Rush Limbaugh says the climate scientists should be 'drawn and quartered'. Glenn Beck touts stolen emails as evidence for a 'scam,' and the Moonie Times says, well who the hell cares. The Moonies are down to 45,000 uber-wingnut subscribers. Last week we explained the story behind one of the stolen emails. Paleo-climatologist Micheal Mann of Realclimate, who was intimately involved in the issue discussed in some of the emails in question, was kind enough to take time out of his holiday week to provide further clarification.

DS: When Phil Jones wrote in 1999, "I've just completed Mike's Nature trick of adding in the real temps to each series for the last 20 years (i. e. from 1981 onwards) and from 1961 for Keith's to hide the decline," what did he mean?

Michael Mann: Phil Jones has publicly gone on record indicating that he was using the term "trick" in the sense often used by people, as in "bag of tricks", or "a trick to solving this problem ...", or "trick of the trade". In referring to our 1998 Nature article, he was pointing out simply the following: our proxy record ended in 1980 (when the proxy data set we were using terminates) so, it didn't include the warming of the past two decades. In our Nature article we therefore also showed the post-1980 instrumental data that was then available through 1995, so that the reconstruction could be viewed in the context of recent instrumental temperatures. The separate curves for the reconstructed temperature series and for the instrumental data were clearly labeled.

The reference to "hide the decline" is referring to work that I am not directly associated with, but instead work by Keith Briffa and colleagues. The "decline" refers to a well-known decline in the response of only a certain type of tree-ring data (high-latitude tree-ring density measurements collected by Briffa and colleagues) to temperatures after about 1960. In their original article in Nature in 1998, Briffa and colleagues are very clear that the post-1960 data in their tree-ring dataset should not be used in reconstructing temperatures due to a problem known as the "divergence problem" where their tree-ring data decline in their response to warming temperatures after about 1960. "Hide" was therefore a poor word choice, since the existence of this decline, and the reason not to use the post 1960 data because of it, was not only known, but was indeed the point emphasized in the original Briffa et al Nature article. There is a summary of that article available on this NOAA site.

There have been many articles since then trying to understand the reason for this problem, which applies largely to only one very specific type of proxy data (tree-ring wood density data from higher latitudes).

As for my research in this area more generally, there was a study commissioned by the National Academies of Science back in 2006 to assess the validity of paleoclimate reconstructions in general, and my own work in specific. A summary of that report, and link to it, is available here. And the New York Times (6/22/06), in an article about the report entitled "Science Panel Backs Study on Warming Climate" had the following things to say:

A controversial paper asserting that recent warming in the Northern Hemisphere was probably unrivaled for 1,000 years was endorsed today, with a few reservations, by a panel convened by the nation's preeminent scientific body...At a news conference at the headquarters of the National Academies, several members of the panel reviewing the study said they saw no sign that its authors had intentionally chosen data sets or methods to get a desired result. "I saw nothing that spoke to me of any manipulation," said one member, Peter Bloomfield, a statistics professor at North Carolina State University. He added that his impression was the study was "an honest attempt to construct a data analysis procedure."

DS: You wrote, "Perhaps we'll do a simple update to the Yamal post. As we all know, this isn't about truth at all, its about plausibly deniable accusations," what's the story there?

MM: This refers to a particular tree-ring reconstruction of Keith Briffa’s. These tree-ring data are just one of numerous tree-ring records used to reconstruct past climate. Briffa and collaborators were criticized (unfairly in the view of many of my colleagues and me) by a contrarian climate change website based on what we felt to be a misrepresentation of their work. A further discussion can be found on the site "RealClimate.org" that I co-founded and help run. It is quite clear from the context of my comments that what I was saying was that the attacks against Briffa and colleagues were not about truth but instead about making plausibly deniable accusations against him and his colleagues.

We attempted to correct the misrepresentations of Keith's work in the "RealClimate article mentioned above, and we invited him and his co-author Tim Osborn to participate actively in responding to any issues raised in the comment thread of the article which he did.

DS: Phil Jones again wrote "Can you delete any emails you may have had with Keith re AR4? Keith will do likewise. He's not in at the moment -minor family crisis. Can you also email Gene and get him to do the same? I don't have his new email address. We will be getting Caspar to do likewise."

MM: This was simply an email that was sent to me, and can in no way be taken to indicate approval of, let alone compliance with, the request. I did not delete any such email correspondences.

DS: You wrote, "I think we have to stop considering Climate Research as a legitimate peer-reviewed journal. Perhaps we should encourage our colleagues in the climate research community to no longer submit to, or cite papers in, this journal"?

MM: This comment was in response to a very specific incident regarding a paper by Soon and Baliunas published in the journal "Climate Research". An editor of the journal, with rather contrarian views on climate change, appeared to several of us to be gaming the system to let through papers that clearly did not meet the standards of quality for the journal. The chief editor (Hans von Storch), and half of the editorial board, resigned in protest of the publication of the paper, after the publisher refused to allow von Storch the opportunity to write an editorial about how the peer review process had failed in this instance.

Please see e.g. this post at RealClimate. Especially the 3rd bullet item -- see the various links, which lead to letters from chief editor Von Storch, and an article by the journalist Chris Mooney about the incident.

Scientists all choose journals in which we publish and we all recommend to each other and our students which journals they should publish in. People are free to publish wherever they can and are free to recommend some journals over others. For an example of this behavior in daily life, people make choices and recommendations all the time in their purchasing habits. It is highly unusual for a chief editor and half of an editorial board to resign and that indicates a journal in turmoil that should possibly be avoided. Similarly, authors are allowed to cite any papers they want, although usually the editor will note incorrect or insufficient citing.

I support the publication of "skeptical" papers that meet the basic standards of scientific quality and merit. I myself have published scientific work that has been considered by some as representing a skeptical point of view on matters relating to climate change (for example, my work demonstrating the importance of natural oscillations of the climate on multidecadal timescales). Skepticism in the truest scientific sense of the word is good and is indeed essential to science. Skepticism should not be confused, however, with contrarianism that does not meet the basic standards of scientific inquiry.

DS: "It would be nice to try to contain the putative "MWP".

MM: In this email, I was discussing the importance of extending paleoclimate reconstructions far enough back in time that we could determine the onset and duration of the putative "Medieval Warm Period". Since this describes an interval in time, it has to have both a beginning and end. But reconstructions that only go back 1000 years, as most reconstructions did at the time, didn't reach far enough back to isolate the beginning of this period, i.e. they are not long enough to "contain" the interval in question. In more recent work, such as the IPCC Fourth Assessment Report published in 2007, the paleoclimate reconstructions stretch nearly 2000 years back in time, which is indeed far enough back in time to "contain" or "isolate" this period in time.