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A review of cosmic rays and climate: a cluttered story of little success

Filed under: — rasmus @ 25 December 2012

A number of blogs were excited after having leaked the second-order draft of IPCC document, which they interpreted as a “game-changing admission of enhanced solar forcing”.

However, little evidence remains for a link between galactic cosmic rays (GCR) and variations in Earth’s cloudiness. Laken et al. (2012) recently provided an extensive review of the study of the GCR and Earth’s climate, from the initial work by Ney (1959) to the latest findings from 2012.

The story is quite remarkable from a point of view on public discourse and climate change – so much hype for so little (the recent excitements from the leaked IPCC drafts, a point in case).

Laken et al.‘s review indicates that there never really were any strong correlations, and subsequent investigation found that those which looked interesting, didn’t stand up to scrutiny. They provide an account of the work on GCR-climate connections which I feel is well in line with the views presented here on RealClimate.

For instance, there have been some claims of statistically significant relationships between the GCR variations over solar cycles as well as during Forbush Decrease events (FD) (here). Laken et al. provide an overview of others who subsequently repeated the analyses behind these claims, and report that errors were discovered pointing to inflated results in the first place.

There were many problems. The data describing the clouds were not sufficiently reliable for studying long-term variations on a global scale. Especially not for the low-level clouds, which often would be obscured by layers of clouds aloft.

Lab experiments such as CLOUD and Sky produced some interesting findings, where charging affected the nucleation rate of the miniscule particles (more here), but the concentrations of these tiny particles do not have a strong influence on the concentration of substantially larger cloud condensation nuclei (CCN) (here and here).

The hype in the past was prompted by films, such as the ‘Cloud Mystery’, and proponents who gave the impression that GCRs can explain the global warming. There was never any solid support behind this claim: in fact, as noted long ago, there has been no trend in GCR. Furthermore, any resemblance between GCR/clouds and the global mean temperature is lacking (see the grey curve in the figure below).

A comparison between time evolution in the global mean temperature (dark red) and different solar indices (bottom) as well as CO2 forcing (green). All the curves here have been standardised, and the solar curves are shown along the bottom. The GCR are shown in grey, and have been multiplied by -1 to emphasise the correlation with the other solar indices.

In my opinion, Laken et al. provide an accurate comprehensive review of the hypothesised effect of GCRs on our climate through moderating the clouds. There is still no evidence suggesting that the GCR influence our climate in significant ways.

We wish all our readers a Merry Christmas!


  1. B.A. Laken, E. Pallé, J. Čalogović, and E.M. Dunne, "A cosmic ray-climate link and cloud observations", Journal of Space Weather and Space Climate, vol. 2, pp. A18, 2012.

40 Responses to “A review of cosmic rays and climate: a cluttered story of little success”

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    Yes, Geoff. The conservative IPCC vies is something that I have sistematically shown in my blog (sorry it’s in Portuguese). However, it is hard to expect much more. I think that scientists and others that recognize those limitations and understand why have to bring those issues to the general public and decision-makers/policy-makers everywhere.

  4. 4
    Unsettled Scientist says:

    Merry Christmas to you (and all the RC contributors) as well. I haven’t had time to comment but still read every post. Thank you for your continuing efforts to help educate the public.

  5. 5

    [Typo, second to to last para, “oinion” = “opinion”]

    [Response: fixed. thanks. – gavin]

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  7. 7

    [Typo, “Forebush Decrease” should be “Forbush Decrease“]

    [Response: Thanks! Fixed now. -rasmus]

  8. 8

    The key to this information (about correcting misinformation) is making it accessible to the general public. Just because your science is based on facts does not make it available for general discussion. My wish for you is that a non-political or non-science writer weaves these GCR facts into a hip-hop song, a super-hero movie or a zombie video game. Stranger things have happened. The youth of our beleaguered planet must carry these facts forward.

  9. 9
    Russell says:

    Forecasts of amphibious reindeer landings at 90 North notwithstanding,a very merry Christmas to all!

  10. 10
    Steve Bloom says:

    Re #9: They’ll be OK since the whole crew can just decamp to the Claus summer estate in the scenic Gamburtsevs, notwithstanding that the elves may be in for some serious shoveling preparatory to getting the place aired out.

  11. 11
    Jean says:

    I try to pass on to other non scientists like myself what I learn //so Thanks!!!Happy New Year

  12. 12
    Eli Rabett says:

    Eli has been thinking about what is the rate limiting step in CCN formation. While it is clear that SO2 availability is the rate limiting step over land, DMS should be available enough over oceans that it is not rate limiting, and if cosmic rays are not, what is?

  13. 13
    David B. Benson says:

    Eli Rabett @12 — As I understand the matter, there is a superabundance of CCNs everywhere except maybe interior Antarctica where it does not matter.

  14. 14
    Patrick says:

    @ 10 I heard that children who follow satellite photos of things like the Petermann Glacier are sending Santa letters saying, “Santa, get out of there the ice is melting!”

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    Christopher Squire says:

    Re: ” . . the recent excitements from the leaked IPCC drafts, a point in case).”

    The expression is ‘‘case in point’‘:

    ‘case n. . . Phrases
    P1. With prepositions.
    . . f(c) Apposite, appropriate, or pertinent. Now chiefly in ‘case in point’: an apposite instance, an example that illustrates the point.
    . . 1875 W. S. Jevons Money iv. 24 The wampumpeag of the North American Indians is a case in point, as it certainly served as jewellery.
    . . 1996 Sci. Amer. Jan. 84/3 Much of the ecological evidence about sex is open to sharply differing interpretations. A case in point concerns the ‘haplodipoid’ sex-determining system of ants, bees and wasps.’ [OED]

    Thanks for a most useful blog: I wish you a Happy and Productive New Year.

  16. 16
    Hank Roberts says:

    > what is the rate limiting step in CCN formation

    I really miss the headinacloud blog.
    Where else might this question be addressed?

    (I’d guess there are many answers, as various kinds of stuff that could act as a condensation nucleus for clouds moves, gets altered over time, runs into different temperature/humidity/dewpoint conditions — but why guess?)
    turns up

    DOI: 10.1002/pro.2015
    Structures of dimethylsulfoniopropionate-dependent demethylase from the marine organism Pelagabacter ubique
    Protein Science
    Volume 21, Issue 2, pages 289–298, February 2012

    Hmmm, is the common precursor to available CCNs something as simple as how much of one particular enzyme is active in bacteria in the surface layer, and which way the wind blows? And what if MonDieuPonsanto’s next

    “Dimethylsulfoniopropionate (DMSP) is a ubiquitous algal metabolite …. DMSP is a precursor for the climatically active gas dimethylsulfide that is readily oxidized to … products that act as cloud condensation nuclei…. the enzyme responsible for DMSP demethylation by marine bacterioplankton … has only recently been identified and biochemically characterized….”


    Hey, eventually we’ll get a natural experiment, when some persistent organic chemical from MonDuPonsanto turns out to block that enzyme. What’s the worst that could happen?

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    John Baez says:

    When the gray dots on that graph are high, then fewer galactic cosmic rays hit the Earth, right? After all, increased solar activity reduces the number of those cosmic rays that make it to Earth.

    [Response: The GCR are plotted inversely “-CLIMAX”, so you indeed have a minimum in GCR at the solar cycle peak. -gavin]

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    Jim Larsen says:

    Leaking the report seems to have done some good here, as the wording can be strengthened as a result. The more claims and distortions that are directly addressed in the final document the better.

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    Gerald Wilhite says:

    Why don’t you include the HADCRUT4 data in the graph?

  20. 20
    Hank Roberts says:

    Gerald Wilhite: why bother?
    “HadCRUT4 is in … agreement …. in recent years … a bit higher than NCDC but a bit lower than GISS.”

  21. 21
    Jim Larsen says:

    20 Hank asked, “Gerald Wilhite: why bother?
    “HadCRUT4 is in … agreement …. in recent years … a bit higher than NCDC but a bit lower than GISS.” ”

    When your favored metric agrees with your opposition’s metric, only a fool would put his own metric on anything.

  22. 22
    Don Ciesielski says:

    When you shut off your oven does it go to zero immediately? When the sun goes does in a desert does it get cold quickly? When the sun goes down, during the summer, in a forested area, does it stay warm at night? When you heat up something of mass, perhaps a large rock or boulder in a fire pit or fire place, will it hold heat for awhile, perhaps longer than something of less mass? When you have less ice in a cooler, will things get warmer as the ice melts and the water is warmer? If you put more ice in it, will they get colder immediately? Would it take more or less ice to change the temperature in the cooler if the melted ice is cool or if it is lukewarm or warmer than lukewarm? Would the temperature change quicker or slower according to the amount of ice put into the cooler with warm, melted ice in it? Would it matter if the cooler was hot, lukewarm or somewhat cool prior to putting in the ice?

    The sun warmed the earth for the past fifty to sixty years. Now there is less sun active. Cloud cover isn’t permanent but is more frequent due to less GCR. Temperatures are not rising as much anymore but instead are moving sideways and/or cooling.

    Could nature have provided some cover for itself by melting the glacier ice to warm the waters to prepare for a possible cooling period? Would that be a good way to do so? If it is preparing for a pretty long cold period, would it be better to put more warm water into the oceans or less? Would it be better to remove more ice and deposit more warm water to keep its temperature within a certain range so that the life it supports can survive?

    We are busy looking behind and looking ahead at only the man made possibilities. Perhaps we need to put the past natural responses together and look forward as what nature might be up to also.

  23. 23
    Ray Ladbury says:

    Don Ciesielsk,
    WTF? I’m sorry but it was hard to see through all the misunderstandings and false premises to your central point. Why not go to the Start Here tab, learn what the science actually says and then come back and try again?

  24. 24

    #22–“Could nature have provided some cover for itself by melting the glacier ice to warm the waters to prepare for a possible cooling period? Would that be a good way to do so? If it is preparing for a pretty long cold period, would it be better to put more warm water into the oceans or less? Would it be better to remove more ice and deposit more warm water to keep its temperature within a certain range so that the life it supports can survive?”

    This seems to be the anthropomorphic fallacy writ large. If you really think that Nature predicts the future and looks out for our welfare, then I’d say you have developed a certain kind of faith–that is, a belief formed in the absence of any evidence whatever.

    Ditto, if you really think you’re the only one who knows about so-called ‘thermal inertia.’

  25. 25
    flxible says:

    re 22/24: More to the point, if we’re going to attribute intention to nature, wouldn’t it be more likely what “she” is up to is trying to rid herself of this scourge of terra-forming critters that are defacing her artwork?

  26. 26
    Dave Griffiths says:

    When the first two volumes of his Principia were published, Isaac Newton found himself dealing with the type of confusion exhibited by Don Ciesielski. Newton saw it as death by a thousand hypotheses. To deal with this he began his third volume with his rules for (scientific) reasoning. They are all worth reading, but here I will only quote Newton’s 4th rule and his comment:

    “In experimental philosophy we are to look upon propositions collected by general induction from phaenomena as accurately or very nearly true, notwithstanding contrary hypotheses that may be imagined, till such time as as other phaenomena occur, by which they may either be made more accurate, or liable to exceptions.

    This rule we must follow, that the argument of induction may not be evaded by hypotheses.”

    Applied to the present case we have a simple argument by induction:

    1. The level of CO2 in the atmosphere has been increasing since ~ 1750, and is now increasing rapidly (about 2 ppmv/year)
    2. The increase in CO2 correlates very closely with estimated emmisions since 1750 (the CDIAC webpage gives estimates by Marland and Rotty, and Houghton and Hackler – but you have to convert cumulative emitted Carbon to ppmv ). About 41% of the emitted CO2 stays in the atmosphere, most of the rest produces ocean acidification).
    3. CO2 is a greenhouse gas so it raises the earth’s average surface temperature. This increases the average water vapor level which also tends to warm things up.
    4. The rise in yearly average temperature since 1880 correlates fairly well with the rise in the CO2 level. The correlation is very good if you use 10 year floating averages to remove high frequency noise.
    5. The correlation of temperature and CO2 level is compatible with the temperature rises predicted by the big models.

    The argument of induction says “Global warming is caused by increasing CO2 which is caused by human activity such as burning fossil fuels”

    So why do you need more hypotheses? Taking, for example, the behavior of solar radiation. There is no evidence that it has increased appreciably since 1880. Also, the experts are watching this. For example, the global cooling of ~ .3 deg. K that occurred during the Maunder minimum was explained by Shindell et Al (SCIENCE VOL 294 7 DECEMBER 2001) on the basis of a reduction in solar radiative forcing of ~-.3 watt/m.sq. The 30% increase of atmospheric CO2 since 1750 is equivalent to a 1.4 watt/m.sq. forcing. So, using a crude linear estimate, this should cause a temperature rise ~ 1.4 deg C, whereas the actual is a little smaller, ~ .9 deg.K (from 1880). But here we ignored niceties such as transient vs steady state temperatures (yes, when you turn off your oven it does not immediately cool). Anyway, the main point is: no need for hypotheses, standard climate theory works very well.

    This being said, I think that a lot of confusion could be dispelled if the information mentioned in 1,2 and 4 was readily available in graphical form (on this site?). Then perhaps we would be spared the really weird hypotheses such as “Are the rising atmospheric CO2-levels a result of oceans warming up?”

  27. 27
    Ray Ladbury says:

    Dave Griffiths, That quote by Newton is worth the weight of all 3 volums of Principia in gold!

  28. 28
    Dan H. says:


    Very good statement, until you got to the part of solar radiation. The following is a graph of solar irradiance since 1880:

    [Response: Way out of date – try this instead. – gavin]

    While you could argue that the effect of this increase would be less than that from CO2, claiming that there has not been an increase would be erroneous.

    Less of a concern is the correlation between temperature and CO2 rise. While the CO2 rise has been fairly consistent, the temperature rise has not. Clearly, other influences have been at work also. This does not negate the role of CO2. However, to so readily dismiss other variables is foolhearty.

  29. 29
    Ray Ladbury says:

    Dan H. “Less of a concern is the correlation between temperature and CO2 rise. While the CO2 rise has been fairly consistent, the temperature rise has not. Clearly, other influences have been at work also.”

    It’s called weather. Google it. Fascinating stuff.

  30. 30
    Hank Roberts says:

    > While the CO2 rise has been fairly consistent, the
    > temperature rise has not. Clearly, other influences ….

    Correlation doesn’t imply a _consistent_ temperature increase.

    “… in fact it’s mainstream climate scientists who identified those other influences. Natural factors cause temperature fluctuations which make the man-made global warming signal less clear ….”

  31. 31
    Hank Roberts says:

    Dave Griffiths, you asked for a collection of graphics to illustrate the basics.

    You should follow Tamino’s site, which does far more than collect other people’s images (as you saw from Dan H.’s pointer, there are lots of bad sites with outdated graphics).

    Tamino cites the data sources, generates the graphics, and goes through the analysis. (There are others doing the similar work, who get mentioned there.) He’s also very good at nailing the deniers and befuddlers who try to fool people.

    Here’s one of the recent best:

  32. 32

    Dan H,

    Yes, solar irradiance is somewhat higher now than in 1880. Gavin’s reference is useful but a bit of an eye test. I found it easier to download data from:

    Using 11-year averages to remove most of the fluctuations due to the sun spot cycles, the TSI levels were 1360.62 watt/m.sq. in 1880, and 1361.17 watt/m.sq. in 2006. The net forcing (using the usual definition) is the difference in TSI divided by 4 and multiplied by .7 (albedo effect), i.e. 0.097 watt/m.sq. This is to be compared to the forcing due to a 30% increase of CO2, 1.4 watt/m.sq.

    So the CO2 forcing is an order of magnitude greater than the solar forcing, and the solar forcing can be ignored (to a first approximation).

    There are clearly other factors, Mt. Pinatubo for instance, but CO2 is the main factor. When I run a correlation of yearly temperature anomaly vs. ln(CO2/CO2ref) I get Rsq=0.86, and if I use 10 year floating averages to get rid of that pesky El-Nino etc the Rsq goes to .93. The results agree with the big models in that they are equivalent to a transient response of 2 deg. K to CO2 doubling.

    What would be really foolhardy would be to ignore the obvious. I’ve spent time in China and I can easily believe they are building two coal fired plants a week. They are pouring incredible amounts of concrete. The economy doubles in less than 10 years. The CO2 from the Alberta Tar Sands is a drop in the ocean compared to China’s increasing output. Fortunately the Chinese are very smart and I don’t suppose it will be long before they are selling us the technology needed to deal with the problem.

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    Charles says:

    I thought Ray Pierrehumbert had a good comment back in 2007 regarding the chances that solar irradiance was the cause of recent warming: “That’s a coffin with so many nails in it already that the hard part is finding a place to hammer in a new one.” (But several new nails have been hammered in since then.)

  34. 34
    Dan H. says:

    Weather is a term used to describe short-term events like this year’s U.S. summer heat wave or the European winter cold snap. It is not typically used to describe decadal-long temperature trends, which may be less fascinating, but nevertheless, noteworthy.

    [Response: ‘Weather’ has impacts on all time scales – including interdecadal. – gavin]

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    Dan H. says:

    These are two different methods for calculating the solar input. Regardless of the method and final numbers, the trend is similar. A similar trend can be seen in the sunspot data, which some have maintained is a greater influence.

  36. 36
    Hank Roberts says:

    > the trend …
    > a similar trend


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    Susan Anderson says:

    “So the CO2 forcing is an order of magnitude greater than the solar forcing, and the solar forcing can be ignored (to a first approximation).”

    A statement of such clarity and simplicity it is hard to understand how it can be misconstrued. Never mind that recently the solar input is going in the opposite direction.

    Heidi Cullen makes a useful synthesis: climate is weather over time and space. I add that time is several decades at the least, and space being the whole globe, perhaps to some extent split by the equator. Fake skeptics are fond of isolating pieces of the picture, but real scientists always take in as much as they can, though they may focus on parts to work on them.

    For coriolis forces in action, this is fascinating and beautiful, if a bit too fast. More local ones can be found by clicking around, and of course many other agencies provide similar materials. The evolution of this over the few years I’ve been watching it is startling, but one could not draw conclusions from it day to day, except to enhance one’s understanding of current weather patterns (for example, there was a triple spiral in the Pacific that ended up with several east coast storms.

  39. 39
    Pete Dunkelberg says:

    Since we are saying what climate and weather are all over again in the cosmic ray thread:

    The earth’s climate is a manifestation of how the radiation from the Sun is absorbed, redistributed by the atmosphere and oceans, and eventually re-radiated in to space.


  40. 40
    Dan H. says:


    I’ll buy that. This is from NOAA, “weather consists of the short-term (minutes to months) changes in the atmosphere.”