Does climate sensitivity depend on the cause of the change?
Can a response to a forcing wait and then bounce up after a period of inertness?
Does the existence of an 11-year time-scale prove the existence of solar forcing?
Why does the amplitude of the secular response drop when a long-term trend is added?
These are perhaps some of the questions that we might hope to see discussed in the sequel to the sequel on solar forcing by Scafetta & West (S&W), a few of which have been discussed before here and here. (I still think those earlier studies were seriously flawed and showed a lack of scientific understanding, by the way).
This time S&W present a set of new arguments and a new set of results which are scattered all over the place. The impression from reading their paper is that the upper range (they call it ‘upper limit’) is probably more representative than the lower estimates for the solar contribution to the global mean temperature.
I think that many of their arguments, on which this impression is built, are shortsighted. For instance, they claim that certain climate reconstructions must be wrong because they give ‘unphysical’ answers. But there is another explanation too that they did not contemplate: their idealistic (one may also argue unphysical) model may also be wrong! Thus, they fail to exclude other explanations.
S&W attach the ACRIM Total Solar Irradiance (TSI) product (not the PMOD product, probably because that does not show any trend) to a TSI reconstruction (Lean 2000 TSI [see Lean, 2004], or Wang et al., 2005) in such a way that the average reconstructed TSI value over 1980-1991 corresponds with the ACRIM mean for the same period – never mind the discrepancies in trend and that such cavalier stitching of data series is one of the deadly sins in climatology (hint: the series is inhomogeneous).
One new aspect of this S&W study is the focus on ‘feedbacks’. They assume the TSI reconstruction is a proxy for the total solar influence and that CO2 is part of a solar ‘feedback’ (isotope ratios suggest the CO2 comes from deep underground reservoirs, but it’s not clear how the sun manages to dig up this carbon from deep below Earth’s surface).
S&W maintain that the climate response is greater for longer time scales (which is reasonable) as illustrated in their figure 4 (reproduced below), and assisted by the simple model illustrated in this figure, they argue that the present warming is a delayed response to past solar changes (presumably before the 1950s). But it is unclear why the temperature then flattened out and even dropped a little between 1940-1970 at the time when it really should have increased fastest. One could argue that something else also happened then, but for an unknown reason, this forcing then seemed to have a shorter relaxation time. Why such an interference would give a quicker response than a solar signal is unexplained (the response to volcanoes is fairly prompt, however).
The study by S&W has some suspicious results. When their simple ‘phenomenological thermodynamical model’ (PTM) is forced by a signal with shorter time scales (high-frequency response representing the ~11-year solar cycle), it produces weaker response than if the forcing has longer time scales (or lower frequency) – as expected. But if you add a long-term trend to the former, the amplitude of the high-frequency response diminishes further (their Figure 4, reproduced above): The amplitude of the higher frequency response in their upper panel (4mm measured in the print) had diminished by ~50% in the lower panel (2mm). This is probably because the relaxation time response has been increased between the two panels and is greater than 10 in the lower panel. The presence of a trend should not affect the amplitude of the higher frequency in such a simple linear system (see my reproduction above).
Their figure 5 (below) does not correspond with the discussion in their paper (see scanned part of the text). Again, their analysis is sloppy in the estimate of change, underestimating the observed temperature change (T(obs) in Fig 5a, the total warming is stated to be ~0.8K since 1900, but the figure suggests it is greater than 0.8K) and exaggerating the solar contribution T(sol). This way, the fraction T(sol)/T(obs) gives the impression of a more sensitive response to changes in the Sun. They then proceed to use the lower T(obs) estimate for Mann & Jones (2003) for the total temperature change (claiming 0.8K, although this is too low), but taking a solar contribution estimated from the Moberg et al. (2005) temperature with more pronounced variations (the right estimated warming should exceed 1.0K – not 0.8K as they claim). Hence the fraction of solar signal to total change T(sol)/T(obs) is spuriously inflated.
But what about GHGs if the sensitivity is so high and the relaxation time is so long? We know from laws of physics and lab measurements that the CO2 levels have been increasing and that CO2 absorb infra red radiation. In fact, the Mauna Loa observations done by infra-red gas analysers measure the absorbing properties of air samples – a pure GHG effect on a microscopic scale without feedback effects. The high climate sensitivity and long time delay suggested by S&W would be scary – imagine the GHG warming that is not yet materialised and would be in the pipeline! (Lindzen who doesn’t believe in the lagged response would indeed be surprised if this was the case!).
S&W propose two mechanisms which may amplify the response to solar variations: (i) GCR (here, here, here) or (ii) UV-radiation.
But S&W ignore the issue about the lack of trend in the GCR (Lockwood & Frohlich, 2007; Benestad, 2005), the fact that trends in the diurnal temperature suggest otherwise (IPCC, 2001, 2007), and that there is not a clear trend in the cloud cover. Thus, explanation (i) is not convincing.
The problem with the UV-explanation (ii) is that the stratosphere has been cooling – some of which is due to the ozone depletion. How could they have ignored that?
Finally, the paper oozes of vague but subjective and cherry-picked statements forming the impression that the climate and solar reconstructions of Mann & Jones (2003) and Lean (2000) (why not use more recent reconstructions, by the way?) respectively are less accurate than others. Apparently because these do not give the desired results.
The paper also offers some incorrect references (Kristjansson et al, 2004, do not support the notion that GCR affect the climate). Furthermore, their paper contains little physics, but is little more than a curve-fitting exercise with no cross-validation.
Thus, S&W make a number of unjustified assumptions and sweeping statements which turns it into a mere speculation. In a way, the conclusions are already given when S&W assume that the sun is the predominant cause from the outset. S&W presumes a desired conclusion when arguing that if the TSI variations are small but the temperature variations are pronounced, then this suggests greater climate sensitivity and vice versa. No surprise, their conclusion is that the sensitivity to solar changes is high. Any other conclusion would then be surprising, wouldn’t it?
If they were my students, I’d have flunked their paper.
Re 20, 24, 29, 34
Re 20 (Robert):
E.g.
Ammann C.M., F. Joos, D.S. Schimel, B.L. Otto-Bliesner, R.A. Tomas, 2007: Solar influence on climate during the past millenium: Results from transient simulations with the NCAR Climate System Model. PNAS, 104, 3713-3718.
Foukal P., C. Fröhlich, H. Spruit, T.M.L. Wigley, 2006: Variations in solar luminosity and their effekt on the Earth’s climate. Nature, 443, 161-166.
Bard E., M. Frank, 2006: Climate change and solar variability: What’s new under the sun? Earth and Planet. Sc. Lett., 248, 1-14.
Gray L.J., J.D. Haigh, R.G. Harrison, 2005: A review of the Influence of Solar Changes on the Earth’s Climate. Hadley Centre technical note 62.
Shindell D.T., G.A. Schmidt, R.L. Miller, and M.E. Mann 2003: Volcanic and solar forcing of climate change during the preindustrial era. J. Climate, 16, 4094-4107, doi:10.1175/1520-0442(2003)016.
Solanki S.K. and N.A. Krivova, 2003: Can solar variability explain global warming since 1970? J. Geophys. Res., 108, 1200.
Re 24 (Charles):
If you want to explain the temperature rise after 1970 by the solar activity increase in the first half of the century, you need a time lag reaction of about 50 years (or more). SW do not mention that, they are just talking about lagged reaction (large relaxation time), but do not consider, what that would mean and if there is any hint in the data that would point to a corresponding relaxation. However, at the end they are talking about a time lag of 6 to 12 years which would exclude a current influence of the solar activity rise before 1950.
Re 29 (Henning):
From SW: Our calculations also assume that the observed secular preindustrial warming before 1900 is induced by the contemporary solar activity increase.
Re 34 (Robert):
The problem with SW is, that they try to get a possible percentage of solar influence as high as possible, regardless of the likelyhood of their assumptions. You are right to point out that per se the search for an upper limit is all right. However, some of their assumptions are very unlikely or questionnable. They assume e.g. that before 1900 the whole temperature trend is due to TSI increase and that the whole variability of global temperature on the interannual (about 10y) time scale is due to the 11y solar cycle (these are the two constraints they build their model on), and that 1 Wm-2 equals 1 K (very interesting…).
Besides, their difference (citing themselves) comparing sun cycle 21-22 to 22-23 of ACRIM (0.45Wm-2) is also the highest one can find, since their cycle 21-22 does not begin at the maximum of 21 but ends at maximum of 22. My estimation for the cycles encompassing the maxima (1979- 1991, 1992 – 2000; the definition of the time of maximum is somewhat arbitrary, dependent on averaging) gives a difference of only about 0.25 Wm-2 for ACRIM, which is half of the SW value. For the averages of cycle 22 and 23 (1987- 1996.5, 1996.5 – 2007.3) I get a difference of about 0.04 Wm-2.
Re 48 & 49,
I do know all you say, I have discussed with the authors many times and filed all the relevant studies, over 6000 now. Besides uncertainties I’m always looking for alternative explanations to everything, and first after critical scrutiny we’ll see (or not) where the beef may lure.
Well, when I take the big picture, in last three decades I see three major incidences
– the 1977/78 global shift,
– the 1998 super-el Nino, and
– the enormous burst of warm water to Arctic Ocean observed from 2004 on
About the latest one please see
Polyakov, Igor V., et al., 2005. One more step toward a warmer Arctic. Geophys. Res. Lett., 32, L17605, doi:10.1029/2005GL023740, September 9, 2005
Extract from the Abstract
“This study was motivated by a strong warming signal seen in mooring-based and oceanographic survey data collected in 2004 in the Eurasian Basin of the Arctic Ocean. The source of this and earlier Arctic Ocean changes lies in interactions between polar and sub-polar basins. Evidence suggests such changes are abrupt, or pulse-like, taking the form of propagating anomalies that can be traced to higher-latitudes. …”
AGU Highlights:
“Arctic Ocean waters warm suddenly
New research on water flowing from the North Atlantic Ocean into the Arctic provides evidence that the Arctic Ocean is warming. Polyakov et al. measured the temperature, salinity, and velocity of the Atlantic Water, a warm, salty layer (150-900 meters [500-3,000 feet]) of ocean water that flows through the Norwegian Sea into the Arctic Ocean. The temperature of the Atlantic Water entering the Arctic Ocean increased dramatically in 2004, warming in two abrupt stages in February and August. The anomalously warm water is currently flowing along the basin margins toward the interior of the Arctic Ocean. The authors suggest that enhanced westerly winds in the North Atlantic pushed warm water into the Norwegian Sea, and from there it flowed into the Arctic Ocean. These winds are due to changes in atmospheric conditions, but the authors say more evidence is needed to determine if the associated warming is the result of long-term change or part of a recurrent climate cycle. The authors’ observations do indicate, however, that the Arctic Ocean is currently warming, a trend that could reduce Arctic ice cover and influence ocean processes in more southerly regions.”
See also
Sitnews June 12, 2005 at
http://www.sitnews.us/0605news/061205/061205_ak_science.html
Extract:
“…A rise in water temperature from 0.4 to 0.8 degrees Celsius (32.7 to 33.4 degrees Fahrenheit) is a big change in the stable environment of the Arctic Ocean, said Dmitrenko’s colleague, Igor Polyakov, who also works at the International Arctic Research Center in Fairbanks.
“It’s as if the planet became warmer in a single day,” Polyakov said.
Interested in the pulse of warm water, Polyakov contacted oceanographers from around the world to backtrack the water on its path to the high Arctic. Norwegian scientists have moored stations in the Norwegian Sea, and German scientists monitor stations in Fram Strait, between Greenland and Svalbard. Using information from those stations and others, Polyakov and his coworkers found that the warm water passed Norway in 1998 and took about six years to reach the mooring station north of the Laptev Sea. That warmer water now resides in the Arctic Ocean, where it will remain for years caught up in currents that swirl counterclockwise in several giant basins north of the world’s landmasses…”
….
Well, besides these three huge incidences originating from the oceans other climatic events and trends are quite trivial. Speaking of climate I always exclude weather events.
Finally, when we return back to the main issue of this discussion, the Sun, please see the new study
Usoskin, Ilya G., Sami K. Solanki, and G.A. Kovaltsov, 2007. Grand minima and maxima of solar activity: new observational constraints. Astronomy & Astrophysics Vol. 471, No 1, pp. 303-307, August III 2007, online http://cc.oulu.fi/~usoskin/personal/aa7704-07.pdf
Re: #46 (Pete)
Regarding PMOD vs ACRIM, the information on the ACRIM website is only one side of the story. Interested readers should also study this paper by Frohlich, and I’ve posted on that topic myself.
Re Gavin: “RC is a volunteer effort. No one gets paid for anything. Our annual expense are $30 for the domain name registration.”
Just the kind of full financial disclosure I’d like to see from other sources of putatively scientific information! To cut to the chase: the single property shared by the “science” of almost all the stuff RealClimate takes pains to debunk is corruption – plain and simple. I don’t mean to sound moralistic in this assertion, but only to point out an obvious thing
[edit – please don’t make unsubstantiated specific allegations]
Thank you for your conscientious edit (really).
It’s a challenging concept to frame dispassionately, which is my goal here – obviously, you’ll hold this one back if you find it inappropriate, and I can appreciate that. One more try…
A phenomenon which might be called “scientific fraud” is a feature, in my view, not only of several shoddy papers I’ve seen of late, but also an attribute which attaches to the authors and publishers of those papers (particularly in cases where the same cast of characters keeps coming up with the same tired old nonsense – I don’t mean to include honest mistakes in this category). It seems like a fairly bland assertion to me, and yet it is tricky to posit in a manner which doesn’t upset the lawyers.
This phenomenon has a rich and storied history as long as that of science itself – so in a way my suggestion is that historical precedents for “scientific fraud” are ripe for the plucking, in case they inform your discussion.
[Response: Shoddy is not necessarily fraud. Ignorant is not fraud. Deliberate obfuscation or repeating tired old nonsense is not fraud either (though it doesn’t do much for ones scientific credibility). Faking data, doctoring photographs or samples is fraud though. In the cases we have been discussing the problems don’t add up to anything approaching that and the accusations that they do, don’t lead to very much except to ever more expansive rhetoric. Sticking to the issues and assuming good faith (unless it is clearly not warranted) is more fruitful in the end. – gavin]
Re: #53 (tamino)
I do appreciate this Tamino, and I have previously read your thread in which Dr Willson himself appeared :)
I just wanted to highlight that PMOD(composite) is still stitched together from 7 segments from 1980: ERB>ACRIM1>ERB>ACRIM1>ERB>ACRIM2>VIRGO then reconciled to the VIRGO scale and then fitted into a previous proxy reconstruction pre 1979.
Whereas ACRIM(composite) is stitched together from 1980: ERB>ACRIM1>ERB>ACRIM2>ACRIM3.
I just think both methods are unsatisfactory really, but it’s the best we have from real data. The current ACRIM 3 / SORCE differneces just show the uncertainties currently existing in this field.
Any paper using either of these, in my view, is well advised to model results and conclusions on both these composites, as has happened with S&W. Whereas the Royal Society F&L paper earlier this year chose to ignore the ACRIM composite completely. Who’s the more incorrect in this situation? With S&W you have a choice it seems to me!
In 52, Tim makes the extraordinary claim that “besides these three huge incidences originating from the oceans other climatic events and trends are quite trivial.”
Tell it to Perth and Sydney.
Re #45 Cobblyworlds:
The problem I saw was not with fig 6b vs 5b, but in the last decade of 6b where the two modeled temperatures deviate by 0.1 degrees despite the two TSI curves being the same for the last six decades. But also why is there almost no difference between the two modelled temperature curves both in fig 5 and 6 pre-1950 where the two TSI curves deviate by up to 1.5 W/m2? The only sensible conclusion seems to me that these deviations demonstrate how non-physical the results are.
Timo,
Thanks for Usoskin’s latest contribution. After a quick perusal, it looks interesting–particularly the lack of periodicity seen. A couple of comments and questions. The statistics are really not good enough to make detailed conclusions about distributions. In particular, it is not clear to me that the distribution of Minima distributions would necessarily be bimodal. It could be simply long-tailed, with the clustering in the second “mode” being due to statistical fluctuations. This is particularly true, since these long-duration events are infrequent, and the reconstructions may have more uncertainty the further back one goes. I don’t see any obvious implications for current climate studies of models.
#9, Urs, “This is funny, since one of the beloved sceptic arguments is that the CO2 increase during ice age cycles lag the temperature increase by more than 600 years. So we will still have to wait a few hundred years to see the CO2 increase due to the temperature increase since the Maunder Minimum (apart from evidence by the isotopic footprint).”
We don’t have to wait 600 years, all we have to do, is go back 600 years, use a proper proxy and look for a 1407 spike in CO2… Thank goodneess for contrarians pointing out the right direction. Now they will have irrefutable proof that they are full of ideas devoid of verification.
When Tamino (#52) refers to Klaus Frölich’s new paper (and Gavin Schmidt has used the same reference), it’s proper to refer to the following new paper, too, and to the comments it has invoked:
Lockwood, Mike, and Claus Fröhlich, 2007. Recent oppositely directed trends in solar climate forcings and the global mean surface temperature. Proc. Royal Soc. A, in press, July 2007, online http://www.pubs.royalsoc.ac.uk/media/proceedings_a/rspa20071880.pdf
Abstract
There is considerable evidence for solar influence on the Earth’s pre-industrial climate and the Sun may well have been a factor in post-industrial climate change in the first half of the last century. Here we show that over the past 20 years, all the trends in the Sun that could have had an influence on the Earth’s climate have been in the opposite direction to that required to explain the observed rise in global mean temperatures.
5. Conclusions
There are many interesting palaeoclimate studies that suggest that solar variability had an influence on pre-industrial climate. There are also some detection–attribution studies using global climate models that suggest there was a detectable influence of solar variability in the first half of the twentieth century and that the solar radiative forcing variations were amplified by some mechanism that is, as yet, unknown. However, these findings are not relevant to any debates about modern climate change. Our results show that the observed rapid rise in global mean temperatures seen after 1985 cannot be ascribed to solar variability,
whichever of the mechanisms is invoked and no matter how much the solar variation is amplified.
….
Well, very, very determined position.
Yet, please see e.g.
Reference Frame / Lubos Motl July 22, 2007
“Nir Shaviv: Why is Lockwood and Fröhlich meaningless?
One of the newest articles at RealClimate.org contains a link to the full text of a recent article by Lockwood and Fröhlich who argue that “all” potential aspects of the Sun in the last 20 years that could be responsible for warming in that period went the wrong way. Well, there are many questions: for example, was there a warming that one should talk about? There wasn’t one in the last ten years.
A more important question is whether their whole article is correct…..”
Please see also
Reply to Lockwood and Fröhlich –
The persistent role of the Sun in climate forcing
Svensmark, H. and Friis-Christensen, E.
Danish National Space Center
Scientific Report 3/October 2007
online http://www.spacecenter.dk/publications/scientific-report-series/Scient_No._3.pdf/view
…..
Well, my only comment is that experts disagree.
As far as I can see, also in the foreseeable future.
[Response: Ahh… experts disagree (about what we are not told), therefore we know nothing. Perfect! Actually they don’t. Even S+FC’s latest (unpublished) piece accepts that the trend in temperature cannot be explained by the CR data (since they remove the trend from their analysis). Thus, we actually find an agreement! Maybe we do know something? – gavin]
Re #59 Ray:
I ask Ilya Usoskin. My dear friend Ilya usually is willing to communicate, if not too busy.
Errata, its easier, we rather need to look for a 1407 spike in temperature, or any other recent 600 year temperature to CO2 correlation, lets say something known like 400 to 1000 AD correlation etc.. .
Re Gavin: on fraud (#55)
I’ve very much taken your response to heart. I think you are right about what is productive and non-productive discussion, an insight so key to making RealClimate pertinent. I learn even more than I expect to here. Thanks.
Re # 61 Gavin’s comment:
Link to Nir Shavis’s analysis (above) is
http://motls.blogspot.com/2007/07/nir-shaviv-why-is-lockwood-and-frohlich.html
I further copy a bit as follows:
“…L & F state that from 1985, there is a discrepancy between solar activity, which decreased, and the global temperature, which increased. Hence, solar activity cannot explain the observed warming. This conclusion, however, is flawed for several reasons….
So why has the temperature continued increasing even though the solar activity diminished? This has to do with the second point, which is very important, but totally ignored by L & F.
L & F assume (like many others before) that there should be a one-to-one correspondence between the temperature variations and solar activity. However, there are two important effects which should be considered and which arise because of the climate’s heat capacity (predominantly the oceans). First, the response to short term variations in the radiative forcings are damped. This explains why the temperature variations in sync with the 11-year solar cycle are small (but they are present at the level which one expects from the observed cloud cover variations… about 0.1°C). Second, there is a lag between the response and the forcing. Typically, one expects lags which depend on the time scale of the variations. The 11-year solar cycle gives rise to a 2 year lag in the 0.1°C observed temperature variations. Similarly, the response to the 20th century warming should be delayed by typically a decade. Climatologists know this very well (the IPCC report, for example, include simulation results for the many decades long response to a “step function” in the forcing, and climatologists talk about “global warming commitment” that even if the CO2 would stabilize, or even decrease, we should expect to see the “committed warming”, e.g., Science 307), but L & F are not climatologists, they are solar physicists, so they may not have grasped this point to the extent that they should have….”
…
Hopefully the link above opens to everyone interested to read the full text.
[Response: Ahh…. so the acceleration of the warming in the last 30 years is because of the solar forcing increases in the 1940s? And this is the expected outcome from a simple model with an ocean heat capacity? Hmm… maybe you could point us to a simple model that shows this behaviour if it is so obvious? All of the ones I have seen respond to a step with an exponentially decreasing warming, not an ever increasing one. But not even S+FC make this argument! They state clearly that:
Thus they are no longer claiming the trend is due to GCR. Why do you insist that it is? – gavin]
[Response: To re-iterate one of the points made here in this thread: It’s a fact that the global mean temperature leveled out after 1940 and even decreased a little until 1970. A delayed response from a solar forcing – if it were important – would on the other hand suggest strongest warming in this period. So you need to answer: ‘Can a response to a forcing wait and then bounce up after a period of inertness?’. The alternative explanation is that there are other factors which are more important than solar forcing. One such candidate is aerosols, but the pronounced warming since 1970 is still difficult to explain in terms of solar forcing. However, if the climate sensitivity is high for these factors, why should it be any less for increased GHG? After all, AGW surely involves many of the similar feed-back processes e.g. involving changes in vapour, snow/ice albedo, lapse-rate, and clouds. -rasmus]
Timo (#61): You claim that “experts disagree” and yet the “expert” you cite states “there wasn’t [a warming] in the last ten years”. That, in my opinion, means that your “expert” is only an expert in obfuscation, and not in real climate science. Look at either the GISS or HadCrut temperature records: do a multiple year smoothing (try 5 years for example) and you’ll see a clear continuing warming signal.
Meanwhile, Svensmark et al. (these were the same folks that in the early 90s attempted to attribute recent warming to solar trends, only to have it pointed out that their 30 year averaging algorithm meant they couldn’t actually talk about anything post 1960 or so, right?) detrend their signal by 0.14 K/decade to get a match to a cherry-picked tropospheric data set (claiming that some mysterious natural greenhouse feedback is as likely as anthropogenic GHGs to account for it), and claim that their ocean and troposphere data sets are more reliable than surface temperature records? And also claim that figure 1e is “roughly flat” since 1998, when even the roughest attempt at statistical analysis beyond eyeballing it shows that it isn’t at all flat.
All in all – I find your “experts” quite lacking.
Gavin, you suggested climate science is in its adolescency. Where is your current focus? What else could be discovered that we don’t already know? Is your main job from here on out media relations? Why not just turn off your Blueice and go home?
[Response: There’s tons to do: Getting a grip on D/O events, understanding the last deglaciation, understanding the variability in ‘interglacial times’, aerosol impacts, improving the models, ice sheet dynamics, cloud resolving etc. No need to go home just yet. But if all you want to know about is the impact of greenhouse gases, you already know enough to act. – gavin]
Svalgaard is presenting at the 8:00 AM Wednesday session (GC31B), presided over in part by Scafetta and Willson. As Erik noted, Svalgaard is talking about minima being the same, but I believe he’s referring to minima of the 22-year cycles, which would imply that the maximas can’t have much variation either, leading to the conclusion that there isn’t a century-scale solar forcing (as opposed to a decadal one, which would refer to the 22-year cycle).
TI: (No?) Century-scale Secular Variation in HMF, EUV, or TSI
AU: * Svalgaard, L
EM: leif@leif.org
AF: ETK, Inc., 6927 Lawler Ridge, Houston, TX 77055-7010, United States
AB: Recent work suggests that the Heliospheric Magnetic Field (HMF) strength, B, at each sunspot minimum varies but little (less than a nT). The variation of B within a solar cycle seems to be due to extra (and likely closed) magnetic flux added by Coronal Mass Ejections (CMEs) riding on top of a “floor” of somewhere between 4 and 5 nT, leading to the conclusion that the open magnetic flux is nearly constant with time, and that, in particular, there is no secular variation of the open flux. B inferred from geomagnetic data back to the 1840s further support this conclusion. In fact, B for the current cycle 23 matches well B for cycle 13, 107 years earlier. The amplitude rY of the diurnal variation of the geomagnetic Y-component is an excellent proxy for the F10.7 radio flux and thus also for the EUV flux (more precisely, the FUV, as the Sq current flows in the E layer). As for the HMF there seems to be a “floor” in rY and hence in F10.7 and hence in the FUV flux, thus the geomagnetic evidence is that there has been no secular change in the background solar minimum EUV (FUV) flux in the past 165 years. Direct measurements (although beset by calibration problems) of the Total Solar Irradiance (TSI) from satellites have only been available for 30 years and indicate that solar irradiance increases with solar activity. Correlating mean annual TSI and sunspot numbers allows one to estimate the part of TSI that varies with the sunspot number. If TSI only depends linearly on the sunspot number then irradiance levels during the Maunder Minimum would be similar to the levels of current solar minima. But TSI is a delicate balance between sunspot darkening and facular brightening, and although both of these increase (in opposite directions) with increasing solar activity, it is not a given that there could not be secular variations in the relative importance of these competing effects. Reconstructions of TSI, all postulate a source of long-term irradiance variability on centennial time scales. Each group of researchers have their own preferred additional source of changes of the “background” TSI, such as evidence from geomagnetic activity, open magnetic flux, ephemeral region occurrence, umbral/penumbral ratios, and the like. The existence of “floors” in HMF and FUV over ~1.6 centuries argues for a lack of secular variations of these parameters on that time scale. I would suggest that the lack of such secular variation undermines the circumstantial evidence for a “hidden” source of irradiance variability and that there therefore also might be a floor in TSI, such that TSI during Grand Minima would simply be that observed at current solar minima. This obviously has implications for solar forcing of terrestrial climate.
Regarding Nick #13 and later responses.
I have to agree with Nick”s response, at least that was the thought I had when reading the article. In other words if S&W claim solar is the only forcing worth considering and feel the cooling is due to delay only and not Aerols etc., Rasmus could be more clear. I am glad Nick asked this question better than I could and for Gavin’s reply.
I have to admit the discussion though is a bit too technical for me to follow. But I will take a few more passes at it.
#58 Erik Hammerstad
Sorry about that, I misread.
They use different values of relaxation time reponse(Tau), and insolation scaling factor(alpha). I think the main factor in creating the effect you describe would be the value of Tau. Fig 6a and both of 5 show lesser deviations
As they’ve derived the values of Tau and Alpha from the whole of each respective Lean/Wang Dataset I’d expect the parameters to differ and S&W’s defence to what you say could be that the difference is down to the difference between Lean & Wang.
That one aspect doesn’t bother me about the paper. Its unphysical because it’s trying to get agreement between one variable, in a multivariable context. I accept that they could be argued to show the (surely accepted) pre-1950 dominance of solar forcings on a multi-decadal scale. Note that their graph has significant enough deviations from observations for the “wiggle room” needed for other “natural” factors.
Indeed whilst I certainly wouldn’t rely upon this paper it seems to me to generally suggest Mann03 rather than Moberg05 is closer to reality. That’s because the latter 20th Century deviation suggests the sort of room CO2 increases take up in attribution studies. With the same sort of deviation from modelled results in the 1950s (must find out if it’s known what that was due to). e.g. http://www.globalwarmingart.com/wiki/Image:Climate_Change_Attribution_png Note – I am comparing northern hemisphere vs global here- so it’s rough.
If I had to bet on what I think is the most “true” of the four graphs I’d bet fig5a – but that’d be a hunch nothing more. On balance though, I’m just not keen on “phenomenological approaches”, even when they support the theory of AGW (there was a statistical attribution study that did a while back – but I forget the names now).
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I’ve got some sympathy with Robert A Rohde, but given S&W’s track record and notably paragraph 7. Which seems to me can only be placed there to confuse those who don’t know of the multiple strands of evidence that support the conclusion that the rise in CO2 is due (substantially) to fosil fuel burning.
Is the paper about TSI/GAT attribution or about CO2? What they’re doing there is superfluous to their scientific purpose, as far as I can see it’s inclusion demonstrates their real purpose – to hoodwink those unfamiliar with the wider body of evidence.
Svalgaard explains that S+W 2007 is based on bad data:
“Scafetta & West 2007 uses and compares the TSI [Total Solar Irradiance] reconstructions by Lean 2000 and Wang et al. 2005. Lean’s is pretty much ruled out as the secular increase since the M.M. [Maunder Minimum] is much too large. Wang’s has no secular change [check the minima values] up to 1900, but then takes off during the 20th century, largely based on the Lockwood open flux doubling. Since not even Lockwood believes the doubling any longer, there is no reason for Wang and us to believe in it either, and the large increase [S&W, Figure 3] in TSI during the 20th century is simply not there. Therefore the solar influence is also not there. So, now we have two things to explain:
1) the warming during 20th century, and
2) the cooling during the LIA
None of which are caused by the sun.
So, we invoke Natural [other than solar! other than solar! other than solar! other than solar!] Causes [NC] for the cooling and Human causes [HC] for the warming. Doesn’t sound right to me.”
On those latter points, IIRC there are perfectly good reasons why the anthropogenic causes would net out to warming, and the LIA could only be a problem if it is a) assumed to be a substantial global phenomenon (a point which is at least in some dispute) and b) not largely explainable by a combination of natural variability and volcanic activity. But is there any validity to the supposition (which Svalgaard admitted was based on very little direct knowledge of the models) that knocking out the solar trend from the first half of the twentieth century would throw the models for a loop? I said I didn’t think so, but there I’m on very shaky ground. Gavin?
#52 Timo Hämeranta
No problem with asking the awkward questions, when it’s done to provoke fruitful re-examination of things which are tacitly accepted.
– the 1977/78 global shift,
– the 1998 super-el Nino, and
– the enormous burst of warm water to Arctic Ocean observed from 2004 on
also
– 1990s shift in modal tendency of the Arctic Oscillation.
– what looks like an upward trend in NATL cyclone activity.
etc
All happening at the same time as increasing CO2 levels (a gas expected to cause warming on a global average basis) and a “coincidental” global warming. A warming that, if not forced by internal variability, does affect the sort of climatic phenomenae we expect. e.g. Coral research suggesting a predominant EN state in warmer periods.
By the way.
Check out the graph of seasonal area(extent?) at Cryosphere Today: http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/seasonal.extent.1900-2007.jpg
It’s apparent that there’s been a summer warming trend long before 2004 (some small factor being “amiplified” by ice-albedo feedback?). And the flushing out of perrenial ice due to the +ve AO mode happened in the 1990s. With the reduction of the damping factor that is perrenial ice, natural changes are then able to have an impact they didn’t have before.
[Response: RC is a volunteer effort. No one gets paid for anything. Our annual expense are $30 for the domain name registration. – gavin]
Wow.. really. Where can I get a free host and web server for my domain. Thats a sweet deal. Especially for the bandwidth that a site like this consumes. Inquiring minds want to know.
[Response: Inquiring minds should simply try looking. This is what we said when we started. – gavin]
Help me out, I don’t grasp how “Getting a grip on D/O events, understanding the last deglaciation, understanding the variability in ‘interglacial times’, aerosol impacts, improving the models, ice sheet dynamics, cloud resolving etc.” won’t impact my understanding of the role of greenhouse gases, and what I should do about them.
We are somewhere in the middle of an ‘interglacial time’, are we not?
[Response: Sure, but this is the only one CO2 has reached 380 ppm and is still climbing. We are not going to learn from past interglacials what that does (since it hasn’t happened before), but we may learn something about the stability of the ice sheets, ecosystem and ocean circulation dynamics in those regimes. It all might feed into improved model evaluation, and conceivably improve predictability into the future. These factors are the most uncertain going forward, but there’s tons of stuff that is pretty certain that no amount of D/O-related research is going to shift. Bottom line, tons of science to do, probably minimal change in what policy-makers will hear. – gavin]
[Response: Inquiring minds should simply try looking. This is what we said when we started. – gavin]
So, you are ‘hosted’ by a sock puppet for an environmental PR firm that also represents groups like Greenpeace and other environmental firms who do have a vested financial interest in promoting AGW. Based on the standard that skeptics are held to here, with regards to similar ties to industry they are immediately dismissed without comment on the merits of their arguments. Why should your commentary not merit similar treatment (Just because they don’t pay you doesn’t mean that your access to this venue is not of some value to you.) Again, based on the standards for credibility that you have repeatedly endorsed (usually) indirectly by allowing them to pass unchallenged, you too represent a biased viewpoint and your credibility too is questionable.
[Response: Credibility is a funny thing. I generally reserve it for people who have been conscientious about they do, have a track record of not dissembling or passing disinformation, who do not misrepresent what others say and who argue honestly. I have never argued that industry money ipso facto removes credibility – people like Michaels lose credibility due to their actions, not their (anonymous) funders. But if you think we’re cheap enough to be bought off with a free server account, try buying us lunch – who knows what we’ll do for that? – gavin]
cbone, congratulations. That may well be the most pathetic post I’ve ever seen here on RC. Golly, someone is concerned about climate change and so they host a group of climate scientists who answer questions (FOR FREE) for blockheads like you. Oh my, what if they take away the server account? Then Gavin et al. might only be half as overworked as he is and that would be tragic for him, wouldn’t it?
Your swiftboating technique is rather reminiscent of James Inhofe’s denunciation of Dr. Jim Hansen for “taking money from a liberal think tank”. Of course you do a little digging and find that Hansen won a prize from the Heinz Family Foundation for his climate work–in 2001, long before John Kerry even thought about running for president. Karl Rove, is that you?
[Response: I start to think that such a think – sulking because the number of rational arguments has dried up – is to be expected. But, please, judge us on what we write, the arguments that we present, the empirical/modelling evidence we use, and the logic that we follow. -rasmus]
Re # 75 cbone: “…you too represent a biased viewpoint and your credibility too is questionable.”
To support your allegation of bias by the RC moderators, you need to provide evidence that Environmental Media Services somehow influences the research they (RC moderators) conduct or the papers they publish, or somehow exerts editorial influence over the content of RealClimate threads – if you have evidence of such influence, please share it. Inquiring minds would love to know.
There are a number of papers that predict the sun is moving to a Maunder minimum. (Solar minimums have been shown to occur every 200 years and the Dalton minimum was 200 years ago.) We should have an opportunity to determine how much of the 20th century warming was attributable to solar as compared GWG, if the solar minimum occurs starting cycle 24.
Any thoughts concerning what to expect?
The following is an explanation of the mechanisms which the sun is hypothesized to modulate planetary clouds.
Solar mechanisms – Electroscavenging
The 20th century solar contribution to global warming is hypothesized to be due to the process called “electroscavenging” which reduces planetary cloud independently of GCR flux.
Electroscavenging is caused by electrostatic charge which is created by high speed solar wind bursts. The high speed solar winds bursts were created by coronal holes that moved to the solar equator at the end of the solar cycles 21 and 22. The electroscavening processes removes clouds and masks the increase in GCR at the end of the solar cycle.
The following is a paper that explains the different mechanisms by which solar activity can modulate clouds. See the figure 3.1 for a diagram that shows how electroscavenging removes cloud forming ions.
“Atmospheric Ionization and Clouds as Links between Solar Activity and Climate” By Brian Tinsley and Fangqun Yu
http://www.utdallas.edu/physics/pdf/Atmos_060302.pdf
“Electroscavenging depends on the buildup of space charge at the tops and bottoms of clouds as the vertical current density (Jz) in the global electric circuit encounters the increased electrical resistivity of the clouds. Space charge is electrostatic charge density due to a difference between the concentrations of positive and negative ions.
The magnitude of Jz depends not only on the GCR flux, but also on the fluxes of MeV electrons from the radiation belts, and the ionospheric potentials generated by the solar wind, that can vary independently of the GCR flux.”
Ahhhm… regarding the reliability record of this website (technically) the host can – if anything – only be suspected to actually sabotage RC. ;-)
Re # 65 to Gavin:
You do know I only forwarded information for consideration, and personally haven’t argued anything about GCR.
Re # 72 to ‘CobblyWorlds’:
I know that ‘there’s been a summer warming trend long before 2004’, it’s also in the papers I have forwarded.
But let’s concentrate in this discussion to the Sun.
This is completely off-topic, but it’s good news for a change, so I’d like to share it with you all:
You may be aware that Australia recently had an election and that the government of John Howard (a good mate and supporter of George Bush) has been crushed by the left leaning Labor Party (led by Kevin Rudd with the support of the Australian Greens. Howard himself lost his seat to a very switched on former journalist from the Australian Broadcasting Commission – Maxine McKew.
It is widely recognised that the backward stance of Howard with respect to climate change played a significant role in the change of government.
Labor has announced that it will sign the Kyoto protocol and work with other nations to help ensure that the next one is effective. It’s notable that during the election, the national mining and energy labor union supported Labor and ran advertisements calling for action on climate change. The new leader of the outgoing ‘Liberal’ party has declared support for Labor’s stance on Kyoto (in Australia the ‘Liberal’ party are the right-wing conservatives). Given the amount of coal and steel we sell to China, the fact that Mr Rudd speaks fluent Mandarin makes for interesting possibilities during international dialog on the issue.
Now to top it all of, Rudd has declared that his minister for the environment, heritage and the arts will be Mr Peter Garrett – the former head of the Australian Conservation Foundation (equivalent to Sierra club in the US and the RSPB in Britain). And in addition, Ms Penny Wong has been appointed as Minister for Climate Change and Water (yep it’s so important they have appointed a dedicated minister). The new Deputy Prime Minister Julia Gillard is the first woman ever to hold that role.
Besides holding power nationally, the Labor party also holds power in every state and territory in the nation. These governments have been battling the national government for years to get meaningful greenhouse policies in place.
It’s always easy to be cynical (‘no matter what, you always get a politician’). But this new crop includes some of the most committed, intelligent, environmentally savvy, socially progressive people in the country.
To find the highest ranking right-wing politician in Australia you now have to look to the Mayor of Brisbane.
It’s like some kind of miracle!
Within a month or two, the US will be the only hold-out on Kyoto.
Urs #51:
Thanks for the references.
I am a little surprised you included Solanki and Krivova though. That paper goes through basically the same curve fitting approach as S&W with basically the same result. In other words, by crudely fitting solar variability to temperature, they also get something like 50% of the 20th century warming “attributable” to solar variation, with a smaller fraction of the recent warming. (They state it as “we conclude that the Sun has contributed less than 30% of the global warming since 1970”, which is arguably more severe than the typical S&W result.)
I don’t actually believe that 50% of the 20th century is solar, but I do think simple limits arising from data-driven models provide a useful counterpoint to the very complex and opaque climate models usually used (see, for example, Ammann et al. in Urs’s references). When it comes to communicating climate change to others, it is lot harder to convince people to believe a GCM they can’t possibly understand than to have them compare data on a screen.
Richard Rohde,
Solanki et al. is constructed as a reductio ad absurdum–they admit that the assumptions they are making are unreasonable and then say, “See, even making these unreasonable assumptions, solar variability could only account for ~50% of the last century’s warming. S&W may be equally absurd, but they are seeking to justify those absurdities. As such, S&W deserve no more credit for a reductio ad absurdum argument than a tenor whose pants rip in “The Marriage of Figaro” deserves to be called a comic opera genius. The audience would be laughing as much if it had happened in “Madame Butterfly” or “Faust”.
It is unfortunate that people get wrapped around the axle wrt models. They are tools to aid in physical understanding and intuition–nothing more. If people go in with that understanding, and if they understand that much of the model is constrained independently of the data under consideration, the inescapability of anthropogenic causation becomes manifest.
#80 You missed the most important thing about the good Mr. Garrett–lead singer for Midnight Oil.
(Incidentally, some of the Aussie papers seem to suggest that Garrett has been given half a ministry, with Wong getting the other half, because of gaffes made during the election campaign).
William Astley, I notice your reference has yet to be published. How was it reviewed? I also see some significant problems–why did we not see rapid warming in the late 1800s, for instance. Solar forcing also has a lot of trouble reproducing qualitative features of the warmingMoreover, the fact of the matter is that CO2 sensitivity is fixed by several independent lines of evidence. Thus, if there is another significant contributor, it will likely affect our estimates of quantities we DON’T know (e.g. aerosols) rather than those we do (e.g. CO2). Thus, any decrease in solar forcing will buy at most a temporary reprieve (and probably a return to complacency) before the end of the Minimum brings the return of warming with a vengeance. That CO2 is responsible for most of the current warming is really inescapable. See:
https://www.realclimate.org/index.php/archives/2007/11/global-dimming-and-global-warming/
These data are inconsistent with a solar mechanism.
From the paper at (3):
“PTM assumes that the climate system, to the lowest order approximation, responds to an external radiative forcing as a simple thermodynamical system, which is characterized by a given relaxation time response t. This should be a valid approximation for small variation of the input forcing.”
Why?
Making the variation small does not necessary alter the dynamics of a system. I do understand that if the system is presumed to be non-linear it may be approximately linear for small forcings.
However if the model is invalid (i.e.. does not have a single time constant) making the forcing small will not change matters.
For instance if the system contains momentum it can contain resonances or more generally behave with different phase delays and amplitude responses at different frequencies. If it has resosances they will not go away just because you tap the bell lightly. It will still ring.
The system does contain momentum and is capable of oscillations.
If this was an ordinary investigation one might use solar variation as a probe to investigate the response of the system to a forcing with an eleven year period. As we cannot determining the attenuation of the response directly (climate sensitivity is not sufficiently well known) we only have the phase to work with. Plus if we are lucky and the forcing contains not just a fundamental frequency but also higher harmonics we can examine the relative amplitudes of the harmonics.
From the paper:
“We observe that both properties are expected for the climate system where it has been found that the climate sensitivity and the time lags to a forcing decrease with the frequency of the forcing because of the damping effect of the ocean and atmosphere thermal inertia”
When analysing cyclic forcings it is the phase not the time lag that you need to investigate. Their simple model would predict that as the amplitude of the response decreases with increasing frequency the phase delay should approach pi/2 (90 degrees). Now phase is not mentioned in the paper and it is critical to the analysis.
If the amplitude to long period forcings is 3 times that for the 11yr cycle then the 11 cycle should be delayed by about 0.4 pi or 70 degrees or 2.15 years (for the fundamental frequency or first harmonic) higher harmonics ought to be highly attenuated ( the third by the factor 9 the fifth by a factor of 15).
As far as I am aware “Tung & Camp (2007)” (not quoted in this paper) did not address the phase delay explicitly but their Fig 2c does not seem to show signs of the required time lag (2 yrs+) throughout most of their period (1959-2004) except at the extremities (1959-1963) and (2000-2004) in the middle part it appears to be closer to 1 yr. (This is just my eye-balling)
If this is the case it has serious implications for even their simple model. It would put their factor of 3 for the attenuation as an upper limit and it will in turn give an upper limit 5 yrs to their time constant. They prefer a range (6-12 yrs).
I believe that if they looked at both aspects of their model (amplitude and phase) they might come to the conclusion that they give contradictory results. They might be wise to consider whether this is due to the data or the inadequacies of the model.
Best Wishes
Alexander Harvey
Re Craig Allen @ 81: “Within a month or two, the US will be the only hold-out on Kyoto.”
Not quite, the minority Conservative Harper government in Canada is still very much “holding out,” having stated that although Canada signed Kyoto, it can not and will not meet its Kyoto commitment, having never seriously made any attempt to do so under the past two Liberal governments.
Re: Ray #85,
The paper William references appeared in the book: “Solar Variability and its Effects on Climate” published by the AGU in 2004.
For what it is worth which is probably not much I have had a look at the NOAA temperature data for 1980-2002 (all.land_and_ocean.90S.90N.dat) hopefully this is a good source.
It is relatively easy to find a ~0.1C pk-pk signal but it peaks around (1989/1990) and (2000/2001) and troughs around (1984) and (1995/1996) which I guess makes it in phase with the solar cycle (actually slightly leading). Not I feel an answer that would please them.
There is another snag. We only have two cycles so the resolving power is very small. The 11 cycle is not at a spectral peak which in fact occurs at ~8.5yrs ~0.15C pk-pk. Such peaks can occur for no apparent reason they are commonly just happenstance but 11yrs is too close to 8.5yrs to be resolved seperately with just 22yrs of data. So maybe there is a signal or maybe there is not.
BTW I tried the same trick as Tung & Camp in order to account for volcanoes (remove the data for 1982/83 and 1992/93) which are perilously close to and 11yr periodic forcing but it made only a small difference putting the peak about 6 months to 1 years later (where I have given a second figure above it is for the “devulcanoed” data).
Best Wishes
Alex Harvey
I would be obliged for a correction I used
monthly.land_and_ocean.90S.90N.df_1901-2000mean.dat
not the data dataset I mentioned.
Re: #78 (William Astley)
I’m highly skeptical of this claim. One of the most common mistakes made by scientists in data analysis is to attribute periodicity to time series when the data don’t really support that conclusion. Considering that we have a mere 400 years of sunspot data to work with, the evidence for a genuine 200-year periodicity is flimsy — at best. And considering Svensmark’s well-founded contention that changes in solar-cycle intensity do *not* correspond to changes in climate-relevant solar activity, claims that reduced solar activity will lead to cooling, or even that “We should have an opportunity to determine how much of the 20th century warming was attributable to solar as compared GWG, if the solar minimum occurs starting cycle 24,” are premature — at best.
GREAT fun video on global warming
http://www.youtube.com/watch?v=5SiEm2akhrc
http://www.globalwarmingguy.com
I have to confess that I find this paper opaque.
Can someone tell me if have they divided the Moberg temperature change 1700-1900 (~0.3C) by the Wang TSI increment for that period (~.5 W/m^2) to get (0.65 +/-0.28 K m^2/W).
I.E are the sensitivities rated against Insolation in space?
I am not sure of the exact relation but to get to a standard forcing from TSI you have to divide by 4 for the spherical geometry of the rotating earth, multiple by ~0.9 (ish) for UV absoprtion above the tropospere multiple by ~0.7 to allow for albedo.
Do that and 0.65 becomes ~4.1 K/(W/m^2).
Perhaps I am having one of my bad days but it really looks like they are quoting K/TSI which need converting by a factor of about 6 to get the corresponding sensitivity.
Best Wishes
Alexander Harvey
Small correction: they use the their wierd estimator which for Moberg gives 2*.186 = 0.372K but it does not change my point.
In reply to Tamino’s comment:
“I’m highly skeptical of this claim. One of the most common mistakes made by scientists in data analysis is to attribute periodicity to time series when the data don’t really support that conclusion. Considering that we have a mere 400 years of sunspot data to work with, the evidence for a genuine 200-year periodicity is flimsy — at best.”
The following is 1200 year evidence of a 200 year solar cycle.
http://www.springerlink.com/index/V544315804280142.pdf
200-year variations in cosmic rays modulated by solar activity and their climatic response
Manifestation of the 200-year solar cycle (de Vries cycle) in climatic changes (summer temperatures) has been investigated by analyzing the radial growth of long-lived (800–1200 yr) ….Quasi-two-hundred-year variations in the radial growth of trees have been revealed, which correlate well (correlation coefficient reaches 0.94) with similar solar activity variations (Δ14C).
http://linkinghub.elsevier.com/retrieve/pii/S1364682698001424
In reply to Tamino’s other comment concerning Svensmark. Svensmark’s papers and his book state that there would be a significant cooling resulting from a solar minimum.
There are three methods in which solar changes affect climate. Electroscavenging that removes cloud forming ions. Electroscavenging is caused by high speed solar wind bursts. Changes in the solar heliosphere. The heliosphere takes roughly two years to reach equilibrium after a step change. Changes in the TSI.
In reply to Ray Lambury,
There is a disagreement as to how much of the 20th century warming was due to solar modulation of clouds and TSI changes and how much was due to GWG.
A set change in solar modulation of clouds and TSI will enable that question to be resolved.
Re: #95 (William Astley)
I have studied in great detail the variations of cosmogenic isotopes, and a large number of research papers which claim to establish numerous periodicities using them as a proxy for solar variations. It is precisely because of this detailed study that I am skeptical of the validity of claims of periodic fluctuations. As I said before, one of the most common mistakes made by scientists in data analysis is to attribute periodicity to time series when the data don’t really support that conclusion. You have simply pointed to examples of this.
I remain highly skeptical that solar minima occur every 200 years.
Svensmark will be presenting his evidence that climate-relevant solar variations to not follow variations in sunspot cycle intensity in about a week at the AGU meeting.
Re: #96 (me)
Oops! It’s not Svensmark — it’s Svalgaard.
The S&W paper states,in part, on P.4:”[23] The second independent constraint reflects the
hypothesis that the secular TSI increase during the preindustrial
era is responsible for the contemporary observed
increase of global surface temperature. (In the Conclusion we discuss the limitation of this assumption.)”
Then in the conclusion are the statements:” On the other hand, if a secular temperature
showing large preindustrial variability is adopted, such as
MOBERG05, the climate is found to be very sensitive to
solar changes and a significant fraction of the global
warming that occurred during last century should be solar induced.”
And further on:”Some climate model studies [Shindell et al., 2003] have
reported that on a secular scale the volcano forcing had the
same order of magnitude as solar forcing, other studies
would present a wide range of relative contributions.
[40] Therefore our estimates about the solar effect on
climate might be overestimated and should be considered as an upper limit.”
All of this sounds to me like quite a stretch!I’m referring to their hypothesis that the TSI activity during the pre-industrial period, some 250 years ago and beyond, has a non neglible effect on the global climate change being seen today! Can this be?!
[Response: Not to defend S&W, which is really quite full of nonsense, but I think you are misconstruing their argument in this instance. I believe they are making a statement about estimating climate sensitivity to solar forcing by using the pre-industrial fluctuations; they are not arguing for a direct lagged effect of solar forcing 250 years ago. If a climate reconstruction like Moberg’s, with a lot of variability, were right, you’d need a high sensitivity to solar forcing in order to account for it. Then, take that high sensitivity into the post-industrial era, and you get a lot of solar response then, part of which correlates with the observed temperature. What’s left over is what you explain by CO2. (in the twisted physics-free world Scafetta and West inhabit). Now, in a physics-full world, the problem you have with that argument is that if the climate is so terribly sensitive to radiative forcing by the weak solar variability, you ought to get a truly humongous response to CO2– which wouldn’t match the observed temperature record. In the physics-lite world of Scafetta and West, this is gotten around by assuming the sensitivity to radiative forcing by CO2 is a parameter that can be twiddled independently from sensitivity to solar forcing. What they probably have in mind is some variant of the cosmic ray modulation of clouds. Fine, if that’s what they want, but this has got to be considered rank speculation until there’s some quantified treatment of the radiative forcing by the purported cosmic ray effect. And if they are invoking some kind of stabilizing cloud or water vapor feedback to damp down the CO2 sensitivity, they’ve got to consistently apply that damping to any radiative forcing coming from the solar-related modulation of clouds as well. –raypierre]
BTW Moe Berg( who I’m sure has nothing to do with the naming of the model), a major league catcher for ~15 years, and then a spy during WW2,is also known for his statement saying that a catcher’s equipment are “the tools of ignorance”. Well, tools are neither intelligent nor ignorant, but in the hands of the untrained or the mischievous, they can be useless or even detrimental. This may well apply to the S&W paper.
I agree with Tamino (#96). While solar activity definitely fluctuates, there is little compelling evidence of true periodicity. The direct records are too short to establish long-term periodicity, and the proxy records of solar variability (e.g. C-14, Be-10) look like red noise. In other words, you’d expect a similar pattern if the intensity simply fluctuated up and down in a random walk. Sometimes, merely by chance, there would be intervals of apparent periodicity, but those intervals generally don’t persist over the long-term.
That said, I would still suspect that solar intensity would likely decline during this century, if only because the current intensity appears unusually high by historical standards.
Those looking for a bit of fun might want to read the recent CA post on S+W 2007, beginning with Svalgaard’s first comment at about #65. The writhings of the solarphiles are a sight to behold. McIntyre doesn’t sound too happy himself, which I suppose is understandable given that so much of his support base is composed of people who *know* that it just has to be the sun. Of course if Svalgaard is correct (and BTW he seems to have a lot of support from other solar physicists), there may be some unsalubrious implications for McIntyre’s own efforts to plump up the MWP and LIA.