In the comments to the earlier thread, Nic Lewis left this comment about what happened when he discovered that the IPCC had altered the Forster and Gregory climate sensitivity findings. I thought it striking enough to warrant a posting of its own.
A recap for those unfamiliar with the story. My complaint about the alteration of the Forster & Gregory 2006 results was rejected on the grounds that it was done to put all the climate sensitivity probability density graphs on the same, uniform prior in sensitivity, basis. Justifying changing a result from a correct to an incorrect basis on the grounds that all the other results were given on that basis seems very dubious to me. But I knew that at least one of the other studies, Gregory 2002, actually had its results shown on the same basis as the original Forster & Gregory 2006 results, being a uniform prior in the climate feedback parameter - that is, a prior inversely proportional to the square of sensitivity. So my letter to Gabi Hegerl complained that the statement that the Gregory 2002 results were stated on a uniform prior in sensitivity basis was incorrect.
Gabi Hegerl, quite properly, brought my letter to the attention of the IPCC WG1 Co-Chairs, and it was dealt with under the new formal "IPCC protocol for addressing possible errors". The result was the issue of a formal Erratum by the IPCC, stating that Gregory et al "implicitly use a uniform prior on transient climate response". I knew that this was also wrong, but Gabi insisted that the WG1 authors were sure it was right. In fact, Gabi was relying on Myles Allen, who I think was primarily responsible for the use of a uniform prior in sensitivity basis in Chapter 9 of AR4 WG1.
It took me several months, with the help of another climate scientist, to find out why Myles Allen thought that Gregory et al "implicitly use a uniform prior on transient climate response" and then ultimately to persuade him, and thus Gabi Hegerl, that this statement also was incorrect - and that I had been right all along in saying that in fact this study implicitly used a nearly uniform prior in the climate feedback parameter.
Gabi and Myles were not keen to get the IPCC to issue a further Erratum, which would obviously be embarrassing, so I agreed not to pursue the matter further.