Mann told Antonio Regalado of the Wall Street Journal that he would not be “intimidated” into releasing source code for MBH98.
Here is an account of correspondence with Mann and with the U.S. National Science Foundation:
Even before publication of MM03, we politely requested clarification on issues in MBH98. This was a source of controversy in late 2003. Here is a record of correspondence with Mann which we made available some time ago.
After publication of MM03, Mann argued that MM03 contained an incorrect implementation of a stepwise principal components procedure (which was not documented in MBH98) . Details of this procedure have continued to drift in, with the first listing of the number of PC series retained in each calculation step/tree ring network combination provided in the July 2004 Corrigendum SI. This listing was inconsistent with prior information.
In August 2004, through Nature, we became aware privately of claims that a variation of Preisendorfer’s Rule N had been used to determine the number of retained PC series. This claim was published in November 2004. (We have not been able to verify actual application of this criterion, as actual numbers are impossible to replicate. See Was Preisendorfer’s Rule N Used?
In any event, immediately after we learned of the previously undocumented stepwise procedure, we asked to inspect MBH98 source code so that we can completely reconcile results and avoid this type of dispute. Attached is our correspondence after MM03, which obviously cannot be construed as a form of “intimidation”, but as an entirely proper request.
Subsequently, we located some Fortran code at Mann’s FTP site for the calculation of tree ring principal components. Although this code is only a very small fraction of the total code, it contains a procedure which was materially misrepresented in MBH98 and which additionally is not statistically valid. We reported on this in MM05 (GRL) and MM05(EE).
As I’ve pointed out in various postings on Replication, it is impossible on the present record to replicate important steps in other parts of MBH98.
After our unsuccessful attempts at obtaining source code, we asked the U.S. National Science Foundation for assistance. This was also unsuccessful. The correspondence is here.
We also made attempts with Nature and I’ll get to describing this on another day.