Climate Science Glossary

Term Lookup

Enter a term in the search box to find its definition.


Use the controls in the far right panel to increase or decrease the number of terms automatically displayed (or to completely turn that feature off).

Term Lookup


All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.

Home Arguments Software Resources Comments The Consensus Project Translations About Donate

Twitter Facebook YouTube Pinterest

RSS Posts RSS Comments Email Subscribe

Climate's changed before
It's the sun
It's not bad
There is no consensus
It's cooling
Models are unreliable
Temp record is unreliable
Animals and plants can adapt
It hasn't warmed since 1998
Antarctica is gaining ice
View All Arguments...

Keep me logged in
New? Register here
Forgot your password?

Latest Posts


What's the link between cosmic rays and climate change?

What the science says...

Select a level... Basic Intermediate Advanced

Cosmic ray counts have increased over the past 50 years, so if they do influence global temperatures, they are having a cooling effect.

Climate Myth...

It's cosmic rays
"When the Sun is active, its magnetic field is better at shielding us against the cosmic rays coming from outer space, before they reach our planet. By regulating the Earth’s cloud cover, the Sun can turn the temperature up and down. ... As the Sun’s magnetism doubled in strength during the 20th century, this natural mechanism may be responsible for a large part of global warming seen then."  (Henrik Svensmark)

The galactic cosmic ray (GCR) warming hypothesis is based on the premise that GCRs can "seed" clouds, and clouds reflect sunilight.  So if there are fewer GCRs reaching Earth (because a strong solar magnetic field is deflecting them away), the hypothesis says there will be fewer clouds, more sunlight reaching the Earth's surface, and thus more global warming. 

So more solar activity means a stronger solar magnetic field, which means fewer GCRs reaching Earth, which hypothetically means fewer clouds and more warming.

The body of scientific research has determined that GCRs are actually not very effective at seeding clouds.  However, the hypothesis is also disproven just by examining the data.  Over the past five decades, the number of GCRs reaching Earth has increased, and in recent years reached record high numbers.  This means that if the GCR-warming hypothesis is correct, this increase in GCRs should actually be causing global cooling over the past five decades, and particularly cold temperatures in recent years.

On the contrary, while GCRs are up, global temperatures are also way up, and temperatures in recent years reached record highs.

GCR vs. Temp

Annual average GCR counts per minute (blue - note that numbers decrease going up the left vertical axis, because lower GCRs should mean higher temperatures) from the Neutron Monitor Database vs. annual average global surface temperature (red, right vertical axis) from NOAA NCDC, both with second order polynomial fits.

Last updated on 6 January 2013 by dana1981. View Archives

Printable Version  |  Offline PDF Version  |  Link to this page

Further reading

A team of scientists from 17 countries have found the most likely origin of galactic cosmic rays - the centres of distant galaxies (Active Galactic Nuclei) powered by supermassive black holes. This discovery is not particularly pertinent to the global warming debate but it is cool :-)


Prev  1  2  

Comments 51 to 68 out of 68:

  1. pixeldust#49: "it means scientists are being "censored" and "gagged""

    Wow, things must be really slow in deniersville. Since when is the very reasonable request made by Heuer, asking a colleague to be 'clear,' rise to the level of 'censorship'?

    Why not focus on science questions that arise from these supposed 'results'? For example, the PhysicsWorld article dropped what I consider a rather shocking bit:

    ... the researchers found that this effect also took place when they used a radioactive sodium source, which produces gamma rays, and as such claim that similar measurements in the future will not require expensive accelerators. -- emphasis added

    Great news! No accelerator needed. But what does it really mean if the 580 MeV (see PhysicsWorld cited above) accelerated electrons that CLOUD used to simulate GCRs and gamma rays from radioactive sodium produce the same effect? It's supposed to require the higher energy of a GCR (100s of MeV to GeVs) to seed clouds. But Na22 produces 0.5 and 1.27 MeV gamma rays; Na24 (formed by neutron bombardment of stable Na23) produces 1.37 and 2.75 MeV gamma rays. What isotope did they use and what energy gammas resulted?

    If they used low energy gammas from these sodium isotopes, it means that all cosmic radiation, not just the higher energy GCR component should be making clouds! Solar cosmic rays (mostly protons in the solar wind), which give rise to the ubiquitous muon flux we see at the surface should also produce the same effect.

    Or it means that the whole concept is total bunk. Bet deniers wouldn't like to hear that.

    Once again, my apologies to Sondheim:

    But where are the clouds?
    Send in the clouds.
    Well, maybe next year.
  2. Given Musch 2005 I think these GCR guys have an uphill battle.

    Not only do they have to explain a highly complex mechanism they are going to have to explain why their theory works other times but didn't work in this case. The deck is pretty well stacked against them.
  3. Oh, that slide comes from Alley's AGU A23A lecture.
  4. Oh no! A new denial meme about to be born:


    This Letter reports the discovery of an antiproton radiation belt around the Earth. The trapped antiproton energy spectrum in the South Atlantic Anomaly (SAA) region has been measured by the PAMELA experiment for the kinetic energy range 60-750 MeV.

    So it's anti-matter that's been causing global warming all along. The anti-water that forms from these anti-protons (and those evil positrons) will destroy us all -- anti-rain is clearly the cause of the drought (which could also be called an anti-flood).

    Be afraid, be very afraid. Bet Svensmark wishes he'd found this.

    [DB] Ah, the Bridge of the Gods has been found!  All that is left is for one to project one's atman into it, then return as the Avatar of Tathagatha, with both raised Aspect and Attributes...

    Of course, that will probably be denied, too.

  5. CERN CLOUD project results are published, discussion @ RC. I suspect they are not all that was hoped for, but I need to read the article.
  6. Dikran,

    Their experiments produced between ten and a thousand times fewer aerosol particles than found in nature, which basically means that they have not determined the cause of the aerosol formation in our atmosphere. The results were not what they hoped for in that no climatic conclusions could be drawn from their work. But as any good scientists will tell you, this study will inspire more research in the area.
  7. 54, muoncounter,

    Really, I find your anti-denial of such science to be the antithesis of all that science represents.

    As Dorothy would tell you, anti-Em may not be the Wicked Witch of the West, but she's no Glinda the Good Witch, either. That, my friend, makes this entire topic a horse of a different anti-color. Or would that be an anti-horse?

    I suppose I should visit WUWT to be set straight on such issues.
  8. Eric, I completely agree (I try to be a good scientist, but I try to avoid talking to myself as much as possible ;o) as do the RC chaps. The really interesting thing about the CLOUD project as far as the climate debate is concerned is that it is a good example of how science and science funding actually works. Skeptic often say that government agencies will not fund their work, but CLOUD is a big project (see the number of authors) with big funding (about 12MECU IIRC), that aims to investigate the very most basic physical underpinnings of an alternative hypothesis (for which there is only the most circumstantial evidence). It also shows that skeptical hypotheses can and do result in good basic science of general interest to the research community. It also shows that the outcome of an experiment can be very interesting and useful, even if it doesn't provide much support for the working hypothesis (and hence suggest new lines of enquiry or provide support for an existing line etc). A really good experiment is one that has a 50-50 chance of corroborating or refuting an hypothesis as these are the ones that provide the most information about science (in an information theoretic sense). This means we should expect experiments to reject the working hypothesis on a regular basis (a significant minority of experiments); it shows that the research is "sharp".
  9. 58, Dikran,

    Well said.

    The only thing that I would add would be that anyone should look at that study and its conclusions and from it recognize that such research is absolutely in its infancy. It is going to develop and progress as it should, but it needs to build its very foundations before it can progress to making many meaningful conclusions about effects on climate.

    It is not going to challenge current climate science anytime soon (which says nothing about whether it ever will or won't), and skeptics need to avoid trying to use such research, and every resulting paper which will merely represent another baby step in the process, as a debate tool to be used to provide one more "let's wait and see, we don't know enough about clouds and GCRs yet" excuse.

    Let it just be good science at work.
  10. Sphaerica Indeed, a good example of how not to communicate is Svensmark and Calders book "The Chilling Stars", which essentially attempts to explain every change in (paleo) climate to GCR (slight over-statement there, but only slight) before the fundamental work demosntrating that GCRs actually could affect climate (nevermind whether they did). As a scientist (of sorts) I cringed reading the book, not because the theory is bad, but the lack of perspective which is potentially maximising the height of the fall they are setting themselves up for.

    I am always very suspicious of any paper that comes with a press release suggesting its findings are contraversial; most often such a paper either (a) doesn't actually support the message of the press release or (b) turns out to be wrong or (c) both. It is much easier to think of examples where this is true than it is for papers that actually did merit controversy.
  11. First it was 'cosmic rays cause clouds;' now its 'Role of sulphuric acid, ammonia and galactic cosmic rays ...' Have the goal posts shifted? And why does the NatureNews headline read Cloud formation may be linked to cosmic rays, which is not at all a justifiable conclusion of the paper?

    From the Kirkby abstract,

    We find that atmospherically relevant ammonia mixing ratios of 100 parts per trillion by volume, or less, increase the nucleation rate of sulphuric acid particles more than 100–1,000-fold.

    Hmm, 100 parts per trillion NH4 is significant now, yet 395 CO2 parts per million is not?

    Sphaerica#57: You open an interesting possibility. If there is a good witch (helpful to Munchkins everywhere), surely an evil witch (very destructive) could be referred to as an anti-good witch. And the abbreviation for that is AGW!!!
  12. According to Watts, Svensmark has now unveiled a GCR Theory of Everything! There's no need for a link, he's tethered to piece to the homepage so the gang all know the world as we knew it is now over (think I'm exaggerating? Read Watts' piece!)

    I'm sure you're probably already aware of it, but I thought I'd point it out!...
  13. Sounds like Svensmark has decided to go full Climastrology.
  14. Well, my first thought upon reading Watts' rapturous acclaim was 'so the Astrologers were right, after all'! ;-)

    If this thing holds up I'd expect triumphalism from that quarter, too, and not just our contrarian friends. (Just think of the woooo impact of Quantum Mechanics. As Terry Pratchett says 'It's Quantum'!)

    Let's face it, if it doesn't hold up, we'll get triumphalism anyway (in fact, that's what Watts comments thread is full of, with the occasional brave soul pointing out that he/she thought they were all supposed to be, um, 'skeptical'!)

    Yet again: hundreds of papers arising from years of hard-won science that builds on findings dating back over a century - it's all BS mate, crap! Particularly all that dodgy paleo crap and expecting us to believe minute trace gases make any difference. But give 'em one paper based on paleo reconstructions of the impact of rays from the outer reaches of the universe - doubts, who has doubts?

    Hypocrisy and just plain silliness I can identify; but me, I make no claims to being able to assess the science, hence my bringing it up here.
  15. Svensmark must have read 'Star-Begotten' by HG Wells. However, Watts can in no way take the role of the 'quiet little man'.

    ‘Those cosmic rays of yours,’ he said. ‘They are the most difficult part of your story. They aren’t radiations. They aren’t protons. What are they? They go sleeting through the universe incessantly, day and night, going from nowhere to nowhere. For the life of me I find that hard to imagine.’

    ‘They must come from somewhere,’ said a quiet little man with an air of producing a very special contribution to the discussion.

    And when all other arguments against AGW have failed, they invoke a mystery.

    ‘And so, having eliminated everything else,’ said the barrister, ‘you lay the burden of change and mutation — and in fact all the responsibility for evolution — on those little cosmic rays! Countless myriads fly by and miss. Then one hits — Ping! Ping!— and we get a double-headed calf or a superman.’
  16. My first censorship and I give credit to the great work you have been doing at Skeptical Science. I thought the view that SKS are propagandists might interest the group. Attempting to show GSR's would actually have been a cooling effect I believe is what did not go well with him.


    Note to renewableguy: I have deleted your comment on GCR because it is irrelevant and misleading, and shows that neither you nor the propagandists at skeptical science have read the paper. Had you read the paper you would see the explanation.

    I doubt very much there is a connection between life thriving on earth and galactic cosmic rays. Misleading is actually wrong and it shouldn't be your opinion alone to determine that. I presented an article based on several data sources explaining their point on GCR's.
    Proganda would be based on countering the truth with possibly false information. You are showing yourself to be using strong arm tactics unnecessarily. If you are interested in a fair presentation of both sides then put my article back up. If you only want to present one side, then by all means keep my post off.
    Skeptical science bases their postings on the current science.And yet you base your articles on the latest denial of AGW in the right wing circulation of entirely wrong and false media hype.
    The scientist refuted this false information very quickly. Your conclusion of medieval warming period was refuted by the very scientist that wrote it. This a true account of what has happened. Unless you would like to use your editorial power to rewrite that history.
  17. A couple of notes on Svensmark's latest. Let's start with the worst news:

    Origin of Cosmic Rays Not What Was Thought Results announced at nearly the same time as Svensmark's paper show that gamma ray bursts from supernovae are not associated with the expected neutrino flux. This calls into question the entire mechanism of cosmic ray origin underlying Svensmark's paper - as GRBs are clearly connected with supernovae.

    From the MNRAS announcement of Svensmark's paper:

    To obtain this result on the variety of life, or biodiversity, [Svensmark] followed the changing fortunes of the best-recorded fossils. These are from invertebrate animals in the sea, such as shrimps and octopuses, or the extinct trilobites and ammonites.

    So from the start, its clear that we're talking about life in the oceans only.

    They tended to be richest in their variety when continents were drifting apart and sea levels were high and less varied when the land masses gathered 250 million years ago into the supercontinent called Pangaea and the sea-level was lower.

    It's been known for quite some time that biodiversity diminished as shallow seas dried up during the formation of Pangaea.

    But this geophysical effect was not the whole story. When it is removed from the record of biodiversity, what remains corresponds closely to the changing rate of nearby stellar explosions, with the variety of life being greatest when supernovae are plentiful.

    When the primary driver is removed, what remains is a residual. Any detectable signal from this point forward is thus no more than a secondary mechanism and may in fact be contaminated with unexplained residuals from the primary.

    A likely reason, according to Prof. Svensmark, is that the cold climate associated with high supernova rates brings a greater variety of habitats between polar and equatorial regions, while the associated stresses of life prevent the ecosystems becoming too set in their ways.

    Svensmark's self-described 'innovation' is that cosmic rays from close supernovae cool so extensively that they cause glaciation and the associated sea level drop. This speculative leap requires acceptance of his as yet unsubstantiated model (cosmic ray ionization -> clouds -> observable cooling). However, there's a hidden contradiction here: supernovae (and the resulting colder climates) did not 'help life to thrive' (as claimed); colder climates produced greater environmental stress, resulting in higher extinction rates.

    The highest supernova frequency shown by Svensmark is a broad band from 300-250 million years bp, during the Permian. At the end of this period (252 MYBP), the greatest mass extinction event known on Earth occurred. Does 'thriving' equate to mass extinction? Or was it the end of the 50 million years of stressful cosmic ray-induced cold climate that caused the extinction? Is it chicken or egg?

    It is interesting to note as well that Svensmark is the sole author on this paper. But they laughed at Galileo...

    BTW, one aspect of propaganda is that it is "repeated and dispersed over a wide variety of media in order to create the desired result in audience attitudes." Searching "svensmark cosmic rays life" returns a 'wide variety of media' indeed: WUWT, Nigel Calder, The Register, The Daily Mail, etc.
    Response: [Riccardo] link fixed
  18. muoncounter:

    But what about the Battlestar Gallactica effect?
  19. Move over, galactic cosmic rays! Bring on the 'blazars:'

    ... black holes can emit high-energy gamma rays and are then called blazars. ... This particular radiation interacts with the optical light that is emitted by galaxies, transforming it into the elementary particles electrons and positrons. Initially, these elementary particles move almost at the speed of light. But as they are slowed down by the ambient diffuse gas, their energy is converted into heat, just like in other braking processes.

    The process of converting electron/positron kinetic energy into heat by 'braking' seems a bit mysterious. But have no doubt, the 'ABC' crowd will spin this into their next version of 'the answer.'
  20. Rawls writes on WUWT:

    "In effect they are claiming that you can’t heat a pot of water by turning the burner to maximum and leaving it there, that you have to keep turning the flame up to get continued warming, an un-scientific absurdity that I have been writing about for several years (most recently in my post about Isaac Held’s bogus 2-box model of ocean equilibration)."

    Does someone have a precise explanation of what Rawls apparently misunderstands about the science when making this analogy?

    My impressions are as follows (I have a mechanical engineering degree with a loose focus on the thermal side of things, so I have better than a layman's understanding of heat transfer, but I am no more than a casual student of climate science):

    1) When you heat a pot of water, it DOES stop getting hotter when the water reaches 100 deg C, as the temperature of liquid water cannot physically go above that. More importantly, the reason why the water can keep absorbing heat without any increase in temperature is that it is giving up thermal energy at the same rate that it is being absorbed, in the form of the latent heat of vaporization of the water vapor that escapes the pot! When that vapor touches something cooler and condenses, it will pass that latent heat of vaporization back to whatever it touches. If you do happen to increase the flame level, one thing that you will notice is that the steam escapes more quickly, to account for the fact that the water temperature can't go up any more, and a thermal energy balance must nonetheless be maintained.

    2) Even if Rawls had picked an simpler example without physical phase change, like heating an empty pot, that too would eventually reach an equilibrium temperature for a given flame level. This would happen because the higher the temperature of the pot, the more heat it gives off by convection. Thus, when the rate of convection of heat from the surfaces of the pot into the surrounding air became equal to the forced rate of heat transfer into the pot from the flame, the temperature of the pot would stop rising. So his basic premise, that it would be absurd to think you have to keep increasing the flame level to raise the temperature of something you are heating, is false: eventually the object stops getting hotter, and you DO have to raise the flame level!

    3) Giving Rawls the benefit of the doubt that he understands the law of conservation of thermal energy within a control volume, he seems to be implying that climate scientists have failed to account for the Earth's ability to respond relatively quickly (i.e., in significantly less time than 50 years) to whatever amount of forcing resulted from the increase in TSI that occurred before it remained generally flat 50 years ago, and reaching an equilibrium vis-a-vis that forcing long before now, so that effects of that forcing delayed by 50 years cannot explain the current warming.

    Rawls' attack doesn't pass my smell test, and I trust that climate scientists are in fact very familiar with and have accounted for the lag between a step or ramp up in TSI and its observed effects on global temperatures. Can somebody address that succinctly, in a way that would help somebody who is not necessarily so scientifically inclined to understand why they should trust that scientists have taken any "lag" effect into account?
  21. For those interested, I looked back and now see that comment 12 above addresses the denier argument that the effects of TSI could be lagging, and includes a hyperlink to a more detailed explanation.
  22. Update 2012: RealClimate posted "A review of cosmic rays and climate: a cluttered story of little success."
  23. There are quite visible correlations (link to image) between the two curves. The cycle duration is 11 years. This is the solar spot observation periodicity as known for several hundreds of years already. Even the well known fact that the solar cycle that should have started at about the millenium change came a bit late is seemingly reflected in the curves.

  24. IIUC, you are denying the scientific hypothesis that there is a correlation between sunspot numbers and climate on earth.  Your argument appears to be that because this hypothesis doesn't account for all global warming, that it doesn't account for any global warming.  That is both unscientific and fallacious reasoning.

    We have history that provides strong evidence that this hypothesis is correct.  The Maunder Minimum and the Little Ice Age being most significant.  Still, it is true that we do not completely understand the action mechiism.

    You are correct to point out that this correlation broke in the second half of the 20th century.  However, since it has been so strong historically, it is more reasonable from a scientific point of view to try to figure out why the correlation broke than to use this fact to try to prove that the hypothesis is false.

    Might I suggest one possible cause which is CFCs.  It is now belived that CFCs had a stronger effect on global warming than was once thought and their concentration in the atmosphere, taken as a factor (possibly with a delay in time) allong with the sunspot number as a proxy for solar activity in factor analysis might yield a reasonable answer to the question.

  25. JRT256: Firstly sun-spot numbers are correlated with total solar irradiance (TSI) as well as cosmic rays.  So a correllation between sunspot numbers and climate does not necessarily involve cosmic rays as the causal mechanism.

    Secondly, a link was provided to the "body of scientific research has determined that GCRs are actually not very effective at seeding clouds."  (i.e. the advanced version of the article).  The cosmic ray theory is not unlikely to be correct because it doesn't explain all warming, but because of the scientific research that has been performed has identified several problems with the causal mechanism,  If you want to discuss the details of any of the papers mentioned, I'm sure there will be plenty of contributors willing to discuss them with you.

    "it is more reasonable from a scientific point of view to try to figure out why the correlation broke than to use this fact to try to prove that the hypothesis is false."

    Actually, the most plausible theory is that there is more than one forcing that affects climate; changes in total solar irradiance and the rise in greenhouse gasses explains the breakdown in the correlation pretty well.  However, proving hypotheses to be incorrect is a fundamental part of scientific method.  Ruling out hypotheses is a good a way of finding out why the correllation broke down as any.

    Lastly, as a word of advice, if you want to have a discussion of science, starting by using phrases such as "That is both unscientific and fallacious reasoning." when you yourself obviously have not understand the argument put forward in the article is unlikely to be conducive to constructive dialogue.  Note I have taken pains to reply in a rather more civil manner.

  26. I was wondering if someone with a stronger background in physics than I could help place this new discovery into the broader context of the scientific knowledge of climate change. I can't say I agree with Dr. Lu's assertion that CFCs are the sole cause, and that CO2 can be ruled out, but that degree of correlation within Antarctica certainly does present a strong argument.

    Could it be possible that the link between CFCs and cosmic rays does indeed play a strong role in determining Antarctic temperatures, even if the role in the global climate system is less pronounced?

  27. DMCarey, as I was trying to answer that same question, I discovered other commenters in other threads here at Skeptical Science already had answered.  (What a team!) 

    This is merely Lu recycling the same claims he has been making for years. His claims have been proven wrong repeatedly. RealClimate has a short critique with a link to a peer-reviewed critique.

    And see the It's CFCs entry here at Skeptical Science.

  28. Tom,

    Thanks for the quick reply! The answer is much appreciated.

    uWaterloo is my alma mater, making it kind of disappointing to realize there is a professor there continuing to assert claims when faced with evidence that it's incorrect

  29. I am a bit confused by this page, as the basic and advanced versions seem to contradict each other. From the former:

    "Cosmic ray counts have increased over the past 50 years, so if they do influence global temperatures, they are having a cooling effect."

    And from the latter:

    "Cosmic ray flux on Earth has been monitored since the mid-20th century, and has shown no significant trend over that period."

    So my questions are whether this is, as it appears, a contradiction, and if so, which one's correct and can the one that's incorrect be changed?

  30. jsmith @79, if you read further into the advanced version, you will find it later refers to a record high GCR flux; after which it shows the same diagram used in the basic version, showing the same decline in inverted neutrino flux.  The key point is that while GCRs have increased over time, the increase is not statistically significant.  Consequently there is no contradiction between the advanced version and the basic version, nor internal inconsistency in the advanced version. 

  31. Here's the latest "knock down evidence" against AGW theory from the skeptic camp. Have you guys seen this one yet? I fail to see this as overwhelming evidence that cosmic rays are the main driver of the recent warming, but I'm just a layperson so maybe I'm missing something. Anyone care to comment on this? Thanks!

Prev  1  2  

Post a Comment

Political, off-topic or ad hominem comments will be deleted. Comments Policy...

You need to be logged in to post a comment. Login via the left margin or if you're new, register here.

Link to this page

The Consensus Project Website



(free to republish)



The Scientific Guide to
Global Warming Skepticism

Smartphone Apps


© Copyright 2015 John Cook
Home | Links | Translations | About Us | Contact Us