The UnAustralian

Tuesday, March 18, 2003
A New Low in Climate Pseudoscience: Part 5

This section of this series of posts, deals with Daly's criticism of the use of tree rings to determine past temperatures. Sadly, because of Daly's ignorance/dishonesty, his essay doesn?t deal with the ice core measurements used in the Mann paper, rather he pretends that they don?t exist.

Because I've got virtually no knowledge of dendrochronology, I can't direct deal with Daly?s criticisms of dendrochronology, except to note that some of them seem to be in direct ignorance of one of the principles of dendrochronology; The Principle of Limiting Factors.

So rather than address his concerns directly, I'll attack them from a different angle. The important question of how valuable Mann's research is: does it accurately reconstruct past temperatures?

Daly must have forgotten to mention it, but Mann has put in a lot of effort into validating the results. Basically, Mann took as much historical surface station data as he could find and divided into two categories; stations that measure back to 1902, and those who measure back to 1854. None of the stations that were in the second category were included in the first. The temperature information in the first category was used to calibrate the reconstructed temperature history. Now, if Mann's reconstruction was misrepresentative of the pre-1902 temperature record, the correlation between the reconstruction and the 1854 temperatures should be extremely poor. There is a good correlation.

About now, I should point out that there is one criticism of Daly's that I agree with. The reconstruction doesn't cover the world?s ocean areas. This doesn't make it bad, but rather it is a qualifier that should be keep in one?s mind.

In conclusion, while Daly lists a number of reasons as too why dendrochronology may not work, he doesn't deal with the extensive validation efforts that were performed by Mann and coworkers.
| 6:36 PM