![320px-Qantas_Boeing_747-400_VH-OJU_over_Starbeyevo_Kustov[1]](https://wattsupwiththat.files.wordpress.com/2014/06/320px-qantas_boeing_747-400_vh-oju_over_starbeyevo_kustov1.jpg?quality=83)
From the Institute of Physics
Re-routing flights could reduce climate impact, research suggests
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 global warming 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 carbon emissions 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 aircraft 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 climate impacts 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.”
Fast Facts
- Aviation CO2 emissions accounted for 6% of UK total greenhouse gas emissions in 2011.
- Global CO2 emissions from aviation were estimated at 630 million tonnes of CO2 for 2005. This is 2.1% of the global emissions of CO2 in that year.
- Previous research by scientists at the University of Reading has shown that, on average, 7% of the total distance flown by aircraft is in cold, moist air where long-lasting contrails can form (2.4 billion km out of a global total of 33 billion km flown in 2005).
- Aircraft engines emit a number of other gases and particles that can alter climate (such as oxides of nitrogen and sulphur gases) and their effects might also depend on the route taken.
Discover more from Watts Up With That?
Subscribe to get the latest posts sent to your email.
I suspect those contrails act much like John Christy’s water vapor. Christy did a study years ago showing much of the San Joaquin Valley’s temperature change was due to irrigation- transpiration in plants led to cooler days, extra water vapor led to less cold nights, with net overall warming.
Since contrails only form in a narrow altitude band it would seem easier to change altitude than to change route. This was regularly done by reconnaissance aircraft during WW2 to avoid detection.
It’s called money [in] search of science instead of the usual science in search of money. The typical approach is some government agency announces a grant program for a targeted field. “Scientists” then sit down and try to figure out how to get a piece of the pie. First, you have to guess what topics the reviewers will prioritize, which isn’t difficult. Then, it’s just a matter of drafting the grant proposal with wording that clearly indicates the results of the research in advance.
” I believe he concluded that contrails raise nighttime temperatures, and lower daytime temperatures.”
Could be. Luckily for us, not that many planes fly at night compared to the day. Ergo, plane travel should be a net negative temperature wise with regards to contrails.
Tom O says:
June 19, 2014 at 6:25 am
….
I have rarely seen a “contrail” last for any length of time and certainly not spread out and resemble natural, wispy clouds. ….
********
On the contrary, I’ve often seen them last hours and the descriptions of them spreading out is quite accurate. Of course, it may be a function of location, our Gulf Coast is pretty moist.
I have to roll my eyes at those that say the grounding of aircraft during 911 increased, or decreased temperatures.
Please. You can only know this, if you know exactly what the daily temperature would have been those days without the grounding of aircraft. No weather forecast is that accurate.
The CAGW crowd has gone completely barking mad. And still, the funding gravy train keeps on rolling. How can the fools who did this study not see how stupid it is?
Wait……..so now scientists have a complete understanding of clouds,how they form and their contribution to global warming ?
That’s amazing!
Considering filght time…Think about this:
It was in the news recently that the Whitehouse installed a 6.3 kilowatt PV system. This was used to show resolve in the fight against global warming. The daily energy production of such a system in Washington DC is about 27 kilowatt-hours.
That amount of energy is consumed by Air Force One in 0.7 seconds (about 500 feet of travel). A years worth of energy from the PV system will be consumed in a little over 4 minutes. One round trip between Washington DC and Hawaii would consume over 200 years of energy from the Whitehouse PV system.
For details see…
http://climatesanity.wordpress.com/2014/05/28/news-white-house-installs-6-3-kw-solar-pv-system/
An important part of science is observation.
The Oxford English Dictionary defines the scientific method as “a method or procedure that has characterized natural science since the 17th century, consisting in systematic observation…
We can argue about what causes contrails or chemtrails and what impact they are having but to say it’s not happening is rather foolish I think. Try looking up once.
So we have something else that just might be more important to the climate than CO2.
Who’d-a-thunk-it could be?
cn
elmer says:
June 19, 2014 at 9:02 am
An important part of science is observation.
“We can argue about what causes contrails or chemtrails and what impact they are having but to say it’s not happening is rather foolish I think. Try looking up once.”
I don’t recall anyone saying vapour trails aren’t happening? I do recall people saying that the clear blue skies during the Icelandic eruption of Eyjafjallajökull when flights were stopped would be a rare and unusual sight. Well those skies were not rare as I’ve observed clear blue skies before and after that eruption when planes were flying.
The video is not that interesting and to complete the observation of the sky it would be better to show all the other cloud types that traverse the sky 24 hours a day 365 days a year; Such as the high cirrus that precedes a front, or cloud streets, or wave clouds etc. I love watching clouds.
Here is a science question:
The alleged GW aspect of contrails is in the absorption, emission, and reflecting of IR energy from the H2O dispersed in upper troposphere – lower stratosphere.
Does it matter the PHASE the H2O molecule?
Certainly in the case of albedo, the contrail must condense into water vapor, and quickly into ice crystals at that altitude. Uncondensed water vapor would seem to change albedo very little.
But for the warming aspect, does uncondensed water vapor have the same, more, less “heat trapping” power as cirrus clouds or contrails for the same amount of water vapor?
Implication: the amount of water added to the upper atmosphere by jet planes is proportional to fuel use. Planes that don’t create contrails are still disbursing water vapor in its combustion products. If it doesn’t immediately create contrails, is the “danger” over? or will the water form greater cirrus cloud accumulation hours later?
One alternative to flying in the high-altitude zone around high pressure systems is flying in the lower-altitude zone around high pressure systems. This increases air resistance (drag) and decreases lift, requiring more thrust, so fuel consumption rates increase dramatically. More CO2 goes into the air.
The other alternative is not flying at all. 🙁
Thirteen years ago, all domestic flights were grounded after the horrible 9/11 terrorist attacks on New York and DC. With no commercial flights leaving contrails over the USA and Canada, what was the effect?
If this article is to be believed, if contrails cause a net warming effect, then we should have some measurable anomaly for the days when the flights were grounded. Does the data support the conclusion that contrails cause warming?
Another addition to the list of Global Warming “Facta”. ;-D
more soylent green! says:
June 19, 2014 at 10:25 am
Somewhere I have that study from 9/11 referenced, someone will probably post it before I find it.
more soylent green! says:
June 19, 2014 at 10:25 am
Found it but the results of the study were widely disputed …
http://www.nature.com/news/2002/020808/full/news020805-7.html
http://www.celsias.com/article/9-11-contrail-climate-effects-questioned/
And in a couple more years someone will say it was all caused by alignment of the planets. 🙁
Contrails are condensation and are dependent upon the ambient air temperature and the water vapor content. Our piston engine bombers (and fighters) in WW2 usually left contrails in the skies over northern Europe. Sometimes the bomber formation leader would alter the altitude to an altitude where contrails didn’t form and make the formation harder for enemy fighters to find.
As this picture of B-17’s spiral prop-tip-generated contrails shows, contrails can be created by a sudden low-pressure field in near saturated clear air.
http://commons.wikimedia.org/wiki/File:B-17_Flying_Fortress.jpg
Rather than being at night, as the caption says, It is a fast shutter speed taken up at high altitude from a plane lower in the formation of a daylight mission against a dark blue high altitude sky.
What is interesting here is that the contrails do not come from the engines, at least not within range of the picture. Yet the contrail is generated instantaneously from the propeller tip, yet persist for seconds to minutes.
On the other hand, transonic aircraft can show an instantaneous condensation cloud that travels with the aircraft, but does not last.http://www.thelivingmoon.com/45jack_files/03files/Transonic_Clouds_Page_02.html
http://www.nature.com/news/2002/020808/full/news020805-7.html
“They found that the difference between daily high and nightly low temperatures in the absence of contrails was more than 1 oC greater than in the presence of contrails. Comparing the three-day grounding period with the three days immediately before and after, the impact was even larger – about 1.8 oC.
“It’s obviously a significant effect,” says Andrew Carleton, an atmospheric scientist at Pennsylvania State University in University Park and a member of Travis’s team.
The researchers suggest that in regions with crowded skies, contrails work just like artificial cirrus clouds, preventing days from getting too hot by reflecting the Sun’s rays, and keeping nights warmer by trapping the Earth’s heat. ”
Why is moderating temperatures between day and night a BAD think, a why do the article’s authors propose taking measures to counteract this seemingly benign effect of contrails?
There’s too much government funding wasted on “the science of global warming” .
Re: Does phase of the H2O molecule matter to the absorption spectra?
http://www1.lsbu.ac.uk/water/vibrat.html#comp
Yes it does. Greatly. Liquid water and Ice have greater and broader absorption than does vapor, but at longer wave lengths in the middle infrared:
Liquid (25deg C) – 3600 to 3200 cm-1,
ice (190 K = -83 C) – 3500 to 3000 cm-1.
They went looking for a “warming effect”, and, wonder of wonders, eureka, they found it!
The joys of climate scientology.
Quote:
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.
_________________________________
What an absurd idea.
Firstly, more aircraft fly in the day than at night, especially in the all-important summer months. (Each hemisphere receives its climate-warming during the summer, and more aircraft fly in the summer than the winter). Any pilot will know that the ATC frequencies are pretty dead at 3am, demonstrating that very few aircraft are flying. The net effect of this bias towards summer daytime flying (because of holiday-maker passengers), has to be daytime cooling and not nighttime warming.
Secondly, the contrail layer can be quite thick sometimes. This would mean a much lower flight level for the cruise than normal, and greatly increased fuel burns. So much so, that many aircraft would have to offload passengers to make their normal destination. This would kill aviation. But there again, I daresay that that is the whole point of this absurd proposal.
R
@Alan McIntire says:
So, clouds moderate the temperature and moderate the temperature differences between daytime and nighttime? Yee gods man, surely this warrants immediate action!
No seriously, I don’t see the problem either.