Claim: Historical climate fluctuations in Central Europe overestimated due to tree ring analysis

Present warming is extraordinary

POTSDAM INSTITUTE FOR CLIMATE IMPACT RESEARCH (PIK)

Research News

“Was there a warm period in the Middle Ages that at least comes close to today’s? Answers to such fundamental questions are largely sought from tree ring data,” explains lead author Josef Ludescher of the Potsdam Institute for Climate Impact Research (PIK). “Our study now shows that previous climate analyses from tree ring data significantly overestimate the climate’s persistence. A warm year is indeed followed by another warm rather than a cool year, but not as long and strongly as tree rings would initially suggest. If the persistence tendency is correctly taken into account, the current warming of Europe appears even more exceptional than previously assumed.”

To examine the quality of temperature series obtained from tree rings, Josef Ludescher and Hans Joachim Schellnhuber (PIK) as well as Armin Bunde (Justus-Liebig-University Giessen) and Ulf Büntgen (Cambridge University) focused on Central Europe. Main reason for this approach was the existing long observation series dating back to the middle of the 18th century to compare with the tree ring data. In addition, there are archives that accurately recorded the beginning of grape and grain harvests and even go back to the 14th century. These records, as well as the width of tree rings, allow temperature reconstructions. A warm summer is indicated by a wide tree ring and an early start of the harvest, a cold summer by a narrow tree ring and a late start of the harvest. The trees studied are those from altitudes where temperature has a strong influence on growth and where there is enough water for growth even in warm years.

“Medieval archives confirm modern climate system research”

“It turned out that in the tree ring data the climatic fluctuations are exaggerated. In contrast, the temperatures from the harvest records have the same persistence tendency as observation data and also the computer simulations we do with climate models,” says co-author Hans Joachim Schellnhuber of PIK. “Interestingly, medieval archives thus confirm modern climate system research.”

To eliminate the inaccuracies of the tree ring data, the scientists used a mathematical method to adjust the strength of the persistence tendency to the harvest data and the observation data. “The adjustment does not change the chronological position of the respective cold and warm periods within the tree rings, but their intensity is reduced,” explains co-author Armin Bunde from the University of Gießen. “The corrected temperature series corresponds much better with the existing observations and harvest chronicles. In its entirety the data suggests that the medieval climate fluctuations and especially the warm periods were much less pronounced than previously assumed. So the present human-made warming stands out even more.”

###

Article: Josef Ludescher, Armin Bunde, Ulf Büntgen und Hans Joachim Schellnhuber (2020): Setting the tree-ring record straight. Climate Dynamics, DOI: https://doi.org/10.1007/s00382-020-05433-w

Weblink to article: https://link.springer.com/article/10.1007/s00382-020-05433-w

From EurekAlert!

100 thoughts on “Claim: Historical climate fluctuations in Central Europe overestimated due to tree ring analysis

    • Each time I walk through a forest clear-cut I stop and compare tree rings on adjacent stumps.

      They almost never agree with one another. One stump might show that the weather has been sunny and wonderful for the past century, while the adjacent stump records a century of misery and torment.

      Tree ring proxies are voodoo science.

      • “They almost never agree with one another. One stump might show that the weather has been sunny and wonderful for the past century, while the adjacent stump records a century of misery and torment”

        the same tree ring on the opposite side of the tree trunk usually doesnt agree
        Cut the log in 3 foot sections – The same tree ring wont agree on the other end of the log

        • “Joe _ the non climate scientiest{sic} September 10, 2020 at 3:26 pm
          “They almost never agree with one another. One stump might show that the weather has been sunny and wonderful for the past century, while the adjacent stump records a century of misery and torment”

          the same tree ring on the opposite side of the tree trunk usually doesnt{sic} agree
          Cut the log in 3 foot sections – The same tree ring wont agree on the other end of the log”

          It happens irregularly around the tree’s circumference.
          All it takes is damage to a lower cambium level to stress growth layer above;
          or damage to the roots on one quadrant of the tree;
          or a fallen branch’s knot rotting and sickening the tree in that growth.

          As Joe_the non climate scientiest and pochas94 point out so well, trees are unreliable. Even within one tree.
          Trees respond to fertilizer,
          warmth,
          sunlight,
          higher CO₂,
          proper moisture, neither too little nor too much,
          lack of insect attacks,
          lack of bird attacks, especially the kind that encourage insect and fungal attacks,
          lack of fungus diseases,
          proper fungal and bacterial root colonizations,
          healthy root growth,
          full leafing for the entire period of growth,
          minimal frozen ground surrounding the root mass during the growth season,
          etc., etc., and so on…

          Not to overlook; What happens to those trees when dendronologists are not there?

        • Excerpted comment:

          In its entirety the data suggests that the medieval climate fluctuations and especially the warm periods were much less pronounced than previously assumed. So the present human-made warming stands out even more.”

          “WOW”, …… the science based facts is good news.

          Only a couple problems though, this being one of them.

          the same tree ring on the opposite side of the tree trunk usually doesnt agree

          “DUH”, ……. the major reason is, it’s the quality and quantity of Sunlight that each tree receives.

          All sides of all trees do not receive the same amount of sunlight.

          Why does moss grow on the northside of trees?

          In the northern hemisphere, moss most often grows on the north side of trees, according to the Woodland Trust. … That’s because the north side is the shadiest side in the northern hemisphere and the south side is the shadiest side south of the equator.Feb 28, 2020

          • “So the present human-made warming stands out even more.”

            The fact that felt the need to include this statement is just proof that this is what they were paid to prove in the first place.

            What’s happening in the here and now is totally irrelevant to what may or many not have happened to trees 1000 years ago.

        • Indeed. A tree that is leaning, or subject to persistent winds from the same direction (e.g. some coastal and alpine areas), will build up “reactionary wood”. Compression wood on the down-lean side, and tension wood on the other. This will influence both the type/orientation of cells and the ring width, often leading to off-centered and elliptical ring cross sections.

          https://en.wikipedia.org/wiki/Reaction_wood

          However, depending on the wood source dendrological methods can be used to account for this, for example taking ring widths on more than one axis or scanning the cross-section and using software. Of course this still requires the assumption that the differences can be averaged out to something meaningful, and that the difference between specimens and across time are related to the climate variables of interest.

      • Well see. A liberal tree will show a century of misery, a conservative tree will show sunny and nice. You need to only check moderate tree’s.

      • Trees compete with each other. You have a grove that’s growing like weeds but some are dead or dying. If you want to show warming, pick the healthy ones.

        • Behind all the mathematical red scarf tricks of Fourier transforms, Hurst exponents etc., what they are actually doing is a applying a simple high pass filter.

          They multiply the frequency domain by f -(2h0-1) h0=1.03 so basically 1/f !!

          This retains lots of squiggly climatey looking noise and removes any meaningful longer term natural variability.

          This is just another excuse to suppress any natural climate variability from the proxy records.

          • Indeed Greg …. as soon as I saw Potsdam and then further down I read “To eliminate the inaccuracies of the tree ring data, the scientists used a mathematical method to adjust” I knew the fix was in.
            Climate science is truly fooked IMHO.

  1. My first suspicions about tree rings as proxy temps from past eras were triggered by “Mike’s Nature trick” as used to create the Mann et al ‘hockey stick’ graph.

    To wit –
    if tree rings proxies were found to be so vastly inaccurate from when they were able to be compared to the temp instrument record, that Mann et al had to truncate the proxies and graft on the actual instrument numbers (ie Mike’s Nature trick), what’s to say that ALL the tree ring proxies used to form a picture of temps in ancient times were not also vastly inaccurate?

    • They seem to think tree rings are the only proxy metric. They are probably the worst metric out there. Thus, the question is that, if a tree ring study fails in the forest, does anyone care? No.

      • If a tree ring study fails in the forest, and there is no one there to see it fail: has it actually failed? This is one of the great philosophical questions we have never been able to solve.

        • Greg: Fortunately for us all, M&M were there to see THE tree ring study fail. Shellnhuber et al have misspent careers trying to show M&M wrong, here’s another effort that doesn’t pass the laugh test.
          I wonder why they don’t give up on tree rings, they can use their version of “math” to get AGW out of rocks, water, fire….. any essential element. For instance, take ten rocks. Measure something about them. Run a graph for each rock. IF one rock shows we’re all doomed to die of AGW, the other nine are non-conforming samples. That’s how math can work for humanity!

  2. BLM has released a statement explaining that tree ring studies are the product of European white supremacist racist science. Such studies also fly in the face of our modern understanding of Climate Justice. The authors of the study therefor are rayyyciiiss, practicing White Supremacy, and inflicting Injustice on underrepresented groups.

    This study needs to be condemned in the harshest terms, and the authors atone for their sins. Then they must be held accountable for their unspeakable crimes.

  3. I’ve been working on the data for wine production in Germany. In the thirteenth and fourteenth century there were vineyards in Franconia 100 meters or more above the current upper limit for wine production. And that is only because of the introduction in the eighteenth century of frost resistant strains. Less than half of the area that was used for wine production in the period before 1500 is now cultivated, and the decline in acreage coincides with the decline in temperatures after the Medieval Warm Period. Production appears to have peaked in the first decade of the fifteenth century but then fallen off sharply after 1550. By the 1640s, 87% of vineyards had been abandoned. Only in the eighteenth century did winemaking recover.

    • Yes but harvest was later in those regions so it must have been colder.

      Makes sense, doesn’t it?

      (A bit of sarcasm there, before I get a nasty reply).

    • Good comment WB Smith.

      Sara wrote regarding my paper:
      wattsupwiththat.com/2019/04/14/hypothesis-radical-greens-are-the-great-killers-of-our-age/

      “A hypothesis? I don’t think any of it is hypothetical. Too many instances of verified occurrence to back up that that statement to make it a hypothesis.”

      Hi Sara,

      As you know, the scientific progression is Hypothesis -> Theory -> Law, each progression requiring more and more supporting evidence and absence of disproof.
      https://www.thoughtco.com/scientific-hypothesis-theory-law-definitions-604138

      My Hypothesis is limited to radical greens, who support false science and use false fabricated crises to promote their toxic anti-human agenda. As such, there is a mountain of evidence to support my Hypothesis, and no evidence (that I know of) to disprove it. Therefore, over the next few years it may be promoted to the level of Theory.

      If it is a Theory, it will require a nice name, like “Darwin’s Theory of Evolution”. I am not even sure if mine is an original concept – others have probably said this before.

      I will therefore submit, immodestly, the proposed name
      “MacRae’s Theory of Radical Green Rat Bastards”.

      MacRae’s Theory of Radical Green Rat Bastards is a huge time-saver, and based on the past performance of radical greens, it continues to be a highly successful predictor of future green lack-of-credibility.

      Others are welcome to submit improvements to the name – after all, at this time it is still a Hypothesis. 🙂

        • If you used that on Climate Science its gets a pretty good score on it gets points on 2,3,4,5,11,14,19,21 (if you are Mike Mann),26,37

        • It seems the Potsdam pretenders have found that natural variation was quite pronounced. It would also indicate that Michael Mann’s work is inaccurate and irrelevant. That hasn’t stopped him from making a career out of outrageous B.S. thanks to the surrounding environment of politico-activist liars that dominate these garbage sciences. Backed up of course by their Socialist brethren such as Loydo who refuse to read the historical record of utter destruction and death wrought by the Socialist fools and murderers.

      • No, he was awake, just wearing is stupid glasses. Unless he was kidding around. The problem is that he sounds like the former and we cannot tell without a clue.

      • “Hypothesis -> Theory -> Law”
        NO!

        Hypothesis (guess as to why something occurs)
        —> Theory (an attempt to explain a phenomenon as the result of experimentation)

        A law simply describes what happens more than 50% of the times and makes no attempt to explain anything.

        • Charles wrote: “A law simply describes what happens more than 50% of the times and makes no attempt to explain anything.”

          Really Charles?

          My impression is that a Law requires a much higher degree of confidence than 50%.
          For example, the Law of Gravity is pretty reliable, at least within the Terrestrial boundaries of our space/time continuum. 🙂

          • I agree with this point, but I’d say your basic sequence is off. Laws come before theories; the latter are devised to explain laws (as well as less well-defined regularities). E.g. Boyle’s Law came before Dalton’s atomic theory. Ohm’s Law came before theoretical explanations of electricity.

      • Allan posted: “. . . the scientific progression is Hypothesis -> Theory -> Law . . .”

        With all due respect to Allan, readers should understand that those arrows are NOT intended to indicate irreversibility as additional data is accumulated.

        • Agreed Gordon.
          Any solid disproof invalidates or constrains a Hypothesis, Theory or (even a) Law. Knew that.

          “Every genuine scientific theory then, in Popper’s view, is prohibitive, in the sense that it forbids, by implication, particular events or occurrences. As such it can be tested and falsified, but never logically verified. Thus Popper stresses that it should not be inferred from the fact that a theory has withstood the most rigorous testing, for however long a period of time, that it has been verified; rather we should recognise that such a theory has received a high measure of corroboration. and may be provisionally retained as the best available theory until it is finally falsified (if indeed it is ever falsified), and/or is superseded by a better theory.”
          More re Hypos, Theories and Laws at https://plato.stanford.edu/entries/popper/

          To others:
          The notion that a Law predates a Hypothesis or Theory or that a Law requires less conclusive evidence than a Hypothesis or Theory is wrong, imo.
          Examples:
          Catastrophic man-made global warming (CAGW) is a Hypo, disproved numerous times.
          Evolution is a Theory much more credible than CAGW; but still a Theory.
          Gravity is a Law – highly reliable, and resistant to falsification.

          • Right you are, ….. ALLAN MACRAE.

            The problem is that the miseducated do not realize that scientific Law(s) can be and are included within an hypothesis or a theory …… but an hypothesis or a theory cannot be included within scientific Law.

    • Similarly, we have this:

      Let’s face it. If you want a good wine the last thing you will do is head off to the supermarket and buy an English brand. The idea is almost comic. French, Italian, yes. Australian, Californian, Hungarian, perhaps. But English grapes freezing their pips off on a vine in the Midlands, where not enough sun gets through, just don’t really do it for most of us, despite some heroic marketing on the part of British wine makers. Yes, Theale Vineyard Sparkling Chardonnay may be, for all you or I know, a cracker, but who honestly has heard of it? With global warming perhaps this will soon change. Beach recently tripped over a reference to a new (exciting sounding) Scottish wine so anything is possible. link

      Many years ago I planted grape vines in my back yard. There were some nice harvests but eventually trees grew up and shaded the the vines. In that light, it occurs to me that while a frost free growing season is a necessary condition to grow grapes there are also other requirements.

      Are you aware if the monastic grape growers kept records of things like sunshine, rain, and frost?

      • No, but the harvest dates are known way back. French historian Le Roy Ladurie used them to document historical climate changes.

    • It’s also true that the northern tree line has not yet reached the latitude it held during the Medieval Warm Period.

      Fore example:
      Kullman, L., Higher-than-present Medieval pine (Pinus sylvestris) treeline along the Swedish Scandes. Landscape Online, 2015. 42(0): p. 1-14 https://landscape-online.org/index.php/lo/article/view/LO.201542.

      MacDonald, G.M., K.V. Kremenetski, and D.W. Beilman, Climate change and the northern Russian treeline zone. Phil. Trans. Roy. Soc., 2008. B363(p. 2285-2299

  4. What happens to tree rings if the temps stay the same but CO2 increases? Will the rings be wider, like they would be for a warmer year? For example, comparing a tree ring from a normal summer in 1200AD with CO2 at 250ppm vs a tree ring from a normal summer in 2020 with CO2 at 400ppm

    • It depends on the species, but I suspect some types of trees would benefit from additional CO2 which would sort of skew the whole tree ring comparison racket.

      • We never see a genetic twin tree. Trees ‘stunted’ (or altered) at germination due to weak endosperm (or fungus, virus, salinity imbalance, etc) are going to grow differently … not just in the beginning, but throughout the life of the tree.

        Are there differing genetic triggers at germination that change the way the tree grows and utilizes water, CO2, light, & nutrients. Does environment at germination make a difference?

        (Have some plants been programmed to be able to take advantage of environmental changes from the beginning? Does ‘”high” C level in the soils/water trigger a gene that allows the tree to better utilize CO2 in the air?)

        Do these guys that authored this study care?

    • Tree rings respond to changes in temperature, rainfall, CO2 concentration, insolation, soil conditions, shading by other trees, diseases, fertilization by animal populations, which do vary, storm damage, and winter storm damage. If near the coast, they also are affected by high salt intrusion from storms. There are also tree viruses that can impair tree growth and even determine the maximum age of some species.

      It is very narrow-minded to pretend only temperature drives tree rings. Just the loss of the tree next to a given tree can produce growth rings that the narrow-minded would interpret to be massive warming.

  5. “To eliminate the inaccuracies of the tree ring data, the scientists used a mathematical method to adjust the strength of the persistence tendency to the harvest data and the observation data. “The adjustment does not change the chronological position of the respective cold and warm periods within the tree rings, but their intensity is reduced,” explains co-author Armin Bunde from the University of Gießen. “The corrected temperature series corresponds much better with the existing observations and harvest chronicles. In its entirety the data suggests that the medieval climate fluctuations and especially the warm periods were much less pronounced than previously assumed. So the present human-made warming stands out even more.”

    One again, “adjustments” and manipulation of inconvenient data.

    • Yup, got it.
      They flattened the data, then claim it fits their model better.
      “adjust the strength of the persistence tendency to the harvest data and the observation data.”
      But what was their “observation data”, over and above the harvest data???

      See Smart Rock below.

      • They didn’t adjust the tree rings to match models, they adjusted their tree ring proxies to better match their other proxies.

        The error here is assuming that all of their proxies are measuring exactly the same thing and should therefore have identical curves.

        Beyond that, if you find that one of your proxies isn’t fit for the purpose you are using it for, the scientific thing to do is to dump the proxy. You don’t just ad-hoc adjust the data until it looks the way you believe it should.

    • First it was the Hiatus that was adjusted out. Now the Medieval Warm period is under attack. What next, Antarctica Ice expanse? It hasn’t toed the line with the predictions and is currently running above it’s average. Is there an algorithm adjustment on the horizon?

  6. We also consider the central European summer temperatures from the output of the past 1000 (850–1849) run of the MPI-ESM-P general circulation earth system model (Jungclaus et al. 2010). We obtained the data from (Earth System Grid Federation).

    In other words, model output = data to input into your next model. No connection with real-world observations.

    The whole thing looks like a conclusion in search of supporting data. In other words, climate science best practice.

    • The question was asked above.
      “adjust the strength of the persistence tendency to the harvest data and the observation data.”
      No doubt about it. They took model output and called it “observation data”.

      This has to be a new record. A real live “Climate Science” paper, and from the prestigious Potsdam Institute for Climate Impact Research, killed, gutted, and field dressed in one hour flat.
      Well done all.

  7. So they are smoothing an unproven proxy measurement for temperature with another unproven proxy measurement for temperature. Gee, what could go wrong with that.

    • Exactly! Harvest data is strongly influenced by human choices and human conditions. Any number of superstitious beliefs relative to the cycles of the moon, reading of ‘signs’, advice of clergy, etc. This applies equally to planting dates, which in part dictate harvest dates. Disease outbreaks, war, etc. could all delay planting.

      Further, you could have a warm year with spring floods that delayed planting, or a year with an early spring, but late frost, where the initial planting failed and had to be re-sown – thus delaying harvest.

      Harvest date may have some usefulness as one of many indicators to be combined together to increase confidence in an estimate of that years climate, but on it’s own it is not strong enough to adjust other data.

  8. ” So the present human-made warming stands out even more.”

    So it’s worse than we thought…much worser… probably the worst worse so far, but there’ll be much more worse to come, you mark my words … & it will be unprecedented.

    Wish they would use Lego instead of Plasticine for their models/muddles.

  9. “Oxygen isotope studies in Greenland,Ireland,Germany,Switzerland,Tibet,China,New Zealand…..all confirm the existence of a global MWP. An ice core from the Eastern Antartica peninsula showed warm temperatures during this period”.-“Evidence-Based Climate Science ” 2016 – DJ Easterbrook.
    There’s that word again-Evidence.

  10. Reminds me of that old saying.
    With 4 variable parameters, I can draw you an elephant. With 5, I can have him crushing grapes in an oak vat.

  11. The adjustment does not change the chronological position of the respective cold and warm periods within the tree rings, but their intensity is reduced

    That’s what the target was.

    • They buried it and moved on. That is another reason why the practitioners of this dark art of treemometers are not scientists. They may do things that look like science, they may call themselves scientists, but their methods show they are not scientists.

  12. Tree rings have the remarkable property of being either thermometers or rain gauges, according to what suits.

    It’s magic, really.

  13. Tree rings only look at the growing season., early spring through mid fall. Thermometer records show the growing Season doesn’t change much but the cold dormant season is warmer. That being the case, tree rings should miss the bulk of the observed instrumental period warming. Is there something wrong with this logic?

    • Trees also respond to moisture more than what is minor movements in temperature. Moisture as droughts can fluctuate wildly year to year, where temperatures generally do not do so in the summer to summer. The entire field of dendroclimatology is absolute junk science, because as Ross McKitrick has shown the treemometer witchdoctors “pre-select” those tree sections that they think will give them the desired signal.

  14. Here in North Carolina I find it hard to see how trees rings vary with temperature. It’s pretty much warm from April until November. What matters is how much it rains. Wet years like this one has a lot of growth.

  15. Potsdam is THE alarmist hotspot. Even the Mann got embarrassed by some of their claims once on twitter.

    Anything more you need to know?

    PS: the whole made up stuff about tipping points comes from them too. Geological evidence? Negligible.

  16. So, if (big IF) tree rings overestimate fluctuations, then we can ignore all the evidence that we have, that is NOT based on tree rings, and that proves that current glaciars in the highest mountains in Europe were more retired in Roman and Medieval times than they are currently. Hmmm… NOT!

  17. Time to haul out the Greenland studies. They planted barley and raised farm animals including dairy cows. Moreover, many medieval farmsteads are still largely ice covered today. Scotland had a significant wine industry. Medieval tree stumps occur well above today’s treeline. None of these facts require proxies. Just the minimum of common sense.

  18. “If the persistence tendency is correctly taken into account”

    and

    “but their intensity is reduced”

    So they changed from a measure of time to a measure of temperature in order to refute the MWP.

    And we accept this as science? This charlatan word play?

  19. Huh, Tree ring size & CO2…. what about the HEIGHT of the tree? More f ertilising materials induces taller growth, from my experience …. and as has been stated so often in earlier comments – neighbouring trees and along length of SAME tree, there is / can be, NO consistency of tree ring growth….

  20. Quote from the article.
    “If the persistence tendency is correctly taken into account, the current warming of Europe appears even more exceptional than previously assumed.”
    Well they could just have come right out and said ” It is worse than we thought”
    Perhaps the “new information” about climate in past periods derived from tree rings, will also explain how farming used to be carried out successfully on Greenland, but not now as it is too cold to do so, Perhaps it will reveal why, wine production was widely available in England during the earlier warm periods, but today that opportunity is limited to just a few places with high risk of zero production years.
    As Prince Charles is a self proclaimed expert at listening to the trees, perhaps we should ask him what they are telling him at the moment?

    • Prince Charles is busy, having reincarnated into a mortal virus capable of killing millons, like he expressed that was his secret wish.

      • Actually that was his father Prince Philip who has that permanent anti human wish.
        I suspect there are some paternal influences in play, but talking to the plants is a peculiar habit of Charles. Well, it’s what he does when he is not wishing to be a tampon anyway….

  21. The day barley ripens again in Greenland, like it did in the MWP, then it will be as warm as it was then.

    It might actually happen. On Iceland barley growing was resumed in the warm 1930’s after a 300+ year hiatus.

  22. “The corrected temperature series corresponds much better with the existing observations and harvest chronicles. In its entirety the data suggests that the medieval climate fluctuations and especially the warm periods were much less pronounced than previously assumed. So the present human-made warming stands out even more.”

    In Finlands northern part Lappland have whole medieval oaks in svamps. Now oak grows only in the most southern part, about 1000 kilometers from Lappland. And this is observation, so obviously Josef Ludescher of the Potsdam Institute for Climate Impact Research is wrong.

  23. Although we are not officially in a period as warm as the MWP we seem to be using Mediaeval means for predicting the climate….Michael Mann’s tree ring readings have cost us, and are still costing us a lot in terms of mitigating climate change. Reading the entrails in the Wuhan Lab has and is costing us a lot in terms of life/death and the economy…and now I hear it is also a climate change indicator. Both these “technologies” are ruinous and I suggest we stop them at once and let the climate do its own thing as it always has done.

  24. “We apply a low-pass filter to the time-series data, because of a dubious construct we call persistence. Lo and behold, the range is compressed. This proves AGW is even worse than we thought.”

    Tautological, circular numeric masturbation.

  25. I’ve cored a lot of trees and compared ring widths to climate data. What showed up consistently was that precipitation probably plays a bigger role than temperature in ring width. In general, I found a poor correlation of ring width with temperature. In fact, cool periods with higher precipitation sometimes showed wider rings than warm, dry periods, especially in arid climates. The Chinese seem to have gotten good results with tree rings confirmed by other methods. My conclusion about all this is that tree rings sometimes track temperature and sometimes they don’t.

  26. I have read through all the post and see no mention there or in the original story about some trees rotating ass they grow. Some may make more than a complete 360 degree rotation, depending on conditions and their particular location.

    In the early 1950’s, my father had a saw mill he could move from location to location to turn smaller forests into lumber. Sometimes he would discover a log from such a tree and it would be removed from the mill and discarded. The lumber would not be usable for anything.
    Today we can occasionally find a very old ponderosa pine tree that has died and lost all it’s bark and will show how it turned over it’s lifetime. We can also find the remains of such trees on the ground here in Central Oregon.

    I wonder if the study of tree rings based on tree stumps ever account for that tree turning as it grew?

    Paul in Central Oregon

  27. The Tree ring history of Glacier Bay Alaska is used to record the number of growing years between glaciers. And since receding Glaciers in this decade uncovered stumps of trees that were several hundred years old wen the trees above were snapped off, then it is save to say it was warmer then this decade for hundreds of years. And that happened 6 times in the last ten thousand year. Nothing any one says for climate alarmist verbiage is worth listening too. There are cycles to warming and cooling. Try a 1500 year cycle (10,000 / 6). We are little people living a very short time. yes it warms between ice ages duh.

    https://www.nps.gov/articles/historicglacieractivityinglacierbay.htm

  28. The Medieval Warm Period has been firmly established around the world by not just tree ring data but by glacier retreat, lake sediments, temperature dependent biota, oxygen isotopes, deuterium excess, ice rafted debris, and other means.

    https://www.google.com/maps/d/viewer?mid=1akI_yGSUlO_qEvrmrIYv9kHknq4&ll=-1.6538884343610288e-13%2C38.03818700000005&z=1

    Not just that, but the MWP has been historically recorded in written records.

    It’s flat dishonest of the authors to suggest that this tree ring study makes the MWP less of a real thing.

  29. Of hundreds of WUWT comments sections I’ve read, this is a favorite. Thank you all.
    (Confirmed my own tree ring observations as a kid in western Montana. Should never have doubted my young logic.)

  30. Climate Impact Research Institute. Motto: Carbo Carbonis Dioxidenus Malus. Patron saint: St. Alexandria de Occassio-Cortez

  31. From the article: “The corrected temperature series corresponds much better with the existing observations and harvest chronicles. In its entirety the data suggests that the medieval climate fluctuations and especially the warm periods were much less pronounced than previously assumed. So the present human-made warming stands out even more.”

    Well, first of all, there is no evidence of any “human-made warming” in connection with the Earth’s atmosphere, and second of all, we don’t need to use tree rings to show it was just as warm in the past, when CO2 was a minor player, as it is today, when CO2 has increased in the atmosphere.

    All we have to do is look at regional Tmax charts from around the world to see that it was as warm or warmer in the Early Twentieth Century as compared to today. We have actual temperature charts recorded by human beings that demonstrate this. We don’t need tree rings.

    Regional Tmax temperature charts destroy the Human-caused Climate Change narrative. That’s why you never hear alarmists referencing them. But they’re out there.

    Tmax charts

    US chart:

    https://bobtisdale.files.wordpress.com/2018/12/Figure-11.png

    China chart:

    https://bobtisdale.files.wordpress.com/2018/12/Figure-12-1.png

    India chart:

    https://bobtisdale.files.wordpress.com/2018/12/Figure-13-1.png

    Norway chart:

    https://bobtisdale.files.wordpress.com/2018/12/Figure-13-2.png

    Australia chart:

    https://bobtisdale.files.wordpress.com/2018/12/Figure-12-2.png

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