Comments on: McShane and Wyner Weights on Mann 2008 Proxies

By: Skiphil

Skiphil — Thu, 28 Feb 2013 01:41:49 +0000

Nice, this is a very helpful graphic for those of us coming to these topics more recently. The 2006 CA article at your link is also valuable — those geographic plots of proxy weights really tell a tale.

By: snowrunner

snowrunner — Fri, 17 Jun 2011 08:47:38 +0000

Well…I was trying to suggest a way of demonstrating the absurdity of believing that a weighted average of a few points gave a meaningful estimate of the global mean. But I guess the irony didn’t come across. However, the argument that the global mean temperature isn’t a measure of anything with a physical meaning applies equally well to the whole proxy reconstruction concept.

By: McShane and Wyner Weights on Mann 2008 Proxies « Bee Auditor

McShane and Wyner Weights on Mann 2008 Proxies « Bee Auditor — Fri, 17 Jun 2011 02:30:34 +0000

[...] Source: http://climateaudit.org/2011/06/09/mcshane-and-wyner-weights/ [...]

By: Jeff Alberts

Jeff Alberts — Fri, 17 Jun 2011 00:45:01 +0000

A useless exercise: http://www.uoguelph.ca/~rmckitri/research/globaltemp/GlobTemp.JNET.pdf

By: snowrunner

snowrunner — Thu, 16 Jun 2011 10:19:48 +0000

If the weighted mean of proxy series is a valid estimate of the global mean temperature, then it is surely a short and logical step to assume that the same weighted mean of actual observed temperatures is also a valid estimate of the global mean temperature. Indeed it may even be better than the more commonly used spatially weighted mean. I wonder if anyone has tried this? I mean take whatever temperature series are available for the grid squares with proxies (for the last 50-100 years maybe) and combine them with the PCA weights. This new “global mean” temperature could then be compared with the usual one. If the series are very similar then there is some possibility that the PCA method works. If not, we can draw another conclusion.

By: ferd berple

ferd berple — Wed, 15 Jun 2011 13:21:57 +0000

If one looks at the example above labelled “Gavin Schmidt versions”, you can see that the Pacific South West sample is much larger than all the others.

It would be like giving Liechtenstein greater weighting than India, China and Brazil when assessing population rends.

This suggests that Gavin is engaged in marketing, not in science.

By: ferd berple

ferd berple — Wed, 15 Jun 2011 13:06:27 +0000

Changing the weightings is exactly what is done when training a neural net (curve fitting).

You can achieve any result (curve) you want by selecting the appropriate weightings. If you don’t get the result you want, change the weightings and try again.

It is a simple matter to write a computer program to do this, to select the weighting through trial and error, to converge on the result you want.

Thus, if I was a climate science researcher that wanted to obtain a “hockey stick” shape to eliminate the MWP and LIA, I could do this simply by varying the weightings in my analysis.

However, this is not science. It is marketing (advocacy). You maximize the data that supports your point of view (by increasing the weightings), while minimizing the data that contradicts your point of view (by reducing the weightings).

By: AMac

AMac — Tue, 14 Jun 2011 14:54:03 +0000

HR (Jun 11, 2011 @ 6:13pm) –

If you take the advice Ianl8888 offered (Jun 13, 2011 @ 8:05pm) and look at the Tiljander saga, note also that there are only three independent Lake Korttajarvi data series, although Mann08 uses four. “Darksum” is a computed value, derived by Tiljander as “thickness” minus “lightsum” (all are varve thicknesses in millimeters). (XRD is the final data series).

It was almost certainly another simple and innocent error — the relationship was obscured by the common practice of log-transforming these series before adding them to the proxyhopper.

This mistake is easily understood and verified. However, to my knowledge, it has never been addressed or acknowledged by Prof. Mann, any of his co-authors, or any advocate of the pro-AGW Consensus position.

By: mrsean2k

mrsean2k — Tue, 14 Jun 2011 13:36:18 +0000

It’s always refreshing to see someone else’s incredulous reaction to things that regular observers have long taken for granted.

How anyone can argue that this practice is acceptable defies belief.

By: ianl8888

ianl8888 — Tue, 14 Jun 2011 01:05:38 +0000

Absolutely sure

Start here for the Tiljander lake sediment story:

http://climateaudit.org/2008/10/02/its-saturday-night-live/

If you track this through to the current state-of-play, you will see that the original authors of the Tiljander paper are outraged that their hard-won proxy series was flippantly flipped