delayed.oscillator

Climate, paleoclimate, huevos rancheros, and general asymmetry

Yamal III: Summary and Update

with 15 comments

A fair number of people have been visiting this humble blog in the last few days, presumably not for my excellent tips on where to find the best huevos rancheros in the world. My previous posts on Yamal are long and perhaps technical in places, so I wanted to provide a quick summary.

in Yamal I, I emulated the modifications of the Yamal chronology by Steve McIntyre. As I noted in that post:

Adding the Khadyta River series reduces the the level of the chronology though the 1970s and 1980s and into the early 1990s, when those data end. But if one includes both data sets, the series terminates similarly to the original Yamal chronology, of course (because the last few years are only present in the modern trees from Yamal). These changes are potentially important, and the actual scientific questions are interesting

I also noted that the manner in which the series are low pass filtered can change the impression of the impact of these changes. Smoothing and filtering series — particularly dealing with end points — is a complicated issue, so care is always necessary when designing, deploying, and subsequently interpreting smoothed series.

In doing the emulation, I noted that there are differences in the archived Yamal, McIntyre emulation, and my own. These probably arise due to the different curve fitting techniques (time varying spline for Yamal, nonlinear least squares for McIntyre’s R code, and standard spline or Supersmoother fitting for my emulation). In terms of identifying relative differences due to adding the Khadyta River data, though, these don’t seem to matter too much. Apparently, McIntyre noted that his RCS routine created a greater rise than the archived Yamal chronology (again, this is probably differences in curve fitting, if I had to guess), but I can’t locate the statement now.

I also see, via Deep Climate, that McIntyre has posted graphs showing the chronology from the full data set (including the complete set of trees from Yamal and Khadyta River). We seem to differ on showing the period from 1991 to 1996, apparently — I think if you are going to make rather strong statements about using all the data, you should use all the data, but I don’t expect us to agree on this.

So, more interesting perhaps is my second post, Yamal II, where I looked at the raw data from Yamal and Khadyta River. Here, I concluded:

Khadyta River does display the divergence problem, in that it ceases to track temperatures as it did from 1883 to the 1960s.

and, finally:

Relatively little more can be said about the specific case of Yamal at this point — I’ll leave that to the scientists working in this part of the world — but even my quick review of these data here shows that including Khadyta River raw data in the Yamal chronology does not result in a more accurate nor precise understanding of past temperatures in the region. This isn’t to say that some time in the past that Yamal didn’t experience divergence (this after all is a large part of the concern about divergence), but we can clearly see that Khadyta River does exhibit modern divergence.

That’s where I stand now, and I’m not sure what further insights will come from solely the data at hand. However, reading blog posts about this topic, I’ve become aware that there persist misunderstandings in how field and lab dendrochronology is actually done. So, hopefully there will a post about this from me in the near future.

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Written by delayedoscillator

October 7, 2009 at 12:18 pm

15 Responses

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  1. […] Oct. 7: DO has a third update and summary post and has promised a future post: However, reading blog posts about this topic, I’ve become aware […]

  2. […] October 7, 2009 · Leave a Comment The latest battle over the “hockey stick” has taken quite a turn, one that may finally lay to rest the latest absurd claims of its demise made by contrarians. In previous posts, we discussed climate blogger Steve McIntyre’s scurrilous accusations of “cherrypicking” against UK dendrochronolgist Keith Briffa, and summarized a a quick technical critique of McIntyre’s work by a dendrchronologist known as Delayed Oscillator. […]

  3. This blog is nothing but chaff to obfuscate the real issue which is that Briffa created the hockey stick himself using RCS almost 10 years ago. Steve only reproduced Briffa’s work. Your suggestion that Steve created a hockey stick himself to stir up controversy is ludicrous.

    eric1skeptic

    October 9, 2009 at 10:15 am

    • Hello Eric,

      I’m disappointed you don’t have something to add to the conversation, or some relevant and genuine question about the methods or data discussed here (particularly in this thread, 3 of 3), or a firm grasp of what I’ve actually written in my three posts on this subject. Please read carefully again, and then I invite you to engage in useful and measured commentary in the future here.

      All that said — and as a general notice to all visitors — I have no intention of allowing comments here to become the platform for hasty or ill-informed mudslinging (well-informed and creative mudslinging, perhaps … ). Useful technical issues, questions, and comments all posed with a modicum of politeness and genuine interest are welcome and indeed encouraged– if you want to denigrate working scientists, you’re going to have to find another venue which tolerates such things, sorry.

      delayedoscillator

      October 9, 2009 at 12:19 pm

  4. […] the comment section of this blog resemble the ‘Lord of the Flies’.  As I related to commentator Eric from Climate Audit in the thread below, I have no intention of allowing comments here to become the platform for hasty […]

  5. This question is not related to your post, but you might guess a possible answer given that it is your field or expertise. According to the statements from Briffa and Hantemirov, I undestand that both of them used the same raw data:

    Briffa: “The Yamal tree-ring chronology (see also Briffa and Osborn 2002, Briffa et al. 2008) was based on the application of a tree-ring processing method applied to the same set of composite sub-fossil and living-tree ring-width measurements provided to me by Rashit Hantemirov and Stepan Shiyatov which forms the basis of a chronology they published (Hantemirov and Shiyatov 2002)”

    Hantemirov: At that time we had close collaboration with CRU and I sent to Keith Briffa these raw data

    And I understand that the CRU archive comes from the work by Briffa. However, the CRU archive and the Hantemirov data in NCDC have different number of proxies according to McIntyre’s graphs:

    Briffa
    Hantemirov

    If they use the same data, shouldn’t they have the same number of proxies?
    (I’m not speculating nor implying a dim answer, I just don’t know :) )

    climafuturo

    October 9, 2009 at 6:01 pm

  6. Ops, re. my previous comment, I’ve just seen that the number of proxies in Briffa 2008 looks more like the Hantemirov-NCDC:
    Fig 3b:

    http://rstb.royalsocietypublishing.org/content/363/1501/2269.full.pdf

    I think I’m quite lost with this stuff :P

    climafuturo

    October 9, 2009 at 6:36 pm

    • Yes, if you look at Hantemirov and Shiyatov 2002, Figure 6, you see the full sample size.

      delayedoscillator

      October 9, 2009 at 6:56 pm

  7. WRT divergence. Can you quantify the correlation of the two series with the temperature record. It would be helpful to the debate to show how these series stand up to Wilson’s criteria in his 2008 study on divergence. Further, it would be interesting to see what temperature record you use to make this assesment as there maybe some area of disagreement there. Finally, it would raise the profile of your site if you got in the habit of posting turnkey code.

    [snip — Agreed ;) ]

    Steven Mosher

    October 22, 2009 at 8:51 pm

    • Hi Steve,

      I may get around to doing that (juggling data analysis requests and my own work is a balancing art I’m still learning at this early stage, we’ll have to figure out how that pans out for the long-term), but have you looked at Section 5 in the Briffa et al. Phil. Trans. R. Soc. B paper?

      The data I used, as stated in the post, is the CRUTEM3, JJA season.

      As to turnkey code, I use MATLAB, so deploying it is not as simple as R, but I’m considering how I can best do it.

      delayedoscillator

      October 23, 2009 at 4:05 pm

  8. Could you briefly remark on your qualifications and credentials in dendrochronology and statistics? Or point to an appropriate link?

    I’m just starting to read through your Yamal stuff — looks interesting!

    Incidentally, should you ever visit Santa Fe, NM, the huevos rancheros at Rio Chama steakhouse are superb. Best in town, imo.

    TIA y buen provecho,
    Peter D. Tillman
    Taos, NM

    pdtillman

    October 23, 2009 at 6:41 pm

  9. ya Matlab is less easy than R. But if you post matlab their are guys who will turn it into R for you and make it turn key.

    WRT hadcru JJA. You used a grid value? Honest question I asked a long time back on CA. Some studies I looked at used station data closest station) and other studies used a grid. Kind of a broad question, your thoughts on that. Also, in one paper Mann used a pick two strategy for corelation. thoughts on that.

    That’s it for now. I know its tough to juggling this and work.

    Steven Mosher

    October 23, 2009 at 10:41 pm

    • Hi Steve,

      The thing with Matlab is, I have a lot of home grown code that relies on other home grown code as well as Mathworks function, etc. so it is not a matter of posting a single turnkey script. Some will be simpler than others. But this is my goal in the future.

      In some applications, I think grid cell values are favored because they better represent average variability over a large region (vs. the particulars of any single station and its particular siting). I think this paper has a nice discussion of instrumental gridded data error models, too:

      http://www.agu.org/pubs/crossref/2006/2005JD006548.shtml

      I haven’t followed the particular issue of using two grid cell, although I could imagine a reason or two one might want to do this. Some statistical tests then become multiple comparisons though, right, so a degree of freedom adjustment. That’s a bit off topic here, though, maybe later.

      delayedoscillator

      October 24, 2009 at 6:36 pm

  10. I just cited you at dot.earth; watch for incoming.

    http://dotearth.blogs.nytimes.com/2010/03/17/your-dot-climate-concerns/

    Hank Roberts

    March 24, 2010 at 3:37 am


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