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.
Think you missed the links to GCR (here, here, here)
[Response: Thanks! Fixed now. -rasmus]
Hmmm, this contribution could do with a little polish.
– The article critiqued isn’t actually quoted (a problem for those not having online access to this AGU journal)
– Spell checking! (What is ‘buildt’?)
– The language is not good (‘How could they ignored [sic] that?’; ‘I’d flunked’; similarly in many places) and a bit rambling
– The claim ‘The paper also offers some incorrect references’ is unintentionally funny as it is followed by an incorrectly written author name, and no actual reference in sight ;-)
[Response: Link added now. -rasmus]
– GCR = Galactic Cosmic Rays. Who knew?
I don’t doubt the validity, but presentation is important. While this is not a peer reviewed journal, what about showing it to a colleague with a red pencil first?
[Response: Point taken, sorry about that! I was a bit too quick, but it’s good to get some feedback. I have fixed the typo and a few of linguistic details. My old English teacher would probably have given me a ‘D’ for this ;-) -rasmus]
The study Rasmus Benestad tries to evaluate is
Scafetta, Nicola, and Bruce J. West, 2007. Phenomenological reconstructions of the solar signature in the Northern Hemisphere surface temperature records since 1600. J. Geophys. Res. – Atm., 112, D24S03, doi:10.1029/2007JD008437, November 3, 2007, and available online http://www.fel.duke.edu/~scafetta/pdf/2007JD008437.pdf
Earlier studies by the authors are e.g.
Scafetta, Nicola and Bruce J. West, 2003. Solar flare intermittency and the Earth’s temperature anomalies. Physical Review Letters 90, 248701, June 20, 2003, online http://www.fel.duke.edu/~scafetta/pdf/PRL48701.pdf
Scafetta, Nicola, and Bruce J. West, 2005. Estimated solar contribution to the global surface warming using the ACRIM TSI satellite composite. Geophys. Res. Lett., 32, L18713, doi:10.1029/2005GL023849, September 28, 2005, online http://www.fel.duke.edu/~scafetta/pdf/2005GL023849.pdf
Scafetta, Nicola, and Bruce J. West, 2006. Phenomenological solar contribution to the 1900–2000 global surface warming. Geophys. Res. Lett., 33, L05708, doi:10.1029/2005GL025539, March 9, 2006, online http://www.fel.duke.edu/~scafetta/pdf/2005GL025539.pdf
Scafetta, Nicola, and Bruce J. West, 2006. Phenomenological solar signature in 400 years of reconstructed Northern Hemisphere temperature record. Geophys. Res. Lett., 33, L17718, doi:10.1029/2006GL027142, September 15, 2006, online http://www.fel.duke.edu/~scafetta/pdf/2006GL027142.pdf
Enjoy reading!
A [pdf] of the full text we’re discussing here :
http://www.acrim.com/Reference%20Files/Scafetta%20&%20West_2007JD008437.pdf
Work of this nature is important but it needs to be reasonable.
I also will not be reading this paper (no free access) so I am reluctant to comment but even the diagrams shown here raise some problems.
One can get some idea of the model being invoked from the implied amplitude and phase delays.
We have two diagrams (their figure 4) both of which appear to correspond to a simple lumped (thermal)capacity/conductivity system. I note that there is a starting transient (both the input and response are 0 at time 0, and the phase angle and vertical displacement changes with successive cycles).
Is the reason for the transient explained in the text? (genuine question not rhetorical).
Such a model has some consequences in that it is a simple low pass filter which would severely attenuate higher frequencies and give them a phase lag of approaching pi/2.
Now there is some support for this at diurnal and annual timescales over the oceans but less so for the continents.
Do they give any figure for the time constant or constants they feel explain their effect?
Too long and the seasons will disappear, too short and the solar cycle will not be attenuated in the temperature record.
The lumped capacity/conductivity model is but one of several available that might apply to the earth or most importantly the oceans.
At the ocean surface (well mixed layer) a lumped model may be appropriate, below that a diffusion model (which tends to give a pi/4 phase delay) is believed to be appropriate, and for the deep ocean flows, a more complex transmission line that incorporates the effects of momentum would seem appropriate.
If we are looking for heat to be returned at a later date in some sort of coherent way only systems that incorporate flow would seem to be likely candidates. Both the lumped and diffusive models smear out the signal (a wiggle in the past will not reproduce that wiggle in the future). Is this what they claim?
The thermal response of the earth (primarily the oceans) holds an important key to understanding the entire system. It is at least an equal third of the (forcing, long term sensitivity, thermal response) system. It is also the least loved and perhaps the least sexy of the three.
Analysing the thermal response to accurately known cyclic forcings will give insights into how the oceans behave thermally at various timescales.
More needs to be done, for instance, what is the amplitude of the 11-ish year solar cycle in the record. Some say it is too attenuated to be found, some say it is big (rather too big perhaps). Which is correct?
If we do not know the thermal response of the earth well enough to know the size of the solar cycle response how close are we to knowing the relationship between observable (short term) climate sensitivity and the long run sensitivity. Getting the answer to this question wrong has large implications 50 or 100 years out.
As I understand it, the observable (short term) climate sensitivity is a bit too low to be reasonable and hence much of the thermal excess must be being stored in the oceans. By a bit two low I mean that simple analysis of the 20th century response against long term (CO2) forcings gives a low value to the sensitivity. It is believed that the difference will show up the record in centuries or millennium to come.
Now it is important to be able to put some limits on the nature of this returned flux. If the paper is saying that stored energy (excess/deficit) is being returned. This must be true but without any knowledge of the timescales and coherence of the returned signal I can not see that it is possible to make any meaningful judgement on such an issue.
Best Wishes
Alexander Harvey
Timo,
Thank you for the link, so I will be able to read it after all.
(Postings crossed)
#4: Thanks Charles.
The good news is that the language in the article isn’t so much better… and it went through peer review ;-)
Now that I am reading the paper some notes.
Camp & Tung found a 0.18 (+/1.08) K solar cycle signal in the (1959-2004) record. This is the one that I felt seems a little too big. It is not I think quoted by the authors but it is quite recent (May 2007).
Both 0.1 (+/- .01) K (from this paper) and the above figure can not be correct. The uncertainty in this figure between authors is massive but the values are often precise. One needs ot be cautions.
Some additional problems of the Scafetta and West (SW) paper:
SW are proud of the good match of their solar reconstruction and global temperature on the multidecadal time-scale (SW Figure 5). However, this match is without any time lag and thus is strong evidence against a slow system response. If the increase of global temperature since 1970 should be a lagged reaction on the increase of solar activity before 1950 (time lag of maybe about 50 years), such lagged reaction should be detectable for multidecadal variability since 1600, but there isn’t any at all.
Besides, SW recycle a bunch of tiring old sceptic arguments. They argue e.g. that the CO2 increase during industrialisation might be partly due to a temperature increase. 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).
SW completely ignore the third available TSI composite by Dewitte et al. (2005; IRMB), which shows no significant TSI trend in the satellite period. They also ignore that the positive trend of the 11y-cycle minima in the ACRIM data (which they used for their estimations in a previous paper) has almost vanished when including the current minimum (the trend is 10 times weaker now; see http://www.acrim.com/ACRIM%20Composite%20Graphics.htm).
I think I am getting a feeling of deja vu here.
Did we not have another paper trying to extract the time constants and deduce sensitivity a little while back. I think it used autocorrelation.
Unfortunately the world is a bit more complex than that.
When the lump models run out to timescales longer than their time constant other mechanisms must be considered to take over. I really wish that the lumped capacity/conductivity model was put in a box marked “dangerous”.
My quick look at their “time constant”/sensitivity values tells me to consider that the top ~100m of the ocean is well mixed. Which is often regarded to be the case. So this could be a mechanism.
The question is “is that all there is to it?”.
Well no, below the well mixed layer diffusion takes over with much longer time constants. Also the deep circulation must be considered with timeconstants of the order of centuries to millenia. Even the mixing of the ocean surface is a complex affair and the depth of the layer is seasonal and dependent on latitude and is unlikely to behave with a single time constant.
Best Wishes
Alexander Harvey
Sounds like they followed the time-honored tendency of grad students to start from the answer in the back of the book and work backwards until they got it. It appears, however, that their book had the wrong answers in it.
My questions: Where has all that energy been hanging out for the past 60 years? How do they manage to get a “timed release” of the energy so that it kicks in just in time for the millennium celebration? And most important: Why work so hard to produce such crappy science (e.g. poor reconstructions, no physical understanding…) when we have a model that is physics-based and actually works quite well?
Can anyone follow the production of T(MANN03) etc.
Rearranging gives:
((T18-T17)+(T19-T17))/2 = ((T18-T17)+((T19-T18)+(T18-T17)))/2
= ((T19-T18)+ 2*(T18-T17))/2
= (T19 + T18)/2 – T17
which is the average of (average 19thC + average of 18thC) – the average of 17thC (temperatures)
Far too many averages for my liking also the distance from the temporal average of the 17thC to the temporal average of the temporal averages of the 18thC and 19thC is 150 years not 100 years.
I.E. if they must do this should there not be a 3 not a 2 in the denominator?
Try it with a 1K/Century linear slope from 1610-1910.
Apply their formula and you get 1.5K/Century:
(1-0)/2 = 0.5 (T17)
(2-1)/2 = 1.5 (T18)
(3-2)/2 = 2.5 (T19)
((1.5-0.5)+(2.5-0.5))/2 = 3/2 = 1.5
If this is really is the case I have to ask when papers get reviewed does anyone check the equations?
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
The reason is one that realclimate keeps pushing on the CO2/temperature correlation problem.
1940-1970 the correlation between CO2 and temperature is not positively correlated, and yet realclimate doesn’t view this as a problem.
However, if an alternative explanation has the same issue, then its a major flaw.
Is is it that rasmus in his original post things that pollution causing the temperatures to drop 1940-1970 isn’t a good explanation? If so, if he would let me know, I’d like to have a realclimate statement that there’s a major flaw in AGW.
Nick
[Response: Arrggh! The whole point of the ‘mainstream’ view is that you are not going to get very far with simple one-factor correlations. It doesn’t work for solar, and it doesn’t work for CO2 either – too many of the forcings are correlated. You absolutely need to use all major forcings before you can do an attribution. When you do that, GHGs are very likely responsible for the rise in recent decades. – gavin]
PMOD link is broken. I assume it should point here (www.pmodwrc.ch/pmod.php?topic=tsi/composite/SolarConstant) rather
Dear Alexander, it’s good when you direct attention to the oceans.
Please see:
Wunsch, Carl, 2007. The Past and Future Ocean Circulation From a Contemporary Perspective. Chapter in Schmittner, Andreas, John Chiang, Sidney Hemmings, Editors, 2007. Ocean Circulation: Mechanisms and Impacts. AGU Geophysical Monograph Series Vol. 173, 2007, online http://ocean.mit.edu/~cwunsch/papersonline/present_pastocean_rev_2april.pdf
Abstract
Meridional overturning of the ocean, particularly the North Atlantic, is commonly invoked as the “trigger” and major cause of global climate change in a series of stories based upon a very simplified view of the circulation (a “conveyor belt”). Observational and computational progress in physical oceanography, however, over the last 30 years has rendered obsolete the old idea that the fluid ocean is a slowly changing, passive, almost geological system. Instead, it is a dynamically active, essentially turbulent fluid, in which large-scale tracer patterns arise from active turbulence and do not necessarily imply domination of the physics and climate system by large-scale flow fields. To the contrary, oceanic kinetic energy is dominated by the time and space-varying components. The complexity of the resulting fluid pathways is an essential part of any zero-order description of the system. Thus general circulation models are the essential tool for understanding past, present and future climate states. Quantification of the likely major errors in using oversimplified models with inadequate turbulence closures and undersampled data becomes the main issue. Determining the past and future circulations is not easy, but hiding the difficulties is not a viable option.
….
Well, as far as I can see, before we are able to correctly model the oceans we are unable to forecast (almost) anything.
Actually, honest modelers have already admitted that 30, 50 or 100 yr forecasts/projections are too uncertain and have no practical value.
Please see e.g.
Cox, Peter M., and David B. Stephenson, 2007. A Changing Climate for Prediction. Science Perspective Vol. 317, No 5835, pp. 207-208, July 13, 2007
Stainforth, David A., M.R. Allen, E.R. Tredger, and L.A. Smith, 2007. Confidence, uncertainty and decision-support relevance in climate predictions. Philosophical Transactions of the Royal Society A Vol. 365, No 1857, pp. 2145-2161, August 15, 2007
Collins, Matthew, 2007. Ensembles and probabilities: a new era in the prediction of climate change. Philosophical Transactions of the Royal Society A Vol. 365, No 1857, pp. 1957-1970, August 15, 2007, online http://www.journals.royalsoc.ac.uk/content/u0106636v6g14764/fulltext.pdf>
Extract:
“…Model imperfections, coupled with fundamental limitations on the initial-value prediction of chaotic weather and the unknown path that society may take in terms of future emissions of greenhouse gases, imply that it is not possible to be certain about future climate…”
Even the IPCC admits:
”the future is inherently uncertain” (IPCC AR4 2007 WGIII SPM, last sentence)
….
Well, when we discuss about solar influence, which has been flat for the last two or so decades, I’m pondering inertia in the oceans. I recall seeing an estimation of 10 years lag time in the mixed layer. Any confirmation?
If correct, we may have one possible explanation (among others) to current non-warming of surface and oceans, despite CO2 increase (?).
Another explanation we have in the study
Smith, Doug M., Stephen Cusack, Andrew W. Colman, Chris K. Folland, Glen R. Harris, and James M. Murphy, 2007. Improved Surface Temperature Prediction for the Coming Decade from a Global Climate Model. Science Vol. 317, No 5839, pp. 796-799, August 10, 2007, online http://www.precaution.org/lib/warmer_after_2009.070810.pdf
[Response: Lack of absolute certainty is not the same as no knowledge. All scientific knowledge is preliminary and not absolutely certain, so by your implication, we know nothing useful about anything. I find it odd that you only apply this heuristic to climate change. – gavin]
Check out http://www.co2ticker.com to see co2 emissions BY THE SECOND and compare different countries co2 emissions .
rasmus, the point on the “upper limit” had to do with the study being sun-centric. In other words, S&W don’t put much emphasis of volcanoes, pre-industrial anthropogenic, and possible other natural causes for pre-industruial climate variability. Not much to my liking, but that’s life. I did not like your point on S&W comments about the sun-CO2 feedback relationship. It should be clear the sun isn’t doing anything to CO2, the temperature change (generally centered in orbital variations) is. Simple gas proportionality inversely related to temperature and we reproduce a feedback. Of course, the sun isn’t digging up buried CO2. S&W specifically note atmosphere-ocean gas exchange. However, S&W is also trying to get more CO2 feedback than is possible. S&W should go over the CO2-temperature response at http://www.springerlink.com/content/9q2hwxrhr3cm8g87/?p=6ee1c184f37d4955a354d64157c3a084&pi=11 (and since solar is a minimal impact next to GHG, and we’re not yet even at 1 C, you can’t get the feedback being discussed- not to mention what we know about the Suess Effect and known fossil fuel emissions)
Secondly, if we accept figure 5b from S&W, I have a hard time accepting the “thermal lag” argument. We run into the same problem repeated here often- if the lag was so huge, we expect the rate of warming to drop over time as the ocean adjusts to the level of forcing, but instead we are seeing the opposite. Perhaps a lag over years to decades, but 50 years and still no signal of the decline? And then we reproduce a graph with direct correlation with no lag?
A few other things
– Mann et al. does not “get rid” of a MWP and LIA
– “weaker TSI forcing would imply the presence of a stronger climatic feedback to TSI variation and/or a stronger climate sensitivity to other solar changes” – What about non-solar changes? True, a larger change from unmodified causes means a more-sensitive climate system but here there is no reason to necessitate unmodified causes. The logic could also apply to GHG’s.
– Your points still remain: stratosphere cooling? PMOD? ERBS/ERBE, GCR, the aa-index, 10.7cm flux, solar cycle length, sunspot number, etc showing no trend…Silliness
Re: Ray Ladbury “Why work so hard to produce such crappy science?”
Odds are they’re being rewarded for their tireless contributions somehow, along with the editors of the crappy journals… [edit]
[Response: But JGR-A is not, in general, a crappy journal. Where there is some controversy, editors often like to lean over backward to let things into print so they can be discussed out in the open. This flaws in this paper should have been caught in review, though. Taken together with other deeply flawed papers that S&W have been able to publish in AGU journals, it does seem to me that a pattern is emerging which suggests some breakdown of the review process at AGU. [edit] –raypierre]
I’m a rank amateur where the study of science is concerned, so RealClimate continually amazes me with the sheer flim-flammery of some people who call themselves scientists, and some journals which call themselves scientific. Silly me, I used to think “peer-reviewed” meant something.
Are there any conventions regarding financial disclosure for scientific journals? Just wondering. Enhanced transparency could restore the reputation and vitality of scientific publishing. Such standards could take the form of voluntary protocols, certified by an independent organization as is “Fair Trade” coffee. Maybe that’s just a con game as well, but at least I (the coffee purchaser) can distinguish between coffee vendors who at least care about seeming to care, and those who clearly don’t.
With respect, I have read many excellent articles on this site followed by interesting discussions.
The content of this article is interesting, however the presentation is so poor—well it’s hard to believe we are reading it a realclimate.org
The article needs a rewrite from top to bottom.
[Response: I’m sorry about this. I have re-read the post, and made slight improvements (removed ‘and’s and hopefully improved the grammar). But that aside, I think the points are clear. Is it ‘contaminated’ by my Norwegian, do you think? -rasmus]
Rasmus or someone else here, can you give examples of papers that discuss the impact of solar variation over the last 400 years that you do like?
I couldn’t find other way to address this blog’s contributors so I will try here.
What do you think about the recent Oxfam study, which states that the major climate disasters have multiplied by four due to the global warming? Does it have any credibility? Is it serious? Is it a gross overstatement of something that is happening? What do you believe on that matter?
Sorry for my english, and thank you for your time
:)
Timo, you are once again falling victim to the fallacy that because we don’t understand everything, we understand nothing. Some results remain robust over the entire possible range of likely changes in ocean circulation. What is more, those arguing for complacency fail to understand that most of the risk uncertainty is on the upside. By all means, we need to keep studying the problem, but we need to be working on mitigation in parallel with those efforts. Not to do so when dealing with a physical system with large and ill constrained positive feedbacks is negligent to the degree of criminality.
Charlie, re: 19. I think you are being entirely too harsh. There are gramatical errors and organization could be improved, but the points Rasmus makes, he makes quite clearly. Sometimes it’s kind of fun to go along with the experts as they annotate their reaction to an article in quasi-real time.
Some first comments.
Rasmus : 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.
Could aerosol direct and indirect effects explain that ? (The diminution of ongoing SW counterbalancing the delayed effect of 1900-40 warming)
[Response: Yes, it think so,. But if the relaxation time is long and the solar forcing the dominant driver, no.. -rasmus]
*
Rasmus : 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 ignored that?
First, stratospheric T 100-50 hPa has a global cooling trend for past 50 years (see Sterin thereafter for example), but how could we explain that if TSI has no change at all, particularly since 1980 (PMOD composite) ? The usual anwsers are : O3 depletion and CO2 forcing. But in this case, is the stratospheric trend of any help to infer a solar UV or TSI trend, if O3 and CO2 are the main drivers ?
http://cdiac.ornl.gov/trends/temp/sterin/steringrap.html
[Response: One proposed mechanism for how the solar signal may be amplified is that solar UV alters the density/temperatures in the stratosphere, which subsequently affect planetary wave propagation. This may have an effect of the redistribution of heat, and thus lead to a warming response near the surface. One would expect a warming of the stratosphere with increased solar activity levels (increased absorption of UV). But if ozone-depletion takes place, this will counter this mechanism, and since the stratosphere has cooled, seems to be the strongest effect (well increased GHGs also play a role).-rasmus]
Second, we should precise which level of stratosphere and which latitude are concerned. I read for example in ML Chanin 2006 or Labitzke 2006 that stratospheric response to solar maxima minus minima is not a univocal warming trend. See special issue of Space Science Reviews, recently published by Springer in Space Science Series ISSI 2007 :
http://www.ingentaconnect.com/content/klu/spac/2006/00000125/f0040001
[Response: I think this depends where you are looking. -rasmus]
*
#9 Urs In the figure 5, the 1900-2000 period is the sole to exhibit a constant rising trend for TSI proxies. So, in previous periods, the long term response could be cancelled by short term variations (at least theoretically). Anyway, I fastly read S&W paper but I don’t find the 50 yrs time lag you mention. Could you precise ?
*
More generally, all TSI reconstructions (see Lockwood et Frohlich 2007, Lean et Wang 2005, Solanki et Krivova 2006, Beer, Vonmoos et Muscheler 2006, etc.) agree on one point : the Sun is more active on 1960-2000 than in 1900-1940. And more active for 1900-2000 that for past two centuries, at least if TSI reconstruction from magnetic proxies (open flux) are correct.
The fact that there’s no trend for 1980-present (or a small decrease) should not dismiss this evidence : the 20th Century global warming seems to correlate with a global brightening of our star. Astrophysician and others work on the physical explanation and evaluation of this correlation (UV-ozone and stato-tropo circulation, with QBO and BDC, effect on GCR and nebulosity, etc.). That’s the normal job for science, the same is done for CO2 effects on climate.
[Response: Actually,. there is little trend from the end of the 1950s. -rasmus]
Re #s 19/23: I agree with Ray. As long as the points are made clearly (which they were in this case), perfect English grammar isn’t a necessity. We want to encourage non-native speakers of English, and unfortunate remarks like Charlie’s have the opposite effect.
[Response: Having said that, we should have done a grammar check before posting. – gavin]
[Response: Arrggh! The whole point of the ‘mainstream’ view is that you are not going to get very far with simple one-factor correlations. It doesn’t work for solar, and it doesn’t work for CO2 either – too many of the forcings are correlated. You absolutely need to use all major forcings before you can do an attribution. When you do that, GHGs are very likely responsible for the rise in recent decades. – gavin]
Quite right. However, rasmus uses this argument to say that S&W are wrong.
I’ll post the sentence again
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.
[Response: I think we all agree and it’s not really unclear to me… As Gavin says, there are several forcings. But if you play along with S&W that (i) the relaxation time is long and (ii) that the solar forcing is the dominant forcing, then it’s hard to explain. S&W do not discuss this or why different forcings should have different relaxation times. -rasmus]
Let me put this in CO2 terms.
But it is unclear why the temperature decreased during the 1940-1970 period at a time of rising CO2.
This is identical logic used by rasmus to say that S&W are wrong. If you apply the same standard and level of scientific thought, you come to the conclusion that AGW is wrong.
One could argue that something else also happened then
Exactly. The arguments that you apply to the correlation being negative in this period, also apply to the question of solar.
Put it this way.
What evidence do you have that your claim of polution 1940-1940 does not apply to S&W solar explainations?
None.
That’s why the original article by rasmus is deeply deeply flawed.
[Response: Don’t agree, because you misunderstood my point. This merely shows that solar forcing is not the main driver (as S&W presume) and the additional variations suggest a shorter relaxation time than S&W suggest, as they imply that a long relaxation time is means that the present warming is part of a recovery from increased solar activity in the past. -rasmus]
Nick
[Response: Rasmus can defend himself, but S&W have started with the assumption that solar is the only important driver, therefore the criticism made is justified. Rasmus is not doing the opposite (i.e. assuming that CO2 is the only driver) therefore your equivalency is in error. – gavin]
I’ve quoted directly from rasmus’s post and he taken the view that you can use a one-factor model for solar.
To then come back and say that he isn’t because he isn’t assuming that CO2 is the only driver is distorting what I’ve said.
I’ll spell it out again to make it clear.
Rasmus says in the article that 1940-1970 there is not a good fit of temperature with solar, contradicting the model which predicts a rise.
The implication here is that because the model (single factor) does not fit then the premise of a large solar component is falsified.
The problem is back on the single factor model which doesn’t work for CO2 either. You, as you rightly point out, need more factors.
It is at this point that the article goes wrong. As you Gavin well know, the single factor CO2 model doesn’t work 1940-1970 because of the factor of polution.
Introduce that and there is clear explaination of why 1940-1970 shows a temperature drop in spite of a solar increase.
What rasmus is arguing is that you can use pollution for a CO2 model, but you can’t use it for a solar model.
[Response: Actually, I’m saying you can’t have a long relaxation time and a dominant solar driver. The clue to S&W’s argument is that precisely this combination is used to explain the recent global warming. I also say that the climate responds to many forcings (GHGs, aerosols, volcanoes, solar, etc), but there are also internal variations. -rasmus]
He should have said that the 1940-1970 drop is expected from a solar model, for the same reason as there is a drop 1940-1970 from a CO2 model.
Nick
[Response: We don’t appear to be communicating. S&W assume a one factor solar model. Rasmus points out (correctly) that this fails a number of tests. No one is assuming a one factor CO2 model. There is only one correct model which is to take all forcings together. Criticising S&W for not doing so is perfectly fair game. – gavin]
Charles, You seem to be saying, “Let’s forget the last 20 years. Then we can just assume it’s all due to the Sun.” I don’t think that’s going to work. The fact of the matter is that you can’t consider factors in isolation, and if you don’t include the added warming due to greenhouse gasses, you don’t match the trends. What we have is a situation where the sun gets warmer and the climate gets warmer. Then the Sun cools and the climate still gets warmer. Hmm. That ought to tell you something.
Gavin – I can not find anything in the paper suggesting that S&W assume solar to be “the only important driver”. And even if they were – how does that contradict the point nick made? Even with solar being the most important driver, the standard explanations for cooling in the mid 20th would still apply, wouldn’t they?
[Response: The assumption is built in to their ‘model’. If they wanted to include other factors – aerosols, GHGs etc. they could have done so. The ‘real’ explanation is a combination of aerosol forcing, combined with some internal variability – neither of these factors are accounted for here. – gavin]
Nick,
Further to Gavin’s point, Rasmus has only demonstrated that there is an serious inconsistency in S&W’s premise that variation in solar activity is the lone forcing of climate change. Namely, it requires near uniform response times, which is manifestly at odds with even their, (questionable), data. See post #9 for more on this. It is a perfectly valid point and totally inapplicable to the mainstream understanding of the system, which, as indicated by Gavin, is nothing if not multi-causal. I sense there is a question underlying this accusation, which IMOHO, would probably be a better approach.
But as I understand it, the whole point of their model is a (unique?) approach to quantify solar influence on climate variability based on different proxy studies – they don’t try to explain the recent decadal temperatures in detail. They’re talking at some considerable length about anthropogenic influences in the text and state, that solar merely contributes to recent warming. (And if you pick MBH rather than Moberg, that contribution is rather small).
[Response: That might be what they are trying to do. But it is flawed because other factors correlate with solar over these timescales and the role of unforced noise is not quantified. Unique is not the problem. -gavin]
Okay, so the big issue here is the importance of just focusing on the “solar issue”
From a non-expert view, can you come up with at least a ball park ratio of forcing?
If solar output=1
Then aerosols= 0.2?
And CO2=0.4?
Any way to put a value on what is most important?
[Response: It depends on what period you are talking about. For the twentieth century, normalising to solar=1, you would get CO2=8 (that is eight times solar, not 0.8), other GHGs=5, aerosols=-4 etc. In the pre-industrial period, solar=volcanic=1 (roughly). – gavin]
Re # 18 Daniel C. Goodwin “RealClimate continually amazes me with the sheer flim-flammery of some people who call themselves scientists, and some journals which call themselves scientific. Silly me, I used to think “peer-reviewed” meant something.”
Are you referring to the RC contributors (none of whom, to the best of my knowledge, receive funding from the power industry, nor consult for the power industry), or the authors of papers critiqued by the RC contributors? Please clarify!
As for peer review, it means only that reasonably qualified scientists examined the manuscript and recommended changes to improve the paper, or recommended that the paper be rejected; the journal editor has to make a determination about the merits of the paper based largely, but not entirely on the reviewers’ comments (the editor has some discretion in deciding to accept or reject – his/her reputation as an editor, and the reputation of the journal, depend on sound editorial judgments).
The quality of peer review varies with the individual reviewers, some of whom put tremendous effort into a review (possibly even checking the math in equations, checking computer code, etc), whereas others may not put much effort at all into their review (I’ve certainly had reviews of my papers that indicated to me that the person didn’t carefully read, or simply didn’t understand, my manuscript). This is why, as others on this site have repeatedly warned, you can’t put too much stock into any single paper – it needs to be viewed in the context of the wider body of literature on the subject and the work currently in progress (this is why scientists go to conferences to hear about research being conducted). Scientists doing research and publishing in a given field will have more, or less, confidence in the findings in a new paper depending on their particular knowledge and experience. Publication in a peer reviewed journal is just the starting point for research to make an impact on the scientific community – it is not the final word.
As for your question, “Are there any conventions regarding financial disclosure for scientific journals?” – it depends. Here are the ethical guidelines for AGU journals:
http://www.agu.org/pubs/pubs_guidelines.html
I see no mention of financial conflict of interest disclosure (though, most funding agencies require acknowledgment of funding source in any publication). However, I am not surprised – this has only recently become an issue in the medical literature, because of revelations of bias associated with corporate (e.g, drug companies) support of clinical research. Certainly, if a climate scientist is supported by an oil company or other source that could be considered to have a stake in the research findings, this should be disclosed in the acknowledgments section of the paper. Is this always done? I don’t know.
[Response: To, blogs (like RC) may play an important role, as papers get discussed. Poor papers will be torn apart, and when authors know that they risk their paper being scrutinized and criticized, they will hopefully take more care to check their analysis. -rasmus]
I think some of the comments are misconstruing the work of S&W.
Yes, the only forcing in their model is solar variability. But their purpose is not to say that the sun explains all behavior, but rather to characterize how much variation might be explained by solar forcing.
For example, from page 7:
Using the preindustrial period to calibrate the impact of solar forcing is quite reasonable, given the high apparent correlations between solar variation parameters and temperature reconstructions such as Moberg’s. Finding that some fraction (e.g. 8-25%) of the warming post-1950 might be explained as a residual solar effect, isn’t even entirely unexpected and doesn’t appear to challenge the consensus that most of the post-1950 warming is anthropogenic.
Some of the criticisms being made here are legitimate (e.g. ACRIM/PMOD), but a number of comments seem to spuriously assume that they were attempting to explain all of 20th century warming. Their model certainly doesn’t explain all of the features of the temperature record, but since it was never their claim to have done so, such criticisms seem misplaced.
S&W still believe that GHG are major climate forcing and that anthropogenic effects are responsible for most of the recent (post-1950) warming.
[Response: The series of S&W papers have many assumptions that always increase the attribution to solar. I doubt that I am alone in perceiving a desire to make the number as big as possible. It is not that the answer is zero, but the likely answer (roughly 10%-20% of 20th Century warming, more like 0% for post 1980) never appears to be bracketed by their error bars. Aren’t you curious why not? – gavin]
Joao Vasco (29) — Your English is quite good, but I fear that ‘major climate disasters’ is subject to misinterpretation. To me, the spread of the Sahara Desert south into the Sahel might be called a major climate disaster, as are the devastations of the world’s tropical rain forests. These are caused by humans, although climate change may also play a role in the expansion of the Sahara Desert.
If you are referring instead to extreme weather events, then yes, global warming is thought to make such more likely. I don’t know about the factor of four, which seems too high to me.
I’m not sure I have answered your questions (and anyway, I am an amateur here). If not, please rephrase and I (or someone) will try again.
#28 Hank, I don’t forget at all the past 20 years and it would be very surprising that solar forcing explains all the modern GW. In fact, I’m not much interested by “correlation game” ad attribution-detection with ad hoc parametrization, neither for S&W here nor for AR4 models. Ingram 2006 shows interestingly in his paper that 11 years smoothing of T and Fs give a very good correlation (but very bad for CO2) and inversely for a 8 yrs smoothing. More broadly, many signals of XXth century climatologies are degenerated (the better illustration of that : 23 models perfectly match the T curve 1900-2000… but with different parametrizations, different forcings, different simulations of nebulosity/insolation, different complexities… so we must suppose it’s not so difficult to reproduce the modest 0,76 °C slope for 1850-99 / 2005 — and to reproduce it uncorrectly).
Ingram 2006 :
http://www.ingentaconnect.com/content/klu/spac/2006/00000125/F0040001/00009057
The physical question is : do we fully understand solar effects on climate and do we fully implement the mechanisms in models ? I guess the answer is no and no, as Haigh pointed it in the introduction of the special issue of SSR I mention above. So, there’s no reason to believe attribuction-detection of climatologies will not evolve in the future, as well as climate sensitivity for 2xCO2.
An earlier try at something like this was Soon and Baliunas, Ap J 472 (1996) 472. Failed, and was commened on in the TAR
The solar expert Leif Svalgaard had some interesting postings on Tamino’s blog arguing for a floor in solar activity at sunspot minimum, i.e. that solar forcing at the Maunder minimun is about equal to today’s. He has some interesting papers on his website, see http://www.leif.org/research/
Back to the S&W paper, could anyone give a reason for why the two “doctored” TSI curves (which are equal after 1950) show a difference in modelled temperature for the last decade increasing to 0.1 degree (figure 6b)?
Re #38: More than that, Erik, IIRC he argues that irradiance hasn’t varied at all (and will be presenting at AGU to that effect). In addition, he stated that the latest S+W paper is invalid on its face because the data sets upon which it’s based are no longer deemed valid. If nobody beats me to it, I’ll see if I can pull out his specific remarks later.
Joao,
I do not no much about this study but I can say that it was treated cautiously on BBC radio news:
I can include the following extract from the original report:
http://www.preventionweb.net/globalplatform/first-session/docs/session_docs/ISDR_GP_2007_3.pdf
Note 1
By analysing the EM-DAT database, it is possible to reveal patterns and trends in disaster occurrence and loss globally, comparing countries, comparing time periods and comparing hazard types. The EM-DAT database contains data entries from 1900 through to the present, and registers events as disasters if they produced 10 or more deaths, 100 or more affected people, or where a state of emergency was declared or a call for international assistance was made. The data has a global level of observation and a national scale of resolution. The data is gathered from UN agencies, government sources, IFRC, insurance sources, press and others and is maintained by CRED. EM DAT has a number of data fields including, numbers killed and affected, and economic losses.
The BBC implied that this statement represents what the authors defined as a disaster.
Two of these:
“a state of emergency was declared” or “a call for international assistance was made”
the BBC noted that these are political decisions not objective measures.
I hope this helps you.
Best Wishes
Alexander Harvey
Question- can you pull the difference between 1900-1950 and 1950-2000 from the S&W2007 data alone because it is pretty well established solar was more important earlier on, with anthropogenic dominating in the second half of the century. But the period of interest in the paper (the 50% number) is from 1900. Still an overestimate, but the number is higher when you include earlier in the century.
Joao,
Here is the Oxfam page that contians the link:
http://www.oxfam.org.uk/resources/policy/climate_change/bp108_weather_alert.html
and the headline quote:
The total number of natural disasters has quadrupled in the last two decades – most of them floods, cyclones, and storms.
Please excuse my harsh comments on the writing and thanks for the edits. It’s a very interesting piece—and yes I would prefer to have imperfect prose than no prose.
[Response: ..and I should take more time to check the prose of my own post. -rasmus]
Re 15 To Gavin’s response:
Gavin, you do know I critizise unjustified certainty and we both know Climatology is all about probabilities and uncertainties, even unknowns, only.
It’s strange how scientists interested in probabilities are annoyed about scientists interested in uncertainties (to put it nicely).
Re 22 Ray:
Additionally to above, too often I see Logical Fallacies when the cause identified actually is only a (tiny) part of a whole gengre of causes.
Re 33 Rasmus’ response
Rasmus writes “Poor papers will be torn apart, and when authors know that they risk their paper being scrutinized and criticized, they will hopefully take more care to check their analysis”
Well, if you behave otherwise, i.e. rely the studies you like, and don’t rely the studies you don’t like, you are no scientists.
Scepticism, criticism, validation and replication are the only means Science can survive.
[Response: Scientific debate and discussion is important – actually essential. We can at least agree on that. -rasmus]
….
Well, no comments so far about ocean inertia.
When the sun has been exceptionally active and 80 % of solar heating sinks into the oceans, in recent years I have several times inquired whether the current warming were a coincidence of numerous variations, oscillations and cycles originating from the oceans?
But, unfortunately, as Carl Wunsch has pointed, the oceans are a similar nonlinear, chaotic and turbulent system as the atmosphere.
Like it or not, but so far I see more uncertainties than probabilities.
#38 Erik Hammerstad,
From S&W para 31:
“Figure 6 shows the comparison between the two NH
temperature reconstructions shown in Figure 1 and the
phenomenological solar temperature signatures obtained
with the TSI proxy reconstructions corrected with the
ACRIM TSI satellite composite since 1980, as shown in
Figure 3.
By assuming ACRIM, the solar activity has an
increasing trend during the second half of the 20th century.”
That’s why there’s a difference in modelled temperature for the last decade between 5b & 6b.
At 27, Rasmus writes
[Response: Actually, I’m saying you can’t have a long relaxation time and a dominant solar driver. The clue to S&W’s argument is that precisely this combination is used to explain the recent global warming. I also say that the climate responds to many forcings (GHGs, aerosols, volcanoes, solar, etc), but there are also internal variations. -rasmus]
What, precisely, are these internal variations and what is their approximate magnitude and sign compared to forcings typically used in GCMs? I mean “precisely”, not a wave of the arm. 35 years in geology helps understand. What really caused the surface temperature drop, say 1940-70? You skirt all around the answer but you don’t answer it. Precisely.
[Response: Precisely? – should we ignore the uncertainties in the forcing history, the difference in the transient behaviour in the real world and any one model simulation? Precision is all well and good, but I prefer accuracy. The accurate statement is that some part of the 1940’s to 1970’s change was likely driven by aerosols, and some part was due to the internal variability – possibly related to ocean circulation changes in the Atlantic making the 1940s anomalously warm. All of these proportions can be estimated, but the error bars are large. Thus no ‘precise’ attribution is ever likely to be credible. Unfortunate, but that’s just how it is. – gavin]
Next, at 33, Rasmus notes in response to funding for authors and possibilities of undue influence – [Response: To, blogs (like RC) may play an important role, as papers get discussed. Poor papers will be torn apart, and when authors know that they risk their paper being scrutinized and criticized, they will hopefully take more care to check their analysis. -rasmus] Question. From where does the financial backing for Real Climate weblog come? [edit]
[Response: RC is a volunteer effort. No one gets paid for anything. Our annual expense are $30 for the domain name registration. – gavin]
What I love about RC :-)
Someone earlier enquired about the differences in the Solar TSI reconstructions, and especially the PMOD/ACRIM ones. I think this issue has been treated unfairly in this RC article, and I think it is due to a lack of understanding on the ACRIM project. The actual ACRIM website goes into detail about both these reconstructions, and why they believe the ACRIM one is probably more accurate.
http://www.acrim.com/
In Summary, what I feel is not being represented here is that BOTH the ACRIM and PMOD reconstructions use the ACRIM dataset from both ACRIM I and ACRIM II – You need to understand this. The problem lies in the ‘ACRIM GAP’ This was a two year period in which the ACRIM II satellite was delayed due to the Shuttle Challenger Disaster. To fill this two year gap ONLY the PMOD and ACRIM used other data to fill the gap years.
Full details of this are on the ACRIM website. Also F&L used one of these reconstructions in their paper earlier in the year, and yet the validity of them using a ‘patched up’ TSI series was not even challenged by RC – so why drag this up for this paper?
Simply speaking there are still major sensor problems in current TSI measurements. SORCE/TIM and ACRIM 3/ACRIMSAT both give differences in TSI readings in the order of almost 5 w/m2 ! It is still not understood why this is, as stated on the website, and hence modern measurements of TSI are anomalous to say the least -when the two current modern satellites give readings that are so apart.
People on here seriously need to read and understand the information on http://www.acrim.com/ before making some of these misguided comments.
#45 Timo Hämeranta,
The link you posted doesn’t work for me, but the paper is available from Wunsch’s page http://puddle.mit.edu/~cwunsch/ Link entitled “C. Wunsch, 2007. The Past and Future Ocean Circulation from a Contemporary Perspective, in AGU Monograph, 173, A. Schmittner, J. Chiang and S. Hemming, Eds., 53-74, (pdf) ” Wunsch’s publications page is great food-for-thought, I particularly enjoyed his papers on Ice Age changes and the Milankovitch cycles. But I’ve not read that one – yet.
I pondered the ocean while still sceptical, once I’d satisfied myself that there was no evidence for a solar role in the recent warming (0.6degC in the last 30 years). This is very roughly why I ditched the oceanic line of thought:
If the ocean were the source of the warming:
1) Why is the warming concentrated over land in the Northern Hemisphere? http://data.giss.nasa.gov/gistemp/graphs/
2) Why does there seem to be a correlation between warming rate and changes of “global dimming” (Wild) indicating a radiative source for the warming.
3) Why the diurnal range changes and vertical profile of changes? Surely the ocean causing the warming (at the base of atmosphere) would cause a warming in all parts of the atmosphere.
There may be other points – this is a rushed lunchtime post. I don’t see from the abstract you quote how that work supports an oceanic cause for the recent warming. The atmosphere may well be chaotic etc – however we still see the hadley cells shift in a reliable enough manner for cultures to have prospered for centuries with monsoonal rain patterns. i.e. chaotic does not mean devoid of predictable patterns.
You are right in that there’s a lot of uncertainty, but I disagree that such uncertainty means we can attribute the observed warming to the ocean, or vulcanism, sensible industrial heat emissions, Piratic upwelling reductions etc etc etc
As far as I can see, the best bet for explaining the last 30 years remains CO2. My attitude – go with the best working theory until/unless you have enough evidence to go with an alternate.
PS “rely the studies you like, and don’t rely the studies you don’t like, you are no scientists.” In view of S&W’s lack of argument for choosing ACRIM over PMOD I wonder to whom you should be addressing that statement. In my experience it’s the denialist camp that engages most in cherry picking.
That reminds me: I must check to see if you have enlightened us as to the rationale for your raising arctic oceanic circulation during what I recall was a discussion about the (atmospheric) AO.
Timo, re: 45,
My beef with your approach is that you are emphasizing uncertainties without considering their relative magnitudes or without considering the likely importance of the effects of those uncertainties. OK, let us say the oceans do wind up being more important (there’s no evidence supporting this, but assume it anyway). Does that mean that we will reduce CO2 sensitivity? No, because it is constrained by many independent lines of evidence. Rather, the give would have to come from some other less certain piece of the puzzle. Bottom line, only the feedbacks would likely change, and the feedbacks are more likely to result in an increase than a decrease (since that’s how they are distributed).
Being a scientist means learning to deal with uncertainties and make predictions that take them into account. It does not mean throwing up you hands when confronted with a complex system and saying that it is beyond all human understanding.
CO2 is emphasized because you simply cannot explain what is going on without it. That does not mean that other factors are being ignored.