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Les Chevaliers de l'Ordre de la Terre Plate, Part II: Courtillot's Geomagnetic Excursion
— raypierre @ 18 December 2007 - ( )
This article continues the critique of writings on climate change by Allègre and Courtillot, started in Part I . If you would like to read either post in French, please click on the flag icon beside the post title above.
Prelude: It's the physics, stupid
…which of course is a paraphrase of Bill Clinton's famous quote regarding the economy. We put the last word in small letters since we've learned that it is not a good debating technique to imply (even inadvertently) that those who are having trouble seeing the force of our arguments might be stupid. What we wish to emphasize by this paraphrase is the simple fact that the expectation of a causal link between increasing long-lived greenhouse gases (like CO2) and increasing temperature does not rest on some vague, unexplained correlation between 20th century temperature and 20th century greenhouse gas concentration.
The anticipated increase in temperature was predicted long before it was detectable in the atmosphere, indeed long before it was known that atmospheric CO2 really was increasing; it was first predicted by Arrhenius in 1896 using extremely simple radiation balance ideas, and was reproduced using modern radiation physics by Manabe and co-workers in the 1960's. Neither of these predictions rests on general circulation models, which came in during subsequent decades and made more detailed forecasts possible.
Still, the basic prediction of warming is founded on very fundamental physical principles relating to infrared absorption by greenhouse gases, theory of blackbody radiation, and atmospheric moist thermodynamics. All these individual elements have been verified to high accuracy in laboratory experiments and field observations. For a time, there was some remaining uncertainty about whether water vapor feedback would amplify warming in the way hypothesized in the early energy balance models, but a decade or two of additional observational and theoretical work has shown that there is no real reason to doubt the way in which general circulation models calculate the feedback. When modified by inclusion of the cooling effect of anthropogenic aerosols, the theory gives a satisfactory account of the pattern of 20th and 21st century temperature change.
No other theory based on quantified physical principles has been able to do the same. If somebody comes along and has the bright idea that, say, global warming is caused by phlogiston raining down from the Moon, that does not make everything we know about thermodynamics, infrared absorption, energy balance, and temperature suddenly go away. Rather, it is the job of the phlogiston advocate to quantify the effects of phlogiston on energy balance, and incorporate them in a consistent way beside the existing climate forcings. Virtually all of the attempts to poke holes in the anthropogenic greenhouse theory lose sight of this simple and unassailable principle.
In a paper entitled "Are there connections between the Earth's magnetic field and climate?" published recently in Earth and Planetary Science Letters, Courtillot and co-authors attempt to cast doubt on carbon dioxide as a primary driver of recent (and presumably future) climate change; he argues instead that fluctuations in the Earth's magnetic field (partly driven by solar variability) have an important and neglected role. Like most work of this genre, it is carried out in an intellectual void — as if everything we know currently about physics of climate had to be set aside in order to make way for one new (or in fact not-so-new) idea. But the problems don't end there. With the help of a Comment published by Bard and Delaygue (available here at EPSL or here as pdf) , we'll expose a pattern of suspicious errors and omissions that pervades Courtillot's paper. Sloppiness and ignorance is by far the most charitable interpretation that can be placed on this pattern.
Let's set the stage by noting that, as a significant competitor to anthropogenic greenhouse forcing of recent climate change, the direct radiative forcing by solar irradiance variations is dead on arrival. The solar output has been monitored by accurate satellite instruments since 1978. Measured peak to trough over the 11 year solar cycle, averaging over the Earth's surface and allowing for albedo, the radiative forcing amplitude is under 0.2 W/m2. The trend left after averaging over the solar cycle is even smaller. This pales by comparison with over 2 W/m2 of radiative forcing arising from long-lived greenhouse gases that have accumulated in the atmosphere since 1750; it pales yet more by comparison with the forcing to come in the future if action is not taken to control emissions. There is nothing in climate physics to suggest that the sensitivity of climate to solar irradiance variation differs substantially from the sensitivity to infrared radiative forcing arising from greenhouse gas changes. As far as the climate cares, a Watt is (for the most part) a Watt, regardless of whether it comes from changes in the incoming solar energy or greenhouse-induced changes in the infrared radiation loss.
To get a bigger bang out of solar variability, one needs to invoke something else about the way the Sun affects climate. Something exotic, like magnetic field variations. Since there is no quantified physical mechanism linking field variations to climate, Courtillot must fall back on showing us a few supposed correlations between temperature variations and magnetic field variations. To make matters worse, Courtillot can't always make up his mind even about whether an increasing field index should warm the climate or cool it, making it unclear just what correlations one is looking for. The lack of a physical model makes it impossible to treat the various forcings on an equal footing and make a reliable attribution of causes. This is particularly fatal when the various forcings are strongly correlated with each other. For example, on time scales of years to centuries, the magnetic field variability, cosmic rays and solar irradiance vary nearly in lock-step, so if there is a correlation with temperature (or cloud cover) one cannot tell whether it means that climate is responding with high sensitivity directly to luminosity changes, or whether something more exotic is going on. Over a period when temperature, greenhouse gas forcing, and some magnetic field index are all going up, a statistical attribution technique which ignores greenhouse gases and considers only the magnetic field index will of course find that the magnetic field "explains." the signal. If we knew nothing about how CO2 affects climate, this would put the magnetic field on an equal footing with CO2 as a candidate explanation but this is not the case. We know a great deal about how CO2 affects climate and no amount of additional fiddling with cosmic rays or magnetic fields can make this physics go away. One can get even more confused by forgetting about the important role of anthropogenic aerosols in the past century, as Courtillot all too often does.
The confidence with which Courtillot casts doubt on the generally accepted role of anthropogenic forcing in climate change of the past century is surprising, in view of the essential limitations of any argument from correlation alone. But it's worse than just that: as Bard and Delaygue show, most of the correlations upon which Courtillot et al. rest their flimsy case are in fact bogus.
Solar variability and climate: The Good, the Bad, and the Ugly
Work on the influence of solar variability (and on its close cousin, the influence of the Earth's magnetic field) tends to fall into one of three categories. There is the Good, in which careful scientists do their objective best to unravel a complex and probably small (but nonetheless important) signal. As examples of work in this category, I would mention Judith Lean's tireless efforts on relating luminosity to sunspot number, the work of Bard and colleagues on developing isotopic solar proxies like 10Be, Shindell's work on response to solar ultraviolet variability, and the work of Foukal et al on factors governing solar irradiance variations. I would also include the recent work by Camp and Tung diagnosing the amplitude of the solar cycle in temperature in the "Good" category; that it is an easy paper for greenhouse skeptics to misquote takes away nothing from the quality of the science. In fact, I'd say most work on climate and solar variability falls into the Good category. That's rather nice. In fact, scientists have long recognized the importance of solar variability as one of the factors governing climate (see the very scholarly review of the subject by Bard and Frank, available here at EPSL or here as pdf) An understanding of solar variability needs to be (and is) taken into account in attribution of climate change of the past century, and in attempts to estimate climate sensitivity from recent climate variations. Further, the Little Ice Age demands an explanation, and solar variability at present provides the only viable possibility. (It's less clear that the Medieval Warm period is a sufficiently coherent phenomenon to require an explanation).
Then, there is the Bad, exemplified by two papers by Scafetta and West that have been discussed on RealClimate here and here. This is just normally bad science, in the sense that there is something wrong in the approach taken by the authors which leads to erroneous conclusions. Perhaps some of this work should never have made it through peer review, but as long as the methods are well documented and honestly described, subsequent investigators will be able to identify the errors and either salvage or discard the results.
And then … there is the Ugly. These papers cross the line from the merely erroneous into the actively deceptive. Papers in this category commit what Damon and Laut judiciously call a "Pattern of strange errors.". Papers in this category often use questionable (and often hidden and undocumented) data manipulations to manufacture correlations where none exist. The work by the Danish solar boosters, discussed extensively by Damon and Laut, typifies the Ugly category. We'll leave it to the reader to decide, after the discussion to follow, whether Courtillot's paper is merely Bad, or has crossed over into the Ugly.
Spin vs. Scholarship
The general style of discourse in Courtillot et al. has more in common with the kind of one-sided polemic one finds in Lomborg or the Robinson et al. fake PNAS article distributed with the original Global Warming Petition Project than it does with scholarship whose intent is to get at the truth. It quotes papers uncritically and selectively if they can be made to appear to support the authors' thesis (e.g. the uncritical use of the aforementioned single-factor Scafetta and West paper to support a large attribution of twentieth century climate change to solar variability). There is also a lot of general spin here; for example, greenhouse gases are listed last in a laundry-list of things that can affect climate, without any indication as to the relative magnitudes of the various forcings. Other problems include the following:
Courtillot exaggerates the cloud radiative forcing by a factor of four, because he attributes virtually all the Earth's albedo to clouds and fails to take into account the cloud greenhouse effect.
He says that "Cooling from 1940 to 1970 is often disregarded as being part of the noise" whereas in fact it was intensive study of this period that lead scientists to appreciate the importance of the anthropogenic aerosol effect, at the time of the IPCC Second Assessment Report. Again ignoring the well-documented importance of anthropogenic aerosols, he says later: "Note that the leveling or drop in temperature from 1940 to 1970 matches solar and magnetic series, and not the monotonous accelerated rise in CO2" Not only is this a Crichton-esque obfuscation of a well-understood phenomenon, but as we'll see later the supposed "match" is an artifact of questionable data manipulations.
Courtillot points to an energy-balance model study by Crowley as support for his thesis that there is some missing physics left out of models, which affects response to solar forcing. Specifically, Courtillot points to a model/data mismatch in the early 20th century. However, Crowley did not include the indirect aerosol effect, and the energy balance model has no geography and therefore can't be expected to model things like continental vs. ocean seasonal cycles or ice and snow cover with complete fidelity. General circulation models forced with a combination of natural (including solar) and anthropogenic (aerosol and greenhouse gas) forcing have no problem reproducing early 20th century climate. Further, Crowley's model accurately matches the observed response to solar forcing earlier in the millennium, so it is hard to see why the "missing physics" should suddenly kick in at 1850. It is always suspicious when selective quotes are used to draw a conclusion exactly opposite to what the paper's own author concludes. For the record, here is what Crowley himself says in the paper about his own results:
There are therefore two independent lines of evidence pointing to the unusual nature of late-20th-century temperatures. First, the warming over the past century is unprecedented in the past 1000 years. Second, the same climate model that can successfully explain much of the variability in Northern Hemisphere temperature over the interval 1000–1850 indicates that only about 25% of the 20th-century temperature increase can be attributed to natural variability. The bulk of the 20th-century warming is consistent with that predicted from GHG increases. These twin lines of evidence provide further support for the idea that the greenhouse effect is already here.
Courtillot also cites an atmosphere-ocean model simulation by Zorita et al. (2004) as support for his claim that models fail to represent the 20th century response to solar or magnetic variability. However, as discussed here and in the peer-reviewed references cited therein, this simulation suffers from an inappropriate initialization which leads to a spurious cooling in parts of the run, and a large climate drift requiring detrending of the output before analysis. Besides that, the model explicitly neglects anthropogenic aerosol forcing, so how could one expect it to get 20th century climate right?
Courtillot claims that the correlation between geomagnetic "jerks" and Alpine glacier advances supports a solar-magnetic influence on climate. As Bard and Delaygue emphasize, this requires an exactly opposite sign of response to magnetic field variations as claimed by Marsh and Svensmark (2000), and as assumed elsewhere in Courtillot's paper. Courtillot cooks up an ad hoc explanation for why this might be the case, but this leads him even farther afield from anything that can be justified by known, quantified physics. One can find all sorts of correlations if one allows oneself the liberty to change the sign of the sought-for relation whenever convenient, and without any constraint by physics.
There is hardly anything more embarrassing to a theory than success in explaining a phenomenon that turns out not to exist. Courtillot makes much of the fact that the millennial cycle of hematite-stained ice rafted debris in Gerard Bond's data set — taken at the time to be a proxy for North Atlantic temperature — lines up nicely with geomagnetic variations. However, as Bard and Delaygue note, later work with better chronology, more cores and better time resolution show that Bond's record does not represent a temperature index for the entire northern Atlantic region. The more complete record exhibits little or no relation to geomagnetic variations.
…and now for the really ugly part
Bard and Delaygue uncovered a number of errors of a more troubling nature. Courtillot et al. commit the "flat Earth" error from which our article draws its name: they give a misleading impression of the comparison of forcing by solar variability relative to greenhouse gas forcing by failing to take into account the Earth's spherical geometry and albedo. After the very public humiliation suffered by Le Mouel on this point at the Academie debates (see Part I), in his article in La Lettre Courtillot took pains to show that he indeed understood the consequences of the Earth being round. However, this new understanding did not result in any sign of a corrigendum being sent to EPSL, so one can only conclude that the deception is deliberate. Further in their Fig. 1 Courtillot et al. show geochemical data from a Central Alpine stalagmite which purports to establish a highly tight correlation between climate variations and a solar activity proxy; as Bard and Delaygue note, Courtillot and co-workers have concealed the fact that the correlation is so good precisely because the chronology of the two series being compared has been finely tuned to expressly maximize the correlation. The original untuned data does not show nearly so tight a correlation.
The piece de resistance of Courtillot et al., is the following graph, which purports to show that for almost all of the past century, temperature correlates tightly with solar activity and magnetic field variability. The three curves on the graph are, according to the paper, Phil Jones' global mean temperature record (Tglobe, in red circles) , a total solar irradiance reconstruction (S(t), in pink triangle; Courtillot cites Solanki's reconstruction in the text), the magnetic field variability index at a site in Scotland (ESK, blue) and at Sitka Alaska (SIT, green). All the curves have been centered to have the same mean and standard deviation over the length of record, so as to make them more comparable. Note that the S(t) curve spans a shorter time than the others; this turns out to be important.
Looks pretty good, eh? Well it would, except for the minor details that "S(t)" is not actually the solar output, "Tglobe" is not actually the Jones global mean temperature it is claimed to be and neither "ESK" nor "SIT" look much like broader-based magnetic variability indices that provide more reliable indicators of solar activity. Bard and Delaygue thought it curious that Courtillot would use just the final snippet of the Solanki record when the full century was available. They checked what the curve would look like if it were normalized using the full length of the record. That's the thick grey curve in Bard and Delaygue corrected version of the figure below; for comparison, the purple curve with triangles shows the results of using Solanki's reconstruction truncated to the period Courtillot chose.
Get the picture? By snipping out just the last bit of the curve and normalizing to unit standard deviation, Courtillot inflates the variability and makes the fit look better than it would be if the full data set were used. As a bit of deceptive data manipulation, this has to go down in history with the selective smoothing used on some of the solar records that Damon and Laut discuss in their critique of the Danish solar work. Now, in his response to Bard and Delaygue (there's always a response to Comments) Courtillot digs himself even deeper into a hole. He states that the reason he used a truncated solar series is that the data came not from Solanki (as implied in the paper), but rather from Tobiska's SOLAR2000 model product. Tobiska's paper is not even cited by Courtillot et al. (2007), whereas Solanki (2002) is cited there as well as in the authors' earlier papers on related subjects. There is no legitimate reason for using SOLAR2000 in a study of the sort Courtillot et al. are attempting since, as noted by Bard and Delaygue, the SOLAR2000 model is restricted to the ultraviolet portion of the solar spectrum, making it the wrong choice unless one is explicitly investigating phenomena linked to ultraviolet forcing (see Lean (2002) ). One could guess that Courtillot et al.pulled this convenient rabbit out of the nearest available hat, because it was the first curve they found that gave them some excuse to truncate the record in a way that gave the desired result.
Bard and Delaygue noticed another strange thing. Courtillot's "Tglobe" curve did not look much like the curve published by Jones. Jones' curve, plotted from his actual data files, is shown in Bard and Delaygue's corrected version of the figure; they also show the NASA reconstruction for comparison. These two curves are in agreement, but neither shows the sharp rise/dip pattern between 1940 and 1970 which is seen in Courtillot's figure. So if Courtillot's data is not Jones' global mean temperature, what is it that Courtillot plotted? We may never know. In his response to Bard and Delaygue, Courtillot claims the data came from a file called: monthly_land_and_ocean_90S_90N_df_1901-2001mean_dat.txt. Bard and Delaygue point out, however, that Jones has no record of any such file in his dataset, and does not recognize the purported "Tglobe" curve as any version of a global mean temperature curve his own group has ever produced.
Whatever the source of the purported "Tglobe" data given in Courtillot et al., there is no legitimate reason — in a paper published in 2007 — for truncating the temperature record at 1992 as they did. There is, however, a very good illegitimate reason, in that truncating the curve in this way helps to conceal the strength of the trend from the reader, and shortens the period in which the most glaring mismatch between solar activity and temperature occurs.
In the corrected graph, Bard and Delaygue also plot the "aa" geomagnetic index. This is an index based on two stations at antipodal points, which has been found to correlate well with the overall geomagnetic variability based on a larger network of stations. One could argue that if one is looking at global mean temperature data, the aa index provides a more appropriate basis for comparison than the single-station high Northern latitude records that Courtillot uses. Note that the aa index tracks Solanki's solar irradiance well, whereas the single-station measurements do not.
In the corrected graph, Tglobe, aa and S(t) track each other upward from 1900 to 1940, but note that greenhouse gases also go up monotonically in this period, as they do later. A purely statistical attribution could ascribe nearly all the changes from 1900-1940 to solar or magnetic variability, but a similar statistical attribution could do the same for greenhouse gases. Only physics can divvy up the blame. Since 1940, however, there is not even the appearance of correlation between Tglobe and either S(t) or any of the geomagnetic indices. There is a hump in both the solar and aa index around 1950, during which time the temperature is flat or decreasing. Courtillot's erroneous analysis defers the decorrelation until 1985.
Between the embarrassing showing at the Academie debates and the travesty of science exposed by Bard and Delaygue in the case of the EPSL paper, You'd think that Courtillot would want to fine the nearest hole and go hide in it. Far from it, he was recently spotted giving a talk called "What global warming?" at this prestigious event gathering several famous physicists and chemists. Some people have no shame.
Postlude: Of silk purses and sow's ears
Bard and Delaygue conclude with a figure, reproduced below, which nicely illustrates something we've been saying for years at RealClimate. On this figure they plot the Jones global mean temperature together with a global magnetic index (the aa index), a cosmic ray flux index (Climax) and the PMOD composite satellite record of solar irradiance. These curves are less smoothed than those shown in the preceding graph. The inter-annual temperature variability is linked to natural effects such as major volcanic eruptions, ENSO events and solar variability. However, only the Tglobe curve is characterized by a very significant upward trend — a trend which cannot be explained by these natural causes.
Say it three times every night before going to sleep: Temperature goes up. Solar stuff goes up and down and up and down and up and down. You can no more make a trend out of that than you can make a silk purse out of a sow's ear.
A note added in proof, concerning the "Note Added in Proof"
The above discussion was based on the version of Bard and Delaygue's comment and Courtillot's response which was available on the Elsevier web site through December 15. Since the time of writing, some strange changes have occurred under the direction of the responsible editor, Robert van der Hilst of MIT. He deleted the "Note added in Proof" from the final version of Bard and Delaygue's comment. Bard and Delaygue only found out about this when they received the proofs of their Comment. What is even more disturbing is that van der Hilst allowed Courtillot to change the text of his Response based on what Bard and Delaygue wrote in the now-deleted "Note added in Proof." Bard and Delaygue were given no opportunity to see or comment on these changes. I have left the above discussion as it is, in order that the reader will have a better appreciation of the strange history of this comment/response cycle.
In the revised "Response" Courtillot now admits that the temperature record called "Tglobe" is not from any of Phil Jones' datasets at all. Courtillot now claims that the data came from a study by Briffa et al. (2001), giving the address of a file stored at NCDC. As specified in this study and in the head of this file, these data have been "recalibrated to obtain estimates of April-September mean temperatures from all land regions north of 20N". Thus, the temperature dataset used by Courtillot is definitely not Tglobe, does not represent the full hemisphere, and moreover is not even an annual mean.
Rob van der Hilst — recently a Visiting Professor at IPGP (Courtillot's institution) — claims that these changes were made in the interests of scientific communication. I leave it to the reader to judge whether these actions were appropriate, or whether they were just an attempt to protect Courtillot from embarrassment.. In the interests of scientific communication, I append below the full text of the "Note added in Proof" which was stripped from Bard and Delaygue's Comment:
Note added in proof:
In their Response to our Comment, Courtillot et al. state that for the total irradiance curve S(t) they had used the SOLAR2000 model product by Tobiska (2001) instead of the century-long record by Solanki (2002) cited in their original paper (Courtillot et al. 2007). However, the SOLAR2000 model is restricted to the UV component and their total solar irradiance is severely flawed as pointed out by Lean (2002).
For the global temperature Tglobe curve cited from Jones et al. (1999) in Courtillot et al. (2007), these authors now state in their response that they had used the following data file: monthly_land_and_ocean_90S_90N_df_1901-2001mean_dat.txt We were unable to find this file even by contacting its putative author who specifically stated to us that it is not one of his files (Dr. Philip D. Jones, written communication dated Oct. 23, 2007).
Tobiska, W. K. 2001, Validating the solar EUV proxy, E10.7, J. Geophys. Res. 106, 29,969- 29,978.
Lean, J.L., 2002. Comment on "Validating the solar EUV proxy, E10.7" by W. K. Tobiska. J. Geophys. Res. 107, (A2), 1027, 10.1029/2001JA000137.
148 Responses to "Les Chevaliers de l'Ordre de la Terre Plate, Part II: Courtillot's Geomagnetic Excursion"
Russ Hayley says:
The newscientist had an article that seemed to blame the fall in global temperatures in the 50s to sulphate aerosols.
http://environment.newscientist.com/channel/earth/mg19225822.300-histories-the-ice-age-that-never-was.html
[Response: Yes, indeed. That is the best-supported explanation for the interruption in global warming in the 50's, and indeed in some regions this even shows up as an actual decline in temperatures. There is more uncertainty in aerosol forcing than in GHG radiative forcing, but what I said about "it's the physics" applies to cooling influences like aerosols as well as warming influences like GHG — if somebody wants to say phlogiston (or magnetic fields) explain mid-century cooling, they can't just ignore the known influences of aerosols when trying to do an attribution. –raypierre]
Pascal says:
raypierre
for the Camp and Tung paper, I don't understand, as I said in a precedent post, how it is possible that a 0.17W/m2 radiative forcing leads to 0.18°K temperature increasing.
The 0.17W/m2 solar forcing in 5.5 years (between a minima and a maxima) corresponds to 0.031W/m2.y .
You said that oceanic thermal inertia doesn't react in the same manner because it is a rapid variation compare to GH effect increase.
For this last effect,if I take +2ppmCO2/y I find 0.028W/m2.y.(for CO2 only and without other GHG, aerosols, ..).
So how do you look at this (apparent for me) contradiction?
[Response: You've put your finger on precisely the puzzling thing about the C&T results, which will need to be sorted out by a more detailed analysis of the oceanic response in the IPCC AR4 models. I can only explain their result by a combination of high sensitivity and low thermal inertia. But why should the thermal inertia that explains the solar cycle response be so much lower than the thermal inertia needed to explain the seasonal cycle over oceans? Camp and Tung are on to something interesting, but I don't think it can be said that we understand what is going on yet. ]
But I think that also part of your problem is that you double-counted the geometric factor. That .17 W/m**2 I quoted already has the albedo and sphericity terms taken into account. As for your comparison to CO2, it is indeed true that taken over the time between solar min and solar max, the solar radiative forcing fluctuation is larger than that due to CO2 increase over the same period. However, when you compare the min to max solar forcing to the net GHG radiative forcing over the past century, solar looks like a minor player — especially in view of the fact that the min to max solar cycle amplitude is not the relevant number, For that , one needs to look to the long term trends in solar irradiance. –raypierre]
John Mashey says:
Raypierre mentioned phlogiston, clearing scoffing at the likelihood that it has anything to do with climate. However, last summer, in a journal RC readers might recognize, I ran across:
"Climate science and the phlogiston theory: weighing the evidence"
Arthur Rorsch, Energy & Environment 18, number 3-4, 2007. p441-447(7).
http://www.ingentaconnect.com/content/mscp/ene/2007/00000018/f0020003;jsessionid=7abb5un7rjvfi.henrietta
But, seriously, thanks for the nice analysis.
JEG says:
Great deconstruction job, Ray.
C'est accablant , but alas, totally unsurprising. Here is a little tale to give it context.
I happened to be passing through the IPGP this past January, when Courtillot and Allègre launched "allègrement" their Spring 2007 "climate skepticism seminar series". It started with the visit of well-known climate skeptic Richard Lindzen (MIT) – one of the few skeptics to actually know something about climate .
What non-French readers may not be aware of, is how abrasively obnoxious Allegre and his clique have been to the country and the entire French research community – some will say since 1968, when Allegre apparently showed himself so unbearable that he got literaly thrown out of the window at a student meeting in La Sorbonne (first floor …). There are countless such stories which need not be repeated here.
As a young and innocent student who got into Earth Sciences in 1998 (while Allègre was still ministre de la Recherche et de l'Education ), all i could hear about, anywhere i went, was resentment towards his bullish and pretentious practices. I originally thought it was born out of jealousy for his political success, but had to surrender to the evidence : obnoxious is his style and did not improve after his tremendous unpopularity forced him to resign from the ministry.
On the contrary, it seems that he's been missing media attention , and that gratuitous climate skepticism has given him an ideal platform to get closer to a mic.
The Lindzen seminar started by a pompous introduction by his first lieutenant (squire ?) Courtillot about how misguided climate science currently is, and the need to do this work "properly". His tone was the usual heatedness and anger that i have seen stain all his recent public addresses. Needless to say, there was considerable uproar in the room, with much of the Parisian climate community come to hear the fireworks. Allègre's clique on the front row vs climate scientists filling much of the room behind them. Lindzen bemusedly watched the verbal joust for a good 10 minutes, fully aware that he the fight was not about him.
Clearly, it was not about climate science : it was about Courtillot and Allègre throwing "a stone in the pond" of climate scientists, desperately trying to come out of political oblivion.
Add to that Courtillot's notorious tendency of defending ideas in the face of a towering pile of evidence (like that of all major mass extinctions, in particular the Cretaceous/Tertiary one, having been caused SOLELY by volcanic eruptions), and there is little wonder what this is about : Devil's advocacy as an attention-seeking practice.
It is very sad, because their track record does prove that they can do good science when they want to. Like Lindzen…
I admit I have my doubts about the Camp & Tung result. I'm not saying it's wrong, just that I have my doubts.
For one thing, they detect solar-cycle response of 0.18 K, but in an earlier version of their paper the same graph which has this number has a different number quoted, namely 0.10 K — I'd need more details about their procedures to understand why. For another thing, I'm doubtful of the validity of their projection of the global temperature spatial pattern onto the "composite mean difference," by which they transform global average temperature to a newer, modified temperature time series — I suspect this step may artificially inflate the solar-cycle response. Again, I'd need more details to say with confidence. And then there's the fact that none of the temperature time series I've studied (HadCRU-T3 and GISS GLB_Ts+SST) show statistically significant response to the solar cycle, although they do not constrain the response to be less than the Camp & Tung value (at the upper limit of the error range).
If Camp & Tung turn out to be right, it wouldn't disturb me too much in terms of the rapid response. After all, the climate system has more than one active time scale; while the oceans drag their feet, the land-atmosphere system responds quickly (as volcanic eruptions confirm).
In any case, I repeat that I'm not saying they're wrong, just that I have my doubts.
As for the paper by Courtillot which is the subject of this post, it looks to me like it has gone way past "bad," deep into the bowels of "ugly."
Raypierre,
What an interesting post. It reads something like a spy novel.
The 'Note added in proof' appears in the PDF version at the link you gave: http://www.realclimate.org/images/BardDelaygue.pdf. That version is the 'Article in Press' version, not the published version. You may want to clarify this to avoid confusion.
As you say, the 'Note added in Proof' is gone from the online version currently available at on the website at ScienceDirect. It is intriguing to compare the 'Article in Press' version with the published version. Very strange editorial practice.
[Response: Yes, I ought to clarify that. The pdf linked is the version I downloaded from the EPSL site before van der Hilst deleted the Note. I made a separate copy mainly so readers without access to the journal could still read the comment, but in the end it served a separate purpose in providing a record of the original form. –raypierre]
Thanks for mentioning phlogiston, one of my favourite examples of how scientific theories develop.
This whole episode reminds me of one of my observations on the overall debate. It is a sophomoric debating trick to bolster a weak position by accusing the other side of all the flaws in your own argument — very effective when being judged by an audience unable to evaluate the argument on its merits.
John Mashey's reference (#3) to a phlogiston paper provides a classic example. Almost everything they say to establish conventional climate science as the new phlogiston applies much more aptly to their side of the debate.
Let's try a few arguments from the contrarian side:
* the "mainstream" is about correlations with no underlying physical model
— nope, there are numerous examples of this kind of bogus study in the contrarian camp, especially the various "blame the sun" positions which lack elementary tests of physical validity, like does the solar variance measured account for the change in observed temperature?
* the fits look good because the data has been massaged
— again, the solar crew is widely guilty of this: see not only this paper but also Soon and Baliunas's "it's all the sun" papers
* the mainstream is ignoring significant factors, only looking at CO_2
— not guilty: many contrarians on the other hand are happy to model the entire climate as controlled by a single variable; IPCC et al. generally try to include all quantifiable influences
I could go on but you get the picture.
The point is to recognize this stuff for what it is, and expose this debating tactic.
Great post, Raypierre! My you've been busy the past week or two!
[Response: Yah, time to get back to writing the book, I guess. At least I still managed to finish grading my final exams only a week late. I very much appreciate all the words of encouragment from the readers. –raypierre]
Robert A. Rohde says:
Minor quibble: Arrhenius 1896 provided the first measurement of the radiative forcing due to CO2 and estimated the potential impact of variations in its concentration. However, it wasn't until ~1908 that Arrhenius connected this to fossil fuel consumption to predict that temperatures would increase. Before that realization, speculations about CO2 were purely of academic/historical interest.
Incidentally, he estimated that it would take 3000 years for fossil fuel consumption to have a meaningful impact on climate. Sadly, he underestimated man's enthusiasm for burning fossil fuels.
Lab Lemming says:
You forget two things involving Allegre:
1. On the timescale of the Archean, a century and 10,000 years are both negligible.
2. A change in mean surface temperature of 5 degrees make no substantial difference to the cooling curve of a 1750 degree komatiite.
Physicists have put so much effort into measuring absorbtion and reflection of every wavelength by every concievable form of matter. There are also innumerable spectrometers in chemistry departments. I haven't checked, but I would guess that other departments would also have spectrometers. And you would think that Courtillot did not have access to the MIT Wavelength Tables.
It is really hard to understand how anybody could avoid the idea that the absorbtion bands of every gas have been cataloged and re-measured about a jillion times. Perhaps all high school students should be required to take 4 years of physics in which they spend about a semester measuring the spectra of CO2 and other things.
Another subject I would like to read RealClimate's comments on: See the chart on page 274 of "Six Degrees" by Mark Lynas. Mark Lynas says we have until 2015 to BEGIN REDUCING our total CO2 output and we have until 2050 to actually reduce our CO2 output by 90%. Mark Lynas says if we don't follow the schedule in Six Degrees, we will encounter positive feedbacks which will take the control of the climate out of our hands. Civilization may fall anyway well before 2050, but we can avoid going extinct by 2100. Mark Lynas says we have to hold the CO2 level to 400 parts per million to have a 75% chance of avoiding the positive feedbacks. Is Mark Lynas correct? 8 years is a very tough timetable to stop the building of coal fired power plants and replace some coal fired power plants with nuclear. I doubt that anything else other than a plague that kills a few billion people could make a dent within 8 years.
[Response: From other estimates I've seen, Lynas' timetable seems about right if the goal is to avoid 450 ppm. To avoid 400ppm, even his timetable is a bit of a stretch. However, with regard to the impacts of exceeding 400ppm (or even 450ppm), if you are quoting Lynas correctly I would differ with his assessment. There is no magic threshold crossed at 450 that commits us suddenly to the kind of catastrophic changes you mention, and certainly not to extinction of humanity by 2100. If we can't hold the line at 450, there are still harms to be avoided by stopping short of doubling. If we can't stop doubling, there are still harms to be avoided by preventing tripling, and so forth. But his general sentiment that we can't drag our feet on this is correct. –raypierre]
Russell Seitz says:
re4
Thanks for reminding us of the deposit of academic skeletons at the K-T boundary. America may require automation to catch up to the reflexive polemics of the IPGP:
http://adamant.typepad.com/seitz/2007/02/climate_of_list.html
Peter Williams says:
One thing I'm very confused about. I assume what we are talking about here is not inherent variations in the Earth's magnetic field (e.g. its dipole moment) due to the Earth's internal dynamo, but rather variations in the external field due to external forcings (e.g. the solar wind)? What is the basic idea? Is that energy is pumped into the atmosphere, say, by Alfven waves coming down through the ionosphere?
It would be nice to have an explanation of the physical mechanism that Courtillot supposes, and a back-of-the-envelope calculation giving the order of magnitude of the effect he would expect based on theory, independently of the empirical results. That's the sort of thing I'd expect as a referee, anyway.
> It is really hard to understand how anybody could avoid the
> idea that the absorbtion bands of every gas have been cataloged
> and re-measured about a jillion times.
Those avoiding this utter certainty that the science knows everything precisely can mostly be found publishing papers in the field.
I won't pretend I know what this means, but I take it they would disagree with your claim that everything is known already:
"The following improvements to Heller's theory have been made: (a) derivation of new recurrence relations for the time-dependent wave packet overlap in the case of frequency changes between the ground and electronically excited states, (b) a new series expansion that gives insight into the nature of Savin's preresonance approximation, (c) incorporation of inhomogeneous broadening effects into the formalism at no additional computational cost, and (d) derivation of a new and simple short-time dynamics based equation for the Stokes shift that remains valid in the case of partially resolved vibrational structure. …"
http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JCPSA6000127000016164319000001&idtype=cvips&gifs=yes
J. Chem. Phys. 127, 164319 (2007) (15 pages)
[Response: There's plenty in spectroscopy remaining to be understood, particularly with regard to the CO2 continuum as it applies to Venus and Early Mars. The theory behind collision-induced absorption is still pretty flaky. None of that compromises the kind of stuff that's needed to accurately calculate the GHG radiative effect in Earthlike conditions. ]
Minor point but your lead quote is from James Carville and not Bill Clinton.
[Response: Thanks for that. Though Carville coined the phrase, it was widely used in the 1992 Clinton campaign; I can't say that I've found any evidence that Clinton himself ever uttered it, though. Digging around, I also found out that the sign Carville posted in headquarter's didn't have the "it's" which somehow got added in later. –raypierre]
Charles Muller says:
Raypierre : the SOLAR2000 model is restricted to the ultraviolet portion of the solar spectrum
I used to think SOLAR2000 model (now Solar Irradiance Platform – SIP) is an irradiance specification tool which produces the full solar spectrum of historical Sun variations (or spectral formats, like UV, if needed for research). Do you have more precise information for SOLAR2000 limited to UV spectrum?
[Response: What I said applies more specifically to the Tobiska et al. application. Take a look at the paper by Lean cited in the "Note Added in Proof" and see if that helps. –raypierre]
Davinci says:
Interesting case, Ray. Media and the public are constantly remarked to refer to peer reviewing as the only credible source of information. The EPSL is not the last scientific publication, it has a reputation. If this case has been unveiled, how many other cases of "strange" reviewing may have been passed without notice?
And should the public be informed about such cases, or may this harm science at all?
[Response: Certainly the public should be informed. Cover-ups are never good. When faults in the editorial process are exposed, there's a better chance that they will be fixed. It would be easy to misread an incident like this as devaluing everything in the peer-reviewed literature, but that would be unfair. Cases like this are pretty rare. Usually, reviewing works pretty well, and even when something bad (or ugly) slips through, it is caught by the scientific community pretty quickly, if the result is important enough to check. That's why it's important not to make judgements based on an individual paper, but instead to watch for the follow-up. –raypierre]
Re #11, yes he is essentially correct I believe. The subject has been discussed here under the term "alarmist and alarmism". Due to uncertainties and non linear nature of the earth system of which climate is a part there are unknowns in regard to how the earth will respond to increased CO2 levels. Sulphates, aerosoles, clouds, forest cover and ice albedo all are understood within boundaries and the paleoclimatic record indicates that 1.4 to 4.5 (ie a mean of 3) is the range of temps available for a pre industrial doubling of CO2.
is climate is more sensitive than reported (IPCC often criticised for being too conservative) then we might experience 0.3/0.4 C per decade warming as oppossed to the current 0.2C and if levels get higher than yer 1.6C is already guaranteed (hence adapting to CC is needed) and another 0.4c is not far away. only one or two decades depending on sensitivity.
Edward Greisch posts:
[[ 8 years is a very tough timetable to stop the building of coal fired power plants and replace some coal fired power plants with nuclear.]]
You're right. We'll have to replace them with conservation, solar thermal, photovoltaic, wind, geothermal and biomass.
Richard Sycamore says:
"it's important not to make judgements based on an individual paper, but instead to watch for the follow-up"
Agreed. New science needs some time to season (i.e. weather criticism) before it can be safely taken up by policy makers. Haste makes waste.
[Response: To amplify on that sentiment, though, I do think it is fair to take into account the track record of the investigator, the degree of support for the idea that can be seen in prior work, and the nature of the argument when making a jugement of what the long term assessment is likely to be — while waiting for that assessment to materialize. Thus, while one ought to wait to see how the results of Camp and Tung hold up, given that Tung is quite meticulous and given the straightforward nature of his analysis of the solar cycle in the AR4 archive, I feel pretty confident that that result is likely to hold up. We shall see. Whether the observed solar cycle in surface temperature is as large as .17K (as in Camp and Tung) or more like .1K (many previous estimates) is somewhat more in doubt, as is their interpretation in terms of low thermal inertia and high climate sensitivity in energy balance models. –raypierre]
Some press coverage of this affair appeared in Liberation today. Check out http://www.liberation.fr/transversales/futur/298894.FR.php
And a report also in Le Monde:
http://www.lemonde.fr/web/article/0,1-0,36-991405,0.html
I think maybe the word "fraud" used in the headline of this article is going further than can actually be demonstrated at this point, which is why I preferred the judicious phrase used by Damon and Laut in connection with other work of this type: "A pattern of suspicious errors." Other than that, I think the article captures the nature of the issues pretty well.
Raypierre, I agree that fraud is too strong. I might choose delusion. The really odd thing is that with 10% of the effort the authors have devoted to deceiving themselves, they could actually understand the physics. It really does emphasize the importance of consensus in science.
Edward Greisch wrote: "8 years is a very tough timetable to stop the building of coal fired power plants and replace some coal fired power plants with nuclear"
Barton Paul Levenson: "You're right. We'll have to replace them with conservation, solar thermal, photovoltaic, wind, geothermal and biomass."
Conservation and efficiency are by far the fastest and most cost-effective ways to reduce carbon emissions, especially in the USA where we are profligate wasters of energy, and thus can easily reduce our energy consumption and associated emissions by applying readily available conservation and efficiency measures.
On the supply side, there is some very good news today: the California-based company Nanosolar has begun shipping their thin-film photovoltaic panels. The first panels will be used in a solar power plant in Germany, which will initially produce 1 megawatt of electricity. According to Nanosolar, their new ultra-cheap, flexible thin-film PV panels will enable the production of solar electricity for less than one dollar per watt — less than the cost of fossil-fuel or nuclear generated electricity. While the initial product offering from Nanosolar is for utility-scale applications, the same technology will eventually be available for small-scale distributed applications, including residential rooftops. Nanosolar says that their entire planned production of thin-film PV panels for 2008 has already been sold.
And yet more press:
http://www.20minutes.fr/article/202189/Sciences-Les-sceptiques-francais-du-climat-accuses-de-tricherie.php
#21, 22, 25…
Yes, a good example of what we call "pensée unique" in France: tomorrow, it will be l'AFP, Le Figaro, L'Humanité, this week-end Le Nouvel Obs, L'Express and Le Point, next month Science & Vie, La Recherche and Sciences & Avenir… But I'm pleased to sea how my French colleagues are now vigilant for dubious curves and how they're interested in solar effects on climate. I'm sure that beyond the polemic, they will from now on inform their readers on real climatic debates in a more balanced way.
Timothy Chase says:
raypierre (#25) wrote:
Swweeet!!
I had to run it through Google Translator, I'm afraid. (My apologies, but I took German due to Kant — and didn't do terribly well at that. Not that much point, I suppose: I am told that Kant gets taught in the English translation in Berlin — as he is more easily understood by native German speakers that way.)
While I am sure that more than little was lost in translation, it looked devastating, hitting a number of the major points — and your critique on Real Climate received a fair amount of space. They did far better job than I have come to expect from the US press — but then it would be quite a different world as of recent if the US press generally rose to the level of mere mediocre performance.
Incidentally, I enjoyed your critique. Quite thorough. And it gives us a bit more insight into the kind of politics which can get that sort of paper in print.
[Response: Without divulging any privileged information, I can say — as one who has himself had some experience as an editor — that another factor in such papers getting into print is that it is often hard to find qualified reviewers who are willing to take the time to delve into a paper like Courtillot's. Everybody has a lot of demands on their time, and it is much more productive to ones' research to spend time with good and interesting papers rather than bad ones, especially in view of the fact that there are so many of the latter. For every four papers like this that get stopped in review, one is bound to get by, just through exhaustion of the reviewer pool. Some editors are better than others at tapping into a pool of suitable reviewers, and it helps if a paper is bad in an interesting way, and is laid out so one can at least follow the argument. No reviewer is likely to go through the amount of work Bard and Delaygue had to do to dig out the flaws in Courtillot's paper, especially since work of that sort done at the review stage never sees the light of day. –raypierre]
I have been in communication with Rob van der Hilst, who is understandably more than a little unhappy about my commentary on the way he handled the Comment/Response to Courtillot et al. I somewhat regret bringing up the issue of possible problems with the EPSL editorial process at all, given that it is a side-show to the main issue at hand, which is exposing the nature of the arguments in Courtillot et al. However, I thought it necessary for the readers to know the full history of how the true data source for the supposed "Tglobe" came to be known, and of who first pointed out the problem with Courtillot's use of the Tobiska solar data series. I did not see any way to explain this without bringing Rob's name into it, given that he was the responsible editor and made all the decisions. I tried to present the sequence of events as best I could infer them from what appeared on the Elsevier web site, augmented by a few queries I put out (none of which went directly to Rob; remember I am a scientist, and not schooled in the reflexes every professional journalist has).
I invited Rob to give his view of the editorial process here, but he did not want to pursue it in this forum. In lieu of that, here is a second try by me, to present the basic facts of the matter in the most neutral possible manner, taking into account Rob's perception of what went on. I would be interested in what the readers make of this. In the same spirit, I emphasize that I stated Rob's professional connection with IPGP purely as a matter of relevant background information. I of course am not a mind reader, and can have no knowledge of what role this connection may or may not have played in the way Rob chose to handle this. So here goes:
As I stated originally, at the proof stage of their Comment, Bard and Delaygue had the opportunity to see Courtillot's Response. Noting the peculiarities in the Response regarding the solar and Tglobe dataset, they felt that in light of this new information an additional remark was called for, and for want of any other vehicle proposed handling it as a "Note added in Proof." This is quite standard editorial practice when there is a late-breaking development, and when such a note is added to a regular journal proof, the Editor generally has leeway to accept or deny the note. In this case, the Editor articulated the opinion that the Comment/Response cycle was closed and no further information should be introduced, and the Editor feels he exercised his Editorial discretion to deny the approval of the Note Added in Proof. Bard was left with a very different impression of the outcome, particularly in view of the fact that his Comment was posted on the Elsevier preprint section with the Note intact. As far as I can tell, there was no further communication with Bard and Delaygue concerning the matter until the final prepublication proofs were sent. When it came time for final publication, the Note had disappeared. I suppose Rob would say that he intended this all along, and that the appearance of the Note on the posted Preprint version was an oversight; I am only guessing about that, though. At some time before final publication, van der Hilst, having declined to exercise his editorial discretion to re-open the "closed" Comment/Response cycle when it came to Bard and Delaygue's "Note Added in Proof," decided to exercise his editorial discretion to the extent of re-opening the "closed" cycle in order to allow Courtillot to modify his Response so as to take into account the points raised by the Note Added in Proof.
So there they are, just the facts, Ma'am (as they used to say on Dragnet), in the most unvarnished way I know how to present them, and as best they can be known to me. I would be very interested in what conclusions the readers draw from this sequence of events, what may or may not have been lost by handling things this way, and how the readers feel the matter should have been handled, if they do not feel it was handled correctly.
Thanks for the great article. Indeed, I do find it very suspicious that you see the same names over and over, regurgetating the same nonsense over and over. Same stuff as well- water vapor, CO2 lag, 1940-70 cooling, MWP, ad nauseum. The number for S&W solar number keeps getting higher and higher, I'm sure we'll see a "70% solar contribution" in some 2010 paper, but who knows
One point that has been made on and off before, but needs to be repeated was the point on the concept that there is only one way to look at radiative forcings: the sum of them all. The scientific basis for anthropogenic climate change is there, but now we find some unknown forcing, or some forcing is a bit higher than we suspect, etc. You can't just now "replace CO2." The logic of "the sun is going up, so now we can have a picnic because there will be no problem or we can't do anything about it, and CO2 is falsified" is high level nonsense: I'd be much more worried if the sun is going up, and CO2 is going up. Heck, if Svensmark or Shaviv is right, Scafetta and West is right, the CO2 forcings are right, Courtillot is right, etc then we really are screwed!
I do need clarification on one point though. Say we have Total forcing represented by Ft which equals 10 W/m-2 (hereafter just the number), where F1 + F2 + F3 = Ft. Say we think F1 = 4, F2 = 11, and F3 = -5 (so 10). Now say that it turns out through further tests that F1 really equals 7, not 4. First of all, don't we know the "total" forcing, (that is we can quantify the radiative imbalance and tell you how much Ft is, like now it is ~1.6 W/m-2). So that means if a partial forcing goes up, doesn't another partial forcing need to go down (or throw in a negative F4)? Since we know Ft = 10 ( i.e. back to the real world, don't we know the imbalance is 1.6 W/m-2 now so dont all forcings need to add up to the imbalance?)
[Response: We have estimates of the imbalance through looking at heat storage in the ocean and looking at the surface energy budget, but I'll defer to Gavin on how accurate those estimates are. He was directly involved in that area. So far as I am aware, satellite data isn't yet accurate enough to detect the top-of-atmosphere imbalance, but somebody please correct me if there are new developments in this area. But the more important thing to note is that the imbalance is emphatically not the same as the radiative forcing. If you doubled CO2 and let the system come into equilibrium, the imbalance you'd measure from space would be zero — but there would still be about 4 W/m**2 of radiative forcing from the change in CO2. Radiative forcing is not a zero-sum game in the sense you laid it out, but it is fairly standard practice to use the observed temperature record to put some constraints on both climate sensitivity and the magnitude of unknown forcing. For example, we know the past CO2 radiative forcing to very high accuracy, but there are more uncertainties in the aerosol forcing; applying a consistent climate sensitivity to both CO2 and aerosols, you can get a match to the observed record for a range of different supposed aerosol forcings, but you can't take it too far. If you set the aerosol forcing to zero you don't get the mid-century interruption of warming, and if the aerosol forcing were allowed to get as big as, say, 10 W/m**2 you would get excessive cooling unless you imposed a very low climate sensitivity — which would then make it impossible to reproduce the post-1970's warming. You get the picture. Crowley's paper is a nice one to read to see how this is done, since it's done with an energy balance model where you can see the big picture without a lot of complications –raypierre]
I've had enough experience with the referee process not to believe for a nanosecond that the reason this paper was published was anything other than the name of the first author, pure and simple. I'm sorry, RayPierre, but I don't buy your argument. Editors are politicians, like it or not.
#29 response- Thanks, I'll look into it
things that are wrong, and things that seemingly have the intent to deceive makes their way into peer-review quite a bit (moreso the former, which is good). I am a bit disappointed in the peer-review process, actually, given the abundance of literature that RC and other places need to cover because of errors. I also don't think that the name of the guy was a significant part of Ray's argument, and you can focus on issues like the objection paper, as well as why Damon and Laut had to write a paper on "suspicious" papers.
Stuart Jensen says:
Whatever measures you adopt for tactical reasons, please never abandon the 10 foot baguette. ;)
Raypierre, I have also had a little recent experience with a bad paper that "slips through the cracks". A paper I reviewed had some very serious errors. I pointed these out and suggested a major revision, thinking (indeed hoping) that the paper would go away. Alas it did not, and the second draft was much improved, though still flawed. Again, I pointed out the flaws and made suggestions. Like a bad penny, it came back for a third revision, then a fourth. After several cycles of this, with the journal editor under significant pressure to publish from the authors and under deadline, I gave my final review, detailing the remaining errors, suggesting corrections (some quite involved), but not requiring further review. I was conflicted. I know the final paper will be quite flawed. It will present some interesting ideas from a different perspective than the community gets, though, and the final product will be much better than it started out. Perhaps I should have held firm against publication of a crappy paper, but one must make a judgement whether the modicum of good in a paper might outweigh the bad. I decided that my peers are big boys and girls and will be able to sort out the good from the bad.
Perhaps Rob made a similar judgement, and I'm certain he is chagrined to find this playing out on the pages of the French media. Unfortunately, however, I think he was in a no-win situation. Had he rejected the paper or had he allowed the Note, he would have been accused by denialists of "being part of the conspiracy," and that would have played out on the pages of the National Post, the WSJ and other contrarian rags (remember Benny Peiser's ill-fated "rebuttal" to Oreskes's work). I suspect that editors face considerable pressure to allow into print the work of contrarians unless it is beyond all redemption. So crap gets into print precisely because contrarians demand a voice and all there is to publish, once you remove all the real climate science, is crap.
Denis Delbecq says:
Hello, and thanks Ray for this interesting saga on aour french climate-skepticals. I just updated my website to signal that two major daily newspaper in France have published article yesterday on this story. Here are the links for french speaking people…
On Liberation, http://www.liberation.fr/transversales/futur/298894.FR.php
On Le Monde, http://www.lemonde.fr/web/article/0,1-0@2-3244,36-991405@51-853716,0.html
Lynn Vincentnathan says:
#11 and "Civilization may fall anyway well before 2050, but we can avoid going extinct by 2100." I read SIX DEGREES last summer, and from what I recall, Lynas did not imply this. His idea (as I remember it) was that we would likely COMMIT the world to great harm (as 55 or 251 mya) if we reached 3C warming, in that slow positive feedbacks would eventually push us to 4C, then 5C & 6C. However the harms would take a long time (centuries, perhaps millennia) to completely play out, even after reaching 6C. More like bleeding to death from a thousand small wounds than a sudden (within this century) total wipe-out.
And I think Ray is right, that no matter how bad it gets, we could still lessen the harm, or slow its realization.
a mathematician says:
"At some time before final publication, van der Hilst, having declined to exercise his editorial discretion to re-open the "closed" Comment/Response cycle when it came to Bard and Delaygue's "Note Added in Proof," decided to exercise his editorial discretion to the extent of re-opening the "closed" cycle in order to allow Courtillot to modify his Response so as to take into account the points raised by the Note Added in Proof."
this is a clear-cut case of editorial misconduct. It has happened to me too
in this particular way with the addition that after the comment/response
cycle was closed our refereed reply was shown to the commenter who
was then allowed to modify the comment which was subsequently (re-)accepted
with no further review. At that point we threatened to sue the editorial
board (the comment touched on being libellous as we were advised by an
in-house lawyer). After the threat we got a letter from the editor that
stated the commenter had withdrawn the comment after considering our
reply. We let the matter end there, although we have the editor
admitting on letter-head to a violation of the editorial policy that governs
commets/replies. Go figure.
Eduardo Zorita says:
Courtillot also cites an atmosphere-ocean model simulation by Zorita et al. (2004) as support for his claim that models fail to represent the 20th century response to solar or magnetic variability. However, as discussed here and in the peer-reviewed references cited therein, this simulation suffers from an inappropriate initialization which leads to a spurious cooling in parts of the run, and a large climate drift requiring detrending of the output before analysis. Besides that, the model explicitly neglects anthopogenic aerosol forcing, so how could one expect it to get 20th century climate right?
Dear Raypierre,
your and Courtillot's discussion of the Zorita et al (2004) simulation are inaccurate. Contrary to Courtillot et al (2007) the NH T trend simulated by the model in the 20th century does by no means differ from observations by a "factor of three", but rather is about 10% larger than in the observations. I do not know on which grounds Courtillot et al (2007) reach such conclusions.
Your are right when you state that that particular simulation was not driven by anthropogenic aerosols and therefore a match to observations should not be necessarily expected. However, the simulation does not show a "spurious drift" and the output does not need to be detrended at all. You have probably mixed up several things here: another, different and longer, simulation with the same model – which actually your link refers to; the issue of detrending or not detrending in the context of climate reconstructions; and the issue of the use of flux-adjustment (the output of some models that do not use it may display a spurious climate drift – our model is however flux-adjusted).
Unfortunately the Courtillot et al paper and this part of your post can be quite confusing to the readers in this respect
[Response: Thanks for the clarification. I read your paper (which had some very interesting points, by the way) and from the description there it looked to me like the simulation was the same one as we discussed previously on RC. You're the one who knows for sure, though, so I'll defer to you on that. Given the number of papers I needed to read in order to check the claims made in Courtillot et al., I was not able to spend as much time with each one as I would have liked. I will point out that with regard to the claims made by Courtillot regarding your results, flux adjustment introduces similar issues to detrending. These issues are not necessarily important for the things you were trying to do with the model, but they are relevant to the way Courtillot was trying to spin the results. –raypierre]
Gavin, Ray, anybody,
I've written a popular article on the saturation argument. It's got some math in it, but nothing harder than algebra. About 2400 words. Can you think of any place that would take something like this? I emailed Physics Today, but they never replied.
[Response: You might try American Scientist, which is the house magazine of the scientific honor society, Sigma Xi. –raypierre]
darrel says:
Raypierre and also Chris (comment 29) noted that "sceptics" should not just magically forget about or omit the established greenhouse gas physics when trumpeting exotic solar explanations for current warming. But as far as I can tell, most sceptics don't flat out deny greenhouse gas warming, but they incorporate their "extra" forcing by assuming a lower climate sensitivity. That way they don't have to completely deny basic physics, and they throw the exotic stuff in by using the relative uncertainty of climate sensitivity as a free parameter so to speak. By doing so they may actually deny the constraints that there are on sensitivity, that I'm not sure about.
FWIW, journal editors have the role of bringing the maximum information to the readers not acting as judges between the parties with the sole and vital exception that they must make an editorial decision that the the correction is worthy of consideration. It is all to easy in a controversy to try and cut it off (which is the mistake that the editor here made), but I see nothing wrong with showing the information to the original authors for their comments. There is no "deadline to meet" and the process takes as long as it takes. That does not mean that when one of the parties starts sprouting nonsense the editor cannot rule the nonsense offsides, or cut off the process when no new information is being added.
I have been on both sides of this, and consider myself fortunate in the editors that handled the situations. I have, through the guidance of those editors, learned a lot about these situations. A word of advice to those submitting comments – keep it short, only comment on things you definitely can prove.
Jack Roesler says:
#24, SecularAnimist: Here's another company in the thin film solar panel business that's just getting started. They expect to be selling their panels for about a dollar a watt also.
http://www.toledoblade.com/apps/pbcs.dll/article?AID=/20071219/BUSINESS03/712190411
I think it's pretty interesting that just today, Pres. Bush said that nuclear is the "best" way to combat global warming. Oh well.
My Repulican friends couldn't wait to inform me of the Senate report just posted to Imhof's Press blog:
http://epw.senate.gov/public/index.cfm?FuseAction=Minority.Blogs
If anyone ever needed a complete guide to the "scientific Denialist's", this report should do it.
The authors of the paper under discussion are prominently featured.
[Response: Yeah, this is pretty much a non-story. All you have to do is look at the names and some of the creative accounting used to bulk up the list. For example, they've added pretty much all of the names of Lomborg's "Copenhagen consensus," even though most arent' scientists. Then, there's the trick of including, say, all the co-authors of the Courtillot article, even though some of them (like Fluteau) certainly would not describe themselves as skeptics. There is Avery, with his "unstoppable global warming" nonsense (and no peer-reviewed scientific publications). There are a few real scientists, like Allegre and Courtillot ('nuff said about that), plus a lot of nonentities whose lack of credentials you can spot just by running their names through Web of Science. If this is the best 400 names that Inhofe can scrape together, then the denialist crowd is really in bad shape. I don't think it needs any more comment than that. –raypierre]
Raypierre, re. 29 "We have estimates of the imbalance (energy) …looking at the surface energy budget,"
For determining surface energy budget, do you mean by measuring borehole evidence or other means?
http://www.sciencemag.org/cgi/content/full/297/5579/206?ck=nck&ijkey=TgKv6oKI2SgcE&keytype=ref&siteid=sci
[Response: No, for long term heat storage it's only the sea surface that counts. What I had in mind were estimates of net surface imbalance using boundary layer models driven by meteorological observations. –raypierre]
Deech56 says:
RE #42 Paul Middents:
Yeah that tidbit was brought to my attention as well. It is on today's Drudge Report. Everything in one overwhelming re-package. BTW, the paper under question is exactly the kind of item that will be brought up again and again to show that there is still a scientific controversy. Excellent critique, Raypierre, and thanks for all the dispatches from San Fran.
Chuck Booth says:
A bit off topic for this thread, but certainly relevant to RC:
Here's an clever approach to getting people to think about AGW and its consequences:
http://www.switched.com/2007/12/19/high-school-teachers-global-warming-video-a-youtube-hit/
Of course, he probably won't change the minds of many die-hard skeptics, as is evident from the comments listed below the video window.
Francis Albarede says:
Editorial Handling of Comments and Replies
However necessary, a Comment and Reply procedure always demonstrates a failure of the publication system: noble material appears in full-blown regular papers. During 11 years of editorial tenure in major geophysics journals, I always agonized about how Comments and Replies should be handled, especially when one of the parties is as prejudiced as in the present case. I stick to two principles: (1) the Comment and Reply exchange thread can't go on forever, and (2) the defense (Replyer) should have the last word and not be opposed arguments that they can't respond to. Clearly these principles are a potential source of frustration for the Commenter when the Replyer's good faith is an issue. Finding editors of high stature is already a very difficul task but if you now hold them liable for all the mistakes, lapses, and twists slipping into each manuscript, this task will soon prove impossible.
[Response: Very true words,and indeed an Editor is in a bind when one of the parties (the Reply party, in this case) is acting in bad faith. If I have some complaint about the way the Editor handled this, it is that to me the way out of the dilemma was much more indulgent to the bad-actor (Courtillot) than to the white-knight who put in the work to dig out the errors. Further, it was surely relevant information that in the initial Reply, Courtillot attempted to deceive yet again, by giving the name of a purportedly global dataset that turned out not to exist, and was certainly not the one used by the authors. It was only on the second attempt that the name of the real data (which turned out to be neither global nor annual) came out. Surely this history is relevant information, which should have been preserved. In fact, it was preserved, but only because, by luck, I happened to be writing my post based on the earlier version of Bard and Delaygue's comment, before the Note was deleted and Courtillot's Reply was modified. In the end, some critical information did get out, but if it werent for these fortuitous circumstances, some critical information would have been lost as well. –raypierre]
I have no envy for editors, and I am sure it takes herculean strength to resist the arm-twisting they're subjected to, but time and again one sees that
(1) Progressive, unconventional ideas from young researchers are biased against,
(2) Regressive, outdated ideas from old farts who should just get out of the way, are biased for.
In other words, scientists are actually phenomenally conservative; something the right wing clearly just doesn't get.
You can still find papers being published from time to time on non-cosmological redshifts of quasars, for example, which is total nonsense, but it is a regressive idea held onto by old cranks who don't believe in general relativity and have names big enough to get their ideas to press.
The whole peer-review system is a mess. The public thinks that being peer-reviewed is a stamp of approval, which it isn't, and editors themselves aren't clear on precisely what refereeing/editing is supposed to accomplish. Last time I looked, the major astrophysics journals did not publish any basic position statements on what, exactly, being approved for publication was supposed to significate. So how is the public supposed to figure it out if the scientists themselves don't even know? I'd love to hear it if the situation were different in geophysics.
[Response: I wouldn't go so far as to say that it's a mess, but I do think that it is overloaded. The journal Atmospheric Chemistry and Physics has an interesting new angle on this. Reviews are anonymous, but they are posted for the public. In addition, the general readership can post comments and suggestions on a preprint, just as on a blog. As I see it, though, the main problem is that people are writing too many papers, many of which are just not that significant. Everything would work more smoothly if more people held their fire until they had something fairly important to say. Unfortunately, a lot of the reward structure is not set up to foster that. –raypierre]
Pascal Y. says:
Thank you for your post and clarification. I completely agree with what you wrote (and also with Bard & Delaygue's paper…).
Just to add my grain of salt, I recently (i.e. before your posts) had a conversation with somebody at IPGP who explained me the context of Courtillot et al.'s EPSL paper:
In 2003, Gallet and others (incl. Courtillot) published in EPSL a study on paleomagnetism from archeologic data over the last 3 millennia. Le Mouel, Kossobokov and Courtillot published a paper in EPSL in 2005 on the magnetic field and climate. For some reason Courtillot wanted to paste the two papers together, hence the list of authors. The latter 2005 paper made (admittedly too little) noise in the climate science community. But nobody, including Edouard Bard, seem to have had the time to respond to the paper. I just remember that I was extremely perturbed by the abundant use of the adjective "significant" in the text, while no real quantification of this signifiance was provided. The other thing that should strike any non specialist is that temperature (whatever its true reference!) always leads the solar and geomagnetic data by a few years… oh well, I just told to myself that the paper would not take long to be forgotten…
So, it appears that the present controversy originates from the 2005
EPSL paper. In the unlikely event that the 2007 paper is withdrawn or whatever, there remains the 2005 paper, which everybody seem to have forgotten and contains the very same flaws outlined by Raypierre, and Bard and Delaygue in the 2007 paper. Incidentally, this also says that Courtillot never cared to improve his physics of climate between 2005 and 2007.
To conclude, with colleagues, we had thought of nominating Allègre and Courtillot for an Ignobel award (say, in the climate nonscience
category), but it turns that the Ignobel awards are given to true
results (albeit strange!) and they probably would not be qualified.
Best to all and joyeuses fêtes,
[Response: The remark about the 2005 paper raises another troubling question about the 2007 Courtillot et al paper — As far as I can tell, there is little if anything new in this paper beyond what has been published by the authors in the authors' previous works. In essence it is a review article, not a research article. Yet, it does not appear to be one of the invited EPSL "Frontiers" reviews. Does EPSL now publish unsolicited submitted review articles? I wasn't aware that it did. So how did it happen that this paper was even allowed to enter the review process, let alone survive it? Curioser and curioser. (et joyeuses fêtes!) –raypierre]
To #47
To paraphrase Churchill, peer review is the worst form of editorial handling except all the others that have been tried. We can also joke about either old farts resisting change (fair enough) or that younger ones see themselselves as creative because they never read anything more than 5 years old (equally true). Junior and senior scientits having a different perception of science is a good thing after all: energy arises from differences in potential. The science you inherit today was left to you by this less than perfect system. We all fell victim to abusive or incompetent reviewers. Good reviewers (and editors) are rare and overtaxed. I fear, however, that if they know their reports will posted, many of them simply will decline the review. Don't throw out the baby with the bath water!
Francis Albarede, A very thoughtful post. The thing is that peer review typically serves many functions. Yes, it should serve as a barrier preventing very bad science from seeing the light of day, but more commonly its role is to take decent science and push it into the realm of good science. Often, peer review is problematic for either really great or really bad papers. In the former case, the author may be saddled with lots of trivial changes, or worse yet be asked to make changes that weaken the paper. And in the case of very bad papers, the sheer persistence of an author can result in the paper tunneling through even if it is deeply flawed. Fortunately, science is strong enough to deal with these failings–enough scientists will recognize great work once it is published to ensure it is incorporated, and crappy papers usually get the obscurity they richly deserve (it's a lot harder to tunnel your way to general acceptance than it is to tunnel through the review process).
The main problem comes when you bring in the lay public or reporters, who often are not sophisticated enough to separate the wheat from the chaff and who often uncritically accept peer review as a seal of approval by the scientific community. People need to understand–peer review is a minimum threshold. The real stamp of approval is scientific consensus.


text:
Most celebrated edtech startup Byju's raises funds from Tencent
Harsh Upadhyay
India's leading edtech startup Byju's has bagged a new round of funding from Chinese internet major Tencent Holdings Limited.
Backed by Mark Zuckerberg and Sequoia, a $670 million valued Byju's will accelerate product development for new markets and enable inorganic growth through acquisitions with the latest funding.
The development was first published by Economic Times.
"This makes our strong investor portfolio even more diverse. At Byju's, we have been fortunate to have investors who have always played a crucial role as partners in our growth story. With increased brand awareness and strong adoption amongst students, this year we expect the revenue to double again and we will be profitable on a full year basis," said Byju Raveendran, founder of Byju's.
Founded in 2011, Byju's has a footprint in the Middle East and is looking to expand its horizon to US, the UK, South Africa and other African and Commonwealth markets.
The largest funded edtech startup in India, Byju's has about 8 million users and 400K annual paid subscribers. Through its flagship product-Byju's-The learning app, it offers learning programmes for class 4-12 & test preparation for JEE, AIPMT, CAT, IAS, GRE & GMAT.
Bengaluru-based Byju's, which has recently acquired global education company TutorVista and Edurite for an undisclosed amount, had raised funding from the likes of Chan Zuckerberg Initiative (founded by Mark Zuckerberg and Dr. Priscilla Chan), Sequoia Capital, Sofina, Lightspeed Ventures, Aarin Capital and Times Internet. Brussels-based Verlinvest is the latest who infused $30 million in it.
Byju's claimed to clock a revenue of around Rs 4 crore in FY12, Rs 12 crore in FY13, Rs 20 crore in FY14, Rs 48 crore in FY15, and Rs 120 crores in FY16 and expects to grow at the rate of 2.5X in 2017.
As per Google's and KPMG report, India's online education industry is expected to grow almost eight times to hit $1.96 billion by 2021, with the number of paid users rising six-fold from 1.6 million now to 9.6 million.
Tencent which already had invested in Indian start-ups like Flipkart, Practo and Hike, its foray in Indian edtech startup can be seen as a sign of growth.
In April, Mumbai-based Toppr, raised Rs 2.16 crore (around $336,000) in a bridge round. Earlier, another startup Cuemath, raised Rs 102 crore in Series B funding from CapitalG and existing investor Sequoia India.
Byju Raveendran, Byju's, Tencent Holdings Limited
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redpajama_set_name: RedPajamaCommonCrawl


text:
Classical and Bayesian methods of estimation for power Lindley distribution with application to waiting time data
Sharma, Vikas Kumar;Singh, Sanjay Kumar;Singh, Umesh 193
https://doi.org/10.5351/CSAM.2017.24.3.193 PDF KSCI
The power Lindley distribution with some of its properties is considered in this article. Maximum likelihood, least squares, maximum product spacings, and Bayes estimators are proposed to estimate all the unknown parameters of the power Lindley distribution. Lindley's approximation and Markov chain Monte Carlo techniques are utilized for Bayesian calculations since posterior distribution cannot be reduced to standard distribution. The performances of the proposed estimators are compared based on simulated samples. The waiting times of research articles to be accepted in statistical journals are fitted to the power Lindley distribution with other competing distributions. Chi-square statistic, Kolmogorov-Smirnov statistic, Akaike information criterion and Bayesian information criterion are used to access goodness-of-fit. It was found that the power Lindley distribution gives a better fit for the data than other distributions.
Consideration of a structural-change point in the chain-ladder method
Kwon, Hyuk Sung;Vu, Uy Quoc 211
The chain-ladder method, for which run-off data is employed is popularly used in the rate-adjustment and loss-reserving practices of non-life-insurance and health-insurance companies. The method is applicable when the underlying assumption of a consistent development pattern is in regards to a cumulative loss payment after the occurrence of an insurance event. In this study, a modified chain-ladder algorithm is proposed for when the assumption is considered to be only partially appropriate for the given run-off data. The concept of a structural-change point in the run-off data and its reflection in the estimation of unpaid loss amounts are discussed with numerical illustrations. Experience data from private health insurance coverage in Korea were analyzed based on the suggested method. The performance in estimation of loss reserve was also compared with traditional approaches. We present evidence in this paper that shows that a reflection of a structural-change point in the chain-ladder method can improve the risk management of the relevant insurance products. The suggested method is expected to be utilized easily in actuarial practice as the algorithm is straightforward.
Inverted exponentiated Weibull distribution with applications to lifetime data
Lee, Seunghyung;Noh, Yunhwan;Chung, Younshik 227
In this paper, we introduce the inverted exponentiated Weibull (IEW) distribution which contains exponentiated inverted Weibull distribution, inverse Weibull (IW) distribution, and inverted exponentiated distribution as submodels. The proposed distribution is obtained by the inverse form of the exponentiated Weibull distribution. In particular, we explain that the proposed distribution can be interpreted by Marshall and Olkin's book (Lifetime Distributions: Structure of Non-parametric, Semiparametric, and Parametric Families, 2007, Springer) idea. We derive the cumulative distribution function and hazard function and calculate expression for its moment. The hazard function of the IEW distribution can be decreasing, increasing or bathtub-shaped. The maximum likelihood estimation (MLE) is obtained. Then we show the existence and uniqueness of MLE. We can also obtain the Bayesian estimation by using the Gibbs sampler with the Metropolis-Hastings algorithm. We also give applications with a simulated data set and two real data set to show the flexibility of the IEW distribution. Finally, conclusions are mentioned.
Using ranked auxiliary covariate as a more efficient sampling design for ANCOVA model: analysis of a psychological intervention to buttress resilience
Jabrah, Rajai;Samawi, Hani M.;Vogel, Robert;Rochani, Haresh D.;Linder, Daniel F.;Klibert, Jeff 241
Drawing a sample can be costly or time consuming in some studies. However, it may be possible to rank the sampling units according to some baseline auxiliary covariates, which are easily obtainable, and/or cost efficient. Ranked set sampling (RSS) is a method to achieve this goal. In this paper, we propose a modified approach of the RSS method to allocate units into an experimental study that compares L groups. Computer simulation estimates the empirical nominal values and the empirical power values for the test procedure of comparing L different groups using modified RSS based on the regression approach in analysis of covariance (ANCOVA) models. A comparison to simple random sampling (SRS) is made to demonstrate efficiency. The results indicate that the required sample sizes for a given precision are smaller under RSS than under SRS. The modified RSS protocol was applied to an experimental study. The experimental study was designed to obtain a better understanding of the pathways by which positive experiences (i.e., goal completion) contribute to higher levels of happiness, well-being, and life satisfaction. The use of the RSS method resulted in a cost reduction associated with smaller sample size without losing the precision of the analysis.
Multivariate analysis of longitudinal surveys for population median
Priyanka, Kumari;Mittal, Richa 255
This article explores the analysis of longitudinal surveys in which same units are investigated on several occasions. Multivariate exponential ratio type estimator has been proposed for the estimation of the finite population median at the current occasion in two occasion longitudinal surveys. Information on several additional auxiliary variables, which are stable over time and readily available on both the occasions, has been utilized. Properties of the proposed multivariate estimator, including the optimum replacement strategy, are presented. The proposed multivariate estimator is compared with the sample median estimator when there is no matching from a previous occasion and with the exponential ratio type estimator in successive sampling when information is available on only one additional auxiliary variable. The merits of the proposed estimator are justified by empirical interpretations and validated by a simulation study with the help of some natural populations.
Bivariate odd-log-logistic-Weibull regression model for oral health-related quality of life
Cruz, Jose N. da;Ortega, Edwin M.M.;Cordeiro, Gauss M.;Suzuki, Adriano K.;Mialhe, Fabio L. 271
We study a bivariate response regression model with arbitrary marginal distributions and joint distributions using Frank and Clayton's families of copulas. The proposed model is used for fitting dependent bivariate data with explanatory variables using the log-odd log-logistic Weibull distribution. We consider likelihood inferential procedures based on constrained parameters. For different parameter settings and sample sizes, various simulation studies are performed and compared to the performance of the bivariate odd-log-logistic-Weibull regression model. Sensitivity analysis methods (such as local and total influence) are investigated under three perturbation schemes. The methodology is illustrated in a study to assess changes on schoolchildren's oral health-related quality of life (OHRQoL) in a follow-up exam after three years and to evaluate the impact of caries incidence on the OHRQoL of adolescents.
The restricted maximum likelihood estimation of a censored regression model
Lee, Seung-Chun 291
It is well known in a small sample that the maximum likelihood (ML) approach for variance components in the general linear model yields estimates that are biased downward. The ML estimate of residual variance tends to be downwardly biased. The underestimation of residual variance, which has implications for the estimation of marginal effects and asymptotic standard error of estimates, seems to be more serious in some limited dependent variable models, as shown by some researchers. An alternative frequentist's approach may be restricted or residual maximum likelihood (REML), which accounts for the loss in degrees of freedom and gives an unbiased estimate of residual variance. In this situation, the REML estimator is derived in a censored regression model. A small sample the REML is shown to provide proper inference on regression coefficients.
Intensive numerical studies of optimal sufficient dimension reduction with singularity
Yoo, Jae Keun;Gwak, Da-Hae;Kim, Min-Sun 303
Yoo (2015, Statistics and Probability Letters, 99, 109-113) derives theoretical results in an optimal sufficient dimension reduction with singular inner-product matrix. The results are promising, but Yoo (2015) only presents one simulation study. So, an evaluation of its practical usefulness is necessary based on numerical studies. This paper studies the asymptotic behaviors of Yoo (2015) through various simulation models and presents a real data example that focuses on ordinary least squares. Intensive numerical studies show that the $x^2$ test by Yoo (2015) outperforms the existing optimal sufficient dimension reduction method. The basis estimation by the former can be theoretically sub-optimal; however, there are no notable differences from that by the latter. This investigation confirms the practical usefulness of Yoo (2015).
A cautionary note on the use of Cook's distance
Kim, Myung Geun 317
An influence measure known as Cook's distance has been used for judging the influence of each observation on the least squares estimate of the parameter vector. The distance does not reflect the distributional property of the change in the least squares estimator of the regression coefficients due to case deletions: the distribution has a covariance matrix of rank one and thus it has a support set determined by a line in the multidimensional Euclidean space. As a result, the use of Cook's distance may fail to correctly provide information about influential observations, and we study some reasons for the failure. Three illustrative examples will be provided, in which the use of Cook's distance fails to give the right information about influential observations or it provides the right information about the most influential observation. We will seek some reasons for the wrong or right provision of information.