Comments on: Tasmanian Tree Rings

By: TCO

TCO — Wed, 12 Apr 2006 11:15:55 +0000

Sid, that’s one reason for advocating double-coring trees. (Although one could probably make a DOE-type argument that you’re just as well off, sampling more trees).

By: ET SidViscous

ET SidViscous — Wed, 12 Apr 2006 04:07:51 +0000

“Do they really measure tree ring widths to 1/100 or 1/1000 of a millimeter? ”

Didn’t see this before.

What is the variation around the entire circumference? I’ve yet to see a tree ring that was a perfect circle, and I don’t mean the band, (Real music Steve, not L’il Kim type stuff).

I can’t see where the error is going to be less than .1mm, and that only if you measure at 720 angular points or so and determine an average.

Hell I’d rather calculate Global Mean Temperature, lass grunt work.

By: Steve McIntyre

Steve McIntyre — Wed, 12 Apr 2006 03:58:48 +0000

#29. Although Rob Wilson thought it unlikely, the Tasmania data is definitely jumbled. Some of the individual trees have 999 tags and some of them have -9999 tags. So the data can be disentangled. But the data has to be extracted in an ad hoc way to do so.

By: John A

John A — Tue, 21 Mar 2006 21:17:31 +0000

Do they really measure tree ring widths to 1/100 or 1/1000 of a millimeter?

By: Steve McIntyre

Steve McIntyre — Tue, 21 Mar 2006 16:02:54 +0000

I was looking at some Mongolian data and noticed that the mean ring width for the Jacoby series ws about 10 times greater than the mean ring width for Schweingruber series. I asked for clarification from a specialist who told me that later dendro versions tend to be in 1/1000 mm while earlier ones tend to be in 1/100 mm. The ITRDB data bank has no metadata describing the units, which creates a problem even for specialists.

For Cook’s Tasmania data, I’ll bet that the modern data was done earlier and is in 1/100 mm, while the subfossil data is in 1/1000 mm. However, the two differing units are jumbled together in the ITRDB archive. As I noted before, this would not make any difference to STD standardization, but would make a difference to RCS versions applied to this data.

I notified Cook some time ago about the bimodal distribution, but he did not reply and the matter does not seem to have been corrected.

By: Steve McIntyre

Steve McIntyre — Mon, 27 Feb 2006 21:29:52 +0000

Doug, it’s probably worth resolving. Cook’s standardization methods are probably on a tree-by-tree basis (not RCS) so that a gross error like this would not actually make it difference to his chronology – which is interesting in itself.

By: Douglas Hoyt

Douglas Hoyt — Mon, 27 Feb 2006 20:47:49 +0000

Re #23, I would tend to agree with Evan. The slow growers were probably measured by one group using centimeters. The other trees were probably measured by another group using millimeters. The two groups were probably combined and no one noticed the units problem. Perhaps that is why Cook did not answer.

In any case, it looks like the data as it is would give a downward pointing hockey stick. Doesn’t one of Mann’s steps invert downward sticks into upward sticks? Maybe that is why they are happy with the data as it is.

By: TCO

TCO — Sat, 10 Sep 2005 23:26:19 +0000

Publish, publish, publish! Sheesh, we finally have a chance for you to publish something that is not just a Republican/Exxon plot to discount GW. You’ve actually added a bit of knowledge here, vice just exposing a fraud.

By: Steve McIntyre

Steve McIntyre — Fri, 09 Sep 2005 04:37:10 +0000

Re #17 – Mount Read and Lake Johnston are the same site.

By: Steve McIntyre

Steve McIntyre — Thu, 08 Sep 2005 01:40:27 +0000

Re #23: I’ve seen giants turn up when I’ve done plots of other sites, so they are probably real. There seems to be a type of “alpha tree” phenomenon where they keep strong even as they are very old. They really screw up the RCS adjustment where a standard aging adjustment is done, because the alpha trees just keep on going.

Could there be a lot of errors in the underlying dataset? I would be the last person to deny this possibility. A lot of the ITRDB chronologies end in the 22nd and 23rd century because of a computer programming error. But in this case, I think it’s real. I sent these diagrams to Cook some time ago but he did not reply. (These are the same people who won’t reveal the location of the Gaspe cedar site.) It’s worth asking, but I won’t be able to get an answer.