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Climate Hustle

Stauning and Friis-Christensen on Solar Cycle Length and Global Warming

Posted on 22 March 2012 by Klaus Flemløse

In the scientific debate on global warming and the sun/cosmic rays relations, Friis-Christensen et al. have produced several fascinating and inspiring ideas. New and alternative ideas are always welcome and they deserve recognition for their contribution. Not all ideas have passed the test by the scientific community. However, it is clear that they have started a scientific debate and as well as a blog debate on solar influence and cosmic rays.

Friis-Christensen et al. investigated the relation between solar cycle length and global temperature in their 1991 paper. They found a close relation between solar cycle length and global temperature for the years 1850-1985. As I understand it, they have been doing a data mining exercise and found this relation. However, their result could not be supported by scientific evidence. Data mining is OK in some cases, but there is a risk to detect flawed relations. The result was consequently challenged by Peter Laut in 2003. Peter Laut has publicly criticized Friis-Christensen for adjusting data in an improper way. As a consequence there was a heated debate.

Recently P. Stauning has produced a paper where he has updated data and expanded same graphics, now from 1850 to 2005, and corrected the calculation errors of Friis-Christensen et al. The result of this update is that the close relation from 1850 through 1985 has stopped and from 1985 the solar cycle length curve and the temperature curve are diverging.

Stuauning 2011

Figure 1: Solar cycle length (red) vs Northern Hemisphere temperature (blue) (Stauning 2011).The number of sunspots has a minimum and a maximum. The solar cycle length can be found in two ways. Either as the difference between two successive dates on which the number of sunspots show a minimum or as the difference between two successive dates on which the number of sunspots shows a maximum. The first number is indicated in the legend as “min-to-min” and the second as “max-to-max” in red color.The temperatures on the minimum dates and the maximum dates are indicated in the legend as “min-to-min” and “max-to-max” in blue color.

This shows that the hypothesis based on data mining - put forward by Friis-Christensen et al – had been falsified. There could be other explanations for a relation between global temperature and the sun, so the debate on sun/climate relations will continue, but one of the branches of sun/climate debate has now been cut off.

The Friis-Christensen (1991) paper has been used again and again by the climate deniers without any protest from Friis-Christensen et al. The paper by P. Stauning will hopefully prevent the deniers from using the Friis-Christensen graphs in the future.

The paper by P. Stauning is an investigation in general of the sun/climate relations and the Friis-Christensen case is only a minor part of his interesting paper. P. Stauning’s paper deserves attention from readers of Skeptical Science.

However, I would like to express my thank you to Friis-Christensen and his team for their contribution to climate science in the past. Hopefully he and his team will publish both verifications and falsifications in the future.


Stauning,P (2011): Solar activity-climate relations: A different approach. J.Atm.Solar-Terr.Phys. 73, 1999-2012.

Laut,Peter (2003):Solar activity and terrestrial climate: an analysis of some purported correlations. J.Atmos.Solar-Terr.Phys 65, 801– 812

Friis-Christensen, E. Lassen (1991): Length of the Solar Cycle: An indicator of solar activity closely associated with climate, Science, New Series, Vol.254, 698-700

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Comments 1 to 23:

  1. Sadly, it won't phase the deniers, because they're not interested in the science, just the denial.
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  2. I always find it particularly concerning when I see charts showing the correlation between solar and T followed by the divergence of the two. The first thing that pops into my head is, T would be rising much faster if solar forcing had not been falling so precipitously. And it holds the chance that solar output will kick back in and push T even higher and faster.

    Nice update, though. Do I think "skeptics" will stop making the claim? Unlikely. Facts rarely get in their way.
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  3. Previous SKS article
    What does Solar Cycle Length tell us about the sun's role in global warming?
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  4. Thanks for this solar update. I suppose it is natural for scientists in the Nordic countries to have a special interest in the sun :) and I'm glad to see Skeptical Science being as global as possible. Many interesting figures from Stauning's paper are available here in small size.
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  5. Thanks for the article. So the correction is that solar cycle length and temperature stop correlating after about 1977 or so, instead of 1985? Seems to me that this "skeptic" argument is/ was weak after maybe a decade or so after the Friis-Christensen (1991) paper, and would be even weaker today - even if the 1991 paper was not falsified.
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  6. I have been studying the relationship between SSL and global temperatures for years and have known about both the seemingly close correlation that seems to exist prior to about 1980, as well as the strong disconnect that occurred after that point. Of course, as pointed out, there are other potential solar influences outside of SSL that could show covariance with SSL, such as EUV's, so more research is certainly quite warranted. But what should be most obvious is that some other signficant forcing is now driving climate on a longer-term basis, such that solar, ENSO, and aersols and other natural variability are now playing a secondary role as "noise" that rides upon a much stronger signal. That signal of course is the forcing from the additional CO2, N20, and methane that are now at their highest levels in probably at least several million years.

    One final side-note to the SSL/Climate connection. If we believe there was some correlation in the past (prior to the large influx of anthropogenic GH gases), then we might rightly beleive that at least a Dalton and possible Maunder type cooling would be in the offing in the next few decades as SSL look to be lengthening for many decades. That we will likely not be seeing this cooling-- indeed, quite the opposite, speaks both to the strength of the anthropogenic signal, but also, to the rather tenous nature of the connection between SSL and climate.
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  7. Roger, actually I'd say it was weak when they wrote it. If you look at the 'correlation' they initially found you'll see that there is no 'consistency of change'. That is, about half the time cycle length went up temperature went down - or vice versa. The only period where they both head in the same direction for any appreciable length of time is the rise in both between ~1910 and ~1940.

    So let's say we're looking at two sets of data and we see that both rose over the same time period. If we then plot them on the same graph and set the scales of each such that these rises appear to be parallel we can create an apparent 'correlation'. However, while the years before and after that period aren't wildly wrong, they don't show any strong correlation either. If there were a tight enough correspondence between these factors for the 1910-1940 cycle length rise to cause the temperature rise (or vice versa, which makes about as much physical sense) then we shouldn't be seeing the sharply inverse responses in some of the preceding and subsequent cycles.

    It is just a form of 'curve fitting'... which falls apart once you look outside the bounds which have been fit to 'correspond'. Just as the past 30 years show wild divergence you'd get the same going back before 1850. For example, solar cycle 4 around 1790 was 13.7 years long... that's way off the bottom of the chart. Meanwhile, solar cycle 8, at 9.8 years ~1840, was shorter than any of those shown on the chart and thus should have had the highest temperature anomaly... but there is no indication of sudden extreme heat in the 1840s and then immediately returning to globally colder temperatures.
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  8. Actually, Friis-Christensen made a mistake in his 1991 paper, when calculating the length of the last solar cycles. When corrected, the divergence is obvious.
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  9. Technically a more elegant and complete description would be that solar forcing is a driver of climate in the absence of other more important drivers - and it was so before 1800. It appears also well correlated from 1800 to about 1980 - since for that interval the (somehow weaker) CO2 forcing was largely canceled by the negative aerosol forcing and the direction of the remaining CO2 forcing and solar forcing were both in the same direction, but once the aerosol forcing becomes less visible and the sun is no longer increasing in TSI the divergence becomes obvious.
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  10. Actually, given the number of other drivers and the shape of human impact on the biosphere before 1985, the solar correlation is very good. The divergence context here is the same as the divergence for tree rings ('the decline'), and the PDO -

    SKS - Temp v PDO

    Just off the SWAG, there are new factors that have caused "a disturbance in The Force". All the other factors are still there and still do their part - in fact, they may be good tests of the status of the imbalance.
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  11. R. Gates @ 6 and owl905 @ 10, I am drowning in acronym soup here.

    • SSL: I only know of this as Secure Sockets Layer

    • EUV: Google suggests "Extreme ultraviolet lithography" or "European University Viadrina"

    • SWAG: Google suggests "Scientific Wild Ass Guess" or "Stuff We All Get"

    Will someone please throw me a lifebelt?
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  12. @ Doug H

    Well I'm guessing SSL is Solar Cycle Length, but the author of that acronym tripped up phoenetically. As for the others? Well it's like lurking in millitary forums around here sometimes...
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  13. EUV is possibly 'emitted ultra violet' - but thats about all I can think of...

    But this makes little sense, as that's mostly intercepted high up in the atmosphere, and wouldn't play much of a role in observed ssurface temp IMO.
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  14. Time for a new image to be added to the expanding list?
         - Global Warming -
    How skeptics blame the sun
    How realists observe the role of the sun
    I think you all can imagine what image fit's this description...
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  15. I believe EUV is Extreme UV which means the high energy/short wavelength portion of the UV spectrum. I believe that there is some research linking variations in the sun's EUV emission with weather on Earth.

    SSL - I agree it is likely solar cycle length. Or alternately SunSpot Number. Either way, I'm pretty sure it's a typo.

    SWAG - I have no idea....
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  16. 70rn @ 12

    I couldn't agree more. It would be nice to have a glossary of all the abreviations, argot, etc. found on this site that one could turn to in order to clarify matters.
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    [DB] Glossary functionality nears completion.

  17. @Paul 15 - Doug H @ 11, first interpretation of SWAG is the correct ... G ... .
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  18. Yes, of course SSL was a typo in the context of this post and how rightly embarrassed I am. Just goes to show what happens when you deal with two somewhat related acronyms at around the same time! Our neighborhood is thinking of installing some of these in our park, and I'm on the committee looking into them:

    Solar Spot Lights, which I would take it, have no relationship to the past climate, nor would show covariance with past temperatures...but who knows, someone could probably find a correlation to Solar Spot Lights and global temps, or perhaps there is as much correlation as SCL's have!
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  19. owl905 @ 17 and R. Gates @ 18, thank you both for the clarifications. I'm relieved to see that I was not the only one suffering AD (Acronym DissonanceTM).

    For SSL, I should read "Solar Cycle Length";
    For SWAG, I should read "Scientific Wild Assed Guess".

    R. Gates, for EUV, should I read "Emitted UltraViolet" or "Extreme UltraViolet"? Perhaps you could shine the the Solar Spot Light on this for me "8-)
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  20. I'm glad to see that I'm not the only one stumped by acronyms. I'd like to suggest that all commenters define their acronyms at first use.
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  21. There was a nice response to the FC&L paper from CRU:

    Kelly and Wigley (1992) Solar cycle length, greenhouse forcing and global climate. Nature. 360, 328-330.

    Amongst other things, they struggled to recreate the cycle length data that was used by FC&L.
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  22. Aha: clearly a new case of divergence.
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  23. Looks to me like this paper might be relevant to claims of solar causality.
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