New Study: Two Thousand Years of Northern European Summer Temperatures Show a Downward Trend

In a paper published in the Journal of Quaternary Science, Esper et al. (2014) write that tree-ring chronologies of maximum latewood density (MXD) “are most suitable to reconstruct annually resolved summer temperature variations of the late Holocene.” And working with what they call “the world’s two longest MXD-based climate reconstructions” – those of Melvin et al. (2013) and Esper et al. (2012) – they combined portions of each to produce a new-and-improved summer temperature history for northern Europe that stretches all the way “from 17 BC to the present.” And what did they thereby learn?

As the international team of researchers from the Czech Republic, Finland, Germany, Greece, Sweden and Switzerland describes it, this history depicts “a long-term cooling trend of -0.30°C per 1,000 years over the Common Era in northern Europe” (see figure below). Most important of all, however, they note that their temperature reconstruction “has centennial-scale variations superimposed on this trend,” which indicate that “conditions during Medieval and Roman times were probably warmer than in the late 20th century,” when the previously-rising post-Little Ice Age mean global air temperature hit a ceiling of sorts above which it has yet to penetrate.


Northern Europe summer (June, July, August) temperature reconstruction. Data shown in°C with respect to the 1961-1990 mean. Adapted from Esper et al. (2014).

And so we continue to collect ever more real-world evidence for the fact, that there is nothing unusual, unnatural or unprecedented about the Earth’s current level of warmth.

Paper Reviewed

Esper, J., Duthorn, E., Krusic, P.J., Timonen, M. and Buntgen, U. 2014. Northern European summer temperature variations over the Common Era from integrated tree-ring density records. Journal of Quaternary Science 29: 487-494.

Full paper PDF:


Esper, J., Frank, D.C., Timonen, M., Zorita, E., Wilson, R.J.S., Luterbacher, J., Holzkamper, S., Fischer, N., Wagner, S., Nievergelt, D., Verstege, A. and Buntgen, U. 2012. Orbital forcing of tree-ring data. Nature Climate Change 2: 862-866.

Melvin, T.M., Grudd, H. and Briffa, K.R. 2013. Potential bias in ‘updating’ tree-ring chronologies using Regional Curve Standardization: reprocessing the Tornetrask maximum-latewood-density data. The Holocene 23: 364-373.

h/t to and D.W. Schnare


200 thoughts on “New Study: Two Thousand Years of Northern European Summer Temperatures Show a Downward Trend

    • Yup. I few weeks ago, a paper we published in May was attacked on the basis that if the peer review process had been better and more rigorous, it would never have been allowed to get into print. The objection was not to the proven conclusions (which are very inconvenient in some quarters), but to describing the output metric, which included an invalid calculation step, as having no scientific value. The only ‘value’ I could see was as an object lesson in how not to calculate something.
      New CAGW Defense: If the conclusions are inconvenient but sound, attack the lexicon.

      • The warmists are running scared and it is just a matter of a few years when they will have to answer to all the lies and made to pay dearly for all those billions wasted and as the cold deepens the rage will increase! What will happen then or where are they going to hide?

    • From the paper: “Calibration and error estimation
      The MXD climate signal was estimated by calibrating the combined S88 + E12 chronology against regional June–July–August (JJA) mean temperatures recorded at the Haparanda, Karasjok and Sodankyla meteorological stations over the period 1876–2006. A split 1876–1940 calibration and 1941–2006 verification approach was used for assessing the temporal robustness of the signal (Schneider et al., 2014), and the chronology transferred into JJA temperatures by scaling the record to the mean and variance of the instrumental climate data (Esper et al., 2005).
      That is, tree ring series are statistically scaled up to measured temperatures and then assigned the label “degrees centigrade.”
      The method is not guided by any valid physical reasoning, nor justifiable by any valid physical theory. Statistics is substituted for physics. Methodologically, the process is a-scientific.
      The ordinate values on the head-post plot have as much to do with physical temperature as would a time series in average length of hem-lines.

      • We can always start pumping more CO2 into the atmosphere. Maybe it’ll warm things up. Terra-form the planet, if you will.

  1. Well ‘the Team’ are certainly going to like this one. I guess that they no longer have the influence to get these papers shut out and not published.
    It would be nice to be a fly on Mann’s office wall when he reads this.

    • “Well ‘the Team’ are certainly going to like this one.”
      There have been doubts about how warm the MWP was globally. But I haven’t heard many dispute that it was warm in N Europe.
      As to the cooling trend, well, Marcott et al said in their abstract:
      “Early Holocene (10,000 to 5000 years ago) warmth is followed by ~0.7°C cooling through the middle to late Holocene (<5000 years ago), culminating in the coolest temperatures of the Holocene during the Little Ice Age, about 200 years ago. This cooling is largely associated with ~2°C change in the North Atlantic. "
      North Atlantic. This paper seems to be echoing that.

      • Really?! Then what is all of the hysteria for? Why denigrate people as “deniers”? Why must we “act now”? What is the “hockey stick” all about….if not thoroughly repudiated?
        Why then do we have to pay more for everything in the name of “saving the planet”?
        You might not realize this yet, but in “putting” Willis “out to pasture” some many article comments ago you became his jackwagon. And now, you slyly admit that your entire scare mongering is based on a downward trend in temps!

      • @Nick, “There have been doubts about how warm the MWP was globally”
        Explain the atmospheric/climate mechanism that has Northern Europe 2+ degrees warmer that the rest of the planet for about 2 centuries !!!

      • The reason behind having to act now to global climate change is to make people rich and build another industry that will create jobs. From Government inspectors to manufacturers to investors, they are hoping or trying their best to infuse money into the economy by trying to create another market.

      • Nick
        “…coolest temperatures of the Holocene during the Little Ice Age,…”.
        Thanks, I dont remember seeing that before. Seems to give some credence to any hypothesis that we are warming out of the coolest period in several thousand years. Just that little bit of information should give someone pause.

    • I don’t trust treemometers, but I agree.
      The confidence expressed in the treemometers that made the hockey stick looks untenable now.

      • One difference to Mann et al is that this study used latewood density, whereas Mann’s hockey stick was manufactured from tree ring widths, and very possibly cherry picked tree ring widths,
        It is my understanding that latewood density correlates well with known temperature trends during the period of the thermometer record. Still may be affected by other environmental conditions though.

    • Just eyeballing the chart, it looks like most of the downward “trend” comes from picking 17 BC as the starting date. If they’d picked 200 AD the trend would be flat or almost so. But if they’d started around 325 AD the trend would be slightly positive. So what is magical about any one of these starting dates?
      I view this is just data to be considered when looking at any tree ring proxy study: you don’t get a consistent picture out of them. A rebuttal to MBH98 (as if any more were needed): yes; a finding which actually establishes declining global temperatures over the study period: not so much.

      • AWCDL7, “what is magical about any one of these starting dates” is that the trend indeed has a different sign, depending upon the starting date. Thus, we can say summers were warmer during so and so period, and were cooler during that other period…demonstrating that current summers are perfectly normal (within the normal range), and therefore perfectly natural (uncorrelated with anthropogenic CO2 emissions).

    • Not really, It is simply missing “Mikes Nature Trick” to “hide the decline” that’s all. Splicing the Satellite measurements since 1069 on to the end should produce the requires Hocky Schtick (or not)

    • When the MWP shows up in your data that confirms that you are either barking mad or barking up the wrong tree. They should have left this study to the experts who know which trees hold an accurate record of historic global temperature variations, these tree are obvious better used as firewood. .

      • …confirms that you are either barking mad or barking up the wrong tree

        HeHe. Almost went over my head there Julian.

  2. I don’t care that it lends some support to my interpretations of the general climate trend, I still don’t see that anyone can get temperature from tree rings. Until they can separate out who peed on the tree, what died underneath its branches, and how much it rained each year, I’m not buying.

    • HR, that was my first thought also. The trend just shows that the climate has gotten generally more challenging for trees – not why.

      • I agree, but you can see the Roman warm period, Dark Ages, Medieval warm period and then the Little Ice Age. All other things being equal (though of course they aren’t) you would expect trees to do better in the warmer periods.
        The graph doesn’t show a recovery from the LIA. Dendro is hard. Far too hard for Michael E Mann.

    • @H.R.:
      And don’t forget that (at least for the Pacific N.W. where the study was done) bears eating salmon and pooping on the trees is the major source of nitrogen. So you also need to know the number of bears, the size of salmon run, and how far the bear like to walk from stream into the woods for ‘privacy’ while they ‘think’…
      And, perhaps, a ‘back scratch bark metric’ to assure that those trees especially suited to a good post dump backrub are not over sampled. 😉

      • E.M.
        “[…] and how far the bear like to walk from stream into the woods for ‘privacy’ while they ‘think’… “
        Major chuckle! Thanks for the giggles.
        P.S. Headed your general direction in February ’15 with some 13/0 hooks and wire leaders. I ain’t goin’ bluegill fishing.

      • The recent stories about how Yellowstone was transformed right down to the flow of the rivers with the reintroduction of wolves shows this as well. If the wolves had diminished and recovered from disease instead of hunting, the same macro environmental effects would be seen and been attributable to entirely natural causes. How can we know what factors go into tree growth when such seemingly minor factors as the fluctuations and diseases in the animal population can play such a large role.

    • Second the motion. The only thing you can glean with reasonable certainty from this study is how good or bad it was for the trees. Anything else is handwaving.

      • mikerestin
        December 18, 2014 at 11:21 am
        I have difficulty comprehending how one can glean temperature from a tree.
        Way too many factors affect a plant’s wellbeing than just temperature.

        If the tree starts to smoke, it’s way to hot to hang around it. (Or its name is Treebreard and he’s been hanging around Hobbits too long.)

    • Yup, trees used to be happier, but we wonder why. If CO2 is really higher than it used to be, then trees are lacking something that is inhibiting the increased growth we should be seeing from increased CO2.

  3. No hockey stick here. Did the brief spike in temperature near the end of the chart occur in the 1930s? Nothing after that even comes close, despite increasing CO2. But you can still get a hockey stick if you append the output of climate models onto the chart. So all is not lost. 🙂

  4. The lessons of history are clear :
    Clearly, the Roman Empire’s imposition of a carbon tax successfully cooled the planet,and the trick was repeated 1,000 years later by the Aztecs.
    Unfortunately, both Empires subsequently collapsed.
    Quite the dilemma…….

  5. For tree rings, ‘The Thrill is Gone’. It has been largely destroyed by the egregious biased selection of samples (I imagine the preconceivers even looking at non-supportive samples and throwing them away), the casting about for novel statistical manipulations to get the desired result (when highly convoluted methods are needed, the study is junk), disappearing of historically well known warm and cold periods, the divergence problem which begs the question: why would we trust a method for gleaning historical temperatures that doesn’t work for the instrumental record (here I don’t have to imagine that they threw out the decline). Finally, individual researcher biases in the compilation of files. Noise is very useful because it gives you a range of possible “values” to choose from. For example, does anyone believe that the CAGW researchers have ever underestimated the warming?

  6. H.R.
    I agree with you. Rings tell you the age; width of rings tells you the growing conditions of which temperature is one.
    But what this paper does is, as Lonnie says, to give the lie to the hockey stick or at least provide a realistic, properly researched view of the last two millennia which comes to a different conclusion from MBH and chimes with other data sources — some reliable, some maybe anecdotal — all of which posit the existence of warm periods at least as warm as the one recently ended.
    So, game on!

      • David wrote:
        “Too bad the GISP-2 ice cores don’t show the past 150 years”
        And then David posted an image
        “Here is another great chart from J Box, et. al”
        David, that’s a lovely, lovely chart of the past 150 years, but the article was discussing a 2,000 year trend and I posted an image of a 10,000 year trend. Everyone is talking big picture here. If you look over at the right hand side of the image from the Journal of Quaternary Science Reviews, you’ll see they have included something similar to the image you posted. You can see how it fits in the big picture.
        Let’s hope the earth can reach the temperatures of the glory days over towards the left side of the 10,000-year ice core graph, eh? As it stands, over on the right, we’re in the sucky portion of the temperature range right now.
        P.S. I really enjoy geology and from a geological perspective, this temporary several-million-year (so far) ice age seesaw of glacials and interglacials will soon come to an end. Humans might not be around to see whether the Earth winds up as a snowball or Miami Beach-from-pole-to-pole, but this ice age will come to an end.

      • You posted a 10,000 year trend for the top of the Greenland ice sheet. I just showed you what the “trend” has been on the top of the Greenland ice sheet in the past 150 years. I suggest you combine the two of them and tell me what it looks like.

      • David,
        Talking short term, the general trend from the Little Ice age is up. Let’s hope it keeps going. I had a mile of ice over my back yard at one time and if it starts coming back, my property value is going to plunge.

      • Here’s the combined image:
        Temperature scales are matched and line is drawn to the latest average marked on the second image. The upward line follows approximate time scale of the first image. It should probably be even steeper to be correct.

      • The GISP-2 Ice Core dO18 isotope data has been tainted because it has been calibrated to the borehole temperature models.
        They threw out the traditional dO18 isotope to temperature conversion formula that would apply to the Greenland Summit (the relationship of which is scientifically measured and even has International Protocol-type standards) and they used a different conversion formula based on borehole temp modelling.
        This has set-back Greenland ice core science by 20 years. The Antarctic ice core scientists have not used this faulty method because they have higher ethics than the Greenland ice core scientists such as Richard Alley.
        The numbers can be redone with the proper formula and they would match up to thermometre measurements. The temperature changes (the last 7000 year decline) would be cut by about half with the proper method.

      • OK Bill Illis

        Post a graph like the one posted by Janne that incorporates what you consider “corrected” GISP-2 data combined with the J Box GRIP data.

      • David & Janne,
        Try selling that graph to Otzi, and the Vikings whose farms are still emerging from the permafrost. Yeah, I know they’re all dead, but I’d bet they’d get a chuckle out of it. Come to think of it Hannibal might get the giggles, too.

      • It is surely ironic that, in thread where people have complained about Mann’s splicing of different datasets, that graph posted by H.R. pops up. This has known major problems. The timescale on the horizontal axis is wrongly labelled (it is not years before 2000AD) and a really silly estimate of modern warming has been spliced onto the end of the ice core record. If you really wanted to splice records, it would look like Janne’s graph. Of course if Bill Illiis is correct the ice-core section needs revisions as well. All in, it would be better just to scrap that graph entirely.

      • Actually, Janne, you’re splicing the GISP-2 temps to the “average annual temperatures at the GRIP site.” Note the two red crosses in the second graph that indicate the GISP-2 temps. Given the difference between the annual temperatures at the GRIP site and the GISP-2 temps for 1847 and 1855, the GISP-2 temp graph would have to be adjusted upward by over 2.5° to make it somewhat comparable with the GRIP site. And note that you’d still be splicing a low-resolution graph to a high-resolution graph. GISP-2 being ice core doesn’t show annual temperatures.

      • David Socrates: OK Bill Illis. Post a graph like the one posted by Janne that incorporates what you consider “corrected” GISP-2 data combined with the J Box GRIP data.
        Done. But first of all, the GRIP site is not the same as the GISP2 site. They might be only 28 kms apart, but the 20th Century temperature average is about -31.0C at GISP2 and has been -29.9C in the last 10 years.
        GISP2 ice core temperature data for the past 13,000 years using the proper formula and the borehole calibrated one they like to use (maybe they like it because the Younger Dryas cooling looks more ominous. Borehole temperature theory is based on scenarios of how temperatures migrate through the ice/ground and there can be a wide variation in the scenario solutions used. In this case, they continue to use the wrong one for Greenland’s ice cores.)
        Then the last 9,000 years. Maybe not that much different but there is a problem with the calibration.

      • On second thought, we have David Socrates and Janne trying to pass off a Skeptical Science chart of the GRIP site as something contained in Jason Box 2009.
        This chart is NOT in Box 2009.
        GRIP is not even in the sites listed in Box 2009. The closest station is the GISP2 site or the Summit Camp which is reported as an annual average temperature of -29.5 in the paper. The average annual temperature recorded by the Summit Camp staff is -30.2C.
        So we have a number of posters here trying to induce doubt about the GISP2 temperature record, by trying to pass off an obviously fake chart from Skeptical Science. This is not the first time we have seen this, it is about number 100 now.

    • jimmi_the_dalek
      Nicely said. I’ve no quarrel with your points. I have always only viewed the ice core graphs – or really all of the proxy reconstruction graphs – as only useful for the broad pictures that they paint. I’ve never been convinced who, if anyone, has ‘correct numbers.’ That’s why I always prefer the inarguable evidence that may not have any particular or exact temperature associated with it, but shows that the climate has “been there and done that” before the current climate study funding orgy.
      I can’t argue with the physical evidence of the 30-40m thick layer of limestone from the shallow seas that covered my backyard nor the evidence of the mile-high glaciers that more recently covered my back yard. Now that is climate change. I cannot argue with the tree lines much further north than today or the various higher sea levels recorded in coastlines around the world or more recently, Otzi or Hannibal or the Viking farms emerging from the Greenland permafrost. I don’t know that I’d accept any value given as the temperature for those times that were obviously warmer than the present, but it’s plain to see that those times were warmer than the present.
      Now the original topic was long term temperature trends and whether you use the original or new and improved ice core graphs, the glory days are long past in this interglacial. If I have to pick between any scientificky-looking graph and Otzi or a tree line or a green Sahara, the graph loses every time. If they like their graph, David and Janne can keep their graph, but I won’t call the Viking farmers liars about it being warmer back in their day.

      • So, are you saying that you don’t believe the GISP-2 graph you originally posted?

        Make up your mind

  7. According to Greenland Ice Cores, temps have been dropping for the last 3,000+ years, so no surprise there.

  8. This new paper is in complete accord with my forecast of a coming cooling based on the natural 1000 year (as in the Fig above) and 60 year quasi-periodicities seen in the temperature data and using the 10Be ice core record and neutron count as the best proxy for solar activity.
    For a description of the method used and discussion of the inutility of the IPCC climate models for climate forecasting see

    • Nonsense. A 1000 years ago there was 400 years of warmth per the figure in this post [the Medical Warm Period; perhaps you know…], so a 1000 years hence [i.e. now] we are in for another 400 years of warmth, if there is a 1000-year period in climate [which I doubt in the first place].

      • Leif
        The medical warm period? Are you using an iPad with a mind of its own?
        Mind you, bearing in mind the scorn we tend to pour on tree rings we all seem to be accepting the results of this study rather quickly merely because we like the answer. However, at least it is a summer time study, when trees do grow, rather than extrapolated over an entire year.
        CET shows it has been warming up for some 300 years so there is no reason to suppose it won’t continue for another century or so.

      • Leif,
        The end of the Holocene is likely near, based on several previous interglacial lengths. A few cycles within the interglacial may be just response to a weak forcing, but the forcing driving the glacial to interglacial changes are likely stronger. Thus as we near the transition, the 1000 year or so weak cycles would not necessarily repeat again. That does not mean there were no cycles in the past. Data is the only way to determine that. As an aside, there are many forcings and internal lags in the Earth’s climate, but that does not preclude some quasi-periodic cycles popping up then stopping. However, the only thing that counts is DATA, not models or vague efforts to explain why temperature varies. The point I am making is that you cannot predict a new 400 year period of warmth or how long before cooling becomes very large from past data to present. We just don’t know.

      • Leif for the width and amplitude of the 1000 Ad peak see Fig 9 (ChristiansenFtg 5)at
        The shape of the current peak is most likely something similar.
        For the 1000 year quasi-periodicity see Fig 5
        There is a variable time lag between the solar activity peak and the various climate metrics – TLT (RSS) SSTs OHC peaks etc. .We are just past (RSS) or just approaching these peaks. We passed the Solar activity peak at about 1991 in Fig 14 and the definitive drop is seen in the Ap index at 2005-6 at Fig 13.
        We are right at the neutron peak for cycle 24 and past the SSN peak – Feb 2014.
        Within a couple of months the neutron count will drop sharply as we start to approach the 24-25 minimum.

      • “CET shows it has been warming up for some 300 years so there is no reason to suppose it won’t continue for another century or so.
        no reason to suppose it will continue.

      • Leif do you accept the accuracy of the GISP 2 graph at HR 11.27am ? Tony B or anyone else, is it accurate or not and why? Thanks.

      • Mosh says there is no reason to expect it will continue warming over the next century
        So you appear to be saying that we have reached the limits of the warming that is claimed to be caused by co2 ? Sensational!

    • Those three nice warm-peaks are about 1,100 years apart. Not so bad as periodicity goes. But before that it is random noise.

  9. The provided graph shows a larger number of well-below points using the gray area as reference compared to the up spikes. [They use 1961-1990 mean. Why? Not that it would make a big difference.]
    Without getting into the CAGW issue, it seems a prudent society should be prepared for cold snaps as happened in North America the past winter.
    Sunset is occurring less late this week than last week.
    Sunrise does not cooperate until January 6th.

  10. I will point out, that the downward trend results from the truncation of the series at the left end (the roman warm period), remove that (either driving the series to earlier, or leaving the roman warm period out) and there is no trend.

    • Start 1000 years earlier and you have to deal with the Minoan warm period which was likely warmer than the Roman period. Before that there was the Holocene warming period. There is ample evidence that our planet has cyclical periods of cooling and warming and another warming period was about due at the start of the 20th century.

  11. What this paper shows is that there is a debate in regards to what tree-ring proxies show for surface temperatures over the last 2000 years. Mann is not a professional scientist because he claims there is not and should not be a debate in climate focused science. He is anti-science in his no-debate position.

  12. Did the Little Ice Age get averaged out in the graph? or is not evident in this dataset? The graph doesn’t seem to show it. The article mentions it briefly, but the graph shows a recovery from the warm period, followed by fairly steady temperatures. There is no apparent cool dip and recovery.

  13. Well the headline graphic is nice, but there is a message there.
    Just suppose that Lord Monckton had been with us for those 2,000 years, and monthly putting out his trend line graph, every month for those 2,000 years.
    Well he would have had times when he could say: guess what folks, it really is warming; or he could say: yes we are really on a cooling binge. And he could certainly at times have told us. There has been no statistically different from zero trend for xyz years and pq months.
    And he would be absolutely correct.
    Well he is absolutely correct right now, when he says it has been zero trend for 18.pq years.
    All of which points out that a presumed linear trend, over any climate interval whatsoever, is not of any real scientific value.
    True or not, it tells us nothing about what physics is active in the system to cause things to do what they appear to be doing.
    But it sure gives ammunition to skeptics to resist the ‘sky is falling’ insanity.
    Keep your meter running Christopher. Sooner or later the MSM even may get the message. CO2 is clearly NOT driving the present climate behavior.

    • As you rightly point out, it’s a question of perspective in time. Unless we get to know some of the causes for theses variations, we can speculate all day long and nobody can prove or disprove the conclusion of this latest study. In any case, he study hasn’t measured the temperature, it has only measured a proxy which has yet to be proven to be a proxy of — temperature.

      • The validity of the specific proxy being used should always be determined in the individual paper in which it is presented. After all, no conclusion is possible FROM the proxy data until the evidence is weighed that the proxy correlates with temperature.

    • Just suppose that Lord Monckton had been with us for those 2,000 years, and monthly putting out his trend line graph, every month for those 2,000 years.
      Well he would have had times when he could say: guess what folks, it really is warming; or he could say: yes we are really on a cooling binge. And he could certainly at times have told us. There has been no statistically different from zero trend for xyz years and pq months.

      If he were scientifically honest he would say “Sorry, averaging temperatures is physically meaningless. Nothing to see here.”

  14. I have a paper downloaded on my computer written by the Australian scientist David Archibald that he wrote in 2007 entitled “The Past and Future of Climate”. In it he sates that
    “Since the Holocene Optimum, we have been in long term temperature decline at about 0.25° per thousand years.”
    I guess he was right!

  15. I am waiting for our resident AGWer’s to show and explain how this can’t be right and even if it is we’re all gonna die anyway from CO2 toxicity.

  16. Leif says that there should be 400 years of warmth (similar to the medieval warm period), if there really is a 1000 year cycle.
    Depending on when you think the nadir of the Little Ice Age was, we may have had nearly 400 years of warmth since then already. Warmth is relative. If we reached a zenith recently, in general it may well be downhill from here.

  17. The hockey stick replaced by a pool cue. Looks promising to me, if elegance and precision is promoted instead of gang fights.

  18. Michael Mann will be right on this. Tree rings at thirty paces. I don’t have much confidence in tree rings, even if they do give the result I think is correct.

  19. Hmmmm.
    Since these tree-rings are recording moisture, more than temperature, they seem to have proven that it was:
    Wet in the Roman period. 0AD
    Dry as the Western Roman Empire fell. 400 AD
    Wet in the late Dark Age. 1000 AD
    Dry in the Middle Ages onwards. 1400 AD plus.
    Or am I missing something here……?

    • ralferris No – in general cooler periods are dryer and warmer periods more humid – although there is considerable regional variation as the climate belts and winds shift north and south.

      • Whether tree growth correlates with temp or moisture depends upon which is the limiting factor in a given area. Rainfall is high in Northern Europe, so it is not the limiting factor there. Temperature is probably the controlling factor, but what aspect of temperature? Length of growing season in Northern Europe is probably more of a factor for tree growth than peak summer temperature.
        The 2 may correlate. If they do, since humans tend to measure summer warming by peak temperatures, the trees and humans may even agree on which summers are weak, which strong.

    • They say this is based on density of late season wood rather than ring thickness. That may correlate better with temperature, but than again it may not. I imagine one would have to do a very detailed (and probably impossibly expensive) botany experiment with these species of trees where one had thousands of green houses set up to control for all the various temperature, nutrient, CO2, and water profiles and grow trees for a hundred years and see how the ring characteristics lined up against the control parameters. Then we might get to the bottom of the whole treemometer problem.

  20. Treemometers may not be a reliable source for the temperature record but they may be a good guide to general liveability conditions for life on the Earth.

  21. Interestingly we were always told the Viking raids and settlement were due to poor cold seasons but this record seems to suggest the warming of the Eighth, ninth and tenth centuries allowed their expansion, particularly into a less frozen Russia. Not so much victims of climate shift but rather opportunists.

  22. I seem to recall something like Briffa’s tree ring data graphs showed only one tree with a hockey stick, and that was the one used by Mann. Can anyone confirm that?

    • You’re way off. In Mann’s original hockey stick, Briffa’s Yamal series was not used. Mann obtained his HS by overweighting one set of cores (American Southwest Bristlecones) over all others. Briffa did something similar with his One Tree in Yamal, but his is a different reconstruction.

  23. The trouble is if we argue that tree make has good a guide to past temperatures has pine cones do to future temperatures , when it comes to Mann and co ‘work ‘ Then we cannot be happy with them when the produce data we like .
    The reality is any historic proxies in this area are ‘problematic’ to say the least , ‘better than nothing ‘ and ‘we think’ are issues which dog proxies to such an extent that in reality their value , for or against , AGW has to be consider as poor at best. We would never expect such poor quality modern measurements, can we really justify accepting them from the past on the grounds of ‘there better than nothing ‘ given what is being based on them?

      • No one says that tree rings don’t respond to local climate, David. But temperature is a thermodynamic quantity. There is no physical theory that permits converting tree ring metrics into temperature degrees. Term assignment by statistical fiat is not science.

      • Here’s a specific answer David. When several proxies show the same thing, what “thing” are they showing?
        Your question implies that the shapes of proxy series are uniquely determined, i.e., by a single causal element.
        Your implicit assumption is unwarranted. Proxy shapes are multiply determined. The impact of each causal element is unknown. Different arrays of multiple causes can produce a proxy series of similar shape.
        That means proxy series can have similar shapes even when the array of causal determinants is disparate. The proxies then are not showing the same “thing.” They are merely statistically correlated. No specific physical meaning can be extracted from that correlation. No one knows what “thing” it was that caused the proxy series to have that shape, because there is no valid physical theory of proxy structure.
        That judgment includes proxies that happen to be correlated with measured temperatures. No one knows why certain proxies correlate with temperatures. It’s just asserted in the field that correlation with temperature implies causation by temperature. That assertion is entirely unjustifiable, physically.
        The take-home realization as regards science, David, is that when an experiment cannot produce a unique solution, any specific interpretation of the observable is impossible. Any interpretation that is forced, such as we see in the Esper paper (the forced interpretation is, ring density = temperature), is spurious and physically meaningless.
        The fact that such nonsense is ubiquitous in proxy climate studies, has been so for 20 years, and is generally unchallenged, indicates only that the entire field has descended into pseudo-science.

      • David,
        I have seen so many of these multiproxy studies examined in detail at Climate Audit.
        It is clear that there is only one temp. proxy that has any demonstrate temp. dependency: d18O.
        Even that proxy is tricky in such applications as cave deposits.
        Otherwise, the temperature proxies fall short of my standards of scientific rigor. So, no thanks. As Pat Frank points out, these temp. proxies are just bs flung on the wall.

  24. Reblogged this on The GOLDEN RULE and commented:
    So where is the evidence that Carbon is a significant factor in global temperature trends?
    Air pollution needs controlling, but what has that to do with carbon controls and costs?
    So where is the justification for the political and financial controls?
    Perhaps world government agenda is the real reason!

  25. Reblogged this on Public Secrets and commented:
    Bad news for the Warmist cult: Empirical evidence shows not only a millennia-long cooling trend, but that prior warming periods were warmer than the late-20th century peaks. Darn those “inconvenient truths.”

  26. The next thing you know Mike Mann will come out and say tree rings is a poor proxy for past temperatures.

  27. Additional to Jan Esper:

    In so doing, the researchers have been able for the first time to precisely demonstrate that the long-term trend over the past two millennia has been towards climatic cooling.
    “This figure we calculated may not seem particularly significant,” says Esper, “however, it is also not negligible when compared to global warming, which up to now has been less than 1°C. Our results suggest that the large-scale climate reconstruction shown by the Intergovernmental Panel on Climate Change (IPCC) likely underestimate this long-term cooling trend over the past few millennia.”

    A certainly well known paper from 2012

  28. Does a tree core produce the same results if you core the tree from the north side, the east side, the west side or the south side? Nope.
    Does a tree core produce the same results if you core the tree 2 feet from the ground, 4 feet or 10 feet from the ground? Nope.
    Does a tree core match a nearby tree that has the same age? Nope.
    If you core a bristlecone pine tree, what do you get? Nothing of any use. The tree is three-quarters dead on a continual basis and the 3 quarters is constantly moving around the tree throughout its 5,000 year lifespan. It tells you nothing about temperature, just which one-quarter of the tree was alive in the year 553 AD. Naturally, these trees form the main part of the hockey stick. Random cherry-picking potential that is.
    The current tree ring science is more like astrology.
    They could make it a real science again, If they used carbon dating and proved a dO18 isotope-temperature relationship. Then they could use the carbon dates and the dO18 isotopes like the ice cores do. But i think this has only been tried one time.
    The other use of tree rings and carbon dating is to find the northern tree line limit with fossil trees. Naturally, this shows a warm Holocene and a warm MWP and a cold Little Ice Age and no northern expansion of the tree line in recent times. Plant a tree in the Yamal Peninsula where forests grew naturally 5,000 years ago. Will it survive today? Nope.

    • My feelings exactly . When we took the children on country walks and came across the stump of a cut tree we would get them to count the rings and estimate the tree age and also told them that the pattern of thick and thin rings could be used to determine the age of timbers in , say , an old manor house because thickness depended on how good a summer it was that corresponding year..
      Then of course their little fingers would trace the same ring around the trunk and point out that it was thick in one part and thin in another and they would look to me , a bit suspiciously, for an explanation . A bit of waffling , then the walk resumed with 3 small boys having a somewhat diminished respect for the superiority of adult knowledge.

      • Ha, nice one – your kids did the same, eh?
        This is the trouble with kids, they have no preconceived ideas, no specific creed to follow, and a degree of honesty boardering on the suicidal. (quote: ” Granny, why did you not shave this morning…….?”)
        And yes, the tree rings are all different shapes and sizes around the tree, as they gleefully pointed out. How can dendrothermists possibly derive a tree-ring profile, based upon any degree of scientific honesty?
        If you were coring trees [from] London in many decades time (the ash, I think), you would see that London was gripped by a severe Ice Age from 2010 to 2014, with tree rings measured in micrometers. Actually, it was a severe blight infestation – but not according to the dedrothermists…..

      • Remember that a cut tree stump is but a two dimensional sample of a three dimensional object, and that just one of many such objects.
        Tree core boring, is even worse. You get a one dimensional sample of a four dimensional object.
        Pick a lucky angle at a lucky height on a lucky tree, and you might believe anything, you find.
        If somebody had bored a six inch hole 18 feet deep in South Africa back a100 or more years, they might have concluded that the whole of Africa was sitting on a layer of flawless type II-A diamond, from the core that they retrieved.
        Instead they had just found the smaller piece of the Cullinan Diamond. Well actually it was sitting in the wall of an 18 ft deep tunnel somebody had already cut, destroying the other piece in the process (maybe).
        That is why we have a Nyquist Sampling Theorem.
        To stop people supposing, what that object really is, that they are touching in the dark.

  29. If I read the comments above correctly, a person should never put a solved-for trend line on climate data. Person A will say it’s cherry picking, and Person B will say there’s not enough data, or not the right kind of data, to put a valid trend line on.
    That’s cool. Sauce/goose/gander. Let the data speak for itself, and let each person draw their own conclusions, because the so-called “experts” are certainly not in agreement.

  30. Re:Dr Page @ 12:15 The present solar cycle is not yet down for the count. Instead of a couple months, try 2-3 years or more.

    • Victor See graph at
      The Nov number was 70.1 and needs to be added
      Peak cycle 24 SSN was Feb 2014 – the neutron count low ( activity peak) usually lags by 1yr+/- so we are getting close to neutron count low ( activity high )
      The actual SSN will vary widely above and below the blue line on the way down.
      Are you really suggesting that the 24 SSN peak is still 2 – 3 years away? That would be a very unusually long cycle.

  31. The problem with proxy data is that they only approximately record conditions in one particular location.
    As a geologist, I’m more swayed by “macro” data that reflect (at least) regional changes over long periods.
    Where dead-tree forests are found above modern tree-lines, I have to conclude that conditions were more favorable (warmer, wetter) than today when those dead-tree forests grew.
    Where modern continental glaciers melt back and expose former forests and human habitations, I have to conclude that conditions were more favorable (warmer, wetter) than today prior to the advance of these Little Ice Age glaciers.
    These observations are not local or sub-regional. They have been validated in both northern and southern hemispheres – these warmer past climates are truly global.
    It’s also demonstrable that, prior to about 2 million years ago, the entire planet was far warmer than today – for millions and millions of years. Modern mammals, apes, poley bears, and homonids all evolved and survived those warmer conditions, and evolved to adapt to the anomalously cold conditions of the Pleistocene and Recent epochs
    CO2 doesn’t make a bit of difference on the geologic timescale

  32. Many of these posts are missing an important point. The tree ring data and the GL ice core data measure temperatures at very different parts of the globe. There is no reason to think northern Europe and high-altitude GL should change temperature proportionally to each other.

  33. Tree are useless as a temperature proxy, because they react at least as much to precipitation. So this study is of zero value.

  34. From Esper et al., 2012
    Solar insolation [radiation] changes, resulting from long-term oscillations of orbital configurations, are an important driver of Holocene climate. The forcing is substantial over the past 2,000 years, up to four times as large as the 1.6 W m−2 net anthropogenic forcing since 1750, but the trend varies considerably over time, space and with season. Using numerous high-latitude proxy records, slow orbital changes have recently been shown to gradually force boreal summer temperature cooling over the common era. Here, we present new evidence based on maximum latewood density data from northern Scandinavia, indicating that this cooling trend was stronger (−0.31 °C per 1,000 years, ±0.03 °C) than previously reported, and demonstrate that this signature is missing in published tree-ring proxy records. The long-term trend now revealed in maximum latewood density data is in line with coupled general circulation models indicating albedo-driven feedback mechanisms and substantial summer cooling over the past two millennia in northern boreal and Arctic latitudes. These findings, together with the missing orbital signature in published dendrochronological records, suggest that large-scale near-surface air-temperature reconstructions relying on tree-ring data may underestimate pre-instrumental temperatures including warmth during Medieval and Roman times.

  35. Can I just go back some way to Janne’s posting of the two graphs. Call me old fashioned, call me a retired risk analyst (if you must), but I couldn’t help noticing that the time scale of the two graphs overlaps by a number of years and that to the nearest degree the GRIP data is roughly 5 degrees warmer during that period of overlap. That suggests to an old school chap like me that any comparison is utterly meaningless.

  36. So Anthoy Watts has got his logic wires comprehensively tangled (once again).
    “And so we continue to collect ever more real-world evidence for the fact, that there is nothing unusual, unnatural or unprecedented about the Earth’s current level of warmth.”
    A study, not in Europe (a small part of the earth’s surface), a study not even covering Northern Europe (an even smaller place), but a study covering “northern Scandinavia” (part of Northern Europe) can be extrapolated world-wide??
    Would one warming weather station’s data be considered “ever more real-world evidence for the fact that” the world was warming? I think not!
    [ dear “idiot”, you’ve got some issues…
    1. The article was written by Craig Idso at CO2 Science, not Anthony – note the hat tip
    2. Anthoy is actually spelled Anthony
    3. You seem OK with small regional sampling such as Mann’s Sheep mountain Bristlecones, now debunked or Briffa’s Yamal YAD061, shown to be a sample bias of one.
    You’ve definitely lived up to the ‘village idiot’ name you’ve given yourself, Rick. Keep it up, we need more idiots like you. – Anthony]

    • Paleoclimate data from all over the world show that the planet has been in a long term cooling trend for at least 3000 years. Take for example the polar regions. The Greenland ice sheet cores clearly show declining peak warmth from the Minoan Warm Period, c. 3300 years ago. The East Antarctic ice sheet, largest depository of fresh water on earth, quit retreating about 3000 years ago, as shown by soil radionuclides around it.

  37. Everyone here knows that the silly, popular culture questions and statements about global warming “belief” WITHOUT any reference to a starting date are just that- silly, and sometimes intended to obscure rather than illuminate. Each of us can show agreed upon warming and cooling trends of various lengths by cherry picking our dates. Sure, there are also disagreements about some trends when the instrumentation, proxies, or markers are disputed.
    How can we prevent the further dumbing down of science by the journalists, the pundits, and the sometimes ignorant social scientists who talk about belief, but are ignorant of data? It sure appears that many climate scientists and the scientific academies themselves are allowing this to happen for reasons often discussed here. I’m pessimistic and see no hope of turning this ship around soon until the scientific academies take a more principled and scientific approach to the “belief” doctrines that have replaced climate science.

  38. You think the downward temperature trend is from volcanoes, but you’re wrong. It’s from our savior Al Gore and his carbon taxes. Al Gore has saved the world. Actually he has saved the entire universe!!!

  39. Socrates / Janne ; Wouldn’t it make more sense to align the two series to the common time period that Janne marked on the weather station chart???

  40. For a look at (and an excellent visual demonstration of) how cycles of different lengths can oppose or combine to cancel or enhance each other, see the ‘Newton’s Pendulum”

    It is interesting to see this and think about the temperature swings from various natural and cyclical forcings.

  41. You wrote quite correctly: “when the previously-rising post-Little Ice Age mean global air temperature hit a ceiling of sorts above which it has yet to penetrate.”
    However, according to the plot of the 934-year and superimposed 60-year cycles in the scalar sum of the angular momentum of the Sun and all the planets (which correlates with Earth’s climate cycles as seen here) we have not yet reached the maximum in that 934-year cycle. That maximum will be reached after the next 30 years of warming from 2028 to 2058. Because that maximum will probably be about 0.3 to 0.5 degrees above the 1998 maximum, that could level out the long-term cooling trend discussed in the article. I suggest it is only being seen as such because it is not based on the predicted maximum in the current 934-year cycle.

  42. Basically, then, this trendline matches Mann’s trendline – except for the ending 20 decades. But because he homogenized the data so much, he washed out the MWP and the LIA.
    When he did that, and I saw it, it was too much for me. He simply erased two periods – one up and one down – that DID exist, so there had to be either something in his methods or he had to do some serious explaining. “Extraordinary claims require extraordinary proof.” The climate community and pols let him get away with his extraordinary claim – and then they made THAT into the main stream thinking.
    Don’t blame Mann as much as blame the people who didn’t do THEIR due diligence in asking how he came up with such an outlandish claim. But he told them what they wanted to see (catastrophe on the horizon!), so they accepted it.
    *** Note that Esper was one of The Mann-Jones Team, or at least on the close periphery. That this comes from Esper sounds like the man got some principles along the way.

  43. I find it very interesting that, there is so much in dispute about present day Global Climate. We know a great deal about what’s going on, with all the advantages of modern technologies etc. Yet there is still a great deal to learn. How can we have any certainty about the past? We have good broad outlines, but not to the extent of what we know what’s going on today. For me, what is even more amazing, is the confidence expressed by some, that they are so certain what will happen in the future.

  44. I’d have thought sunlight would be more important than a few degrees temperature to improve plant growth. Perhaps it is warm but cloudy or cool but sunny.

    • Zemlik –
      Sunlight? Added to site slope, available site nutrients, competition from nearby trees, etc., of COURSE it is a factor. Which (or which combination) actually tracks with growth of tree rings? They claim to know, don’t they?
      On that line of thought, milep over at just a short time ago posted this link:
      I posted a comment about rainfall and temps myself that ties in with this, too. Several growth factors, and the dendroclimatologists assume ALL of those other than temperature are constant. It is an analog to global warmist scientists, who think that CO2 and only CO2 is underlying late-20th-century warming – the warmists MUST and DO assume all natural forcings are constant. Without such an assumption, they’ve got nothin’. WITH such an assumption, have they been digging themselves into a hole?
      I track down such thinking to the astronomers who about 100 years ago began assuming that all stars of a certain type had the same intrinsic brightness (which I thought was a terrible assumption when I first heard it and still do). Thus was born the beginnings of all the distance determinations which led to the Doppler redshift and then to the Big Bang. (Are they right? Perhaps, but such an assumption is so wrought with blind-alley-thinking possibilities that I simply cringe whenever I see it again, in any discipline. If they have gone down a blind alley, it will take a VERY long time for them to admit it and at the risk of many decades of lost progress.)

      • Well there is the expression ” blind you with science”.
        I agree I also have always had questions about what is being measured.
        having tried to imagine the construction of the Universe I can report that it is really difficult for a mind to grasp the reality of it.
        I suppose a lot of people have noticed that too.

  45. I really had to think about water being densest at 4 degrees C and that if it did not have this property life would most likely not have evolved because it would be pushed up to flap about and die on the surface of ice. And this seems to suggested that to find warming you need to measure the bottom of the oceans rather than the top.

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