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  1. With all due respect, the main conclusions of the Feulner and Rahmstorf study seem not only self-evident, but something that can be worked out on the back of an envelope, at least to a good first approximation (especially when placing it in the context of a warming signal an order of magnitude greater by end century). For example, the Total Solar Irradiance around solar minimum is ~1360 W/m2 (Kopp and Lean, 2011), and estimates of the solar decline toward Maunder Minimum are of order ~0.1%, so the associated radiative forcing is 1360*0.001*(0.7/4) ~ 0.24 W/m2, which even at equilibrium is about 0.2 degrees C for a reasonable climate sensitivity. There’s no way to make that competitive with CO2 by end century even with [probably] unreasonable amplification factors.

    Another interesting question concerning a new Maunder Minimum would be the impacts on decadal-scale prediction, where both internal variability and changes in TSI are competitive with changing greenhouse gases.

    [Response: I agree with Chris that the simplest back-of-envelope argument is fully sufficient to make the point. It does seem though, that these days it is necessary to publish the obvious in repeatedly different and more catchy forms in order to get the word out. To get attention, a new paper, and new press release, is necessary, and besides that it appears that a lot of things that are well-known to everybody in climate science haven't been articulated in a conveniently citable form (though one can find estimates like Chris's embedded in various discussions of solar variability). The thing I find a bit curious about the result that is the subject of this blog article, though, is the statement that the model used reproduces the Little Ice Age climate simply as a response to the luminosity reduction. That is at odds with what one finds in GCM's, and is in fact what prompted the search (e.g. in Shindell's paper) for fancy amplifying mechanisms based on UV variability, ozone feedback and strat/trop coupling. So, the small reduction in warming in 2100 is fully expected and compatible with standard climate sensitivity arguments, but the statement that the same physics accounts for the Maunder Minimum response is not. I suppose it may have something to do with what one considers the LIA signal to actually be. It's fairly small in the global mean, but as a regional climate signal much bigger and hard to account for by insolation reduction, when put into full GCM's. Comments from the authors? --raypierre]

    [Response: Ray, we're discussing the global mean temperature response. The fact that a wide range of different models (including ours) give a reasonably good simulation of the past millennium with this forcing was already shown in the IPCC AR4, see Figs. 6.13 and 6.14. -stefan]

    [Response: Right, but does this really mean there's nothing left to explain about the LIA? Can you actually get the magnitude of the Northern Hemisphere regional response right just as a response to reduced luminosity? Again, the whole reason so many researchers are looking for more exotic mechanisms for the LIA is that it is hard to account for the magnitude of NH (especially European) expression of the LIA when forcing with just the straight luminosity reduction. I am willing to believe, however, that maybe some of what we call the LIA is within natural variability, and that the regional signal that needs to be explained is not as large as some think. --raypierre]

    Comment by Chris Colose — 19 Jun 2011 @ 11:15 PM

  2. “What’s Down with the Sun? Major Drop in Solar Activity Predicted”

    Do you have a good model for what goes on in the interior of the sun? Since 21st century instruments were not available in 1650, it seems to me that you need a good theory of the sun’s interior to make such a prediction. Relying on what can be seen on the solar surface and corona seems like weather forecasting.

    Thanks for the File:Sunspot Numbers.png graph and the 1000 year sunspot graph. I notice that the 1950s were a time of peak oscillations and also good economic times.

    Comment by Edward Greisch — 20 Jun 2011 @ 12:01 AM

  3. Unfortunately, direct observations of the Sun just before the Maunder Minimum were not frequent and precise enough to understand how the Sun entered into this prolonged minimum (in particular how the 11-yr sunspot cycle collapsed). Cosmogenic nuclides should teach us part of this story, but we still need a larger and more precise database in order to test if the present behavior of the Sun is indeed a good analog for the start of a Grand Minimum.

    Actually, the discovery of the Maunder Minimum should be attributed to the French astronomer Jean-Jacques Dortous de Mairan (1678-1771), who reported a link between solar activity, based on the abundance of sunspots, and the frequency of aurorae observed at mid-latitudes (e.g. in Paris or Montpellier). He described the concomitant decrease of both phenomena around 1645 and their subsequent increase around at the beginning of the 18th century during which he was living. This seventy year period of anomalous solar behavior was studied again more than a century later by Edward Maunder, whose name would ultimately be associated with this period by Jack Eddy.

    J.J.D. de Mairan, Traité Physique et Historique de l’Aurore Boréale, Imprimerie Royale, Paris, 1754, pp. 1–570, 1st édition 1733, 2nd edition.

    Comment by Edouard — 20 Jun 2011 @ 12:03 AM

  4. Interesting analysis. Politically, global warming will be a hard sell during the early years of a Maunder type minimum as temperatures take a several year rapid plunge (around 2020 on your chart). During that time, the idea of restricting the burning of fossil fuels could well lose its luster. In such an eventuality, we might find that CO2 levels are actually higher by 2100 than they would have been without a quiet sun period earlier in the century.

    [Response: Those sharp dips are from volcanic eruptions that were put in to make the scenarios more realistic (though of course no-one knows when the next big climate-affecting eruption will be). We should have made that clearer though. - gavin]

    Comment by R. Gates — 20 Jun 2011 @ 12:29 AM

  5. It is clear that if a grand minimum were to happen it would be a tremendously exciting opportunity for solar physicists, however it is unlikely to be very exciting for anyone else.

    I think that you underestimate how much interest there will be in comparing the measured temperature to the modeled temperature.

    [Response: Not at all. That is is always interesting (if done properly of course). But the 'excitement' generated by this story outside the solar physicist community seems almost entirely confined to the fringe who are predicting a new ice age. They will be sorely disappointed. - gavin]

    Comment by Septic Matthew — 20 Jun 2011 @ 2:01 AM

  6. Minimum of 1810 type is on cards, couple of low cycles, but nothing approaching the Maunder type minimum.
    http://www.vukcevic.talktalk.net/NFC7.htm
    http://www.vukcevic.talktalk.net/LFC2.htm
    There is no reasonable correlation between the longest temperature record (CET) and the sunspot activity.
    http://www.vukcevic.talktalk.net/CET-SSN.htm

    Comment by vukcevic — 20 Jun 2011 @ 2:24 AM

  7. Observations by Matthew Penn and William Livingston (refered to in Frank Hill and colleagues link, see above) is an interesting discovery, but conclusions drawn from it are by no way definitive. The effect may be associated with a deeper and longer minimum (as the current one is) but it appears that the effect may reversible; there some indication to that as shown here:
    http://www.vukcevic.talktalk.net/L&P.htm
    Next year or two may show true trend of this effect.

    Comment by vukcevic — 20 Jun 2011 @ 2:37 AM

  8. For those curious about the pronounced dips in the future scenarios here they are responses to Pinatubo-scale volcanic eruptions that are assumed to occur at a reasonable frequency over the course of the next century.

    I have to say that I was wondering whether anyone had done any such climate simulations when I heard the news, so thanks very much for the post. I think people would be a bit more interested in the difference over a decadal time-frame. You conclude that a 0.3K difference is the maximum you would expect by year 2100, but this is equivalent to about one decade of global warming at present rates [0.3K/decade?], so presumably this could create a one-decade pause in global warming were such a minimum to occur now.

    Of course, on a timescale of one decade the noise in the temperature signal from internal variability and measurement uncertainty is quite large, so this might be hard to determine, though tamino showed that five year means show a monotonic increase over recent decades, and one might not unreasonably expect this to cease for a decade in a grand solar minimum scenario.

    I’d be very interested to see the difference in a well-initialised decadal forecast between the two possibilities [grand solar minimum/solar business as usual].

    Comment by Timothy — 20 Jun 2011 @ 4:51 AM

  9. [R Gates] – “Politically, global warming will be a hard sell during the early years of a Maunder type minimum as temperatures take a several year rapid plunge (around 2020 on your chart)”

    See my post at 7 – this plunge is due to a volcanic eruption they’ve included in their scenario. Note that it is present in all the runs, not just those with a grand solar minimum. This confused me at first too, but Fig. 2 of the paper explains everything.

    As far as I was aware most climate model scenarios include a constant, small, forcing for volcanoes, rather than arbitrary, episodic forcing. It doesn’t make much difference to the 2100 temperatures, but it can make differences in the timeseries confusing.

    Comment by Timothy — 20 Jun 2011 @ 8:14 AM

  10. Even if there were a significant negative effect on the increasing temperature trend due to a cooler sun, we would still have the problem of “ocean acidification” from carbon dioxide added to the atmosphere. In fact the cooler the oceans are, the more rapidly carbon dioxide would dissolve into the water. Given the slow rate of temperature changes for large bodies of water and the tiny hypothetical effect of a cooler sun, I doubt that rates of ocean acidification would be affected much, but there would be some effect.

    It’s important to remember that greenhouse gases, particularly carbon dioxide, affect the biosphere in multiple ways. Looking at temperature trends alone misses much that is important. No matter what other factors affect temperature, the addition of large amounts of carbon dioxide to the atmosphere-ocean system will produce large negative effects.

    Comment by Robert Reiland — 20 Jun 2011 @ 8:34 AM

  11. two things:

    1-what about your graph?

    The A1B scenario warming, in 2100, is not 3.8°C but 2.8°C (see IPCC 2007)
    On your graph the cooling is only 0.1°C not 0.30°C as in the text.
    So there is an evident minoration of the “Maunder effect”

    2 this sentence:

    “It is clear that if a grand minimum were to happen it would be a tremendously exciting opportunity for solar physicists, however it is unlikely to be very exciting for anyone else”

    is, at least, understandable.

    A solar grand minimum should be exciting for climate scientists who are interested, by example, by the local effect (for winters in Europe and in the US)and many other effects in the stratosphere.

    Comment by meteor — 20 Jun 2011 @ 9:12 AM

  12. sorry, in my precedent post we must read “incomprehensible” not “understandable”

    Comment by meteor — 20 Jun 2011 @ 9:59 AM

  13. You include volcanic activity in the climate models. It appears you did not include a solar minimum. Why not?

    As for climate scientists being out of work in a solar minimum, me, I’m hiring people who understand how to warm up this joint.

    Comment by JCH — 20 Jun 2011 @ 11:33 AM

  14. This idea has been put forth previously, although compared to a Dalton-type minimum and not a Maunder-type.

    http://sesfoundation.org/dalton_minimum.pdf

    Comment by Dan H. — 20 Jun 2011 @ 1:25 PM

  15. It is worth noting that Theodor Landscheidt – one of iconoclasts in the ‘solar-forcing-trumps GHG’s’ school of European solar physicists – predicted this possible Grand Minimum based on the theory that Gliessberg cycles generated by the Sun’s oscillation around it’s centre of mass directly affect the Coriolis force perturbing solar plasma flow and the solar dynamo.
    He took to self-publishing through his own independent research institution rather than academia and peer review for this paper:

    http://www.schulphysik.de/klima/landscheidt/iceage.htm

    But on re reading it in my files he really does seem to have made a valid prediction and call on intensities of cycle 23 through and beyond 25 and the implications re a Grand Minimum.
    Indeed there had been a suggestion that should this hiatus in sun spots prevail it should be called the
    Landscheidt Minimum.

    Comment by Will Hansen — 20 Jun 2011 @ 1:45 PM

  16. JCH “It appears you did not include a solar minimum. Why not?”

    Why? Was there a solar minimum in C20?
    In 2010 was one predicted anywhere outside of the denialsphere?

    Why wasn’t an major asteroid-strike include as well?

    Comment by Jim Eager — 20 Jun 2011 @ 1:54 PM

  17. Will Hansen
    Theodor Landscheidt is a rather vague in comparison to the precision of the ‘Vukcevic formulae’
    http://www.vukcevic.talktalk.net/NFC7.htm
    http://www.vukcevic.talktalk.net/LFC2.htm

    Comment by vukcevic — 20 Jun 2011 @ 2:38 PM

  18. @grnhse_gas_bros says:
    shoutout to folks at RealClimate for clearly pointing out that SUN IS NOT STAR of show

    Comment by Prasad Kasibhat.a — 20 Jun 2011 @ 3:24 PM

  19. Of greater interest to me is the reduction of UV in a sunspot minimum. This must affect the upper atmosphere, so would there be an induced affect on the lower atmosphere?

    Comment by David Beach — 20 Jun 2011 @ 3:49 PM

  20. Figure 4 only shows the warming up to 2100, a mind boggling 4C in a century. Just what do the models predict for a much longer period? dT = 40C @ T=2300 ? By how much can the temperature really rise (theoretically)?

    Comment by H. Beijeman — 20 Jun 2011 @ 6:06 PM

  21. Dr. Schmidt,

    if I remember right, was it not you who suggested that with the dampening of the sunspots, TSI may even rise?

    Well it seems the Dr.Svalgaard thinks somewhat along the same lines. If I may –

    (Leif Svalgaard says:
    June 16, 2011 at 1:44 pm
    (Mark Wilson says:
    June 16, 2011 at 1:03 pm
    Of course nobody knows if the TSI during a grand minimum is equivalent to TSI at the bottom of normal cycle, or if it is lower.)

    If we assume that the L&P effect is that magnetic field does not concentrate into dark visible spots, variations of TSI which is normally composed of a darkening due to spots plus emission from the surrounding magnetic field areas [twice as much as the darkening] might miss the darkening effect [when there are no spots], so TSI during a Grand Minimum might be higher than TSI now.}

    I think that the ability to really test some hypothesis about a minimum is going to be very exciting!

    [Response: Not me. We talked about the temperatures going down potentially with higher sunspots based on the (possibly very dubious) spectral results reported in Haigh et al (2010) - but I think that is unlikely. Leif's point is interesting - but in itself not very convincing. Having a grand minimum happen would obviously clear things up considerably. - gavin]

    Comment by DeNihilist — 20 Jun 2011 @ 9:57 PM

  22. David Beach (#19)

    A great review on the various solar impacts on climate is by Gray et al (2010) available here [PDF]. Note that the UV variations are strongly disproportionate to the integrated TSI change, and can reach up to 100% variation (depending on the wavelength interval), ~6% at UV wavelengths in the stratosphere, and temperature anomalies of ~1000 K in the very uppermost regions of the atmosphere; section 4 of the Gray et al. paper discussed UV changes and stratospheric feedbacks.

    Another interesting question, on a larger planetary evolution scale, is the role of the very short wavelengths in eroding planetary atmospheres. The shortwave extreme ultraviolet flux is much higher in the distant past, which could pose problems for early Mars to develop a very dense CO2 atmosphere early on for example, since C and O could escape from Mars early in its history (driven by these energetic wavelengths).

    Comment by Chris Colose — 21 Jun 2011 @ 12:34 AM

  23. Re 15:

    Perhaps “Landscheidt Lessening” ?

    Comment by AIC — 21 Jun 2011 @ 2:10 AM

  24. So if this could be regarded as a good reconstruction (only the NH tropics I know) how much would it affect the possible contribution from the sun?

    http://journals.ametsoc.org/doi/abs/10.1175/2011JCLI4145.1

    Comment by Magnus W — 21 Jun 2011 @ 2:11 AM

  25. “You include volcanic activity in the climate models. It appears you did not include a solar minimum. Why not?”

    They did include a solar minimum, not only that they included one that lasts throughout most of the 21st century – far longer than the period of time that the Maunder minimum persisted.

    Comment by Timothy — 21 Jun 2011 @ 3:06 AM

  26. There is some research that links solar minimums to increased volcanic activity, which would have a much greater effect on climate temperatures than just solar activity.

    [Response: What possible mechanism could cause this? Any such coincidence is almost certainly just a coincidence. - gavin]

    Comment by stuart — 21 Jun 2011 @ 4:06 AM

  27. Forget the last question… this answers it
    http://journals.ametsoc.org/doi/pdf/10.1175/BAMS-D-10-05003.1

    Comment by Magnus W — 21 Jun 2011 @ 6:29 AM

  28. sorry, this:
    http://www.google.com/url?sa=D&q=http://www.people.fas.harvard.edu/~tingley/Comment_on_Christiansen.pdf

    Comment by Magnus W — 21 Jun 2011 @ 6:31 AM

  29. @1:

    You are right, of course, but this is true for any estimate of global temperature response to known forcing. If we had done a simple back-of-the-envelope estimate, surely someone would have criticized us for not using a climate model… Besides we also looked into regional patterns and the sea-ice response in our paper, something one cannot do without a climate model.

    @3:

    Thanks for the information about de Mairan, I was not aware of his work in this context.

    @11:

    On your first comment, part of the discrepancy between our model’s warming and the IPCC result is due to different reference periods. The IPCC uses the difference between the 2090-99 and 1980-1999 averages while we use anomalies relative to 1961-1990. The corresponding value for our model is 3.5°C warming. Furthermore, the value of 2.8°C you mentioned is the best estimate from an analysis of many different models, the likely temperature rise for the A1B scenario is given as 1.7-4.4°C by the IPCC, so our result is higher than the best estimate, but well within the range of all IPCC models. In any case, the thing we are most interested in is the solar-minimum induced cooling relative to the warming trend. The cooling in the graph shown is indeed 0.1°C only as you observed, the 0.3°C arises when we, conservatively, estimate all uncertainties in the modeling and the forcings. We should have explained that better. On your second comment, I agree, a 21st-century grand solar minimum would also be interesting for climate science as well. What we wanted to say is that the effect will be small.

    @13:

    The simulations do include solar forcing, of course. The solid lines represent experiments with a repeated 11-year cycle, the dashed lines those with a new grand minimum.

    Comment by Georg Feulner — 21 Jun 2011 @ 8:18 AM

  30. This blog still seems to insist on using obsolete solar activity data. I can understand the attraction. The apparent pick up in activity just after 1900 helps explain the strong warming in the early 20th century. Clearly ghg forcing cannot have been responsible. However, it’s now pretty obvious that activity has varied much less than implied by the old Lean and Hoyt/Schatten reconstructions.

    [Response: You are mistaken about what reconstructions were used. F&R used Bard et al 2000 and Wang et al (2005) (extended using 10Be reconstructions scaled to the Wang numbers at the MM). The latter reconstruction is inline with more recent work by Steinhilber et al (2009) and Viera et al (in press) (see my paper for comparisons). I agree that no-one should be using the older Lean (2000) or Hoyt/Schatten numbers any more- gavin]

    Isn’t it time to admit that you don’t actually know what caused a ~0.5 deg rise in global temperatures and a ~2 deg increase in arctic temperatures between ~1910 and ~1945.

    [Response: Odd that the only paper to make a connection between Arctic temperatures and solar activity (Soon, 2005) used the ...... Hoyt and Schatten reconstruction. Isn't that a little contradictory to your first point? - gavin]

    Comment by John Finn — 21 Jun 2011 @ 9:11 AM

  31. John Finn
    The Arctic temperature regime appear to be a very specific case, any generalisation may be misplaced:
    http://www.vukcevic.talktalk.net/NFC.htm

    Comment by vukcevic — 21 Jun 2011 @ 1:11 PM

  32. John Finn – If you tried a little investigation and thought you could address your own false accusation about early 20th century warming (and might not appear such a boor).

    I suspect you’re looking at the Hadcrut temperature data since that’s the one that gives “a ~0.5 deg rise in global temperatures”…”between ~1910 and ~1945″. It’s pertinent to your point that the global temperature drifted downwards a tad between 1880ish and 1910ish, a result most likely of the large volcanic activity in that period.

    So the marked early 20th century warming was likely a mixture of recovery from volcanic forcing and accumulated (but masked) greenhouse forcing [the 1880-1940 [CO2] rise from ~290 – ~309 ppm was quite significant (equivalent to nearly 0.3 oC at equilibrium with a mid-range climate sensitivity)]. With a small solar contribution, the 1910-1845 warming can be understood rather well.

    Indeed, recovery from (negative) volcanic forcing is consistent with the marked Arctic warming you mention, since the high polar latitudes are very susceptible to the cooling effects of volcanic aerosols. Recovery from this forcing probably made a large contribution to Greenland temperature rise during your period as described by Box et al (2009).

    Comment by chris — 21 Jun 2011 @ 2:45 PM

  33. Are solar physicists always so keen to risk having egg all over their faces? Since there is insufficient data dating from the last Grand Minimum, how can recent anomalies be seen as a sign of anything? My reading of Biesecker and Nandi’s remarks seems to support this view.
    Is it the politics of solar physics or some other forcing that is driving this phenomenon?

    Comment by One Anonymous Bloke — 21 Jun 2011 @ 4:03 PM

  34. Gavin

    Re: #30 (my post)

    Response: Odd that the only paper to make a connection between Arctic temperatures and solar activity (Soon, 2005) used the …… Hoyt and Schatten reconstruction. Isn’t that a little contradictory to your first point? – gavin]

    I’m not terribly concerned what ‘other’ papers say. How do you explain the Arctic temperature rise in the early 20th century.

    [Response: There are at least two problems in providing a robust explanation. Firstly the forcings over this period are not as well known as in more recent times (solar, aerosols, especially black carbon). Secondly, the arctic has a lot of internal variability - this implies that there is going to be a number of equally probable 'explanations' that can't really be assessed absent some additional data. So it isn't going to be either a place or a period that are going to lead to strong conclusions. - gavin]

    Comment by John Finn — 21 Jun 2011 @ 6:01 PM

  35. They did include a solar minimum, not only that they included one that lasts throughout most of the 21st century – far longer than the period of time that the Maunder minimum persisted. – Timothy

    My question was poorly worded, but this is at which I was getting. In Hansen’s recent draft paper, he discusses recent temperature versus a solar minimum. In my understanding, which is less than rudimentary at best, the last half of the recent decade saw the global mean rebound into the teeth of a fairly prolonged spell of few spots (and a deluge of global cooling predictions.) Am I wrong about that?

    Comment by JCH — 21 Jun 2011 @ 6:16 PM

  36. chris says:
    21 Jun 2011 at 2:45 PM

    John Finn – If you tried a little investigation and thought you could address your own false accusation about early 20th century warming (and might not appear such a boor).

    I suspect you’re looking at the Hadcrut temperature data since that’s the one that gives “a ~0.5 deg rise in global temperatures”…”between ~1910 and ~1945″. It’s pertinent to your point that the global temperature drifted downwards a tad between 1880ish and 1910ish, a result most likely of the large volcanic activity in that period.

    Possibly, do go on…

    So the marked early 20th century warming was likely a mixture of recovery from volcanic forcing…

    Ok – there was the Krakatoa eruption in 1883 and a major eruption in ~1902. The warming started 10 to 15 years after that. But isn’t that a bit like the last 20-30 years, i.e. El Chichon erupted in 1982 followed by Pinatubo in 1991. Perhaps the warmth of the last decade was, at least partly, due to a recovery from the Pinatubo eruption.

    and accumulated (but masked) greenhouse forcing [the 1880-1940 [CO2] rise from ~290 – ~309 ppm was quite significant (equivalent to nearly 0.3 oC at equilibrium with a mid-range climate sensitivity)].

    So the CO2 rise from 290ppm to 309ppm was responsible for 0.3 deg temp rise. Using the simple Myhre et al formula the forcing due to this rise would be 5.35xln(309/290) = 0.33 w/m2, so your 0.3 deg riseimplies a sensitivity of ~0.9 deg/w/m2. Seems a bit high but let’s run with it. How does this explain the post 1945 rise. Again using Myhre et al the CO2 forcing since 1945 can be calculated by 5.35xln(390/309) = 1.24 w/m2. Using your sensitivity figure the temperature increase should be ~1.1 deg. Just checking GISS I note that the actual temperature increase since 1945 is ~0.6 deg.

    Something doesn’t quite add up – but I knew that already (I have done a “little investigation”)

    With a small solar contribution, the 1910-1845 warming can be understood rather well.

    Can it?

    Comment by John Finn — 21 Jun 2011 @ 6:38 PM

  37. John @ 36,
    take a look at my post at “comments on 2000 Years of Sea Level, #12, for some long term temperature graphs & comparisons to CO2 levels.

    Comment by J. Bob — 21 Jun 2011 @ 9:00 PM

  38. O.K, good John Finn – you can address these questions yourself without boorish false accusations!

    Of course my account was a broad description of likely contributions to early 20th century warming. Note, BTW, that I stated that the greenhouse gas contribution was an equilibrium value. It’s unlikely that the greenhouse gas contribution in the period 1880-1940 was nearly 0.3 oC since that would be the full equilibrium response (under a 3 oC climate sensitivity). So your numerology re late 20th century and contemporary warming is misplaced.

    But I’m sure you know that (even if you pretend not to!). Attribution of early 20th century warming requires a more quantitative consideration of all the contributions (e.g. atmospheric aerosols, black carbon etc. as well as anthropogenic greenhouse contributions, recovery from volcanic aerosols and solar etc.). Try here for example.

    We may not know everything, but things do “add up”…

    Comment by chris — 22 Jun 2011 @ 6:28 AM

  39. #4 R. Gates

    On the contrary R. Gates, I think by 2020, much of the Arctic ice will be obviously depleted in the summer melt season, and I would say it is most likely that the majority of people will have a better idea of how greenhouse gases work. And of course by then we will likely have seen trends in the crop productivity tied to warm days and periodic events affecting crop yields. Not so hard to see the CO2 from human emissions negative impacts from that perspective.

    #26 stuart

    I think there is a possible SG/VG connection here. Like a see-saw: the Solar God relaxes while the Volcano God Expresses and vice versa. What institute did you say was doing some research in this area?

    #30, #34 John Finn

    Being not terribly concerned what other papers say means that you are not terribly concerned with utilizing the scientific method as your basis for developing your understanding. That would indicate that you prefer to believe only those papers that you like or think support your own ideas of reality. That’s not the way science works.

    #36 … John Finn

    The early part of the century is still buried in the noise a bit; sort of like weather noise is buried in climate signal. That does not mean that CO2 did not have an impact but more likely that, though having an impact, is still buried in throws of natural variation. I’m not up on recent work in the area but I’m sure they are working on coaxing out the climate signal as natural variability is becoming better understood.

    Context is key? What are you trying to imply? That uncertainty in the early part of the century reduces certainty in the latter part of the century? Or something else?

    Comment by John P. Reisman (OSS Foundation) — 26 Jun 2011 @ 2:54 AM

  40. May I be practical? What will it mean for someone installing solar panels?

    [Response: Nothing. The differences are extremely small compared to average insolation and will not be visible in solar array performance. - gavin]

    Comment by carol isaac — 26 Jun 2011 @ 3:54 PM

  41. John P. Reisman (OSS Foundation):
    Most likely outcome is that the Arctic ice volumes could be decreasing further in forthcoming decade, while both N. Europe and N.E. US winters get much colder.
    This is not a contradiction but the consequence of negative phase of NAO.
    http://www.vukcevic.talktalk.net/NAO-.htm

    Comment by vukcevic — 27 Jun 2011 @ 7:20 AM

  42. The study you did assumes only direct solar forcing, but I can’t help wondering if Judith Lean’s regression results (albeit linear) don’t suggest indirect forcing about equal to the direct. If so, the effect of a new extended minimum would have a larger effect. Those who argue that regressions must be non-linear may be ignoring that some of the other forcings such as ENSO might be influenced by solar activity.

    Comment by charles "chick" keller — 29 Jun 2011 @ 2:31 PM

  43. From what I have read on this, the solar physicists who announced these findings added quite a few caveats about their studies (e.g., “If true,…”"). Clearly this is not a definitive set of results for making profound, unassailable predictions of the future. However many of their analyses appear to be based on data gleaned during the “satellite era” and thus reflect a very limited time series, especially when we compare it to the length of time that humans have walked the Earth. My understanding is that these scientists, the solar physicists, are trying to work with what they have, and three INDEPENDENT analyses of different data propose that there is a major change underway, and that we MIGHT be about to witness a new Solar Minimum. I would expect that many if not most solar physicists today would acknowledge that there are many uncertainties about what makes the Sun tick, and about the effect all those things would/might have, by both known and unknown mechanisms, on and for Earth, including our climate. The lack of comparable (i.e., modern technological) data about the Sun during and just prior to the LIA, the MWP and other important historical periods is a problem, so our understanding is, and always will be, evolutionary. I don’t intend to hang my hat on the results exclusively, but to also be mindful that other real-world observations may either support the conclusions or provide additional information that forces the theories and hypotheses to evolve in a different direction. Not being a solar physicist, I can only trust that the analyses have been done with care, following the scientific method, and accept that they could be either right or wrong with their predictions.

    That said, all I have read thus far about the climate modeling run of last year by Rahmstorf, et al., seems to suggest a heavy focus on TSI as the sole or primary mechanism for solar influence on Earth’s climate. I have read numerous reports in the past two years that relate how observations and analyses have identified as yet unclear mechanisms linking the Sun and Earth’s climate subsystems (such as the oceans). If those studies (many funded via the National Science Foundation. My question is how do we KNOW that TSI is the only component that is critical in the Earth’s climate?

    We still do not understand fully what causes clouds to form. “Because clouds are so dynamic and can contain ice, water, or a mixture of the two, they continue to be one of the hardest components of the climate system for scientists to model accurately.” (See: http://www.eurekalert.org/pub_releases/2010-12/dnnl-sb5120910.php)

    We also know that there have been periods in the past during which CO2 levels and temperatures have been comparable to what they are today, yet do not understand the mechanisms behind those warm periods with coincident high CO2. (See: http://www.eurekalert.org/pub_releases/2010-12/uoc–bsw121010.php — this particular study focuses on the Pliocene Warm Period, 3.5 to 4.5 million years ago)

    Comment by Gene — 2 Jul 2011 @ 12:29 PM

  44. That’s a huge dip about 2020 … did you factor in a supervolcno eruption to get that amount of cooling? It looks to me like a VEI 8 event would be needed to produce that dip?

    “Those sharp dips are from volcanic eruptions that were put in to make the scenarios more realistic (though of course no-one knows when the next big climate-affecting eruption will be). We should have made that clearer though. – gavin]”

    Comment by William — 2 Jul 2011 @ 11:48 PM

  45. Made a short search on spectroscopical studies on leafs (tangentially related to the TSI question, as a notable portion of the planet is covered with plants…). The relevant question for climate change students here would be “what sort of alterations in the irradiation spectrum of the sun would produce effects on carbon fixation?”

    water is a major absorber of IR in leafs:
    http://speclab.cr.usgs.gov/national.parks/Yellowstone/ynppaper.html

    increase in UV-radiation decreases the leaf area in couple of Antarctic species (which should be quite tolerant to UV):
    http://www.plantphysiol.org/content/125/2/738.full

    normal chlorophyll complex spectrum (radiation used for photosynthesis a.k.a. carbon fixation in living plants(cyanobacteria have a slight different spectrum)) :
    http://www.life.illinois.edu/govindjee/paper/fig5.gif

    and the obligatory effect of heat-stress in the photosynthetic machinery:
    a broadleaf tolerates heat better and recovers faster than a conifer but both start showing a decrease in photosynthesis if T>40C:
    http://connection.ebscohost.com/c/articles/8052611/temperature-induced-changes-photosystem-ii-activity-quercus-ilex-pinus-halepensis

    As most of the earth is covered by ocean the next questions could be of the UV/VIS -spectrum of water:”How deep under water floating algae can photosynthesize and what is the effect of ozone hole to the primary production on the southern ocean?”

    Comment by jyyh — 3 Jul 2011 @ 2:13 AM

  46. There are an interesting suite of anomalies that appear to correlate with solar minimums.

    There is addition to paleoclimatic changes that correlate with deep solar minimums there is a curious increase in worldwide volcanic activity during deep solar minimums. (The anomaly is the increase in volcanic activity is in regions that geographically and geologically separated.)

    Curiously sea level also correlates with solar minimums (sea level falls during solar minimums) with the change in sea level being more than twice what would be expected based on thermal expansion due to temperature change.
    Solar cycle 24 appears based on the change in solar parameters to be an abrupt interruption in the solar magnetic cycle as opposed to a slow down. There is also an interesting suite of anomalies associated with observations related to the solar magnetic field and stellar magnetic fields.

    Comment by Saul — 4 Jul 2011 @ 9:12 AM

  47. My father is somewhat of a climate ‘sceptic’ and insists that the prediction of 0.3C cooling is based only on solar irradiance and does not take into account increased cloud cover caused by low sun activity (he beleives that we are going to be facing extreme global cooling over the next few decades). Could anyone tell me if he is in any way correct. Thanks.

    Comment by Jonty — 6 Jul 2011 @ 3:51 PM

  48. An interesting look at our variable sun. The conclusions of -.3C are not consistent with historical evidence, ice core analysis, crude 16th century thermometers, or glacier movement that suggest NH cooling of -2C during Maunder. Since our current warm period is primarily a NH event a Maunder type -2C NH cooling would be dramatic.

    While there is pretty strong evidence to suggest a 1.5C warming by doubling atmospheric CO2, suggesting a +4C by 2100 is speculative at best requiring large assumptions of positive feedbacks that have not been observed to date. I suspect given what we know about radiative physics and what we don’t know about the sun during a prolonged grand minimum it is equally likely that it will be no warmer in 2100 than it is today.

    While considering the possible grand minimum this century we must also consider the effect of the Grand maxima we experienced during the last century and it’s possible contribution to observed warming.

    [Response: There is no synthesis of evidence that supports your claims of such a large change at the Maunder Min. - you are implying a change that is 1/3 of the way to a full blown glacial maximum. Very, very unlikely (about as unlikely as 2100 not being any warmer than today - though that is mainly wishful thinking). - gavin]

    Comment by ivp0 — 7 Jul 2011 @ 11:24 AM

  49. Gavin Says: “There is no synthesis of evidence that supports your claims of such a large change at the Maunder Min. – you are implying a change that is 1/3 of the way to a full blown glacial maximum. Very, very unlikely (about as unlikely as 2100 not being any warmer than today – though that is mainly wishful thinking). – gavin]

    Hmmmm,

    I suspect Dr. Richard Alley would strongly disagree:
    “In the North Atlantic, sediments accumulated since the end of the last ice age nearly 12,000 years ago show regular increases in the amount of coarse sediment grains deposited from icebergs melting in the now open ocean, indicating a series of 2-4ºF (1-2ºC) cooling events recurring every 1,500 years or so. The most recent of these cooling events was the Little Ice Age between 1500-1850 AD when European rivers and ports were choked with ice, and glaciers overran alpine villages.” -Alley

    [Response: I doubt it actually. Alley is talking mainly about D/O events and, like some others (Broecker for instance) tried to link it to the LIA, but neither the pattern of change, the abruptness, the ocean circulation change nor the magnitude actually match. You don't give a date for this quote, but I doubt it is recent. - gavin]

    Comment by ivp0 — 7 Jul 2011 @ 12:37 PM

  50. “You don’t give a date for this quote, but I doubt it is recent. – gavin”

    Looks like 1998 to me:
    http://www.usgcrp.gov/usgcrp/seminars/980217DD.html

    -M

    Comment by M — 7 Jul 2011 @ 3:42 PM

  51. The Alley quote come from this:
    http://www.usgcrp.gov/usgcrp/seminars/980217DD.html
    “Abrupt Climate Changes Revisited: How Serious and How Likely?”
    USGCRP Seminar, 23 February 1998

    Note the date.

    Comment by Robert Murphy — 7 Jul 2011 @ 4:02 PM

  52. Jonty:

    There is no evidence for this. The temperature changes associated with solar minima, or for that matter prolonged solar inactivity are very small compared to what you get with a doubling or tripling of CO2 in the atmosphere. There’s some interesting dynamical feedbacks and regional responses (see section 4 of the paper I linked to in post #22), but we have evidence for what happened during the Maunder Minimum, and the cooling trend was relatively modest, and probably depended on other things as well (like volcanic activity).

    As I said in my post #1, the “business-as-usual” expectations for the global temperature by 2100 (or beyond) if we continue to emit carbon are something like an order of magnitude greater than anything the sun has done over the last 10,000 years, so even if you believe in these amplification factors or if clouds enhance the sun-induced cooling by a factor of two or three, you are still left with a big warming signal. Though, as I also said, there’s probably some interesting work to be done with short-term prediction when the effects of CO2 are comparable to both the decline in sunlight and natural variability.

    Your father also wants the argument to go one way: if clouds operated as a positive feedback to decreased solar (further causing cooling) then they could just as well act as a positive feedback to the elevated greenhouse gases (further enhancing the warming). Clouds are a very uncertain subject in general though, but most estimates having them as a neutral to positive feedback. It’s not settled, but a huge cooling trend in the near future seems well beyond the constraints we have.

    Comment by Chris Colose — 7 Jul 2011 @ 5:12 PM

  53. @50
    Yes that is the source. Alley was doing the bulk of his paleo work in the 90s. He is now monitoring change in glaciers and ice sheets but I believe he still considers his earlier LIA data quite valid. Got a link that supports your statement that he no longer believes the NH LIA was -(1-2C)? Perhaps I will ask him.

    @52 Chris says “The temperature changes associated with solar minima, or for that matter prolonged solar inactivity are very small compared to what you get with a doubling or tripling of CO2 in the atmosphere.”
    There is simply no scientific support for this statement Chris. When solar activity falls far below the sunspot threshold, far below any time that we have measured TSI with satellites we are in uncharted territory. We do not know what effect this will have on climate because we have never been there. Gavin suggests Maunder was mild at only -.3C but Richard Alley, historical records, glacier movement, migration patterns, clothing trends, crop records, ice cores suggest a much deeper NH dip in temps (1-2C). It important to get this right so we have a better idea of what to expect over the next 70 years or more. If Gavin is right, AGW will continue with a modest reduction. If Alley (and historical record) is right, a deep solar minima may neutralize AGW for the 21st century only to emerge when solar activity increases again. To consider this possibility is just good clean science at work.

    Comment by ivp0 — 7 Jul 2011 @ 9:41 PM

  54. @50 Yes that is the source. Alley was doing the bulk of his paleo work in the 90s. Now he is mostly focused on changes and movement of the cryosphere but I believe he still feels his LIA data is valid. Got a link to suggest he changed his mind?

    @52 Chris says: “The temperature changes associated with solar minima, or for that matter prolonged solar inactivity are very small compared to what you get with a doubling or tripling of CO2 in the atmosphere.”

    Sorry Chris but there is no evidence to support your statement either. If solar activity drops off far below the threshold to produce sunspots for a prolonged period we are in uncharted territory with no instrumental precedent. TSI estimates are completely unknown and we don’t really know what the climate response will be. If Gavin is right AGW will continue with only mild attenuation for a while. If Richard Alley was correct in his assessment of NH temps during the LIA, the quiet sun may play a stronger climate forcing role than GHGs for most of this century. Interesting times!

    [Response: From Richard Alley's Earth: The Operator's Manual (2011), Chapter 9 (The Moving Finger Writes), p. 115-116 (section on "Solar Stuff"): The small variations in the sun's output during sunspot cycles have caused small variations in Earth's temperature. The cold of the Little Ice Age of a few centuries ago seems to have involved both a little extra sun-blocking effect from explosive volcanic eruptions, and a small reduction in the sun's output....There is a small but interesting literature looking for amplifiers that might allow tiny changes in the sun to cause larger changes in climate...However, the few tenths of a degree from such influences are very small compared to the possible warming if we burn most of the fossil fuels". Any further discussion of Richard's views will be considered O-T. -mike]

    Comment by ivp0 — 7 Jul 2011 @ 10:06 PM

  55. This is what’s been quoted in the last 3 weeks, suggesting a possible end to sunspot cycles for a while:

    http://www.boulder.swri.edu/~deforest/SPD-sunspot-release/SPD_solar_cycle_release.txt

    Same press release from SRO:
    http://www.nso.edu/press/SolarActivityDrop.html

    One news story based on that:
    http://earthsky.org/space/major-drop-in-solar-activity-ahead-scientists-say

    Comment by Hank Roberts — 8 Jul 2011 @ 2:30 AM

  56. Might as well quote the bit that’s being left out of the blog science copypastes:

    ______________________
    In response to news inquiries and stories, Dr. Frank Hill issued a follow-up statement:

    “We are NOT predicting a mini-ice age. We are predicting the behavior of the solar cycle. In my opinion, it is a huge leap from that to an abrupt global cooling, since the connections between solar activity and climate are still very poorly understood. My understanding is that current calculations suggest only a 0.3 degree C decrease from a Maunder-like minimum, too small for an ice age. It is unfortunate that the global warming/cooling studies have become so politically polarizing.”
    —————-
    http://www.nso.edu/press/SolarActivityDrop.html

    Comment by Hank Roberts — 8 Jul 2011 @ 2:32 AM

  57. @53
    Thank you for your response Mike. I am aware of Alley’s views on the possible causes of the LIA. It is the classic textbook answer that is most common. I am certain that volcanic activity played a role in brief cold periods throughout the LIA just as Pinatubo did in the early 90s. Your response does fail to answer the question asked though:

    Does Richard Alley still believe that the LIA was characterized by NH temps falling 1-2C over an extended period as he did in 1998 while doing his paleo studies, or has he invalidated his own data and accepted the more consensus view (Gavin et al) that it was a far milder event (approx -.3) as stated in the op?

    As I am sure you are aware the NH climate implications of a difference between (-.3) vs (-2C) are huge. Both scientists are bright guys with strong credentials. It would be useful to get clarity on what really happened during Maunder as we face a possible sequel in the near future.

    Comment by ivp0 — 8 Jul 2011 @ 10:03 AM

  58. To Jonty, his “extreme global cooling” father, ivp0, and anyone else who might seriously believe that the next few decades will bring strong cooling:

    Off and on for years, I have been trying to make a large, public bet about the next few decades with someone who disagrees strenuously with mainstream climate science. Alas for my retirement fund, whenever I get a hint of a worthy opponent, they melt away in a flurry of anonymity, coy disclaimers, and general commitment-phobia.

    Since most of us on both “sides” agree that we are effectively betting our grandchildren’s futures anyway, it seems a small thing to ask.

    If you are serious, let’s find a suitable forum to work out the details.

    Please put up or shut up.

    Comment by Ric Merritt — 8 Jul 2011 @ 11:53 AM

  59. @57
    No need to get nasty there Ric. I am just a curious guy asking questions from the climate experts here. I have made no such cooling predictions (feel free to re-read my posts) and really just want to know if I need to buy sunshades or long johns for the next 50 years. I do hate to ignore history though. So sorry if my questions have somehow ruffled your feathers.

    Comment by ivp0 — 8 Jul 2011 @ 12:14 PM

  60. > ivp0 says:
    > 8 Jul 2011 at 10:03 AM
    > your response does fail to answer the question asked though:
    > Does Richard Alley still believe …

    You’re copypasting a faux-clever trick question widely circulated a year ago. You’re rebunking.

    Look it up, like this: http://www.google.com/search?q=%22Richard+Alley%22+%22little+ice+age%22+temperature+change

    The first hit debunks the question you’re pretending to ask:

    “Richard Alley’s name has been thrown around a bit by bloggers asserting that ice-core records from Greenland show that carbon dioxide has scant, if any, influence on climate…. I sent a query to Dr. Alley about such interpretations of his work and the ice-core record and he sent a reply, the heart of which is pasted below…..”

    http://dotearth.blogs.nytimes.com/2010/02/08/richard-alley-on-old-ice-climate-and-co2/

    Read. Think for yourself.

    Comment by Hank Roberts — 8 Jul 2011 @ 1:21 PM

  61. ivp0:

    Does Richard Alley still believe that the LIA was characterized by NH temps falling 1-2C over an extended period as he did in 1998 while doing his paleo studies, or has he invalidated his own data and accepted the more consensus view (Gavin et al) that it was a far milder event (approx -.3) as stated in the op?

    Look, the NH is not the world, and as has been stated repeatedly the LIA wasn’t caused only by a drop in TSI anyway. The 0.3C figure is for average global temps, not the continental masses of the NH.

    It’s not enough to offset the global 4C warming we expect to see by 2100, and in the NH would serve to diminish warming but not start another LIA. That’s the point. Global warming of (say) 3.7C vs. 4C means NH continental warming of 10C+/- a bit in either case.

    Comment by dhogaza — 8 Jul 2011 @ 2:45 PM

  62. @59
    Sorry Hank,
    I guess I am not that clever as I did not find the answer to my question in your links. I do admit to being somewhat of a fan of Dr. Alley. His observations, teaching style, and curious mind are quite refreshing. I also believe that the earth is warming and manmade CO2 certainly plays a key role in this. As always, the devil is in the details and that often means asking the hard questions. I apologize if this process somehow offends you.

    Comment by ivp0 — 8 Jul 2011 @ 3:39 PM

  63. @ivp0: I am just a curious guy asking questions from the climate experts here.

    *eyes rolling*

    Right. Just a noble seeker after truth. Mm-hmm.

    Comment by Adam R. — 8 Jul 2011 @ 4:01 PM

  64. I didn’t say anything “nasty” (your word, ivp0).

    I notice any candidates to take a serious bet have melted away, as I predicted. Seems to be a good correlation with arctic sea ice there, maybe a subject for research. Jonty’s father, oh where are you?

    An awful lot of disagreement with mainstream climate science, so many mentions of decades of cooling, none of them serious.

    Comment by Ric Merritt — 11 Jul 2011 @ 11:44 AM

  65. Chris:

    Thanks for the info/ammunition – Will put it to pa (will probably end up agreeing to disagree as usual)

    Comment by Jonty — 11 Jul 2011 @ 12:14 PM

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