Re-routing flights could reduce climate impact, research suggests

Jun 18, 2014
An airliner lands at sunset

Aircraft can become more environmentally friendly by choosing flight paths that reduce the formation of their distinctive condensation trails, new research suggests.

In a study published today, 19 June 2014, in IOP Publishing's journal Environmental Research Letters, researchers from the University of Reading have shown that aircraft contribute less to by avoiding the places where the thinly shaped clouds, called contrails, are produced – even if that means flying further and emitting more carbon dioxide.

Contrails only form in regions of the sky where the air is very cold and moist, which is often in the ascending air around high pressure systems. They can sometimes stay in the air for many hours, eventually spreading out to resemble natural, wispy clouds.

The findings suggest that policymakers need to consider more than carbon emissions in discussions about how to make aviation less environmentally damaging. Recent research has shown that the amount of global warming caused by contrails could be as large, or even larger, that the contribution from aviation CO2 emissions.

The work was carried out by Dr Emma Irvine, Professor Keith Shine, and Professor Sir Brian Hoskins, at the Department of Meteorology at the University of Reading.

Dr Irvine said: "If we can predict the regions where contrails will form, it may be possible to mitigate their effect by routing aircraft to avoid them.

"Our work shows that for a rounded assessment of the environmental impact of aviation, more needs to be considered than just the of aircraft."

Just like natural clouds, contrails reflect some of the Sun's incoming energy, resulting in a cooling effect, but also trap some of the infrared energy that radiates from Earth into space, therefore having a warming effect. Detailed calculations indicate that generally the warming effect wins over the cooling effect.

The researchers estimate that smaller aircraft can fly much further to avoid forming contrails than larger aircraft. For example, for a small aircraft that is predicted to form a contrail 20 miles long, if an alternative route adds less than 200 miles onto the route (i.e. 10 times the length of contrail that would have been produced) then the alternative route would have a smaller climate impact.

For larger aircraft, which emit more CO2 than smaller for each mile flown, the alternative route could still be preferable, but only if it added less than 60 miles (i.e. 3 times the contrail length) onto the route.

Dr Irvine added: "Comparing the relative of CO2 and contrails is not trivial. One complicating factor is their vastly differing lifetimes. Contrails may last for several hours, whilst CO2 can last for decades. In terms of mitigating these impacts, air traffic control agencies would need to consider whether such flight-by-flight re-routing is feasible and safe, and weather forecasters would need to establish if they can reliably predict when and where contrails are likely to form.

"The mitigation targets currently adopted by governments all around the world do not yet address the important non-CO2 climate impacts of aviation, such as contrails, which may cause a climate impact as large, or even larger, than the climate impact of aviation CO2 emissions.

"We believe it is important for scientists to assess the overall impact of aviation and the robustness of any proposed mitigation measures in order to inform policy decisions. Our work is one step along this road."

Explore further: NASA to study the effects on emissions and contrail formation of burning alternative jet fuels

More information: E A Irvine, B J Hoskins and K P Shine (2014) 'A simple framework for assessing the trade-off between the climate impact of aviation carbon dioxide emissions and contrails for a single flight' Environ. Res. Lett. 9 064021. iopscience.iop.org/1748-9326/9/6/064021/article

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dav_daddy
1.9 / 5 (11) Jun 19, 2014
Didn't average temp jump like 3 degrees in US after 9/11 with all the planes grounded?

With crap like this its no wonder so many people doubt climate change. We all know it gets much hotter out when it's cloudy.

Imagine if we could just get rid of all those pesky clouds how much cooler the planet would be.
barakn
4.2 / 5 (10) Jun 19, 2014
No. The daily temperature range increased by about 1 degree C above the 1971-2000 average. We're talking about the range, i.e. the nightly low and the daily high, and this says absolutely nothing about the average temperature. People doubt climate change because idiots like you invent false factoids out of thin air.
sirchick
4.4 / 5 (7) Jun 19, 2014
Didn't average temp jump like 3 degrees in US after 9/11 with all the planes grounded?


Average is such a useless word.. over what time span are you referring to and where did you read such info?

Whilst air quality probably improved (with exception of around the incident in question) such an event would have almost no impact on climate temperature, now it might affect the typical temperate for that month....

The climate as a whole would've been affected in an immeasurably small way...perhaps not at all infact.....

You have basically confused climate and seasonal weather, climate is a long time span.

Only a serious volcanic eruption could affect climate in a sudden manor really.
lynvingen
1.8 / 5 (5) Jun 19, 2014
Agree with dav_daddy: What I have heard too in stories like this is that the contrails reduces the heat from the sun and the greenhouse effect because they reflect the infrared radiation out into space. I have also read, I believe on this website that after 9.11, when all the planes were grounded that the average temperature increased 3-4 degrees in the US.
However, this could have been daytime temps, because at night the same clouds would trap heat in the atmosphere, maybe thats what they are talking about? Critical details like this always get lost in the media.

At this point, who really knows?
Vietvet
3.7 / 5 (6) Jun 19, 2014
runrig
3.9 / 5 (7) Jun 19, 2014
Agree with dav_daddy: What I have heard too in stories like this is that the contrails reduces the heat from the sun and the greenhouse effect because they reflect the infrared radiation out into space. I have also read, I believe on this website that after 9.11, when all the planes were grounded that the average temperature increased 3-4 degrees in the US.
However, this could have been daytime temps, because at night the same clouds would trap heat in the atmosphere, maybe thats what they are talking about? Critical details like this always get lost in the media.

At this point, who really knows?

Contrails are more opaque to IR than they are SW - just look at side-by-side pics in the two radiances to appreciate, however......

During the day they will cool, but during the night they will warm (the Earth's surface below).
You have to work out which is dominant.
And as someone said you will probably just alter the max and the min and end up with a barely changed average.
runrig
4 / 5 (4) Jun 19, 2014
I see mr biased observer knows meteorology better than me.
About par for the course in the denialosphere.
antigoracle
1.7 / 5 (6) Jun 19, 2014
even if that means flying further and emitting more carbon dioxide.

Another "genius" solution from the AGW Cult, as if bio-fuel from corn wasn't stupid enough.
PPihkala
1 / 5 (2) Jun 21, 2014
I think I saa study that suggested ending night time flights because they warm by causing contrails.
julianpenrod
1 / 5 (1) Jun 22, 2014
Basically, a repudiation of many things claimed about "contrails" and a validation of things I derived about chemtrails that are generally derided.
How do you find a place where "contrails" won't form? They form by the condensing of water, from jet engine operation, in the supercold air just below the stratosphere. Where are you going to find regions 7 miles up that aren't immensely cold?
And, now, clouds are being accused of holding down infrared heat. What of all the plans to stop global warming by reflecting light away with artificial clouds. And how do the ice crystals of "contrails" hold heat?
I have said that global warming began with the first jets spraying chemtrail chemicals. In pinning it on contrails, they're admitting that global warming started around 1950. I also have been pointing out that chemtrail chemicals are making the air incapable of supporting aircraft and jets "divert" around such patches, and they are admitting that will be policy.

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