On April 10, I was notified by NOAA that a little bit of data from Trouet was now online at NOAA WDCP. The archive is the absolute minimum; even Science would require them to archive this data if asked.
However, it is totally inadequate for replication.
However, every little bit of data helps and here’s a little progress report. It’s too bad that Esper the non-Archiver has taken an anti-archiving stance as the underlying idea of comparing the Scotland and Morocco proxies is fairly interesting. I’m still trying to understand why the authors regard this information as rebutting the MWP idea, as the proxies themselves seem to show a rather pronounced MWP/MCA.
First, the new data permits a more complete emulation of Trouet Figure S1, now that the Esper PDSI recon is available. For reference, below is the original Figure S1 with original caption.
Trouet Figure S1 Original Caption: Long-term winter proxy records from Europe. Comparison of the tree-ring based Morocco (S2) and speleothem based Scotland (S1) records with a documentary based estimate of September-June England-Wales precipitation (S10) and speleothem based estimate of winter temperature from the central Alps (S13) (A). Time series consist of 25-year averages, standardized over the common period (1075-1925). The Morocco PDSI record was inverted.
Next, here is my emulation of their Figure S1 using the speleothem version said by Andy Baker to be correct; the newly archived Esper PDSI information; my manual transcription of data from Lamb 1965; and archived Mangini information. In each case, I’ve used 50-year averages and then scaled the resulting series over 1075-1925 as in the Trouet caption, orienting the series to match the Trouet figure. As noted previously, 50-year averages match. Three of four emulations match very closely: the oddball is the Scotland speleothem, where, as noted before, Trouet has almost certainly used the detrended version, said by Andy Baker to be an incorrect version. (Andy Baker said that Trouet used the non-detrended version but I don’t think that his understanding is correct; I’ve emailed him about this.)
Figure 2. My emulation of Trouet Figure S1.
Moving along a little, here is Trouet Figure 1 from the main article. The term “30-year cubic spline” may not be familiar to statisticians and scientists from Off the Island; I think that I can explain what this means in Team dialect and will do so if necessary. Note that the two series are oriented oppositely in this plot (while the MWP has a common orientation in SI Figure 1.)
Original Caption to Trouet Fig. 1. Proxy-derived long-term NAO reconstruction. (Top) Reconstructed winter precipitation for Scotland and February-to-June Palmer Drought Severity Index (29) for Morocco. Records were normalized over the common period (1049–1995) and smoothed with the use of a 30-year cubic spline. (Bottom) Winter NAO reconstruction NAOms (black curve) is the difference of the Scotland and Morocco records. The gray area is the estimated uncertainty; yellow and red areas are the 10 and 33% highest and lowest values since 1700. The blue line represents the 30-year smoothed Lisbon-Iceland instrumental NAO index series (11).
Most CA readers hate all the smoothing of data that’s infected so many Team articles and presentations, including Trouet et al. For comparison, in the next figure, I’ve plotted raw versions of the two series in question – the Esper PDSI recon (however it was made) and the Baker non-detrended speleo, said to the preferred version, though, as noted above, unlikely to be the version used in Trouet.
Examining the “raw” versions of the data, here are my first few comments.
1. The “correct” non-detrended Scottish speleo data – whatever it shows – definitely shows a “warm” MWP on the scale of the late 20th century. The ability of the proxy to measure warm climates looks severely limited by the fact that it has a zero minimum and is bumping against the zero minimum in the MWP.
2. The eye can certainly be teased into comparing the two series. And in fairness to this perception, both series had been postulated to be connected to the NAO in independent articles (Proctor et al 2000, 2002) and Esper et al 2007, before the present joint venture article. IF both series are NAO proxies, then the big downspikes should align. Given the precision of tree ring dating, I think that there would be an excellent case for using the tree ring data to align the speleo data with its much looser dating control. I’m not exactly sure how one would express this methodology in objective statistical terms, but intuitively it makes sense to me. Perhaps Roman or UC or Hu have ideas on this.
3. Esper’s PDSI reconstruction has all sorts of ad hoc splicing, selecting and re-scaling, but it’s not possible analyse its impact without the Esper measurement data, which is under lock and key.