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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plus extra co2 in the air from burning ‘fossil fuels’
Exactly, what does a 100ppm increase in CO2 do to tree growth?
I am surprised we do not have far more hocky sticks.
Air temperature need not change at all. Normaly the hockey team likes to make ajustments. If the recent years in all these treemonitors were adjusted down for the increase in CO2 what would they show?
I wonder if trees also suffer from lack of carbon dioxide when they are growing in dense growth at the bottom of a poorly mixed air column. Sort of the situation you’d find over an Iowa cornfield on a calm day.
I posted this over at lucia’s, but it applies here very well.
Jeff Id over at tAV said it very well in his post -RC Off the Deep End-
“So the possible sorting of data suggested in the quotes given — is actually standard practice.”
Gavin’s rants over at RC about accusations of cherry-picking are oxymoronic in the extreme. The whole approach of cherry-picking proxies because only some have a positive correlation with measured temperatures invalidates the whole mess.
Its PaleoRorschachism, a new CAGW-created psychosis. Perhaps it can be added to the excellent list of things caused by global warming over at numberwatch.
http://www.numberwatch.co.uk/warmlist.htm
Please have a permanent link to Caleb’s guest post.
I agree with the CO2 comment. Clearly, more CO2 will cause the trees to grow faster. This would somehow need to be accounted for. But how? Is it a linear response? Or, something else?
I voted “Unsure”…
Like all proxy data, tree ring analysis has limitations. Despite its flaws and recent possible misuse of tree ring data, I think it is still a valuable paleoclimatology too.
I voted “no” but the study is worth pursuing. If you don’t ask, you don’t larn nuthin.
Methinks the time for debate is over. Looks like a consensus to me. 😉
Now can we ditch all the extra ‘carbon taxes’?
I don’t know if this took so delete id it’s a repeat
With the debate about tree ring data and “global warming, I though I’d compare tree ring data to long term temperature data. The tree ring data I found from http://www.climatedata.info
With tree ring Nor. Hem. proxy data shown below, using the 20 year MOV Norway, Sweden & Russian data, since they were more compatable to Ave14 defined below:
http://www.climatedata.info/Proxy/Proxy/Proxy/treerings_northern.html
Next I took the 14 longest temperature records from http://www.rimfrost.no/
plus the east English data starting in 1659. I averaged the whole bunch up to form a composite average Ave14. This is shown below:
http://www.imagenerd.com/uploads/ave14-smoothed-rev_cheb-j0m9Y.gif
I then added 40 year filtering consisting of a MOV, Fourier filter, and a 2 pole reverse Chebushev filter. The later is found in MATLAB as “filtfilt”. Basically the later filter is run forward and then backward to compensate for phase delay. Unfortunately the end points generally will have a significant error, but is a good cross check for date in the middle of the sample. The Fourier gives much better end point results, comparable to the EMD method.
The figure below compares the 20 year MOV averaged tree ring data with the 20 year MOV Ave14 data. The tree ring width is plotted against temperature.
http://www.imagenerd.com/uploads/ave14-tr-noswru-C3EAh.gif
For what it’s worth, it’s in the region where it “kinda looks” correlated, but would need more sophisticated analysis to show anything definite. From this short analysis, if I were a betting man, I would note bet the farm on tree ring data, much less the chicken coop.
The other thing to consider is it might be possible to use treering data and have it actually mean something about C02 if the sample size is sufficiently large to average out those near-environment issues that impact individual trees like shade from elders being removed over time, and nutrients. But then we’re probably talking about sample sizes in the thousands (tens of thousands?), not 12, 10, 1. . .
Each tree grows within its own microclimate. While many of these microclimates may be similar, few, if any, are identical. A given species has evolved to tolerate a wide range of variation in its microclimate, which broadly defines the range of the species.
BUT, the number of unidentified variables controlling any one tree approaches infinity. Therefore it is nearly impossible to define a statistic that accounts for these variables well enough. Tree ring chronology is independent of climate (with the exception of seasonality in some species), hence its usefulness for dating. No such independence exists for correlation with temp, and perhaps even moisture.
Treelines and range limits are better, but even they have issues. Treelines are plagued with the variability introduced by edge succession, and the accumulation of humus, which is a huge modifier of the microclimate, and hence, the stability of the treeline.
Complex plants and animals are lousy proxies for just about everything, due to their acquired adaptibility.
Mike O (08:12:57) :
I agree with the CO2 comment. Clearly, more CO2 will cause the trees to grow faster. This would somehow need to be accounted for. But how? Is it a linear response? Or, something else?
Honoring truth, there are some forests that don’t do it well at high concentrations of CO2. I am referring to concentrations of CO2 above 1000 ppmV. In general terms, tropical, subtropical and equatorial forests do it well at high concentrations of CO2. Our plants, I mean plants for food, do it superb at very high concentrations of CO2.
You may violently disagree with the covenants of common law (precedent), but it little profits that you rant about its injustice. File a brief with your own pro argument carefully researched rather than the criticism that “the law is a ass.” The frequently-heard reductio-ad-absurdum “treemometers” is such a sweeping condemnation.
One commenter above wonders what kind of a fool would have his perception clouded by such findings that would call into question “the actual known historical record of the medieval climate optimum and also the little ice age based on what a few trees might reveal via their tree rings.”
It seems to me that much of our understanding of paleoclimate history is based on tree rings and other (similarly-fallible) sciences which depend upon years, centuries, eons of layer-deposition, and that we might do with a bit of careful review of the science here before we proudly don the mantle of Mr. Bumble.
I vote “yes” with the caveat / hope that the science continue to be funded and studied by a less-restricted, more open body of scientists, and that its findings be much more clearly understood and accessible before they are used as a criterion for enacting sweeping political and economic changes.
Antonio San (12:52:01) :
“I think this poll is misleading as it almost advocates science by referendum. A careful line not to cross…”
Would you apply the same kind of thinking to “there is a scientific consensus about AGW?” Is this not akin to “science by referendum?”
Consensus is not scientific fact, whether on WUWT or at the IPCC.
Jimbo
I’ve perused this discussion and have seen a lot of good observations made. However, I see no mention of this. Forgive me if I m duplicating someone else’s observation.
One of my (many) reservations of using ‘treemometers’ is that they don’t work about half the time, i.e., trees don’t grow when sunlight (the daytime) falls below a given minimum, which of course is from mid-fall to mid-spring, depending on the species. The APPLICATION of the treemometer data wrt to global warming is to derive an average YEARLY global temperature. Any temperature signal derived at all from tree rings must necessarily give only an indication of the temperature during the growing season. I’m sure you can see the problem: a warm winter can negate a cold summer, cold winters negate a warm summer, and so on. In light of the miniscule temp changes under debate, why would anyone want to try to reconstruct past temperature data from only the growing season? Why would any reasonable person accept such data as proof of small changea in yearly temps?
Tree ring data perhaps could serve as a proxy for rainfall, temperature, air quality, carbon dioxide, soil fertility, sunlight, etc. But for any meaningful information to be derived from tree rings, a very large sample — hundreds, if not thousands — would be required.
If the studies that created the “hockey stick” temperature rise hoax were based on a very small sample, were they in effect a “bearing of false witness” against truth and even me, a nonbeliever of AGW? Were they a deliberate, unconscionable assault on God’s eighth Commandment?
Did this false witnessing create the basis for the current AGW hysteria that our foolish politicians in Congress may soon address by creating a carbon tax that will kill more jobs and further debilitate our desperately struggling economy? Will this false witnessing result in a totally unnecessary poisonous dose of taxation like the deadly adulterated Kool Aid elixir Jim Jones prescribed for his misguided flock of believers at Jonestown, Guyana, a number of years ago?
Let’s hope the evolving revelations about that junk “science” may provide a desperately-needed antidote.
Tree ring data is very useful since it gives a date to optimal and sub-optimal growing conditions for that particular tree.
However one is unable to tell if the conditions were global (meaning macro rather than totally world wide) or local (around that one tree) without using a large sample of trees.
It is a very interesting and valid area of study but one should be hesitant about announcing a world wide trend based on one tree.
It is the usual “small sample” problem to be found in any area of science. (Coupled with more than one factor being responsible for the results).
Jimbo (13:17:33) :
Antonio San (12:52:01) :
“I think this poll is misleading as it almost advocates science by referendum. A careful line not to cross…”
Would you apply the same kind of thinking to “there is a scientific consensus about AGW?” Is this not akin to “science by referendum?”
Consensus is not scientific fact, whether on WUWT or at the IPCC.
Jimbo
There is a valid (scientific) consensus.
“Treat the conclusions with caution and examine the original data.”
Nic (15:38:35) :
Tree ring data is very useful since it gives a date to optimal and sub-optimal growing conditions for that particular tree.
Given that we cannot be sure about the factor that have influenced on the optimal growth of that tree, we cannot use treering data for deducing a particular factor, except a best photosynthetic performance. 😉
If tree ring growth can be affected by other factors such as rainfall, nutrients, sunlight and maybe CO2 then you have to correct for all of those things before you can get meaningful temperature indications. Do the researchers make those corrections? If so, how do they know the history of those factors? And why do the ten trees not all tell the same story. One shows an upward surge at the end. Another shows a downward trend since 1925. Others show an upward trend, which mostly occured before 1925. Which trees are telling the truth and which trees are lying?
But even if the tree ring data can give a good indication of the local climate history, how much can it tell us about the climate of the world? Do the ten trees in Siberia know what the climate was like in Michigan, or Mexico, or Africa, or Brazil, or Australia? I wouldn’t want to bet my lunch money on it.
Once we look around, we start to notice that the evidence argues strongly against the idea that growth can be directly coorelated to temperature. I’ve started paying attention (prompted in party by discussions on this site and CA) and it seems everywhere I look there is contrary evidence:
– similar plants as my neighbor in our gardens this past year; huge difference in growth, despite identical temperatures
– identical plants in different parts of my yard, huge difference in growth, depending on soil and whether the sprinklers were working in a particular area or not — temperatures absolutely identical
– different growth for different trees of the same kind at the local park, despite identical temperatures
Without controlled experiments, it seems impossible to control for all the variables at a historical site in the past. I’ve certainly seen no evidence that it is possible to tease out temperature as an isolated variable.
Which brings me to the question I’ve asked before. Surely this issue has been on the table long enough that someone has undertaken by now a controlled study of growth vs. temperature and other factors? There ought to be plenty of good data by now on how trees respond to various factors.
Eric Anderson (21:47:14) :
– similar plants as my neighbor in our gardens this past year; huge difference in growth, despite identical temperatures
– identical plants in different parts of my yard, huge difference in growth, depending on soil and whether the sprinklers were working in a particular area or not — temperatures absolutely identical
– different growth for different trees of the same kind at the local park, despite identical temperatures
Hi Eric… There are many external factors which influence on plants growth, insolation the main factor among them; nevertheless, the most important factors are the inherent factors, specifically, genetic information. As in animals, plants also inherit deficiencies, aptitudes, advantages over other individuals, etc.
A single error in the production of a protein would lead to disease and deficient growth. Some genetic errors can be corrected through alternate pathways, but many other cannot be corrected; consequently, not all the trees grow homogeneously even under the same optimal conditions.
For example, by a single genetic failure regarding the production of a volatile substance which acts like a repellent against insects, some bristlecone pines tolerate the friction from insects, while others pines, living in the same ecological area, do not tolerate the friction from insects, which will slow down or stop their growth. You could see a bulky tree which could be a very weak tree that will succumb before a plague.
Definitely, treerings are not adequate proxies for investigating paleotemperatures.
I am personally keeping an account of all the ”science” and noting how it affects my very expensive lifestyle, when the billion$ lawsuits start to fly I want my corner.
BTW IS it possible to over lay the tree plots with the global temperature plot to see how they line up?
David Segesta (12:01:41) :
BTW IS it possible to over lay the tree plots with the global temperature plot to see how they line up?
Yes, it is possible. There are minor problems, like the longitude of the periods covered by other proxies for example, but this problem can be solved by taking individual databases and collating them with the tree plots.