Mann: Trees aren’t behaving like I want them to – volcanoes to blame

From Penn State

Tree rings may underestimate climate response to volcanic eruptions

Some climate cooling caused by past volcanic eruptions may not be evident in tree-ring reconstructions of temperature change because large enough temperature drops lead to greatly shortened or even absent growing seasons, according to climate researchers, who compared tree-ring temperature reconstructions with model simulations of past temperature changes.

“We know these tree rings capture most temperature changes quite well,” said Michael Mann, professor of meteorology and geosciences and director of the Penn State Earth System Science Center. “But the problem appears to be in their response to the intense short-term cooling that occurs following a very large volcanic eruption. Explosive volcanic eruptions place particulates called aerosols into the stratosphere, reflecting back some fraction of incoming sunlight and cooling the planet for several years following the eruption.”

Tree rings are used as proxies for climate because trees create unique rings each year that often reflect the weather conditions that influenced the growing season that year. For reconstructing climate conditions, tree-ring researchers seek trees growing at the extremes of their growth range. Inferring temperature changes required going to locations either at the tree line caused by elevation or at the boreal tree line, the northern most place where the trees will grow.

For these trees, growth is almost entirely controlled by temperature, rather than precipitation, soil nutrients or sunlight, yielding a good proxy record of surface temperature changes.

“The problem is that these trees are so close to the threshold for growth, that if the temperature drops just a couple of degrees, there is little or no growth and a loss of sensitivity to any further cooling. In extreme cases, there may be no growth ring at all,” said Mann. “If no ring was formed in a given year, that creates a further complication, introducing an error in the chronology established by counting rings back in time.”

The researchers compared temperature reconstructions from actual tree-ring data with temperature estimates from climate models driven with past volcanic eruptions.

Comparing the model-simulated temperatures to the Northern Hemisphere temperatures reconstructed from tree-ring thickness, Mann, working with Jose D. Fuentes, professor of meteorology, Penn State, and Scott Rutherford, associate professor of environmental science, Roger Williams University, found the overall level of agreement to be quite good.

However, they report in the current issue of Nature Geoscience that “there is one glaring inconsistency; the response to the three largest tropical eruptions — AD 1258/1259, 1452/1453 and the 1809+1815 double pulse of eruptions — is sharply reduced in the reconstruction.”

Following the 1258 eruption, the climate model simulations predict a drop of 3.5 degrees Fahrenheit, but the tree ring-based reconstruction shows only about a 1 degree Fahrenheit dip and the dip occurs several years too late. The other large eruptions showed the same type of discrepancy.

Using a theoretical model of tree-growth driven by the simulated temperature changes, the team determined that the cooling response recorded by the trees after a volcanic eruption was limited by biological growth effects. Any temperature drop exceeding roughly 1 degree Fahrenheit would lead to minimal tree growth and an inability of trees to record any further cooling. When growth is minimal enough, it is likely that a ring will not be detectable for that year.

The potential absence of rings in the first one to three years following eruption further degrades the temperature reconstruction. Because tree-ring information is averaged across many locations to obtain a representative estimate of northern hemisphere temperature, tree-ring records with and without missing rings for a given year are merged, leading to a smearing and reduced and delayed apparent cooling.

The researchers also noted that aerosol particles forced into the air by volcanoes block some direct sunlight causing cooling and they produce more indirect, scattered light at the surface. Trees like indirect sunlight and grow better under those conditions. However, this effect is small compared to that of lower temperatures and shorter growing seasons.

By accounting for these various effects in the tree growth model, the researchers were able to reproduce the reduced and smeared cooling seen in the actual tree-ring temperature reconstruction, including the near absence — and delay — of cooling following the massive 1258 eruption.

“Scientists look at the past response of the climate to natural factors like volcanoes to better understand how sensitive Earth’s climate might be to the human impact of increasing greenhouse gas concentrations,” said Mann. “Our findings suggest that past studies using tree-ring data to infer this sensitivity have likely underestimated it.”

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117 Responses to Mann: Trees aren’t behaving like I want them to – volcanoes to blame

  1. Goldie says:

    So I’ll say the obvious. If trees respond so well to warmth then surely…………..

  2. petermue says:

    “Our findings suggest that past studies using tree-ring data to infer this sensitivity have likely underestimated it.”

    A real euphemism to concede all tree-ring data is simply wrong from scratch.
    Of course he would never admit it this way.

  3. ibbo says:

    Love the confidence, we know that tree rings, capture ‘most’ climate changes ‘quite’ well.

    Good job were not spending billions based on this work.

    God help the bloke if he actually had to do some work based on financial systems, where things have to be 100% accurate.

    Or engineering where the term ‘quite’ well kills people.

  4. James Allison says:

    Well waddaya know The Mann may have some competition. According to some academics down my way tree rings are also pretty clever at predicting Nini events. Shame about cutting down the Kauri forests.

    http://www.stuff.co.nz/national/6370049/Forest-giants-forecast-trouble-ahead

  5. Kurt in Switzerland says:

    Does this mean that Prof. Mann will issue a new version of his hockey stick? Will the new one look like a downhill ski racer’s poles? Or perhaps an “accordion gate”?

    Will it acknowledge the MWP & LIA? (and perhaps address that pesky bit of data post 1950, which showed a decline – requiring him to graft on temperature sensor data).

    Not holding my breath…

    Kurt in Switzerland

  6. Brian H says:

    Next, he’ll discover rainfall affects tree growth. Wait for it!

  7. Christopher Hanley says:

    “We know these tree rings capture most temperature changes quite well,” said Michael Mann….

    How can Mann and his colleagues know that?
    The infamous ‘hidden decline’ repudiates that statement http://www.climate-skeptic.com/wp-content/uploads/2009/11/briffa_recon.gif.

  8. Robinson says:

    “We know these tree rings capture most temperature changes quite well”

    They do?

  9. Markus Fitzhenry. says:

    Volcanos don’t cool Earth, at least not whilst the energy evacuated, remains in Atmosphere. Eventual, if any, upper atmosphere disturbances would pass more Atmospheric mass to space, on a timescale unknown to me.

    The enhancement of the potentiality of additional Atmospheric mass would warm in the near term, not cool. I don’t think volcano eruptions cause climate disturbances under a paradigm of greenhouse, I think the climatic result of volcano eruptions would be more like the Ned Nikolov & Karl Zeller, ATE principle.

    The following is the thorey of DavidmHoffer when prehistoric Earth suffered a meteor shower and eventual loss of Atmospheric mass, with catastrophic results for biodiversity in a world with a dramatic loss of force of pressure (density).

    The earth loses atmosphere to space as an on going process. The ultimate fate of the earth, millions of years from now, is to be a barren rock, just like the moon. What if we postulate, instead of a few large meteors, many small ones?
    Many small meteors would leave no mark on earth surface because they would burn up before getting there. But throw enough of them at the atmosphere at once, over a period of years or even decades, and that is one hot upper and perturbed upper atmosphere with loss of atmospheric mass (I would think) to space heavily accelerated. Consider the chain of events that would follow:

    o No more flying creatures. Not just Pterodactyls, but anything, even insects, that had evolved the ability to fly based on a denser atmosphere. All gone in short order.
    o Predators dependent upon those species…gone.
    o Plants dependent upon those species for pollination…gone.
    o Plants dependent upon those species to control pests that would otherwise run rampant… gone.

    But here is the doozy. We know that plants thrive in conditions of much higher CO2 than we have today, that’s why greenhouse operators pump it into their greenhouses raising levels to many times “normal”. The plants respond with better growth and need less water and humidity to remain healthy, suggesting they evolved at a time when CO2 levels were much higher than they are now. And, based on the faint sun hypothesis…when PRESSURE was also much higher than it is now. We haven’t tested plant growth at elevated pressures to my knowledge, but it makes sense that in reduced pressure, the ability of plants to capture CO2 from the atmosphere would also be reduced, and likely other effects would occur as well.
    o The entire plant kingdom that had evolved to a given atmospheric pressure range, would have also died. Let’s keep going!
    o A sudden drop in pressure would in turn result in a sudden drop in temperature. The temperate zones would have retreated, and retreated big time, from the poles toward the tropics, triggering… if not a full blown ice age, then something like the Little Ice Age. Mass extinctions world wide even in the tropics where temperatures would have held steady. And that would be followed by….
    An earth steadily increasing in temperature commensurate with the steadily increasing insolation of the Sun for thousands of years.
    Exactly as the geological record since the last ice age shows.
    If one ties N&Z to Stephen Wilde to Faint Sun to Extinction Event….an awful lot of things start falling into place.

  10. I think he’s just making it up as he goes along!

  11. Bertram Felden says:

    “We know these tree rings capture most temperature changes quite well,”

    Erm, no they don’t.

  12. I recently wrote an article whereby I looked in detail at the methods of temperature reconstruction used by Dr Mann and Hubert Lamb when carrying out my own reconstruction of CET back to 1538

    http://judithcurry.com/2011/12/01/the-long-slow-thaw/

    It is very difficult to see how and why this myth surrounding the accuracy of tree rings has come about. As an approximate measure of precipitation they may be ok, but they are certainly no sort of reliable indicator of temperatures to fractions of a degree. It is disappointing that bona fide climate sciemtits do not point out the limited worth of tree rings and similar proxies.
    tonyb

  13. Juergen says:

    Trees don’t grow in the winter. Look out the window and you can see how inactive they are.
    This means they don’t record anything in the tree rings about the winter time.
    What’s about the night time? I read that the trees are partially shut down (asleep)..

    Q: What do tree rings really record and what not?

  14. Gary Mount says:

    Poor Mr Mann, his specialty becomes ever more obsolete as more high quality satellite data streams in by the day. A third of a century of data now. Since I started my climate research 2 years ago, the length of time of this high quality unbiased data has grown by 6 percent. The climate sensitivity question will be answered not with tree rings, but by the work of the likes of Dr. Roy Spencer.

  15. Phillip Bratby says:

    I don’t seen any signs that an expert statistician has been involved in the paper. I wonder why not.

  16. sunderland steve says:

    “We know these tree rings capture most temperature changes quite well,” said Michael Mann,

    Yeah, apart from those that occur outside the growing season and those that are masked/enhanced/suppressed by variation in precipitation.
    Face it Michael, tree rings are useless for temperature reconstructions.

  17. RB says:

    “quite well”.

    Well thats me convinced. Where do I send my taxes?

  18. Markus Fitzhenry. says:

    Every tree is different, as we are.

    They took a miniscule sample, averaged it and expected it to apply it to a universal theory.

    Deluded.

  19. brokenhockeystick says:

    So, what he’s saying is that tree rings are great for indicating when its bright and warm but they can’t show when its dull and cold. In-built warming bias, maybe…?

  20. Doug UK says:

    “We know these tree rings capture most temperature changes quite well,” said Michael Mann,

    “They do – honestly! – believe me!! – I speak from a position of authority”

    I suspect history will ponder the likes of Mann’s hubris for quite some while

  21. Ade says:

    Manns temperature model has gone COLD

  22. Let me paraphrase this

    … the big problem for trees is when there is too much cold.

    Which is exactly the same for humans:-

    1. 23,000 people die in the UK from cold … they don’t have records for heat because the hot weather prevents deaths.
    2. In the 1690s some estimates suggestion a quarter of the Scottish population died from the cold.
    3. Humans inhabit the planet from the equator to a point north/south … i.e. diminishing rapidly toward the poles. In other words, the amount of the world we humans populate is limited not by heat but by cold.
    4. Many uplands in Britain are “fossilised” human landscapes of bronze age inhabitation from a time when it was warmer. There is zero evidence any part of Britain was too warm!!!

    And Mann has the gall to call warming a problem!

  23. AndyG55 says:

    “who compared tree-ring temperature reconstructions with model simulations of past temperature changes.”

    roflmao !!

  24. Christopher Hanley says:

    “We know these tree rings capture most temperature changes quite well,” said Michael Mann….
    “The infamous ‘hidden decline’ repudiates that statement..”….I should have added: or does it?

  25. Dave Wendt says:

    I’ve got a question that I don’t have time to run down myself at the moment,but I’m hoping someone here might have the answer for. Has anyone ever done an analysis of how well weather stations at the treeline in mountains and at the boreal forest margin correlate with GAT in the instrumental era?

  26. Jimmy Haigh. says:

    Charles Gerard Nelson says:
    February 6, 2012 at 12:49 am
    “I think he’s just making it up as he goes along!”

    I agree – that’s exactly what I thought.

  27. Dermot O'Logical says:

    “For these trees, growth is almost entirely controlled by temperature, rather than precipitation, soil nutrients or sunlight”
    I just can’t believe this can be true. Can a tree really grow at the same rate, regardless of the availability of water, nutrients and photosynthesis? That sounds, well, miraculous.

  28. Kev-in-Uk says:

    Agree with the comments regarding negative ability of tree rings as temperature proxies – but, and it is a big but – they are still useful as comparison sources for other palaeoclimate reconstructions. All temperature proxies are suspect, IMHO – but if you get a few that ‘agree’ and show some consistency, you at least can draw the conclusion that some ‘change’ happened. What really peaces me off is the way proxies are then compared to current measurements/trends and supposedly ‘realistic’ past temperatures are deduced (a la hockey stick). The day I see a proxy dataset being described correctly as ‘purely indicative only’ – instead of being touted as some form of real quantitative data, (especially by believers!) is the day I’ll start to take the palaeo-climate work more seriously!

  29. Disko Troop says:

    Mann. “Our findings suggest that past studies using tree-ring data to infer this sensitivity have likely underestimated it.”

    Dare I say it…..”It’s worse than we thought!”

  30. papiertigre says:

    http://wattsupwiththat.com/2008/06/13/surprise-leaves-maintain-temperature-new-findings-may-put-dendroclimatology-as-metric-of-past-temperature-into-question/

    Surprise: Leaves Maintain Temperature, new findings may put dendroclimatology as metric of past temperature into question

    A new study that shows their internal temperature remains constant at 21.4deg could challenge the way trees are used to determine historical climate data
    The internal temperature of leaves, whether in the tropics or a cold-clime forest, tends toward a nearly constant 21.4 degrees Celsius, reports a study released today.
    It had long been assumed that actively photosynthesising leaves – using energy from sunlight to convert carbon dioxide and water into sugar – are nearly as cold or hot as the air around them.
    The new findings not only challenge long-held precepts in plant biology, but could upend climate models that use tree rings to infer or pre… .

    Game over.

  31. H.R. says:

    “I talk to the trees…. but they don’t listen to me.”
    (From Paint Your Wagon)

  32. Brian H says:

    JA;
    “Nini”, huh? Generic for Ninas and Ninos. Nice! “Los Nini” with the article?

  33. Gary Hladik says:

    “Using a theoretical model of tree-growth driven by the simulated temperature changes, the team determined that the cooling response recorded by the trees after a volcanic eruption was limited by biological growth effects.”

    Whoa! The simulated trees now agree with the simulated climate! Who’da thunk it? I think these guys should be rewarded with some simulated research grants!

  34. RobB says:

    Robinson says: February 6, 2012 at 12:45 am
    “We know these tree rings capture most temperature changes quite well”
    They do?

    From the 1997 paper “Tree rings are really not that bad, actually OK at times on occasion, as temperature proxies”

  35. paul in surrey says:

    well you know what they say, its not the thing thats wrong, its our perception of what it should be doing thats wrong, there’s a name for that

  36. thingadonta says:

    Doesnt say anything yet about tree rings and warm temperatures. oh well, we’ll wait another 15 years. Then it will be:

    “The problem is when solar activity and temperature increases beyond a certain point, this is not reflected in the tree rings, as they reach a maximum growth state determined by internal growth factors… etc etc”.

    Yes Mr Mann, a hockey stick, that then declines. A 7 year old could understand it.

  37. ScuzzaMan says:

    We know that new evidence, which shows our previous estimates to be even less reliable than we optimistically assumed, proves that our previous estimates are correct.

    Yeah, whatever you say, Mike.

  38. JohnH says:

    I am always amused when the word Skilful is used by Mann to describe his false machinations of proxy data. He has some front.

  39. Old England says:

    Did I miss any mention that CO2 levels have a very significant effect on rates of growth? Does Mann understand that – or is it ‘coveniently’ ignored? I wonder if tree ring data had any adjustments made to take account of the prevailing CO2 levels – let alone precipitation ?

    Unless I misunderstand it plant growth is greater, even at lower temperatures, in higher concentrations of CO2. I’m not sure that there is research detailing the growth characteristics of appropriate tree species plotted against temperature and against CO2 levels. Without an accurate understanding of that then using tree ring data to try and calculate temperature is a non-starter as it can never be correct – it would simply be valueless guess-timation. Although having said that Mann seems to be unconcerned about the inescapable innacuracy.

    I don’t have access to the data but if a 50% increase in CO2 levels creates a 10% increase in tree growth then, without adjusting for the CO2 level, might it suggest a 5% or 10 % (??) higher temperature? To make that CO2-related growth adjustment the species sensitivity to CO2 levels (at given temperatures) would need to be accurately known – but having reached that point the next variable (again an unknown) of precipitation levels which also affect growth comes into play ………

    None of which seems to concern Mann – or am I mistaken ?

  40. Allan MacRae says:

    Please note my questions 3, 4 and 5 below, especially number 5.

    Apparently this week’s answer is 5c) Volcanos !!!

    “You could not make this stuff up.”

    Oh wait! I just did! On Saturday morning!

    Inside the mind of Mann… (queue music from Twilight Zone, Rod Serling speaks: “Hubris…”)

    http://wattsupwiththat.com/2012/02/04/editorial-in-support-of-dr-michael-mann-and-open-debate/#more-55949

    Of course – let the Mann speak! But do not expect a fair or open debate.

    Some suggestions for question period:

    1. Do you believe that the Uniformitarian Principle has been especially exempted for your particular brand of global warming science? Why?

    2. Do you assume that Occam’s Razor can safely be ignored, just for advocates of dangerous humanmade global warming? Why?

    3. Please explain the “Divergence Problem” and “Hide the Decline”.

    4. Not one of your scary global warming predictions has materialized. You have demonstrated negative predictive skill. Do you see any problem with your predictive record?

    5. What is this week’s explanation for the observed flat or cooling global temperatures in this century? Is it aerosols, dust, volcanoes. the appalling scarcity of buffalo farts, or other?

    6. What journal editor are you trying to intimidate this week?

    7. What climate realist are you trying to have fired from his university position this week?

    8. Will you participate in a fair and open debate, this week, or any other?

    ************************

  41. DEEBEE says:

    So they were right to hide the decline.
    Since the models do a bang up job predicting the future without volcanoes and China, they should do a bang up job estimating a portion of the anomaly. We can subtract this wonderful estimate and draw even more magical conclusions from the residue.
    Is this not amazing that all these magical calculation always turn out one way.

  42. wayne Job says:

    I would believe that the last time the words needed to explain this character were uttered by Audrey Hepburn. Those words were an addlepated ninconpoop seems appropriate.

  43. berniel says:

    Why does this puff-piece bring to mind the great Polish historian of Marxism, Leszek Kolakowski, who, after defecting and abandoning Stalinist Eastern Marxism, said of the neo-Marxism of the 1960s West: ‘There are better arguments in favour of democracy and freedom than the fact that Marx is not quite so hostile to them as he first appears.’ ?
    Perhaps it is that there have always been better ways to proxy past global temperatures than by tree-rings. The limitations of using tree rings to proxy temperature have always been known to outsider (to those that invented it!), and so to persist with dendrology when its failure becomes unavoidably apparent — to only use other measures to correct it — seems to exhibit a touch of the obsessiveness of those clinging desperately to a fag-end of a fading ideological dogmatism.

  44. Markus Fitzhenry. says:

    “”For these trees, growth is almost entirely controlled by temperature, rather than precipitation, soil nutrients or sunlight””

    What barometer was available to assume the biological influx of Co2 and other nutrients. Was there an allowance for Atmospheric pressure levels at tree growth? What credence was given to air density in his paleontological proxies?

    Climate Science, the art of seeing what is not there.

  45. Khwarizmi says:

    We all know that tree growth rates make an excellent thermometer.
    And I would have gotten away with it too–if it wasn’t for those meddling volcanoes! (1)

    1. peer-reviewed

  46. Tony Mach says:

    What, wait treemometers are not perfect thermometers? What a stunning revelation. So to recap, treemometers are perfect thermometers when it suits Mann, and then he disowns them when it is in the interest of “The Cause”™©. Gee, thanks Dr. Mann, for this valuable post-hoc rationalization!

    And I wonder, if these treemometers fail to record a rapid drop in temperature, maybe they can equally fail a rapid drop in water supply (e.g. when a rapid increase in temperature occurs). Just a thought, Dr. Mann.

  47. Claude Harvey says:

    I’m confused. Is Mann talking about “regular trees” or “temperature trees”? We know from his previous work that not all trees are “temperature trees”. It takes a highly trained expert like Mann to tell us which trees are telling the truth about temperature and which of their neighbors are lying like rugs in the forest. It’s an ART!

  48. SandyInDerby says:

    “We know these tree rings capture most temperature changes quite well”

    I wouldn’t buy a car that:- “Gets round most corners quite well”
    I don’t buy this as a reason to buy into his theories either.

  49. Mark says:

    “Tree rings are used as proxies for climate because trees create unique rings each year that often reflect the weather…”

    Erm, weather or climate?

  50. richard verney says:

    I cannot believe that this man is this stupid.

    Trees are proxies for then prevailing growing conditions. Based upon our present understanding and problems with noise and resolution issues, it is not possible to separate out, on an individual basis, ring response to each individual factor that may influence the then prevailing growing conditions. Trees are a poor proxy for global temperatures not least because of their spatial distribution and the fact that oceans, arid desert and arctic/antarctic areas account for more than 80% of the area of the globe. Trees can at best provide an insight into conditions representing no more than 20% of the globe.

    He claims that “We know these tree rings capture most temperature changes quite well,” and yet we know that that is not the case as is conclusively proved by:

    (i) the infamous divergence problem (ie., the divergence in response post 1960 to temperature data); AND
    (ii) the fact that they failed to capture the LIA (a well documented event that we know occurred); AND
    (iii) the fact that they failed to capture the MWP (another well documented event that we know occurred).

    In fact, it appears from the Climategate emails that tree ring response was tuned to data extracted from the instrument record for the period 1906 to about 1950. This begs the question, why were they not tuned to the entire instrument record. In particular why not include:

    (i) the data 1850 to 1905? Presumably because the desired result was not obtained!; and/or
    (ii) the data post 1950s through to the date of the study? Again, presumably because the desired result was not obtained!

    In practice tree proxies should be scrapped until they can properly deal with and explain the divergence problem. At this stage, all efforts should be limited to collecting tree data for the period 1950 to 2011 and examining this in relation to the instrument record for the period. There are some volcano eruptions in this time frame and therefore the response to volcanoes will be seen.

    Once tree rings can be tuned to the period 1950 to 2011 and from that tuning an accurate year on year (or at least semi decadal) plot back to 1850 can be reproduced there can be no confidence that tree rings are good for anything to do with temperature extraction. If when further extrapolated back in time they fail to show the LIA or the MWP something is still amiss and further study needs to be conducted or an acceptance that based upon present techniques and understanding tree rings are not a good proxy for temperature.

    A life time of work needs to be consigned to the bin; it is back to the drawing board on this one, sorry mate but that is the only way forward.

  51. richard verney says:

    I am not an expert on trees but agree with others that tree ring growth is in general more determined by precipitation rather than anything else. Growth can also be stunted by extreme cold.

    Here in Spain, in my garden, I have a number of orange trees. All are of broadly similar age and yet they have grown very differently. Some are a few metres apart (therefore getting the same sun, rain, temperature and soil nutrients) and yet perhaps only 20 to25% as large as the best growing trees! WUWT?

    My back garden is open to the mountain side covered by 100s of pine trees. No two trees appear obviously the same and yet many must have rooted at the same time and they are all experiencing broadly similar growing conditions and yet their height and width and branching and canopy distribution is quite variable.

    I suspect that trees are over rated as a proxy for anything. Some broad extrapolation may be possible, but fine resolution I suspect is very difficult.

  52. David L says:

    So Mann, with all his simulated theoretical models, has proven that trees grow better in warmth. Isn’t this the same guy the loves glaciers and laments a warm globe?

  53. Speed says:

    As Willis says, “It’s models all the way down.”

  54. KNR says:

    “We know these tree rings capture most temperature changes quite well,”
    In reality Manns show that his ‘no expert’ in tree growth as well as statistics , while the hide the decline tells us how stupid this claim really is . There are people who are experts in tree growth , that is they spend years working and studying in this area , and they would laugh at Mann’s ideas . But I guess they don’t count as their not ‘climate scientists’

  55. Joe Bastardi says:

    I can not believe some of the tweets coming out of him.. He retweeted Heide Cullens nonsense about a pissed off planet causing Volcanoes and Irene, and now has tweeted its journalistic malpractice not to report the non US winter as a climate change indicator, when the global temp has plummeted and is over -.18C for the year so far.

    I always wanted to give him the benefit of the doubt, but he is going the way of Hansen, pure and simple

  56. “…Following the 1258 eruption, the climate model simulations predict a drop of 3.5 degrees Fahrenheit, but the tree ring-based reconstruction shows only about a 1 degree Fahrenheit dip and the dip occurs several years too late. The other large eruptions showed the same type of discrepancy…”

    With this statement, he shows that either the climate model simulation is wrong, or his tree ring-based reconstruction is wrong. Either the first simulation is too high, or the other simulation is too low.

    “…Using a theoretical model of tree-growth driven by the simulated temperature changes, the team determined that the cooling response recorded by the trees after a volcanic eruption was limited by biological growth effects. Any temperature drop exceeding roughly 1 degree Fahrenheit would lead to minimal tree growth and an inability of trees to record any further cooling. When growth is minimal enough, it is likely that a ring will not be detectable for that year…”

    So where are the peer-reviewed papers showing that his selected trees (or any trees) can have no rings for a drop of 1 degree F? And, then, according to his latest – since we’ve seen a rise of about 1 degree F since the start of the industrial revolution, does that mean there was no tree growth before then?

    “…theoretical model of tree-growth driven by the simulated temperature changes…”

    This study isn’t being done to see how actual trees respond to actual biological changes. It’s being done to try and salvage the “today is the warmest it’s been in a million years” papers.

  57. George says:

    “Following the 1258 eruption, the climate model simulations predict a drop of 3.5 degrees Fahrenheit, but the tree ring-based reconstruction shows only about a 1 degree Fahrenheit dip and the dip occurs several years too late. The other large eruptions showed the same type of discrepancy.”

    Just wow. In other words, the model has no prediction power and does not tie into the data. Invalid model. And the model then actual refutes their own hypothesis.

  58. David L. says:

    “If no ring was formed in a given year, that creates a further complication, introducing an error in the chronology established by counting rings back in time.”

    It creates a counting error of one year. This is a major complication?

    Why a missing ring causes such issues for Mr. Mann is puzzling. Real dendrochronologists know how to deal with missing tree rings. They do happen occasionally along with other phenomena such as double rings in a year.

  59. You ALL are invited to a free special seminar by

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    2pm-4pm 22nd February 2012
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    (Ask for Sammy Wilson MP’s meeting
    and allow 30 minutes for security)

    Special guest speaker
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    Program in Atmospheres, Oceans, and Climate
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  60. David L. says:

    Claude Harvey says:
    February 6, 2012 at 3:28 am
    I’m confused. Is Mann talking about “regular trees” or “temperature trees”? We know from his previous work that not all trees are “temperature trees”. It takes a highly trained expert like Mann to tell us which trees are telling the truth about temperature and which of their neighbors are lying like rugs in the forest. It’s an ART!
    ……………………………………..
    I used to own an old log cabin in Central PA, built sometime around 1800. I wanted to pinpoint the year exactly so I measured the rings of the logs with an accurate optical reticule to create a tree ring series. I also measured the rings of freshly felled trees (same species of pine) on my property and a few others down the valley. I also got some official tree ring data for the region going back about 500 years. Performing cross correlations between all samples, I couldn’t get any tree to agree with any other tree to within a correlation coefficient of about 0.6 with an uncertainty in lag for about +/- 30 years.

    It’s hard to get two neighboring trees to show great correlation in their ring width series. As one tree grows faster than the other it starts to rob it of sunlight, nutrients, etc. I can even see that in my own back yard from saplings I’ve planted. Mann’s worry about missing a year in the series is the least of his problems. The absolute least.

  61. kcom says:

    But I guess they don’t count as they’re not ‘climate scientists’

    But they are the cardiologists of trees. And yet, Mann doesn’t want to listen to them. He wants to claim expertise in their area, as all areas, for himself. Was he part of that letter in the WSJ? What hubris!

  62. Blade says:

    Mann: Trees aren’t behaving like I want them to

    HeHe, I just saw this at Tom’s Hardware This Record Player Turns Trees Into Music

    “Designed by German artist Bartholomäus Traubeck, this one of a kind record player revolutionizes the classic vinyl playing turntable. By using circular cross-sections of trees rather than vinyl records, the “Years” player gives us an idea of what music would sound like if mother nature was a composer. As one might expect from a chopped down tree, the music is fairly dark and ominous.”

    This is undoubtedly a better use of the wood than letting Mann continually vindicate the Peter Principle.

    http://vimeo.com/30501143

  63. Mark T says:

    At some point you just have to acknowledge the plain truth that this guy’s PhD was a gift. There’s a reason he dropped out of the physics program. Unbelievable.

    Mark

  64. Doug Cotton says:

    richard verney says:
    February 6, 2012 at 3:47 am
    I cannot believe that this man is this stupid.
    _____________________________

    I can.

    We have his hockey stick, now developing a bent handle from too much misuse.

    And we have him and his colleagues treating the Earth’s surface as if it is a blackbody totally insulated from the atmosphere and emitting all the radiation observed from space, so, when we make such stupid assumptions we can derive a very sensible (?) statement showing the surface would have been -18 deg.C but for carbon dioxide and its colleagues.

    But then we realise we had better put back the conduction, convection, evaporation etc into the energy diagrams, plus all the radiation from the atmosphere, so it all looks about right. Hopefully the public will be even stupider and forget that we left it out to calculate the -18 deg.C. Yes, I think we can count on climatologists forgetting that so they will peer-review the new energy diagrams and yet still remember that -18 deg.C figure which they will now teach to all their up-and-coming climatologists – so the the public will indeed be even stupider, and anyone who denies all this (because he/she sees how stupid it is) will be even stupiderer.

  65. A Lovell says:

    It would seem Mann is on the back foot. He appears still to be trying to justify his hockey stick. At least if he continues to bang on about ‘treemometers’ he may not be up to too much mischief elsewhere. The desperation is palpable.

    I believe dendrochronology has been found useful for dating stuff.

  66. Philip Peake says:

    I think people are missing the point here. It appears that tree rings under estimate cold, which means they need to apply cooling corrections to past temperature data thus exposing the fact that temperature rise is much worse than we thought!

  67. Taphonomic says:

    “there is one glaring inconsistency; the response to the three largest tropical eruptions — AD 1258/1259, 1452/1453 and the 1809+1815 double pulse of eruptions — is sharply reduced in the reconstruction.”

    He has just disproved his own hypothesis and is too entrenched to realize it. Start doing science, Mike.

  68. More Soylent Green! says:

    I think the answer to the problem is right there in the article. Clearly, instead of using actual tree ring measurements, Mann needs to use his theoretical model of tree ring grow. Just plug in the data for temps and precip. If that doesn’t get the results, use a model to get the temp and precip data.

  69. brokenhockeystick says:

    Aren’t we in danger of misssing a trick here? In the interests of holding out an olive branch, should we not be congratulating Mr Mann for finally admitting to the world the Hockey Stick chart is a crock of sh!te?

  70. PhilJourdan says:

    @H.R. says: on February 6, 2012 at 2:01 am

    I see I am not the only fan of that movie. ;)

  71. trbixler says:

    While it is obvious that Mann’s science is weak or non existent his “cause” still controls government action.

  72. Shevva says:

    Don’t worry MM y0u will be going down in history as a scientist, it just may not be a scientist anyone would want to follow in the foot steps of.

    Phil Jones (Whos he?) will thank you though as he probably will not be remembered.

  73. TomT says:

    “model simulations of past temperature changes.” Well if tree rings don’t match the model, change the model. Oh what if tree rings don’t capture most temperature changes quite well? Then we will select one tree that matches the models fairly well and use that one tree for a proxy of global temperature, until we have to hide a decline.

  74. D.J. McGuire says:

    OK, maybe it’s just me, but doesn’t this actually make the hockey stick even *more* unrealistic?
    Mann is saying the old, pre-volcano-adjustment, tree-ring data was too *high* for temperatures, but wasn’t “Mike’s Nature Trick” designed to camouflage the fact that the post-1950 tree-ring data was too *low*? If I read this right, this adjustment will make the tree-ring data *lower*, and thus *exacerbate* his problem.
    Am I missing something? Was there a tent in this tree-ring circus that I haven’t seen?

  75. Louis Hooffstetter says:

    “Some climate cooling… may not be evident in tree-ring reconstructions of temperature change… (when) tree-ring temperature reconstructions (are compared) with model simulations of past temperature changes.”

    Translation: “When data doesn’t match our model simulations, we conclude our model is right and the data is wrong.”

    or as Mythbuster Adam Savage says: “I reject your reality and substitute my own.”

    Only in ‘Climastrology’ get you away with this B.S. The scientific community should laugh them off of the stage!

  76. Theo Goodwin says:

    Tears of Joy rolled down my face as I read the comments on Mann. I do not need to say a thing. Bravo/Brava, commenters!!!!

    Unfortunately, I cannot resist saying something. Mann has been forced to recognize that there is a real world, that trees live in the real world, and that investigation of the facts on the ground are necessary for claims that some set of trees can be used as proxies for temperature. It must have hurt him deeply to accept those facts. He does his best to spin them.

    Mann’s recognition of the importance of these facts should have come before he was granted a Phd. The recognition should have come before publication of any version of his Hockey Stick. Responsible people failed in their duties.

    Now that Mann has been forced to take account of the facts on the ground, his work on temperature proxies must surely fall apart. That “falling apart” will be evident in his own work as it is evident in each paragraph quoted above.

    If you get a chance, make sure that your Congressional representative knows that Mann’s work on temperature proxies is about to disappear like a puff of smoke.

  77. John West says:

    “The researchers also noted that aerosol particles forced into the air by volcanoes block some direct sunlight causing cooling and they produce more indirect, scattered light at the surface. Trees like indirect sunlight and grow better under those conditions. However, this effect is small compared to that of lower temperatures and shorter growing seasons.”

    So what! Anthropogenic CO2 emissions are small compared to natural emissions and yet they dominate the global heat budget, throwing the entire global climate into chaos whereas before man’s interference with the carbon cycle there was perfect balance and stability, global paradise. /sarc

    Seriously though, that may very well explain the “lag” they see in response. The temperature decrease is initially offset by the efficiency increase. But, of course, that would mean temperature isn’t the dominant factor in tree ring growth and we all know that just can’t be true. [Oops, how did that sarcasm tag come back? I better turn it off again.] /sarc

    “The lack of a larger cooling in proxy records of climate change following large volcanic eruptions such as those of Tambora in 1815 and Krakatau in 1883 has long been a puzzle for climatologists. These records, however, may have been biased by enhanced tree growth for several years following each eruption induced by additional diffuse radiation caused by the stratospheric volcanic aerosol clouds from the eruptions.
    http://climate.envsci.rutgers.edu/pdf/TreeRingCorrection3.pdf

  78. David Ball says:

    The trees are part of the fossil fuel conspiracy. Only possible explanation, …..

  79. Peter Miller says:

    Tree rings are a good proxy for:

    1. Temperature.
    2. Rainfall,
    3. Tree density,
    4. Forest fires,
    5. Volcanoes,
    6. Forest fires – fertiliser effect,
    7. Lightning – fertiliser effect and partial tree destruction,
    8. Wild animal and bird populations – fertiliser effect,
    9. Carbon dioxide concentration – fertiliser effect,
    10. Exposure to wind, and
    11. Mannian maths to distort.

  80. Mikesixes says:

    Assume you are a budding climatologist, and you are confronted with a situation in which measured data conflicts with a model output. Do you think-
    a-the model is wrong
    b-you have misinterpreted the measured data
    c-the natural process which produced the measured data has somehow malfunctioned

    If you chose c, congrats! You are a climate scientist.

  81. NoAstronomer says:

    “Inferring temperature changes required going to locations either at the tree line caused by elevation or at the boreal tree line, the northern most place where the trees will grow. For these trees, growth is almost entirely controlled by temperature”

    And the research proving this can be found where exactly?

    Mike.

  82. YukonJack says:

    Juergen says:
    February 6, 2012 at 1:07 am

    Trees don’t grow in the winter. Look out the window and you can see how inactive they are.
    This means they don’t record anything in the tree rings about the winter time.
    What’s about the night time? I read that the trees are partially shut down (asleep)..

    Q: What do tree rings really record and what not?

    Trees do not grow in the winter as you point out, so they record nothing about winter conditions. At night, the trees respire, they use O2 and give off CO2 to stay alive just like we do. I have never tried to wake one up, so I don’t know whether they sleep or not. ;^)

    What do tree rings record?
    1. they record temperature during the growing season, but too hot can be the same as too cold in terms of growth.
    2. they record the amount of available water, so rainfall may be inferred.
    3. they record the amount of available nutrients like Nitrogen

    Basically, they record whether the tree was growing normally (enough warmth, wet, and food) or whether it was stressed (too cold, too hot, too wet, too dry, or starving for nutrients)

    What they do not record directly is temperature, that has to inferred and would require a knowledge of the other parameters as well.

  83. Steve Keohane says:

    Hey Mikey, when you can explain why the temperature vs. ring width stopped correlating in the 1960s, and get an empirical grasp of what you write about, I might read something you write again. You may also want to brush up on history so you have some comprehension of perspective on actual climate we have dealt with and recorded as humans. With these in your ruck sack you might wander in from far left field.

  84. RockyRoad says:

    “…most temperature changes”…? “MOST”…?? “MOST“???

    What happens to the rest, Michael?

    Epic Fail, folks!

  85. Steve M. from TN says:

    “If no ring was formed in a given year, that creates a further complication, introducing an error in the chronology established by counting rings back in time.”

    If there’s a missing ring, how do you know there’s a missing ring? Oh, because it doesn’t match the climate model! So we make a tree ring model, and tweak it to match the climate model..and bingo..it all agrees!

  86. Theo Goodwin says:

    Mikesixes says:
    February 6, 2012 at 8:26 am

    Bwaaaaahahaha…!!!! Made my day.

    Steve M. from TN says:
    February 6, 2012 at 9:12 am

    Receives honorable mention on same funniness scale. Is there a marker where the tree ring is missing?

  87. RACookPE1978 says:

    Old England says:
    February 6, 2012 at 2:32 am

    Did I miss any mention that CO2 levels have a very significant effect on rates of growth? Does Mann understand that – or is it ‘conveniently’ ignored? I wonder if tree ring data had any adjustments made to take account of the prevailing CO2 levels – let alone precipitation ?

    Unless I misunderstand it plant growth is greater, even at lower temperatures, in higher concentrations of CO2. I’m not sure that there is research detailing the growth characteristics of appropriate tree species plotted against temperature and against CO2 levels. Without an accurate understanding of that then using tree ring data to try and calculate temperature is a non-starter as it can never be correct – it would simply be valueless guess-timation. Although having said that Mann seems to be unconcerned about the inescapable inaccuracy.

    I can – to a little degree – agree with Mann that CO2 levels should not have been a factor in his dendro-assumed temperature records. But ONLY across the early years of tree growth, the years prior to the 1950′s and 1960′s, when we know mannkind at last began emitting significant levels of CO2 into the atmosphere. Prior to that point in the 1960′s, we are told CO2 levels were steady. Note that actual CO2 measurements varied all over the place!

    (Note, strategically) that Mann’s variations from the paleo temperature proxies and the tree-growth thicknesses also began to deviate as soon as his assumptions about CO2 levels and steady-state tree ring growth began to deviate!)

    Therefore, after reading everybody’s comments above, we have – at a minmum! – the following tree-growth-to-worldwide-climate-to-temperature-reconstruction-due-to-volcanoes errors and omissions:

    1) Any volcanoes erupting between fall through winter through early spring (with respect to the “winter” of the limited sites he chose to investigate!) will NOT be reflected in tree ring changes.

    2) Volcanoes erupting will – at most! – only affect 1 to 2 years of ring growth. From the weather-is-not-climate part of climate reconstructions?

    3) CO2 levels greatly increase today’s growth rate by 12 to 27 percent (based on Idso’s measurements of worldwide plant responses) particularly for resource-restrained plants in marginal areas. Which is what Mann prefers to study.

    4) Tree rings may not appear when growth is restrained by extreme cold.

    5) Only valid data that fits the pre-assumed model data of climate is acceptable to Mann.

    Any that I’ve missed?

    Now, who pal-reviewed this “paper” and how much did his/her universtiy receive in Man-made gifts (er, grants) from the taxpayers?

  88. Nic says:

    For these trees, growth is almost entirely controlled by temperature, rather than precipitation, soil nutrients or sunlight, yielding a good proxy record of surface temperature changes.

    No, tree growth is not almost entirely controlled by temperature. Precipitation, Soil, Sun are more important.

  89. Gary Pearse says:

    With the trees underestimating temp effects, I can see where we are going to get another paper with the re-taped hockey stick that can now magnanimously show the MWP and the LIA but these dwarfed by the “underestimated” temp rise of the last half century. Watch for it and remember this prediction. It should be out in about 6 months to a year (they are already working on it and, of course, they don’t have to wait long for peer review.

  90. TXRed says:

    I would like to know the source of Dr. Mann’s temp-controlled trees so I can purchase a few. The drought out here seems set to continue for at least another year and the temperature has been warmer than the (recently-reset) 30 year average. Trees that are not precipitation-dependent and that thrive with higher heat would be exactly what I need!

    Oh, they cut down the last ones to use in tree-ring measurements? Darn.

  91. mwhite says:

    “Following the 1258 eruption, the climate model simulations predict a drop of 3.5 degrees Fahrenheit, but the tree ring-based reconstruction shows only about a 1 degree Fahrenheit dip and the dip occurs several years too late. The other large eruptions showed the same type of discrepancy.”

    Whatever your views on using tree rings as temperature proxies just reading the paragraph above it seems that the virtual world has more validity than data from the real world.

  92. G. Karst says:

    “We know these tree rings capture most temperature changes quite well,” said Michael Mann,…”

    Does anyone know who the “we” is in the above statement. Does it refer to the other members of the “team”. Or does it just refer to M. Mann and his mistress. Many would like to know. GK

  93. Gene L. says:

    Am I following this correctly?

    A) The *new* suggestion is that tree ring analysis isn’t set in stone after all, that there are things that it doesn’t do well? … AND …

    B) They compared the actual data collected against the results of models, indicating (again) that the models are the best evidence they have?

    You have got to be kidding me…

  94. Gene L. says:

    Actually, I have another question:

    How is it that dendrochronology, using trees at the limits of their growth range (either boreal zones or at the upper edge of altitude) can be used to reflect GLOBAL conditions?

  95. Resourceguy says:

    Using FDA standards of efficacy for new drugs, these tree ring experts aka published paper mill workers for hire would be laughed at and not invited in the building.

  96. Smokey says:

    Tree ring studies correlated with CO2 vs temp.

  97. Tom Davidson says:

    Throughout the 20th century there were many (about 65!) volcanic eruptions – averaging at least one eruption of VEI 4 or greater – about one every two years.
    On the other hand, those with a VEI of 6 or more (i.e. those large enough to leave a measurable ‘mark’ on the temperatures – such as Tambora in 1815 or Pinatubo in 1991) number a scant 100 in the past 100,000 years.
    If the Mann-ly models don’t account for this, they are defective.

  98. Smokey

    Have you also got a graph showing the WORST 30 published proxies? Now that would be instructive.
    tonyb

  99. Andrejs Vanags says:

    I don’t understand the part about ‘ Tree rings respond to temperature quite well’. I thought that given that a ‘Hockey stick’ shape is a characteristic signature of fitting a temperature to uncorrelated random brownian noise, that it is proof that tree rings are uncorrelated to temperature and their use should be discarded.

    Take a large number of brownian (red) noise runs , call it ‘tree rings’ and fit the last 1/4 or so of the runs to an upwards slope (simulating temp) and weight the runs (as Mann did) so that those having the best fit have a higher weight and you will always get a ‘hockey stick’. It is a characteristic signature. Garbage in, garbage out

  100. David Duthie, Chem. Eng. Ret. says:

    A few years ago I led a program to recycle municipal sewage sludge as fertilizer. One of our projects, in partnership with with Scott Paper, was to accelerate the growth of cottonwood or black poplar for the purpose of producing white fibre for toilet paper manufacture. The application of bio-solids to sapling poplar plants induced tremendous growth with tree rings as wide as 1/2″ to 3/4″. We referred to the poplars as “nutrient pigs” and their growth out stripped that of unfertilized trees by two to three orders of magnitude. No change in weather, no change in temperature, just a change in nutrient dosage.
    As a teenager I helped keep a market garden in the Fraser Canyon of British Columbia. The land, rich volcanic soil only required water in the very sunny climate to grow the most fantastic tomatoes I have ever tasted. Lots of them. I learned that summer that volcanic ash is rich in plant nutrients. So volcanoes may make it colder but they also sprinkle fertilizer just like flooding rivers and desert winds. I’m pretty skeptical of tree ring proxies.

    Dave Duthie, Delta, British Columbia

  101. RockyRoad says:

    Gene L. says:
    February 6, 2012 at 11:09 am

    Actually, I have another question:

    How is it that dendrochronology, using trees at the limits of their growth range (either boreal zones or at the upper edge of altitude) can be used to reflect GLOBAL conditions?

    It’s a reflection of the author. Only somebody who views himself as the veritable “king” of climatology would view trees in their most lofty position as representative of the entire world. It’s an ego thing.

    The more applicable term to apply to Mann is simply: Epic Fail. He gives the science of geology a very bad name.

  102. Rosco says:

    “who compared tree-ring temperature reconstructions with model simulations of past temperature changes.” ????

    Sure – comparing one fairy tale to another produces “settled science”.

    This has to be the most absurd claim ever – neither of the two is anything more than conjecture.

  103. Rosco says:

    The whole concept is bizarre – the results of assumptions about tree ring proxies compared to assumptions run through a computer model based on assumptions ???

    If an engineer came up with a theory about bending moment based on “science” like this would we let him build a skyscraper ??

    I don’t think so.

    Ruin the global economy and cede control of energy to the Chinese ? – Sure, why not if it reduces CO2 back to 350 ppm ?

  104. ntesdorf says:

    “We know these tree rings capture most temperature changes quite well,”
    No, we don’t! They record what the tree did in response to all external effects.
    More fraud from the Old Master of Fraud.

  105. John says:

    In reporting on this latest from M Mann, the environmental report Energy and Environment closed with this subtle but pointed commentary:

    Brian Luckman, a tree-ring expert and emeritus professor of geography at the University of Western Ontario, says Mann’s paper is interesting, but raises more questions than it answers.
    “They make the comment that given these conditions, and based on their [tree] growth model, a certain number of sites should have missing rings,” Luckman said. “But they never actually go and look at chronologies to see whether they could identify those missing rings. That would be a reasonable thing to do.”

    Let me get this straight….Luckman is suggesting that Mann and company didn’t actually look to see if tree rings went missing for a year or so…..and then they suggest that before writing an article saying that volcanos cause trees to not have tree rings for a year or so, perhaps Mann and company might look to see if the rings actually were missing…a “reasonable thing to do,” even?

    Well, if you don’t validate models, why not go further, and not validate data???

  106. John says:

    On the other hand….if what this article portends is that Mann and Co will soon discover that when corrected, the treemometers actuallo DO find a Little Ice Age, this might be progress of sorts. The blame will go to volcanos and not to solar influences, but that may be of little matter. We appear to be currently at the beginning of a years-to-decades long “natural experiment” that will tell us a lot more about the effect of a changing sun on climate. If a cooling effect is large, then by implication the effect of the Maunder Minimum on cooling will also be large.

  107. All you have to do to understand that the work of Mann is worthless is look to the temperature reconstruction of the last 10,500 years of the GISP2 Project ice core data by R. B. Alley.

    All you have to do to understand the work of Mann is worthless is look at bristlecone pine data 75 miles from the Yamal Pennisula, or those in California, or anywhere else on Earth to see that there is no warming registered at all.

    How does this guy get away with this crap?

  108. F. Ross says:


    “For these trees, growth is almost entirely controlled by temperature, rather than precipitation, soil nutrients or sunlight, yielding a good proxy record of surface temperature changes.”

    [+emphasis]
    So all of the trees at the boreal margin would thrive as long as the temperature was above
    some key point. No water. no nutrients, no sunlight, NO PROBLEM? I don’t think so.

  109. DocMartyn says:

    Given that X-Rays are used to estimate ring density, tree rings are the major storage site of heavy metals in trees, the ‘divergence’ in the Northern Hemisphere matches the removal of lead from petrol/gasoline, I am a bit surprised he is having a go a volcanoes now.

  110. Downdraft says:

    To a logical mind, the fact that the treemometers have a major flaw would prompt one to re-think the whole concept. To MM, it is simply evidence that it is worse than he thought and he needs to lower the shaft of the hockey stick quite a bit to compensate for the lost rings.

  111. Jeff Alberts says:

    Gary Hladik says:
    February 6, 2012 at 2:06 am

    “Using a theoretical model of tree-growth driven by the simulated temperature changes, the team determined that the cooling response recorded by the trees after a volcanic eruption was limited by biological growth effects.”

    Whoa! The simulated trees now agree with the simulated climate! Who’da thunk it? I think these guys should be rewarded with some simulated research grants!

    Methinks Prof Mann has been spending too much time playing The Sims on his Uni computer.

  112. rbateman says:

    It’s amazing what ‘truths’ one can come up with when torturing data as to why it lied oh, so convincingly. Ah, but if Mann had only stopped to ponder that his tree ring hypothesis was based on a shifty proxy. Methinks he barked up the wrong tree. He’s doing it again.

  113. jonathan frodsham says:

    I love reading these posts. Such an inquiring group of people here :-) WELL not all! Some are very stupid watermelons trying to disrupt the natural clean cycle of WUWT.

  114. Mickey Reno says:

    The issue of missing tree rings due to cold years is an inversely proportional problem of ice cores missing years of deposition due to warm years, no? If a year (or decade or a century) has less precip and/or more top-melting, an ice core might represent a much longer period, during some of which the glacier’s growth was negative. Without some very reliable chemical signatures of layers within a core that pins the layers to known dates or events, the certainty of an ice core’s period is much less reliable. And BOTH proxies might have missing (or reduced) signals during DRY years (and here dry=dry during the proxy’s growing season; summer for trees and winter for glaciers). Or am I missing something?

    I’m not saying the cores can’t be useful and should be disregarded. I’m only saying there are more uncertainties and specific meanings can easily be overestimated.

  115. uppsalaumea says:

    The trouble with tree rings or never trust a skinny tree.

  116. Tancred says:

    “The problem is that these trees are so close to the threshold for growth, that if the temperature drops just a couple of degrees, there is little or no growth and a loss of sensitivity to any further cooling.”

    No proxy, then.

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