Wahl and Amman #2

Here are some first thoughts. So far I don’t see anything in W-A that affects any of our results. Indeed, I expect that W-A is going to be very positive for this debate, as the points at issue are going to be narrowed sufficiently closely that any people actually interested in the results (as opposed to spin) will be able to finally compare apples and apples. It will require a little cutting through the packaging, but since they’ve commendably provided code for the first time, it won’t be too hard.

As I work through their code in the next few days, I will highlight any points of methodological difference and and will immediately provide notice of the issue. This is what you’re supposed to do in public businesses (and most businesses do) and it’s a good policy.

One of the first questions that readers of this site have had e.g. Paul Gosling – what happens without the bristlecones. Here’s a cutout of their run archive without bristlecones
In Hockey Team style, they provide a spaghetti graph so that it makes it more difficult to examine the individual calculation. However, you can pretty much see the purple calculation up to the end. The legend says that if the bristlecones are omitted, the calculation is "without merit".

It will be interesting to see how they comment on Mann’s grandiose claims that their reconstruction was "robust" to the presence/absence of dendroclimatic indicators in total (since a very quick inspection of this graphic confirms our report that this representation was false.) It will also be interesting to see their explanation as to how – if a reconstruction without bristlecones is "without merit" – a calculation with bristlecones can possibly have any merit in the face of our many criticisms of bristlecones not only as a flawed proxy, but as a proxy with flaws known to Mann et al.

In any event, the graph below shows that they don’t get a hockey stick without bristlecones either.

Figure 1. Excerpt from figure on Amman’s ucar website.

A first comment on the code. It’s really nice to see a paleoclimate article with code. Good for Wahl and Amman on this. I presume that we can take a little credit for this. It’s provided in a UNIX version. I was able to make a few tweaks to the code to make it Windows compatible quite quickly. I’ll post up these tweaks a little later in the day.

I now have an operational 15th century step result. The advantages of posting code should become obvious very quickly: reconciliations that otherwise take months of inquiry (and can still be inconclusive) can be done in a matter of hours, if not minutes.

Their results are NOT a replication of MBH, but an emulation and only an emulation of the regression-calibration step. For example, there’s nothing in the code to show an implementation of Preisendorfer’s Rule N for retention of PCs in tree ring networks in MBH98 – which was mentioned out of the blue last year for the first time as being a critical step. There’s nothing about estimating confidence intervals.

Although the website says that they "reproduce" MBH98 results, it would be more accurate to say that they emulate the MBH98 reconstruction method. For example, the correlation of their 1400-1450 reconstruction to the 1400-1450 MBH98 reconstruction was only 0.69 in my first check. I’ll plot up their emulation of this step against ours a little later, but at a first blush, they look pretty similar. The similarity is not chance, as in the main steps of their emulation, they use equivalent methodology to ours, the first version of which was archived almost 18 months ago.

Ironically, I’m not entirely sure yet what’s in here that isn’t already in our E&E paper (although with a different slant obviously). We show an emulation of MBH98 as do WA. We report that various permutations and combinations yield, on the one hand, high 15th century results and, on the other hand, low 15th century results, and that these differences pertain to the impact of the bristlecone pine and Gaspé series. Reading between the lines, it looks like Wahl and Amman get virtually the same results. In our respective emulations, it looks like the handling of the regression-calibration steps to make "reconstructed" temperature principal components is identical.

I’ll go through how they go from the reconstructed temperature principal components to NH temperature later today. Mann has carried out some re-scaling here and it’s never been very clear what he did. It looks like W-A had some difficulties here as well (even with input from Mann) as there’s code added in as late as April 2005 modifying a scaling step. I expect to be able to reconcile our results to W-A results step by step without a whole lot of difficulty. I think that the entry of the W-A articles with code is a highly positive development.

Naturally, their presentation will be filled with all sorts of hyperbole and probably even some disinformation, but, for the first time, some one from the Hockey Team has stepped out of the foxhole with some code. We will be able to reconcile calculations in a business-like way to actual Hockey Team calculations and show exact points of difference without shadow boxing.


  1. John A
    Posted May 13, 2005 at 12:25 PM | Permalink

    I have to squint to see the graph for the (bristlecone pine) trees, but to me it looks like without the bristlecones, they get no hockey stick. What they get is noise.

    It looks like an attempt to fit the non-BP curve to the Hockey Stick, but if you pull them apart, you won’t see a hockeystick.

  2. BEEEP
    Posted Jun 1, 2005 at 6:06 PM | Permalink

    yea thats true, John. :/ no hockey stick

  3. Joe S
    Posted Jun 1, 2005 at 6:07 PM | Permalink

    :/ no Hockey stick that u can see.

  4. Tom Still
    Posted Jun 8, 2005 at 7:30 PM | Permalink

    Why don’t you folks write an abstract or a lay rewrite of each of these articles (appended to the article) suitable for the lay reader (say a college junior majoring in construction management)not knowledgeable of all the scientific jargon or the models’ names or science celebrates in the debate, etc. You should realize that many people interested in the debate over Global Warming come to these web sites/pages to find out which side of the debate is right. The debate over Global Warming policy will be decided by the audience (the body politic) not the scientists fighting on the field. You best make you output easily understood by these people (like me).

  5. John A
    Posted Jun 10, 2005 at 8:52 AM | Permalink


    I don’t know that we can provide all of the background information that you might want on this subject.

    The best backgrounders are:

    http://www.climateaudit.org/index.php?p=166 – Ross McKitrick’s paper on the history of the Hockey Stick

    http://www.john-daly.com/hockey/hockey.htm – the late John Daly’s assault on the Hockey Stick, prescient in many ways.

    http://www.uoguelph.ca/~rmckitri/research/MM-W05-background.pdf – background to the scientific papers by McIntyre and McKitrick.

    There are plenty of others.

  6. Martin Ringo
    Posted Jun 10, 2005 at 5:13 PM | Permalink

    What are the bristlecone variable names? I understand that ca534 is one. As I looked at the 70 tree ring series, there appears to be rougly 9 “hockey stick” shapes (ca528, ca529, ca530, ca534, co523 -weak, co525 -weak, co545 – weak, nv511 – late effect, and nv512). These correspond to a rough eyeball test and an ad hoc difference in trends (1400-1901 versus 1902-1980 fits) expressed as a studentized ratio. Are these all bristlecone series?

  7. Steve McIntyre
    Posted Jun 10, 2005 at 6:39 PM | Permalink

    I’ve posted up a summary of type details at http://www.climateaudit.org/data/network.details.txt. This is tab-separated and should open in Excel. PILO and PIAR are bristlecones and PIBA is the very similar foxtail pine. ca528 through ca534 are all bristlecone/foxtail; nv512 is bristlecones; nv511 is a high-altitude limber pine (which is sometimes strip bark as well.) co523, co525 are bristlecone; co545 is high-altitude limber pine.

  8. Steve McIntyre
    Posted Sep 26, 2005 at 3:48 PM | Permalink

    This post steadily gets really a lot of hits. Anyone feel like saying hello?

  9. john prendergast
    Posted Oct 7, 2005 at 10:38 AM | Permalink

    Interwsting that the model strats from 1400, 1400 was a historically cold period. Had model been made from 200 AD it would have shown warming to about 800 and then marked cooling to 1400. In 800 AD greenland was discovered and aptly named as there was no ice cover.

  10. Jim O'Toole
    Posted Oct 7, 2005 at 11:01 AM | Permalink

    Hello. Long time lurker, first time poster. Interesting discourse here; keep up the good work.

  11. Rick Katz
    Posted May 11, 2006 at 6:21 AM | Permalink

    This website satisfies all my global warming needs. THis website makes me feel good.

  12. Students4Truth
    Posted Aug 2, 2006 at 12:12 PM | Permalink

    I hope you all continue to feel good about misleading the public…by attacking the research which is backed by almost all credible scientific studies and using the technical jargon that few understand, you hope to confuse the public into merely believing the truth you have set in front of them. I, for one, hope that the truth comes out before it is too late. Thanks for continuing the trend of America’s blissful ignorance.

  13. ET SidViscous
    Posted Aug 2, 2006 at 12:17 PM | Permalink

    Who is the arbiter of what truth is.


    If so might I suggest you learn the technical jargon.

  14. Lee
    Posted Aug 2, 2006 at 12:37 PM | Permalink

    re that old post in #9 –

    It’s interesting that no one bothered to correct Prendergast’s claim that in AD900, Greenland had no ice cover.

  15. Jean S
    Posted Aug 2, 2006 at 12:57 PM | Permalink

    re #14: I don’t know about others, but if I were here to correct all the silly mistakes by people like JP or you, I’d expect to be paid for it. I don’t, and I try to concentrate on more productive issues. How I wish you would do the same.

  16. students_4_truth
    Posted Aug 2, 2006 at 1:27 PM | Permalink

    We are not interested in Absolute Truth. But we are interested in ‘little t’ scientific truth. Please continue your audit. The discussions are very interesting.

  17. Lee
    Posted Aug 2, 2006 at 2:58 PM | Permalink

    And yet, jean, almost every post I make get responded to by people claiming I’ve made mistakes or challenging what I have to say. I part that is inevitable – I am the one out of agreement here – but now and again I feel justified in returning a silly nitpick.

    I often ignore truly silly things like this, but this one caught my attention becasue it has been so often repeated in some form or other as evidence that the MWP was clearly a lot warmer than now. And I’ve been attacked for pointin out that even the true description is not adequate such evidence, much less this kind of amazing exageration.

  18. Dave Dardinger
    Posted Aug 2, 2006 at 3:38 PM | Permalink

    Really, Lee. Don’t be such a troll. People with brains in their head knew (or at least assumed) that Prendergast was talking about there being no ice cover at the near shoreline areas in southern Greenland, not that the entire continent of Greenland was ice-free. Explorers don’t generally climb mountains just to see if it’s cooler there, “Yes, there’s ice here at 1000′; guess we can’t call this Greenland after all!”

  19. Michael Jankowski
    Posted Aug 2, 2006 at 3:42 PM | Permalink

    Re #12,

    Thanks for continuing the trend of America’s blissful ignorance.

    If you’d been following this debate at all, you’d know that M&M are Canadian (which Mann loves to point-out for some reason). Please don’t try to spin this and say you meant “North America as a whole” or “all of the Americas,” because we can tell from your context.

    So I’m not sure how much of a “student” you are, nor if you know what the definition of “truth” is. You don’t seem “blissful,” but there seems to be “ignorance” in your post. But kudos on using “4” instead of “for.” I’ll bet that kind of cuteness on the internet gets you all sorts of instant messages from other teenie-boppers who want to save the world but don’t want to start by helping mom do the dishes.

  20. Lee
    Posted Aug 2, 2006 at 4:15 PM | Permalink

    Even if, Dave, those areas are nice and green (for the 3-4 month growing season, like it was when the norse settled there) and not ice covered right now. Adn for the most part, the evidence of farms and buildings are still there – they didnt GET ice covered, except maybe on some of the always-marginal fringe farms and outholdings. So what was he claiming again?

  21. Mark T.
    Posted Aug 2, 2006 at 4:44 PM | Permalink

    I hope you all continue to feel good about misleading the public…

    Curious how we’re misleading anyone here?

    by attacking the research which is backed by almost all credible scientific studies and using the technical jargon that few understand

    Uh, we’re simply using the same technical jargon these scientific studies use. I’m also curious about your thoughts on what constitutes “credible?” Would that include failing to report adverse statistics and claiming otherwise?

    you hope to confuse the public into merely believing the truth you have set in front of them.

    The truth is the truth. If methods are manipulated to obtain preconceived outcomes, and someone here uncovers that manipulation, it is nothing more than uncovering the truth.


  22. ET SidViscous
    Posted Aug 2, 2006 at 4:54 PM | Permalink

    Well put

  23. Dave B
    Posted Aug 2, 2006 at 5:13 PM | Permalink

    #20…you are wrong here, lee. sheep dung is unlikely to survive 500 years if it is not frozen.

  24. Lee
    Posted Aug 2, 2006 at 6:02 PM | Permalink

    “under the sand” is not “ice covered”

    Last time I looked the words ‘sand’ and ‘ice’ referred to different kinds of things. The word “frozen” does not mean the same thing as the phrase ‘covered in ice.’ Even frozen sand, if it were, is not the same as ‘covered in ice.’

    BTW, if you are sayign sheep dung cant survive 500 years unless it was frozen, and this is equivalant to saying it was covered in ice, does that mean you accept that the quelcayya plant remains are good evidence for a 5,000 year unique event?

  25. welikerocks
    Posted Aug 2, 2006 at 7:27 PM | Permalink

    fossilized dung is called “coprolite” it’s a geologic term.
    Google coprolite and Greenland …and you get all kinds of information. LOL

  26. Posted Aug 2, 2006 at 7:41 PM | Permalink

    Given that sand is made of a solid, it can’t freeze unless it’s wet. Being wet involves water, and frozen water is ice.

    Therefore, something covered in “frozen sand” is covered in a mixture of sand and ice, no?

  27. welikerocks
    Posted Aug 2, 2006 at 7:59 PM | Permalink

    #26 Nicholas,

    Rocks are considered “liquid” because of the way they behave, grow and move. They are already “frozen” because they are cystalized particles. Water would have to be around them to make “ice”. But, fossils found in rock are “frozen” if you think about it that way. (From my husband here, the geologist 🙂 )

    If you google “Coprolite +Medieval Warm Period” there are tons of papers using them in research.

  28. Posted Aug 2, 2006 at 8:23 PM | Permalink

    welikerocks : OK, I understand. I always thought that “frozen” referred only to a substance which had gone from liquid to solid state, or else to something which had stopped moving.

    I see that the word is overloaded (i.e. has multiple meanings). So, sorry for the confusion.

    I would like to read more about Coprolite, but I’m busy now, next time I’m bored I’ll read up on it 🙂

  29. welikerocks
    Posted Aug 2, 2006 at 8:32 PM | Permalink

    #28 No apologies!
    I was just throwing more confusion or info into the mix . All dung can be fossilized. I don’t think it has to be frozen with ice to survive. If the sheep coprolite was found in frozen sand, it means sand with water in it. And husband says all sand has moisture in it, even in the desert, you’ll find it when you dig below the surface, the sand gets darker, the darkenss is the moisture. It’s almost never zero percent moisture.

  30. welikerocks
    Posted Aug 2, 2006 at 8:43 PM | Permalink

    Oh I see what the problem is. Sheesh.
    Dung can be fossilized without being frozen, but in this case from the article linked by #23 Dave B the moisture in the dung itself froze! because it got cold, and it was also covered with sand when it froze so that’s how it was preserved.

  31. Chris O'Neill
    Posted Nov 16, 2006 at 2:14 PM | Permalink

    Wahl and Ammann’s Scenario 6c (1450 network) shows that excluding the 15 highly weighted proxies in MBH98 noamer PC1 removes about 0.06 degrees C average of hockeystick bias from the reconstruction in the 1450-1799 period.

    Other than this bias which is fairly uniform before 1850, these proxies don’t appear to do any harm to the 1450-1901 reconstruction.

    Given that there is no objective reason why these proxies should suddenly behave differently before 1450, and the fact that the 1400 network reconstruction average agrees extremely well with the 1450 network reconstruction average from 1450 to 1799, including these proxies in the 1400 network shouldn’t do any more harm than introduce a hockeystick bias of around 0.06 degrees C.

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