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Solar spectral stumper

Filed under: — gavin @ 7 October 2010

It’s again time for one of those puzzling results that if they turn out to be true, would have some very important implications and upset a lot of relatively established science. The big issue of course is the “if”. The case in question relates to some results published this week in Nature by Joanna Haigh and colleagues. They took some ‘hot off the presses’ satellite data from the SORCE mission (which has been in operation since 2003) and ran it through a relatively complex chemistry/radiation model. These data are measurements of how the solar output varies as a function of wavelength from an instrument called “SIM” (the Spectral Irradiance Monitor).

It has been known for some time that over a solar cycle, different wavelengths vary with different amplitudes. For instance, Lean (2000) showed that the UV component varied by about 10 times as much as the total solar irradiance (TSI) did over a cycle. This information (and subsequent analyses) have lent a lot of support to the idea that solar variability changes have an important amplification via changes in stratospheric ozone (Shindell et al (2001), for instance). So it is not a novel finding that the SIM results in the UV don’t look exactly like the TSI. What is a surprise is that for the visible wavelengths, SIM seems to suggest that the irradiance changes are opposite in sign to the changes in the TSI. To be clear, while the TSI has decreased since 2003 (as part of the descent into the current solar minimum), SIM seems to indicate that the UV decreases are much larger than expected, while irradiance in visible bands has actually increased! This is counter to any current understanding of what controls irradiance on solar cycle timescales.

What are the implications of such a phenomena? Well, since the UV portion of the solar input is mostly absorbed in stratosphere, it is the visible and near-IR portions of the irradiance change that directly influence the lower atmosphere. Bigger changes in the UV also imply bigger changes in stratospheric ozone and temperature, and this influences the tropospheric radiative forcing too. Indeed, according to Haigh’s calculations, the combination of the two effects means that the net radiative forcing at the tropopause is opposite in sign to the TSI change. So during a solar minimum you would expect a warmer surface!

Much of the longer term variance in solar output has been hypothesised to follow what happens over the solar cycle and so if verified, this result would imply that all current attributions to solar variability of temperature changes in the lower atmosphere and surface ocean would be of the wrong sign. Mechanisms elucidated in multiple models from multiple groups would no longer have any validity. It would be shocking stuff indeed.

Conceivably, there might be another missing element (such as a cosmic-ray/cloud connection) that would counteract this physics and restore the expected sign of the change, but no-one has succeeded in finding any mechanism that would quantitatively give anything close the size of effect that would now be required (see our previous posts on the subject).

So is this result likely to be true? In my opinion, no. The reason why has nothing to do with problems related to the consequences, but rather from considerations of what the SIM data are actually showing. This figure gives a flavour of the issues:

(courtesy Judith Lean). Estimates of irradiance in three bands are given in each panel, along with the raw measurements from various satellite instruments over the last 30 years. The SIM data are the purple dots in the third panel. While it does seem clear that the overall trend from 2003 to 2009 is an increase, closer inspection suggests that this anti-phase behaviour only lasts for the first few years, and that subsequently the trends are much closer to expectation. It is conceivable, for instance, that there was some undetected or unexpected instrument drift in the first few years. The proof of the pudding will come in the next couple of years. If the SIM data show a decrease while the TSI increases towards the solar maximum, then the Haigh et al results will be more plausible. If instead, the SIM data increase, that would imply there is an unidentified problem with the instrument.

In the meantime, this is one of those pesky uncertainties we scientists love so much…


254 Responses to “Solar spectral stumper”

  1. 1
    san quintin says:

    If true, rather upsets the attribution of parts of the LIA like the Maunder Minimum.

  2. 2
    toxymoron says:

    Hi,

    The figure seems to be missing from your post and the RSS feed.

    Regards,

  3. 3
    Alexandre says:

    Layman’s question:

    Warmer surface during a solar minimum? What about Maunder minimum and Little Ice Age?

    And isn’t a figure missing just above Lean’s paragraph?

  4. 4
    John Ransley says:

    Thanks. Judith Lean figure is currently missing

    [Response: fixed. thanks. – gavin]

  5. 5
    prianikoff says:

    According to Joanna Haigh quoted in the “Independent”:
    “…we may have overestimated the Sun’s role in warming the planet.”

    What is more, the slightly increased solar activity over the past century:

    “may have kept global warming in check by lowering temperatures slightly and counteracting the influence of greenhouse gases.”

    See:-
    http://www.independent.co.uk/environment/climate-change/ozone-study-dims-suns-global-warming-role-2099712.html

    http://www.guardian.co.uk/science/2010/oct/06/sun-role-warming-planet

    The other question is how does this show up in the 11 year solar cycle?
    I’m not aware that there is any correlation with troposperic or stratospheric temperature change.

    3 years of data doesn’t seem very conclusive in establishing the hypothesis, but I’ve noticed that the newspapers that are most associated with denying anthropogenic Global warming are already exploiting this study contrary to the stated views of its authors.

    Surprise, surprise!

  6. 6
    Ld Elon says:

    Man could not even dream of being a planet, which is inevitable.
    Now hear the calling of the spheres.

  7. 7
    prianikoff says:

    A good interview with Joanna Haigh of Imperial College, originally published in 2001 and reproduced on the Open University’s web site:

    http://www.open2.net/sciencetechnologynature/worldaroundus/two_warming4.html

  8. 8
    prianikoff says:

    #5 To follow up

    This is the most recent study on the 11 year solar cycle that I’ve been able to find:-
    Title: “Surface warming by the solar cycle as revealed by the composite mean difference projection”
    Authors: Charles D. Camp and Ka Kit Tung: Department of Applied Mathematics, University of Washington, Seattle, Washington, U.S.A.
    Source: Geophysical Research Letters (GRL) paper 10.1029/2007GL030207, 2007

    It reports a global temperatures increase 0.18°C due to an increase in Total Solar Irradiance (TSI).
    (This 11 year cycle is superimposed over the long term global warming trend.)

    http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.140.6149

  9. 9
    Susan Anderson says:

    Thanks for this. With my limited ability to digest scientific information, this provides just the level of skepticism about this issue needed. It is so easy to read vast reams of irrelevant opinion into factual material like this.

    I also looked at the BBC Open University site, and while the page from Dr. Haigh is good, the overall tone of the grouping gives far too much weight to the supposedly skeptical view. Unfortunately, real skepticism is all too rare – the kind that looks at all the available information and does not overweight information it wishes to believe. The proliferation of think tanks and expertise supported by wealthy interests lends plausibility to the assumption that there is a large cadre of credible scientists in relevant fields with views that contradict the real state of scientific understanding.

    Confusion, unfortunately, is all too easily conflated with uncertainty.

  10. 10

    #1, #3:

    For people upset about the implications for the impact during the Maunder Minimum, I’d suggest that this observation, if confirmed, can only be said to apply to the current, active level of 11 year cycles. It would I think be erroneous to jump to the conclusion that during an extended quiet period, visible radiation must also remain continuously increased throughout that period.

    In particular, the visible increase may be the result of some “rebound” mechanism resulting from the previous TSI high. If there were no previous TSI high, there might be no subsequent increase in the visible radiation. This would be particularly true if the duration of the visible radiation increase is in fact short (“only lasts for the first few years”).

    Until the reason/mechanism is hypothesized/understood, or until we encounter another Maunder Minimum period of solar behavior during which we can directly observe the behavior, it’s impossible to say what’s what.

  11. 11
    Leonard Weinstein says:

    Since absolutely positive statements have previously been made that the solar variations can’t possibly cause significant temperature changes, and since we seem to be learning new things about solar activity all the time, statements like “Conceivably, there might be another missing element (such as a cosmic-ray/cloud connection) that would counteract this physics and restore the expected sign of the change, but no-one has succeeded in finding any mechanism that would quantitatively give anything close the size of effect that would now be required (see our previous posts on the subject).

    So is this result likely to be true? In my opinion, no.” shows the ignorance of the author. WE DON’T KNOW is the fact here. No one has found a mechanism, but you just stated a new and previously unknown mechanism. There is no reason to think we have found all there is to know yet. Be a bit more open minded.

    [Response: If you are not interested in my opinion, then don’t read the blog. ;) But if you are interested in what people that have looked at this issue in detail, then you might want to pay attention. When you get results that purport to overturn decades of understanding, the most likely outcome is that there is an error some down the line. In this case, my guess is that there is still an unidentified issue with the early years of the satellite. If new data comes in that confirms this result (i.e. SMI in the visible goes down as we go to solar max), then I will update my expectation, but in the meantime, great caution is warranted. Being open-minded is all well and good, but the whole point about actual expertise is that it allows you to weight new information in a more efficient manner. My advice to you is to wait-and-see, rather than jumping to any conclusions. – gavin]

  12. 12
    Hank Roberts says:

    Is any effect expected from variation in dust between us and the Sun?
    It’s somewhat variable: http://dx.doi.org/10.1016/j.pss.2009.11.002

    Are there data for other stars? Do they show individual changes in stellar output? Any pattern suggesting local dust might be affecting what reaches us?
    (I expect this has an obvious answer to the astronomers, not likely to take up space in paper publications, it’s a ‘peanut gallery’ question.)

  13. 13
    Grinspoon says:

    So my take away was.. what if it means that the radition during a maximum reacts more with the greenhouse effect, than during a minimum. Changing the balance of the causes of warming. None greenhouse solar warming is more during minimum, but greenhouse warming is reduced. So during a maximum, direct solar warming is less, but there’s more greenhouse warming.

  14. 14
    gavin says:

    I’m finding it very amusing how the contrarians are reacting to this paper – the most incoherent example is illustrated by the UK’s Daily Express story. First off the whole story is predicated not on the actual results, but on what the ‘skeptics’ think of the results, and the quotes they use indicate without a shadow of a doubt that Monckton, an MEP (of unknown origin) and Montford do not have a clue.

    The MEP (Godfrey Bloom) goes into a knee-jerk ‘the sun did it response’ without noting that the results of this study would completely contradict earlier associations of the medieval warming to increased solar activity. He even claims to be using logic! Monckton plays it safe saying there is a ‘close association’ between temperatures and the sun, without actually noting that the association is reversed in this study from anything he has previously insisted on. And Montford uses the absolutely lowest level generic response in the contrarian playbook “[insert any new paper here] implies the science isn’t settled” – as if that meant anything. (Note that no scientists would publish any papers if all questions were settled!).

    One doesn’t expect much from the Express (or the contrarians), but this is embarrassing.

  15. 15
    MR SH says:

    Very interesting.

    But if TSI and UV behave indicate opposite sign, since both have warming gases, it means “total warming power of sun” is stable than expected by TSI’s variation. If increased UV caused the recent warming, what happend the strong positive correlation between TSI and atmospheric temperature record before 1975? Is there any reason that the UV is stronger only recently than in the past cycle?

  16. 16

    14 (gavin),

    What’s shocking to me about that article is that I don’t see how this discredits AGW theory in any way. Silliness aside (like the claim of no warming for 12 years as a given fact, or the argument that other planets in the solar system are warming), how does this relatively meager discovery explain warming to date? There’s no evidence that this is a phenomenon that only began when recent warming began, or that it’s in any way different from the sun’s usual behavior. It’s unexpected, and will impact all sorts of models and expectations, but it’s hardly either an explanation for current climate change, or in any way a lever to explain why AGW should not and would not happen.

    The denier’s (excuse me, “contrarian’s”) bottom lines? (A) This is firm proof that we don’t know everything (duh!) and (B) the sun must be involved, so any new evidence that has the word “sun” used in a sentence completely obviates anything else being said or considered.

    *shakes head, goes back to work*

  17. 17
    MapleLeaf says:

    IMHO, the BBC did a pretty good job on this one:

    http://www.bbc.co.uk/news/science-environment-11480916

  18. 18
    CM says:

    spellcheck:
    – ‘hot of’ => ‘hot off’
    – ‘attributions of solar variability to temperature changes in the lower atmosphere and surface ocean’ => the other way around (or a lot more models and theories will have to be overturned…)

    [Response: indeed… thanks! – gavin]

  19. 19
    Hank Roberts says:

    Answering (in an amateur way) my question above, astronomers would have noticed if the interstellar medium were varying to this degree; it’s not.
    http://arxiv.org/abs/astro-ph/0601359
    “Optical or UV data are now available for ∼100 stars sampling nearby ISM [interstellar medium] … Very high-resolution optical data … for ∼40 nearby stars, and high resolution UV data … for an additional ∼65 stars.”
    Not likely anyone knowledgeable in the field would have missed

  20. 20
    Andy says:

    This is great! I love these things – it’s why scientists get out bed in the morning and go to work. Recall the Keppler paper?

    http://www.realclimate.org/index.php/archives/2006/01/scientists-baffled/

    Also great stuff. This is how science works people. Congrats to Haigh et al. even if the results turn out to be wrong!

    [Response: That’s a very good point. There is no problem in scientists exploring the ‘what if’s’ of the data that comes in. Sometimes they are going to be ahead of the curve, sometimes it’s going to be wrong, but it is the quantification of the consequences of new information that allows everyone else to look for those signals and help support (or not) the original idea. This is people seeing where the data takes them with an open mind. – gavin]

  21. 21
    Aaron Lewis says:

    The key phrase in this post is “instrumental drift.” I love the solid state stuff they put in the sky because it does not drift – much! Then, they put everything through a fairly complex model. It is very interesting, but it is not data of known quality and it has limited utility in risk management.

    It is time for climate science to grow up and establish standards of data quality; and procedures for data validation as was done under CERCLA for Human Health Risk Assement from hazardous waste.

    Data of known quality did much to get the paid data slingers out of the (CERCLA) spotlight. We need to turn the spotlight of climate science away from the data, and toward policy and action.

    [Response: You greatly overestimate how easy it is to control instruments once they are launched into orbit. Space is a pretty hostile environment, and with the single exception of the Hubble Space Telescope, once an instrument is launched there is no way of getting hold of it again. Since we generally only have single examples of new data, cross-checking is hard. If you would like to suggest doubling the budget so we could get two instruments every time, that would be great, but for the time being, we are stuck with the data we have, not the data we’d like. – gavin]

  22. 22
    caerbannog says:


    Comment by MapleLeaf — 7 October 2010 @ 11:44 AM

    IMHO, the BBC did a pretty good job on this one:

    http://www.bbc.co.uk/news/science-environment-11480916

    In the interest of fairness and balance, let me present the loony-tunes side (www.theregister.co.uk/2010/10/07/solar_as_big_as_people/):

    Much of recent global warming actually caused by Sun

    * Alert
    * Print
    * Post comment
    * Retweet
    * Facebook

    The ball of fire in the sky, not the jubblesheet

    By Lewis Page • Get more from this author

    Posted in Environment, 7th October 2010 11:21 GMT

    Free whitepaper – The Register Guide to Enterprise Virtualization

    New data indicates that changes in the Sun’s output of energy were a major factor in the global temperature increases seen in recent years. The research will be unwelcome among hardcore green activists, as it downplays the influence of human-driven carbon emissions.

  23. 23
    Fred Moolten says:

    Some idle speculation: The photosphere of the sun is often assumed to radiate like a black body, which implies that a reduction in total emitted radiation would be accompanied by a reduction at all wavelengths, even though the ratio of visible to UV would increase. For the absolute level of visible radiation to increase would seem to imply either a “non-black body” increase at the source that heats while the photosphere as a whole is cooling, some change in the transmission to the TOA (e.g., via an unmasking effect in the interstellar medium or the higher reaches of the atmosphere), some mechanism that shifts the frequency of radiation from shorter to longer wavelengths (e.g., by absorption and re-emission), or some combination of the above. Is there evidence for any of these phenomena, or any other mechanism that would explain the observations?

    In any case, whatever mechanism is operating would be unlikely to maintain an increase in visible radiation if TSI fell by more than a small decrement, and would therefore probably not invalidate conclusions relating major changes in TSI to changes in solar forcing and temperature of the kind that have generally been considered likely – changes that are small compared with greenhouse gas forcing but nevertheless in the same direction as changes in TSI.

  24. 24
    Rod B says:

    Fred Moolten (23), it is very curious. If I had to bet I’d put my money on variable emissivity. Though it’s hard to picture an essentially homogeneous surface varying its emissivity per wavelength much. I’d want some odds.

  25. 25
    Brian Dodge says:

    My suspicion is that their “relatively complex chemistry/radiation model” overestimates the 200-295 nm UV, and uses that to (mis) correct the 450-550 nm VIS to create a dip artifact in the VIS where the UV is high and rapidly changing, around 2004-2005.

    [Response: It’s not the model, it is the input data. – gavin]

  26. 26
    MarkB says:

    Climate contrarians have 2 general goals:

    1. To argue the human-caused global warming is minimal and/or not a problem

    2. To spread confusion

    The study does nothing to support #1, and if anything, is evidence against it. It tentatively argues that solar effects on climate (past and present) are smaller than previous estimates.

    “Overall solar activity has been increasing over the past century, so the researchers believe it is possible that during this period, the Sun has been contributing a small cooling effect, rather than a small warming effect as had previously been thought.”

    “We cannot jump to any conclusions based on what we have found during this comparatively short period and we need to carry out further studies to explore the Sun’s activity, and the patterns that we have uncovered, on longer timescales. However, if further studies find the same pattern over a longer period of time, this could suggest that we may have overestimated the Sun’s role in warming the planet, rather than underestimating it.””

    http://www.sciencedaily.com/releases/2010/10/101006141558.htm

    But any study that involves a natural driver of climate is spun to support #1.

    Other contrarians will play the generic “this just proves climate scientists don’t know anything” card.

  27. 27
    Steve Fitzpatrick says:

    Puzzling results indeed. The integrated spectra generate a TSI versus time plot which is pretty close to other TSI versus time plots, so if the spectral changes they are talking about are artifacts, then there would have to be offsetting errors at different wavelengths. The other interesting thing is that wavelengths which are reasonably close together show substantial divergence over time. This is looks difficult to explain with calibration problems. The dual identical spectrometer design, with one used only once per month the check radiation induced loss of transmission on the other, and other on-board calibration methods, look reasonably robust.

    All of which is not to say there could not be a problem with calibration, but if this turns out to be the case, it will probably have to be something that the design group completely missed. Unfortunately, the satellite is expected to die long before a replacement is launched, which will leave a gap of a few years in the spectral data.

  28. 28
    Edward Greisch says:

    Panel 3 appears to be double valued in 2005. It looks like something evaporated from the window of the SORCE instrument, allowing clear vision by 2010.

  29. 29
    cougar_w says:

    Cyclical changes in solar output — regardless of the sign on them — don’t appear to have had much impact on the steadily ramping global average temperature. It’s not the variability of the changes associated with AGW that are worrisome — it is the overall direction — and the overall direction seems driven by something outside of solar cycles. If it were otherwise none of this discussion would have ever taken place.

  30. 30
    oca sapiens says:

    “this anti-phase behaviour only lasts for the first few years”

    Help, please. If there is no instrumental drift, wouldn’t those first few years show the same behaviour in the maps of the ozone holes? And possibly during previous solar cycles as well? Joanna Haig’s paper mentions tropical ozone, so I must be missing something.

  31. 31
    CM says:

    Re Andy #20 (“Congrats to Haigh et al. even if the results turn out to be wrong!”): Yes, long as they don’t apply for grants in Virginia…

  32. 32
    Eli Rabett says:

    Wrong, this is much more important then you say. The UV is the photochemically active part of the spectrum, and it’s effects, including for example NO2 photolysis extend down to the surface.

    [Response: Sure, we’ve published papers on exactly that (i.e. Shindell et al, 2006), so what do you think I got wrong? – gavin]

  33. 33

    Re 23-25–

    Spend a few minutes looking at the SORCE data (Gavin conveniently linked it.)

    There’s a surprising (to this naive layperson at least, but also probably Fred and Rod, too, at least) amount of variability over shifts of just a few tens of nanometers of wavelength. Quite different irradiance levels, different curves over time. Check it out.

    I’ve no idea what it means. but…

  34. 34
    Jacob Mack says:

    Gavin great post. I wholeheartedly agree with your responses reminding people what science is and is not. Whether this paper is correct or not, it is the subsequent searching and looking at data and calculations that will better help us understand such complex issues. Global warming for example is well evidenced too so one claim to the contrary does not negate it either but as instruments and models are fine tuned and we have more data in hindsight better projections can be made. It can be tricky working out all the physics of these complex processes but I do feel as if this entry is more fair and balanced than many others will give it credit for.

    There is nothing wrong with a scientist giving an opinion. I have opinions based on how I view the data about future warming. I may be correct or I may be wrong. Uncertainty does not bar exploration. What I like is the opinion and the facts are separated very well by the author of the paper and by Gavin.

  35. 35
    deconvoluter says:

    Re #17

    Yes, but it is the BBC on the web*. As usual the radio was quite different.

    I have been told that Radio 4 at about 7AM was very confused, and that John Humphreys provided the news about it by reading out listeners emails. Later in the day, the item disappeared.
    —————-
    * There is pressure to cut or chop this arm of the BBC

  36. 36
    Jacob Mack says:

    Eli is a true expert. I look forward to hearing your response to Gavin sir.

  37. 37
    Corey Watts says:

    Gavin, love your work. Is it possible to start with a plain English summary? Cheers.

  38. 38
    Terry says:

    [Response: It’s not the model, it is the input data. – gavin. That’s a pretty big call. Many years ago, the stratospheric ozone models that included only gas phase were considered to be pretty solid too.

  39. 39
    Terry says:

    “[Response: It’s not the model, it is the input data. – gavin.” That’s a pretty big call. Many years ago the stratospheric ozone models were considered to be pretty sold too.

  40. 40
    Average Person says:

    Sounds like there’s a lot of love going around, however, I couldn’t help noticing the sarcasm. Would be slightly more interesting if it somehow jeopardized AGW alarm, although somehow I feel that wouldn’t get as much “love”.

    lol

  41. 41
    Geoff Wexler says:

    A vague report on a relevant bit of history.

    Coleman et al, 1973. Solid State Communications
    Volume 12, Issue 11, 1 June 1973, Pages 1125-1132

    which caused quite a stir and was, with difficulty, explained by some outstanding theorists. But the effect then appeared to go away:

    Anyway these points are less vague:
    1. Good theory includes past experimental knowledge (observations).
    2. New experiments (observations) should not always take precedence over old theory.

  42. 42
    nigel jones says:

    Assuming the papers correct, since solar activity has been increasing from about 1900 – 1970 then flat, shouldnt the climate have been cooling or static? Isnt this a compelling pointer at c02?

  43. 43
    Rod B says:

    MarkB (26), Skeptics are not Contrarians, which saves me a ton of words rebutting some of your post.

    [Response: Many of the so-called ‘climate skeptics’ are indeed contrarians, despite the fact they don’t have a skeptical bone in their body when it comes to anything that aligns with their preconceived notions. The true and honorable sense of the word has been corrupted though association with them. All scientists need to be (and are) skeptics (in the true sense). But let us not waste time on arguing about who is or is not skeptical in any of the thousands of ways the term is used. – gavin]

  44. 44
    Jacob Mack says:

    #41 The climate did cool from the 1940’s to the 1970’s. A big part of that were sulfates as Weart and other point out but who can say yet that solar activity did not also contribute? (Some also blame after effects of nuclear weapons) Perhaps there is more inertia than discussed prior to a cooling (or warming) effect. I am not stating it is the case but since some preliminary warming (a small comparitive %) in the paleoclimate record began prior to a C02 increase and then C02 acted as a forcing of said warming, why cannot it also be true of cooling? A lot of counter intuitive things could turn out to be true while C02 still remains a greenhouse gas. Nothing changes the fact GHG exert a greenhouse effect, but warming and cooling may be more complex than we ever imagined:)

  45. 45
    Jacob Mack says:

    Oops I made an error. I meant to say a feedback in the past but a forcing now. My apologies.

    [Response: Wrong still. It’s, time-independently, both. A critically important point.–Jim]

  46. 46
    Fred Moolten says:

    A 1997 paper by Gray and Livingston in The Astrophysical Journal is of interest, at Solar Temperature

    Although I’m not qualified to judge the methodology, I found Figure 9 of particular interest. It shows solar irradiance and solar temperature generally to vary in phase during the solar cycle, but not completely. In particular, in 1983 and again in 1992, temperature exhibited a slight temporary rise during a descending phase of the irradiance cycle. One implication is the existence of multiple sources of radiation that vary semi-independently, such that an irradiance decline could be accompanied by a transient increase in solar temperature, and therefore, radiation in visible wavelengths, even while an independent UV source was declining. I’d be interested in the interpretation of others who are conversant with astrophysics.

  47. 47
    Thomas says:

    That TSI and UV are not well coupled, or not coupled with the same sign shouldn’t be that surprising. There are two reasons the sun does not radiate as a black body. The most obvious is that the opacity of the solar atmosphere varies widely across the spectrum, so the average depth within the solar atmosphere that a given frequency comes from varies greatly. More importantly the upper parts of the solar atmosphere are superheated by turbulent hydromagnetic effects. The later effects vary strongly with the solar magnetic cycle. TSI, varying probably would imply energy storage within the outer layers of the sun itself, presumably by contracting and expanding its outer layers slightly. That the phases of the two effects are not the same probably says something about the interaction. But we shouldn’t be surprised that they TSI and UV might not vary in the same way. The crudest handwaving theory would be that periods of high magnetic activity slightly inhibit convective heat transfer with the sun (thats why sunspots are dark), and if so during periods of high solar activity some of the heat flux may be diverted to the energy storage (thermal and gravitational).

    In any case, some of these effects are likely transient behavior, and disentangling transient effects from secular effects may not be easy (if say solar activity is changing on century or longer timescales). The correlations of the different wavelengths may be different on short and long timescales.

    Also we have to remember, that the current solar minimum is anomalous, so we don’t know how the current data (if verified) relates to an average solar cycle.

  48. 48
    Olivia says:

    Interesting facts.

    It is meaning that surface will be get warmer, not cold such as ice age?

  49. 49
    MArk Green says:

    Um, sunspots? Speaking from a cosmological point of view, the sunspot cycle would seem to correspond closely to the data shown above. Visible light is reduced when sunspots are at maximum and, as sunspots are hotter than the rest of the sun’s surface, infra-red radiation increases. Obviously, the reverse is also true.

    The study doesn’t seem to be saying anything new at all, as far as I can see.

    [Response: Total irradiance increases with sunspots because they are accompanied by bright ‘faculae’ that more than compensate for the spots. So people expect increased warming as solar activity increases. – gavin]

  50. 50

    Does anyone have a time series of solar UV intensity? Where can I find one?

    [Response: The raw satellite data are available at the SORCE site linked above, while the solar irradiance models produce time series at all frequencies (see Wang Lean and Sheely for instance). – gavin]


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