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Airplanes Cause Accidental Cloud Seeding

An anonymous reader writes "A new study by a team of U.S. researchers found that commercial and private jetliners may be contributing to a form of accidental cloud seeding. When an airplane flies through a cloud, its propellers cause the expansion and cooling of the air behind them which can cause water droplets to spontaneously cool and crystals to form. The aircraft sets off a chain reaction in the cloud that can continue on for hours after the plane has passed by. The researchers also discovered that this phenomenon is more common near the poles, where many of Earth's weather monitoring systems are, and it could be skewing data that research teams are gathering in those areas."

151 comments

  1. "Propellors"? by Anonymous Coward · · Score: 0

    Now you're into the time slip...

    1. Re:"Propellors"? by petteyg359 · · Score: 1

      They're those things that spin around on a motor. They're quite useful, because they behave differently than jet engines in certain conditions.

    2. Re:"Propellors"? by Osgeld · · Score: 0

      oh we know what they are, but when was the last time you saw a commercial plane with them? let alone a propeller powered commercial jetliner...

      this entire thing stinks of stupid

    3. Re:"Propellors"? by petteyg359 · · Score: 1

      Did you miss that first sentence of the summary where it clearly said " private and commercial"?

    4. Re:"Propellors"? by dave420 · · Score: 2

      Ever heard of a Turboprop engine? They're extremely common.

    5. Re:"Propellors"? by Wyatt+Earp · · Score: 4, Informative

      I saw some yesterday, Dash-8s and there a lot of other propeller commercial aircraft out there.
      http://en.wikipedia.org/wiki/Bombardier_Dash_8 - turboprop
      http://en.wikipedia.org/wiki/Beech_1900 - turboprop
      http://en.wikipedia.org/wiki/Cessna_406 - turboprop

      We even have one of these flying out of Anchorage
      http://en.wikipedia.org/wiki/Lockheed_L-100_Hercules along with
      http://en.wikipedia.org/wiki/DC-3
      http://en.wikipedia.org/wiki/DC-6
      http://en.wikipedia.org/wiki/Short_360

    6. Re:"Propellors"? by Sicily1918 · · Score: 1

      In commercial aircraft? Even private airliners use jet turbines...

    7. Re:"Propellors"? by dave420 · · Score: 4, Interesting

      Yes - in *plenty*. It amazes me that people don't know that. There are a shit-tonne of turboprop aircraft the world over, including the US.

    8. Re:"Propellors"? by Adriax · · Score: 1

      Not on my first/last/only flight 5 years ago.
      Twin prop engine, only 4 seats wide, out of a small town airport on behalf of Delta. Not everything is a jumbojet out of LAX/Seatac/ect...

      --
      I don't suffer from insanity, I enjoy every minute of it!
    9. Re:"Propellors"? by Travelsonic · · Score: 2

      .. but when was the last time you saw a commercial plane with them?

      Actually, just before the sun set - a DeHavilland/Bombardier Dash-8 of US Airways Express.

      --
      If you believe in privacy, and believe you have "nothing to hide" at the same time, you're a goddammed idiot
    10. Re:"Propellors"? by Scrameustache · · Score: 1

      last time you saw a commercial plane with them?

      Must have been a few days ago, I don't usually bother to look at every plane that goes by, but if I want I'll see a commercial propeller plane go by within the hour, I just have to go out and point my nose up.

      --

      You can't take the sky from me...

    11. Re:"Propellors"? by the+linux+geek · · Score: 1

      Constantly. US Air especially uses props for short-hop flights.

    12. Re:"Propellors"? by RoFLKOPTr · · Score: 1

      this entire thing stinks of stupid

      You stink of stupid.

      Domestic airports in relatively-major cities (relative to their surrounding area... think Bakersfield, Billings, etc) don't usually have big enough runways to support large jets, so they use regional jets and turboprops. The big airlines usually don't run their own small planes. Rather, they use a different banner (United Express, Ted, Delta Connections, etc) for their regional services and usually contract that out to smaller airlines. I used to fly from California to South Dakota for a hunting trip every year, and usually United would put me in a 737 from SFO to Denver, and I'd get in a United Express EMB120 operated by SkyWest. That is one tiny freaking plane. 30 passengers. It's a fun ride as you're descending through the bumpy South Dakotan air.

      No, there aren't any 737-sized turboprops, but there are plenty of commercial planes with propellers.

    13. Re:"Propellors"? by Deadstick · · Score: 1

      Oh, fer chrissake...google "Beech 1900" or "ATR-72" or "Embraer Bandeirante", among others.

      rj

    14. Re:"Propellors"? by magarity · · Score: 1

      Did you miss that first sentence of the summary where it clearly said " private and commercial"?

      I didn't miss it but apparently you missed the part about 'over the poles'. And they didn't mean poles as in Polish people.
       
      The only prop aircraft over the poles is the (very) occasional TU95 Bear bomber.

    15. Re:"Propellors"? by MichaelSmith · · Score: 1

      propeller powered commercial jetliner

      Turbo props are used for short distance commercial transport, especially between small airports and where demand is low. They use turbojet engines.

    16. Re:"Propellors"? by MichaelSmith · · Score: 1

      I have never once seen a privately owned turboprop. They are basically workhorses for middle range airlines and commercial operations which need to carry a lot of stuff with short strip capability. Air ambulances for example.

    17. Re:"Propellors"? by rossdee · · Score: 1

      Smaller commercial planes are sometimes turboprop powered. I last flew on one 10 years ago, but I am sure they are still in service on small city to city routes of 300 miles or less.

    18. Re:"Propellors"? by jimmydevice · · Score: 1

      Did you miss the "commercial and private jetliners" in the first sentence?

    19. Re:"Propellors"? by MacGyver2210 · · Score: 1

      A turbine is just a propeller with a hell of a lot more blades...it would logically have the same effect, if not more.

      --
      If the only way you can accept an assertion is by faith, then you are conceding that it can't be taken on its own merits
    20. Re:"Propellors"? by stox · · Score: 2

      Most jet engines, these days, are high bypass turbofan engines. In many respects, not that much different from a Turboprop. The bulk of the thrust comes from the driven element, ie. the fan or prop, rather than the thrust from the turbine itself.

      --
      "To those who are overly cautious, everything is impossible. "
    21. Re:"Propellors"? by starblazer · · Score: 1

      The big airlines usually don't run their own small planes. Rather, they use a different banner (United Express, Ted, Delta Connections, etc) for their regional services and usually contract that out to smaller airlines.

      TED was never a small plane airline, it was a "vacation" subsidary of United. It never flew anything smaller than an A320. Now, Anything "Express, Connection" or pretty much most planes from Republic Air Holdings (short of the small fleet of A319s it acquired from Frontier) is RJ.

    22. Re:"Propellors"? by antifoidulus · · Score: 1

      Yup and their numbers will probably increase, not decrease at least in the near future because of their fuel efficiency. A turboprop uses considerably less fuel than a jet, esp. for short to medium distances.

    23. Re:"Propellors"? by mcavic · · Score: 1

      That was going to be my suggestion.

    24. Re:"Propellors"? by DougF · · Score: 3, Informative

      Fail. The LC-130H is commonly seen over both the Arctic and Antarctic, and it has 4 props and skis.

      --
      Impetuous! Homeric!
    25. Re:"Propellors"? by capnkr · · Score: 1

      FYI - a 'turboprop' engine is basically a jet engine (or "gas turbine") powering a propeller; the turbine powerplant is more efficient, more mechanically reliable, and has longer TBO's (time between overhaul; 3-5K hours vs 1-2K) than a reciprocating engine. These are just some of the reasons that turboprops are extremely commonly used as working, commercial aircraft, hauling passengers *and* freight, whether employed by large airlines, regionals, freight co's, and/or small independent operators (think bush pilot, air taxi, etc...). Planes like the Cessna Caravan are common, although I get a hoot out of the ex-DC-3 Basler Turbo-67 Turboprops are also quite commonly used on high-end civil and business aircraft, like Pilatus and Piaggio Avanti.

      --
      "...there are some things that can beat smartness and foresight. Awkwardness and stupidity can." ~ Mark Twain
    26. Re:"Propellors"? by capnkr · · Score: 1

      You don't hang out at general aviation airports or with pilots much, then. See my comment below, and if you can at all arrange it, try going to EAA Airventure in Oshklosh, Wisconsin this August. You will learn. And have LOTS of fun.

      --
      "...there are some things that can beat smartness and foresight. Awkwardness and stupidity can." ~ Mark Twain
    27. Re:"Propellors"? by Wyatt+Earp · · Score: 1

      P-3s go around in the Arctic Ocean, even over the poles.

      http://science.dodlive.mil/2011/03/25/icebridge-almost-to-the-north-pole/

    28. Re:"Propellors"? by Wyatt+Earp · · Score: 1

      Those airports used to support MD-80s, DC-9s, B-727s, B-737s, BAe 146s, but after deregulation and the consolidation of the airlines the planes got smaller and smaller.

      From 1980 through 1995 I'd fly in and out of Pierre, Bismarck, Rapid City, Sioux Falls, or Billings out to Eugene, Portland, Spokane or Sacramento.

      I've even seen L-1011s and DC-10s in Pierre and Aberdeen way back when.

    29. Re:"Propellors"? by Wyatt+Earp · · Score: 1

      There are quite a few general aviation turboprops, even see them at Merrill Field here in Anchorage.

      Saw a Cessna 206 and Pilatus PC-6 without corporate colors June 30 flying

    30. Re:"Propellors"? by Joce640k · · Score: 1

      Yep, we get loads of commercial props around here. The Dash-8s hold about 40 passengers so they use them on routes where they can't fill Airbuses. I've been on quite a few of them, they fly pretty good and aren't noisy when you're inside them. Only problem is the top speed which is less than a jet.

      --
      No sig today...
    31. Re:"Propellors"? by Wyatt+Earp · · Score: 1

      I flew on a Dash-8 last summer from Seattle (KSEA) to Portland (KPDX) in the morning, pilot was able to take us right over Mt St. Helen's crater at about 12,000 feet, gorgeous flight.

      My cousin flies A320s and whenever I mention Dash-8s his response is "Man, I love those planes."

    32. Re:"Propellors"? by nospam007 · · Score: 1

      "oh we know what they are, but when was the last time you saw a commercial plane with them?"

      Yesterday, the day before and all the other days before.
      Luxair De Havilland Canada DHC-8-402Q Dash 8
      http://www.youtube.com/watch?v=mLOSQ6bk8cM&feature=related

    33. Re:"Propellors"? by sortius_nod · · Score: 1

      Dash-8s are everywhere here in Australia, I live under the flight path for both Tullamarine & Essendon airports here in Melbourne. Lot more prop traffic than jet traffic.

      Anything from small Pipers/Cessnas through to DC-3s and other larger prop planes go over all day.

      Add to this that, technically a turbofan (jet) engine is essentially an inside out turboprop with a higher blade density... well, the bullshit about not seeing aircraft with propellers is just someone wanting to look smart on /.

      If you actually read the full article, or even dug a bit deeper and read some of the other articles that have been going around the net, you'd realise that it's all aircraft.

    34. Re:"Propellors"? by MichaelSmith · · Score: 1

      Less common here in Australia. The price of fuel may be a factor. People who can afford their own aircraft may get a vari-eze or a sailplane. There are a few helicopters in private ownership, I suppose they count as turboprops.

    35. Re:"Propellors"? by petteyg359 · · Score: 1

      Yes, I did miss that in the first sentence, because it ain't there. If you're going to quote, then put the words in the right order.
      The article writer clearly didn't know much about aircraft when they put jetliners and propellers next to each other, so I'm ignoring those words and just going with "aircraft". As such, whether this phenomenon is caused by only jets or only props or both is entirely up to speculation, until somebody links to an article on the phenomenon written by somebody who has a clue about aircraft.

    36. Re:"Propellors"? by nuggz · · Score: 1

      The article specifies private and commercial jetlines.
      Military, prop, or turboprops don't fall into those categories.

      Though the research may be valid, the summary article is a disaster, which is becoming quite common in the media today.

      The "journalists" in science based reporting often have NO CLUE on basic scientific stats, ie odds ratios are routinely wrongly reported or commented on. But I've noticed even more basic factual errors aind inferences being drawn.
      I've pretty much given up on media reports of science, I simply find the source article if it's at all interesting.

    37. Re:"Propellors"? by HomelessInLaJolla · · Score: 1

      Meteorites cause cloud seeding. Most of them are really small and never make it to earth.

      The book of Joshua was so special because those meteorites had been moving on track for so long that they gently entered the atmosphere at about thirty miles per hour.

      --
      the NPG electrode was replaced with carbon blac
    38. Re:"Propellors"? by RoFLKOPTr · · Score: 1

      No kidding? Thems some pretty short runways. Perhaps they're only flying small planes in and out of there nowadays because "Who the hell would want to fly to Sioux Falls?"

    39. Re:"Propellors"? by RockDoctor · · Score: 1
      I use one every couple of months on average.

      That's about a 350 mile each way trip to the Shetlands for work. But there are also commercial (if subsidized) air ferries in the area that use prop craft. And in some cases, don't even have runways, but land on the beach.

      I'd be fairly surprised if there weren't other remote and/ or thinly settled regions where prop craft are still dominant.

      --
      Birds are not dinosaur descendants;birds are dinosaurs, for all useful meanings of "birds", "are" and "dinosaurs"
    40. Re:"Propellors"? by Wyatt+Earp · · Score: 1

      Sioux Falls has a pair of 8,000 foot runways, Rapid City has a single 8,000.

      Aberdeen is short (6500) so not sure why they had trijets other than a 727, but I remember an L-1011 taxing by blew the door of our Cessna 210 off the hinges once.

      Eugene Oregon is another airport that used to have more bigger jets and it's all RJ and turboprop now.

      http://en.wikipedia.org/wiki/Eugene_Airport#History

    41. Re:"Propellors"? by CheerfulMacFanboy · · Score: 1

      The article specifies private and commercial jetlines. Military, prop, or turboprops don't fall into those categories.

      Though the research may be valid, the summary article is a disaster, which is becoming quite common in the media today.

      The "journalists" in science based reporting often have NO CLUE on basic scientific stats, ie odds ratios are routinely wrongly reported or commented on. But I've noticed even more basic factual errors aind inferences being drawn. I've pretty much given up on media reports of science, I simply find the source article if it's at all interesting.

      Can't blame journalists for quoting the scientists though: http://www.sciencemag.org/content/333/6038/77

      Formation and Spread of Aircraft-Induced Holes in Clouds

      Andrew J. Heymsfield1,*, Gregory Thompson1, Hugh Morrison1, Aaron Bansemer1, Roy M. Rasmussen1, Patrick Minnis2, Zhien Wang3, Damao Zhang3

      1National Center for Atmospheric Research (NCAR), Boulder, CO 80301, USA. 2NASA Langley Research Center, Hampton, VA 23681, USA. 3Department of Atmospheric Sciences, University of Wyoming, Laramie, WY 82071, USA. *To whom correspondence should be addressed. E-mail: heyms1@ncar.ucar.edu ABSTRACT

      Hole-punch and canal clouds have been observed for more than 50 years, but the mechanisms of formation, development, duration, and thus the extent of their effect have largely been ignored. The holes have been associated with inadvertent seeding of clouds with ice particles generated by aircraft, produced through spontaneous freezing of cloud droplets in air cooled as it flows around aircraft propeller tips or over jet aircraft wings. Model simulations indicate that the growth of the ice particles can induce vertical motions with a duration of 1 hour or more, a process that expands the holes and canals in clouds. Global effects are minimal, but regionally near major airports, additional precipitation can be induced.

      --
      Fandroids hate facts.
    42. Re:"Propellors"? by Travelsonic · · Score: 1

      DeHavilland / Bombardier Dash-8
      Avion de Transport Regional 42, 72
      Saab 340, 2000
      Beech 1900D
      Shorts 330, 360 [I remember when American Eagle flew these]
      Dornier 228
      Fairchild Metro
      BAe Jetstream 31s, 41s
      DC-3 [A couple of tourist companies use them, I think 1 in Canada, use a couple of DC-3s still]
      etc etc, hard to believe that people don't know that turboprops were, and are still [relatively] widely used.

      --
      If you believe in privacy, and believe you have "nothing to hide" at the same time, you're a goddammed idiot
  2. Not new news by Afforess · · Score: 5, Informative

    Meteorologists have known about this for some time. They tend to form what is known as "Hole Punch" clouds.

    Examples: http://bit.ly/lAxNQO

    --
    If our elected representatives no longer represent us, do we still live in a Democracy?
    1. Re:Not new news by Anonymous Coward · · Score: 0

      Wow. That was actually what it was billed as! No goatse! I'm astonished.

    2. Re:Not new news by MobileTatsu-NJG · · Score: 1

      I can't believe I actually fell for clicking on this... ... good thing it's legit.

      --

      "I like to lick butts!" by MobileTatsu-NJG (#32700246) (Score:5, Informative)

    3. Re:Not new news by Anonymous Coward · · Score: 0

      Obviously its caused by HAARP and airplanes are being scapegoated.

    4. Re:Not new news by Anonymous Coward · · Score: 0

      The bit.ly link above redirects to a Google search for "hole punch cloud". I guess the OP was too bewildered by HTML to link to a URL with ampersands in it.

    5. Re:Not new news by Anonymous Coward · · Score: 0

      Unrelated, but a general suggestion: don't use link shorteners unless the service requires it (e.g. Twitter). They conceal the URL, and people tend to assume that they're being rickrolled or goatse'd that way (it is, in fact, pretty common on /. to have a shortened URL link to goatse - probably every third link or so), and will treat you accordingly, especially if they have mod points.

  3. How is this news by Anonymous Coward · · Score: 5, Informative

    I mean seriously, this has been known for decades. There was even a study that looked at the 9-11 shutdown of air-traffic affected climate.

    This has been known for a long time.

    1. Re:How is this news by ChrisCampbell47 · · Score: 1

      Precisely. Someone mod parent up please.

    2. Re:How is this news by Anonymous Coward · · Score: 0

      Yes - 9/11 ended the experiment of jet travel for 3 days and this is a known result - I remember it being discussed on day 2 of the shutdown.

    3. Re:How is this news by MichaelSmith · · Score: 1

      I have only flown across the US once (I am an Australian) but I was surprised to see how many contrails we crossed going from New York to Los Angeles. It may be the distributed nature of the US population. Aircraft go all over the place and cross each others paths with surprising frequency.

    4. Re:How is this news by Anonymous Coward · · Score: 0

      Check http://radar.weather.gov/Conus/full_loop.php in the evening. You can usually spot westbound radar returns that might be correlated with air traffic.

    5. Re:How is this news by excelsior_gr · · Score: 2

      I agree with what you said, I just want to do some CNN-bashing:
      Those damn journalists were trying to be sensational again by saying that the air traffic affects the *climate* while it is obvious that it just affects the *weather*. If the air traffic disappears the *weather* will just roll back to its usual behavior that is dictated by the *climate*. Of course, I am only taking about the condensation wisps that are referred to in the article, not the aircraft emissions, that do have an effect on the *climate*.

      But I guess the word weather is out of fashion, and climate sounds so much better... Damned journalists, I hate you guys...

    6. Re:How is this news by grimmjeeper · · Score: 1

      You're just being a trouble maker. They know what's best for us and our climate AND weather. Just do what they say without questioning it and everything will be fine. Here, have some Kool-Aid

    7. Re:How is this news by isorox · · Score: 1

      I agree with what you said, I just want to do some CNN-bashing:
      Those damn journalists were trying to be sensational again by saying that the air traffic affects the *climate* while it is obvious that it just affects the *weather*. If the air traffic disappears the *weather* will just roll back to its usual behavior that is dictated by the *climate*. Of course, I am only taking about the condensation wisps that are referred to in the article, not the aircraft emissions, that do have an effect on the *climate*.

      But I guess the word weather is out of fashion, and climate sounds so much better... Damned journalists, I hate you guys...

      It's a problem with journalists. "Climate" sounds sexier than "Weather" just like "Deficit" is sexier than "Debt". These terms start off being correctly used, but soon fall away and reports gets "sexed up"

    8. Re:How is this news by Lost+Race · · Score: 1

      See also NOVA: Dimming the Sun, which discusses, among other things, the effect of the September 2001 air traffic shutdown on weather (not climate).

    9. Re:How is this news by Anonymous Coward · · Score: 0

      9/11 study: contrails affect the daily variation in temperature.
      New study: aircraft seed clouds they fly through and can increase precipitation around airports.

      Those are actually different things.

    10. Re:How is this news by Misagon · · Score: 1

      If planes do this all the time, 24/7, 7 days a week, all year around, then what is the difference? It is precisely as if planes changed the climate.

      There is a theory that seeding from airplanes was the main cause of the drought in Etiopia back in the 1980s.
      I'm not a tin-foil-hat guy, but sometimes weird theories are proven right.

      --
      "We mustn't be caught by surprise by our own advancing technology" -- Aldous Huxley
    11. Re:How is this news by excelsior_gr · · Score: 1

      You have a point, but the difference is the time scale for recovery. As reported in the CNN article, 3 days of grounding were enough to notice a difference. If something changes in the climate it will take much longer than 3 days for things to roll back to their previous state (if ever).

    12. Re:How is this news by camperdave · · Score: 1

      We've had airplanes buzzing through the skies for a century. Over all, they could be a climate altering force.

      --
      When our name is on the back of your car, we're behind you all the way!
    13. Re:How is this news by JohnVKaravitis · · Score: 1

      John V. Karavitis Agreed, this has been known for a long time. But the study/report that I remember reading was that researchers looked at the weather on the East coast, and looked at the incidence of rain during the week versus the weekend. It seems as though the heavy air traffic Monday through Friday brings about more rain on the weekends exactly due to this phenomenon. John V. Karavitis

  4. That's the bees knees, Professor! by blair1q · · Score: 0, Offtopic

    Next week when we come by for Slash Dot Mystery Time, can we talk about how steam valves and clock gears work?

    That would also be a slide in the ice-house.

  5. arg by Osgeld · · Score: 1

    Please quit wasting our tax money, seriously the people who did this study should have their funding removed as all they have done is have a "no shit mr 1934" moment over technology that is darn near extinct

    1. Re:arg by MightyMait · · Score: 1

      Don't jet engines have a propeller-like thing called a turbine? Wouldn't they have a similar effect?

      --
      Nothing interesting to say...MUST...NOT...REPLY...ohtheheckwithit.
    2. Re:arg by Osgeld · · Score: 0

      Similar as in they are objects that spin, but otherwise no, not really

      hell do us a favour and go stand behind a jet engine and let us know how cool the air feels to you

    3. Re:arg by Beelzebud · · Score: 0

      Oh shut up about your tax money. Your share of their funds is probably less than 1 dollar per year, for valuable research.

    4. Re:arg by MacTO · · Score: 1

      While the majority of passengers use jets, it wouldn't surprise me if more than half of the planes in the air use that "darn near extinct" technology. You just won't see many of them at a typical international airport for reasons of economy.

      (Where are they used: flights that serve smaller communities, short haul flights, transporting goods or doing exploration in remote areas, etc..)

    5. Re:arg by dave420 · · Score: 2

      Turboprop engines are used all over the world, in very large numbers. The US military alone has over 2,421 active aircraft with propellers (not including helicopters, before you ask).

    6. Re:arg by MightyMait · · Score: 1

      Well, exqueeze me!! How about the wings? Didn't TFA mention something about wings? Don't *they* have a cooling effect?

      --
      Nothing interesting to say...MUST...NOT...REPLY...ohtheheckwithit.
    7. Re:arg by Osgeld · · Score: 1

      see how much better that sounds over "propeller jetliner"

    8. Re:arg by dave420 · · Score: 1

      What are you talking about? You claimed propellers are nearly extinct, but clearly they are not.

    9. Re:arg by MacTO · · Score: 1

      Very few people will even understand the word "turboprop", so writers end up using terms that their readers will understand.

    10. Re:arg by Anonymous Coward · · Score: 0

      RTFA ... they are talking about jets with propellors. Gave me a brief chuckle, then ignore whatever ignorant ramble that might be connected to it.

    11. Re:arg by mcgrew · · Score: 4, Informative

      Oh, ferkrissakes, I came here to use up my last two mod points and almost every comment is ignorant, so I'm going to just make one comment and watch a movie and use those two points in the morning.

      I know it's not usual for anybody to RTFA and instead just jump to conclusions thinking you know everything without having a clue, so I'm going to clue a few of you guys. This is not about contrails. Of course contrails have been known about forever. I didn't read this particular FA but I saw another FA about this earlier today, and it was damned interesting.

      If it was about contrails, most of you guys would still be wrong. Contrails aren't caused by the turbines, they're caused by the air passing the wingtips of the aircraft. If you want to learn more, there's wikipedia for that.

      This is about circular holes in clouds, It's about the exact OPPOSITE if contrails. The cause of contrails is well known, the cause of this particular phenomena isn't known. I find it hilarious that you guys think you know more about physics than folks who've been studying physics all their lives.

      I'm not a physicist or meteorologist, but at least I know enough to know the limits of my own ignorance, so I READ. Voraciously. The more I read the more I learn, the more I learn the more I understand how ignorant I am. You guys might try reading once in a while. You're ignorant -- we're all ignorant. A physicist doesn't know shit about cosmology, and a cosmologist doesn't know shit about paleontology.

      The man who thinks he knows everything cannot learn. Thus endeth the lesson, grasshopper.

    12. Re:arg by AnObfuscator · · Score: 4, Informative

      If it was about contrails, most of you guys would still be wrong. Contrails aren't caused by the turbines, they're caused by the air passing the wingtips of the aircraft. If you want to learn more, there's wikipedia for that.

      Ironic, considering the tone of your post, but I actually *did* look up (and read) the contrails article on Wikipedia, and you are in fact very wrong. http://en.wikipedia.org/w/index.php?title=Contrail&oldid=436631379

      Contrails (play /kntrelz/; short for "condensation trails") or vapour trails are artificial clouds that are the visible trails of condensed water vapour made by the exhaust of aircraft engines. As the hot exhaust gases cool in the surrounding air they may precipitate a cloud of microscopic water droplets. If the air is cold enough, this trail will be comprised of tiny ice crystals.[1]

      The wingtip vortices which trail from the wingtips and wing flaps of aircraft are sometimes partly visible due to condensation in the cores of the vortices. Each vortex is a mass of spinning air and the air pressure at the centre of the vortex is very low. These wingtip vortices are not the same as contrails.

      --
      multifariam.net -- yet another nerd blog
    13. Re:arg by Jeff+DeMaagd · · Score: 1

      Which is kind of silly, given that the internet is right there to look things up, turboprop is very well defined. Whether turboprop craft are jetliners appears to be ambiguous. It looks like probably not, but I have nothing to be certain.

    14. Re:arg by Greymoon · · Score: 1

      Thank you for reminding me you are ignorant and apparently fail at taking your own advice. Try being more pretentious next time, the asshole in you wants to be free. ... as in speech.

    15. Re:arg by tftp · · Score: 1

      Didn't TFA mention something about wings? Don't *they* have a cooling effect?

      A thing that burns megajoules can't have a cooling effect overall. It will have heating effect, to the exact amount of energy expended.

      All the fuel that an airplane uses up during the flight heats the atmosphere, unless there is a difference in elevation between the origin and the destination airports.

    16. Re:arg by excelsior_gr · · Score: 1

      And you missed the point, in which the GP was saying that the article has nothing to do with contrails, it is about a whole different phenomenon altogether.

      You shall be now asked to leave the shaolin temple, and leave your geek card at the exit...

    17. Re:arg by michelcolman · · Score: 1

      And you missed the point, in which the GP was pointing out the exaggerated degree of pretention in the GGP post. Somebody accusing others of making wrong statements and telling them they should read more, in a very condescending tone, should take care not to make mistakes against the very reading material he was refering to (wikipedia, "contrail"). Of course the part about cloud seeding being a different phenomenon was correct, but that does not mean you can't react on any other part of his post.

    18. Re:arg by Aighearach · · Score: 1

      A thing that burns megajoules can't have a cooling effect overall. It will have heating effect, to the exact amount of energy expended.

      The problem with absolute statements is that, even if you mostly knew what you were talking about, the factors you didn't consider will destroy you. If you asked the same thing as a question, as befitting the amount of thought that went into it, then it might have even been a good question. As a bold statement of fact, it leaves a lot to be desired. Mostly, the facty bits.

      It doesn't matter that the 2nd Law exists. Nobody said it was being violated. You can easily burn a bunch of fuel, create a huge amount of heat, and also create a bunch of cooling. We don't have just one particle in the Universe to heat or cool, we have lots of them. And they're in different places. So you can easy burn a very hot exhaust trail surrounded by a much larger volume of slightly cooled air.

      The second law preserved, the rain indeed may make it to the ground.

    19. Re:arg by gl4ss · · Score: 1

      it's important what's revolving the propeller. from sound, fuel and efficiency standpoints. but it's not silly that writers end up using terms their readers will understand.

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      world was created 5 seconds before this post as it is.
  6. nope by localoptimum · · Score: 1

    Jetliners do not have propellers. ;)

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    1. Re:nope by blair1q · · Score: 0

      They sort of do, in the form of turbofans in their ducted engines.

      However, these do not cause cooling. They cause enormous heating. But they cause turbulence in the air behind the plane. This turbulence may constitute enough of a difference in density and pressure to cause water vapor in the air to condense into mist, which is called a contrail.

      Airplanes also have wings and control surfaces. Air flowing over these creates vortices. These vortices can constitute enough of a difference in density and pressure to cause water vapor in the air to condense into mist, which is also called a contrail.

      And just wait until Mr. Wizard and his government grant get ahold of the idea of the speed of sound...

    2. Re:nope by Loconut1389 · · Score: 1

      and turboprops are both a jet and a propeller

  7. Mystery Fog formed before airplan crash near Katyn by PythonM · · Score: 1

    Before the 2010 airplane crash that killed Polish president several top generals and tens of top politician, a mystery fog appeared. Could the fog be intentionally formed the Russian airplane that was flying around that place earlier?

  8. Re:And this is nothing compared to.... by blair1q · · Score: 2, Insightful

    Contrails are real. Jet exhaust contains chemicals. Those chemicals are pollutants. They can cause respiratory problems and maybe birth defects. But they can't cause mind control, other than the ability to twist some people into a knot when their brain power meets their ignorance in a paranoid delusion and motivates them to make fools of themselves and enemies of everyone sane.

  9. cue the chemtrail jokes... by lemur3 · · Score: 0

    3 2. 1......

    surely someone out there will be using this as more "proof"

  10. Spammy Inhabitat link instead of Science Daily. by couchslug · · Score: 5, Informative

    "commercial and private jetliners" "When an airplane flies through a cloud, its propellers"

    The number of jetliners with "propellers" is mighty fucking few, though not zero.

    Linking to the PARENT Science Daily piece

    http://www.sciencedaily.com/releases/2011/06/110630142835.htm

    instead of the pointless Inhabitat bullshit summary would have been nice. There is NO excuse for the Inhabitat link other than SPAM.

    AC is anonymous because he/she/it wants page hits for Inhabitat.
    Now I know not to visit Inhabitat again. Fuck you too and thanks for nothing.

    http://www.sciencedaily.com/releases/2011/06/110630142835.htm

    --
    "This post is an artistic work of fiction and falsehood. Only a fool would take anything posted here as fact."
    1. Re:Spammy Inhabitat link instead of Science Daily. by Anonymous Coward · · Score: 0

      if i had points, i'd mod you up. I can't stand inhabitat.

    2. Re:Spammy Inhabitat link instead of Science Daily. by sphealey · · Score: 3, Informative

      > The number of jetliners with "propellers" is mighty fucking few, though not zero.

      The number of airliners with gas turbine engines that turn propellers is in fact quite large.

      The bypass fan of a high-bypass turbofan engine is essentially a propeller as well, although ducted.

      So that leaves us with the various 707s, DC-8s, and 727s and their military equivalents flying around out there with straight turbojet engines having no fan-push component, which is not all that many in 2011.

      sPh

      In any case the results of this study should have been blindingly obvious to anyone living in North America during the no-fly week of 9/11 - 9/18.

    3. Re:Spammy Inhabitat link instead of Science Daily. by couchslug · · Score: 1

      Technically quite correct, but few readers not greatly interested in aircraft will get those differences between a conventional external "prop", turbojets, and turbofans. I'm prior avionics/engines/crew dog (cross-training was fun) but try to keep it simple for layfolk.

      These are kinda neat:

      http://www.popsci.com/technology/article/2010-03/naked-engine-cleaner-flights

      --
      "This post is an artistic work of fiction and falsehood. Only a fool would take anything posted here as fact."
    4. Re:Spammy Inhabitat link instead of Science Daily. by FunkSoulBrother · · Score: 1

      I've never been to inhabitat but holy shit did it want to run a lot of javascript. Like 15 different domains.

    5. Re:Spammy Inhabitat link instead of Science Daily. by Wyatt+Earp · · Score: 1

      Turboprops make up for 45% of passengers carried by commercial aircraft in the US and Canada.

    6. Re:Spammy Inhabitat link instead of Science Daily. by don_weber · · Score: 1

      Thanks for the article, I was curious about other fluid effects beyond the propeller argument of the inhabitat article.

    7. Re:Spammy Inhabitat link instead of Science Daily. by Anonymous Coward · · Score: 0

      Yes, because there are so many which fly by electromagnetodynamic induction.

    8. Re:Spammy Inhabitat link instead of Science Daily. by Anonymous Coward · · Score: 0

      I'm prior avionics/engines/crew dog (cross-training was fun) but try to keep it simple for layfolk.

      You poor little brain damanged monkey. (I'm avionics. Yes we are smarter than everyone else.)

      The plus side with working with crew chiefs is you'll feel like a genius no matter how stupid you are.

    9. Re:Spammy Inhabitat link instead of Science Daily. by couchslug · · Score: 1

      (I'm avionics. Yes we are smarter than everyone else.)

      Teh smartness is portable. Always be ready to exploit the arcane knowledge of swaptronics...

      Crosstraining out of Comm/Nav beat the fuck out of staying on Moody AFB in the 1980s! Job was fun (F-4s) but location was a ghastly backwater. They even warned us during inprocessing that Lowndes county had the highest VD rate in Georgia.

      Of course I didn't voluntarily crosstrain to nosepicker. I went Engines, then a few years later we were merged with APG by Rivet Workforce. Later, they "un-merged" and ended up with a bunch of noob Engine troops and a bunch of the sharper crew chiefs who were better Engine troops but weren't allowed to switch even if they wanted to.

      Avionics is not a fast route to rank, but it beats working. If you can sneak into Gold Flag that's magnificent. I was too senior to get in when it was started, though with multiple AFSCs I was plenty qualified.

      --
      "This post is an artistic work of fiction and falsehood. Only a fool would take anything posted here as fact."
    10. Re:Spammy Inhabitat link instead of Science Daily. by Anonymous Coward · · Score: 0

      Very nicely put and well reasoned. A breath of fresh air!

  11. Re:And this is nothing compared to.... by dominious · · Score: 1

    weather its real or not.... its not only real but mentioned in weather modification and other paperwork from the US government.

    I agree that whether modification its real weather people agree with it or not.

  12. There is no going back by Anonymous Coward · · Score: 0

    Could we possibly not appropriate these results into the militant anti-human greeny litany and then beat ourselves over the head with it? It's such a drag.

    This is a human planet. For whatever reason the universe permitted the emergence of a species of engineers. Barring our extinction the planet will never again approach 'natural.' From radioisotope traces to atmospheric disruption the effect of our existence can not be prevented, removed or even hidden.

    Contemporary Western culture is presently indulging a crippling self-loathing as it attempts to come to terms with this reality. Yurts aren't an option. Stop polluting your mind with that nonsense.

    Fortunately cultures evolve, sometimes rapidly. A day will come when we cease to relegate all analysis of new knowledge of our world and everything in it exclusively to anti-humanists.

    1. Re:There is no going back by wierd_w · · Score: 4, Insightful

      Conversely, there are fundemental limitations of what this muddy dirtball can handle, and limits to what technology can accomplish.

      The ideal course is to understand both, and proceed accordingly.

      To do otherwise is to invite disaster.

    2. Re:There is no going back by couchslug · · Score: 1

      Clearly, we must conquer more muddy dirtballs!

      --
      "This post is an artistic work of fiction and falsehood. Only a fool would take anything posted here as fact."
  13. Re:Mystery Fog formed before airplan crash near Ka by Wyatt+Earp · · Score: 1

    Or it was just a fog.

    http://en.wikipedia.org/wiki/Fog#Characteristics

    Fog forms when the difference between temperature and dew point is generally less than 2.5 C or 4 F

    "Fog can form suddenly, and can dissipate just as rapidly, depending what side of the dew point the temperature is on. This phenomenon is known as flash fog."

  14. Where have I read this before? by JayTech · · Score: 3, Funny

    I remember reading this at a popular news site over a year ago. Where could it have been? Oh, wait, here it is! http://science.slashdot.org/story/10/06/15/2020240/Airplanes-Unexpectedly-Modify-Weather

    1. Re:Where have I read this before? by gl4ss · · Score: 1

      classic! slashdot has turned into one of those classic popular science mags which re-print same future news every few years.

      --
      world was created 5 seconds before this post as it is.
  15. Also known as "contrails" by Geoffrey.landis · · Score: 0

    Meteorologists have known about this for some time.

    The common term for it is "contrails."

    Yes, it's well known that contrails sometimes to grow into cloud cover. (High altitude thin clouds, not puffy cumulus ones). This is not news.

    --
    http://www.geoffreylandis.com
    1. Re:Also known as "contrails" by sjwt · · Score: 2

      I do believe you did not look at the photos, so from another website, here is some text for you to read.

      As a note, because of what ever technical reason stooped you looking a the lint, these clouds can and do look at times look like massive eyes or holes in the clouds, nothing at all like contrails, and in some cases can look like a massive gouge taken out of the clouds, kinda like a revers contrail.

      http://www.weatherthings.com/HolePunch.html

      "A “Hole Punch” cloud is a non-technical name given to a cloud formed from an aircraft dissipation hole or trail. They are also called "Punch Hole" clouds. Rather than extending as a line, Hole Punch clouds appear as a circular or oval hole in a deck or thin layer of supercooled water clouds. They are not uncommon where jet flight paths intersect altocumulus layers. What is uncommon is when they form in a perfect circle that persists for a length of time to be widely observed."

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  16. Re:And this is nothing compared to.... by dave420 · · Score: 2

    Chemtrails = bullshit. Abject, horrific bullshit, spread by idiots who don't have a fucking clue about meteorology, basic physics, and more importantly that a few documents mentioning cloud seeding do not instantly mean that even one single witnessed contrail is anything other than a contrail. Critical thinking - it works, bitches.

  17. Why has it taken so long for anyone to think... by Red_Chaos1 · · Score: 1

    ...of this? I used to wonder about this as a kid at least 15-ish years ago. Even without the stuff about propellers and pressure and such, it seemed obvious that a plane flying through a cloud would set off a reaction from the larger water drops formed from the condensation buildup on the body of it. Said larger drops fall off and through the cloud further causing a reaction.

    Of course I never studied it or took it further, so it is quite possible I am wrong, but the point stands that I thought of it long ago, why is it only news now? Surely I am not the only one to think of it?

    1. Re:Why has it taken so long for anyone to think... by AHuxley · · Score: 1

      The Airline industry was subsidised, nationalistic and futuristic. Nothing was going to be allowed to get in the way of its expansion.
      If decades of “tombstone technology" (when there are enough tombstones the technology gets fixed) was allowed to slip whats a bit of weather changing :)

      --
      Domestic spying is now "Benign Information Gathering"
  18. opens the door for lawsuits? by Joe_Dragon · · Score: 1

    Just saying saying that some can say the plane cloud seeding spawned a tornado that killed some one / damaged your car / house / other stuff.

  19. Chem-trails and conspiracies by Missing_dc · · Score: 0

    This almost sounds like a lead in for "scientific excuses" for chemtrails.

    Oh, look, its the turbo-props causing the lasting contrail, those jets are not equipped with special sprayers at all.

    --
    How amazed would you be to suddenly find that you just forgot what I wrote and you needed to reread my post.... again.
    1. Re:Chem-trails and conspiracies by Akima · · Score: 1

      From my research contrails are a completely normal part of air flight. My Grandpa was flying commercial passenger planes long ago. I asked him about it and he told me... "All engines emit water vapour, usually invisible. Given the right atmospheric conditions the vapour will condense into cloud. In the same way that normal cloud appears in many different forms, so contrails can be persistent, non-persistent, thick or thin and so can be short, long, narrow or wide and can remain as cloud similar to the Cirrus that you see at high level on a sunny day. Contrails are usually of ice and at high altitude. I must have released many 1000s of tons of water which became ice and cloud. So far no lumps have fallen on my head!"

      I've also found plenty of evidence that chemtrails have been created in many different countries.
      Here's a Germany news report which describes how the German Federal Army have been creating chemtrails: http://www.youtube.com/watch?v=51FcITBszj8
      There are subtitles in the video.
      I don't think this is strictly chemtrails, but the Russians perform cloud seeding by adding silver iodide, dry ice and liquid nitrogen to the clouds to cause immediate precipitation: http://englishrussia.com/2011/05/18/manipulating-the-weather/

      So far I have been unable to figure out if there is a way of visually distinguishing the difference between chemtrails and contrails.

      Really my point is... when you see artificial clouds in the sky it /might/ be a chemtrail, but it is much more likely to be a completely normal contrail.

    2. Re:Chem-trails and conspiracies by dave420 · · Score: 1

      No, it's basic fucking physics that causes lasting contrails. Basic. Fucking. Physics. Using high-altitude jets to disperse chemicals over populations is about the worst way you can do it - anything jettisoned from the plane would land thousands of miles away from where the plane was, and in an entirely unpredictable direction. The whole "idea" of chemtrails is born from abject ignorance coupled with paranoid hubris. It's despicable.

  20. Re:And this is nothing compared to.... by drinkypoo · · Score: 1

    Abject, horrific bullshit, spread by idiots who don't have a fucking clue about meteorology, basic physics, and more importantly that a few documents mentioning cloud seeding do not instantly mean that even one single witnessed contrail is anything other than a contrail.

    Snicker snort. I bet you're attacking the non-arguments from the fringe of the fringe. It's a long jump from reality, where the military continually talks about ongoing plans and goals to "own the weather" with new papers published talking about how it can be done regularly, to "a few documents mentioning cloud seeding". I'm sure you think this is totally normal for example.

    Critical thinking - it works, bitches.

    though not for you.

    --
    "You're right," Fisheye says. "I should have set it on 'whip' or 'chop.'"
  21. Sure... by gavron · · Score: 1

    Yeah, those private jets over the poles, why DO THEY DO IT??? Stop private planes flying over the poles. All zero of them.

    And as others have mentioned, yeah "propellers" on the "jetliners". LOL! Sure.

    I would rather blame rich guys with long noses who were originally made of wood.
    Sure, it's Pinnochio. Just as real.

    Looks like Slashdot let another potsmoker start a thread.

    E

    1. Re:Sure... by amorsen · · Score: 1

      Looks like Slashdot let another potsmoker start a thread.

      It looks more like "let another potsmoker comment on the article" to me. Planes fly quite far north when they fly e.g. between Europe and North America, and practically all jet planes have fans -- propellers with many blades.

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    2. Re:Sure... by tomtomtom · · Score: 1

      Yeah, those private jets over the poles, why DO THEY DO IT??? Stop private planes flying over the poles. All zero of them.

      Actually, since the end of the cold war (and with the development of aircraft which can do VERY long non-stops like the A340) several commercial passenger flights operate every day which directly cross the North Pole. Particularly these are the very long East Coast US to Asia routes, eg EWR-HKG, JFK-HKG, JFK-PEK, ORD-PEK etc. In the opposite direction it's not usually done as it's more efficient to use the jet stream over the North Pacific.

    3. Re:Sure... by Anonymous Coward · · Score: 0

      uh...yeah actually...alot of planes fly over the poles. It's faster that way between Europe and the US. Private, public, and military. We fly (military) several times a month over the poles from our base. My last two commercial flights back to the States were over the n. pole.

      Bypass fan jet motors, used by 99% of the commercial jets in the US actually use propellers (fans) that happen to have the blades on the inside of the motor rather than the outside. They are quieter and are more efficient though much larger than traditional jet motors.

      The article is acurate, though the material is very dated, by something like 20 years.

    4. Re:Sure... by Misagon · · Score: 1

      Most routes between Europe and northern Asia (Japan, Korea etc.) go over the North Pole. Many make a short stop in Alaska. The routes may look weird on a flat map, but not so much on a globe.

      --
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  22. time lapse by Evoluder · · Score: 1

    Oddly enough I made this time lapse with my phone the other day, see jet fly through on the left. http://youtu.be/2VBx1RHFM3c

  23. Explain California droughts then by keith_nt4 · · Score: 1

    The question i always have, and never get the answer to, when I see articles about these "studies" is: explain droughts in California over the past 30 years. California has a whole lot of air traffic all over the state and yet it goes multiple years on end with very little rain. If this happens so consistently to conclude there's a correlation why does California have droughts...like ever...?

    --
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    1. Re:Explain California droughts then by Anonymous Coward · · Score: 0

      Planes don't put moisture in the air, duh.

      Anyway, as a right libertarian, I understand that these findings prove that Global Warming is a myth, and Al Gore is stupid. It's a scientific fact!

    2. Re:Explain California droughts then by maxume · · Score: 1

      The planes interact with water that is present in the atmosphere. If there is not much water in the air a plane flies through, it won't cause rain.

      --
      Nerd rage is the funniest rage.
    3. Re:Explain California droughts then by Anonymous Coward · · Score: 0

      Terrible water management, not so much the lack of water. Also combine the fact that northern california supplies water to a DESERT, with lush lawn, pools, etc... yeah.

    4. Re:Explain California droughts then by Anonymous Coward · · Score: 0

      The most obvious answer I pulled out of my backside would be to say that there aren't enough clouds to be seeded in the first place, or the ones that *are* there aren't close enough to the "edge" to be triggered by this reaction?!

    5. Re:Explain California droughts then by ponchietto · · Score: 1

      Clouds != Rain I have never seen rain from Cirrus (high clouds > 10000 ft (3000m), probably these clouds are similar. (they form in the same place to start with).

    6. Re:Explain California droughts then by RobertLTux · · Score: 1

      or to rephrase things a bit its like in a game where you roll 5d20 (rolling for 60) to cause an event if you get a bonus of 2 points for every plane in the cloud its going to take a lot if your actual roll is 20 (and its worse if you have say a penalty of 12 to fight)

      so if you have an area where there are mostly clouds with a minimum of water (barely enough to be called a cloud at all) then yes it is possible that Cali could have a bunch of flights and still have a drought (plus Cali has a whole lot of hexes on its map).

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    7. Re:Explain California droughts then by Anonymous Coward · · Score: 0

      Aircraft contrails often lead to cloud buildup, but not rain necessarily.

      You can have cloud and no rain: I've lived in places like Australia where it has been cloudy for months on end while suffering the worst droughts in many years.

  24. Re:Mystery Fog formed before airplan crash near Ka by amorsen · · Score: 1

    Mystery? What exactly was mysterious about it? Are all fogs mystery fogs?

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  25. Re:And this is nothing compared to.... by Lehk228 · · Score: 1

    are you seriously supporting chemtrail bullshit?

    --
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  26. Re:And this is nothing compared to.... by dave420 · · Score: 2

    Yes, aircraft changing course is totally normal. Heck, large circles are even perfectly normal. Can you provide evidence as to how they are not normal? That's how critical thinking works. Apparently you don't understand that, which is why you believe this bullshit.

  27. Not contrails by michelcolman · · Score: 1

    This is actually not about contrails, but quite the opposite. A contrail is a cloud created by the passage of an airplane (due to the vapor from the engine or simply the dynamic effect of stirring up oversaturated air). This study is about airplanes flying through clouds and causing those clouds to start raining. In a way, they are erasing clouds ("punching holes" in them)

  28. Y'all be going on vacation? Beep Delta. by Vandil+X · · Score: 1

    We run up into the sky so deep, it be crying. Yeah, you thought that was rain. http://www.youtube.com/watch?v=IU7VTJA0dNo

    --
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  29. Re:And this is nothing compared to.... by drinkypoo · · Score: 1

    Can you provide evidence as to how they are not normal?

    Aircraft don't normally change direction over my house, and they double-extra don't normally come into the region from multiple different directions and then change direction as you can clearly see in-frame. After this picture was taken the trails spread out to cover the sky from horizon to horizon, even when I stand on the rise on my property from which I have a fairly amazing view.

    --
    "You're right," Fisheye says. "I should have set it on 'whip' or 'chop.'"
  30. Interestingly enough by shoehornjob · · Score: 1

    FTFA "When an airplane flies through a cloud, its propellers cause the expansion and cooling of the air behind them which can cause water droplets to spontaneously cool and crystals to form." However the picture shows a jet aircraft which if very different from a plane that has a standard propeller on the front. If the study took into account the differences between the two types of aircraft I'm reasonably sure that the effect would be different. Ergo there is a significant difference between a standard prop an a jet engine and the author of the article should have noted that. And will these scientists stop "rediscovering" that which has been known for years.

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  31. correlates w/ noctilucent clouds ? by cathector · · Score: 1

    interesting. noctilucent clouds have also been on the rise during the period of modern aircraft, and are also seen primarily towards polar latitudes.

  32. Re:And this is nothing compared to.... by dave420 · · Score: 1

    So basically you don't have evidence, you just have your opinion of what's normal and what isn't, all of which is based on your own personal experience and nothing more.

    Planes change course for many different reasons. Engine difficulty, being re-routed, problems on board, weather patterns changing, or even military action, just to name a few. You have to show how none of those was responsible for the change in course of the plane that caused that contrail, before you can start attributing weird and exotic explanations for an otherwise mundane phenomenon.

    Trails can linger for hours/days, and spread vast distances, simply due to the nature of what a contrail is. Heck, it's even covered in the article.

    So, to sum up:

    You don't know about planes or contrails, so therefore they must be some massive, ridiculously complicated and even more ridiculously pointless conspiracy that there is no evidence of.

    Idiot.

  33. Why don't you show which site you link to? by Anonymous Coward · · Score: 0

    I'm in the habit of inspecting the URL shown in the status bar before clicking on a hyperlink. Do you have any particular reason to hide this useful information?

  34. Contrails, over states, decrease crop yields by Anonymous Coward · · Score: 0

    Contrails, which are extensive over some states such as Oregon where they can spread to cover the sky all day, decrease crop yields, because crop yields respond to the amount of solar energy received. You can see the response of crop yields to solar energy if you plant you garden against shade: in the shaded garden you will see noticeably less growth and productivity. Aviation does reduce farm productivity as a result.

  35. Drought induction downwind ; cooling. by RockDoctor · · Score: 1
    Several issues over this.

    There's only one comment on the source website (and I'm not minded to sign up to the site to comment there) :
    lazyreader says:
    Would that be so much of a problem in drought prone areas?

    Which is a perfectly good question, but begs the follow-up question of "what about the marginal or drought-prone areas downwind of your seeded area, where your seeding accidentally or deliberately wrings the water out of the clouds, so these areas get tipped into full-blown drought?"

    I'm also somewhat minded of the climate research done in mid-September 2011, which showed that the US is probably cooled by around 1deg C (1 K) by it's normal shroud of contrails. (Travis, D.J.; A. Carleton and R.G. Lauritsen (8 2002). "Contrails reduce daily temperature range". Nature 418 (6898): 601. doi:10.1038/418601a. PMID 12167846.)

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  36. two documentaries on subject by Anonymous Coward · · Score: 0

    "The cloud mystery" and "global dimming" paint a good picture of whats going on.

  37. Re:And this is nothing compared to.... by threeseas · · Score: 0

    besides these pictures I took https://www.facebook.com/media/set/?set=a.169900799714796.30084.100000846306529 I then drove home from work where still watching planes in the sky saw two planes one off in the distance to my left flying west and one to my right at a distance flying south. Both started dumping at the same time. two of the picture I took show both contrail and chemtrails, where even one picture shows a chemtrail going south and a con trail paralleling it. The comments on those photos tells me that they started dumping on the east coast that morning and by afternoon they were passing over Atlanta. I was skeptical of chemtrails... until that day and have since noticed that when ever chemtrails are done clouds develop from the chemtrails and rain follow. Cloud seeding is nothing new but Vitamin D deficiency is becoming more wide spread as these chemtrails are causing a sun blocking effect. We get Vitamin D from the Sun. Now if this were contrail seeding of clouds then the Vitamin D issue would not be. But given the chemicals being dumped, there is intent to block the suns rays. Global warming may be a bunch of hot air but solar storms are happening now and will get worse and.this is information even NASA has been releasing. Aluminum oxide is not only able to reflect some sun rays but also is a good conductor of electricity and as some will say, there has been some strange weather and some serious lightening. Add in pole shifting (the sun recently happened and earth going through it...) I've been on slashdot for years and I'm fully aware of the erroneous bias which is so often expressed via scores and comments. So I'm not at all surprised.

  38. Re:And this is nothing compared to.... by dave420 · · Score: 1

    Thanks for proving my point. You clearly don't understand how contrails are formed. You are ignorant, but you somehow can't see it. You fucking idiot.