I mentioned a couple of days ago that Schweingruber et al  seems to arrive at opposite conclusions to Jacoby and D’Arrigo  as to whether anomalous post-1950 ring widths occur (let alone whether that is due to CO2 fertilization or temperature.) It was interesting to compare Schweingruber-Kienast results at Niwot Ridge. It turns out that Schweingruber has published results (cana060) for Churchill, Manitoba, an important site (cana158) in Jacoby and D’Arrigo  (and several other Jacoby-D’Arrigo publications.) Here’s what it looks like – a typical Jacoby elevated 20th century, but inconsistent with Kienast and Luxmoore or Schweingruber et al 1993.
Figure 1. Jacoby-D’Arrigo chronology for Churchill MB (cana158)
Before showing the results, I’ll mention that I corresponded in early 2004 with D’Arrigo about this data set. MBH98 said that they had carried out certain quality control procedures for tree ring data sets to verify minimum correlations between the measurement data and WDCP crn series. I checked this for over 300 sites and one site that really stuck out as having a low correlation between the measurement and crn series was cana158 (it was about 0.05 by memory, as compared to a MBH minimum of 0.5, again by memory). In addition, the crn series went to 1982, while the measurement data only went to 1978, so there was some inconsistency between the data (as well as evidence that MBH had not carried out the quality control that they said that they had carried out.)
I wrote to D’Arrigo about this inconsistency and she said that the series should be withdrawn (although it’s used over and over). I re-checked a few days ago and the crn series is still at WDCP unamended. Anyway, after noticing the remarkable differences between Keinast and Luxmoore  and Schweingruber et al  on the one hand and Jacoby and D’Arrigo  on the other, I’m now intriguing by any chances for detailed cross-checking. Figure 2 below shows two comparisons of the Jacoby-D’Arrigo chronology for Churchill MB – on the top against my emulation of the chronology calculation using STD methods and archived measurement data; on the bottom against the Schweingruber chronology for a sample in the same area (indeed Jacoby and D’Arrigo use Schweingruber’s MXD results from this sample). Both are materially different from the Jacoby-D’Arrigo chronology, especially in the 20th century.
Figure 1. Jacoby-D’Arrigo chronology for Churchill MB (cana158) Top: black – Jacoby chronology (cana158); blue – std emulation; Bottom – black – Jacoby chronology cana 158; red – Schweingruber chronology cana060.
I’m becoming pretty baffled by what’s going in tree ring world. I checked the identification numbers for the two different data sets. Schweingruber had identification numbers up to 19, but reported only 12 trees (missing 5,12-14, 16-18). He reported 24 cores – 2 consistently for each tree. Jacoby and D’Arrigo had identification numbers up 15, but reported only 9 trees (missing 2, 5-6, 8,11-12). They reported 4 cores for one tree (#7), 3 cores for one tree (#1); showed core id numbers reaching 3 for 2 trees where only 2 cores were reported (#9, #10); reported 2 cores for 3 trees with 2 being the highest core id# (#3, 14, 15) and only one core for 2 trees ( #4, 13). On a previous occasion, I mentioned a remarkable quote from Esper about dendro methodologies:
However as we mentioned earlier on the subject of biological growth populations, this does not mean that one could not improve a chronology by reducing the number of series used if the purpose of removing samples is to enhance a desired signal. The ability to pick and choose which samples to use is an advantage unique to dendroclimatology.
But there must be more going on here – the crn series as archived simply doesn’t match the measurement data. Maybe they’ve got some other measurement data squirreled away somewhere. It would be nice if something in dendro world tied together.