Michael,

Can you identify who you are addressing your comment to, i.e. the person or people who exhibit these objectionable behaviors? Thanks.

MT, you say
AMac withdrew from participation on my blog when I refused to take a position on the matter.
This is not quite correct. I started commenting at Only In It For The Gold, but that drew to a close. An on-topic comment of mine failed your moderation. Then an OIIFTG "regular" offered an insult to me. My civil, issue-oriented response also failed moderation.

All of which is fine. OIIFTG is your blog, and you put up some excellent posts. I read it sometimes, but will write in only rarely.

... Continuation from Part 1 ...

2. Tiljander et al provide interpretations of the meaning of three of the proxies in the pre-1720 period when climactic influences predominated.

2a. lightsum is a measure of mineral material in each varve. The authors claim that higher lightsum is associated with wet, cold winters that produce more winter snowpack, so that more inorganic silt is carried into the lake during the spring melt.

2b. darksum is a measure of organic material in each varve. The authors claim that higher darksum is associated with with warmer, wetter summers, where streams carry more organic material into the lake.

2c. xraydenseave (XRD) is the X-Ray density of each varve. This is in a sense a mix of lightsum (very dense) and darksum (not very dense). The authors claim that higher XRD is associated with a colder, wetter climate.

2d. thicknessmm is the thickness of each varve in millimeters. The authors do not assign a meaning to this proxy.

Thus, according to Tiljander:

Higher lightsum, Colder
Higher darksum, Warmer
Higher XRD, Colder
Higher thickness, No assignment.

Contrast this with the way that these proxies are oriented in Mann08, for both the CPS and the EIV reconstructions.

Higher lightsum, Warmer
Higher darksum, Warmer
Higher XRD, Warmer
Higher thickness, Warmer

Mann08's interpretations are Inconsistent, Consistent, Inconsistent, and (possibly) Inconsistent with the detailed interpretations offered by Tiljander et al.

The text of the paper and of the SI do not discuss these inconsistencies. (In my opinion, the authors were not aware of it: an honest mistake.)

In his Reply to McIntyre and McKitrick's Comment in PNAS in 2009, Prof. Mann does not acknowledge these inconsistencies.

Neither the paper's authors, nor Gavin, nor any other climate scientist, nor any AGW Consensus advocate has, to my knowledge, asserted that the authors of Mann08 affirmatively chose their unconventional interpretations. Eli Rabbett (at Stoat) and Steve Bloom (earlier in this thread) have claimed that the authors could have, and might have, done so.

That is indeed correct. However, it seems to me that in that case (a) the authors should have explicitly so stated, and that (b) rigorous peer-review should have led to the Editor's insistence that the authors explicitly explain their unconventional interpretations.

3. In a 2009 Science paper, Darrell Kaufman and co-authors pre-published a draft paper with one of the Tiljander proxies in its inverted orientation. Upon learning of Steve McIntyre's criticism, Kaufman et al. corrected their manuscript so that the proxy was used in the orientation proposed by Tiljander. This episode is mentioned in a couple of Climategate emails.

In conclusion, I have laid out a case for a one word answer to the question

"Are the Tiljander proxies calibratable to the instrumental temperature record, 1850-1995?"

No.

A detailed discussion of the inverted XRD proxy is presented in the post The Newly-Discovered Jarvykortta Proxy -- II.

What is the strongest case for “We can’t tell?” What is the strongest case for “Yes”?

In my opinion, deducing that the answer must be “We can’t tell” or “It doesn’t matter” from the tracings in the twice-corrected SI Fig 8a is a very weak argument.

toto, in the upthread comment beginning "The link provided to supplemental 8a was directly below the comment..., you wrote

Amac [asks]: "Are the Tiljander proxies calibratable to the instrumental temperature record, 1850-1995?"

I think that people have been trying to give you the following answer:

"We don't know, because it depends on whether the modern anthropogenic effects in Tiljander's data actually erased the temperature signal - something that is very possible, but not certain. Things being so, we can do either of two things - use the series, or not. Being wary of a priori decision, we do both. Turns out, it doesn't change much concerning the exceptional status of late 20th century warming."
I agree that "whether the modern anthropogenic effects in Tiljander's data actually erased the temperature signal" is a potentially useful way to get at my Calibratable? Question. Let's look.

Here are some reasons to think that the non-climactic signal has overwhelmed the climate-related signal, beginning around 1720 and getting progressively worse through the 20th century. It may be helpful to get a picture of the proxies, either as Mann08's Supplemental Figure 9, or as they are presented in Tiljander's original Boreas, 2003 paper. Both are linked here.

1. Tiljander et al. caution that this is the case. Page 572:
In the case of Lake Korttajarvi it is a demanding task to calibrate the physical varve data we have collected against meteorological data, because human impacts have distorted the natural signal to varying extents during the past 280 years...
Page 575:
In the 20th century the Lake Korttajarvi record was strongly affected by human activities. The average varve thickness is 1.2 mm from AD 1900 to 1929, 1.9 mm from AD 1930 to 1962 and 3.5 mm from AD 1963 to 1985. There are two exceptionally thick clay-silt layers caused by man. The thick layer of AD 1930 resulted from peat ditching and forest clearance (information from a local farmer in 1999) and the thick layer of AD 1967 originated due to the rebuilding of the bridge in the vicinity of the lake's southern corner (information from the Finnish Road Administration). Varves since AD 1963 towards the present time thicken because of the higher water content in the top of the sediment column. However, the gradually increasing varve thickness during the whole 20th century probably originates from the accelerating agricultural use of the area around the lake.
It is possible to discern the effect of the 1967 bridge construction as a spike in all four of the Tiljander proxies (Mann08, Fig. S9).

... Continues in Part 2 ...

toto, thanks for the constructive feedback.

First of all, I'm not sure which post of mine you refer to--it's very hard to identify them with the current thread implementation at this blog. But your point is valid. It has come to seem obvious to me that Mann08 considered potential drawbacks with the Tiljander proxies, since they discuss these issues in the Methods. You're right, somebody coming new to this debate wouldn't know that from reading some of my comments.

But comments have to be kept short and on point. There are many other caveats and provisos I could list -- but don't. Anybody who takes the time to learn about the case will quickly appreciate the point you raise.

Still, credit should be given when due, and you're right, Mann08 authors did consider the issue. Though they mistakenly didn't give it enough credence and disqualify these proxies, in my opinion.

As far as "crowing about conspiracies" -- I am at a loss to respond to that. I don't believe I've ever done that, and regret it if I have. People aren't perfect, and social organizations aren't perfect. This applies to climate scientists and to the institutions of climate science -- of course. In my opinion, the treatment -- lack of treatment, actually -- of the shortcomings of Mann08 can teach about what's wrong. That should help set climate science on an improved course.

"Most planes don't crash" isn't an argument against investigating the crashes that do occur. Do events like Sullenberger safely landing his jet in the Hudson River also teach about aircraft safety? Yes, they do. Both good processes and bad processes should be acknowledged and appreciated.

"The link" that Gavin supplied is to the modified Figure S8a that is located on Prof. Mann's website at Penn State. Clicking on it should bring up a PDF.

Here it is again, copied from Gavin's comment, since it's devilishly hard to navigate among comments with the current C-a-s threading implementation.

Nov. 2009 version of Fig. S8a.

Note that the Supplemental Information at the PNAS website contained an earlier version of this figure, last time I checked. That could confuse matters, as both the reconstruction traces and the color schemes vary among the different versions.

Upthread, scac wrote
This thread is an instructive example of how the two sides of the debate are talking past each other...
As a Reply to that comment, Gavin made some interesting remarks. (Note that the current software implementation requires one to click on the "reply" triangle at the end of scac's comment to see them.)

Gavin wrote,
The original supplementary material included reconstructions with and without the Tijlander proxies (addressing Amac's point).... ["Auditors" prefer] to rehash issues over and over again in order to tie up conversations - including this one.
Gavin,

Both Lucia and Judith Curry have pointed out that climate scientists may believe that they have adequately responded to a question posed by a member of the public, while leaving that question unanswered.

This is the case here.

The question I have posed is,,

"Are the Tiljander proxies calibratable to the instrumental temperature record, 1850-1995?"

Contrary to Gavin's assertion, neither the original supplementary materials nor the twice-revised Figure S8a address this point. "Addressing this point" would take the following form:

"Yes, the four Tiljander proxies employed in Mann08 are calibratable to the instrumental record."

Or,

"No, the four Tiljander proxies employed in Mann08 are not calibratable to the instrumental record."

In my comment upthread that begins
As the subject of Gavin's comment that was the impetus for this post...
I said,
Gavin's following words are helpful in moving towards a resolution of the controversy surrounding Mann08.
That comment's point #3 is a good-faith effort to interpret those words. This is followed by
4. Question to Gavin: Is my interpretation in #3 a fair and accurate representation of the point you intended to make?
Gavin's words were helpful, with respect to the Calibratable? Question. A follow-up from him on point #4 would be a further positive development, I think.

scac,

With respect to the two sides talking past one another: I am making a good-faith effort to adhere to the host's request to not focus on the technical aspects of the use of the Tiljander proxies in Mann08. What Gavin, Willis, and others do is obviously beyond my control.

This necessarily means that my comments will appear to be non-responsive to some of the points that Gavin and others raise.

As far as your interpretation of the reconstruction labeled "NH CPS minus 7 w/o tree rings" -- You make an excellent point in highlighting this result (as Gavin did at RealClimate, I believe, and also earlier in this thread). It indeed seems that non-tree ring proxies yield similar reconstructions to the tree-ring-including reconstruction (black line), whether theTiljander proxies are included (dark blue line) or excluded (light blue line).

Three remarks.

1. The Fig. S8a that we are discussing is the third version that has been posted by Prof. Mann. It isn't present at the PNAS website, nor is it linked. People who work from the SI downloaded from the PNAS website will be unable to follow this exchange.

2. The fact that Fig. S8a needed two corrections highlights that the calculations behind these reconstructions are complex, and errors are possible.

3. There are subtler problems with this result, if indeed the Tiljander proxies are uncalibratable. It would strongly suggest that the addition of invalid data leads to a reconstruction that is nearly as good as one that is built on valid data. This ought to be a red flag, in my opinion.

Steve, I accept that you don't find late Holocene paleoclimate to be an interesting scientific subject. The authors of Mann08, and I, obviously feel differently. There's a discussion to be had about the pros and cons of people's enhanced ability to form virtual communities around the subjects that most interest them; I'll forgo that for now.

It is possible that Mann08's authors intentionally used the Lake Korttajarvi varve proxies in a way that the original authors deemed inappropriate.

If so, it would have been good practice for the authors to have made this point explicit in the Methods, where they spend considerable time discussing these proxies.

And effective peer-review would have led to PNAS' editors insisting that the authors address this issue (if it is an issue).

However, to my knowledge, the authors of Mann08 have not made this claim: in the paper, or the SI, or their 2009 Reply to McIntyre and McKitrick, or elsewhere.

I explored one aspect of "inappropriate" use of a proxy in a blog post about a hypothetical "Jarvykortta River" data series, here.

As the subject of Gavin's comment that was the impetus for this post, I will respond to his comment upthread that begins
As expected, the pathological dynamic worked it's magic again. I say pathological advisedly because in both of the responses Amac and Willis both simply regurgitated points they've made before without bothering to read what I said, and without clicking on the link...
1. In my opinion, Gavin's comment makes many claims that merit a technical rebuttal. His comment also includes a substantial number of straw-man arguments, non sequitors, and gratuitous insults. In the spirit of Keith's request, I'll forgo addressing these here.

2. One approach to a complex and contentious problem is to look for component issues that might be resolvable. Ideally, such a component can be expressed as a plainly-worded and easy-to-understand question that (if answerable) has the promise of simplifying the overall problem. Sometimes this is not possible. Instead, a series of If/Then premises have to be considered in sequence, or simultaneously.

While this approach is successful for individuals tackling advanced suduko, it isn't preferred. A better way to solve a hard suduko is to begin by identifying the easier parts of the puzzle, and filling them in. Keeping things holistic and complex is a strategy that is particularly ill-suited to occasions where participants bring different skill sets to the table. And where people have strong preferences as to the outcome. And where trust is low and emotions run high. All these caveats apply to Mann08.

3. I've distilled my concerns about the use of the Tiljander proxies in Mann08 to one question.

"Are the Tiljander proxies calibratable to the instrumental temperature record, 1850-1995?"

To date, to my knowledge, this question has never been directly answered by an author of Mann08, or by a working climate scientist, or by a prominent AGW Consensus advocate.

In his comment supra, Gavin says
There is a focus on a very specific point - that does in fact have a very easy resolution - but one which has no actual import. Discussing something that doesn't matter is by definition a waste of time, and so scientists will disengage.
His grammar is elliptical, but it appears that Gavin's "very specific point" is the "Calibratable? question" that I repeated just now.

If so, Gavin's following words are helpful in moving towards a resolution of the controversy surrounding Mann08.

3a. "that does in fact have a very easy resolution" would indicate that Gavin believes that the "Calibratable? question" is easily resolved. Point of agreement.

3b. "but one which has no actual import. Discussing something that doesn't matter is by definition a waste of time" would indicate that Gavin believes that the "Calibratable? question" is trivial. In contrast, I think that Mann08's methods absolutely demand the calibratability of all of the proxy series that are used in producing the paper's key results: the CPS and the EIV paleotemperature reconstructions. Point of disagreement clarified; the discussion is advanced.

4. Question to Gavin: Is my interpretation in #3 a fair and accurate representation of the point you intended to make?