Comments on: Example #2 Of Work That Needs To Be Replicated: Dendroclimatology

By: markm

markm — Tue, 08 Dec 2009 02:42:41 +0000

Larry Sheldon: “Is it worth cutting down more really old treas for?”

You don’t cut them down. You drill a hole with a hollow drill and get a 1/4″ thick sample of everything down to the center of the tree. It doesn’t hurt the tree noticeably.

Forty-some years ago, I did a school science project on tree rings, with input from a Biology professor (my father). Graphing the samples vs. weather records basically gave a scatter plot with no apparent pattern at all. Conclusion: at least for certain species growing in town, any effect of weather was swamped by other influences on growth.

Now, if I’d had computers and a half-baked knowledge of statistics, maybe I’d have run correlations until I found some trees that happened to show a correlation to temperature. And if I was a complete idiot, I might even have accepted that for some trees the rings were wider in warmer years, and in other trees they were narrower.

And that is just part of what Mann and his colleagues did. They used computerized correlation functions to search through all the available records from extremely old trees (mainly bristlecone pines) until they found some that showed correlation to the ground temperature records – including some where the correlation was inverted. Then they used the correlation coefficient, positive or negative, to calculate temperature from the ring widths. Naturally, when they averaged these calculated temperatures, the average since 1850 graphed just like the temperature records. They’d picked the few trees that matched well…

And then they extended the temperature calculations backwards, assuming the correlation coefficients remained constant. And the result was pretty much a straight line. Which is also what you get when you average a lot of random data.

IOW, apply Mann’s methods to random data, and you will cherry pick data that just happens to fit the (massaged) temperatures for the last 150 years. That creates the blade of the hockey stick. Then averaging the data from 1000-1850 AD creates a straight handle, because it is random data, and now you’re out of the region where you cherry picked.

And Mann is quite content that his awful mess of a program has been tested and demonstrated correct, because it produced the output he expected. (Idiot…)

This doesn’t prove the hockey stick is wrong, just that it is meaningless. Historical records go pretty far to proving it is wrong, at least where we can find records of what crops grew where…

By: tim heyes

tim heyes — Mon, 07 Dec 2009 19:37:23 +0000

I think the problems of dendrocloimatology run deeper than those mentioned here. The “divergence/hide-the-decline” data suggests to me that the correlation between tree ring late wood density and temperature is overstated at least in some species.

If the post 1960 trees rings indicate declining temperatures but we have direct temperature measurements indicating a slight increase (viewed in the best light), then the reliability of the historical dendro temperature proxies seems to be in question.

I suspect a truer reconstruction is provided by ice cores and lake sediments.

By: JP

JP — Mon, 07 Dec 2009 18:24:31 +0000

ADiff,
I don’t blame the dendros for at least attempting to tie multiple proxies (from different tree species, at different locations and altitudes). Since I began following ClimateAudit 5 years ago, and reading what one must do in order to come up with some magical global climate signal, it has become apparent that thier attempt is nearly impossible. I certainly agree with you that it is almost statistical alchemy that people like Biffra practiced.

By: ADiff

ADiff — Mon, 07 Dec 2009 17:58:46 +0000

Dendroclimatology…now there’s a mouthful! Assuming that temperature alone accounts for growth rate changes is more than a stretch…it’s pure fantasy. Attempting to ‘account’ for the multitude of other factors affecting growth rates must amount to, at best a well intended S.W.A.G, at worst self-deception, as these are literally Legion, and mostly completely un-trackable. These kinds of studies would require dozens, if not hundreds, of identical provenance samples to average out individual variance among the specimens…and even then there are still many other factors affecting growth rates that can’t really be accounted for…. This has to be considered at best a very speculative proxy for temperature, and worst only noise for any practical purpose. I don’t think it’s much of a stretch to say that any climate reconstruction based on tree-growth must be considered simply as a demonstration of a ‘Possible’ climate regime, but with absolutely no evidence of its probable accuracy at all.

By: ADiff

ADiff — Mon, 07 Dec 2009 17:22:50 +0000

Not “akin to Lysenkoism”, ‘Another Guy Named Dan’… AGW today IS Lysenkoism.

By: mbabbitt

mbabbitt — Mon, 07 Dec 2009 04:56:18 +0000

Very bottom line of Climategate: If the skeptics previously had any doubts that their critiques were perhaps wrong or off base in some way, these doubts have been removed. Now they know they were right all along. The fraud has been clearly unearthed. The skeptics are now confident in their skepticism while those on the warming side who have even a scintilla of integrity, are now feeling a bit of a skeptical edge in their previously strongly held beliefs.

By: dearieme

dearieme — Sun, 06 Dec 2009 23:10:48 +0000

All the proxies have the limitation that there’s only about 120 years or so of measured temperatures to compare with. Perhaps some of them rely though on simpler science than the physiology of trees and the ecology of stands of trees?

By: agesilaus

agesilaus — Sun, 06 Dec 2009 21:51:29 +0000

The big flaw in the “it would take too much time to respond to FOIA requests”, is this. If they posted all the data, metadata and software code on a public website at the time that they published in ‘peer reviewed’ journals, then all the information would be public. There would be no need for any major FOIA requests except possibly some small ones for missing details. Indeed the journals, in theory, require that the data be available. But they do not enforce it for these people.

Look in Analytical Chemistry for an example of the way real scientists do this. All the data and the experimental setup are published in each paper. Other chemists can duplicate the work. No secrets and no FOIA required.

By: S.Norman

S.Norman — Sun, 06 Dec 2009 21:24:35 +0000

I think you’ll find that it was “Bishop Hill” who alerted Steve McIntyre to the fact that the Procedures of the Royal Society had a strict requirement for revelation of raw data (and when pressed, they upheld it).

By: Larry Sheldon

Larry Sheldon — Sun, 06 Dec 2009 20:17:46 +0000

Is it worth cutting down more really old treas for?