factor - if the temperature is made warmer at night - might this reduce heating requirements (and consequently CO2 generation) over built up areas?

Jackie Hodges
Back in the days of 9-11 when they stopped all aircraft from flying, there was a scientist that had predicted that if that were to happen it would cause a warming trend. The idea was the contrails blocked the sun and caused cooling. He measured the temperatures (with the absence of aircraft) around the USA and found that to be true.
Douglas Rogers
You can take the temperature of the night sky (or day sky) with an IR viewer and tell right away the effect of these clouds. The water layer may have a larger effect than the ice.
ljaques
Y'know what would really fix the problem? 11,173,456 quintillion 60mm black plastic balls. Just spread 'em out over the ocean and reduce all that water vapor. Then when Global Cooling sets back in, just collect them and start burning down all the forests again. SIMPLE!
Nobody
(Jackie Hodges) I remember 9/11 and that study. Years ago I even tried to promote the reformulation of jet fuels to provide more opaque contrails for daytime airline routes and a different fuel formulation that minimized contrails at night. Even better would have been additives which could accomplish the same thing with any fuel. I have even suggested that changing the standard airline altitudes could accomplish the same thing depending on the weather. I even got an email from Richard Branson that he wasn't interested. Of course this didn't fit in with the global warming hysteria that wants to demonize all air travel as bad rather than a possible solution.