Quote from bigdavediode:
Considering how badly he mucked up the first portion of his "paper" the fact that he only flounders this badly is sort of a bonus. Do you want me to keep reading this mess?
Since you're dodging, I'll quote the parts I want you to address.
Mann et al. called their method a âmultiproxyâ technique, since it combined a variety of proxies. The most numerous, and influential, proxies in their data set are tree ring chronologies.
Mann arranged provision of a file which was represented as the one used for MBH98.
discovered a quite a few errors concerning location labels, use of obsolete editions, unexplained truncations of available series, etc.
We showed that when these errors were corrected the famous hockey stick disappeared.
Mann argued that we had studied the wrong data setsetâin other words that the one he provided had mistakes in it and we ought instead to have used one in a newly-identified FTP archive at his university. Over the next month we examined his FTP archive and discovered that, in fact, it corresponded almost exactly to the file we had originally been working with.However it differed in important ways from the description of the data set in the original Nature paper. We supplied a list of these discrepancies to Nature and after their own investigation they ordered a Corrigendum from Mann et al.
PC algorithms choose weights to maximize the explained variance of a group of data series. If one series in the group has a relatively high variance, its weight in the PC1 gets inflated. The Mann algorithm did just this. It would, in effect, look through a data set and identify series with a 20th century trend, then load all the weight on them. In effect it âdata-minesâ for hockey sticks.
In 10,000 repetitions on groups of red noise, we found that a conventional PC algorithm almost never yielded a hockey stick shaped PC1, but the Mann algorithm yielded a pronounced hockey stick-shaped PC1 over 99% of the time.
The Mann algorithm efficiently looks for those kinds of series and flags them for maximum weighting. It concludes that a hockey stick is the dominant pattern even in pure noise.
The result is in the bottom panel of Figure 6 (âCensoredâ). It shows what happens when Mannâs PC algorithm is applied to the NOAMER data after removing 20 bristlecone pine series. Without thesehockey stick shapes to mine for, the Mann method generates a result just like that from a conventional PC algorithm, and shows the dominant pattern is not hockey stick-shaped at all. Without the bristlecone pines the overall MBH98 results would not have a hockey stick shape, instead it would have a pronounced peak in the 15th century.
Of crucial importance here: the data for the bottom panel of Figure 6 is from a folder called CENSORED on Mannâs FTP site. He did this very experiment himself and discovered that the PCs lose their hockey stick shape when the Graybill-Idso series are removed. In so doing he discovered that the hockey stick is not a global pattern, it is driven by a flawed group of US proxies that experts do not consider valid as climate indicators. But he did not disclose this fatal weakness of his results, and it only came to light because of Stephen McIntyreâs laborious efforts.
There's the meat of the argument. He data mined FOR the hockey stick.
Very dishonest.......
