Comments on: The Gift That Keeps On Giving

By: The Hockey Stick and the Milankovitch Theory « Climate Audit

The Hockey Stick and the Milankovitch Theory « Climate Audit — Wed, 03 Feb 2010 11:23:12 +0000

[...] why this was done has been somewhat a mystery. Two years ago Steve wrote notes about the issue (here, here, and here). It is worth reviewing those before continuing reading this [...]

By: UC

UC — Sun, 09 Dec 2007 19:45:57 +0000

Willis,

see first figure of
http://www.climateaudit.org/?p=2344#comment-159797

this PC1 adjustment warms the AD1000 reconstruction. But it doesn’t affect 1400-1980 reconstruction (stepwise reconstruction, u know, new proxies enter the game at 1400). Total effect is this long-term cooling trend .

Splitting the linear trend fits to two parts (1000-1399 and 1400-1850) helps to visualize what happens:

http://signals.auditblogs.com/files/2007/12/trend2.png

By: Willis Eschenbach

Willis Eschenbach — Sun, 09 Dec 2007 19:22:36 +0000

UC, if I understand you, that is quite astounding. Mann takes the 150 year smooth of the 75 year smooth of two 50 year smooths, one of which is the average and the other the PC1 of two different hand-selected groups of trees. He asserts (without confirmation) that this triply smoothed curve represents a pulse of growth, attributable to CO2, which starts around 1700 and ends around 1900. He then uses that hypothesized growth pulse to cool his reconstructed temperature … is that a correct summation of the plot to this montebank’s novel?

mountebank – “a doctor that mounts a bench in the market, and boasts his infallible remedies and cures” [Johnson], 1577, from It. montambanco, contraction of monta in banco “quack, juggler,” lit. “mount on bench” (to be seen by crowd), from monta, imperative of montare “to mount” + banco, var. of banca “bench.”Online Etymology Dictionary. Douglas Harper, Historian. 09 Dec. 2007. .

By: UC

UC — Sun, 09 Dec 2007 09:36:34 +0000

Willis, see also

http://www.climateaudit.org/?p=2344#comment-159821

shows the effect of this adjustment in the MBH99 reconstruction.

By: Willis Eschenbach

Willis Eschenbach — Sun, 09 Dec 2007 03:47:04 +0000

Hu, thank you for a most interesting post. That's the most convoluted piece of logic (Mann's, not yours) that I've seen in a while. It seems like the long way around to prove anything about anything, using triple-smoothed residuals ... w.

By: Hu McCulloch

Hu McCulloch — Sat, 08 Dec 2007 17:32:53 +0000

Willis #31 –
See my comment #63 on the next thread (#2355). As a CO2 adjustment, the MBH99 procedure is entirely bogus. All they did was hand-craft the secular trend by replacing that of PC1 with that of the Northern Treeline series, while preserving the desired higher frequency HS blade at the end of PC1. I think the purpose was to generate a modicum of LIA-like action.

By: D. Patterson

D. Patterson — Sat, 08 Dec 2007 08:58:29 +0000

31 Willis Eschenbach says:

December 7th, 2007 at 9:14 pm
[....]
I gotta be missing something here

w.

Danger, Will Robinson! Model instability detected, chaotic thermal equilibrium imminent.

By: Willis Eschenbach

Willis Eschenbach — Sat, 08 Dec 2007 03:14:48 +0000

I gotta be missing something here, anyone please jump in where I’m wrong.

We take a bunch of Jacoby tree chronologies, and we average them (bad start, but oh well).

We take a bunch of Mannian PC chronologies, and take their PC1. One hopes correctly.

We subject them both to 75 year smoothing.

We subtract one from the other to get the residual.

We smooth the residual with a 50 year filter.

We filter out everything with a timescale less than 150 years to get the “secular trend”.

Now if the null hypothesis were that Jacoby and the PC1 were both accurately measuring the same thing, I’d say we could confidently reject the null hypothesis … but beyond that, what does this residual mean? My only conclusion from this is that one of these is true:

a) Jacoby and Mann PC1 are accurately measuring different things.

b) Jacoby and Mann are inaccurately measuring the same thing.

c) Jacoby and Mann are inaccurately measuring different things.

My money’s on “c”, but your mileage may vary.

But the real question … what on earth does the difference between Jacoby and PC1 have to do with CO2? Is the claim that one of these is affected by rising CO2 and the other is not?

I gotta be missing something here …

By: Hans Erren

Hans Erren — Wed, 14 Nov 2007 20:58:25 +0000

The way I read the graph: on the y-axis is the yield the coloured lines are ambient CO2 isolines.
The yield peaks for higher ambient CO2 at a higher optimum temperature .
The optimum yield is logarithmic to ambient Co2 concentration:

co2 yield Topt 100 5 15 250 10 17 500 17 22 1000 25 25 2000 30 30

in an excel graph:

By: dscott

dscott — Wed, 14 Nov 2007 20:14:20 +0000

#17, Hans, Not being a reader of Dutch, but of German, what I make out of this graph from the referenced webpage is that the 3rd graphic, which the one you posted here shows the growth (rate of photosynthesis) of paprika plant in response to various CO2 levels as the temperature rises. I find it interesting that not until you get higher than 2000 umol m2 s1 that an increase occurs as temperature rises from 15 to 30 C. It looks like from the graphic if one were interpolate in reverse, lower CO2 levels favor cooler temperatures for higher photosynthesis rates. Wouldn’t it be also reasonable to infer that high CO2 levels allow for higher rates of photosynthesis at higher temperatures for this specific plant? Given that water is integral to plant growth, wouldn’t this support the finding that a CO2 level causes plants to use less water, i.e. are more drought resistant?

The 2nd graphic shows the effect of increasing light intensity with various levels of CO2.

Maybe I’m ignorant, but since when do logarithms bend down like that graph?