[Climate Audit was started on Jan 31, 2005. Prior to its startup I had some notes at a prior website http://www.climate2003.com, which John A transferred to the CA blog at its start-up.]
If 2 PCs are used in the AD1400 North American network along with conventional (centered) PC calculations, we argued in our Nature submissions that MM-type results are obtained. This is now effectively acknowledged by MBH. To try to salvage MBH98, they now argue that they should be entitled to increase the number of PCs in the AD1400 North American network from 2 to 5 and that our not doing so is “incorrect”. They point out that, using centered PC methods, the PC4 (instead of the PC1) has a hockey stick shape (from the bristlecone pines) and, as long as they can use the PC4, the PC4 now drives world climate history. Doesn’t this just seem silly? Now we’re not dealing with a “dominant” pattern of world climate, but a PC4. ROTFLOL.
Secondly, I defy anyone to show me how the actual retention of PC series in MBH98 can be derived from the Preisendorfer criteria now said to be used in MBH98 for tree ring networks (although MBH98 itself only talked about spatial distributions for tree ring PC retention). Below are two plots made on the same basis as the plot shown at Mann’s blog for the AD1400 North American network – only here for the AD1600 Vaganov and AD Stahle/SWM networks. In the first case, MBH98 retained 2 PCS and in the second case, MBH98 retained 9 PC series. I do not believe that there is any rational policy here. I sure can’t see how the actual retention can be linked to Preisendorfer. It would be helpful to see some source code here. Maybe there’s something weird and inconceivable like their centering method.
Thirdly, what does this do to their claims of robustness? A robust reconstruction obviously should not stand or fall on whether 2 or 5 PCs are used in the AD1400 North American network – but this is exactly what Mann et al. are saying. Remember all the grandiose claims about MBH98 being robust to the presence or absence of dendroclimatic indicators altogether (see both MBH98 and Mann et al.). Now it seems that MBH98 is not even robust to the presence or absence of a PC4. Also remember that Mann et al. have known about the lack of robustness to the bristlecones for a long time – look at the PC1 in the BACKTO_1400-CENSORED directory. It’s almost exactly the same as ours. Maybe someone can explain to me how you can claim robustness after doing the CENSORED calculations.
In the figures above, lines are from Preisendorfer-type simulations using AR1 coefficients. Red is using centered calculations; black is MBH98 method, showing both the archived value and our emulation. (I did these calculations a few months ago; I haven’t reconciled why the emulation differs from the archived value in the Vaganov AD1600 network, but the discrepancy is not large and is non-existent in the Stahle/SWM network. Again riddle me this: why does the AD1600 Vaganov network have 2 PCs and the AD1700 Stahle/SWM network have 9 PCs?