Arguments
Michael Mann, hounded researcher
Posted on 30 December 2011 by Andy Skuce
Here is a translation of recent article (December 25th, 2011) in the French newspaper Le Monde by science journalist Stéphane Foucart. He reports on a talk that Michael Mann gave at the 2011 AGU Fall Meeting in San Francisco, in which Mann introduces his forthcoming book The Hockey Stick and the Climate Wars: Dispatches from the Front Lines. Foucart interviews Mann and discusses the background of the Hockey Stick and Climategate controversies. What is refreshing is the absence of the false balance, both-sides-of-the-story, style of reporting that is found so often in English language newspapers.
Original article (in French) from Le Monde
In early December, at the Fall Meeting of the American Geophysical Union (the annual grand gathering of the bigwigs of the geoscience world), Michael Mann introduced his forthcoming book to his peers. The lecture was entertaining and the audience laughed heartily. The American climatologist, Director of the Earth System Center at Pennsylvania State University, cracked numerous jokes and made many witty asides. He scoffed at the anti-science of the Republican politicians and mocked their ridiculous statements on climate change; everybody laughed out loud.
But this, surely, is no laughing matter. Michael Mann’s forthcoming book, The Hockey Stick and the Climate Wars: Dispatches from the Front Lines (Columbia University Press), is not really a science book; rather, as its title suggests, it deals instead with the war on climate science, which has at times turned into a manhunt, frequently with Mann as the quarry.
Lively, talkative and likeable, passionate about his research, Michael Mann is Conservative America’s most hated scientist. His crime is defined by two words, Hockey Stick, the nickname given to a curve showing how temperature has changed; a diagram that he will now forever be associated with.
In 1998, and again in 1999, with co-authors Raymond Bradley and Malcolm Hughes, he published a “reconstruction” of Northern Hemisphere temperatures, from the year 1000 to the present day. Using the traces of past climates recorded in tree rings, corals and sediments, he succeeded in producing a striking curve in the shape of a hockey stick. The long handle shows a fairly regular decline in temperatures from 1000 to around 1900, whereas the blade displays a sudden and a rather worrying sharp upward increase that is very obvious since 1950. The main conclusion of the Hockey Stick is that the last decade of the twentieth century was probably the warmest in over a thousand years.
“The irony is that I wasn’t originally working on anthropogenic climate change but on natural climate oscillations”, says Michael Mann. “I wasn’t looking for a hockey stick; it simply emerged from the data!”
The curve was given pride of place in 2001, in the Third Assessment Report of the Intergovernmental Panel on Climate Change (IPCC). It provided a striking visual image of the climate emergency. It became a symbol, and consequently, for all climate skeptics, an icon to destroy.
There began, at the beginning of the past decade, “an intense campaign of defamation, essentially financed by industry”, according to Mann. A statistician—also a consultant for the fossil fuel industry—disputed the data processing that produced the famous curve. The basic data themselves were subsequently put under suspicion and soon Mann was accused of having deliberately manipulated them. The Internet became awash with all kinds of myths linked to the Hockey Stick, urban legends that are occasionally passed on by scientists misled by the technicality of the arguments put forward. It is impossible today to Google the term Hockey Stick without finding hundreds of pages that detail alleged frauds, intentional errors and manipulations attributed to its creator.
The campaign worked wonderfully. In 2006, an American Congressman asked mathematician Edward Wegman (George Mason University) to prepare a report on the famous curve. The “Wegman Report” piled on with more criticism of the Hockey Stick. The American National Academy of Sciences was soon put to work to produce a report on the Hockey Stick, but they didn’t find much to complain about. “There was a legitimate technical discussion on the statistical method used in the data processing”, said Pascal Yiou (with France’s Climate Science and Environment Laboratory), “but others have processed the same data with different methods and that didn’t change the shape of the curve”.
Above all, as the controversy was artificially kept alive on the Net, a dozen other temperature reconstructions reached the same general conclusions as the original Hockey Stick.
The attacks were not just restricted to the iconic curve, however. Its author also was personally targeted. At the end of 2009, his emails—along with those of a number of other climatologists— were pirated and published on the Web. Most of the sentences, taken out of context, suggested collusion. A Republican Senator called for an enquiry into several researchers, Michael Mann first among them. The Attorney General for Virginia demanded that Mann’s Alma Mater, the University of Virginia, hand over all documents relating to him, including his archived emails, to search for possible evidence of fraud. As for Pennsylvania State University, it was pressured in 2010 to open an investigation on Mann, but ended up exonerating him.
Michael Mann feels that things can get carried away at times. “One day, a year and a half ago, I received a letter with white powder inside it that looked like it could be anthrax. I forwarded the letter to the police who sent it for analysis: it turned out to be corn flour.” Since then, he won’t open letters unless he knows the sender.
How does anyone survive almost a decade of attacks and slander? “Getting caught in such storms isn’t something that scientific training prepares you for”, he says. “You have to become expert in defending yourself and dealing with misinformation and attacks. But I like a fight!” When the attacks started to focus on him, one of his mentors, the late Steve Schneider (Stanford University), suggested to him that if “they” were coming after him, it was because his work was important. “That was really something that helped me to have the courage to face all this”, he says.
What, ultimately, is the outcome of all this? He suddenly becomes less talkative. “Those who attack us have won in the sense that they have succeeded in delaying any action on global warming by ten, twenty, maybe thirty years,” he concedes with worry as he sees his country succumbing to anti-science. “Denying either anthropogenic climate change or evolution has become a condition of admission to the Republican Party. That’s something quite new and very scary”.
By Stéphane Foucart
(Translated by Andy S. Please note that the quotes attributed to Mann were translated back into English from the French version of his words as reported in Le Monde. They will not therefore correspond exactly to what he originally said.)
Further reading: additional translations of newspaper articles and commentary (in English) on the reporting of climate change controversies in the French press can be found here.
Details here.
I wouldn't be surprised if this event brings some noisy detractors out of the woodwork, so anyone who happens to be in this neck of the woods (or what passes for woods in SoCal) on Feb 15 should consider dropping by and giving Dr. Mann a show of support.
Thank you for the heads up on that! Tix purchased!
The Aquarium of the Pacific is just inside Dana Rohrabacher's Congressional district. Here is a video clip of Rohrabacher, in his full glory, questioning Dr. Richard Alley at a Congressional hearing.
(Warning: Secure all hot beverages before watching it!)
Rohrabacher, btw, is now serving in his 12th term, and IIRC has never had to sweat re-election. Keep that in mind as you watch the video.
There are lots of hard-core Rohrabacher supporters living pretty close to where Mann will be speaking, so heckling wouldn't be unexpected. In fact, given the political views of many in that area (especially to the south, in Orange County), there's the possibility of being treated to a bit of a right-wing "freak-show" outside the venue.
Folks attending might want to have their videocam/iphone/android devices handy. There's the potential of getting some very "YouTube worthy" video footage.
And therein lies the rub.
The Denialati have already won. It matters not to the eventual inevitable public vindication of the science, because the vested interests and the ideologues have achieved the delay they sought. And those ten to thirty years represent the difference between a relatively livable world to bequest to future generations, and one where the global indices of human suffering and of ecological integrity are seriously compromised.
It only remains to be seen by how much humanity intends to allow those indices to be seriously compromised.
That such politically-driven obfuscation of scientific fact can occur in both the USA and in Australia (amongst other countries) indicates a fundamental failing in both our societies. I suspect that as well as future generations cursing our current national propensities for overweening social self-indulgence, future historians will be less than complimentary about the decision-making processes of which we are apparently so proud.
It seems that in its capacity to achieve sensible conclusions, science has much to teach political democracy. This is reflected in the incredulity so many scientists experience when lay people accept the misrepresentation of solid work such as Mann's. It is telling that the situation appears to be different in France.
I suspect at least some amongst those aforementioned future generations would be less horrified, on reflection and with their benefit of hindsight, if Micro$oft Vista (another famously buggy operating system) had been introduced to the world in 2000 at the end of a gun...
If only it wasn't oxymoronic to introduce rational thinking to the US and Australia in the same way.
The irony is that he abandoned his main attack - on the formula - and by implication gave it a measure of approval. Indeed, if the flaw was in the formula there was no need for a decade of data attacks (his latest claim versus the hockey team is that they all use the same flawed data).
Mann's reconstruction has been wiggled and jiggled by subsequent independent lines of research ... but the observations and data match his thesis. And mock McIntyre.
Take taxation. During the decade long boom leading up to the GFC, governments should have taxed more. Its easy to see in hindsight, now that governments around the world find themselves with unsustainable levels of debt. But it should have been foreseeable, and politicians on both sides should have spurned tax cuts, arguing instead for caution. But if you want to win an election, you should promise tax cuts, and the media should cheer you on.
Its the same with global warming - its easy to be irresponsible and encourage people to deny that we have a problem. The Republicans in the US, and the Coalition in Australia have decided to play the populist card. The Murdoch media has gone along with this. It is annoying, to say the least.
While I find your observation about the change in McIntyre's focus interesting, I am skeptical of your suggestion about his being a 'hired gun'.
Yours is the first inference I've ever seen of the Fraser Institute (or any specific party) funding McIntyre directly. On the other hand, McKitrick's links to the think tank are public knowledge.
I appreciate SkS's avoidance of innuendo. It is all too easy (especially given the article's subject matter) to slip into bad habits.
Steve McIntyre was a hired gun out of the Fraser Institute; he packed a statistical toolkit to unravel formulas that produced an inevitable hockey blade - from any data.
(Disclaimer: The material below is a non-rigorous, "arm-wavy" attempt to explain in plain English to non-mathematical types, why the "Mann generates hockey sticks from any data" argument is bogus -- it is by no means a "proper and correct" explanation from a rigorous mathematical perspective.)
I should weigh in here, since I have some relevant experience with the SVD (Singular Value Decomposition) algorithm (the algorithm Mann used to "merge down" his North American tree-ring data). Although it is possible for Mann's SVD implementation to produce a "hockey-stick-shaped" leading principal component from random noise, no competent analyst would ever confuse such a "noise" hockey-stick with the genuine article.
When an SVD run produces a "hockey stick" leading principal component, the full SVD output will tell you two things about that "hockey-stick" leading principal component: its shape, and even more importantly, its *size*. Mann's method applied to tree-ring data produces a *big* hockey stick; if you get a hockey stick when you apply Mann's SVD to random noise, that hockey-stick will be tiny -- much smaller than the genuine Mann tree-ring hockey-stick.
To determine the hockey-stick "size" (aka magnitude), you need to look at the magnitude of the leading singular value. Each principal component aka singular vector has an associated singular value. The size of the singular value will tell you whether the associated principal component represents a "lot" of the data or just a "little" of the data.
If you look at the leading singular values for a bunch of "noise hockey-stick" runs, you will see that those leading singular values are *much* smaller than the singular value associated with Mann's tree-ring leading principal component.
If your SVD produces a small leading singular value, with the other singular values trailing off gradually in magnitude, then you will know that your data vectors are mostly uncorrelated with each other (i.e. they will have little or no "common temperature" signal). That's the signature of random noise.
OTOH, if your SVD produces a large leading singular value, with the remaining singular values decaying very quickly to near-zero magnitudes, you will know that your data vectors are highly correlated with each other, and most likely share strong common temperature signal. Can you guess what Mann's singular values looked like?
You can see a plot of the first ten (out of 70) of Mann's singular values here:
The blue circles represent the singular values (actually eigenvalues which are singular-values squared, but that doesn't matter here) generated by Mann's "short-centered" SVD procedure (the procedure skeptics claim produces hockey-sticks from noise). As you can see, the singular values decay (roll off) rapidly to near zero. Nearly all of the information in the tree-ring data set (70 tree-ring time-series) is captured by just the first three or so singular values. That's a good indication that the 70 tree-ring time-series in Mann's data set are highly correlated and thus share a strong common temperature signal.
Note: The singular values not plotted (singular values 11-70) are all *very* close to zero. If the above plot had shown all 70 singular values instead of the first 10, the "sharp roll-off" nature of Mann's tree-ring singular value spectrum would be even more obvious.
Some time ago, I experimented a bit with SciLab (scilab.org) and was able to generate my own "noise hockey sticks". But when I looked at my singular values, I found that those "noise hockey-stick" singular values looked *nothing* like Mann's tree-ring hockey-stick singular values. The leading singular value (associated with the "hockey-stick" leading principal component) generated from random noise was always very small (a small fraction of Mann's leading singular value), no matter how "hockey-stick-shaped" the leading principal component was. The remaining singular-values trailed off very slowly in size (producing a clear "random noise" singular-value signature).
The bottom line is, unless you look at the singular values, you can't say *anything* about your data. You can't simply look at the principal components (aka singular vectors) without considering the associated singular value magnitudes and draw any reasonable conclusions about whether your data vectors contain a "common signal" or are just random noise. Without the information provided by the singular values, you simply can't tell (no matter what your principal-components look like).
But that's exactly what skeptics did when they attacked Mann by claiming that his procedure generates hockey sticks from random noise. They never bothered to compare their "noise hockey stick" singular values with Mann's "tree-ring" singular values. Those of you out there who are familiar with the SVD and know how to interpret its output will fully appreciate what a spectacular blunder this is. Unfortunately, for most people, the SVD is obscure enough to them that they will never appreciate how stunningly incompetent the "Mann method generates hockey sticks from random noise" argument really is.
The bottom line is that Corbella’s slanderous statements and remarkable version of the ice core records were widely read in what are usually considered to be respectable newspapers. Both the Calgary Herald and the Vancouver Sun refused to publish any ‘letters to the editor’ that countered Corbella’s attack on Mann and I know that my letters were not the only responses that were submitted.
Especially incompetent in the face of all the other hockey sticks that are not from SVDs: atmospheric CO2, Arctic ice (blade is down), sea level (see the SkS graphics page for North Carolina), etc. It's one thing to incompetently say 'the hockey stick is generated from noise' -- its quite another to have to stick with that position over and over again.
But thanks for that lucid explanation of the Singular Value Decomposition (SVD). I've described it to my Linear Algebra classes as 'the best thing since sliced bread.' Should anyone want to try to see what they obtain from random noise, try this applet on an appropriately randomly seeded matrix.
I could not agree more. Bernard J’s “Denialati”, are winning the war whilst losing every battle. This side of the fence has to decide whether their welfare and that of their descendants is going to be best served by continuing to play 'Mr Nice Guy' and sticking rigidly to the science, or if the time has arrived for more direct action. Though the last thing I am suggesting is that sks should sink to the level one finds elsewhere on the climate issue. Perhaps a ‘direct action’ thread could suffice as a nucleus around which some form of organisation for direct action could grow.
The Occupy Wall St. Movement has gained a lot of publicity and not a small amount of public support for their unclear cause(s), yet Climate Change is about the possible deaths of countless numbers of our descendants, if not those of us still alive, and is surely a more deserving and clearer cause.
I have suggested before that there is soon to be an excellent opportunity to show the ‘retarded right’ how we feel about their contempt for the rest of us and our descendants. I make no apology for the repetition. The opening ceremony of the London Olympics next year will be performed mainly by the younger generation, who will be the ones most likely to suffer the privations that climate change will heap upon the planet. If those taking part could be encouraged to carry a placard demanding action on the topic, then at least we can be sure that they will be seen by countless millions. Any national committee that bans the action could be named and shamed. Perhaps even more dramatic action could be considered, such as a refusal to take part in the opening, which the national committees would be hard pressed to ban.
I honestly don’t think that the debate can keep plodding on while The Denialati keep managing to postpone action that is now so urgently needed (re the sudden release of methane in the Arctic as noted recently by Russian scientists, which, if it proves to be the long feared methane ‘burp’, then I guess it’s game over). The debate has now been going on for so long that all with an open mind will have made their mind up on the issue. By all means continue with the excellent scientific analysis, it is still important, if only to provide evidence in any future criminal proceedings regarding the actions of The Denialati. But the debate has to go up a gear if meaningful change is to happen and our descendants are not to be destined to a bleak and overheated future.
On the constructive (but unfortunately off-topic) side, I decided to learn a bit about Mars. I was hoping to find a sort of cryosphere today for martian polar ice cap area or extent, and then look at trends over time to see how well they match up with Earth's. Or to see at some point in the future when the trends diverge. No luck. Also there's a huge fluctuation in the CO2 content of the martian atmosphere (a bunch of the ice is frozen CO2) such that atmospheric pressure fluctuates by 25% over the year. I haven't yet found much written on the climatological impact of greenhouse gases there. But I think that would be interesting.
Can anyone elaborate on the industry finance? supply evidence? details? links?
Many of the think tanks that publish anti-climate change screed are financed by big oil and are staffed by people also on the boards of oil companies.
Exxon-Mobil
is a clear example. You can follow the trail from the think tanks E/M funds/has funded to blog sites like Junkscience.com (via the Cato Institute). Steve Milloy at that blog site and in his column in The Weekly Standardhas smeared plenty of climate scientists, including Michael Mann.
...Just checked in there, and there is a picture of a hockey stick right at the top with some a bumper sticker blurb on the parlous state of intellectual integrity in climate science. A quick search finds such gems as
http://junkscience.com/2011/12/06/steven-hayward-responds-to-mann/
But it's very easy to find links/details/evidence to this and many other examples with some ordinary search terms on google. So I wonder dawsonjg if your question was argumentative rather than genuine?
caerbannog, are the red crosses the singular values for McIntyre and McKittrik's own principle component analysis of the data from MBH 98 and 99?
The red crosses represent singular values when the data time-series are fully centered to zero-mean. The blue circles are the singular values generated via Mann's "short-centered" SVD implementation.
Mann's "short centering" (as opposed to full centering) prior to the SVD calculation was indeed a mistake -- but an inconsequential one.
The singular-value thresholding procedure (i.e. the algorithm that Mann used to decide which principal components to retain) ensures that the final results will be the same no matter which centering convention is used. See Mann et al. (or realclimate.org) for details.
Apply Mann's thresholding procedure to "short-centered" SVD outputs and it will give you the proper answer as to how many principal components to retain. Apply the same thresholding procedure to "full-centered" SVD outputs, and it will still give you the proper answer as to how many principal components to retain.
The bottom line is, no matter which centering convention you use, there is a *huge* (as in night vs. day) difference in the singular-value patterns for tree-ring data vs. random-noise data. Anyone who claims otherwise simply does not know what he/she is talking about.
But folks don't need to take my word for it -- there's lots of free software out there that allows you to "roll your own" random-noise hockey-sticks. Do that, compare your full-centered and short-centered random-noise singular values with Mann's tree-ring eigenvalues (both full- and short-centered), and you will see that it is slam-dunk easy to tell the difference between tree-ring data and random-noise data *simply by looking at the singular values*.
An excellent software package that has everything you need to do this is SciLab (www.scilab.org). It runs on Linux, OS-X, and Windows platforms. Easy to install, easy to run, not that hard to learn how to write your own script files.
Out of a bit of sloppiness, I used "singular values" and "eigenvalues" interchangeably in my above post. As far as Mann's application of the SVD procedure is concerned, they represent basically the same thing (eigenvalues are just singular-values squared).
would you then agree that M&M did make a consequential error by only including two principle components in their reanalysis of the MBH data?
Absolutely.
M&M failed to apply Mann's singular-value selection algorithm properly to the full-centered data. The fact that they blindly stuck with two principal components with the full-centered approach indicates that they didn't know what they were doing. Even a quick "eyball analysis" of the "full-centered" singular values would tell you (actually *scream* at you) to include more principal components.
There are lots of people out there who may be whizzes at crunching data with mathematical tools like matlab/scilab/R/etc., but that doesn't mean that they know how to interpret the results they get.
In addition, because of their focus on it, it's always topical. Whether it's Cuccinelli or AFP, the media plays as though some kind of trump card over the science could be found by someone digging through email. People who know anything about science know there is no such card. But when I talk to someone skeptical of science, and they refer vaguely to any number of supposed scandals involving Mann, I would like to know better than they do the history of the complaints they're trying to echo.
I would go look at McIntyre's website for a history, but there's a lot of chaff to separate and, besides,as @8 suggests, McIntyre's story has changed and he might not be reliable even at summarizing his own claims against Mann et al (both personal and statistical).
The fact is that McIntyre has cooperated with scientists who are both active in the campaign against climate science, and are known to have been funded by fossil fuel companies for activities undertaken in that regard. He has also attended and spoken at conferences organized by think tanks again known to be funded by fossil fuel interests. That makes him part of the industry funded campaign even though he is not paid by industry in that capacity. (He was paid by a fossil fuel company in a professional capacity up until 2003, but I know of no evidence to suggest he has been paid for his "work" at Climate Audit.)
What is more, McIntyre's claims have certainly been taken up and echoed around by industry funded individuals and organizations. That is all that is needed for Mann's specific claim to be true. His claim is, ergo, not defamatory for it is true. If you think it reflects poorly on McIntyre, well you are certainly welcome to that opinion.
McIntyre may very well have received stipends and travel expenses for speaking at climate denial conferences.
Hockey Stick
There were TWO congressional investigations, one at the request of Congressman Sherwood Boehlert(R) of the Science Committee. It was chaired by Professor Gerald North of Texas A&M. The report was critical of some of the methods used by Mann and his colleagues, but in the main supported the conclusions.
However, this report seems to have been deemed insufficiently critical in some quarters. A second Congressman, Joe Barton (R) of the Energy Committee requested another report, chaired by a group under Professor Edwward Wegman of George Mason University. The subsequent history of the Wegman Report is well known - the part of it published in Computational Statistics was subsequently withdrawn for plagiarism. Opinion is that it is a thinly-disguised rehash of McIntyre and McKittrick's earlier papers, leavened with material taken from Wikipedia (among other sources).
The Wegman Report went ahead over the objections of Congressman Boehlert who wrote to Barton that the second investigation was "misguided and illegitimate". Subsequently, Boehlert retired - after the Republican victory in 2010, the Science Committee of Congress was amalmagated with the Energy Committee under Congressman Barton. Joe Barton is notorious for apologising to BP for the obloquy the company received over the Gulf Oil spill.
How Congressional staffers, the Wall Street Journal, and Wegman collaborated to disseminate MacIntyre's ideas and morph him into a "science superstar" (to whom?) can be found on several blogs. Here is a good start:
Climate Science Watch
You are incorrect when you claim "McIntyre's work that discredited the hockey stick". Mann's work has been reproduced and validated by numerous independent groups. Mann himself has updated the original graph several times. McIntyre's work is the material that has not stood the test of time (see 27 in this thread).
Tom Curtis at 11:34 AM on 31 December, 2011
caerbannog @12, would you please write that comment up as an article that can be posted on SkS. Ideally you should have two versions.
Got a bit of a full plate right now, but will get started on putting together an article when I find some free time (hopefully within the next couple of weeks or so).
I think dawsonjg's comment is relevant to this thread in the sense that it is a great illustration of how some people are perfectly willing to denigrate Mann despite demonstrating that they know little or nothing about the science ...
McIntyre however does not move on, and nor do supporters - it seems pretty obvious why not to me.
There is no point coming over all coy and innocent. The corpse is on the floor, the blood is all over you and the knife is in your hands.
As demonstrated by Caerbannog above and elsewhere in this site, McIntyre's criticisms of Mann have been poorly grounded, false or based on invalid statistics. Despite that, they have resulted in endless accusations of fraud, death threats, two congressional ordered inquiries and endless efforts to defame Mann of which yours is just the latest.
[DB] It has been pointed out to you a number of times now that both Mann and the science have moved on, that the "hockey stick" has been replicated in multiple reconstructions and in virtually every single temperature series and metric. Now it is time to move this dialogue on; you beat a dead horse.
Overheated rhetoric snipped.
As you can see, there is far more agreement between MBH 99 and the other two reconstructions during the MWP than there is during the LIA. So while there is some justification for saying MBH 99 eliminated the LIA, there is no justification for saying it eliminated the MWP.
For completeness, some modern reconstructions (including the Mann 2008 EIV method) show MWP temperatures 0.3 degrees C warmer than those shown by MBH 99 (and Mann et al 2008 CPS method). The fact that the use of two different but justifiable methods on the same data can result in that 0.3 C difference shows that reconstructions in that era are uncertain. But 0.3 C above MBH 99 (0.2 C above the mid 20th century baseline) is still 0.3 C less than modern temperatures.
Finally, I am unimpressed by deniers saying that in order to move on we just need to accept unjustified slanders against Michael Mann. The story about how they first came for the Jews comes to mind. If we allow unjustified slanders to stand against Mann, and cut him loose; deniers will just turn to their next target.
Nor are we defending any "sainthood" of Mann. MBH 98 and 99 had flaws, as has been shown by genuine scientific critiques, including by Mann himself. But I am not going to let lies about him stand just for the convenience of deniers who continue to make accusations without substantive evidence.
What I continually point out is the fact that the "skeptics" of the hockey stick have never managed to produce a multi-proxy reconstruction that shows anything other than a hockey stick.
I promise, it was the champaign talking!
For the record, it is possible to use the CO2 content of the atmosphere as a a measure of globally integrated sea surface temperature so long as net emissions are not large (ie, prior to the preindustiral era). Therefore based on the approximately 12 ppm difference in CO2 concentration between the peak of the MWP and the Maunder Minimum, there was approximately a 1 degree C difference in temperature between those times. On that basis, Moberg 2005 is likely to be a more accurate reconstruction than either Mann 2008 EIV or Mann 2008 CPS (where EIV and CPS refer to different reconstruction methods applied to the same data). However, as the following chart shows, the difference between the methods is small:
Based on that estimate, Moberg 2005 and Ljungqvist 2010 are both reasonably accurate. Mann 2008 EIV probably slightly overestimates MWP temperatures and LIA temperatures. Mann 2008 CPS is probably closer than the EIV result for the MWP but overestimates LIA temperatures. None of these estimates are certain enough to be considered the last word, however, all of them show MWP temperatures lower than 21st century (and late 20th century) temperatures. Given margins of error, it is possible but improbable that individual decades in the MWP were warmer than the the first decade of the 21st century. It is slightly more probable, but not very that some individual years in the MWP where warmer than the warmest years of the late 20th and early 21st century (1998, 2005, 2007, and 2010).
Any further discussion should be here.