Ring Widths and Temperature #1

A common theme to recent questions has been the relationship of ring width chronologies to temperatures, and, in particular, the relationship of bristlecone chronologies to temperature. Rob Wilson has recently weighed in on this.

While it was nice of Rob to present some new material, people should not lose sight of the fact that the North American reconstruction presented by Rob is unpublished and it is based on unarchived material; his other comparandum, Salzer and Kipfmueller, is a very recent publication, again based on unarchived material.

So yes, the material is interesting and deserves consideration, but don’t you think that the matter should have been dealt with somewhere in the literature prior to the last few minutes?

Rob compared a composite of 3 bristlecone chronologies to a North American composite chronology, based primarily on unarchived data from D’Arrigo et al 2006. I’m not going to make a detailed response today. In order to respond, I started looking back into predecessor D’Arrigo and Jacoby articles since the 1980s and, in doing so, ran into enough interesting issues to make up about 15 columns. As a result, I’m going to respond in rather a piecemeal basis and maybe try to pull a consolidated reply at the end.

Rob’s North American chronology, drawing on Jacoby and D’Arrigo material, shows somewhat of a growth pulse in the last half of the 20th century. We’ve talked about the "Divergence Problem" in the past. If Rob’s chronology is right, then there wouldn’t appear to be a Divergence Problem. In fact, the Divergence Problem originates mainly from Schweingruber’s sampling and it turns out that there seems to be a remarkable discrepancy between Schweingruber and Jacoby-d’Arrigo as to whether ring widths in the last half of the 20th century went up or not – a controversy which originated in 1988-1989. A simple question like this seems to be unanswered nearly 20 years later. This issue inter-relates with the issue of CO2 fertilization – there’s a sort of 3-cornered battle with Graybill in one corner proposing increased growth and CO2 fertilization; Schweingruber in another corner saying no increased growth; and Jacoby and D’Arrigo in the third corner saying increased growth but due to increased temperature.

I’ll try to summarize the history of the debate from this point of view over a few posts.

Lamarche et al [1984]
Let’s start with Lamarche et al [1984], the et al including Fritts, Graybill and Rose, all important dendro figures, which reported enhanced 20th century growth for Sheep Mountain bristlecones, arguing that the increased growth could not be accounted for by climatic factors.

As a follow-up to this paper, Graybill carried out a fairly significant collection of high-altitude sites in the mid-1980s, reported on in Graybill (1987), conference proceedings which I’ve been unable to locate, but which was cited in contemporary literature. This collection led to virtually all of the sites in Mann’s PC1. It was financed by the Carbon Dioxide Information program (CDIAC) of the U.S. Department of Energy. Later, as we’ve pointed out, the Graybill sites morphed into Mann’s PC1. Graybill and Idso [1993] reported on many of these sites (pdf here). While the collection was nearly all bristlecones and foxtails, there was also one high-altitude limber pine site from Colorado, which I’m going to come back to on another occasion.

The concept of CO2 fertilization was strongly criticized by dendrochronologists, for a variety of reasons (to be discussed below or on another occasion), but was more favorably received in botanical research, leading in particular to a number of detailed studies of high altitude conifers by the Swiss [especially studies associated with C. KàƒÆ’à‚⵲ner]. Interestingly a Walter Ammann is a coauthor of Hattenschwiler et al, 2004, “Atmospheric CO2 enrichment of alpine treeline conifers” [I wonder if he’s related to Caspar?] I’ll get to these articles on another occasion; I’m just noting this line of developments for now.

One line of criticism on the dendro front, starting with Kienast and Luxmoore [1988], was that they were simply unable to replicate anomalous late 20th century growth in high-altitude conifer chronologies. I’ve probably paid insufficient attention to date to this line of evidence, but it needs to be looked at squarely, prior to accepting Rob’s composite at face value. I had noticed some time ago in passing that the HS-ness of Graybill’s high-altitude North American sites was substantially higher than the HS-ness of the other high-altitude North American sites, but didn’t pursue the point.

But the minute that you pause and think about it, it is important: in our discussions of bristlecones, we’re not just talking about bristlecones, but site chronologies collected by one author (Graybill), who was attempting to prove a point about increased growth. One needs to show that Graybill’s results are consistent with those of other authors on the same material. Here one would like to see an update on the classic bristlecone sites, but little has been published in nearly 20 years. Hughes did an update at Sheep Mountain in 2002, but none of the results have seen the light of day.

Salzer and Kipfmueller updated San Francisco Peaks AZ, which was a Graybill site – but curiously about the only bristlecone site with no HS-shape. Unfortunately Salzer and Kipfmueller have not archived their measurement data, so it’s hard to explain the radical differences between the Graybill result and S and K result (maybe I’ll re-visit this on another occasion.)

Kienast and Luxmoore 1988
Kienast and Luxmoore [1988] was one of the first responses to the Lamarche et al [1984] hypothesis of increased ring width due to CO2 fertilization. They denied that there was any significant increase of ring width ( a position later held by Schweingruber).

They studied 34 sites on transects in 4 different regions, one of which was Colorado. Each transect went from the dry lower border to the upper border. They stated that only 8 of 34 sites had even somewhat anomalous post-1950 growth and none of the 8 met the Lamarche et al [1984] conditions. They stated that the increase coincided with favourable climatic conditions in 4 cases and in the remaining 4 sites, the increase in ring width exceeded the expected CO2 fertilizing effect as determined from seedling experiments. Their conclusion was that the CO2 effect was unproven.

In their Colorado transect, only one site had enhanced growth – a lower border site, not an upper border site. Among the Kienast and Luxmoore sites said not to show enhanced growth are two high Colorado Engelman spruce sites (Arapahoe at 3400 m; Niwot Ridge at 3320 m). So an obvious back-tracking question is: did Graybill collect any Engelman spruce and how do they compare with Kienast/Schweingruber? Similarly, did Schweingruber collect any limber pine or bristlecones in Colorado and how do they compare with Graybill? Which sites are used in MBH98?

Jacoby and D’Arrigo 1989
Jacoby and D’Arrigo 1989 articulated a third point of view: that there was increased growth (contra Kienast and Luxmoore), but that the increased growth was due to climatic factors, not CO2 fertilization (contra Lamarche). The controversy was rather a triangle. Jacoby and D’Arrigo 1989 was a seminal multiproxy article and its reconstruction (as extended by D’Arrigo and Jacoby 1992) became a mainstay of the multiproxy world.

I’ve posted about the Jacoby collection from time to time (see right frame category Jacoby). Two points off the top bother me about the Jacoby and d’Arrigo collation: they collected 36 sites and selected only the 10 “most temperature sensitive” and did not even archive the results from the other 26 sites. Some of their collecting appears to overlap with Schweingruber, but no codex has ever been published. Second, the Jacoby 10 sites all have southern exposure, as the northern exposure sites do not share the common “signal”. This bothers me as one wonders whether some sort of insolation effect e.g. cloudiness might be confounding results with only southern exposure sites.

Using their chronologies and local temperature histories, Jacoby and d’Arrigo then carried out a variety of statistical analyses, including the principal components followed by regression (in that sense, anticipating MBH). For all the bellyaching by some blog readers about the right of non-climate scientists to comment on articles by climate scientists, the salient arguments in Jacoby and D’Arrigo 1989 are entirely statistical; one does not need to have drilled cores to comment on that. Discussing the statistical procedures of Jacoby and D’Arrigo 1989 is a long column in itself (and probably worth doing). For now, I merely mention the following, which is a little bit worrying:

“the low-frequency variance and autoregressive properties of the two sets of time series, tree rings and temperatures, do not conform to the theoretical assumptions of standard statistical tests for significance of regression results.”

This observation remains valid 9 years; it obviously remains a problem with MBH98. To cope with this, Jacoby and d’Arrigo also did simulations to provide new benchmarks. I’m not going to examine these simulations today, but it’s obviously something that should be done.
The conclusion of Jacoby and D’Arrigo 1989 was a temperature reconstruction, showing elevated 20th century values (the reconstruction going from 1671 to 1973.) They stated:

“In the eleven individual chronologies the recent increase in growth over the period of increasing atmospheric CO2 is more obvious and universal then the earlier (1700s) increase. Our NH reconstruction through 1973 (Figure 1, with instrumental data added through to the present — another splice) thus supports the hypothesis that the current warming trend has exceeded the level of natural climate variability, at least over the past several hundred years….There is as yet (through 1973) no evidence of any direct effects of CO2 fertilization at these northern sites (Lamarche et al 1984) (Figure 6). This may be due in part to severe nutrient limitations in arctic ecosystems (Oechel and Riechers 1986), (Figure 6)

Now their Figure 6, mentioned above, illustrated the residuals, purporting to show that the residuals were random. I did not find their statistical procedures very meaningful. The data sets used in this article ended in the 1970s and early 1980s. The measurement data has been archived. In most cases, this represents the most recent archived measurement information from Jacoby and d’Arrigo (but stop the presses, 14 Alaska sites from the Seward Peninsula have just been archived) — another topic.

They did not discuss Kienast and Luxmoore 1988.

Schweingruber et al 1993
Next Schweingruber et al [1993], et al including Briffa, reported on a total of 69 sites at the North American treeline – 25 sites collected in B.C., Yukon and Alaska in 1984 and 44 sites collected in Canada from Yukon to Alaska in 1989. Like Kienast and Luxmoore, Schweingruber et al. also concluded that there was little evidence of anomalous growth. In the acknowledgements, it is reported that “Gordon Jacoby jointly selected and sampled many sites during the 1989 field season.” Two increment cores were collected from 12-15 trees per site. 34 sites were Picea glauca, 24 P. mariana, 4 P engelmannii and 3 P sitchensis and one larch.

“Figure 10a,b shows the MXD and TRW chronologies for each major region plotted from AD1800onwards. ..These curves indicate that no recent anomalous growth increases have occurred. Previous work (Jacoby and d’Arrigo 1989) has highlighted significantly increasing ring-width growth of some trees. This previous work was concerned with severely stressed trees growing the forest-tundra ecotone. Selected sites and trees at these locations, with particular ecology and aspect, may exhibit a sensitivity to temperature variability representative of larger climatic regions (G. Jacoby per comm.). Our results, along with other recent work (D’Arrigo et al 1992) indicate that increasing tree growth through the 20th century is not characteristic of the wider North American boreal forest.

Over recent decades, the regional chronologies described here do not exhibit any clear increasing growth tendencies that might be expected to result as a consequence of the anthropogenic environmental modifications or “natural” climate change.

As to the correlation of ring widths to temperature, they reported:

“By comparison, the ring width-related variables appear to be poorly correlated with temperature. Certainly LRW displays apparently random insignificant associations. TRW (and ERW) display mode consistently positive associations for the months of June through September and more particularly in the Gleichlaufigkeit values, with the June values (barring the WINNIP series) displaying consistently high values.

Graumlich 1991
Graumlich 1991 is a criticism of Lamarche et al [1984] and Graybill [1987] from the Kienast and Luxmoore angle. She looked at 5 subalpine conifer sites in California near the bristlecones: 3 foxtail pine — the bristlecone cousin/brother, one lodgepole pine and one juniper. She reported that, at 3 of the 5 sites, their 20th century growth could be modeled adequately as a function of climatic variation (considering both temperature and precipitation). This is again a statistical argument and a number of questions occur to me as to whether she has overfit the models. Unfortunately, no data is archived or available.

None of the 5 chronologies illustrated in her Figure 5 (West Tyndall Foxtail; West Tyndall Lodgepole; Bighorn Plateau; Crabtree; Kaiser Pass) visually show anomalous 20th century growth, although all 5 end on an uptick. Graumlich also notes problems with the data meeting regression assumptions:

I have chosen to retain the autocorrelation within the data set despite the fact that it could be removed by prewhitening because preliminary analyses indicated that prewhitening reduces the upward trend in many of the tree ring time series. Prewhitening would thus remove that feature of the time series of most interest for this study. As an alternative to prewhitening, the residuals from the growth/climate regression models were tested for autocorrelation as part of a general strategy to test for violations of the assumptions underlying ordinary last squares regression.

Graumlich pointed out the possibility of a temperature-precipitation interaction “in which drought stress limits growth in years of high winter precipitation and cool temperatures limit growth in years of high winter precipitation. While the contribution of precipitation in governing growth of subalpine trees in the southern Sierra Nevada and the nearby White Mountains has been recognized (Lamarche 1974, Scuderi 1987) the important distinction that the effects of temperature and precipitation on growth are nonlinear and multiplicative rather than linear and additive has not been fully appreciated.

Graumlich distinguished her results from LaMarche and Graybill by the following alternatives (1) their sites are less arid, and if CO2 fertilization is due to increased water use efficiency then effects would be more pronounced in more arid environments; (2) strip bark morphology characterized Graybill sites and possible interaction with tree morphology; (3) site differences in soil nutrients may be a factor; (4) Lamarche’s exclusion of climate as an explanation was based on linear analysis, while Graumlich considered interaction term.

Graybill, Donald A. 1987. A network of high elevation conifers in the western US for detection of tree-ring growth response to increasing atmospheric carbon dioxide. in G.C. Jacoby and J. W. Hornbeck, editors, Proceedings of the International Symposium on Ecological Aspects of TRee-ring analysis, U.S. Department of Energy Conference Report DOE/CONF-8608144.

Graumlich 1991, Subalpine tree growth, climate and increasing CO2: an assessment of recent growth trends. Ecology 72, 1-11.

Jacoby, G. and R. D’Arrigo, 1989. Reconstructed Northern Hemisphere annual temperature since 1671 based on high latitude tree ring data from North America, Clim Chg 14, 39-59.

Lamarche, V, Graybill, Fritts and Rose, 1984. Increasing atmospheric and carbon dioxide: tree ring evidence for growth enhancement in natural vegetations. Science 225, 1019-1021.

Kienast, F. and R. J. Luxmoore, 1988. tree ring analysis and conifer growth responses to increased CO2 levels. Oecologia 76, 487-495. Schweingruber, F.H., K.R. Briffa and P. Nogler, 1993. A tree-ring densitometric transect from Alaska to Labrador, Int J Biometeorology 37, 151-169


  1. Willis Eschenbach
    Posted Apr 6, 2006 at 11:24 PM | Permalink

    Excellent and interesting. In particular, I liked the quote from Graumlich (emphasis mine):

    While the contribution of precipitation in governing growth of subalpine trees in the southern Sierra Nevada and the nearby White Mountains has been recognized (Lamarche 1974, Scuderi 1987) the important distinction that the effects of temperature and precipitation on growth are nonlinear and multiplicative rather than linear and additive has not been fully appreciated.

    When, a while ago, you started the thread about the upside-down quadratic nature of the temperature-ring width relationship, I said that that factor alone doomed the “science” of dendrochronological temperature reconstruction using the current methods. People replied that I was too hasty, that I couldn’t draw that conclusion, not enough evidence.

    I have seen nothing since to change my mind. Trees are not thermometers. If they were, we wouldn’t need the network of ground stations. She’s right, the distinction is not fully appreciated … even by her, it seems …

    Is there, anywhere, a study that justifies the field? Is there a study that explains how with a pair of multiplicative, non-linear factors like water and temperature we can tease out the temperature without having it all distorted beyond recognition by the two entangled, upside down quadratic relationships?


  2. jae
    Posted Apr 7, 2006 at 6:34 AM | Permalink

    Re #1, your question at the end. I’ve been asking that question for over a year, and still no good response from the experts. After reading Steve’s great summary here, it looks like even those within the dendro community don’t agree on a growth-temperature relationship. If the experts are arguing about it, then there cannot be a very clear proven fundamental relationship. BTW, it looks like there’s a lot of cherry picking going on right from the start–selection of trees to core. Wonder how many cores were discarded in the field, because they didn’t “look right.” Maybe I’m being overly suspicious, though….

  3. Steve McIntyre
    Posted Apr 7, 2006 at 7:15 AM | Permalink

    #1. I’ve got quite a bit more to come on this topic, bringing some of the lines up to date. Willis, here’s a quote from Hattenschwiler et al [New Phytologist 2002] in which they also use the word “tease out” in the same context and with respect to the same articles:

    Nonetheless, it remains difficult to tease apart all the potentially influential and interacting factors, such as changes in forest management, nitrogen deposition and recently increased temperatures (Kienast & Luxmoore, 1988). For example, the data set of La Marche et al . (1984) was found to be confounded with rainfall history (Graumlich, 1991).

    #2. I’ve got some interesting quotes still to come. If you look through the tree ID numbers in some key sites, there are missing ID numbers. I’ll discuss this some time in the next month.

  4. Paul Linsay
    Posted Apr 7, 2006 at 8:09 AM | Permalink

    The relation of ring width to temperature and other growth factors is never going to be resolved by field studies, there are so many uncontrolled variables that they can argue forever. In normal science it would be resolved by controlled experiments with trees in a greenhouse.

    I can’t find the citation, but I made exactly the following point on this site a while ago,

    the effects of temperature and precipitation on growth are nonlinear and multiplicative

    This makes controlled experiments even more important because the function relating tree ring width to water, sunlight, temperature, … is going to be so complicated.

  5. TCO
    Posted Apr 7, 2006 at 8:34 AM | Permalink


    Very thoughtful review of the literature.

    (Segue:) I wonder if part of the problem with the field has to do with the way feildwork is done and who does it. Maybe this field attracts small-money professors and “students who like getting outdoors” and then they go collect a few cores and publish. But given the huge variability of living samples, they are not gathering enough data and are not doing enough controls.

  6. agesilaus
    Posted Apr 7, 2006 at 8:39 AM | Permalink

    Has it never occured to these people that they should pick out a number of sites, install continious weather monitoring for temp, precipitation, insolation and whateever other factors might be involved. Then they should do annual cores and try to correlate the data.

    If they had done that back in the mid 90’s they’d have a decade of real data to work with.


  7. BradH
    Posted Apr 7, 2006 at 8:40 AM | Permalink

    Re: #1

    Is there, anywhere, a study that justifies the field?

    There can’t be, Willis. The “field” defies more principles of scientific uncertainty than your could poke a stick at.

    Why don’t we all try and create a list? I’ll start off with a few:-

    1. Unknown boundary conditions – what are the acceptable upper and lower limits of temperature/humidity/CO2 for reasonably productive survival of most species?

    2. Contributing variables – what are the variables which contribute to temperature fluctuations? No guesses allowed – if you want to promote a variable as important, provide an experiment to back it up.

    3. Use of statistics – we have reliable tree ring widths, yet we have no reliable past temperature or rainfall measurements over the period we are discussing. We are using very time-restricted current data to not only extrapolate into the future, but to extrapolate into the past. What confidence interval should be ascribed to such a “double extrapolation”?

  8. TCO
    Posted Apr 7, 2006 at 8:43 AM | Permalink

    Re6: Yeah, I asked that a while ago, too. 😦

  9. Steve McIntyre
    Posted Apr 7, 2006 at 8:44 AM | Permalink

    #6. There were weather stations in the White Mountains near Sheep Mountain and Campito Mountain from 1950-1980. That data was used by Graybill and Idso in concluding that climatic factors did not account for higher bristlecone growth.

    Curiously another one of Graybill’s bristlecone sites was from Niwot Ridge Colorado, which is about 35 miles from Boulder, has a meteorological station and an ecological station. I’m going to post up some information about Colorado sites and was collating some info about Niwot Ridge. No data on high-altitude Colorado tree ring sites has been archived in the past 12 years.

  10. Steve McIntyre
    Posted Apr 7, 2006 at 9:19 AM | Permalink

    #5. Tree rings don’t seem like small money to me. Look at this NSF announcement: http://www.nsf.gov/news/news_summ.jsp?cntn_id=100394

    Tree-Ring Laboratory Receives $5.5 Million to Study Climate Dynamics

    June 1, 2004

    ARLINGTON, Va.”¢’‚¬?The National Science Foundation (NSF) has awarded the Tree-Ring Laboratory of Lamont-Doherty Earth Observatory (LDEO), Columbia University, a $5.5 million grant to study one of the largest climate systems affecting the globe”¢’‚¬?Asian monsoons. ….The tree-ring reconstructions of Asian monsoon climate dynamics project is led by scientists Edward Cook, Rosanne D’Arrigo, Brendan Buckley and Gordon Jacoby, all of LDEO.

    About 2 weeks after this announcement (and then unaware of the award), I complained to NSF about various luminaries including Jacoby not archiving data and got blown off.

  11. Douglas Hoyt
    Posted Apr 7, 2006 at 9:22 AM | Permalink

    Isn’t the most serious problem that you have positive and negative responders growing right next to each other and these opposite responders are the same species?

    You can throw out the negative responders, but it would be like someone flipping a coin and throwing out the tails and then concluding that the coin had two heads.

    The correlation for all trees (none discarded) with temperature is close to zero, isn’t it?

  12. jae
    Posted Apr 7, 2006 at 9:33 AM | Permalink

    It’s becoming clear that the whole concept of using trees to discern temperature is bogus science. I am sure some dendro guys are reading this blog (Dano, where are you?). Surely, they would be protesting if they had anything to say, since their whole house of cards is in jeopardy. Of course, they are probably taking the Mannian route and saying to each other, smugly, that only the published literature counts, and the “consensus” is on their side. Steve, from the looks of the reviews you’ve done so far, it doesn’t look like much of a consensus, LOL. It’s great you are taking the time to review the “refereed literature” on this subject.

  13. jae
    Posted Apr 7, 2006 at 9:53 AM | Permalink

    You know, if I were supervising a graduate student working on a PhD in dendroclimatology and doing a “climate reconstruction,” I wouldn’t even look at a dissertation that did not have a lengthy review of the literature, similar to what you are doing, Steve. It is truly amazing if none of these scientists have done this, when their whole raison d’etre depends on it!

  14. JerryB
    Posted Apr 7, 2006 at 9:53 AM | Permalink

    Perhaps this post, and those to follow on this theme, might be called: tempodendro, portraits of a train wreck in slow motion. 🙂

  15. Peter Hearnden
    Posted Apr 7, 2006 at 9:55 AM | Permalink

    Re #12, it may be clear to you but is it possible, just possible, that you’re getting just one side of the argument here on CA and accepting that one side as right? That’s how it seems to me.

    This thread is slipping towards ‘we declare victory ‘cos you wont fight on our ground’ triumphalism.

  16. TCO
    Posted Apr 7, 2006 at 10:05 AM | Permalink

    I think that students in dendro have to include lit reviews in chapter one of theses and that papers tend to cite lots of earlier work. The question is not, are people totally blowing off old work, but is it more of a “touch base” type of citation which ends up being house of card upholding rather than serious considerations of the state of knowledge in the field, of the quality of foundational work, and of how different studies argue against each other.

  17. TCO
    Posted Apr 7, 2006 at 10:07 AM | Permalink

    BTW Steve,

    You can order people’s theses usually. They cost a few bucks for a microfiche copy. May even be electronic now. sometimes, there is more room for explanation in a thesis. Also, you may find some of the “excluded” data or studies that were not published.

  18. TCO
    Posted Apr 7, 2006 at 10:14 AM | Permalink


    From your interactions at NAS and over the years, what is your impression of the literarature knowledge of the participants? How would you compare to your own command of the literature?

  19. jae
    Posted Apr 7, 2006 at 10:21 AM | Permalink

    Peter: you may be right, but where ARE those guys? They need to speak up, now.

    #16. I agree, but a good literature review is a complete analysis of both sides of the issue, like Steve is doing. And a worthy dissertation starts with a good literature review.

  20. ET SidViscous
    Posted Apr 7, 2006 at 11:10 AM | Permalink

    Hey Peter. You might want to give yourself a wack, you seem to be stuck and repeating the same things over and over regardless of the discusion.

    No one says it’s over, evidenmce is mounting, and will take a good explanation, on one matter and one matter only.

    No one is shutting the lights off and locking the doors.

  21. Steve McIntyre
    Posted Apr 7, 2006 at 11:25 AM | Permalink

    For an example, here’s a recent dissertation http://cla.umn.edu/physgeog/kurt/research/reprints.html by Kipfmueller of Salzer and Kipfmueller, cited recently by Rob Wilson. appendix A discusses climate-growth issues without mentioning of the references that I put in my first installment or some others that I’m going to mention. He does mention Lamarche and Stockton 1974 without Lamarche et al 1984 or Graumlich 1991, for example.

  22. ET SidViscous
    Posted Apr 7, 2006 at 11:35 AM | Permalink

    The first thing you notice looking at figure 2 on the temperature reconstruction, is that while it tracks with temperature, it doe not reflect extreme divergences, i.e. 1993, 1980, 1960 1937-1940, 1920, 1915.

    A. This shows the negative relationship as temperature exceed a certain level (Upside down quadratic).

    B. That an tree ring re-construction is going to be muted to extremes. Vis-a-vis MWP and LIA, so that when one grafts on an instrumental record to the end, the extremes are seen and the earlier extremes are muted in the tree rings.

    This could lead some people to make un-substantiated remarks like the current climate is warmer than anytime in the last 100/2000 years.

  23. Brooks Hurd
    Posted Apr 7, 2006 at 12:00 PM | Permalink

    Except for carefully controlled laboratory experiments, dendrochronology, like most science, unvolves multiple variables. Steve has summarized sufficient papers to show that authors of dendro studies are aware of the variables and do not understand the interactions. This is not surprising, since understanding how multiple varialbles effect any result is problematic in any field with which I am familiar.

    Steve, it appears that there is very little archived dendro data. With limited archived data and so many variables, I suppose that it should not be surprising that certain authors cherry pick their data to create a trend.

    When authors like MBH, et al cherry pick dendro studies which have cherry picked dendro data and use them to show 1,000 year temperature trends, they have stacked tenuous assumptions upon tenuous assumptions. The use of dendro reconstructions as temperature proxies appears to me to be a huge house of cards. Perhaps Rob could correct me if I am wrong, but I suspect that if one added the dendro errors to MBH’s (or other author’s) reconstruction errors, any trends would be so small compared to the total error that they would be meaningless.

  24. ET SidViscous
    Posted Apr 7, 2006 at 12:06 PM | Permalink

    Steve M

    Couldn’t find any of the threads discussing this, but I thought you might find this of interest from a getting data viewpoint.


  25. jae
    Posted Apr 7, 2006 at 12:08 PM | Permalink

    re: 21. What a quick, hokey literature review in that dissertation. If I were this guy’s major professor, I would have required a much more extensive, critical literature review, unless he was able to cite someone who had done such a critical review. It just amazes me that nobody seems to have done so. Good scientists HAVE to be skeptics. Anyone can point to a series of studies that justify one side of a position. And you can certainly see the bias in the Introduction.

  26. Brooks Hurd
    Posted Apr 7, 2006 at 12:21 PM | Permalink

    Re: 15, Peter,

    The error in the underlying data do not simply overlay the error of the reconstructions. The dendro data errors cause a dramatic increase in the total error of any reconstructions based on dendro data. Each proxy used in a reconstruction has its own errors. To calculate total error, one must combine the errors of the individual proxies with those of the reconstruction. This assumes that all the individual errors have been calculated in a statiscally sound fashion.

  27. Steve McIntyre
    Posted Apr 7, 2006 at 12:26 PM | Permalink

    #23. Brooks, there is a vast amount of archived dendro data. However, the archiving is not complete and very often, the multiproxy studies use unarchived information. In some cases, where they do use archived data (e.g. Esper et al 2002), there are no data citations and the information in the article does not enable one to deduce what data was actually used.

  28. TCO
    Posted Apr 7, 2006 at 2:27 PM | Permalink

    I thought the guy’s lit review was pretty good. I think of dissertations as pass/fail anyhow. What really matters are your papers. You should have seen my dissertation. I wrote it in 10 days (had previously published the bulk of it though).

    Anyhow, he is kind of looking at a sub-problem (fire versus climate) and not climate itself. So he is not going to resolve all the issues in climate recon themselves. That said, he might be building on a house of cards.

    Anyhow, it was a lot better than my lit review in my thesis. And I think I had a great grad student career.

  29. Steve Sadlov
    Posted Apr 11, 2006 at 12:18 PM | Permalink

    Note to Peter H. Let’s go back, wayyyyy back. To perhaps Grade 4. This is a quadratic equation. Now class, can you tell me what sort of shape this equation has? That’s right. It is shaped just like the letter “U!”

    Now, what happens if we reverse the sign of this equation.

    That’s right, class, it looks just like an upside-down letter “U!”

  30. Dano
    Posted Apr 11, 2006 at 1:49 PM | Permalink


    I said that that factor alone doomed the “science” of dendrochronological temperature reconstruction using the current methods. People replied that I was too hasty, that I couldn’t draw that conclusion, not enough evidence…I have seen nothing since to change my mind. Trees are not thermometers. If they were, we wouldn’t need the network of ground stations.


    Steve has summarized sufficient papers to show that authors of dendro studies are aware of the variables and do not understand the interactions. This is not surprising, since understanding how multiple varialbles effect any result is problematic in any field with which I am familiar.

    Bold, knowledge-shattering statements, all!

    I have set up a method for would-be Galileos to test the courage of their convictions – shared widely here – with actual dendro people who do this for a living.

    Would any would-be Galileos like to test the courage of their convictions with dendro ppl? I am willing to act as the moderator and watch some folk test their convictions against folk who do dendro for a living.

    Who’s game?



  31. Hans Erren
    Posted Apr 11, 2006 at 2:08 PM | Permalink


    Come across a resampling study that confirms the hockeystick?

    Because that’s the issue here.

  32. Steve McIntyre
    Posted Apr 11, 2006 at 2:17 PM | Permalink

    Dano, I’ve written many threads here on tree ring studies. I do not agree with every comment that’s made here on one side or the other. If any "professionals" wish to participate, they are welcome. If I’m wrong about anything that I’ve posted about tree rings, I’d like to know and modify my position accordingly.

    In some cases, there’s a disconnect between parts of the literature. For example, Graumlich 1991 can be cited as an example of someone pointing out quite clearly the possibility of nonlinear interactions between temperature and precipitation. I’m sure that this would be the position of most botanists – Larson of Guelph emphasized the extreme nonlinearity of botanical phenomena to us. You can agree with that without endorsing he data mining of MBH98-MBH99.

  33. Dano
    Posted Apr 11, 2006 at 2:28 PM | Permalink


    Unless you are, for some reason, trying to distract away from the topic, let me remind you that the topic of this post is stated in the first para. and the thesis of this post is stated in the third.




  34. Dave Dardinger
    Posted Apr 11, 2006 at 2:46 PM | Permalink


    Since you have such an in with the tree-ringers that you’d be willing to moderate on one of their boards, why don’t you go to such a board and induce a few to come here and state their side of the issue. Indeed if you’d send a messaged to Steve M directly I bet he’d be willing to let them blog their own thread. For any of us to go to another board would be useless. People here wouldn’t be able to see what happened.

  35. Greg F
    Posted Apr 11, 2006 at 3:00 PM | Permalink

    I am willing to act as the moderator …


  36. Steve McIntyre
    Posted Apr 11, 2006 at 4:32 PM | Permalink

    #33. touché.

    What I was responding to in the post were Rob Wilson’s comments, which were based on material hot off the press. He could have mentioned earlier articles but didn’t. The context isn’t very clear and I see why a reasonable reader could take it as being a broader statement than it is; I’ll re-state the point to make it clearer.

  37. Dano
    Posted Apr 11, 2006 at 5:44 PM | Permalink


    It’s an invitation for some of folk who make the more outlandish statements, Steve.


    I’m willing to moderate on their board. Someone goes to them. I’ve set up an ID to do so & passed on the intent of the ID to the owner.

    They have no need to state their ‘side’ of the issue, as they publish their statements already.

    (Of course, some members are students but presumably they would not respond unless doc/postdoc.)

    Anyway, the point being: either you have the courage of your convictions to state to professionals that, say, tree rings are no good for [x, y, z] or you don’t.



  38. TCO
    Posted Apr 11, 2006 at 5:48 PM | Permalink

    Big Dan, I’d be glad to go over there and chat with the folks. I’m just a maggot compared to Steve, but if you will let me into the big leagues, I’ll take the plate.

    P.s. I invited Fritts to stop by here a couple days ago. And Millar before that.

  39. Greg F
    Posted Apr 11, 2006 at 6:06 PM | Permalink

    I’m willing to moderate on their board.

    Is this some secret society? Do you need to know a secret handshake? Just post a link to the discussion board and quit the nanny crap.

  40. jae
    Posted Apr 11, 2006 at 6:08 PM | Permalink

    I’m game, Dano.

  41. TCO
    Posted Apr 11, 2006 at 6:33 PM | Permalink

    No, Jae, you’re not up to it. I don’t want those guys getting a bad impression of us.

  42. Dano
    Posted Apr 11, 2006 at 6:48 PM | Permalink


    I have deadlines/appointments thru Thursday so Friday afternoon looks good to start; I may be out of town Thurs. afternoon. Figger out a concise argument and question(s) ’til then.

    Ground rules, maybe more soon as I see the radar indicates improvement and I can get a ride in before dark:

    – When I get more time (tomorrow afternoon, likely), I’ll give URL to look over. I also set up a new e-mail for purposes of this moderation, for receipt only.

    – this is a site for professionals. I won’t transfer over anything unprofessional.
    – I will not edit text, save for deleting FUD phrases.
    – Stay OT in thread.
    – No use of FUD phrases. You can use them, but I’ll cut them out.
    – I won’t do this 8x/day, so structure your question such that it does not need 23 follow-ups so as to be understandable. I suggest conferring amongst yourselves {I’m not suggesting using Steve’s bandwidth, John A). I suggest structure something along the order of ‘Recent findings (cite) show that there are issues with tree ring width and temp and that dendro is a poor proxy indicator of temp/climate (whatever the assertion is), because of x, y, z. Can anyone address these concerns?’.
    – I’ve never done this before, nor seen it done, so I really have no idea of what to do other than this, so if there’s a question we’ll have to figger out some way of working it out, and I’m sure John A doesn’t want all that on here. Patience.



  43. Pat Frank
    Posted Apr 11, 2006 at 7:51 PM | Permalink

    #42 – “this is a site for professionals. I won’t transfer over anything unprofessional.”

    I saw no link to any blog site given in any of Dano’s posts in this thread. Instead, we get the above “ground rule.” So, what Dano is apparently offering is not a free discussion with dendro professionals, or even a moderated discussion. He’s apparently offering to transfer critical comments over to some group of dendro people and then, presumably, transfer their replies back.

    I dislike those ground rules. If dendro folks want to take the waters, I’m happy to talk freely with them. I’m not happy to have remarks passed back and forth through a third party. They’re free to ignore any comments or questions they consider “unprofessional” without needing anyone’s protection, just as are the rest of us. Both John A and Steve M have been very fair and open to critical inputs here. No one need fear censorship or personal attacks. Sorry, Dano. Paternalism, protective filtration, and condescension don’t cut it.

    David Stockwell has set up his own blog here. If you don’t like Steve M’s climate audit site, maybe David would agree to host a free discussion there that would include your dendro professionals. Then you’d be free to service the deadlines/appointments of your own schedule, which seems very busy, and the rest of us could have an open conversation without protective filtration.

  44. TCO
    Posted Apr 11, 2006 at 7:59 PM | Permalink

    Where’s the site? I’ll go over.

  45. TCO
    Posted Apr 11, 2006 at 8:17 PM | Permalink

    Wonders of google:


    Looks like this is the place to start the invasion discussion. 😉


    (FAQ for this listserv: ITRDBFOR@LISTSERV.ARIZONA.EDU)

    Here is more of a post-ARPA bbs: http://forums.hypography.com/earth-science/5810-new-thought-global-warming-2.html (although if you read the stuff, they seem pretty lame…about Lynn from RC level of discussion.)

  46. TCO
    Posted Apr 11, 2006 at 8:20 PM | Permalink

    Damnit John (and Steve). F***ing Nazi Karma is eating my posts. I just researched and posted the urls of the sites we should terrorize while DanO is out biking (before he can warn them) and it ate my stuff. I think if it sees too many http’s, it deletes stuff. Grrr!

  47. TCO
    Posted Apr 12, 2006 at 6:48 AM | Permalink

    I’m in email conversation with a tree-ring-heavy prof, trying to induce him to come by here and participate/weigh in. DanO would be proud.

  48. Dano
    Posted Apr 12, 2006 at 4:04 PM | Permalink


    Sorry, Dano. Paternalism, protective filtration, and condescension don’t cut it.

    Don’t like the show, change the channel.

    All are free to invite folk over to Stockwell’s site, which by looking at it is milder and less rife with hyperbole, thereby making it more attractive to academic-types. Test the Galileo-like assertions there.



  49. TCO
    Posted Apr 12, 2006 at 4:36 PM | Permalink

    We’re going in, DanO. STFB!

  50. jae
    Posted May 2, 2006 at 1:15 PM | Permalink

    Anyway, I think the jury is still out regarding whether there really is an increase in surface temperatures. Wish I had time to really look into the instrumental data. Given that so many locations are showing a cooling, I wonder if the UHI effects are much greater than most people think. I’m gonna posit a theory that we are entering the next ice age. We are long overdue, from what I’ve read.

  51. Dave Dardinger
    Posted May 2, 2006 at 2:00 PM | Permalink

    What bugs me about UHI skeptics (by which I mean those who think there is no such thing), is that they go to such great lengths to disprove something which is so obviously true. Everyone knows it’s warmer in cities than in the country. And everyone knows that cities have been growing enough to at least keep up with population growth. Therefore the degree of UHI for a given city is nearly certain to have increased, yet we get this nonsense like the article a year or so ago that there can’t be UHI because the authors found windy nights to be just as warm as cool ones. That hardly takes any thinking to debunk, but we still see it quoted to us as irrefutable proof that UHI doesn’t exist.

  52. ET SidViscous
    Posted May 2, 2006 at 2:11 PM | Permalink

    Actually when you think about it UHI is almost a necessity, for three reasons.

    1. Ideal temperature. Humans are always searching for a comfortable temperature. Hence when it is cold they turn on the heat. This warms the buildings (And hence the outside) as well as all the warm exhaust from the vents. When it is hot, they turn on the AC, this is primarily because with the exception of row house it is impossible to get cross ventilation in urban apartments. The AC work at cooling the buildings by exhausting heat to the out of doors. So at any temperature deviation from ideal (let’s say 71) urban dwellers are creating heat in some form. Whereas rural dwellers attempt to do so, due to their low numbers the effect is low.

    2. Wealth. Urban dwellers tend to be wealthier than rural dwellers, so they can spend more money on temperature regulation (no this is not true worldwide, but certainly in developed countries)

    3. Materials. Few cities are built of wooden materials, most are heat retaining materials like concrete stone, and steel. The argument against them retaining heat is easily disproved. If you heat in the woods with a fire, it’s beneficial to do so against a large rock as it will retain the heat longer, and radiate after the fire has burned out. For much the same reason they make radiators out of steel (or more likely cast iron) as once warmed, the cool relatively slowly.

  53. Douglas Hoyt
    Posted May 2, 2006 at 2:14 PM | Permalink

    I think that windy nights and calm nights are equally warm because UHIs are so strong that even windy conditions do not cool the cities down. What other explanation could there be?

  54. JerryB
    Posted May 2, 2006 at 2:34 PM | Permalink

    Regarding Arctic warming as a trend, vs got warmer in 1976 and roughly continued so, see Sue Ann Bowling’s http://climate.gi.alaska.edu/Bowling/FANB.html and her 1990 article to which it links.

    Then look up the PDO shift of 1976, of which Bowling was not aware when she wrote those articles.

  55. Mark
    Posted May 2, 2006 at 3:17 PM | Permalink

    I’m looking at it JerryB, but not in-depth at the moment as I actually have to do what I’m paid to do!


  56. Jeff Norman
    Posted May 2, 2006 at 6:31 PM | Permalink

    Mark said:

    Antarctica, however, is cooling with the exception of the area immediately surrouding the peninsula which sticks out into the southern Pacific.

    Mark, when you have a moment, check your geography.

    Regarding Arctic warming, I have been wondering about the land use or rather sea use impact on regional warming. Consider all the ecotourist and scientific expeditions to the pole on all those ice breakers…

    Probably trivial.

  57. George
    Posted May 2, 2006 at 7:29 PM | Permalink

    Re #51: Dave, it bugs me as well when UHI is denied. The Metromex study in the 70s (St Louis) proved that it exists. Studies in other cities (Atlanta, Salt Lake, LA, etc.) have confirmed it. EPA has a web site which describes it in detail:


    “This phenomenon describes urban and suburban temperatures that are 2 to 10°F (1 to 6°C) hotter than nearby rural areas.”

    And if you have an area which is changing from rural to suburban or urban (many world cities), guess what? Rising temperatures! Not AGW, but AUHI.

  58. jae
    Posted May 2, 2006 at 10:11 PM | Permalink

    Folks, I’m glad to announce that I have moved on. Considering the divergence problem with tree rings and the realities of the surface air temperature records, I think I can prove that we are entering a period of GLOBAL COOLING! Using Mannian logic and methods, it should be easy to prove. I just have to find the right groves of trees…..

  59. Posted May 2, 2006 at 10:24 PM | Permalink

    ET SidVicous,

    Wouldn’t all the tarmacadam and roof tiles affect the albedo of cities, cause them to absorb more of the incoming solar radiation during the day that would otherwise have been reflected back into the atmosphere/space, and re-radiate it at night?

    Also, whenever I’m stuck in traffic I can typically see heat shimmering off the cars in front of me (and indeed my own). Cars are what,

  60. Posted May 2, 2006 at 10:27 PM | Permalink

    Ugh, my next word was “less than fifty percent” (using symbols) and it appears the post got cut off there. I guess it thought the less than sign was a tag.

    Anyway I went on to say that cities must be bit sources of heat, and surely that would be visible to IR. And of course, when I hit google, this was the first link I found.

    I think the pictures speak for themselves.

  61. ET SidViscous
    Posted May 2, 2006 at 10:59 PM | Permalink

    Sure. There’s a bunch of things on both sides of the ledger (larger water circulation through pipes under the cuty will also take away heat). but that pretty much comes under Materials and will in the end add to averages.

    Big skyscrapers are wonderful. Nice big greenhouse (And real ones, not imprecise metaphor ones) heat up nice in the summer. Then you have to evacuate the heat with Big old AC’s. That there generates a bit of heat. And if you think SUV’s are a source of CO2, you should see the power bill on a big skyscraper, and they don’t even have Cruise control or spinners.

  62. ET SidViscous
    Posted May 2, 2006 at 11:07 PM | Permalink

    THe thing is the AGW’ers will say, “That is all taken into account” But that’s the bit. Is there a correction? Sure there is. Is it enough? Who knows. Regardless of what people say, the 20th century increase is still minor, when UHI is subtracted it only gets smaller.

    And the natural variance is still the biggest player by far, we could be heating more than we think (Natural variance is going lower) or actual anthropegenic effects are net cooling (natural variation more than +0.6C) That brings us full circle to the Hockey team who are really, more than anything, attempting to put a number on natural variation.

    The blade is less the story than the shaft. The blade is just the flashy one that gets the media attention, the shaft…

    Well it gets the shaft, per usual.

  63. jae
    Posted May 9, 2006 at 4:51 PM | Permalink

    Here is an interesting explanation of the effect of temperature on plant growth.

    Temperature and plant growth
    Temperature determines the rate of crop development and consequently affects the length of the total growing period of the crop. Growth starts at some minimum temperature (4-5°C). As temperature increases, rate of plant growth increases until an optimum temperature is reached. Mean daily temperature for optimum growth and tillering is between 15 and 20°C. The rate of growth will decline as the temperature rises above this otimum range. At the end growing season, growth will stop when air temperature falls below 5°C.

    It looks to me like trees, even at high altitude/latitude normally get the heat necessary to grow well. Growth in most trees, in fact, is probably decreased by too much heat. A small change in “average yearly temperature,” such as 0.6 deg. C over a period of 60-70 years is almost certainly not going to be reflected by tree rings. Assume there is a linear relationship between growth rate and temperature between 5 C and 20C. Then, a 0.6 C change represents only a 4% increase in growth over the full 70 years. I defy the dendro guys to pick up a 4% change in ring width or density over 70 years, especially on rings that are 1-2 mm in width–0.04*2 mm = 0.08 mm–pretty hard to measure, I think. And the yearly increase would be 0.08/70 = 0.001 mm.

  64. Paul Linsay
    Posted May 9, 2006 at 6:06 PM | Permalink

    #63. There are bound to be a number of errors and variables that make the measurement of ring width even harder. I’d guess that as the tree grows pressure from the outer rings will compress the inner rings some. Coring probably introduces errors by compression as well. Any drying of the tree will also produce unreproducible changes in ring width too. The experts here probably have a whole catalog of what can go wrong.

  65. Pat Frank
    Posted May 9, 2006 at 9:32 PM | Permalink

    #64, Paul, the pressure issue you raise hadn’t occurred to me. Leaves have a large internal water pressure, and there are instruments to measure that in the field. The pressure inside a tree cambium layer is likely very high, with the larger trees having the higher pressure. It’s discussed here, where a 60 foot tree develops 2 atmospheres of pressure at its top, in order to raise dissolved nutrients that high. When trees are cored, there is a loss of pressure in the core-wood. One might then expect a macroscopic expansion of the core as the cells relax. Presumably, the magnitude of the expansion will vary with the size of the tree within a species, and perhaps between species as well. Ancient snags, in contrast, will have already lost nearly all internal pressure. Presumably they will have both relaxed and shrunk due to loss of water. How large is all of this dimensional plasticity relative to growth-related variations in ring width, and how is it normalized out?

  66. Paul Linsay
    Posted May 10, 2006 at 6:58 PM | Permalink

    #65, Pat. Good question, I don’t have a clue. I simply wrote down my thoughts as an experimentalist about what might cause measurement error that would limit the validity of tree rings for quantitative questions.

    Another thing occured to me. Tree rings don’t seem to be highly uniform as can be seen from this picture of a bristlecone pine cross-section. So what’s the width of the ring? Is the ring growth rate constant all the way around? If the ring section at angle x is fast growing this year will it be fast growing next year or will that shift around the circumference of the tree from year to year?

    It would be real interesting to see the raw data on the tree ring widths and how that was massaged into data for the proxy calculations.

  67. Pat Frank
    Posted May 10, 2006 at 7:59 PM | Permalink

    #66, good point about asymmetric growth Paul. Here’s the picture of Mann + tree section that was linked in the thread about his Santa Cruz appearance. Mann’s tree section is asymmetric across the diameter, and cracked in several places too. Any proper ring width measurements would have to include multiple spots around the circumference on every single ring and take an average. I’d guess at least 6 measurements per ring, better 12, and perhaps best 36 (every 10 degrees).

    Someone on their toes in the field could develop the equivalent of the gel scanners used in biology and put tree sections on a spinning circular platen. The scanner would track the rings spinning beneath. Ring widths could then be measured all the way around and a true mean plus range determined. In fact, instead of widths, they could measure areas. Of course, they’d have to kill every tree they measured. Could be a problem, that. 🙂

  68. Steve McIntyre
    Posted May 10, 2006 at 9:21 PM | Permalink

    #67. speaking of non-symmetic, you should see the cores of cedars and bristleoones. They are wildly non-symmetruic.

  69. Paul
    Posted May 10, 2006 at 10:09 PM | Permalink

    Just keep saying “tree rings are thermometers…tree rings are thermometers…tree rings are thermometers…” You might actually come to believe it.

  70. jae
    Posted May 15, 2006 at 4:27 PM | Permalink

    Add to the asymmetry problem the problem of coring perpendicular to the rings, which is very hard to achieve, and which can drastically change apparent ring widths. This is one place where density makes more sense. But the bottom line, as I said in #63 is that the changes in growth due to temperature would be too small to measure, anyway. It’s just a crazy application of dendrochronology. Dendro guys need to stick to moisture proxies (which most of the ones they use probably are, anyway), where tree rings really do show measureable changes. Moisture is probably the most important and often limiting variable. Maybe there is some hope for isotopes in tree rings, but they would just reflect solar forcing.

  71. jae
    Posted May 23, 2006 at 3:59 PM | Permalink

    An interesting paper was presented at a TRACE Conference:


    Tree growth and climate in the Tatra Mountains

    Ulf Büntgen (1), David Frank (1), Ryszrad J. Kaczka (2), Anne Verstege (1), Tomasz Zwijacz-Kozica (3) and Jan Esper (1)

    (1) Swiss Federal Research Institute WSL, Zürcherstrasse 111, 8903 Birmensdorf, Switzerland
    (2) Faculty of Earth Science, University of Silesia, 60 Bedzinska 50, 41-200 Sosnowiec, Poland
    (3) Tatra National Park, Chalubinskiego42a, 34-500 Zakopane, Poland

    We aggregate 24 tree-ring width and 4 maximum latewood density chronologies from the greater Tatra region (Poland/Slovakia). The network comprises 1,183 tree-ring width and 153 density measurement series, and considers four conifer species (Picea Abies, Larix decidua, Abies alba, and Pinus mugo) from elevations between 800-1,550 m asl. Individual spline detrending is used to retain annual to multi-decadal scale information from the data. 20th century temperature and precipitation data from 16 grid-boxes covering the 48-50°N and 18-19°E region are utilized for comparison. The network is analyzed to assess growth/climate response as a function of species, elevation, parameter, frequency, and site-ecology. Twenty ring width chronologies correlate significantly with June-July temperatures, while the density chronologies reveal strongest response to the wider April-September season. Increasing precipitation response with decreasing elevation is observed. Climatic effects of the previous year are generally insignificant, while site elevation and frequency are evident. Correlations between summer temperatures and the annual growth rates of Larix decidua are lower than for Picea abies, although cyclic defoliation patterns of larch budmoth outbreaks are not distinguished. Principal component analysis elucidates five dominant eigenvectors from the network. The first principle component contains highest loadings from 12 Picea abies ring width chronologies and explains 42% of the network’s variance. The mean of these chronologies correlates at 0.62 (p

  72. TCO
    Posted May 23, 2006 at 4:52 PM | Permalink

    It seems that if you are taking multiple cores/tree, that you could do some math on the “within tree” variations and this should give you some idea of whether you are getting an accurate view of the overall RW. Some p, t, F, chi or something test. I mean if I take three measurements and they are all within 2% of the mean, that gives me a warm fuzzy. If I take 2 and get 50% variation, then I’m more worried as to whether I’m capturing the mean RW.

  73. jae
    Posted May 23, 2006 at 5:07 PM | Permalink

    72. TCO, One would not necessarily expect much uniformity in the cores, because of the non-symetrical (non circular) shape of many tree stems. Leaning trees and those with uneven weight distribution (more foliage on one side than the other) tend to be especially non symetrical, since the tree compensates by forming more wood–“reaction wood”– on the loaded side (in gymnosperms; the reverse in angiosperms). Of course, your idea makes good sense if the tree rings are indexed, so as to highlight the DIFFERENCES between ring widths in each core.

  74. jae
    Posted May 23, 2006 at 5:10 PM | Permalink

    Upon considering this further–maybe the index should reflect a PERCENTAGE change from year to year.

  75. Willis Eschenbach
    Posted May 23, 2006 at 6:55 PM | Permalink

    Re 72, TCO, an excellent insight, This has been done for at least thirty years. See the 1974 Bristlecone Pine study I referred to earlier, where they analyse both within-tree and between-tree variations for eight upper tree-line sites. In that study they say:

    The other [chronology] represents a smaller subsample of trees for which measurements along two radii were available. Such replicated subsamples are required for analysis of variance and for evaluation of correlation between radii within trees.

    In that study, the within-tree correlation ranged from a low of 0.46 to a high of 0.80, with an average of 0.60 … not real reassuring.

    And the correlation between the trees within each stand is even worse, ranging from 0.23 to 0.51, with an average of 0.37 … in other words, they don’t agree with themselves very well, and they agree with each other even more poorly …



  76. TCO
    Posted May 23, 2006 at 9:13 PM | Permalink

    I wonder if this level of granularity is typically reported or archived. Also, the .60 while it may give one pause can be overcome by sampling more trees overall. You just need to know it and have some idea of how much total RW uncertainty there is and how many trees need to be cored to compensate for it. In fact, it may be more efficient mathematically (and kinder to the trees) to test more trees than to bore each one more times (or section it).

    This is groundhog day, since we’ve already discussed all this.

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