This is not going to be an especially interesting post for most (probably any) of you, but I want to document a couple of points mostly as an aide-memoire for myself so I don’t forget.
I actually learned something new about the Jones et al reconstruction from the Euro Team study. I’ve been able to sort of replicate the Jones study, but not to anything like adequate precision. Jones did not archive data as used, but did publish diagrams of the data and I used digital versions cobbled together elsewhere – mostly from MBH. Of the 17 proxies in the "independent" Jones study, 14 were used in MBH. After trying diligently, I asked Jones to provide me with the data as used and code. He refused. THe Euro Team has posted up digital versions of 5 Jones series, 4 of which were identical to the Mann versions. However, their Greenland version was somewhat different. It had a high correlation (0.75) but differed in detail. I’ve gone back and traced Mann’s version to Fisher’s veries DELNORM6.CVG, which is his "super-stack", including sites: Crete, A, B, C, D, H, Milcent, GISP2 and 4 GRID series, which I haven’t been able to identify.
The Jones version has a high correlation to a scaled composite of Crete, A,B, C, D, H and Milcent, but I couldn’t locate a precise equivalent in a detailed data set sent to me by Fisher, the author of the series.
Hegerl also uses a "decadally smoothed" version of this series, which is archived by the Euro Team (but not by herself.) She doesn’t state what the decadally smoothing is. I experimented with various gaussian filters, which are common in Team studies and got close but not exact. Eventually I determined that she used an 11-year running average. This filter applied to the Mann version yielded the Hegerl version – which was cut off in 1960 (though the original goes to 1983). Here is a plot of the 3 versions in the 20th century.
Figure 1. Three versions of West Greenland dO18.
As an experiment, I plotted up the data from the 7 cores which are said to be in the Crete stack, shown below. A couple of cores have values in 1984, which was not included in the composite. However the 1984 dO18 values appear to be the lowest values in the duration of the record (which starts in 553)
Figure 2. Twentieth Century Values of 7 Ice Cores in Crete, Greenland Area
As a reminder, here is a plot of the values over the entire series. This is remarkable for the uniformity of values. Fisher’s thoughts on this were that the sites were on a high plateau and were relatively unaffected by centennial changes in temperature.
Figure 3. Three Versions of West Greenland dO18