1. alan white

    alan white New Member

    Has this been debunked? It looks to me like chemtrail believers are taking Dr. Kirby's comments out of context and using what he said to "prove" their beliefs. http://www.veteranstoday.com/2014/12/27/climate-scientist-blows-whistle-on-aerosol-dumps-chemtrails/

    "these are clouds seeded by jets dumping aerosols into the upper atmosphere". Its from Dr. Kirkby’s 2009 CERN presentation about climate change and in this presentation he talks about contrails effecting climate by creating thin cloud covering. I've only heard excerpts of this presentation. So I'm not exactly sure how it was taken out of context to be honest. When I have a chance I'll listen to the whole presentation. I just thought that maybe this had been debunked already because its from 2009.
    Last edited by a moderator: Aug 31, 2015
  2. Trigger Hippie

    Trigger Hippie Senior Member

    I saw that video on aircrap.org the other day. It's hard to understand Harold Saive's concerns since Dr. Kirby states quite clearly "these are clouds". Does Harold not realize that all clouds are formed from both natural and artificial occurring aerosols?

    Here's the full presentation. The quote is close to the 44 minute mark.

    Moderator edit: video was deleted. This is a reupload, the quote comes at 1:15.

    Source: https://www.youtube.com/watch?v=GiNg4equ0fM

    Harold rightly claims that contrail clouds affect the climate. He doesn't mention that the effect is almost insignificant.

    Last edited by a moderator: Jul 12, 2018
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  3. skephu

    skephu Senior Member

    The misunderstanding is due to the fact that many people believe that the word "aerosol" means something that is sprayed.
    It does not; it means solid particles or liquid droplets floating in air, regardless of their origin. Natural clouds are aerosols, for example.
    Yes, the jets do dump aerosols into the atmosphere: it's the contrail, which consists of ice crystals and some soot.
    He meant the contrails and the exhaust emissions.
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  4. WeedWhacker

    WeedWhacker Senior Member

    Yes. This fact seems to require re-iteration.

    There are cases (easily found via Google) of dust particles that originate from Asia being observed in North America (for instance).

    These very small particles of dust can be lofted by winds...and carried for thousands of miles laterally, and inhabit Earth's atmosphere vertically. They can then act as 'nuclei' for condensation purposes.

    This is a 'big' planet in one sense....but not so 'big' in another......
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  5. Mick West

    Mick West Administrator Staff Member

    Kirby is not being that clear there. Yes, aircraft exhaust contain aerosols, and contrails are aerosols, but SO ARE CLOUDS.

    Normal clouds are aerosols, a suspension of small particles in the air.

    But he also seems to be suggesting that it's the aerosols in the aircraft exhaust that cause the contrail formation. This is not entirely accurate, the key factor is the rise in humidity. Clear skies when ice saturation does not necessarily imply lack of aerosols. It implies lack of ice nuclei, and that's what the contrail provides, in the form of ice. The actual soot just changes the ice particle distribution.

    Soot does not act as the cloud condensation nuclei in a contrail except in the fraction of a second when it acts as water condensation nuclei, condensing water, which instantly freezes.

    It's a tricky subject to convey. I think that starting with "clouds are aerosols" might be a good base to form a conversation.

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  6. Ross Marsden

    Ross Marsden Senior Member

    Except that soot is a freezing nucleus and not a condensation nucleus.
    There is an abundance of cloud condensation nuclei, but almost no freezing nuclei.
    The exhaust provides some, and the most important one (probably) is soot.

    It is/was thought that when a droplet freezes, it squirts a shower of fine droplets that are small enough that a significant number spontaneously freeze providing loads more freezing nuclei in the form of ice. This may also explain the behavior of fall streak (hole-punch) clouds.
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  7. WeedWhacker

    WeedWhacker Senior Member

    Sorry...could you expand this explanation? This is interesting (and OT!)...

    Oh and of course..."Bonne année and bonne santé!"
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  8. skephu

    skephu Senior Member

    btw it's Kirkby, not Kirby.
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  9. Mick West

    Mick West Administrator Staff Member

    Exhaust soot is a condensation nucleus, it is not a very good ice nucleus, I refer you to our exchange on this two years ago:

    And as you said:
    Last edited: Dec 31, 2014
  10. Mick West

    Mick West Administrator Staff Member

    But that (droplet freezing, as in hole punch clouds) applies to the seeded (hetrogenous) freezing of relatively large supercooled liquid droplets that are above the homogeneous freezing temperature at that pressure. Contrail particles start out as a very thin layer of liquid water on a CCNw, which then freezes essentially homogeneously, as it's below the homogeneous freezing point. I don't think at those point there's enough mass of water to do the hypothesized seed explosion.
  11. WeedWhacker

    WeedWhacker Senior Member

    Might veer a bit....but as pilots we understand that water droplets can exist...in the atmosphere...and be "below" freezing until disturbed...which for pilots amounts to what is called 'clear ice' on the airplane's leading edges. (These are referred to as "super-cooled" drops of water in the atmosphere. These are most hazardous to airplanes because when "hit", they almost immediately freeze into "clear ice".)

    Other sorts of ice accumulation, IN icing conditions, might be what is called "rime ice".

    "Rime Ice" is more aerodynamically "bad", because of its irregularity. "Clear Ice" is more of a "killer" because it is a bit 'insidious'.

    Of course in the case of modern airliners, these issues of "ice build-up" are usually not an issue, due to the designs, and procedures used by flight crews.
  12. deirdre

    deirdre Moderator Staff Member

    so the hetrogenous 'seed' causes the supercooled droplets to freeze because the 'seed' is THAT much colder or is it just the collision factor... like those videos of soda and beer that are below freezing but dont actually turn to ice until you hit them?

    ex: at 1:35 is this piece of ice an ice nucleus?
    Last edited: Dec 31, 2014
  13. Mick West

    Mick West Administrator Staff Member

    Actually I never thought of that, but it does seem possible. More likely though is that the expelled "seed" of ice would not have enough energy to do that, and would instead act as a seed crystal.

    Supercooled water can freeze in three main ways:

    1) By reducing the temperature even more, so it cools homogeneously
    2) By mechanical shock or agitation
    3) By contact with ice nuclei, like ice, or something with similar exterior molecular structure
  14. deirdre

    deirdre Moderator Staff Member

    so contrails are most likely #3. which does sound more like snowflakes if i remember snowflake formation correctly.
  15. Mick West

    Mick West Administrator Staff Member

    No, contrails form at -40C or below (actually more like -38C, IIRC), which is already cold enough for homogenous freezing, it's more like #1

    Contrails form by water vapor condensing to liquid water on soot and stuff, it then freezes due to being so cold, then can grow more ice directly from the air if it's humid enough.

    More fully:

    1) Hot exhaust gases containing a lot a water vapor are shot out the back of the plane
    2) They mix with the ambient -40F air
    3) At some point while the exhaust gas is mixing with the air, the relative humidity with respect to water is over 100%
    4) During this stage, liquid water condenses on cloud condensation nuclei like soot and sulfur compounds.
    5) This liquid water freezes as it comes into contact with -40° air
    6) These frozen microdroplets then act as ice nuclei
    7) If ambient relative humidity is above 100% with respect for ice (about 60% with respect to water), the ice continues to be directly deposited on the ice crystals
    Last edited: Jan 1, 2015
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  16. Ross Marsden

    Ross Marsden Senior Member

    I'm going to have to read some more about the intricate details of what the CCN and IN are (if in fact IN are needed) in the contrail formation process. One point though, and Mick has made this before, probably 2 years ago, even with pristine pure fuel like hydrogen you will get contrails, utilizating the CNN that are everywhere in the atmosphere (smoke, dust, sea salt). The combustion products of soot and sulfur compounds are not actually needed.

    For general consumption of the cloud physics, Mick's 7 point process is perfectly valid and expresses as simple as possible without being simplified (thanks to Albert E for that distinction).
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  17. WeedWhacker

    WeedWhacker Senior Member

    Um....every launch of a spacecraft that has, in its mix...some H2? Yeah....
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  18. deirdre

    deirdre Moderator Staff Member

    i like it too. but just to clarify for people like me reading, (since gas vs liquid vs solid science twists up my brain) when he says exhaust gases.. he means 'vapor' form of water et al. not gas like i put in my car. right?
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  19. Efftup

    Efftup Senior Member

    Yes. Gas you put in your car is short for Gasoline. If you foreigners called it Petroleum like us who speak English Properly, :D:p, you would call it petrol and then there'd be no confusion between petrol and gas (the thing that isn't liquid or solid)
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  20. Mick West

    Mick West Administrator Staff Member

    Correct. He means exhaust gases as in like what comes out of your tailpipe. Basically water vapor and carbon dioxide.

    Calling gasoline "gas"-oline has an interesting history.
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  21. WeedWhacker

    WeedWhacker Senior Member

    Yes....here in the USA...we just call it "gas"....but in other parts of the World? They say "petrol". Same thing....

    KNOW that for jets? They use a form of diesel, based on "petrol"....but called "Jet-A1".

    Jet-A1 is VERY regulated......it is extremely critical as an Aviation fuel....
  22. Steve Funk

    Steve Funk Active Member

  23. Ross Marsden

    Ross Marsden Senior Member

    I think it also depends on the molecular structure.
    The aromatic hydrocarbons (eg gasoline) has rings of 6 carbons, whereas the alkanes (eg kerosene) have the carbons linearly arranged.
  24. Steve Funk

    Steve Funk Active Member

  25. WeedWhacker

    WeedWhacker Senior Member

    When it comes to the actual chemistry? I admit I am lost, so I bow to this further knowledge.

    ...if a person is advised to purchase an electric lawnmower (for instance) as opposed to one that is run by a 2-cycle gasoline (petrol) engine?

    Which is the "better" choice"? On one hand....that 2-cycle gasoline-powered engine is noisy....an electric is "quiet" in comparison....BUT that same electric must be powered from "the grid"...an electricity source that itself has issues with pollution. (AND has the inconvenient, to some, electrical cord).

    Alternatively....there is the battery-operated lawn device....still of course, the battery must be re-charged once used up...again, from the "grid".

    It always seems to come back to petro-chemical uses of energy extraction.....(?)
    Last edited: Jan 2, 2015
  26. deirdre

    deirdre Moderator Staff Member

    guys the point of my post was so people dont confuse "exhaust gases" with "gasoline". sigh.
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  27. WeedWhacker

    WeedWhacker Senior Member

    So, deirdre....what can I sell to you? The traditional lawnmower, with all that nasty gasoline and 2-cycle oil you have to mix into it?

    Or, a nice quiet rechargeable-battery operated one? ;)

    (The carbon 'foot-print' only gets spread around, with the electric....but your neighbors are less likely to complain about "noise" as you mow the lawn. "Pay it Forward"....ehhh??).
  28. deirdre

    deirdre Moderator Staff Member

    OT dude. i dont mix oil into my lawnmower. i think youre thinking of dirtbikes.
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  29. Trailblazer

    Trailblazer Moderator Staff Member

    The video in the post above has been deleted. Here is another copy of the presentation, which I will edit into the post:


    The relevant quote comes at 1:07.

    What Kirkby means is that the air can be free of clouds even though the humidity is above 100% relative to ice, because there are not sufficient ice nuclei to cause cloud formation. Aircraft supply those ice nuclei, so you get a contrail.
    Last edited: Jul 12, 2018
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