This is for entertainment only. Given the week we’ve had, I thought it might be interesting to gauge some opinion about dendroclimatology. While we can certainly argue the merits of “who said what” etc. the question on my mind is what do people think of the technique of using tree rings for determining past climatic history?
Readers, please invite others at non skeptical blogs to participate, use the “share this” link. I’ll extend a blanket invitation to anyone to participate, no matter what your view might be.
Since this is a highly polarized issue, I’ll note that the poll code is setup (by WordPress.com) to minimize the possibility of vote stuffing and encourage one vote per person. You’ll know you’ve hit that security feature if certain messages are displayed.
Here’s the poll question:
Of course I should add that no online poll is scientific, it is only an interesting and entertaining exercise in gauging the opinion of people who visit here.
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My degree in botany taught me that plants have a variety of responses to environmental conditions. Tree-rings have proven good for archeological dating, but beyond that too many factors confound their clear interpretation as signals of climatic changes.
I do not necessarily dismiss tree rings from consideration, but they appear to be of limited usefulness due to the many environmental factors that affect tree growth.
The use (abuse?) of tree rings in studies by Mann, Briffa and other members of the profession have not given me or many others great confidence in either the ability of tree rings to measure paleoclimate or in the competence (ethics?) of some researchers.
[snip – Tom, too many forbidden words here casting aspersions on scientists]
I can not imagine what kind of a fool it would take to think that tree rings could tell us temperature. Think of the “scientists” who discounted the actual known historical record of the medieval climate optimum and also the little ice age based on what a few trees might reveal via their tree rings. Utterly amazing.
I think this poll is misleading as it almost advocates science by referendum. A careful line not to cross…
REPLY: Well that certainly was not the intent. I don’t think you’ll find many “science by referendum” studies or publications that have a picture of Snoopy and Woodstock in it. It was intended to gauge opinion of visitors to WUWT and to be entertaining and interesting, nothing more. It is the weekend after all.
But since you’ve demonstrated that some folks might get the wrong idea, I’ve made it clearer. Thanks. – Anthony
I have 2 identical species of trees planted at my house – one on the southeast corner in full sun that gets lots of water and one in the northwest corner in the shade that gets little water. After 8 years, the one in the sun with water is twice the size of the other. How could one make any interpretation of climate based on such trees?
True, these trees are affected by artificial (man-made) influences, but use of trees to estimate climate also seems fraught with a huge range of local environmental influences that simply cannot be accounted for.
My opinion: tree rings are interesting, but should be used with utmost caution and only when a very large sample of trees corroborates other sources of data with very little deviation.
The thickness of tree rings is heavily influenced by rainfall which can be heavy during cold or warm seasons or periods. Thus dendrochronology is a weak proxy for gauging temperature.
I collected some tree ring data as an undergraduate 30 years ago. There’s an inherent bias in that healthy trees are preferred, so all selected trees started life in good times. Bad times are gauged from those trees which successfully lived through them. Microclimates — such as if the tree is on a south-facing concave vale, or north-facing convex slope, or competition from neighboring trees — rule. You can only get climate information from features shared across most samples. So it is the median measure for each year which counts. You need to use all the data to get the median. Theoretically some selectivity could be needed, but only if the on-site collection was top-heavy by microclimate — you’d hope the sample collectors were better than that. Briffa’s concern that samples should be from multiple locations is correct, but one location is valid if it is a big enough “location”. A few trees from one location would be worth more per tree than many trees from one location, so you scale their importance as the square root of the number of samples, up to some maximum. So Briffa’s expressed concerns are good science, but not comprehensive I suspect.
FYI: I believe the correct term is dendrochronology. Never heard of nor could find anything on dendroclimatology.
Reply: Really? There is this thingy called Google you may want to try. ~ ctm
Plant development is a complex biologic process and small changes to a plants circumstances can have a big impact on rate of growth. Any group of plants growing in the same location, under similar conditions will show a range of growth rates due to genetic makeup and small natural variations – trees included.
Trying to use trees as proxies to measure small changes in temperature, which is then applied to produce global estimate of change is clearly risible. The Mann and Briffa hockystick graphs prove this to be the case as their temperature reconstructions bear no relationship to historic records.
Tim at 12:52 brought up a good point. A long time ago, my dad planted two oak trees about 7 feet apart. One tree grew 3 times as fast as the other tree. It grew 3 times as fast because it was getting the rain water run off from the house and was in a sunnier spot. Both trees are now cut down, but I remember my dad remarked about the differences in sizes despite the trees being planted at the same time.
Google:
Results 1 – 10 of about 154,000 for dendroclimatology. (0.47 seconds)
It may be a new, contrived, compound word. But 154,000 hits indicates it
is being used.
Its hard to see how tree rings were ever calibrated as a temperature proxy considering the number of confounding variables. The correct choice in the above poll therefore is “#2: the tree derived temperature data has been called into question.” There is nothing unsure about this.
My guess is that the whole problem is that trees are SOMETIMES halfway decent thermometers. But when which ones were, and when?
I hope this isn’t “off topic”. But I’m the orginal “contrarian” I believe when it comes to using O18 to 016 as a proxy for “temperature”.
I think the geophysics types and hydrologists would tell you that since the common availability of Mass Spec devices since WWII (probably even more so in the 60’s and ’70’s) O16/O18 ratios were used to trace water outflow from costal regions, with the concept that THUNDERSTORMS IN COSTAL REGIONS enriched the O18 isotope.
One can argue that a higher O18 number represents higher temperatures, as the O18 to O16 goes UP in even inland thunderstorms during the peak temperature summer months versus spring or fall.
But it should be obvious the NUMBER and INTENSITY of the TS’s will ALSO INFLUENCE THE AMOUNT OF O18 to 016.
I will submit, therefore, that the O18 to 016 ratio is a proxy for “atmospheric energy”, but that may or may not have any correlation with Troposheric temperatures (seasonal).
JK
You are not a warmist climatologist are you? You are certainly displaying the initiative and inquisitiveness of one.
I planted 12 boxwoods a couple of years ago in front of my house. Six get more sunlight and water because of a spruce tree and an overflowing eave trough, and they are 50% bigger on average. So I think tree rings are an unreliable proxy for temp
Besides the obvious complexities of other climate and botanical factors, the need for extensive metadata appears to be essential in order to control for the many environmental factors that can influence tree growth. Given that the environmental data changes through time as well as does climate, I am not very optimistic as to the robustness of trees as temperature proxies.
Treerings are not entirely useless from a climatological point of view. Most chronologies do reflect years with extremely bad weather – usually caused by major volcanic eruptions. Years like 1453, 1601, 1783, 1816 are found in most northern hemisphere treering series. Beyond that I am very skeptical.
It should be noted that treering chronologies were originally developed for archaeological dating, and in that field they have been brilliantly successful, as they have also been for calibrating radiocarbon dates.
There might be some correlation between tree ring widths and temperature, but surely you cannot get from them accurate measurements to one tenth of a degree. The attempt to created temperature “records” 2000 years back, with a resolution of one tenth of a degree is absolutely insane. When I first saw the Hockey Stick, it took me all of 10 seconds to deduce it was bunk. I just looked at the numbers on the vertical (temperature) scale, divided into tenth of degrees.
Being an engineer, I have some grasp of what numbers convey.
Well, I voted unsure. I agree with Bernie, the metadata is lacking and this seems to me to be a neccessary prerequisite for their use as temperature proxies.
I was under the impression that the only certain thing you could learn from tree rings was the tree’s age when it was cut down. Differences in width of the growth rings couldn’t possibly tell you anything with mathmatical certainty. They would only show that conditions were more or less favorable for growth during the tree’s lifetime.
Historical records and passages in literature of the day would seem to me the best indicator of the general temperature range during a particular period.
Evidence provided by an actual referendum, while very limited, still beats the blatant assertions of consensus and ‘settled science’.
A sole tree can certainly not tell of global past climate, however, the GLOBAL tree population, past and present, might tell us something useful.
I’d vote yes to,
With a sufficiently large sample of trees there should be an atmospheric temperature signal.