Comments on: More on the Divergence Problem

By: BobFJ

BobFJ — Mon, 30 Jul 2007 01:21:40 +0000

The following quotes from Increased snow is shortening tree-growing season in subarctic Siberia – Science Daily, are exquisite!

…”The recent weaker correlation between tree growth and temperature clearly affects the reliability of our reconstructions of the past. Actually, it means past climate reconstructions (before the 1960s) are better than we thought they were. And, as a result of this, it means that we underestimated the differences between the present century and past centuries,” Hughes said…
…The contrast between this century and previous centuries may be greater than thought, Hughes now suggests, because “our calibration is contaminated partly by this recent weaker correlation.”…

Did Hughes actually say that?
Did they really calibrate their proxies in the period of divergence?
Where is there data for snowfall at individual sites, say at 1200 AD?
etc!

By: Steve McIntyre

Steve McIntyre — Wed, 09 May 2007 04:03:20 +0000

#59. I re-read my post on Cook et al 2004. There’s nothing in D’Arrigo et al that addresses these issues.

By: Steve Sadlov

Steve Sadlov — Tue, 08 May 2007 21:27:56 +0000

RE: #60 – A bit of clarication regarding coast live oak dormancy. There is not an overall leaf drop. The leaves are waxy and thick with short spines protroding at the ends of the lobes (like holly). There will be some slight drop of selected leaves during very hot periods. There will continue to be a very low, maintenance level of photosynthesis, not complete stoppage. But there will be no growth – no addition of wood mass, if anything, slight shinkage due to moisture loss. When the seasonal dry ends, the response is not immediate – it take a few weeks for the trees to “wake up.”

By: Steve Sadlov

Steve Sadlov — Tue, 08 May 2007 21:20:17 +0000

Some more observations vis a vis my coast live (evergreen) oaks and douglas fir. The oaks have already hit their growth maximum for the year and are rapidly slowing toward their (expected, annual) summer dormancy. The dormancy corresponds with our annual low-no precipitation period. They will be fully asleep by the end of the month and will not awaken again until sometime late in the fall or early in the winter, assuming of course we actually get rains then. The doug fir are still growing at a moderate rate. They are a bit more drought hardy than the oaks (although, I would add, it’s a wet-dry climate seasonal hardiness – I believe that during a protracted drought – e.g. two or more years of statistically significant below normal annualized precip – the oaks are actually better able to survive). They will go dormant prior to the 4th of July. How does all this stack up with the belief system of the Dendro Truth Squad?

By: Steve McIntyre

Steve McIntyre — Tue, 08 May 2007 19:50:01 +0000

#55, 56. I posted last year on Cook et al 2004, describing it as more cargo cult science in Briffa style See post 586, also 570 and 529 are relevant.

By: MarkR

MarkR — Tue, 08 May 2007 19:26:25 +0000

#56 Willis. Perhaps you could put up one of your excellent graphs, or tables of inter correlation showing the divergence between the proxies, while Mr Wilson is about?

By: Mark T.

Mark T. — Tue, 08 May 2007 19:26:18 +0000

Using the reconstructions, of course. Bristlecones are welcome to apply for the job.

Mark

By: Willis Eschenbach

Willis Eschenbach — Tue, 08 May 2007 19:10:54 +0000

I had a different question about the quote:

“A recent analysis by Cook et al. (2004a) suggests that the divergence is restricted to the recent period and is unique over the past thousand years. It is thus likely to be anthropogenic in origin.”

My question is, how would one detect divergence in, say, the year 1156? …

By: MarkR

MarkR — Tue, 08 May 2007 18:58:05 +0000

From D’Arrigo, Wilson via Pielke, apparently…

“A recent analysis by Cook et al. (2004a) suggests that the divergence is restricted to the recent period and is unique over the past thousand years. It is thus likely to be anthropogenic in origin.”

Don’t any of these Dendros realize that their chosen proxies only correlate over the recent period because they’ve been cherry picked for the calibration period. Even then, the cherry picked proxies don’t correlate prior to the calibration periods they are chosen for.

By: bernie

bernie — Tue, 08 May 2007 18:49:52 +0000

#52
bender:
I am not sure I get how replication per se solves the problem versuses hides the problem if the source of variability is not random?