As first fruits of my Mannian CPS emulation, I did a quick sensitivity to see what results looked for the AD800 network without the Tiljander upside-down sediments. I did the run with all proxies except Tiljander sediments as I first cut, since Mannian screening of series that are supposed to be proxies is not a proven method. I’ve also simplified public access to my code quite considerably since yesterday so that it should be relatively easy for someone to experiment.
The top panel shows my emulation of the Mann NH and SH iHAD (land-ocean) reconstructions using the AD800 network (no splicing), together with the Mannian iHad instrumental (I haen’t parsed the relationship of this to HAD and am just using it as is). In the panel below that, I did the same thing using all proxies except the Tiljander sediments. As you see, there is a profound difference particularly in the SH, where the 20th century is not in the slightest anomalous according to this information. Another odd point in the bottom panel version is that the NH 11th century which is believed to be one of the “warm” centers of the MWP emerges, together with the late 17th century LIA, as one of the coldest times of the millennium – something that doesn’t make a whole lot of sense, even for MWP opponents. At present, I don’t know which proxies are leading to this result.
I haven’t been able to replicate Mannian verification statistics calculations. The Mannian “base case” has higher RE and CE statistics than the variation in the bottom panel, but the bottom panel variation is also “99.9% significant” according to the Mannian canon.
The puzzle of deciding between two conflicting reconstructions that are both “99.9% significant” was one that I raised at Climate of the Past Discussions (an interesting point which was ignored by the reviewers, but which remains unresolved.) In likelihood terms (e.g. Brown and Sundberg calibration), I think that the right answer is that one reconstructions would be slightly more “likely” than the other and that the confidence intervals have to be wide enough to encompass both.
Now be careful in using this comparison, as it varies three things – 1) it uses “all” and not just “screened” proxies. Mannian EIV uses “all” proxies, so it’s hardly unreasonable to examine the effect of using “all” proxies under Mannian CPS. 2) it emulates Mannian CPS but without the stupid pet tricks (I realize that this latter term is not very formal, but it’s intended to cover weird programming decisions that probably don’t matter a huge amount in the total scheme of things, but which cannot be justified – sort of like the rain in Spain thing.); 3) the upside-down Tiljander sediments aren’t used. I realize that this is one extra source of variation, but I really can’t stomach doing calculations with upside-down sediments.
Allocating the amount of difference to each thing is something that would be done in an engineering-quality report, something that one would surely expect of the original authors. For now, most of the difference of the difference arises from the use of screened proxies as opposed to all proxies, though I haven’t sorted out what the active ingredients are. I presume that the screening here is another embodiment of the Esper Doctrine, one which makes most statisticians scratch their heads:
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.
I’ve provided code below that would enable interested readers to experiment with their own allocations. The following two lines download a collation of all the relevant Mannian data, including relevant smooths, which don’t need to be re-smoothed over and over again. (This was collated in the script uploaded yesterday, which is a reference.)
# download.file(“http://data.climateaudit.org/data/mann.2008/Basics.tab”,”temp.dat”,mode=”wb”);load(“temp.dat”) #collection of information in utilities
raw.mbh=manniancps(k=11,criterion=passing$whole, outerlist=outerlist.mbh, lat.adjustment= -1, smoothmethod=”mann”,verbose=”default”) ;tsp(raw.mbh)
The control on proxy selection is the parameter criterion which is a logical vector of length 1209 describing the inclusion or exclusion of proxies in a network. The table details.tab is a convenient basis for constructing logical vectors. Mannian program pointlessly creates huge inventories of multiple versions of proxy subsets which are then pointlessly re-smoothed. In fact, all that is needed is to to do the smoothing once and then pick the appropriate subset. nodendro is another logical vector that can be used. Here is code for the all-proxy cps reconstruction (excluding the 4 Tiljander sediments).
raw=manniancps(k=11,criterion=notiljander, outerlist=outerlist.sensible,lat.adjustment= 0, smoothmethod=”sensible”,verbose=”default”)
The plot is done as follows:
title(“CPS iHAD AD800 GL”)