date: Wed Jun 18 12:33:52 2003 from: Keith Briffa subject: Re: Sceptics' discourse to: Timothy Carter Hi Tim ]just back from couple of days in Brussels - will look at this when have time . Cheers Keith At 09:57 AM 6/18/03 +0300, you wrote: Dear Phil/Keith, It was good to see you both last week. I am copying you the English language part of an email I just received from a local sceptic (a lawyer with no climate training at all!) which refers to some of your work. I usually dispose of these mails as they come in, but this one seems to be calling into question some published science. McIntyre is probably well known to you, but just in case here it is. Sorry, but the figures referred to in this mail did not get through our firewall. Best regards, Tim From: [1]Steve McIntyre To: [2]Climate Sceptics Sent: Sunday, June 15, 2003 9:27 PM Subject: [Climate Sceptics] More on Mann and Jones Datasets - Fennoscandia Dear all, More on the underlying datasets in the millenial datasets of Mann; Jones etc. One of the prominent data compilation datasets is Fennoscandia, used in both Bradley-Jones 1992 and Mann 1998, derived from Briffa et al. In fact, Briffa makes several essays at temperature reconstruction for northern Fennoscandia. There seem to be three main variants: (1) BETA1 is reported in Briffa et al 1990 (Nature) and is based on cubic splines; (2) a RCS version, both uncorrected and corrected , is reported in Climate Dynamics 7 (1992), where it is compared to the cubic spline version in a useful way (clearly showing the inappropriateness of cubic splines for long-term data analysis). Figure 8 in Clim Dyn 7 matches Fig 2(2) in Bradley-Jones 1992 and my graph produced from the Mann 1998 proxy 67 which all seem therefore to be the same dataset. (3) a third reconstruction is reported on Fennoscandia by Briffa and Schweingruber in Climate since 1500AD (1992) data on which is at [3]www.ngdc.noaa.gov. In C1500, Briffa and Schweingruber do not reconcile to the prior discussions. I have graphed this dataset together with the other one below. The correlation between the two datasets for the overlapping period 1587-1975 is 0.032 an interestingly low correlation for what are reconstructions produced from relate data. I have shown the two The Climate Dynamics 7 reconstruction contains a fudge by Briffa et al, described as follows: The density chronology shows a low-frequency decline over the last century which appears anomalous in comparison with both the TRW data and the instrumental data over the 19^th and 20^th centuries. These facts suggest that the density-coefficients in the regression equation may be biased as would be the case if the density decline were not climate related (CO2 increases and/or the potential effects of increasing nitrogen input from remote sources may be implicated here.) &The residual MXD data (actual estimated) are plotted in Fig. 7. A systematic decline is apparent after 1750. By fitting a straight line through these residuals (1750-1980) and adding the straight-line values (with the4 sign reversed) to the RCS density curve, the anomalous post-1750 decline was removed. This corrected RCS curve was then used along with the RCS ring-width curve in a final reconstruction of the April-August temperatures. This hardly seems like justifiable statistical procedure.Without the fudge, the "reconstruction" shows declining temperatures in the 20th century. A very similar decline in residuals occurs from 1100 to 1250 and one wonders whether a similar adjustment would be allowable then. The Climate Dynamics article does not contain a description of the regression methodology and I have not yet consulted the predecessor article describing the regressions. Suffice it to say that the tree ring data is highly autocorrelated, as is (to a lesser extent) the temperature data. The meaning of such correlations is not clear. The reconstructions end up being a weighted sum of the tree ring widths over two summers and MXD s over two summers. The coefficients are very unstable under different reconstruction methodologies. Regards, Steve McIntyre -- Professor Keith Briffa, Climatic Research Unit University of East Anglia Norwich, NR4 7TJ, U.K. Phone: +44-1603-593909 Fax: +44-1603-507784 [4]http://www.cru.uea.ac.uk/cru/people/briffa[5]/