Von Storch and Mann have both said that, in an MBH98-type reconstruction, it is impossible to allocate the impact of individual proxies. This is incorrect as we pointed out in MM05b. My posts on MBH98 Linear Algebra showed this more clearly (or at least in more detail). However, those posts only took the analysis back to the PC series. Since the bristlecones were represented in the PC series, this by itself did not segregate the bristlecone impact, other than indirectly through the PC series, and the connections have not always been as clear to others as they have been to me.
However, since the tree ring PC series are themselves linear combinations of the underlying tree ring networks, with a little more linear algebra, the approach of those posts can be extended to represent the MBH98 NH temperature reconstruction as a linear combination of the individual proxies, which, in turn, enables one to create classes of individual proxies and show the effect of individual proxies
Here I’ve done the calculations so that I obtain the MBH98 temperature reconstruction (working here only with the 15th century proxies) as a linear combination of the 95 individual proxies in the 15th century network. I’ve used 9 classes – by joint continent/proxy type class, distinguishing bristlecones from other North American tree rings. (I’ve grouped Gaspé with the bristlecones, because Mann fiddled with this series to get it into the 15th century network. ) Thus the classes are : Asia tree rings, Australia tree rings, European ice core; Bristlecones (and Gaspé); Greenland ice core; non-bristlecone North American tree rings; South American (Quelccaya) ice core; South American tree rings.
Figure 1 top panel shows the absolute contributions of each continent-proxy class to the MBH98 15th century reconstruction (bristlecones in red.). This vividly shows the noise of the other networks. If I overlaid the final reconstruction on this graphic, it overlaps the bristlecone contribution almost exactly. The bottom panel of Figure 1 shows all 9 series in a standardized format of the spaghetti graphs. What the Mann weighting system does is to pick out the bristlecones from the noise (by enhancing their weights). On another occasion, I’ll do a similar graphic without the bristlecones (which is the supposed "MM reconstruction").
You can see quite easily how by enhancing the weight of the bristlecones and reducing the weight of all the other proxies, you can “get” a hockey stick. You have to work pretty hard to “find” the bristlecones out of this pig’s breakfast of noise; that was Mann’s “new” statistical method. If you take the bristlecones out of this system, there is no HS.
Figure: Spaghetti graph showing top- absolute contribution to MBH98 reconstruction (1400-1980 for AD1400 step proxies) by the following groups: Asian tree rings; Australia tree rings; European ice core; Bristlecones (and Gaspé); Greenland ice core; non-bristlecone North American tree rings; South American ice core; South American tree rings. Bottom – all 9 contributors standardized.