Solar activity measured by isotope proxies revealed the end of 20th century was the highest activity in 1200 years
A 2010 paper (that I somehow missed) was recently highlighted by the blog The Hockey Schtick and I thought it worth mentioning here even if a bit past the publish date.
The work by Ilya G. Usoskin of the Sodankyla Geophysical Observatory at the University of Oulu, Finland was published in Living Reviews of Solar Physics. The paper examines records from two isotope proxies (Be10 and C14) and finds that solar activity at the end of the 20th century was at the highest levels of the past 1200 years. Excerpts follow along with a link to the full paper.
A History of Solar Activity over Millennia
Ilya G. Usoskin, Sodankyla Geophysical Observatory (Oulu unit), University of Oulu, Finland
Abstract:
Presented here is a review of present knowledge of the long-term behavior of solar activity on a multi-millennial timescale, as reconstructed using the indirect proxy method. The concept of solar activity is discussed along with an overview of the special indices used to quantify different aspects of variable solar activity, with special emphasis upon sunspot number.
Over long timescales, quantitative information about past solar activity can only be obtained using a method based upon indirect proxy, such as the cosmogenic isotopes 14C and 10Be in natural stratified archives (e.g., tree rings or ice cores). We give an historical overview of the development of the proxy-based method for past solar-activity reconstruction over millennia, as well as a description of the modern state. Special attention is paid to the verification and cross-calibration of reconstructions. It is argued that this method of cosmogenic isotopes makes a solid basis for studies of solar variability in the past on a long timescale (centuries to
millennia) during the Holocene.
A separate section is devoted to reconstructions of strong solar–energetic-particle (SEP) events in the past, that suggest that the present-day average SEP flux is broadly consistent with estimates on longer timescales, and that the occurrence of extra-strong events is unlikely. Finally, the main features of the long-term evolution of solar magnetic activity, including the statistics of grand minima and maxima occurrence, are summarized and their possible implications, especially for solar/stellar dynamo theory, are discussed.
…
4.4 Grand maxima of solar activity
4.4.1 The modern episode of active sun
We have been presently living in a period of very high sun activity with a level of activity that is unprecedentedly high for the last few centuries covered by direct solar observation. The sunspot number was growing rapidly between 1900 and 1940, with more than a doubling average group sunspot number, and has remained at that high level until recently (see Figure 1). Note that growth comes entirely from raising the cycle maximum amplitude, while sunspot activity always returns to a very low level around solar cycle minima. While the average group sunspot number for the period 1750 – 1900 was 35 ± 9 (39 ± 6, if the Dalton minimum in 1797 – 1828 is not counted), it stands high at the level of 75 ± 3 since 1950. Therefore the modern active sun episode, which started in the 1940s, can be regarded as the modern grand maximum of solar activity, as opposed to a grand minimum (Wilson, 1988b).
Is such high solar activity typical or is it something extraordinary? While it is broadly agreed that the present active sun episode is a special phenomenon, the question of how (a)typical such upward bumps are from “normal” activity is a topic of hot debate.
…
6 Conclusions
In this review the present knowledge of long-term solar activity on a multi-millennial timescale, as reconstructed using the indirect proxy method, is discussed.
Although the concept of solar activity is intuitively understandable as a deviation from the “quiet” sun concept, there is no clear definition for it, and different indices have been proposed to quantify different aspects of variable solar activity. One of the most common and practical indices is sunspot number, which forms the longest available series of direct scientific observations. While all other indices have a high correlation with sunspot numbers, dominated by the 11-year cycle, the relationship between them at other timescales (short and long-term trends) may vary to a great extent.
On longer timescales, quantitative information of past solar activity can only be obtained using the method based upon indirect proxy, i.e., quantitative parameters, which can be measured nowadays but represent the signatures, stored in natural archives, of the different effects of solar magnetic activity in the past. Such traceable signatures can be related to nuclear or chemical effects caused by cosmic rays in the Earth’s atmosphere, lunar rocks or meteorites. The most common proxy of solar activity is formed by data from the cosmogenic radionuclides, 10Be and 14C, produced by cosmic rays in the Earth’s atmosphere and stored in independently-dated stratified natural archives, such as tree rings or ice cores. Using a recently-developed physics-based model it is now possible to reconstruct the temporal behavior of solar activity in the past, over many millennia. The most robust results can be obtained for the Holocene epoch, which started more than 11,000 years ago, whose stable climate minimizes possible uncertainties in the reconstruction.
An indirect verification of long-term solar-activity reconstructions supports their veracity and confirms that variations of cosmogenic nuclides on the long-term scale (centuries to millennia) during the Holocene make a solid basis for studies of solar variability in the past. However, such reconstructions may still contain systematic uncertainties related to unknown changes in the geomagnetic field or climate of the past, especially in the early part of the Holocene.
Measurements of nitrates in polar ice allow the reconstruction of strong solar energetic particle (SEP) events in the past, over the five past centuries. Together with independent measurements of the concentration of different cosmogenic isotopes in lunar and meteoritic rocks, it leads to estimates of the SEP flux on different timescales. Directly space-borne-measured SEP flux for recent decades is broadly consistent with estimates on longer timescales – up to millions of years, and the occurrence of extra-strong events is unlikely.
In general, the following main features are observed in the long-term evolution of solar magnetic activity.
• Solar activity is dominated by the 11-year Schwabe cycle on an interannual timescale. Some additional longer characteristic times can be found, including the Gleissberg secular cycle, de Vries/Suess cycle, and a quasi-cycle of 2000 – 2400 years. However, all these longer cycles are intermittent and cannot be regarded as strict phase-locked periodicities.
• One of the main features of long-term solar activity is that it contains an essential chaotic/stochastic component, which leads to irregular variations and makes solar-activity predictions impossible for a scale exceeding one solar cycle.
• The sun spends about 70% of its time at moderate magnetic activity levels, about 15 – 20% of its time in a grand minimum and about 10 – 15% in a grand maximum. Modern solar activity corresponds to a grand maximum.
• Grand minima are a typical but rare phenomena in solar behavior. Their occurrence appears not periodically, but rather as the result of a chaotic process within clusters separated by 2000 – 2500 years. Grand minima tend to be of two distinct types: short (Maunder-like) and longer (Sp¨orer-like).
• The modern level of solar activity (after the 1940s) is very high, corresponding to a grand maximum. Grand maxima are also rare and irregularly occurring events, though the exact rate of their occurrence is still a subject of debates. These observational features of the long-term behavior of solar activity have important implications, especially for the development of theoretical solar-dynamo models and for solar-terrestrial studies.
Full paper here: A History of Solar Activity over Millennia (PDF)
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However, according to the IPCC, none of this has nothing to do with 0.7C of global warming since the end of the Little Ice Age in 1850. And, even if you were to point it out to them for AR5, they have now clearly demonstrated they have no intention of paying any attention to any factual data that doesn’t fit the ‘CO2 and nothing else’ meme.
I don’t see how the discussion can so quickly turn to Earth’s temperature. It’s own variability, short term and long term, produces such fluctuating noise that any Solar affects will be buried in it. I prefer to stick to the paper at hand in our discussion. Confounding it with Earth’s temperature just messes up the flow.
I am surprised to see this old paper as a new topic on WUWT, but it has some useful data. The authors use the INTCAL98 data that I also used in my paper as a reasonably good record of the repeating nature of grand minima, but they make two rather large mistakes. The record after 1950 is very suspect and their blue line depicting grand minima is way too low.
REPLY: I missed the paper the first time around, so it is “news” to me. – Anthony
@Leif Svalgaard
>About the Beryllium record:
http://www.leif.org/EOS/2009GL038004-Berggren.pdf
“Recent 10Be values are low; however, they do not indicate unusually high recent solar activity compared to the last 600 years.”
++++
Thanks for the link. The paper addresses the issue you raise before about wind-blown 10Be and puts a tentative figure on it (30%).
“…they do not indicate unusually high…” Well, yeah, but they also indicate ‘pretty high’ values, you could even say, ‘equal to the highest’ values present in the record. Looking at Figure 1 it is pretty clear your definition of ‘unusually high’ must mean ‘pretty goldarned high’ because the 10Be concentration drops a lot.
With reference to the paper above, there is certainly support in doi:10.1029/2009GL038004, 2009 for the idea that solar activity has been ‘higher lately’ than before (say 120 years before) and I concluded that the warming observed from 1975-1998 has been almost entirely caused by this. Given the quite separate demonstrations that there are significant negative temperature feedback mechanisms in the atmosphere, the attribution of global warming during that recent period is unlikely to have been caused principally by fossil-fuel sourced anthropogenic emissions of CO2 and land use changes, p = <0.05. Until the temperatures are corrected for solar activity, the AG component will remain undetectable. As the IPCC denies any meaningful solar component, don't expect much from AR5.
PS Where did I get that p value? I made it up! It is my opinion. After all, this is climate! Dr Bill Mollison told me that 87% of statistics were made up and I still believe him. :~)
Notice the large gap between the Medieval warm Period temperature anomaly and the 10Be sunspot proxy. It’s almost comical. (hmm… I wonder if Solanki works for NOAA!)
The figure 17 that Anthony quotes from this Usoskin 2008/2010 paper is the same as figure 3 from Usoskin’s 2007 paper on grand maxima and minima:
http://cc.oulu.fi/~usoskin/personal/aa7704-07.pdf
The 2008/2010 paper is written as a survey paper and it provides a lot of background on the isotope proxies, the process of deposition, and factors that have to be accounted to use them accurately, but at least as far as Usoskin’s own work, this background is not affecting his results, but is just giving a fuller picture of how they were arrived at.
In particular, both papers list the modern grand maximum as 80 years in duration, centered on 1960, and neither paper makes any ridiculous claims that late 20th century warming couldn’t have been caused by the extraordinarily high level of solar activity because solar activity did not KEEP going up (something Usoskin and his co-author Solanki have both done elsewhere, like at the end of the abstract of this 2005 paper).
Good find Anthony!
Solanki et al., 2004. “Although the rarity of the current episode of high average sunspot numbers may indicate that the Sun has contributed to the unusual climate change during the twentieth century, we point out that solar variability is unlikely to have been the dominant cause of the strong warming during the past three decades.”
http://www.ncdc.noaa.gov/paleo/pubs/solanki2004/solanki2004.html
Solanki over at Max Planck had this figured out long ago.
http://i42.tinypic.com/2v8pr49.jpg
Thanks to Sparks for citing yet another paper where Usoskin and Solanki claim that it is the rate of change in solar activity that causes warming, not the level of solar activity. You know, like if you want to heat a pot of water on a stove you have to turn the flame up sloooooowly. If you just set the flame on maximum and leave it there, the pot won’t heat. Everybody knows that.
Leif, loved the sunspot count synopsis. Keeper.
Leif Svalgaard says:
So, Leif, what is your overall evaluation of this paper, conclusions, etc., if you have developed such at this point?
To be specific, the 2004 paper that Sparks cites for the Solanki-Usokin conclusion that the sun can’t have caused recent warming cites in turn for this conclusion a 2004 paper by Solanki and Krivova. Here is excerpt from the Max Planck Institute’s summary of the Solanki-Krivova findings:
The sun was at maximum levels, but those levels were not continuing to rise, hence they could not have caused warming. “Post-normal science” at work.
“In contrast, the Earth has warmed up considerably within this time period. This means that the Sun is not the cause of the present global warming.”
That was of course before they took cloud cover into consideration and still approaches solar influence as being one of varying wattage, not varying insulation or shade. The NOAA conclusion is Fred Flintstone Science.
Alec Rawls says:
September 14, 2012 at 9:50 am
Thanks for clearing that up 🙂
Jim G says:
September 14, 2012 at 9:45 am
So, Leif, what is your overall evaluation of this paper, conclusions, etc., if you have developed such at this point?
The high values the past hundred years are caused by the use of the Group Sunspot Number. Just about everybody working on long-term solar activity are participating in two workshops I am leading [with a number of co-conveners]: The sunspot workshops http://ssnworkshop.wikia.com/wiki/Home and the solar activity workshop http://www.leif.org/research/Svalgaard_ISSI_Proposal_Base.pdf
The workshops are ongoing. A preliminary summary/discussion is supplied by Hugh Hudson: http://www.leif.org/research/SSN/Hudson.pdf
One of the conclusions we are coming to is to “Reject the Group Sunspot Number approach”
And therefore reject 10Be? I don’t think so.
Leif Svalgaard says:
September 14, 2012 at 11:58 am
RE: One of the conclusions we are coming to is to “Reject the Group Sunspot Number approach”
Will the sunspot number be calculated by individual sunspots by satellite?
The reason for using that formula in the past is for observing conditions that are less than ideal and where small spots are hard to see from ground based observatories.
Will small spots that were hard to see from ground based observatories be rejected from satellite data and or be added to the past as a new formula?
Crispin, Leif and others thanks for comments.
Leif Svalgaard says
Thanks. Your links, in themselves, a very interesting read. Apparently a “work in progress” at this time. I see that, as per our last discussion, we go back to the adjustment of he older “raw” SSN’s using the “group” number.
… a topic of hot debate. …
New keyboard time, clean shirt needed. Oof.
You do realize this might signal the end of this inter-glacial warm period, right? I sure hope not.
I would take this paper with a large grain of salt. Note that the graphs show quite low solar activity corresponding to the Medieval Warm Period; so how do we explain that? Similarly for the Roman Warm Period.
Mike Haseler says:
September 14, 2012 at 1:58 am
Be-10 is generally produced by cosmic ray bombardment of N14 or O16. It is also the result bombardment of C13 by lower energy neutrons during H-bomb tests. The important point about the tests is that open-air tests took place from about 1950 to 1980. That is an extremely limited temporal window. Unlike (presumably) C-14, Be-10 is rapidly scavenged from the atmosphere by rainfall. If you have followed the climate free-for-all, there is some question about the residency time of CO2 in the atmosphere.
Chris R. says:
September 14, 2012 at 2:36 pm
I would take this paper with a large grain of salt. Note that the graphs show quite low solar activity corresponding to the Medieval Warm Period; so how do we explain that?
That solar activity has little or no influence on climate variability, perhaps?
Alec Rawls says:
September 14, 2012 at 9:23 am
If you just set the flame on maximum and leave it there, the pot won’t heat. Everybody knows that.
I don’t know that. When I start the pot in the mornig on maximum in order to get hot water for my tea and to boil my eggs, it works great for me. I get hot tea and boiled eggs in minimum time. If I turn down the heat, it takes longer…
Sparks says:
September 14, 2012 at 1:01 pm
Will small spots that were hard to see from ground based observatories be rejected from satellite data and or be added to the past as a new formula?
The issue is not the difference between ground-based and satellite data [the solar-observing satellites have rather smnall telescopes – a weight issue and a heating issue]. There are stong indications that we are losing the small spots so that the sunspot number may soon become a poor measure of solar activity. One of our goals is to decide how [and what] to count in the future.
Jim G says:
September 14, 2012 at 1:42 pm
I see that, as per our last discussion, we go back to the adjustment of the older “raw” SSN’s using the “group” number.
Actually, not. We instead abadon the older group numbers. The calibration [‘adjustment’ as you call it – which is a bad terminology as we are calibratinf against a well-observed, objective, and well-understood independent measurement: the daily variation of the geomagnetic field [discovered in 1722].
Ooh I wish this was real.