Comments on: Screening Proxies: Is It Just a Lot of Noise?

By: Neil Fisher

Neil Fisher — Sat, 07 Jul 2012 03:58:12 +0000

Steve Mosher says:

If the LIA is the result of changes in solar forcing ( which is small) then that is a large change in T
for a small change in Watts

If the LIA is the result of (cloud) albedo changes that just happen to correlate at that time with solar forcing variations, then the sensitivity to solar forcing can be small and we can still have the LIA @ -1C.

Yours is the classical “one parameter explains it all” fallacy – if there are several, uncorrelated forcings that happen to coincide at various times, or even worse, if they each have *some* effect on the others, it’s a wicked problem with no easy solution. ISTM that climate is indeed just such a problem.

By: Gergis 2012 Mark 2 – Hurdles to overcome « ManicBeancounter

Gergis 2012 Mark 2 – Hurdles to overcome « ManicBeancounter — Wed, 27 Jun 2012 22:10:35 +0000

[...] the results in favour of the desired result if that correlation is with a short period of the data. RomanM states the issues succinctly here. My, more colloquial take, is that if the proxies (to some [...]

By: Geoff Sherrington

Geoff Sherrington — Tue, 26 Jun 2012 04:10:04 +0000

There is something spooky about sending a a contribution on noise that gets a neat table mangled into noise. But one can follow it, as Jef has done with his comment that followed. Thanks, Jeff. It was meant for me, was it not ? Maybe not ? No?

By: Jeff Condon

Jeff Condon — Sat, 23 Jun 2012 13:38:01 +0000

“My bet is if RomanM redid his analysis using red noise, and examined the frequency domain response, for smallish N, he’d have a bigger deflation of scale at low frequencies than high frequencies.”

No question. Mann 07 used this knowledge to create unrealistically high frequency proxies and then point out that there was minimal deflation of scale.

By: Jeff Condon

Jeff Condon — Sat, 23 Jun 2012 02:50:07 +0000

It is rare that I would miss a post like this.

Good stuff.

By: Carrick

Carrick — Fri, 22 Jun 2012 05:04:11 +0000

Nice, MT!

You can really see the difference in scale when you have “significant” climate signals like the 1815 Tambora and 1883 Krakatoa eruptions.

By: mt

mt — Fri, 22 Jun 2012 03:10:22 +0000

As a bit of a wrap up, here's a view of reconstructions with different screening algorithms using the simulated proxies. Each graph shows the black temperature series, the red composite screened proxy series (average of standardized proxies) and the green reconstruction. The gray regions show the calibration range. The proxy count from the correlation screen was used in the MSE/random screens. Cal.MSE is the calibration MSE, MSE is the pre-calibration MSE. For the simulated proxies: Correlation gives an enhanced temperature signal in the calibration range, which is then causes the muted response in the pre-calibration region during reconstruction. Standardized MSE gives the same result as correlation. Unstandardized MSE and random selection are essentially equivalent, random can give better results. If standardization is disabled when generating the composite series in CPS, MSE always yields a better calibration region, but not necessarily a better full reconstruction. Also note there's a bit of a bias in the all proxy composite series, that disappears with standardization disabled. Here's the CSM proxies. Same results as above, except unstandardized MSE generally beats random. So, biased screening yields a biased reconstruction.

By: gerben

gerben — Thu, 21 Jun 2012 12:35:37 +0000

Nick, Your comment is not clear and unambiguous – it is a cheap cop-out. Saying you do not support the use of the proxy does not acknowledge Mann erred. In fact your own link (in the linked piece) starts with “There’s no reason to suppose that Mann did it incorrectly.” Nick, you have never been shy to express an opinion. I even recall threads when you felt comfortable opining on points of US federal and Virginia state law. (As an Australian research scientist!) And yet when it comes to a question undisputedly within your area of expertise, suddenly you suddenly turn reticent. You may feel this has no bearing on your credibility. Others may differ.

By: Nick Stokes

Nick Stokes — Thu, 21 Jun 2012 11:38:30 +0000

gerben, I do not accept your framing of the matter. It is not a requirement of integrity that I should do so. I have given my views at length, and if you want to read them, I suggest you start at the clear unambiguous comment linked above.

By: gerben

gerben — Thu, 21 Jun 2012 11:21:36 +0000

Nick, No-one is asking you to be a spokesman for Mann (though at times you appear to act like one) and it does you no credit to try re-frame the question that way. We are simply requesting that you express a clear, unambiguous opinion on what has been one of the most discussed climate memes in the skeptic blogosphere over the past few years. Consistent with most “mainstream” AGW advocates, your own tribalism will just not let you acknowledge than Mann erred and used Tiljander upside down. I can understand why Mann is trying to avoid embarrassment, but I don’t get why people like Nick are so eager to sacrifice their own integrity in defense of Mann.