BBC - Longer flights to curb vapour trails

MyMatesBrainwashed

Senior Member
Article from the BBC website that discusses the extra fuel needed to avoid producing persistent contrails could have less of impact on the global climate than the trails themselves.

http://www.bbc.co.uk/news/science-environment-27907399

I am going to preempt that this means the conspiracists have won. Too many people are now noticing these trails that they have had to come up with an excuse to stop producing them. Woo, yeah, fight the good fight.
 
Here is the actual study:
http://iopscience.iop.org/1748-9326/9/6/064021/article
Persistent contrails are an important climate impact of aviation which could potentially be reduced by re-routing aircraft to avoid contrailing; however this generally increases both the flight length and its corresponding CO emissions. Here, we provide a simple framework to assess the trade-off between the climate impact of CO emissions and contrails for a single flight, in terms of the absolute global warming potential and absolute global temperature potential metrics for time horizons of 20, 50 and 100 years. We use the framework to illustrate the maximum extra distance (with no altitude changes) that can be added to a flight and still reduce its overall climate impact. Small aircraft can fly up to four times further to avoid contrailing than large aircraft. The results have a strong dependence on the applied metric and time horizon. Applying a conservative estimate of the uncertainty in the contrail radiative forcing and climate efficacy leads to a factor of 20 difference in the maximum extra distance that could be flown to avoid a contrail. The impact of re-routing on other climatically-important aviation emissions could also be considered in this framework.
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This is not really anything new, suggestions for avoiding contrail areas have been around for a while. Here's a similar paper from 2011
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20110008150_2011007211.pdf

And 2005:
http://dspace.mit.edu/handle/1721.1/32460
Given perfect knowledge of meteorological data and no air traffic controls, if aircraft were individually rerouted, it was possible to mitigate 65%-80% of persistent contrails and simultaneously achieve an average decrease of 5%-7% of the total operating cost for the week in November 2001 for which this analysis was carried out. These reductions are relative to the actual routes flown by the aircraft during this week, reflecting the impact of non-optimal routing not only on contrail formation, but also on fuel bum and operating costs in general.
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Another:
http://dspace.mit.edu/bitstream/handle/1721.1/85768/871330199.pdf?sequence=1


Back in 2002 there were suggestions for flying lower - as it's always been known you could avoid contrails by simply reducing altitude.
http://www.tandfonline.com/doi/abs/10.3763/cpol.2003.0328#.U6L7v2Qv-Gk
While quantification of the effects of NO x and water vapor is still at an early stage there is evidence that contrail formation could make a significant contribution to global warming. This paper builds on previous research that analyzed a policy of restricting air transport cruise altitudes to eliminate contrail formation. Our previous work [Transport. Res. D 7(6) (2002) 451], examined altitude restrictions in European airspace and concluded that this could be a beneficial policy for reducing climate change impacts from aviation. Since most of the flights in European airspace are short-haul flights, this paper evaluates the trade-offs between altitude restrictions, fuel burn and journey times for longer haul flights of up to 6000 nm. Our focus is on the North Atlantic and US airspace and we examine potential contrail fraction to determine optimal cruise altitudes for reducing contrail formation. Changes in fuel burn and travel times associated with flight levels of 18,000 and 31,000 ft for different aircraft types are analyzed. We find that, in most cases, CO2 emission increases would be unlikely to entirely counteract the benefit of possible reductions in contrail formation. For some aircraft types, the percentage increase in emitted CO2 was found to be strongly dependent on journey length. In general, journey times appear not to be a major issue except for some aircraft types. Our results suggest that reducing aircraft cruise altitudes could be a beneficial policy for mitigating climate change impacts from the aviation sector. This is clearly dependent on aircraft type and the distances traveled, but more importantly on ambient atmospheric conditions which can vary significantly between regions and due to daily variation. This suggests that real time flight planning to minimize contrail formation should be investigated as a possible climate mitigation policy.
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The extra fuel has always been an issue with that, so a fine-tuned computer controlled system has always looked like the best bet. IBM patented such as system in 2008 - although they describe increasing contrail cover in some places and decreasing it in others, to modulate energy usage from AC and heating on the ground.
http://www.google.com/patents/US20090319164
A method for controlling aircraft contrail placement including detecting an aircraft contrail, determining an approximate location of the aircraft contrail based on at least one of detected aircraft contrail pan information, tilt information, or zoom information, transmitting contrail detection information and contrail location information to a centralized controlling unit, matching the contrail location information with a database of known GPS coordinates to identify the contrail producing aircraft, determining a boundary for an energy management area, determining an amount of cloud cover over the energy management area, determining an optimal cloud cover amount for the energy management area, and transmitting a re-route request to the identified contrail producing aircraft to re-route toward or away from the energy management area based on the determining an amount of optimal cloud cover amount for the energy management area.
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Similar article on the Daily Mail, which has started to put actual science in little Orange boxes
http://www.dailymail.co.uk/sciencet...r-conditions-help-prevent-global-warming.html

Aviation carbon dioxide emissions accounted for 6 per cent of UK total greenhouse gas emissions in 2011.
Global Carbon dioxide emissions from aviation were estimated at 630 million tonnes of CO2 for 2005. This is 2.1 per cent of the global emissions of carbon dioxide in that year.
Previous research by scientists at the university has shown that, on average, 7 per cent of the total distance flown by aircraft is in cold, moist air where long-lasting contrails can form.
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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The comments there have a lot of chemtrail folk, who are also discussing the science on Twitter:
 
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Has anyone really done the math on this? If there are no contrails, the main emission is gaseous water vapor, which is a more effective greenhouse gas than CO2. If there are contrails, the contrail cirrus clouds consisting of frozen water droplets, have mixed effects, trapping heat but also reflecting sunlight. The graph that has been posted a couple of places on this site shows a large degree of uncertainty on the effects of contrail cirrus.
 
No. and No.
Maybe you misunderstand me but one of the comments on the Daily Mail site already confirms this

Trivializing the disgraceful transformation of the sky and the atmosphere. I think they've been monitoring the concern over chemtrails and have asked you to put your name to this propaganda, Sarah Griffiths.
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Has anyone really done the math on this? If there are no contrails, the main emission is gaseous water vapor, which is a more effective greenhouse gas than CO2. If there are contrails, the contrail cirrus clouds consisting of frozen water droplets, have mixed effects, trapping heat but also reflecting sunlight. The graph that has been posted a couple of places on this site shows a large degree of uncertainty on the effects of contrail cirrus.

They have certainly done some math, and are aware of uncertainties.

http://iopscience.iop.org/1748-9326/9/6/064021/article

This framework is useful to show where the major uncertainties are. Joos et al (2013) find that calculations of the atmospheric COresponse agree within 15%, thus the climate impact of the flightʼs CO emissions can be calculated with a relatively small uncertainty, given knowledge of aircraft fuel burn. The calculation of the climate impact of the contrail has a much larger uncertainty. The uncertainty chiefly arises from two sources: an inability to estimate, a priori, the eventual size and therefore climate impact of the contrail that would be formed, and second the radiative forcing (which has a potential dependence on the time of day, not taken into account here) and climate efficacy of that forcing. Even if the radiative forcing were calculated operationally within a forecast model, there would still be an uncertainty in the size of the calculated radiative forcing due to the radiative forcing codes (Myhre et al 2009), and also due to uncertainty in the contrail characteristics. Taking into account the uncertainty in the eventual climate impact of a contrail of 100 km length, the estimate of the maximum diversion distance varies by a factor of 20.

The application of such a strategy in the real world would require highly accurate forecasts of ISSRs where potential contrails form, and the ability to know a priori the climate impact of a potential contrail, as well as being highly dependent on air traffic control and other operational and economic considerations. In addition, the overall climate impact of the flight should take into account the chemical forcings from aircraft emissions; detailed calculations of such 'climate optimal' routings are currently being performed by the REACT4C project. We note here that for small horizontal diversions it is possible that the chemical forcings between the two routes would be comparable; however since the impact depends on where the emissions are advected, small diversions could potentially result in large differences in impact (Grewe et al 2014). The impact of black carbon and other aerosol emissions may also be important and could be incorporated in more detailed estimates (Jacobson et al 2012).

Nevertheless, despite the uncertainties, the calculations presented here indicate that once a metric (and time horizon) choice has been made, guidance can be given as to whether it is beneficial to divert to avoid contrails. So for example, adding 100 km distance to a flight to avoid making a contrail would seem beneficial for many of the cases presented here, and other parameter choices, such as the extreme high values in Haywood et al (2009), could allow significantly longer diversions.
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Don't expect such discussion in the Dail Mail (or even the BBC) :)
 
Maybe you misunderstand me but one of the comments on the Daily Mail site already confirms this

Trivializing the disgraceful transformation of the sky and the atmosphere. I think they've been monitoring the concern over chemtrails and have asked you to put your name to this propaganda, Sarah Griffiths.
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all the article does is concur with everything the debunkers have been saying for years. That contrails are due to Weather Conditions and altitude. That contrails are too long (mass size) to be "chemtrails" and that contrails are just manmade clouds, that sometimes spread out just like clouds do.
 
all the article does is concur with everything the debunkers have been saying for years. That contrails are due to Weather Conditions and altitude. That contrails are too long (mass size) to be "chemtrails" and that contrails are just manmade clouds, that sometimes spread out just like clouds do.
Yeah, but if you expect the conspiracists to accept that then you are sorely mistaken. Cos they can easily come up with excuses like the one I suggested. And they will do.

At some point you have to realise you are arguing for the "no win" team and they are arguing for the "no lose" team. Although ultimately there are no winners.
 
Article from the BBC website that discusses the extra fuel needed to avoid producing persistent contrails could have less of impact on the global climate than the trails themselves.

http://www.bbc.co.uk/news/science-environment-27907399

I am going to preempt that this means the conspiracists have won. Too many people are now noticing these trails that they have had to come up with an excuse to stop producing them. Woo, yeah, fight the good fight.

From that article:

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.
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I think they have those two numbers reversed.
 
Yeah, but if you expect the conspiracists to accept that then you are sorely mistaken. Cos they can easily come up with arguments like the one I suggested. And they will do.

At some point you have to realise you are arguing for the "no win" team and they are arguing for the "no lose" team. Although ultimately there are no winners.

It is true that you can't stop people who are determined and willing to make up nonsense. to support their position. The bunk machine never sleeps. :rolleyes:
 
Yeah, but if you expect the conspiracists to accept that then you are sorely mistaken. Cos they can easily come up with excuses like the one I suggested. And they will do.

At some point you have to realise you are arguing for the "no win" team and they are arguing for the "no lose" team. Although ultimately there are no winners.
that's ok. I'd rather be right. Plus all the cool guys are on my side.. the scientists and astronauts and jet fighter pilots etc.
 
While the paper is very interesting it will not change the appearance of those lines in the sky as it is only applicable to intercontinental flights. I hazard a guess that diverting traffic is impractical for EU domestic airspace.
 
It's important to note that Flight Planning scenarios (especially very long-range) involve other more important considerations than just "avoiding" the production of a contrail.

(And yes, this is a type of "Chicken Little says 'The sky is falling!' " example of false hysteria, the "concern" about contrails).

The prevailing forecast winds for the route can have a significant effect on flight times, and thus fuel burn rate. Also, many airlines use predicitve tools to help avoid turbulence en-route as much as possible. All of these considerations result in compromises, sometimes....then there also sometimes ATC-mandated routing procedures.....
 
While the paper is very interesting it will not change the appearance of those lines in the sky as it is only applicable to intercontinental flights. I hazard a guess that diverting traffic is impractical for EU domestic airspace.

One of the other papers suggests that shorter flights should fly at lower altitudes, a different type of trade-off.
 
One of the other papers suggests that shorter flights should fly at lower altitudes, a different type of trade-off.

That actually might need to become a "norm" in EU airspace, just merely because of the congestion. And for shorter flights, the increase in amount of fuel used is only slight....however as with everything, it does add up flight-by-flight.

The general consensus was, even for very short lengths, to go as high as possible. Examples such as Houston (Texas) to Austin. About 30 minutes total, lift-off to landing. Yet we'd typically file for altitudes such as 32,000 or 34,000 feet. And, about one minute after reaching the cruise altitude, we'd then begin the arrival descent. So, the theory is yes you've been running the engines at high power setting for about 15 minutes in the climb, but then they are mostly at or near idle during the last 15 minutes.
 
One of the other papers suggests that shorter flights should fly at lower altitudes, a different type of trade-off.
Just reading a paper cited in the original post http://www.aviationsystemsdivision.arc.nasa.gov/publications/2013/ATM2013_Sridhar_Final.pdf

The concluding remarks are interesting in that they note that altitude changes on an "as and when" basis are more fuel efficient than a permanent reduction in altitude.

However just from reading information on here, for Europe, what would be the day to day practicalities especially with regards for air traffic control and how much fuel etc.
 
From that article:

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.
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I think they have those two numbers reversed.

Nope, read it again.;) They are saying theoretically, an aircraft could divert by as much as 10x distance before the fuel emissions outweighs the contrail emissions in terms of damaging the climate. ie, 10km of fuel burnt has the same warming effect as 1km contrail

ETA: "Ladies and gentleman, this is your captain speaking. Our new contrail-aversion system estimates our arrival time will be extended by a factor of nine. Have a nice flight."
 
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Nope, read it again.;) They are saying theoretically, an aircraft could divert by as much as 10x distance before the fuel emissions outweighs the contrail emissions in terms of damaging the climate. ie, 10km of fuel burnt has the same warming effect as 1km contrail

Yes, that's the conclusion of the paper:
http://iopscience.iop.org/1748-9326/9/6/064021/article
The framework calculates the maximum extra distance that can be added to a flight, before the additional CO emissions outweigh the benefit of not contrailing. As the quantity of CO emissions depends on aircraft type, any decision to avoid making the contrail would be highly dependent on aircraft type. For example, using the AGWP metric with 100 year time horizon, the extra distance that a small jet can fly is more than ten times the avoided contrail length, whilst for a very large jet this reduces to three times. As discussed by Deuber et al (2013), it is important to choose a suitable metric, depending on the required outcome. Here, we find a factor of 3–10 difference between the AGTP and AGWP results, depending on the time horizon used
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Nope, read it again.;) They are saying theoretically, an aircraft could divert by as much as 10x distance before the fuel emissions outweighs the contrail emissions in terms of damaging the climate. ie, 10km of fuel burnt has the same warming effect as 1km contrail

ETA: "Ladies and gentleman, this is your captain speaking. Our new contrail-aversion system estimates our arrival time will be extended by a factor of nine. Have a nice flight."

OK, I see it now, but that hardly seems practical.
 
OK, I see it now, but that hardly seems practical.

No it's not, but that's was just the upper bound. The paper suggests much more modest course alterations can be used, especially on longer flights. Like here, an extra 22km across the Atlantic:
 
And it all hinges on contrail-formation predictions. Can't see it flying imho (excuse the pun) or is the science that good now?
 
Will the persistent contrail have the same climate impact regardless what lays below: a landmass or an ocean? Would be there any gain from the contrail avoidance if the ground below is already obscured by a cloud layer?
 
Will the persistent contrail have the same climate impact regardless what lays below: a landmass or an ocean?
Probably. It's going to depend on the albedo and emissivity of the ground/sea, and various other factors.

Would be there any gain from the contrail avoidance if the ground below is already obscured by a cloud layer?

The climate effect they want to prevent is warming (or rather a reduction in cooling) this happens at night. It's quite complicated - but yes, existing cloud will have an effect. They would have to model all kinds of factors to arrive a optimum routes.
 
No it's not, but that's was just the upper bound. The paper suggests much more modest course alterations can be used, especially on longer flights. Like here, an extra 22km across the Atlantic:

That diagram becomes impractical because of the NAT system.


So, every parallel NAT Track would need to be adjusted with the same "bend" in the route, to maintain the required lateral separation (One degree of Latitude, about 60 Nautical miles).

Note that there is a procedure (since 2004) called "SLOP" --or, Strategic Lateral Offset Procedure" but this limits parallel route offsets to 1 or 2 miles.
 
Yeah, it would require replacing the NAT system with some kind of satellite based computer controlled ATC that can freely route planes. Rather a significant undertaking.
 
And since flights are already in the air when an alteration of a subsequent flight was wanted, it all sounds hopelessly complicated.
 
And since flights are already in the air when an alteration of a subsequent flight was wanted, it all sounds hopelessly complicated.

The complexity is easily solved by computers, however it requires an integrated system, so they can avoid hitting each other. Such a system will probably happen this century, and tacking on contrail mitigation/creation would be an incremental feature.
 
The complexity is easily solved by computers, however it requires an integrated system, so they can avoid hitting each other. Such a system will probably happen this century, and tacking on contrail mitigation/creation would be an incremental feature.
wouldn't it be easier to just build nuclear plants or windmill farms for developing countries?
 
wouldn't it be easier to just build nuclear plants or windmill farms for developing countries?

No. Computerised air traffic is going to happen. Weather monitoring and forecasting happens. So it's reasonably cheap (compared to building a nuclear power station) to do some programming to link them to modulate contrails.

I don't think it's a huge factor though, just another tool in the arsenal.
 
The complexity is easily solved by computers, however it requires an integrated system, so they can avoid hitting each other. Such a system will probably happen this century, and tacking on contrail mitigation/creation would be an incremental feature.

I suppose, but any gains would be marginalized by having planes which haven't taken the altered routes from takeoff having to change course to accommodate for changes on other flights, shifting the entire fleet around all the time. It seems like it would be a case of diminishing returns.
 
I will say this: The #1 factor when it comes to our flight planning (besides safety of course) is fuel savings. I would guarantee the airlines are the same way. We are ALWAYS trying to fly high and at optimum airspeed in order to save fuel. If we are flying into select military bases, they even take away our fuel required for an alternate, since there are so many other fields nearby. At no time have we compromised this in order to create less contrails in the skies, the only pilots I have known who care about that issue are the B2 Stealth pilots, since it factors into their visibility while flying, for obvious reasons.
 
I will say this: The #1 factor when it comes to our flight planning (besides safety of course) is fuel savings. I would guarantee the airlines are the same way. We are ALWAYS trying to fly high and at optimum airspeed in order to save fuel. If we are flying into select military bases, they even take away our fuel required for an alternate, since there are so many other fields nearby. At no time have we compromised this in order to create less contrails in the skies, the only pilots I have known who care about that issue are the B2 Stealth pilots, since it factors into their visibility while flying, for obvious reasons.
the gov. will have to give them tax credits. cause yea, hurting the economy just makes the climate issue worse.
 
....the only pilots I have known who care about that issue are the B2 Stealth pilots, since it factors into their visibility while flying, for obvious reasons.

Yeah, good point.

Contrails ARE a consequence of burning fossil fuels in certain temperature/atmospheric conditions.

PERIOD!!

(This is going out to any in the public who might be enjoying this thread discussion). The very concept of "Stealth" (such as B-2 bomber, the F-117, or any other future design) is harmed when the very engines that these jets need, burning NORMAL jet fuel, can give away your position!!
 
I suppose, but any gains would be marginalized by having planes which haven't taken the altered routes from takeoff having to change course to accommodate for changes on other flights, shifting the entire fleet around all the time. It seems like it would be a case of diminishing returns.
The computers would account for that. There is plenty of room in the sky if you know exactly where everyone is.
 
The computers would account for that. There is plenty of room in the sky if you know exactly where everyone is.

AGAIN.....this is the (very near future) concept of what has been proposed (for the future) and dubbed "Free Flight".

Yes, this WILL be the way of the future for air travel. It will evolve. There are huge obstacles in that path to 'evolution'...but it will, one day, be commonplace. (**)

EDIT: Only one of a few problems I can foresee will be (as usual) the Human element. NO system or method is "perfect". Technology can account for much of (expected) Human error....but not ALL of it.

(**) Just as, back when I started in aviation, there was no such thing as GPS. We adapted the technology, it improved many aspects of aviation. Such improvements WILL continue, moving forward in time.
 
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EDIT: Only one of a few problems I can foresee will be (as usual) the Human element. NO system or method is "perfect". Technology can account for much of (expected) Human error....but not ALL of it.

and that is why the aircrew of the future will be just 1 pilot and a dog - the pilot's job is to feed the dog, and the dog's job is to bite the pilot if s/he tries to touch anything.
 
I recall a contrail mitigation study that concluded that persistent contrails could be avoided 80% of the time with an altitude change of less than 2000 feet. A note on how to take into account the aircraft induced cloudiness in the EU-ETS (see pages 6 and 7).

A lowering of altitude into warmer air, where contrails will not form at all, is pretty sure-fire but you would burn much more fuel.
You could also climb into (possibly) drier air and avoid persistent contrail conditions. That will invite bring other dangers, like "coffin corner" where the aircraft's safe airspeed range is seriously diminished between high-speed buffet and low-speed stall. (A pilot could expand a bit on this.)

Diverting horizontally seems the hard way to do it. The atmosphere is quite delicately layered, so a change in altitude is the way to go. IMO.
 
and that is why the aircrew of the future will be just 1 pilot and a dog - the pilot's job is to feed the dog, and the dog's job is to bite the pilot if s/he tries to touch anything.

Old. Joke. (And I am old enough to recall when it first came out...).
 
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