WUWT Opinion Poll – tree derived temperature data

This is for entertainment only. Given the week we’ve had, I thought it might be interesting to gauge some opinion about dendroclimatology. While we can certainly argue the merits of “who said what” etc. the question on my mind is what do people think of the technique of using tree rings for determining past climatic history?

Readers, please invite others at non skeptical blogs to participate, use the “share this” link. I’ll extend a blanket  invitation to anyone to participate, no matter what your view might be.

Since this is a highly polarized issue, I’ll note that the poll code is setup (by WordPress.com) to minimize the possibility of vote stuffing and encourage one vote per person. You’ll know you’ve hit that security feature if certain messages are displayed.

Here’s the poll question:

Of course I should add that no online poll is scientific, it is only an interesting and entertaining exercise in gauging the opinion of people who visit here.

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129 thoughts on “WUWT Opinion Poll – tree derived temperature data

  1. My degree in botany taught me that plants have a variety of responses to environmental conditions. Tree-rings have proven good for archeological dating, but beyond that too many factors confound their clear interpretation as signals of climatic changes.

  2. I do not necessarily dismiss tree rings from consideration, but they appear to be of limited usefulness due to the many environmental factors that affect tree growth.

    The use (abuse?) of tree rings in studies by Mann, Briffa and other members of the profession have not given me or many others great confidence in either the ability of tree rings to measure paleoclimate or in the competence (ethics?) of some researchers.

  3. I can not imagine what kind of a fool it would take to think that tree rings could tell us temperature. Think of the “scientists” who discounted the actual known historical record of the medieval climate optimum and also the little ice age based on what a few trees might reveal via their tree rings. Utterly amazing.

  4. I think this poll is misleading as it almost advocates science by referendum. A careful line not to cross…

    REPLY: Well that certainly was not the intent. I don’t think you’ll find many “science by referendum” studies or publications that have a picture of Snoopy and Woodstock in it. It was intended to gauge opinion of visitors to WUWT and to be entertaining and interesting, nothing more. It is the weekend after all.

    But since you’ve demonstrated that some folks might get the wrong idea, I’ve made it clearer. Thanks. – Anthony

  5. I have 2 identical species of trees planted at my house – one on the southeast corner in full sun that gets lots of water and one in the northwest corner in the shade that gets little water. After 8 years, the one in the sun with water is twice the size of the other. How could one make any interpretation of climate based on such trees?

    True, these trees are affected by artificial (man-made) influences, but use of trees to estimate climate also seems fraught with a huge range of local environmental influences that simply cannot be accounted for.

    My opinion: tree rings are interesting, but should be used with utmost caution and only when a very large sample of trees corroborates other sources of data with very little deviation.

  6. The thickness of tree rings is heavily influenced by rainfall which can be heavy during cold or warm seasons or periods. Thus dendrochronology is a weak proxy for gauging temperature.

  7. I collected some tree ring data as an undergraduate 30 years ago. There’s an inherent bias in that healthy trees are preferred, so all selected trees started life in good times. Bad times are gauged from those trees which successfully lived through them. Microclimates — such as if the tree is on a south-facing concave vale, or north-facing convex slope, or competition from neighboring trees — rule. You can only get climate information from features shared across most samples. So it is the median measure for each year which counts. You need to use all the data to get the median. Theoretically some selectivity could be needed, but only if the on-site collection was top-heavy by microclimate — you’d hope the sample collectors were better than that. Briffa’s concern that samples should be from multiple locations is correct, but one location is valid if it is a big enough “location”. A few trees from one location would be worth more per tree than many trees from one location, so you scale their importance as the square root of the number of samples, up to some maximum. So Briffa’s expressed concerns are good science, but not comprehensive I suspect.

  8. FYI: I believe the correct term is dendrochronology. Never heard of nor could find anything on dendroclimatology.

    Reply: Really? There is this thingy called Google you may want to try. ~ ctm

  9. Plant development is a complex biologic process and small changes to a plants circumstances can have a big impact on rate of growth. Any group of plants growing in the same location, under similar conditions will show a range of growth rates due to genetic makeup and small natural variations – trees included.

    Trying to use trees as proxies to measure small changes in temperature, which is then applied to produce global estimate of change is clearly risible. The Mann and Briffa hockystick graphs prove this to be the case as their temperature reconstructions bear no relationship to historic records.

  10. Tim at 12:52 brought up a good point. A long time ago, my dad planted two oak trees about 7 feet apart. One tree grew 3 times as fast as the other tree. It grew 3 times as fast because it was getting the rain water run off from the house and was in a sunnier spot. Both trees are now cut down, but I remember my dad remarked about the differences in sizes despite the trees being planted at the same time.

  11. Google:

    Results 1 – 10 of about 154,000 for dendroclimatology. (0.47 seconds)

    It may be a new, contrived, compound word. But 154,000 hits indicates it
    is being used.

  12. Its hard to see how tree rings were ever calibrated as a temperature proxy considering the number of confounding variables. The correct choice in the above poll therefore is “#2: the tree derived temperature data has been called into question.” There is nothing unsure about this.

  13. My guess is that the whole problem is that trees are SOMETIMES halfway decent thermometers. But when which ones were, and when?

  14. I hope this isn’t “off topic”. But I’m the orginal “contrarian” I believe when it comes to using O18 to 016 as a proxy for “temperature”.

    I think the geophysics types and hydrologists would tell you that since the common availability of Mass Spec devices since WWII (probably even more so in the 60’s and ’70’s) O16/O18 ratios were used to trace water outflow from costal regions, with the concept that THUNDERSTORMS IN COSTAL REGIONS enriched the O18 isotope.

    One can argue that a higher O18 number represents higher temperatures, as the O18 to O16 goes UP in even inland thunderstorms during the peak temperature summer months versus spring or fall.

    But it should be obvious the NUMBER and INTENSITY of the TS’s will ALSO INFLUENCE THE AMOUNT OF O18 to 016.

    I will submit, therefore, that the O18 to 016 ratio is a proxy for “atmospheric energy”, but that may or may not have any correlation with Troposheric temperatures (seasonal).

  15. JK
    You are not a warmist climatologist are you? You are certainly displaying the initiative and inquisitiveness of one.

  16. I planted 12 boxwoods a couple of years ago in front of my house. Six get more sunlight and water because of a spruce tree and an overflowing eave trough, and they are 50% bigger on average. So I think tree rings are an unreliable proxy for temp

  17. Besides the obvious complexities of other climate and botanical factors, the need for extensive metadata appears to be essential in order to control for the many environmental factors that can influence tree growth. Given that the environmental data changes through time as well as does climate, I am not very optimistic as to the robustness of trees as temperature proxies.

  18. Treerings are not entirely useless from a climatological point of view. Most chronologies do reflect years with extremely bad weather – usually caused by major volcanic eruptions. Years like 1453, 1601, 1783, 1816 are found in most northern hemisphere treering series. Beyond that I am very skeptical.

    It should be noted that treering chronologies were originally developed for archaeological dating, and in that field they have been brilliantly successful, as they have also been for calibrating radiocarbon dates.

  19. There might be some correlation between tree ring widths and temperature, but surely you cannot get from them accurate measurements to one tenth of a degree. The attempt to created temperature “records” 2000 years back, with a resolution of one tenth of a degree is absolutely insane. When I first saw the Hockey Stick, it took me all of 10 seconds to deduce it was bunk. I just looked at the numbers on the vertical (temperature) scale, divided into tenth of degrees.
    Being an engineer, I have some grasp of what numbers convey.

  20. Well, I voted unsure. I agree with Bernie, the metadata is lacking and this seems to me to be a neccessary prerequisite for their use as temperature proxies.

  21. I was under the impression that the only certain thing you could learn from tree rings was the tree’s age when it was cut down. Differences in width of the growth rings couldn’t possibly tell you anything with mathmatical certainty. They would only show that conditions were more or less favorable for growth during the tree’s lifetime.

    Historical records and passages in literature of the day would seem to me the best indicator of the general temperature range during a particular period.

  22. Evidence provided by an actual referendum, while very limited, still beats the blatant assertions of consensus and ‘settled science’.

  23. A sole tree can certainly not tell of global past climate, however, the GLOBAL tree population, past and present, might tell us something useful.

  24. I’d vote yes to,

    With a sufficiently large sample of trees there should be an atmospheric temperature signal.

  25. It is my understanding that tree rings when correlated with temperature records can provide a reasonable proxy for temperature beyond the range of where correlation is possible.

    What Mann does is to correlation a limited subset of the data (bristle comb pine from the US SW) with temperature and then adjust the rest of the tree ring data to fit the correlation. The result of his approach is that in forcing a fit he makes all the data prior to the instrumental record (and especially the data that is not the limited set he correlated) do weird things – like erasing the MWP. What Briffa appears to be doing is similar.

    This approach is apparently only acceptable in the world of dendrochronology (or dendroclimatology for those that like the alternative term). Why it is acceptable there appears to relate to what in science is called “confirmation bias”.

    Climate science isn’t the first field where confirmation bias has been allowed to run amok. That does not however make it acceptable.

    Now that major government policy that can (and likely will) devastate the economies of the western world is being adopted (based in large part on the perceptions generated by the results of Mann’s and Briffa’s work), it has become imperative that the science community insist upon better proof.

    In a perfect world where science is buffered from politics this is what would occur. But alas, we live in a world where science has bee hijacked by politics, so get ready for a wild ride down the economic slide.

    Might be a good idea for younger readers to learn Chinese or Hindi as that is where the world economy appears to be headed.

  26. Original, tree rings were used solely for dating purposes and for that they are very useful. Their use for temperature measurement, proxy, came much later and has always been somewhat dubious.

    As our biology friends have already pointed out tree growth is subject to many environmental parameters and separating them from one another is extremely difficult and cannot be done by the method that ‘the team’ has used.

  27. Probably tree rings are probably better indicators of rain as others have stated, as sunlight on it’s own can bring about a plants demise. A drought can produce narrow tree rings which can happen at high or low temperatures.
    Some years ago there was an incredible TV program called The Green Machine. One thing I remember from that was the sound of photosynthesis which appeared to be driven by sunlight. In which case I would say tree rings are an accurate indicator of sunlight and rain. That is NOT temperature and rain.
    However, maybe there is a tree out there that grows in response to temperature alone. But to derive gloabl temperatures from that tree I would have thought you would then need to find the same kind of tree scattered evenly around the planet.
    Another aspect of tree ring growth is what a trees growth profile would be over it’s lifetime. Do trees have the potential to have even growth rings throughout their lives?

    I thought tree rings were used primarily as a means of dating historical artefacts, and have been a useful cross reference for carbon dating, and magnetic dating.

  28. Vigorous, healthy tree growth in recent years (whether a proxy for temperature or not) is considered evidence of something disasterous coming our way.

    A different “selection” of trees indicates that they’re not doing so well in recent years. This is considered “good news” (by some).

    Are we in favor of tree growth, or opposed?

    Watts up with that???

    Best,
    Frank

  29. I should add that an atmospheric temperature signal will only be found in cold climates.

    I have only to look out my window here in Western Australia to see plants grow like crazy in the winter because it rains. Come summer almost all plant growth will stop because it doesn’t rain.

  30. Jacob (13:36:02) :

    The attempt to created temperature “records” 2000 years back, with a resolution of one tenth of a degree is absolutely insane.

    Yes, it is absolutely insane; however, the purported resolution is not one tenth of a degree, but worst… one hundredth of a degree, i.e. index of growth*0.01 °C. It’s not science. I have used the formula for calculating the change of temperature based on treerings growth, then compared with solar irradiance and the resulted correlation is amazingly high. Then I plotted the raw data, without making the conversion to temperature and compared the results with the solar irradiance databases…

    The correlation didn’t disappear, but reinforced. What does it mean? That the treerings growth depends mostly on insolation; the last assertion coincides with what we know about plants physiology. Siberian Larch Trees, or Russian Pines, slow their growth when the insolation is higher than 50% of the total available, so the conversion of treering growth index to change of temperature will always give false results and flattened lines. There is no doubt about it.

    Bristlecone Pines and Siberian Larch Pines respond also to temperature in the same way. Their growth slows when temperature is above 23 °C. There is no way to know if the narrowing of the treerings growth was due to low or to high temperatures. The claim on associating the treerings growth with the environmental temperature is simply fraudulent.

    More fraudulent is the fact that some dendroclimatologists have chosen C3 plants (pines) for their assessments when they perfectly know the treerings growth will give its maximum value at 23 °C, and lesser or minimum values at temperatures both below and above 23 °C. It would be fair if they would have chosen C4 trees from mid, tropical and equatorial latitudes, which respond proportionally to increases of insolation.

    On the other hand, the growth of any tree depends on the healthy state of its leaves, which is where 95 % of photosynthesis occurs. However, if an army of ants decide to cut leaves of a group of trees in a given region, those trees will offer an extremely low growth even when the insolation index is 1, or if the temperature and humidity are optimal for the tree grows splendidly.

    Conclusion, treerings are absolutely useless as proxies for assessing environmental temperatures.

  31. The only thing tree ring widths tell you is whether conditions were favorable for a particular tree at a particular time. This might mean warm and/or wet weather, but what factors matter/mattered when and where and for which trees is…impossible. Dendroclimatology is, as far as I am concerned, a waste of time given the difficulties inherent which out weigh the dating advantages IMAO.

  32. air temperature has little infuence on tree growt. if there is enough rain and lots off sunshine but colder temps then the tree will have a good year.

  33. I’ve only ever considered tree rings to be useful in determining the trees age.
    Wouldn’t hang my hat on the accuracy of any temperature data that may be implied by them.

    Ian

    Canberra

  34. Whether or not a given tree species grow in a certain area can be a temperature indicator, so the ‘tree line’ or limit seems to be a reasonable indicator of climate. Certainly no palm trees in Antarctica.

  35. I think its clear that ring width is a function of many factors, temp being only one, and for that reason width should be discounted as a temperature proxy. I would suggest that a better means of analysing cores is to look at isotopic ratios, much as is done with speleo core data. Determining carbon isotope ratios of course is easy, of course, and I’m no expert, what possibly could be used here?

  36. Tree rings are a possible source of temperature history.

    Trees rings are a possible source of precipitation history.

    Trees rings can possibly tell us about surrounding vegetation, particularly taller trees.

    The trick is to figure out which of many factors the tree is trying to tell us about.

    In the papers I’ve read, I didn’t see any reasonable methods being applied to try and separate out the various factors.

    It would be interesting to take the various tree ring datasets and use CPS or other methods, but trying to extract a precipitation history. That should be as valid (or invalid) as trying to extract a temperature history.

    ==============================

    All of the above comments also apply to sediment varves, such as used by Mann to determine the annual hurricane count back several hundred years. Of course the multiple factors affecting sediment varve thickness aren’t all the same as for tree rings, but the challenge is the same — to determine which of many different possible driving agents are the ones affecting varve thickness in different levels of the core. Just like with tree rings, we have no assurance that the reason for different thicknesses in one time frame is the same as in another time frame.

    As one wag put it “Torture the data sufficiently and one can get any answer. “

  37. Eh. What poll? Where’s the poll? And what’s the question?

    Like global warming it isn’t showing up here.

    Or am I looking in the wrong place?

    Kindest Regards

    REPLY: Try turn on photos for your browser or use a different browser.- A

  38. What Wade (13:08:38) : said was exactly right.

    Two years ago I planted about ten Dawn Redwood tree seedlings all within 100 feet of each other.. Some of them have done really well and others are puny. Whether it’s the soil, the sun, neighboring trees sapping their nutrients, I don’t know. Location, Location, Location…

  39. From what I can see, studying tree rings requires even MORE random sampling than other proxies for the simple and obvious fact that each tree’s growth will depend mightily on rainfall, light, location (valleys and mountain shadows, other trees, underground water, etc.)

    Trees are notoriously different between themselves, even identically aged trees next to each other in a forest.

    I could see using trees for general, averaged climate as long as you gather and use data from a fairly large number of trees over a fairly large area. Anything else, any other use, any lesser method of gathering “data” will be meaningless. Or maybe, will be wishful thinking.

  40. FYI, here is an email I have just sent to the NPR ombudsperson:

    Dear Sir or Madam:

    As a longtime environmentalist and fan of NPR, who does retain a scientific world view on controversial subjects like the widespread but increasingly religious belief in C02 induced “global warming” I have been appalled by the lack of objectivity apparent in almost all NPR shows that claim to treat this subject in an objective fashion. I’m sure that we can all agree that were the alarmist prognostications of the IPCC valid, then extreme measures would indeed be appropriate. The trouble is, they just aren’t. In fact, it should by now be evident to any reasonably objective person who has bothered to follow the real scientific debate on this topic, that the “consensus science” on which the public statements of Mr. Gore, Dr. Mann, Dr. Briffa, and other global warming advocates are based, is currently in the advanced stages of a complete melt down. This is particularly true now, given the manner in which Dr. Stephen McIntyre has recently revealed the dependence of Dr. Briffa’s new substitute “hockey stick” on tree ring data that is little less than bogus. If you don’t believe me, please visit wwww.wattsupwiththat.com and consider the recent relevant posts and discussion comments.

    NPR staffers can’t even seem to get very basic facts, like the current state of arctic sea ice, correct in their news stories. It is quite untrue to categorically assert, as a gerundive fact, that “with arctic sea ice disappearing” anything else should be postulated. Arctic sea ice is NOT disappearing, notwithstanding the drumbeat of today’s mass media, including NPR. Here, for your information, is AMSR-E’s data on arctic sea ice for the past seven years: http://www.ijis.iarc.uaf.edu/en/home/seaice_extent.htm

    Please note that we are the *third year* of a strong, apparently cyclic rebound, in arctic sea ice extent. The strength of the pattern over three years is particularly evident in this third season. This trend is consistent with the known reality that, for the last 8-10 years, there has not been ANY increase in global temperatures; if anything, there has been a slight decline, and many informed scientists expect this decline to continue for the next twenty years or more, at least.

    The facts are diverging from global warming rhetoric. Its your job to notice that.

    Given the extent of the denial and hysteria that mark the current state of discussion on global climate predictions, it is safe to predict at least one thing: whether the recent 8-10 year flatlining of the IPCC’s projected increases in global warming (and consequent divergence between the alleged cause and its predicted effects) continues, or merely represents a temporary divergence between theory and reality, the theory of CO2 induced global warming (which has always been based on the incorrect assumption that climate modellers actually understand the energy dynamics of earth’s system well enough to distinguish a real cause from a hypothetical one), seems destined one day to be a textbook example of the “extraordinary popular delusions” about which Charles Mackay first wrote in 1841.

  41. First, Anthony, thanks for an interesting question. It is actually two questions, viz:

    1. Does temperature leave a signal in the width of the tree rings?

    2. Can we reconstruct the signal from the width of the tree rings?

    The answer to the first question is definitely yes. A perfect temperature for that kind of tree will lead to wider rings.

    The answer to the second question, however, is generally no.

    Tree rings are not good thermometers. Trees grow poorly when it is too cold. But they also grow poorly when it is too hot. There is no way to tell which is which. A hot year is indistinguishable from a cold year.

    This makes it theoretically impossible to extract the original signal. If a tree ring with a width of 2.7 mm could either represent 60°F or 80°F, we simply cannot reconstruct the original signal from the tree ring widths.

    But wait, there’s more, as the pitchman says on TV … it gets worse!

    Narrow rings can also occur because it is too dry, too windy, too much frost, late spring, waterlogged soil, and a host of other things.

    Goldilocks in the story had three temperatures — too hot, too cold, and just right.

    With trees, wide rings definitely mean “just right”. The timing of the frosts and the water when needed and the sunlight and the temperature and the nutrients and the clouds and the wind all conspired to make a good year for that tree. Things were just right. Not one thing was lacking.

    But unlike Goldilocks, tree rings cannot tell too hot from too cold. Both of them make narrow rings. So does a lack of water. So does the wind blowing from the wrong quarter, and a host of other environmental factors.

    The standard way to attempt to get around this problem is by simply interpreting narrow rings as representing cooler years. Inevitably, this pushes the calculated “temperature” downwards. It falsely represents the past peak temperatures as being lower than they actually were. Any event that slows tree growth, including too hot a temperature, is calculated as though it were a cooler temperature. You can see what that might do to e.g. the Medieval Warm Period.

    So there are two huge problems with extracting the temperature signal from the tree rings:

    1. A narrow ring can mean either too hot or too cold.

    2. No one single factor (e.g. moisture, temperature, hours of sunshine) can cause a wide ring. All of them have to be right to get a wide ring. But a variation in any single factor can cause a narrow ring.

    Problem #1 means that even in the best of cases, with all other factors being equal, our resulting reconstruction will be inaccurate and also biased downwards.

    Problem #2 means in the real world, our resulting reconstruction will more inaccurate and will be biased even further downwards.

    So my vote on the poll is no, at present the temperature signal can not be reconstructed through tree ring width.

    My best to all,

    w.

  42. Thanks Anthony.
    I am always annoyed when I read in some media “that a majority of people believe in AGW” and feel that one single climatologist always trumps 100,000 uninformed people…

  43. I still trust the Hudson’s Bay Temperature records much more than I would trust dendro. Very close to 400 years of sub-artic temperature records that amount to millions of data points. Compared to that, the dendro stuff is very weak. No wonder there was such a concerted effort to marginalize the guy who was documenting that record. The Hudson’s Bay Company was probably in cahoots with big oil anyway, ……. 8^]

  44. Some nice words here about dendrochronology being a better tool than dendroclimatology. I think that is true but there are limits. The same variations in growth of individual trees discussed here has the potential to make some wood samples simply unmatchable to a master chronology. Local climates and microclimates have similar effects.

    There is however a natural human temptation to produce a match rather than no-match and a less than rigorous match is sometimes quoted as ‘the best available match’. But what is not always recognised or even mentioned when such dates are quoted is the very real possibility that the date produced might be wrong. Keenan has written about this.

    Sometimes dendro dates are ‘supported’ by similar radiocarbon dates. However the master dendro sequences have been put together with the assistance of radiocarbon dating and radiocarbon dating is calibrated by information from the dendro sequences. I am not a scientist nor a historian but to me this means that the dates produced have a degree, perhaps a large degree, of uncertainty.

    Years AD are not generally a problem because there is usually plenty of other evidence about dates so dendro dates are often simply used to refine an already reasonably well known date. But in years BC, particularly in pre-Classical times, there may be no available belt to go with the braces. There are therefore a lot of issues about chronology at this time and every reason for scepticism about the certainty of the scientific dates that are available.

    All this is further confounded by the refusal of some dendrochronologists to publish or otherwise make available their data…

  45. OT : I used to live in State College, PA (yes, home of M. Mann). On Mount Nittany there are two Hemlock trees, side by side, that are thousands, yes thousands, of years old growing in the middle of a small stream. They are extremely big and healthy and a sight to behold. If you ever get to that area, do visit them. It does require a bit of a hike, but knowing that you are touching something that is still alive and is that old is a very humbling experience, much like visiting a Stonehenge.

    No, I do not believe our present science can determine past temperature using treerings.

  46. Sorry. OT and not entertaining.
    Britons creating ‘more emissions’ http://news.bbc.co.uk/1/hi/sci/tech/8283909.stm
    Greenhouse gas emissions created by Britons are probably twice as bad as figures suggest, says the government’s new chief energy scientist Professor David MacKay.
    “Other countries make stuff for us so we have naughty, naughty China and India out of control with rising emissions but it’s because they are making our stuff for us now,” he said…
    …”This not only means that the true scale of required emissions reductions in the Western world will be much higher but that the impact on economic growth and living standards there will also be more severe than so far believed.”

    I wonder what support this viewpoint will have amongst those people that have seen their jobs go to China?

  47. The question “Are trees an accurate enough recorder of air temperature to accurately determine past temperatures?”, is reasonable, but a better question I think would have been “Are trees an accurate enough recorder of air temperature to justify re-writing climatic history and discarding or ignoring hundreds of peer-reviewed papers that confirm the MWP and the LIA?”

  48. I return to the quantitative point. Even if tree growth is influenced by temps, it is not linearly influenced by every degree of fluctuation. A difference between, say, 19, 20 or 21 degrees doesn’t make much of a difference in growth. Only extreme temperatures can be reflected in smaller ring widths. Say – temps below 15 or above 23. (All numbers are hypothetical).
    So there is no way tree rings could be translated into temp differences at a resolution of 1/10 of degree, or even one whole degree.
    Tree rings might tell which years were warmer (or had better growing conditions), qualitatively, but no by how much it was warmer quantitatively.

  49. I think the tree rings are good indicators of how well that particular tree was growing in the given year. But why it was or was not growing is not so clear cut and sounds like so much guessing to me.

  50. Like most polls people can take, there is rarely a response choice that reflects my opinion. Here’s mine:

    Yes and no. Tree-ring data acts as a proxy. A proxy is a stand in, not the real thing. Sometimes the proxy might represent me (e.g. if I’m Temperature), other times it might represent someone else (e.g. my colleague Rainfall).

  51. I voted in the unsure column–I do think that tree rings have some value, but only when there are a lot of trees involved and other factors can be controlled for, or they are used to support other data.

    Having said that, my mother has 2 maple trees in her yard; they were about the same size when they were planted at the same time about 10 years ago. The appearance of the soil and presence of some bits of pottery and other artifacts have led us to speculate that one was planted on the site of an old outhouse. Guess which one is twice the diameter of the other now.

  52. After reading the thread, particularly the post by Willis Eschenbach, I voted no. Before reading, I was unsure.

  53. jacob; totally agree. There may be some temp relationship but the supposed small signal and the collosal error involved make it incredibly suspect to us engineers… I believe one of Steve McIntyre’s biggest criticisms of the reconstructions is the incorrect (or misleading) presentation of error. I’d love to see his analysis of the error limits (has he presented that before in graphical form?).

  54. I think your post makes a lot of sense, Mr. Eschenbach. I would question this though:

    “A perfect temperature for that kind of tree will lead to wider rings.”

    It seems to me that perfect temperatures for a tree, if sustained, would lead to more trees growing near that tree, which means more competition for sunlight and other resources. So perfect temperatures might cause wider rings at first, but I would expect them to eventually get thinner again.

  55. Whilst it is certainly possible that temperature will be demonstrated in the width of tree rings (given a large enough sample), there are other very important factors that affect them.

    One, mentioned often here from experience, is sunlight. So if there are fewer clouds, there may be wider rings, regardless of temperature. Having said that, clouds affect the temperature too (more than CO2), so there could be a correlation, I have no idea if high and low clouds, which apparently have different effects on temperature, would affect a tree ring, however. Do we know? I suspect not.

    Water is another mentioned here by many. Given plenty of water, a tree may grow very well in a hot year, whereas another would grow poorly given too little water. I have no idea what other combinations would cause. That is a subject in itself, I guess.

    Finally, we have the start of the show, CO2. Now, CO2 is literally food for plants. Whereas we get our carbon (carbohydrates and protein, aka ‘food’) from plant and other animals (according to taste and availability), plants get all of their carbon from the air in the form of CO2. This is, therefore, what they ‘eat’. If they have an abundance of CO2, they do very well. In fact, doubling CO2 will cause an increase in growth of 40% given no other resource is lacking. If any other resource is lacking (for example in hot, arid countries), that increase could be as much as 100%. Quite a boost, you’d have to admit.

    As an aside, if I wanted to ascertain that (not whether or not, mind you) CO2 levels were correlated with temperature, and I could also claim that tree ring widths were an accurate record of temperature, I’d be on to a winner. If CO2 levels are high, trees will grow more, therefore rings will be wider. So I’ve proved that there is a correlation between CO2 and temperature! It really is CO2 causing Al Gore Warming, as long as no-one points out my circular reasoning, of course….

  56. I would say no, simply. (better answers above)

    Certainly the claims of robustness coming from the Hockey Team in defence of their graphs don’t make any sense whatsoever. Allowing one tree such influence over the final result seems an incredibly bad application of statistics to me. And I’m no statistician! Or scientist!

    Peer review, my foot.

  57. Willis Eschenbach takes the prize. Thanks for the clarity. It’s a false mapping from temperature to tree rings because many “input variables” (temp, water, sunlight, wind, insect stress, browsing animals, soil conditions) all map to the same “output” of ring-width. That “multiplexing” means you can’t extract the temp signal from the aggregate (confounding) factors unless you do huge sample sets and rigorous methods and independently corroborate, as a physical process, ring width goes with temp. But here the statistical rigor is absent and in any case it seems, per Willis Eschenbach’s comment, that ring width is inherently ambiguous for temperature: low temp and high temp both map the same way.

    Bottom line, dendroclimatology = junk science. Whoever gave Mann and Briffa their degrees, never mind their funding, should be run out of town.

  58. Understand, the temperature signal *IS* in the tree-ring data, but in order to extract it you would need solid proxy’s for precipitation, solar radiation, etc… all down the line for all the other factors in order to extract what you want.

    Real scientific investigation would be finding a method of doing just that, not taking the ring data at face-value.

  59. John Cooper (15:24:20) :

    What Wade (13:08:38) : said was exactly right.

    Two years ago I planted about ten Dawn Redwood tree seedlings all within 100 feet of each other.. Some of them have done really well and others are puny. Whether it’s the soil, the sun, neighboring trees sapping their nutrients, I don’t know. Location, Location, Location…

    To follow onto your post, a co-worker and I each purchased a forest pansy redbud three years ago from the same nursery on the same day. His was slightly better than mine visually. He lives only several miles away in the same general climate. He visited the house this summer and ask where ours was. I said you’re standing beside it. He said, “no, I mean the one from three years ago. This one is much older”. Seems I planted mine in a location where a blue spruce had been excavated, and the nutrients have cause it to now be twice the size of my co-workers tree. All in three years.

    I have to admit, I have never seen a forest pansy redbud (slow growing tree) grow this fast. The greatest growth was this summer, when our temps averaged -1.5C. The point is that nutrients play a huge role in tree growth spurts, and the negative temp aspect had nothing to do with it. In fact, when you think about it, nutrients, water, and photosynthesis (it’s always about the sun) are the three most important players in a tree’s life. Not temp. It almost seems like a no-brainer.

  60. It seems almost gratuitous to mention that water stress, for example; either too much or too little, provokes, in a plant, the production of abscisic acid. This is a growth regulator (hormone, if you like) that suppresses growth. This retardation persists long after the environmental stress is mitigated. A plant can sit and sulk for the entire season after a brief but intense period of drought or water-logging.
    Also, how come there’s no allusion to spring and summer wood? Surely, they could tell me not just how warm it was in the year but in the two growing seasons; pines and larches usually have very distinctively colored rings.
    Anybody lacking an incremental borer ( the tool of choice for sampling without killing) and disinclined to the wanton felling of someone else’s trees can do their own subjective assessment of the variability of individual tree responses to the slings and arrows of forest life by strolling through a juvenile plantation of conifers and noting the length of this season’s leaders and comparing the internodes between branch whorls of previous years.
    I’m pretty sure I voted ‘No’ but Anthony appears to have sneakily switched the order of the questions.

  61. I think tree rings are valuable. There is information in there. We just can’t get ahead of ourselves. At some point we may be able to analyse the woody material that make up each ring to the point where we can gain additional insight and de-confound the data of interest. We are not to the point yet where it is anything other than a rough tool.

  62. I do not see how tree ring records can be used to deduce anything over a time period longer than a fair fraction of the life-span of the tree species involved.

    There must inevitably be a high pass filter effect.

  63. This science is probably just as valid as the one where they measure the bumps on your head. I forget what they called it, and NO, I am not going to look it up on google. I hate google.

    [Phrenology. The maps look much the same, come to think of it. ~ Evan]

  64. I vote that someone here or anywhere write a paper that can be published showing how tree rings are not/cannot be indicators of temperature.

    Please! Somebody do more than write a post. Publish a Paper about this matter if you are so convinced that trees cannot be used for establishing past temperatures. Otherwise, this is all conjecture. (And please spare all of us the conspiracy theories about peer-reviewed science).

  65. For more than a decade, like othe commenters here, I have been planting tree seedlings. My trees along a railway plant corridor show diverse growth, some flourish, some do not. Like the climate system, tree development is not simple.

  66. I have to say I am not sure.

    The Yamal series, for example, seems reasonably on the mark–except for that one single tree!

    Do I trust MBH? Heck, no.

    I wouldn’t want to write of the entire methodology as completely worthless. Which it may be. Or not.

    After all . . . I don’t much trust the GHCN final Surface Temperature results, but that does not mean that I don’t believe thermometers can be used to measure temperature . . .

  67. End of story. Tree rings tell you something (unreliably) about the conditions the tree has experienced. Nothing else. And certainly nothing about Hemispherical temperatures. Enough already, move on.

  68. I work with bonsai trees, which are interesting because the balance must be very precise for the tree to grow well. Not mentioned very much so far is disease. I don’t have any formal training, but it is evident from the bonsai that fungal growth is directly related to climate. Warm, wet weather seems to encourage fungal growth in our trees, while dry, cold weather retards fungal growth. The fungus is also somewhat cyclical… the tree is more infected in early spring if the weather is wet and warm, so growth is slow. If the weather dries out, or there is a cold snap, the tree rebounds and growth becomes stronger. If the wet conditions persist, the needles or leaves will be smaller, less effective, and cell collapse will continue. Such a weakened tree will be even weaker in the fall. Some trees are more resistant than others. A tree weakened by several seasons of warm, wet weather, insect infestation, etc would show quite retarded growth, it seems to me. These are just observations, though, and could be quite different for polar trees.

  69. Alas, the actual poll question, as opposed to the accompanying article, does not reference tree rings. Tree rings I think I could scoff at.

    But “tree derived temperature data” generically as stated in the actual poll question? No. The reason is I *do* place value in the various studies that have been done showing where trees grew in the past vs now. That kind of tree temperature data, so far as I know, has not been seriously called into question.

    Of course, the studies I’ve seen reported also don’t support the idea that the 20th century is “warmest in the last umpty centuries” either.

  70. I am no statistician, but I am curious as to how Beck’s work would stand up to an audit, …… Would at least show the warmongers a bit of good faith, since the importance of tree proxies has been thoroughly autopsied. Steve, please publish. If peer-review is not done fair and square on your paper, first they will hear the sound of pipes in the highlands, and then, …..

  71. On a similar note, Tom Wigley who? The poor Lamb made way for the wolf, …. that ate the homework. Sorry for the cryptic post,……~~~~~~~~~~~~~~~~~~~ just messin’ ’round, ….. :^]

  72. This from Dr.Keith Biffa’s site at http://www.cru.uea.ac.uk/cru/annrep94/trees
    It is fairly general and includes this…..

    “By sampling selected trees in carefully chosen locations it is possible to simplify the identification of specific climate information. For example, trees growing at high latitudes or high altitudes are most sensitive to changing temperatures while the growth of trees in semi arid environments responds strongly to changing soil water conditions and so provides information on precipitation. ”

    This is interesting and some links to establish the validity that trees at high altitude/latitude are more sensitive to temperature than the other factors would be welcome.

  73. Dendrochronology is great for dates…. Dendroclimatology’s attempt at a temperature record though, is flawed…..

    Too many things affect the growth of trees.

    …. Then of course there is the government funding of science to justify environmental ideological policies…… The integrity and reputation of Science is at risk of being impugned in the minds of many, if this sad state of affairs continues.

  74. Signal to noise ratio. There is no discernable signal of temperature changes in tree rings from year to year, or score to score or century to century, and “discernable” is the correct word. No point in arguing about resolution. The value of signal in the ratio is so tiny that the value of the ratio approaches zero.

    [snip]

  75. Jody (19:40:57) :

    I vote that someone here or anywhere write a paper that can be published showing how tree rings are not/cannot be indicators of temperature.

    Please! Somebody do more than write a post. Publish a Paper about this matter if you are so convinced that trees cannot be used for establishing past temperatures. Otherwise, this is all conjecture. (And please spare all of us the conspiracy theories about peer-reviewed science).

    I wrote a paper on this issue. It’s not the definite paper because I have to include some other graphs on raw data compared with solar irradiance, but it gives you the whole panorama about the uselessness of treerings for establishing past temperatures. Please, pay special attention to the last diagram:

    http://www.biocab.org/Insolation_Treerings_Growth.html

  76. Oops! Please change “definite” for “definitive”. The phrase corrected is as follows:

    It’s not the definitive paper because I have to include…

    Sorry… :)

  77. Keith:
    “This is interesting and some links to establish the validity that trees at high altitude/latitude are more sensitive to temperature than the other factors would be welcome.”

    Someone posted about this on another thread. Trees in a harch cold environment have a very short growing season. Therefore a change in temperature changes the percentage of the growing season by more than trees that have a very long growing season. A larger percentage change in the growing season is more easily recognized in the rings. But unfortunately the whole thing is a waste of time due to the chronology selection methods that I have described here.

    http://reallyrealclimate.blogspot.com/2009/10/tree-ring-chronology-selection-problem.html

  78. Keith Minto (21:30:35):

    This is interesting and some links to establish the validity that trees at high altitude/latitude are more sensitive to temperature than the other factors would be welcome.

    You cannot disconnect photosynthesis from growth, nor from luminosity. We are talking about trees, i.e. photosynthetic organisms.

    If insolation goes up beyond the optimal index (0.5 for most cases), the growth would slow. That is the reason by which C3 plants prosper better at high latitudes/altitudes where the insolation index is around 0.5 (Odum. Ecology. 2006. Pp. 47-51).

    The big problem is that if the insolation goes up, i.e. above the optimal index, the growth of C3 plants would go down, as if the insolation was low. The same physiological phenomenon occurs with temperature, although the predominant factor is not temperature, but insolation.

  79. I would say I’m not sure. Limited usefulness, probably.

    Of course, they are not useful at all if you throw out the tree rings that don’t agree with your preconceived conclusions. Well, I guess they are useful, but not scientifically. :-P

  80. ANY gardener would tell a scientist that a tree is a rotten proxy for temperature.

    As someone who has held science in reverence for many years I’m still struggling very much with the revelations as to what passes for ‘science’ nowadays. I’m seriously disappointed. When I was a child I discovered that teachers aren’t necessarily intelligent (a shock at the time!). Then I discovered that doctors aren’t necessarily clever either (believing in treatments that are unscientific). Then in my early 20s I discovered that politicians are often liars, and worse, say and do incredibly stupid things. I read many years ago that scientists can be strange characters, and like the great man Isaac Newton himself, display odd behavioral characteristics. But to find out the truth about the scientific process which I have held in very high esteem, and to discover that ‘scientists’ simply do not follow a ‘scientific’ line in many instances has come as a bitter blow from which I will not recover. I no longer trust scientists at all. And neither will I pay any attention to ANY scare story of the future. I’m over halfway through my life, and I’ve heard of everything from a coming ice age to Swine Flu. It’s all nonsense, and I’m bitterly disappointed. I’m a gardener, and I could have told any scientist anywhere that trees grow according to where you plant them. A distance of just 2 metres can have an effect. As a proxy for temperature they’re useless. I’ve grown many trees (too many to count), and I can say that sunlight and water mean everything to a tree.

  81. Is it just me? I am not generally dyslexic, but every time I see the word treering I mis-read it as teetering.

  82. Jody (19:40:57) :

    I vote that someone here or anywhere write a paper that can be published showing how tree rings are not/cannot be indicators of temperature.

    Please! Somebody do more than write a post. Publish a Paper about this matter if you are so convinced that trees cannot be used for establishing past temperatures.

    Jody, the problem with your request at this particular moment is we have good reason to doubt the AGW “peer review” system. For the recent past with respect to any climate related science – the whole system is suspect. Not due to conspiracy but due to hard evidence via Briffa demonstrating lack of oversight, bias, poor attention to detail, faulty research protocols, lack of transparency of data, etc.

    Briffa, Mann and likely hundreds of other “peer reviewed” studies attesting to global warming – are now suspect. PR agencies are not substitutes for good science. Your boy has cried wolf one too many times.

  83. I am an AGW skeptic and have been since first starting to hear about AGW in the early 1980s, but I am actually quite open to tree-mometers as evidence of past temperatures. While the growth rings of an individual tree are evidence just of its own unique growing conditions, the only thing a large number of widely scattered trees could share is a global temperature record. So the problem is not the concept of tree-mometers per se, but the vanishingly small sample sizes used. (I have various other problems with the way it is done too, but they’re not worth even mentioning until there are cores from waaaaaaaaaaay more trees from many more widely scattered locations.)

  84. “Are trees an accurate enough recorder of air temperature to accurately determine past temperatures?”

    A bit of a stiff test!

    Actually, taken literally, they possibly are, a bit like boreholes are, the problem is not in the recording, the problem is in the playing back.

    Alex

  85. In Memoriam
    HOCKEY STICK
    Age 11

    So. Farewell then
    Hockey Stick

    Robust Reconstruction

    It would seem that
    You are dead

    But are you?

    You have risen
    many times before

    So why not now?

    But then. Do dendro
    Theories really die?

    And so eternal.
    Remain the doubts

    with Us.

    (E.J Thribb age 17 ½)

    (with apologies to Barry Fantoni and Howard Hughes. In addition, I would also like to add that.. continued page 99)

  86. Keith Minto (21:30:35), thanks for your post. You say:

    This from Dr.Keith Biffa’s site at http://www.cru.uea.ac.uk/cru/annrep94/trees
    It is fairly general and includes this…..

    “By sampling selected trees in carefully chosen locations it is possible to simplify the identification of specific climate information. For example, trees growing at high latitudes or high altitudes are most sensitive to changing temperatures while the growth of trees in semi arid environments responds strongly to changing soil water conditions and so provides information on precipitation. ”

    This is interesting and some links to establish the validity that trees at high altitude/latitude are more sensitive to temperature than the other factors would be welcome.

    I’ve heard that claim as well, but I haven’t found the studies to back it up. The problem is that temperature is not a limiting factor by itself. It is always the temperature in relation to how much water the plant has. With enough water, trees can continue to grow at a much higher temperature than when they are water stressed. If trees are short of water, they show the signs of heat stress (e.g. lack of turgor, browning) at a much lower temperature.

    The problem with Briffa’s claim is that high elevation sites are often quite arid. They also are often on steep, poor soils with little moisture-holding capacity. As a result, although you would expect trees near the treeline to be “most sensitive to temperature” as Briffa claims, the real issue at the treeline is often not temperature. Extra warmth means nothing if there is not enough water to allow increased growth. In fact, when water is short, extra temperature leads to less growth, not more. And at the treeline, water is often very short.

    So although I read that statement a lot, I don’t think it is true in general. It may be true in the wetter parts of the Pacific Northwest, but I believe it is not generally the case. I’d have to see some good studies of the question before I’d believe it, and despite looking, I’ve never found them. However, they may be out there … so let me add my voice to yours in asking for some links to establish the validity of the claim.

    Best regards,

    w.

  87. jeroen (14:34:21) :

    if there is enough rain and lots off sunshine but colder temps then the tree will have a good year.

    I’d like to add, if you don’t mind : if there is enough rain and lots of sunshine, plus extra co2 in the air from burning ‘fossil fuels’, but colder temps then the tree will have a good year.

  88. We have enough trouble with being able to achieve accurate long term trend results using modern calibrated thermometers and thermisters. This is evidenced by the data manipulation used to try and nullify environmental and other factors on the raw recorded data.

    To quote Cheech and Chong on the different use of a certain tree….
    “Far out Mann !!!”

  89. plus extra co2 in the air from burning ‘fossil fuels’

    Exactly, what does a 100ppm increase in CO2 do to tree growth?

    I am surprised we do not have far more hocky sticks.

    Air temperature need not change at all. Normaly the hockey team likes to make ajustments. If the recent years in all these treemonitors were adjusted down for the increase in CO2 what would they show?

  90. I wonder if trees also suffer from lack of carbon dioxide when they are growing in dense growth at the bottom of a poorly mixed air column. Sort of the situation you’d find over an Iowa cornfield on a calm day.

  91. I posted this over at lucia’s, but it applies here very well.

    Jeff Id over at tAV said it very well in his post -RC Off the Deep End-

    “So the possible sorting of data suggested in the quotes given — is actually standard practice.”

    Gavin’s rants over at RC about accusations of cherry-picking are oxymoronic in the extreme. The whole approach of cherry-picking proxies because only some have a positive correlation with measured temperatures invalidates the whole mess.

    Its PaleoRorschachism, a new CAGW-created psychosis. Perhaps it can be added to the excellent list of things caused by global warming over at numberwatch.

    http://www.numberwatch.co.uk/warmlist.htm

  92. I agree with the CO2 comment. Clearly, more CO2 will cause the trees to grow faster. This would somehow need to be accounted for. But how? Is it a linear response? Or, something else?

  93. I voted “Unsure”…

    Like all proxy data, tree ring analysis has limitations. Despite its flaws and recent possible misuse of tree ring data, I think it is still a valuable paleoclimatology too.

  94. I voted “no” but the study is worth pursuing. If you don’t ask, you don’t larn nuthin.

  95. Methinks the time for debate is over. Looks like a consensus to me. ;-)

    Now can we ditch all the extra ‘carbon taxes’?

  96. I don’t know if this took so delete id it’s a repeat
    With the debate about tree ring data and “global warming, I though I’d compare tree ring data to long term temperature data. The tree ring data I found from http://www.climatedata.info
    With tree ring Nor. Hem. proxy data shown below, using the 20 year MOV Norway, Sweden & Russian data, since they were more compatable to Ave14 defined below:

    http://www.climatedata.info/Proxy/Proxy/Proxy/treerings_northern.html

    Next I took the 14 longest temperature records from http://www.rimfrost.no/
    plus the east English data starting in 1659. I averaged the whole bunch up to form a composite average Ave14. This is shown below:

    I then added 40 year filtering consisting of a MOV, Fourier filter, and a 2 pole reverse Chebushev filter. The later is found in MATLAB as “filtfilt”. Basically the later filter is run forward and then backward to compensate for phase delay. Unfortunately the end points generally will have a significant error, but is a good cross check for date in the middle of the sample. The Fourier gives much better end point results, comparable to the EMD method.

    The figure below compares the 20 year MOV averaged tree ring data with the 20 year MOV Ave14 data. The tree ring width is plotted against temperature.

    For what it’s worth, it’s in the region where it “kinda looks” correlated, but would need more sophisticated analysis to show anything definite. From this short analysis, if I were a betting man, I would note bet the farm on tree ring data, much less the chicken coop.

  97. The other thing to consider is it might be possible to use treering data and have it actually mean something about C02 if the sample size is sufficiently large to average out those near-environment issues that impact individual trees like shade from elders being removed over time, and nutrients. But then we’re probably talking about sample sizes in the thousands (tens of thousands?), not 12, 10, 1. . .

  98. Each tree grows within its own microclimate. While many of these microclimates may be similar, few, if any, are identical. A given species has evolved to tolerate a wide range of variation in its microclimate, which broadly defines the range of the species.

    BUT, the number of unidentified variables controlling any one tree approaches infinity. Therefore it is nearly impossible to define a statistic that accounts for these variables well enough. Tree ring chronology is independent of climate (with the exception of seasonality in some species), hence its usefulness for dating. No such independence exists for correlation with temp, and perhaps even moisture.

    Treelines and range limits are better, but even they have issues. Treelines are plagued with the variability introduced by edge succession, and the accumulation of humus, which is a huge modifier of the microclimate, and hence, the stability of the treeline.

    Complex plants and animals are lousy proxies for just about everything, due to their acquired adaptibility.

  99. Mike O (08:12:57) :

    I agree with the CO2 comment. Clearly, more CO2 will cause the trees to grow faster. This would somehow need to be accounted for. But how? Is it a linear response? Or, something else?

    Honoring truth, there are some forests that don’t do it well at high concentrations of CO2. I am referring to concentrations of CO2 above 1000 ppmV. In general terms, tropical, subtropical and equatorial forests do it well at high concentrations of CO2. Our plants, I mean plants for food, do it superb at very high concentrations of CO2.

  100. You may violently disagree with the covenants of common law (precedent), but it little profits that you rant about its injustice. File a brief with your own pro argument carefully researched rather than the criticism that “the law is a ass.” The frequently-heard reductio-ad-absurdum “treemometers” is such a sweeping condemnation.

    One commenter above wonders what kind of a fool would have his perception clouded by such findings that would call into question “the actual known historical record of the medieval climate optimum and also the little ice age based on what a few trees might reveal via their tree rings.”

    It seems to me that much of our understanding of paleoclimate history is based on tree rings and other (similarly-fallible) sciences which depend upon years, centuries, eons of layer-deposition, and that we might do with a bit of careful review of the science here before we proudly don the mantle of Mr. Bumble.

    I vote “yes” with the caveat / hope that the science continue to be funded and studied by a less-restricted, more open body of scientists, and that its findings be much more clearly understood and accessible before they are used as a criterion for enacting sweeping political and economic changes.

  101. Antonio San (12:52:01) :

    “I think this poll is misleading as it almost advocates science by referendum. A careful line not to cross…”

    Would you apply the same kind of thinking to “there is a scientific consensus about AGW?” Is this not akin to “science by referendum?”

    Consensus is not scientific fact, whether on WUWT or at the IPCC.

    Jimbo

  102. I’ve perused this discussion and have seen a lot of good observations made. However, I see no mention of this. Forgive me if I m duplicating someone else’s observation.

    One of my (many) reservations of using ‘treemometers’ is that they don’t work about half the time, i.e., trees don’t grow when sunlight (the daytime) falls below a given minimum, which of course is from mid-fall to mid-spring, depending on the species. The APPLICATION of the treemometer data wrt to global warming is to derive an average YEARLY global temperature. Any temperature signal derived at all from tree rings must necessarily give only an indication of the temperature during the growing season. I’m sure you can see the problem: a warm winter can negate a cold summer, cold winters negate a warm summer, and so on. In light of the miniscule temp changes under debate, why would anyone want to try to reconstruct past temperature data from only the growing season? Why would any reasonable person accept such data as proof of small changea in yearly temps?

  103. Tree ring data perhaps could serve as a proxy for rainfall, temperature, air quality, carbon dioxide, soil fertility, sunlight, etc. But for any meaningful information to be derived from tree rings, a very large sample — hundreds, if not thousands — would be required.

    If the studies that created the “hockey stick” temperature rise hoax were based on a very small sample, were they in effect a “bearing of false witness” against truth and even me, a nonbeliever of AGW? Were they a deliberate, unconscionable assault on God’s eighth Commandment?

    Did this false witnessing create the basis for the current AGW hysteria that our foolish politicians in Congress may soon address by creating a carbon tax that will kill more jobs and further debilitate our desperately struggling economy? Will this false witnessing result in a totally unnecessary poisonous dose of taxation like the deadly adulterated Kool Aid elixir Jim Jones prescribed for his misguided flock of believers at Jonestown, Guyana, a number of years ago?

    Let’s hope the evolving revelations about that junk “science” may provide a desperately-needed antidote.

  104. Tree ring data is very useful since it gives a date to optimal and sub-optimal growing conditions for that particular tree.

    However one is unable to tell if the conditions were global (meaning macro rather than totally world wide) or local (around that one tree) without using a large sample of trees.

    It is a very interesting and valid area of study but one should be hesitant about announcing a world wide trend based on one tree.

    It is the usual “small sample” problem to be found in any area of science. (Coupled with more than one factor being responsible for the results).

  105. Jimbo (13:17:33) :

    Antonio San (12:52:01) :

    “I think this poll is misleading as it almost advocates science by referendum. A careful line not to cross…”

    Would you apply the same kind of thinking to “there is a scientific consensus about AGW?” Is this not akin to “science by referendum?”

    Consensus is not scientific fact, whether on WUWT or at the IPCC.

    Jimbo

    There is a valid (scientific) consensus.

    “Treat the conclusions with caution and examine the original data.”

  106. Nic (15:38:35) :

    Tree ring data is very useful since it gives a date to optimal and sub-optimal growing conditions for that particular tree.

    Given that we cannot be sure about the factor that have influenced on the optimal growth of that tree, we cannot use treering data for deducing a particular factor, except a best photosynthetic performance. ;)

  107. If tree ring growth can be affected by other factors such as rainfall, nutrients, sunlight and maybe CO2 then you have to correct for all of those things before you can get meaningful temperature indications. Do the researchers make those corrections? If so, how do they know the history of those factors? And why do the ten trees not all tell the same story. One shows an upward surge at the end. Another shows a downward trend since 1925. Others show an upward trend, which mostly occured before 1925. Which trees are telling the truth and which trees are lying?

    But even if the tree ring data can give a good indication of the local climate history, how much can it tell us about the climate of the world? Do the ten trees in Siberia know what the climate was like in Michigan, or Mexico, or Africa, or Brazil, or Australia? I wouldn’t want to bet my lunch money on it.

  108. Once we look around, we start to notice that the evidence argues strongly against the idea that growth can be directly coorelated to temperature. I’ve started paying attention (prompted in party by discussions on this site and CA) and it seems everywhere I look there is contrary evidence:

    – similar plants as my neighbor in our gardens this past year; huge difference in growth, despite identical temperatures

    – identical plants in different parts of my yard, huge difference in growth, depending on soil and whether the sprinklers were working in a particular area or not — temperatures absolutely identical

    – different growth for different trees of the same kind at the local park, despite identical temperatures

    Without controlled experiments, it seems impossible to control for all the variables at a historical site in the past. I’ve certainly seen no evidence that it is possible to tease out temperature as an isolated variable.

    Which brings me to the question I’ve asked before. Surely this issue has been on the table long enough that someone has undertaken by now a controlled study of growth vs. temperature and other factors? There ought to be plenty of good data by now on how trees respond to various factors.

  109. Eric Anderson (21:47:14) :

    - similar plants as my neighbor in our gardens this past year; huge difference in growth, despite identical temperatures

    – identical plants in different parts of my yard, huge difference in growth, depending on soil and whether the sprinklers were working in a particular area or not — temperatures absolutely identical

    – different growth for different trees of the same kind at the local park, despite identical temperatures

    Hi Eric… There are many external factors which influence on plants growth, insolation the main factor among them; nevertheless, the most important factors are the inherent factors, specifically, genetic information. As in animals, plants also inherit deficiencies, aptitudes, advantages over other individuals, etc.

    A single error in the production of a protein would lead to disease and deficient growth. Some genetic errors can be corrected through alternate pathways, but many other cannot be corrected; consequently, not all the trees grow homogeneously even under the same optimal conditions.

    For example, by a single genetic failure regarding the production of a volatile substance which acts like a repellent against insects, some bristlecone pines tolerate the friction from insects, while others pines, living in the same ecological area, do not tolerate the friction from insects, which will slow down or stop their growth. You could see a bulky tree which could be a very weak tree that will succumb before a plague.

    Definitely, treerings are not adequate proxies for investigating paleotemperatures.

  110. I am personally keeping an account of all the ”science” and noting how it affects my very expensive lifestyle, when the billion$ lawsuits start to fly I want my corner.

  111. BTW IS it possible to over lay the tree plots with the global temperature plot to see how they line up?

  112. David Segesta (12:01:41) :

    BTW IS it possible to over lay the tree plots with the global temperature plot to see how they line up?

    Yes, it is possible. There are minor problems, like the longitude of the periods covered by other proxies for example, but this problem can be solved by taking individual databases and collating them with the tree plots.

  113. Regular readers of sane science sites may have already seen my perspective:
    Dendrochronology is an excellent dating technique for archeological and anthropological projects. Matched rings from a known area can tell when logs were felled for a shelter, boat, crib, crypt, etc.
    However, the size of rings in a single tree, a grove, or forest may be affected by temperature, sunlight, water, nutrient s, and/or ambient CO2. These and other factors are variable from year-to-year. I have stumbled across studies where the broader rings in the same isolated grove are seen as evidence in Study A of increased rainfall, and in Study B of increased temperature.
    Dendrochronology has a solid foundation. Dendrothermometry and dendrohydrometry are highly questionable. Looking back a hundred years, who has the ability to track windfalls, lightning strikes, beaver dams, dead carcasses within the drip line, or migrating herds leaving more or less fertilizer? There are far too many variables for the certainty that is asserted in these learned and subtle reports. I take them all with a grain (or more) of salt.

  114. Steffenville, MO virtual survey augmented with on-the-ground pics today. Upload later in the week (target of opportunity my wife happened to be passing by). I see one Glenn Block has been “gettin’ busy” in MO recently –nice! It surely needed it.

    Boy, an updated SS progress thread would sure be nice. . . .

    Oh, btw, if someone is going to do an updated .kml of what’s left to do (and in my opinion, it is about time for one), might I suggest that different map markers be used for sites on the map known to be no longer in service? That’s a very relevant point for most volunteers, as it is almost always a very different kind of experience and investment in time to get those. Not always, but often. It would be very handy if those were marked in a different way on the .kml map from ones thought to still be active.

  115. As a layman, I’m puzzled. I thought that temperature proxies were to be used when direct measurements weren’t possible, such as before thermometers were invented. Why then do Mann, Griffa, the IPCC, and others use tree ring proxies for temperatures in the 20th century (the blade of the hockey stick), when direct measurements, however flawed, are available?

  116. Jolyon Hallows (18:03:06) :

    As a laymen to a laymen.. i would say its to validate the historical data, by showing an excellent correlation with the instrumental record…..

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