Nic Lewis is best known as the co-author of the O'Donnell paper on Antarctic temperatures, which underwent a famously concerted attempt to stifle it at birth from those on the consensus side of the global warming debate.
Nic's attentions have more recently turned to climate sensitivity, his most notable success being the uncovering of the IPCC's rewriting of the Forster and Gregory results to make them look more alarming - in my view one of the great scientific scandals of our time.
In an new article at Climate Audit he reports on another key IPCC climate sensitivity study - Forest 2006. Although the author refused to provide data and code, Nic has been able to get hold of the data by other means and eventually to persuade Forest to release the code.
Which contains several strange errors, one of which may well turn out to be significant. If so, the knock-on effects are likely to be widespread:
In addition to the Forest 2002 and 2006 papers, I believe these errors also affected the Forest et al. 2008 Tellus A and the Libardoni and Forest 2011 GRL papers, and probably also 2009 and 2010 papers lead authored by Forest’s regular co-author Sokolov. It is to be expected that there will be multiple citations of results from these various studies in the AR5 WG1 report. I put it to Myles Allen – who seems, along with Gabi Hegerl, to be the lead author of Chapter 10 primarily responsible for the sections relating to climate sensitivity – that in view of these serious statistical errors, results from the affected papers should not be cited in the IPCC report. However, whilst accepting that the errors were real, he expressed the view that the existence of these statistical errors didn’t really matter to the results of the papers concerned. His reasoning was that only error (b) had a potentially substantial effect, and that didn’t much matter since there was anyway considerable uncertainty in the ocean data that the studies used. I’m not sure that I agree with this approach.
I would be surprised if the basic statistical errors in the IDL code do not significantly affect the results of some or all of the papers involved. I would like to test this in regard to the Forest 2006 paper, by running the IDL code with the errors corrected, in time to put on record in my “expert reviewer” comments on Chapter 10 of the Second Order Draft of IPCC AR5 WG1 report what the differences in Forest 2006′s results resulting from correcting these errors are, if significant. At least Myles Allen and Gabi Hegerl will then be aware of the size of the differences when deciding whether to ignore them.