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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.
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After the 9-11 attacks in New York, the US aircraft fleet was grounded. This produced 1 oc warmer days and cooler nights.
http://www.bbc.co.uk/sn/tvradio/programmes/horizon/dimming_qa.shtml
So aircraft contrails cause about 1 oc of cooling during the day. But since the N Hemisphere receives its climatic warming in the summer daytime (when aircraft make the surface cooler), the net effect must be that aircraft cool the atmosphere.
Readers might also like this transcript, from an old BBC Horizon program about Global Dimming and pan evaporation rates. I have not time to read it all now, but the huge decrease in insolation and evaporation recorded here does not exactly square with the claim that the world is warming.
http://www.bbc.co.uk/sn/tvradio/programmes/horizon/dimming_trans.shtml
And I do like this quote from this program:
DR BEATE LIEPERT: My friends’ reaction to Gerry’s and to my work at the same time was, “oh my God this is really extreme, you are, umm, contradicting global warming. Err do you know how many billions of dollars was spent on global warming research? And you and this old guy are, errr, contradicting us !!
Ralph
19 June: Matt McGrath: Longer flights ‘could curb impact of vapour trails’
Avoiding a major contrail on a flight to New York from London would only add 22km to the journey, experts say…
“You think that you have to do some really huge distance to avoid these contrails,” lead author Dr Emma Irvine told BBC News.
“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.”…
So if a flight from the UK to Spain is predicted to create a 20km long contrail, as long as the plane flew less than 200km extra to avoid it, the overall warming impact would be reduced…
“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,” said Dr Irvine.
“Whether the forecasts are accurate enough to do this is another question.”…
http://www.bbc.com/news/science-environment-27907399
alarming that developingh countries’ economies are growing (& flying)! Guardian alarmed!
11 June: Guardian: Elisabeth Braw: Aviation industry is carbon criminal, while supermarkets slash emissions
PHOTO CAPTION: The aviation industry has failed to cut CO2 despite tough national targets. The blue section illustrates international aviation, and red domestic aviation.
That’s the dilemma: precisely because developing countries’ economies are growing, setting CO2 reduction targets becomes harder. And developing countries’ CO2 emissions are increasing at an alarming rate…
http://www.theguardian.com/big-energy-debate/aviation-carbon-supermarkets-emissions
Pat.
The aviation industry has failed to cut CO2 despite tough national targets.
_____________________________
Both true and nonsense simultaneously. New aircraft are some 10% more efficient than a decade ago, but aviation has expanded by more than 10%.
If you want to reduce aviation CO2, you would need to make people poorer. Oh, wait a minute – thats what they are trying to do……
Ralph
Airliners travel at such altitudes because that’s where their engines are designed to be most efficient, including the drag reduction of a thin atmosphere. To travel much lower to avoid a contrail that’s only a problem in a warmist’s imagination we might as well go back to propellers.
Trouble is, contrail formation can occur in a wide range of altitudes depending on mountain ranges or open ocean.
The SR-71 Blackbird’s expensive A7 jet fuel was designed to minimise contrail formation in order to avoid detection, but if warmists are happy to pay for that fuel on their confab trips then it’s on their silly heads.
This is obviously a study looking for somewhere to die quietly. Let’s hope it’s lambasted for years to come and, that the “researchers” have to repay the grant money for their folly.
At least they finally recognized that water vapor is a greenhouse gas!
I know that this word is banned here, and I actually have something serious I could say here, but most serious stuff has been said, so I hope mr moderator, you’ll forgive me for saying that I think these guys brains have been fried by chemtrails.
wws says: June 19, 2014 at 7:18 am
but.. but.. if they stop making so many contrails, how will the men in black be able to get all the mind control chemicals into the atmosphere?
Wind farms.
I have read all the comments, we live close to an small size international airport and we also we see many intercontinental flight every day on the dot. One comment was that most planes fly by day, every flight longer than 9-10 hrs by hook or crook flies partly by night (E-W). But some of the comments about 911 and the shut down of airspace brought back a memory, the two days when flights were shut down I noticed an odd behavior with birds in our area (rural) to the point I had Stellar Jays landing on a yard table next to me and eventually sitting on my arm and eating (taking) food out of my hands it was an really neat thing but the thing that I remember most was the incredible silence those few days but the minute the air space was opened up the birds stopped coming close to us.
I keep birds, and aircraft are seen as a threat- like dirty big hawks. From the local birds’ points of view, near an airport, the sky would be constantly full of danger from above, hence their normal nervousness and lack of it when planes weren’t around.
ralfellis says:
June 19, 2014 at 5:05 pm
Pat.
The aviation industry has failed to cut CO2 despite tough national targets.
_____________________________
“Both true and nonsense simultaneously. New aircraft are some 10% more efficient than a decade ago, but aviation has expanded by more than 10%.”
For those opposed to aviation there are plenty of statistics that can be made to look bad. It is lazy and disingenuous for those not to even bother to understand what those numbers mean. For example here is a graphic of Heathrow Airport Statistics:
http://en.wikipedia.org/wiki/London_Heathrow_Airport#mediaviewer/File:London_Heathrow_Statistics.png
This shows that indeed there has been a massive increase, but in terms of passengers. The number of planes has not increased so dramatically. But which figure will be used. It is maddening that for all other transport modes utilisation is considered important, whereas for aviation its a criticism.
You mention aircraft efficiency but here again there is a tendency to not only move the goal posts but be on a different pitch. I came across this:
http://www.ipcc.ch/ipccreports/sres/aviation/114.htm#7106
“Aviation and the Global Atmospher
7.10.5.Other Contaminants from Supersonic Transport Engines
“At this stage, there is no reliable information relating specifically to the design of supersonic propulsion combustion systems, but there is no reason to believe that the degree of inefficiency should be any different from subsonic types. ”
INEFFICIENCY!!!! Apart from the fact this document talks about a type of transport that no longer exists, for the one type that did it was extraordinarily efficient. For Concorde during the Supersonic cruse only 8% of the power is derived by the engine with the other 29% being from Nozzles and an impressive 63% from the intakes. That 63% did not involve ANY fuel being burnt.
People are worried about a .01% increase in a beneficial invisible trace gas, thinking it will trap too much of the sun’s energy, yet they ignore very visible jet trails that are screening 50% of the sun’s energy and say it isn’t a problem.
And I said nothing. Because I didn’t have any flight time.
“but detailed calculations show … the warming effect [of clouds] wins over the cooling effect”. Models, perchance? Now pull the other one.
Sent from my Verizon 4G LTE Smartphone
Anthony, have you ever read Larry Niven’s “Fallen Angels”??? I think you’d like it.
“if you like your travel schedule, you can keep it.
If you like your airline, you can keep it.
Air travel will be 10 to 15% cheaper.
Millions of non-flyers will now be able to fly.”
According to this website:
http://www.indexmundi.com/energy.aspx?product=jet-fuel
the jets spewed about 1,800,000 barrels per day in 1984 up to over 5,200,000 barrels per day, today, 286,000,000 gallons per day. Think back to the week after 9/11. Did you notice how beautifully BLUE the sky became in a few days after 9/11 when they were all GROUNDED across America? The average Joe consumer was still driving his cars and pickup trucks so he wasn’t causing the whiteout sky we live with every day….286 million gallons of poorly burned kerosene burning in engines with NO POLLUTION CONTROLS were.
Duhhhh….Algore you watching this?