Accelerator results on cloud nucleation (2)

Climate Change News and Comments

Did you get the message?

I’m not sure that the significance of my 15 May post, about the accelerator experiment in Aarhus, has been fully grasped. Following my 13 May post, the blogosphere seems to be still in a “waiting for CLOUD” mode. Yes, it will indeed be fascinating to see the first results from CERN’s CLOUD experiment in two or three months’ time, but meanwhile we have the results from Denmark. Perhaps I was negligent in not giving a little history.

The first laboratory test of the Svensmark hypothesis was the SKY experiment in Copenhagen, the outcome of which was published by the Royal Society of London in 2007. The positive results were of course politically incorrect, because Henrik Svensmark’s discovery of the effect of cosmic rays on clouds gave the Sun a much larger role in climate change than supporters of the man-made global warming hypothesis would like to admit.

The warmists were offered a delaying tactic by physicists who said, “Ah, but the SKY people used only natural cosmic rays and radioactive sources. Don’t believe them unless the CLOUD experiment in Geneva, simulating the cosmic rays with a fully controllable beam of accelerated particles, gets similar results.”

Conveniently for the warmists, CLOUD was very slow to get going. Meanwhile the Danes continued with their own experiments, including the one using an accelerator at Aarhus, as reported in Geophysical Research Letters a few days ago. The most important points are:

  • The effect of cosmic rays in helping to seed cloud formation is verified with a particle accelerator, just as critics of SKY were demanding four years ago.
  • A simple radioactive gamma-ray source gave just the same results in the Aarhus set-up so the earlier insistence, that only an accelerator experiment would do, was unwarranted.

Nevertheless, let’s say good luck to the CLOUD team. Their big chamber should be able to trace the growth of aerosol seeds much farther than in the small chamber used at Aarhus. And they have a large programme of future work, simulating atmospheric conditions at different altitudes.

See the Aarhus University press release that came out yesterday evening:

For references and other links, see my previous post:

For a video interview with Jasper Kirkby of CLOUD see:

Added 18 May: Ah, now the word is spreading. See

Anthony Watts:

David Whitehouse:

The second item quotes me directly, and at the end of the second paragraph I should really have said ionizing “gamma rays” instead of “particles” — I amended it on this blog a few hours after posting it.

Added 20 May: Friendly words from The Scientific Alliance

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27 Responses to Accelerator results on cloud nucleation (2)

  1. Max_b says:

    Sorry Nigel, but it’s difficult to make any judgement whilst the paper is stuck behind a paywall.

    • calderup says:

      Well Max, this side of the paywall on the abstract page there is a figure from the paper. You need to click on the box to the right of the Fig. to see it whole.

      Let me explain the figure informally. It shows the counts of aerosol particles (4 nanometres) formed when a beam of 580 MeV electrons froin the Aarhus accelerator entered a reaction chamber filled with synthetic air containing sulphur dioxide, ozone and water vapour. That was after ten minutes’ exposure to UV light had made sultphuric acid molecules in the mixture. After 60 minutes the aerosol particles had dispersed and the test could be repeated using a different beam exposure to produce a different intensity of ionization, or alternatively to use gamma rays from a sodium-22 source.

      After Runs 1-5 (top slope) the cylinder supplying the air was changed, and the counts of aerosol particles were lower in Runs 6-9 (middle slope), presumably because of some unidentified contamination. In Run 10 they fell again. Regardless of those changes, there was always a marked and progressive increase in the aerosol counts across a large range of increaing ionization of the air.

      The results using gamma rays (crosses in the figure) were indistinguishable from those using the electron beam.

      Hope that helps


      • Max_B says:

        I appreciate the reply, but the abstract and press release are no substitute for the actual paper. When do the public get to read it?

      • calderup says:

        As a writer who has depended on copyright earnings for more than half a lifetime, I can’t share your belief, Max, that all reading matter should come free. The folk at Geophysical Research Letters have families to feed too.
        Having said that, perhaps rather piously, I would be silly not to notice that someone else has breached the paywall for tou. See Agust Bjarnason’s comment below.

      • Max_b says:

        I don’t believe I’ve stated any such belief. More importantly, your assumption is incorrect.

  2. Kate RC says:

    Very interesting, exciting news. Congratulations to the Danish team.

  3. UzUrBrain says:

    Just how different is this than the typical highschool experiment with a cloud chamber (dry ice above in a sealed plexaglas container)and showing the tracks of ionizing radiation? I had only seen a picture when I tried it in the 60′s for the science fair project. Don’t these AGW folks take highschool physics? It has always seemed obvious to me that radiation caused clouds.

    • calderup says:

      Henrik Svensmark recalled his own experience with a high-school cloud chamber when first thinking about the effect of cosmic rays on clouds. But the link is aesthetic and imaginative rather than mechanistic, because the conditions in the atmosphere are very different. In the old cloud chamber highly supersaturated vapour condenses directly onto charged atoms. In the atmosphere, barely supersaturated water vapour needs chemical specks (aerosols) on which to condense, so it’s a two-stage process, with the cosmic rays helping to make the specks. If the old cloud chamber had ever been a sufficient demonstration of the Svensmark effect, the argument would have been settled long ago.

  4. Bishop Hill says:

    Has HS determined how much of the recent warming is due to changes in cloud cover and how much due to CO2?

    • calderup says:

      To pin down the exact shares of solar and anthropogenic forcing in the warming during the past century is still work in progress, Anthony. It’s made all the trickier by significantly different versions of the ‘facts’ about temperature changes in the air and the ocean, as well as by short-term contributors like volcanoes and El Nino, and apparent natural changes in the workings of the weather machine itself. The cloud-cover records are particularly messy because of changes in the populations of satellites observing them.
      Wearing a reporter’s hat, rather than a physicist’s, let me just say I’d be very surprised if the anthropogenic forcing accounted for more than 20% of the warming since 1900.

  5. Philip says:

    Yes indeed, congratulations to the Danes, good luck to CLOUD and thank you for bringing us this news.

    I agree the evidence for an effect of cosmic rays on cloud cover looks very convincing, but I imagine that the attribution to late 20th century warming will still be questioned. The press release says that the Danes will “now carry out systematic measurements and modellings to determine how important it is to the climate.” It will be very welcome indeed to have those numbers at our fingertips!

  6. Thanks for the interesting update Nigel.

    Dr. Leif Svalgaard (Also Danish :-)has this link to his research page in WUWT’s blog at May 17, 2011,10:22 pm:


    Best regards
    Agust Bjarnason, Iceland,

  7. Cleanwater says:

    This experimental work is very important, it’s not just Hypotheses- it’s real data.
    There is one major problem with the semantics: Everyone keeps using the references to “climate changes” THIS IS BULL! Cloud formation and all this other work has to do with weather changes- after a few thousand days of weather changes you might find that there is some “climate change”
    Definitions of the Climate Discussion
    What is Climate?
    Definition:A few 100 thousand weather days end to end for a specific location.
    How many climates are there in the world?
    Every part of the country and the world has a unique climate -the south of France, the North slope of Alaska, the heart of Africa, the northeast Great Lakes region of the US ,the north of Italy, the south of Italy,thousands of different climates etc.
    What is weather?
    The atmospheric conditions where you are.
    Can mankind control the weather?
    We have tried for thousands of years from the Indian rainmaker, to the cloud seeders of the 1950-60. Man can not control the weather, then how the hell can man be controlling the climate. This whole B.S of MANN-made global warming is a fairy tale.

  8. Simon Conway-Smith says:

    The key experiment to do of course is to vary the concentration of CO2 whilst keeping everything else constant, and observe the effect. This may be irrelevant to us who understand, but to be able to positively demonstrate that CO2 does not affect the result will go a long way to silencing the warming/greenhouse gas theory advocates.

  9. alexjc38 says:

    It will be good to have both the Aarhus and CERN results, and thus (fingers crossed) independent replication of findings, which should help to go some way in silencing the critics. The start of a new chapter in climate science? I hope so.

  10. Bruce of Newcastle says:

    I for one think the result is very important. It offers a potential mechanism for the empirical relationship described by Butler & Johnston 1996, which with the PDO and low sensitivity CO2 (ie as found by Lindzen Spencer & others) I’ve found fits the CET trend exactly.

    Looking forward to the CLOUD results with interest!

    (Apologies to F-C&L, but when you mention their work you get stomped on out of hand without any consideration of the actual data.)

  11. [...] SKY en het kersverse Aarhus nu nog even wachten op CLOUD. Lees meer op Nigel Calders blog. [...]

  12. Tom says:

    Is there a possibility that the venting ‘steam’, that we see coming from the Fukushima reactor buildings, could be radioactive clouds being formed? I am sure there are active Gamma-ray sources. We all can observe it, too.

    • calderup says:

      I honestly don’t think it’s relevant, Tom, although there have been attempts to pooh-pooh the Svensmark hypothesis by reference to nuclear weapons tests in the atmosphere.

  13. Don B says:

    Another Physics World article on cosmics seeding clouds:

  14. Kate RC says:

    Would you mind explaining – in, say, 50 words what this really means?

  15. Kate RC says:

    Sorry – missed a hyphen in my earlier post. It’s just that people are asking what this all means.
    I’m sure we plebs wouldn’t object to more than 50 words. Thankyou.

    • calderup says:

      The chief alternative to man-made greenhouse gases as an explanation of the global warming of the 20th Century is a big influence of the Sun. In the Svensmark hypothesis, the Sun’s control of cosmic rays intensifies its effect, because cosmic rays assist in cloud-making by helping to make little specks on which water droplets condense to form clouds. Using beams of accelerated sub-atomic particles to simulate the cosmic rays, the Aarhus and CLOUD experiments verify the increase in speck formation, But Aarhus also shows that earlier Danish experiments done without accelerated particles were equally valid, even though the warmists have been stalling for four years, waiting for CLOUD.
      Sorry, Kate, I make that 108 words. For another quick but somewhat broader sketch of the mechanism and implications of the Svensmark hypothesis see

    • Don B says:

      Also taking more than 50 words – 7 pages, actually – is Svensmark’s 2007 article on Cosmoclimatology.

  16. [...] Pero por una fea ironía, la única contribución atribuída a Svensmark en la información de Nature es el trabajo de 1997  (Svensmark y Friis-Christensen) en el que basé mi conferencia del CER. No hay mención de los exitosos experimentos del equipo danés en Copenhague, Boulby y después Aarhus, sobre la química de iones y la formación de racimos moleculares, usando un haz de partículas (en vez de rayos gama y rayos cósmicos naturales) para ionizar el aire de la cámara. Ver: [...]

  17. [...] Pero por una fea ironía, la única contribución atribuída a Svensmark en la información de Nature es el trabajo de 1997  (Svensmark y Friis-Christensen) en el que basé mi conferencia del CER. No hay mención de los exitosos experimentos del equipo danés en Copenhague, Boulby y después Aarhus, sobre la química de iones y la formación de racimos moleculares, usando un haz de partículas (en vez de rayos gama y rayos cósmicos naturales) para ionizar el aire de la cámara. Ver: [...]

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