Questions for Marcott et al? – submit them here

Skiphil writes:

Andy Revkin of Dot Earth/NY Times blog is inviting questions to be submitted to the authors of Marcott et al. (2013). Since Revkin is one of the only journalists who might have a chance of getting the study authors to be responsive, this is a good opportunity.

Specifically, he’s asked for someone to prepare one list of questions which are “perceived as unanswered.”

Folks could start a list here at WUWT to post at Dot Earth, or simply post questions/points at Dot Earth until we have a good list.

submit questions on Marcott study to Dot Earth/NY Times blog

Andy Revkin Dot Earth blogger


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Was Michael Mann a reviewer of the manuscript ?


Why won’t Shakun and Marcott engage at ClimateAudit where there work is undergoing a detailed analysis? Why won’t they release their code?

Dear Sean, why on Earth did you listen to Mike?


My question for Marcott is was it worth it?
Marcott means corrupted. for ever more.

Anthony, I think somebody like AMAC or Brandon or Just the facts would be a good compiler of questions.

Tilo Reber

So Marcott is going to answer a question truthfully where the only true answer is, “I cheated to support AGW”. Don’t think so. But what and if he does answer should be entertaining. I think that these questions need to be very tightly structured, with exact references, so there is no way to sidestep the unjustifiable.

Steve McIntyre

I saw Revkin’s comment and will send in some questions, since Shakun hasnt answered points that interested me. The problem with a whole lot of people responding is that it gives Shakun an excuse to avoid my issues. I’ll take a look at what people propose, but would prefer that readers let me decide what to pursue. Thx, Steve Mc



Did any reviewer encourage or instruct the authors to re-date any of the modern proxy records with the intent of influencing principal components to produce hockey stick shapes?
Did you feel that any reviewer was insistent on producing a modern hockey stick as a condition of publishing? Do you have reason to believe this reviewer was Michael E. Mann?
Did any reviewer help produce the press release or otherwise suggest including the claim that modern warming rates were higher than past warming rates? Did this reviewer know that these claims were not robust?
Did you make any effort to temper claims that were not supported by the evidence before the press release was approved?


So It’s hot ea, tell me why is the Hawaii Islands out in the middle of the Pacific setting Cold records…
How about all that ice on hanging out around the south pole…
Oh well it’s weather not climate ea….


I’d recommend to stick to Judith Curry’s recommendation:
“Lets get to the bottom of this, but while doing so I remind you that one element of this is the struggle for the scientific souls of two promising young scientists. Please don’t overegg the pudding and inadvertently send them to the RealClimate refugee and training camp.”
I believe Steve McIntyre is the most qualified person of us all to ask questions and he can ask questions which really mater. Most other people here will just make things worse.


I think Steve Mosher has a good idea there. Get a group of knowledgeable statists, er statistatists, er statisticians, together, exchanging emails to submit legit questions. After answers are provided, at a later date release the e-mails the statisticians exchanged in choosing the questions. I call that taking the hi road. Also maybe not submit them under a name of anyone who must not be named. (;


Does not matter how the game was played…..just look at the scoreboard?

Lance Wallace

Posted this at Revkin’s blog:
In February 2011, Science magazine announced a new policy requiring authors to make their data and computer codes available to Science readers. Here is the relevant sentence:
“To address the growing complexity of data and analyses, Science is extending our data access requirement listed above to include computer codes involved in the creation or analysis of data.”
Have you made or will you make your code available?


“Thus, the 20th century portion of our paleotemperature stack is not statistically robust, cannot be considered representative of global temperature changes, and therefore is not the basis of any of our conclusion…”
Why did you elect to not exclude that period which was “not statistically robust” from the plot in order to preclude anybody from drawing any conclusions from them and would you have elected to omit it had that “not statistically robust” portion happened to have spiked downwards?

Dodgy Geezer

…one of the only journalists…
Er, ‘one of the FEW journalists’, or ‘the ONLY journalist’, perhaps?

son of mulder

Only technical questions that challenge the validity of their findings are worth asking. All science stands or falls based on the technical.

Firstly, I think it is a sound plan to compile questions here then let SteveM ask those he wants;
Secondly, having now actually heard the interview I thought the guy came over quite well, talk of his negative body language and other personal traits seem wide of the mark.
My specific points are these; talking about warming he says ( I paraphrase) ‘The rapid global change we’ve got now is unprecedented-it will cause a 4 degree C rise according to global emissions path.’
Well the change is NOT global and never has been despite the misleading statements by both the IPCC and the Met office. Various studies -including mine and Verity Jones- estimated that one third of the world is cooling, a figure confirmed by BEST (with caveats that no doubt Mosh will explain at some point).
One of those 30% is Britain which in some ways is fortunate (for others) as it has some of the finest and oldest instrumental and observational records in the world. The current decade long cooling in Britain is as rapid as was the warming, now sadly but a fond memory, as can be seen in the official Met office figures
CET has been shown to be a reasonable proxy for NH and global temperatures. As I demonstrated here in my own reconstruction to 1538, an upwards trend in temperatures can be noted as starting in 1690, which incidentally also shows the most rapid rise in the record. Whilst the Holocene generally may have been cooling for 8000 years, over the last 350 it has been warming (in fits and starts).
This demonstrates that the last part of the original hockey stick at least is tilted the wrong way-down instead of up. As a result the final uptick is grossly exaggerated, coming as it does from a much lower base than it should.
Now SteveM can pick what he wants out of that but certainly some of the basic propositions I heard in the interview need to be challenged

Steven Mosher says: April 6, 2013 at 9:41 pm
I think somebody like AMAC or Brandon or Just the facts would be a good compiler of questions.
I appreciate the thought, but I haven’t been paying much attention to the Marcott affair, McIntyre’s on it. I’ve been focused on building the WUWT Paleoclimate Reference Page.
I haven’t included Marcott et al. yet, but I am planning a crowdsourcing thread :

“in order to assess a number of the currently disputed, questionable and falsified graphs, including Briffa et al., 1998, Jones et al., 1998, Mann et al., 1998, Pollack et al., 1998, Jones et al., 1998, Mann et al., 1999, Mann et al., 2000, Briffa et al., 2001, Esper et al., 2002 and Jones and Mann 2004, AR4 section 2007 and Marcott et al. 2013.

Perhaps, once Steve has had an opportunity to get to the bottom of Marcott et al., we can have a crowdsourcing thread dedicated to Marcott. The thread would help to capture all of the facts in one place and help determine an appropriate label/treatment for Marcott et al. on the WUWT Paleoclimate Reference page. Today I created a new section at the bottom of the page for Incorrect/Falsified Graphs. It already has one resident, but there’s plenty of room for more…


Steven Mosher says: “haha.. I came to post this”
Haha, indeed! I loved Susan Anderson’s marvellous Freudian slip.


Why on earth would so called scientists not communicate directly with Steve at CA one of the best science blogs on the net ?

Andrew Harding

If CO2 increases from 0.0032% to 0.004% of the Earth’s atmosphere (of which only a small percentage is man-made) how can this tiny amount cause the doomsday scenario that we are continually told will happen?
Why have none of the predicted climate disasters happened yet?
Why have we experienced a succession of cold winters in the UK, when we were told that snow would be a “rare and exciting event” which clearly it isn’t?
Why do climate scientists want to ignore the medieval warm period?
Why have average global temperatures remained virtually constant for the last 20 years despite the minuscule increase in the already minuscule amount of CO2?
Why do allegedly serious climate scientists want label those of us who do not believe what they say as “deniers” and in extreme cases want us executed?
And finally
Why do you all talk a load of b*****s?

Sorry, but colour me somewhat skeptical about the purpose and value of this particular exercise.
If Revkin were genuinely serious about this, he would (and certainly could) have posted his “invitation” as an update to the headpost – rather than buried deep in the heart of 600+ comments (many – if not most – of which seem to have been written by the un-premoderated recycler of drivel, Susan Anderson).
Come to think of it, considering his many years on the climate beat, it’s somewhat surprising that Revkin is not capable of compiling such a list of questions himself without further input. Certainly, a comparison of the Filibuster After Questions™ with the questions already posed by Steve at CA would be a damn good start for any self-respecting journalist with a curious and investigative mind.
So, colour me very surprised if this exercise turns out to be anything more than Revkin providing yet another delay/opportunity for Marcott et al (and/or their ghost-writers?!) to produce yet another non-responsive FAQ.

Stephen Richards

Leave it to Steve Mc. There is no-one else that the team fear more and that we can trust more.

Stephen Richards

LEAVE IT TO STEVE. I’ve read some of the comments over at Revkin. Inept. All on the wrong tack.


Dear Dr Marcott et al
You went to a lot of trouble to produce a set of temperature readings for a long time period.
Then you “Mean-shifted the global temperature reconstructions to have the same average as the Mann et al. (2008) CRU-EIV temperature reconstruction over the interval 510-1450 years Before Present.” (Your statement on RealClimate blog)
What was the size of the “Mean-shift” adjustment?
Why do you have more confidence in Dr Mann’s work than in your own?

1) This question concerns the uncertainty about the scale normalization of Marcott et al. proxy temperature anomalies (calculated initially relative to 5500 – 4500 YBP) to those of Hadcrut4 (calculated relative to 1961-1990).
Shakun writes

Mean-shifted the global temperature reconstructions to have the same average as the Mann et al. (2008) CRU-EIV temperature reconstruction over the interval 510-1450 years Before Present. Since the CRU-EIV reconstruction is referenced as temperature anomalies from the 1961-1990 CE instrumental mean global temperature, the Holocene reconstructions are now also effectively referenced as anomalies from the 1961-1990 CE mean.

Is the net effect of this process a simple linear increment of the reconstruction by ~0.3C? If yes – what is the error on this offset value ? If no – how was the renormalization achieved ?
2) To justify a statement that 20th century warming is unprecedented since the last Ice Age it must be demonstrated that any previous climate excursion of a similar magnitude would have been observed in Marcott’s data. Hence the importance of Tamino’s work. I performed an independent study which concludes that it would not be possible to detect any such ~1C excursion lasting less than ~400years because of proxy timing uncertainty. This is supported by this statement on realclimate:

Jeremy Shakun writes…. “The paleoclimate records used in our reconstruction typically have age uncertainties of up to a few centuries, which means the climate signals they show might actually be shifted or stretched/squeezed by about this amount.

Do the authors agree that this age uncertainty implies that the reconstruction are indeed insensitive to excursions lasting only 200 years ?

Ian H

Leave it to Steve. His questions will go to the heart of the matter. Don’t set up some easy straw men for these guys to knock over instead.


What is the new scientific practice used in Climate science that allows data to be changed to fit the conclusion?
I’ve tried Wiki but that’s no help as usual.


Does he consider re-dating proxies in order to force a hockey stick shape to be scientific fraud?

I would be interested to know if the MS was rejected by Nature, and whether the reconstruction resembled the thesis version or the Science version if so.

Julian Flood

I have seen a response somewhere that the resolution of the proxies is 120 years, but the answer was crafted rather carefully.
Does the reconstructed record have 120 year resolution along its whole length, or does the resolution vary? If the latter, how poor does the resolution get?

I agree with statements saying “Leave it to Steve”. This is very much a matter of statistical methods of analysis, about which he is an expert, and a matter in which he is already engaged. Go get ’em Steve!

A C Osborn

What I find so disappointing in the comments for the original Revkin article is the number of posters that say that the original Hockey Stick is robust and has been replicated.
Mann’s own work prior to the year 2000 proves it is absolute crap.
The lack of a MWP and the changes to his own 20th century temperature Records shows a complete lack of Integrity.
Add to that the claim of “Unprecedented 20th century warming” shows it to be absolute nonsense.
What a really sad day for SCIENCE.

There is only one question: “How is it possible to take the same set of data and come up with two different graphs?”

To prevent a flood of questions both good and bad, like a couple of other commenters here I figure the most productive option is simply to let Steve McIntyre pose questions on behalf of skeptics. As far as I can see no-one else is quite so deeply into this paper and its problems than Steve. And his clinical approach means maximal trust from almost all in the skeptical community.


Jean S has it laid out clearly @ ClimateAudit.


There’s only a handful of people whom questions should be taken from. Steve number 1 of course, and Clive Best has done some good work on this. Even with the others still best to go through Steve so duplicates aren’t submitted.

Yes. Mr. Marcott, are you truly the Son of Mann?

Louis Hooffstetter

I agree with Moshpit and others: Let people who can see through the statistical illusions ask the hard questions (Steve Mcintyre, AMAC, Brandon, and Just The Facts). But be sure to include the following:
Please provide a list of all reviewers.
Please provide a list of everyone involved with the statistical analysis of the data.
Please provide a list of the editors at Science who approved this paper for publication.
Please provide the code.
Exactly when and where will all of the above information be made available?
I don’t expect any real answers, I predict we’ll get very carefully parsed, obfuscating, weasel-worded statements prepared not by the authors, but by Peter Clark, Gavin Schmidt, Mike Mann, and other members of the Team.
Judy Curry says::
“Please don’t… inadvertently send them to the RealClimate refugee and training camp.”
Too late. Marcott & Shakun have already entered the ‘House of the Rising Sun’.

After reading all of the analyisis of this at Climate Audit, Steve has all the questions to be asked.
Go Steve !


Steve Mc’s comment makes it clear that he is ready to communicate with Revkin on the high priority questions he has, so it’s better if most of us stay away from Dot Earth on the subject and let Steve assemble the questions he thinks are most significant. If there is a barrage of assorted questions then the authors will cherry pick the ones they want to answer and pretend that they’ve been responsive.
Perhaps it is a useful exercise to brainstorm here and refine some questions in case Steve et al. find any useful suggestions. Just to prime the pump, here are some questions which Jean S already posted at Climate Audit:
oh, I haven’t even had time to ask all the questions and I’m sure there are more to come later. Some questions (apart from those obvious relating to the re-dating and the “upstick”), not in any particular order:
1. Where’s the code? Where’s the code for Shakun et al., Nature (2012) as promised in the corresponding SI?
2. In your temperature perturbation MC analysis for alkenones and Mg/Ca proxies, why did you account only for the model uncertainties?
3. What is the rationale for using two independent normal (symmetric) variates for perturbation in the exponential model (Mg/Ca proxies)?
4. What exactly is the uncertainty described for the ice core proxies (SI, p. 6 (f))?
5. Why did you join the instrumental temperature record (CRU) with the EIV reconstruction into a single curve without any indication of this in the case of Mann et al (2008) EIV-CRU?
6. Why did you use EIV-CRU (land only) as the reference? Wouldn’t it be more natural to use, e.g., EIV-HAD (land+ocean) from the same reference?
7. Why did you use the early portion of EIV-CRU (510-1450 yr BP) for the reference? Wouldn’t it be more natural to use the later part of the overlap (or the full overlap), where the Mann et al (2008) reconstruction is more reliable? How sensitive are your conclusions regarding comparision with the modern temperatures to the choice of the reference time interval and the reference series?
8. What are the uncertainties for the (EIV-)CRU record post 1850?
9. Why do you use 1\sigma uncertainties for your reconstruction, but 2\sigma uncertainties for Mann et al (2008)?

John B

Since it was my comment which Andy Revkin responded to, and after reading reactions at a number of locations, let me put forward a suggestion which may be acceptable to all parties. It is clear that any questions should be framed with only one intent, to extract answers to facts which should have already have been largely answered in supporting data supplied as part of the published paper. It is therefore clear that it would be far preferable if Marcott et al make available ALL code and any other supporting data immediately. It would improve their credibility to do so.
In the event they are unwilling to do this, I suggest that a maximum of four questions to be asked by EACH of Mr S Mcintyre, Jean S, Mr S Mosher, Nick Stokes, and two others considered non skeptics who may have questions.
Supplimentary questions should be allowed where the original question has not fully answered.
A video of the questions and answers should be posted by Andy Revkin on his Dot Earth site.

Rud Istvan

Leave it to Steve. Andy Revkin has a soap box, but not more. Steve has the facts, and a world wide following.
I have taken a different tack. Wrote a concise short request to Science editors that the article be substantially revised in light of abstract sentence 1 and supporting figures 1a and 1b being directly contradicted by S18c and now the FAQ, or retracted entirely since the core top redatings were unnoted and unjustified although proven in some cases to be in direct contravention of published core top dates and/or age controls. The editors have acknowledged the communication, and requested time for due process under Dr. Smith’s supervision.
If Science does not act in some appropriate manner in a reasonable period of time, I will provide Anthony with the archived communications for an expose.

Ian W

I am more interested in the Research Management.
Chapter 4 of the Marcott PhD Thesis was the basis for the Marcott et al paper. The PhD thesis did not show any uptick in the 20th century.
* Why was it decided to revisit that thesis and adjust the data times (core tops) changing the output?
* What was the reasoning behind the redating of each of the proxy data series?
* Who was the proponent for the alteration in the proxy data series and timing?

Jim McCulley
John B

Just for the record I happen to think Andy Revkin does a much better job of reporting on highly technical climate and other issues than most reporters.

Jim McCulley

Never fear I am all over it. I have been writing on this subject for years. And had Bill Mckibben laughed out of the Adirondacks with his step up for carbon campaign. 🙂

Chuck Nolan

Adam says:
April 7, 2013 at 12:05 am
“Thus, the 20th century portion of our paleotemperature stack is not statistically robust, cannot be considered representative of global temperature changes, and therefore is not the basis of any of our conclusion…”
Why did you elect to not exclude that period which was “not statistically robust”………………….
The published Abstract appears to be 100% truthful although it leaves a false impression by omission.
Without their hockey stick a cooling problem materializes.
1. Was the Marcott hockey stick blade included on the released graph?
2. Why was the not statistically robust statement not in the Abstract?