And then, they came, they came for your flight time…

320px-Qantas_Boeing_747-400_VH-OJU_over_Starbeyevo_Kustov[1]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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92 Responses to And then, they came, they came for your flight time…

  1. Patrick says:

    Insane!

  2. Sheffield Chris says:

    So, if this research is correct (?) the effect of the dreaded CO2 is reduced even further???

  3. Keith Willshaw says:

    So the conclusion is we must emit more CO2 to reduce global warming and wage war on the clouds.

    The lunatics have taken over the madhouse.

  4. Roy says:

    Obviously prices will rise if flights are longer and more fuel is used. The price rises might discourage some people from flying – but not the people flying to exotic locations to discuss “saving the planet!”

  5. Peter Ward says:

    Just how do artificially formed clouds cause global warming? Surely they reflect the sun and so reduce warming? And if these tiny contrails “cause global warming” then what about the steam that comes out of cooling towers? Perhaps we should forget carbon capture and just worry about the water vapour?!

  6. charles nelson says:

    I think there is a secret department that churns out stuff like this just to wind us up!

  7. Alex says:

    Institute of physics website;
    News of the day is football

    Enough said

  8. Rbravery says:

    It’s all pie in the sky if you ask me

  9. Phil says:

    This is how totalitarianism develops. Every single little aspect of life is analyzed and regulated to the slightest detail, until war comes and governments collapse. Then it’s back to just a struggle for survival. God help us all.

  10. Ed Zuiderwijk says:

    Shouldn’t planes take routes of optimal safety?

  11. Col Mosby says:

    Now, if they could only figure out CO2’s influence, they’d be able to solve their re-routing equations. Big if. Really big if.

  12. T.S. says:

    And then there’s this:
    Former White House climate czar joins board of natural gas exporter

    Heather Zichal, deputy assistant to President Obama for energy and climate change from 2011 to 2013, has joined the board of Cheniere Energy Inc., a large liquefied natural gas exporter, reports SNL. Zichal was credited with having helped shape many of the administration’s key energy and climate priorities, including fuel economy standards and clean energy investment. Cheniere is currently working to push for greater US LNG exports. Exports by the US and Canada of LNG — a supercooled form of gas — are expected to account for 8 percent of the world’s output by 2019, according to the International Energy Agency.

  13. wulliejohn says:

    The experiment has already been done.
    Following attacks on 9th September 2001 all flying over USA was stopped. No contrails. Ground temperatures rose.
    Now is time to ask for more funding to tweak that model.

  14. Olaf Koenders says:

    “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.”

    Hmm.. didn’t I hear something about this post 9/11? Ah.. here’s something:

    http://www.csmonitor.com/Environment/Bright-Green/2010/0201/Airplane-contrails-and-their-effect-on-temperatures

    “Of course, aviation’s real impact on climate probably has nothing to do with contrails. In 2005, NASA’s James Hansen published a study to that effect. He found that, even if the number of contrails were quintupled, global mean temperature would increase by just 0.03 degrees C (0.05 degrees F.).”

    So it means absolutely nothing anyway, coming from the Hansen’s mouth of all things. Here’s a correction:

    “The work waste of money 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.”

    Bah!

  15. Bloke down the pub says:

    If the air is already moist, then wouldn’t it already be absorbing infra-red? Why should it absorb more IR just because the moisture is in the form of a contrail?

  16. johnmarshall says:

    Contrails are like clouds they reduce incoming solar radiation so help cool the earth. this report is a pile of unsupported crap based on the GHE theory that has yet to be validated.

  17. somersetsteve says:

    Not even close to scientific…but….I was seated in my garden in UK yesterday on a beautiful sunny warm day in cloudless skies….when I noticed the brightness dim and the edge fall noticeably off the temp…looking up expecting to see a rogue cloud I in fact saw a broad contrail dimming the sun. The effect lasted around 15 mins until the contrail drifted out of alignment…..

  18. probono says:

    Somebody needs to sit this guy in a desert and see if he starts to cry when a cloud comes by.

  19. Alan the Brit says:

    “and weather forecasters would need to establish if they can reliably predict when and where contrails are likely to form.”

    Gathering around their boiling pot with leg of toad & eye of newt, & a few droplets of blood from a virgin, no doubt! Sheeesh!!! & reading University, fourth rate at best, unless you’re a warmista of course, then it is probably at the best out there!

  20. Mike T says:

    Ed Zuiderwijk says:
    June 19, 2014 at 1:02 am
    Shouldn’t planes take routes of optimal safety?

    Aircraft normally take the route where the benefit from upper winds is most beneficial (or least bad, if they can’t avoid headwinds) in terms of fuel consumption. This often results in strange flight paths, to the lay person, especially when combined with great circle routes on a Mercator projection map.

  21. Telboy says:

    It’s like saying “How many angels can dance on the head of a pin, and how many fewer if they’re wearing clogs?” What action can we take to further mitigate a non-existant problem thereby causing more disruption?
    Unbelievable.

  22. M Seward says:

    This isn’t hair splitting eco-loonism, this is nanofibre splitting and then obsessing if the split is along the exact centre. WTF is in the water at Reading?

  23. Stephen Skinner says:

    “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”

    I bet it hasn’t shown anything of the sort. Probably models. Confirmation bias seems to be large or larger than expected..

  24. faboutlaws says:

    How many miles does Obama fly on the largely empty Air Force One? How many of them are to progressive fund raisers? How much contrail does he create? Obama’s carbon footprint exceeds Godzilla’s by several orders of magnitude. And Godzilla is a whole lot more cuddly.

  25. John S. says:

    I recall a brief study by David Travis that looked at average temperatures before, during, and after the three day grounding of aircraft in the United States after 9/11. I believe he concluded that contrails raise nighttime temperatures, and lower daytime temperatures.

  26. beng says:

    Warmers trying to change the definition of a straight line…

  27. Scott says:

    I’m still trying to understand what our middle school principal meant during the global warming portion of the graduation speech when he said that kids would have to say “no” to flying on planes so much like we did, then later said kids might have to change jobs more often and so might have to go back to school to be trained as a pilot.

  28. philjourdan says:

    Are they channeling callers to George Noory? Sure sounds like it. So now contrails are responsible for AGW.

  29. Santa Baby says:

    Jet cirrus clouds could in theory warm up the surface below, and some days you can have a lot of jet cirrus. But this leading to global warming?
    http://cnls.lanl.gov/~petersen/f/headers/jet.gif

  30. Paul says:

    We’re developing technology to increase aircraft cruise efficiency. And never thought of using CO2 reduction as a selling point. That should help with funding.

  31. Just an engineer says:

    Let’s see if I have this right, “since the net demonstrated effect of increased atmospheric CO2 is approximately zero”, then ANYTHING may have a greater effect on “global warming”!

  32. Brian says:

    This is stupid. Vapor trails form from condensing water of combustion. The amount of combustion H2O will be the same regardless of the formation of vapor trails.

  33. Magic Turtle says:

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

    This “research” is pure conjecture with no empirical validation – an untested, unproven application of preconceived untested, unproven global warming ideology. This is the kind of vacuous pseudoscience that “informs” the policy-decisions of our political decision-makers. It is pretentious rubbish but useful in showing those of us who care to look at it how the Emperor’s New Green Clothes are being fabricated.

  34. Andrew says:

    Sorry but are they quantifying and instantaneous impact or are they seriously arguing that trails are persistent enough to match the half life of CO2? If so, great news – it means CO2 lasts a matter of minutes.

  35. wulliejohn said, June 19, 2014 at 1:10 am:

    “The experiment has already been done. Following attacks on 9th September 2001 all flying over USA was stopped. No contrails. Ground temperatures rose.”

    National average temperature normally fluctuates as weather systems pass through. The warmer times were probably related to the terrorists’ choice of when to attack. They apparently wanted good weather to make their attacks more visible.

  36. jlkinsella says:

    If you change flight paths and burn more fuel, you will produce both more water and more CO2. Why would this extra water not matter in their calculations?

  37. lenbilen says:

    So, if the earth is warming shouldn’t we try to form more contrails during the day when they are cooling and less during the night when they reflect back radiation? Was that part of the calculation, or did they miss the point it matters when clouds and contrails are formed?
    I still vote for most efficient and least turbulent route when flying.

  38. Steve from Rockwood says:

    Fly less. Or was that idea shot down by Sir Richard Branson?

  39. Tom O says:

    “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.”

    I have rarely seen a “contrail” last for any length of time and certainly not spread out and resemble natural, wispy clouds. I have watched high flying jets for probably 50 years, and although contrails can survive for a while, they are normally long and thin when they dissapate. What she is referring to has nothing to do with contrails, thus she is either incredibly misinformed or is intentionally misinforming others about an unnatural event.

  40. ferdberple says:

    the authors have it backwards. the grounding of aircraft during 911 increased temperatures.

  41. ferdberple says:

    Detailed calculations indicate that generally the warming effect wins over the cooling effect.
    =============
    try using detailed measurements instead.

  42. more soylent green! says:

    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.

    I don’t believe it. I’m from Missouri. Show me.

  43. John Boles says:

    And after they concluded the study they got in their SUVs and drove home…

  44. Adam says:

    OMG… cue the chemtrail nutbags!

  45. The article was insufficiently clear about the differential effects of high-altitude and low-altitude clouds. All other things being equal, high altitude clouds and low altitude clouds reflect the same amount of sunlight. However, high altitude clouds also block outgoing long-wave radiation from the atmosphere under them, while the atmosphere above low altitude clouds has an unobstructed view of space. That gives high, thin cirrus clouds a net warming effect, and low cumulus and stratus clouds a net cooling effect.

    Having said that, rerouting jets to avoid making contrails is very silly. Who volunteers to be the first passenger or crew member injured by routing travel into turbulence to avoid making a contrail?

  46. Bryan A says:

    Peter Ward says:
    June 19, 2014 at 12:35 am
    Just how do artificially formed clouds cause global warming? Surely they reflect the sun and so reduce warming? And if these tiny contrails “cause global warming” then what about the steam that comes out of cooling towers? Perhaps we should forget carbon capture and just worry about the water vapour?!

    At Lower altitudes, Thick clouds act to block sunlight from reaching the ground and thereby lower temperatures as the shortwave IR can’t enter the system by reaching the ground. Higher Whispy clouds reflect the Longer Wave IR that comes from the planet and prevent it from exiting to space retaining the heat in the system

  47. wally says:

    FAA has spent billions on developing new tracking systems that can’t be implemented. So to save a few carbon credits we are to spend billions mapping out vapor pressure so planes can avoid them?

    Best and brightest working this “real world problem”.

  48. wws says:

    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?

  49. elmer says:

    It seems that the increase in contrails happened around the same time the “pause” started, so we have been accidentally geoengineering the planet.

  50. elmer says:

    This does prove that clouds have more impact on temps than CO2.

  51. Alan McIntire says:

    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.

  52. tty says:

    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.

  53. Dale Monceaux says:

    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.

  54. kcrucible says:

    ” 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.

  55. Kenw says:

    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.

  56. Sandi says:

    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.

  57. Titan28 says:

    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?

  58. Shawn from High River says:

    Wait……..so now scientists have a complete understanding of clouds,how they form and their contribution to global warming ?
    That’s amazing!

  59. tommoriarty says:

    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/

  60. elmer says:

    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.

  61. Chuck Nolan says:

    So we have something else that just might be more important to the climate than CO2.
    Who’d-a-thunk-it could be?
    cn

  62. Stephen Skinner says:

    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.

  63. 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?

  64. tadchem says:

    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. :(

  65. more soylent green! says:

    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?

  66. Another addition to the list of Global Warming “Facta”. ;-D

  67. 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.

  68. 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. :-(

  69. more soylent green! says:

    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.

  70. 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

  71. Alan McIntire says:

    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” .

  72. 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.

  73. Bruce Cobb says:

    They went looking for a “warming effect”, and, wonder of wonders, eureka, they found it!
    The joys of climate scientology.

  74. ralfellis says:

    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

  75. more soylent green! says:

    @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.

  76. ralfellis says:

    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

  77. pat says:

    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

  78. ralfellis says:

    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

  79. Olaf Koenders says:

    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.

  80. Leonard Jones says:

    At least they finally recognized that water vapor is a greenhouse gas!

  81. Tom Trevor says:

    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.

  82. Mike McMillan says:

    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.

  83. asybot says:

    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.

  84. Mike T says:

    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.

  85. Stephen Skinner says:

    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.

  86. elmer says:

    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.

  87. evanmjones says:

    And I said nothing. Because I didn’t have any flight time.

  88. Brian H says:

    “but detailed calculations show … the warming effect [of clouds] wins over the cooling effect”. Models, perchance? Now pull the other one.

  89. Rich Apuzzo says:

    Sent from my Verizon 4G LTE Smartphone

  90. Ralph says:

    Anthony, have you ever read Larry Niven’s “Fallen Angels”??? I think you’d like it.

  91. Martin Mayer says:

    “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.”

  92. Larry Butler says:

    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?

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