date: Mon Feb 23 15:06:46 2009 from: Phil Jones subject: Re: Fwd: pre-review Arctic 2k reconstruction to: Ray Bradley Ray, Had a quick look and weak on statistics isn't the half of it! The tree-ring stuff needs to mention RCS - otherwise you might as well drop the trees! There needs to be a column on how they were standardized. The Yamal chronology in this paper has no low frequency - the way it is standardized loses it. The paper says so - and it is obvious if you look. What you should be referencing is a paper of Keith's from Phil Trans in 2008. He standardized the long Russian series with a consistent RCS approach. Nauzbaev and Vaganov know how to do this as well, but their 2000 paper is an odd one to use. Use their one from the Holocene in 2002. Keith told me that Grudd 2008 got it wrong as well. Also whilst we're on trees, if I was a skeptic I'd get fed up with people referencing Mann et al (2008) for some North American tree sites. This is a red rag to a bull. Again they should be to original sources and should say how they are standardized. Finally, I've calculated numerous DW statistics in my time. I've never got one approaching 3.9. According to wikipedia it is possible (range is 0 to 4). However, what you're supposed to do with the values above 2 is to subtract them from 4. So this one should be 0.1. What it then means is that there is very, very, very, very high negative autocorrelation (because of the subtraction). It doesn't look as though there is, so I think the calculation is screwed! I think it does stink, but they just need to write a paper with more details! The ice core interpretation depends on how the diffusion is allowed for - may not make much difference on this timescale. Also - they don't need all the ADs. They need to go before dates, but they aren't needed! Cheers Phil At 20:11 21/02/2009, Ray Bradley wrote: Hi Phil, If you have a moment to scan through this & give us some feedback...it would be appreciated. As you will see there are some statistical weaknesses....! But I think you will find it of interest. Darrell Kaufman just wrote : " Ray says that you'd tell us whether it stinks. To lay it bare, we're focusing on 20-year means, and our calibration period is only 100 years, so n = 5. The standard error of the regression is ± 0.04°C, and the Durbin- Watson statistic, d = 3.9, indicating that autocorrelation is not significant. On the other hand, we can calculate annual proxy values for subset of 11 records that are resolved annually to show that the relation between proxy and instrumental temperature is strong (Fig 2 in the attached pdf). ". Thank you in advance for your suggestions. Darrell Darrell S. Kaufman Professor of Geology and Environmental Sciences Northern Arizona University 928-523-7192 [1]http://jan.ucc.nau.edu/~dsk5/ Raymond S. Bradley Distinguished Professor Director, Climate System Research Center* Department of Geosciences, University of Massachusetts Morrill Science Center 611 North Pleasant Street AMHERST, MA 01003-9297 Tel: 413-545-2120 Fax: 413-545-1200 *Climate System Research Center: 413-545-0659 < [2]http://www.paleoclimate.org> Paleoclimatology Book Web Site: [3]http://www.geo.umass.edu/climate/paleo/html Publications (download .pdf files): [4]http://www.geo.umass.edu/faculty/bradley/bradleypub.html Please don't print this e-mail unless you really need to! * Prof. Phil Jones Climatic Research Unit Telephone +44 (0) 1603 592090 School of Environmental Sciences Fax +44 (0) 1603 507784 University of East Anglia Norwich Email p.jones@uea.ac.uk NR4 7TJ UK ----------------------------------------------------------------------------