There’s a difference between the underlying proxy data, source code and supporting calculations, and the situation is different for each category.
There is an archive of proxy data located at Mann’s FTP site at the University of Virginia and this is not a current problem area. This data has not “always” been available. The FTP site was started on or about July 30, 2002, about 4 years after publication of MBH98, so it was not available prior to then. The proxy data is presently located at the url and bears a date stamp from 2002.
The FTP site has private areas
For example, the directory presently located at ftp://holocene.evsc.virginia.edu/pub/MANNETAL98 was formerly located at ftp://holocene.evsc.virginia.edu/pub/sdr/temp/nature/MANNETAL98 and was not indexed. If you knew the exact url, you could retrieve it, but not otherwise. When the url was changed to its present location, the date stamp for the directory did not change, so it looks like this directory has been public since December 2003, but it hasn’t been.
(BTW my access to Mann’s FTP site from my computer has been blocked, although I can still get to it from computers at the University of Toronto. This seems a little petty.)
Prior to publication of our first article, there had been no references to this url, even at Mann’s FTP site. I believe that it is quite possible that the directory was re-located - similar to the relocation of the MANNETAL98 directory and was only accessible since Nov 2003. Be that as it may, the proxy data is currently available.
There is source code at Mann’s FTP site for the calculation of tree ring principal components only. There is no source code for the calculation of reconstructed principal components, for the calculation of NH average temperature, for the Preisendorfer-type simulations, etc. etc. We have requested source code and been refused; we have sought intervention from Nature and the U.S. National Science Foundation without success. For the calculations where code is available and a full reconciliation is possible, there were obviously major discrepancies between the procedures as described in Nature and the procedures as actually used. Who would ever have thought that they used an uncentered algorithm on de-centered data? There were also material discrepancies between the series listed as used and the series actually used. Who would have expected this? Mann et al. have provided a vast new Supplementary Information attached to the July 2004 Corrigendum, which Nature has stated to us finally provides a complete and accurate description of their procedures. Since Nature has not obtained the source code and reconciled it, how can they possibly know that the SI is an accurate description. (By the way, the Supplementary Information was not edited by Nature and almost certainly not peer reviewed.)
The supporting calculations that I most want to see are the calculations for the AD1400 step which is in controversy. The only information available on this step is an RE statistic (of 0.51). Nature has refused to provide supporting calculations for the RE statistics. It is significant that the R2 and other verification statistics have not been provided. My calculations indicate that the R2 and other verification statistics are embarrassingly low, which is probably why no one wants to disclose them or to provide the supporting calculations from which they can be conclusively calculated. The attitude of Nature is that an interested party can calculate their own values. This is hardly an adequate response both given the widespread reliance on this study and the prior track record of inaccurate disclosure of both data and methods. I’d like to see the exact calculation and the refusals make me all the more interested.
So while quite a bit of new information has been provided, there’s a lot of material which has not. It should be easy to simply archive the programs. You’d think that it would be easier to archive the source code than to fight about it.