John Mitchell’s Review Comments
IPCC policies state that their process is supposed to be open and transparent and that all comments are to be archived. Previously, we observed that the Lead Author Responses to our Review Comments were completely unresponsive on key issues. Under IPCC policies, the Review Editor is charged with seeing that this doesn’t happen. John Mitchell of Hadley Center was Review Editor of chapter 6. Despite policies to the contrary, the IPCC refused to provide complete comments by Mitchell and other Review Editors, providing only their sing-off statements.
David Holland attempted to obtain Mitchell’s review. These were refused on a variety of pretexts: first, that they had been destroyed; when that didn’t work, on the grounds that Mitchell had acted in a “personal” capacity; when that didn’t work (due to the fact that David Holland requested FOI information on who paid for his travel to IPCC meetings, they adopted the strategy referred to by Phil Jones – that IPCC was an international organization and that responding to FOI would interfere with UK relations with an international organization.
Ross McKitrick wrote me reporting that Mitchell made some on-point comments about the Hockey Stick issue. Mitchell’s comments could have been made by a CA reader. For example:
Is the PCA approach robust? Are the results statistically significant? It seems to me that in the case of MBH the answer in each is no
From John Mitchell to Jansen and Overpeck
I am in Geneva at the WMO EC meeting,so I have not had a lot of time to look at the SOD comments. I can not get to Bergen before Tuesday. I had a quick look at the
comments on the hockey stick and include below the questions I think need to be addressed which I hope will help the discussions. I do tbelieve we need a clear answer to the skeptics . I have also copied these comments to Jean. Please let me know that you have received this, and what email address I can contact you at in Bergen¨.
With best wishes
1. There needs to be a clear statement of why the instrumental and proxy data are shown on the same graph. The issue of why we dont show the proxy data for the last few decades ( they dont show continued warming) but assume that they are valid for early warm periods needs to be explained.
2 . There are number of methodological issues which need a clear response. There are two aspects to this. First , in relation to the TAR and MBA which seems to be the obsession of certain reviewers. Secondly (and this I believe this is the main priority for us) in relation to conclusions we make in the chapter We should make it clear where
our comments apply to only MBH (if that is appropriate) , and where they apply to the overall findings of the chapter. Our response should consider all the issues for both MBH and the overall chapter conclusions
a. The role of bristlecone pine data: Is it reliable? Is it necessary to include this data to arrive at the conclusion that recent warmth is unprecedented?
b. Is the PCA approach robust? Are the results statistically significant? It seems to me that in the case of MBH the answer in each is no. It is not clear
how robust and significant the more recent approaches are.
3. The chapter notes that new data has been included, but we dont say how much or is this is substantial or minor. The impression I have that the amount added is
minor, but I cant tell.
4. The Esper et al and Moburg et al data both show increased variance, but the temporal patterns are quite different. We need to say why the discrepancy does
not undermine our conclusions of greater cooling in the Little Ice Age.
5. I have not had time to check the original chapter, but the comments give the impression that the recent 50 yr warming is unprecedented over the last 500years (seems reasonable) and elsewhere over the last 1000years (less clear)
John FB Mitchell