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Climate Change

Judge Strikes All of Michael Mann's Expert Witnesses from Libel Suit

A week after granting summary judgment for another defendant (CEI), the judge rejects all but one of the proffered experts.


Climatologist Michael Mann suffered another setback yesterday in the defamation lawsuit over critical blog posts published by the Competitive Enterprise Institute and National Review. Last week, the D.C. court granted summary judgment for CEI, leaving writers Rand Simberg and Mark Steyn as the only defendants left. (National Review had previously been dismissed from the case.)

In a 55-page order, Judge Irving excluded all but one of the expert witnesses offered by each side in the case. Judge Irving struck all seven of the expert witnesses offered by plaintiff Mann and one of the two expert witnesses offered on behalf of the defendants. Only one expert witness offered by the defendants, Dr. Abraham Wyner, an expert on statistical methods, was not excluded by the order.

Here is how Judge Irving set the stage:

Importantly, this is a defamation action arising out of two blog posts written individually by Defendants Steyn and Simberg. The litigation does not intend to answer any questions about the existence of climate change or global warming. The subject statements concerned and criticized Dr. Mann ("Plaintiff") personally for his work in producing a model of rising global temperatures, which model is known publicly as the Hockey Stick graph. The statements accused Plaintiff, inter alia, of "molest[ing] and tortur[ing] data in the service of politicized science[,]" "engaging in data manipulation[,]" and creating the "fraudulent climate-change 'hockey-stick' graph[.]" Competitive Enter. Inst. v. Mann, 150 A.3d 1213, 1262-64 (D.C. 2016), as amended (Dec. 13, 2018), cert denied 140 S. Ct. 344 (2019). Plaintiff claims that the statements are defamatory and false. Defendants, on the other hand, contend the statements are not defamatory and are, indeed, true. Defendants seek to offer the testimony of two experts in the field of climate science and statistics, to lend to the credence and the legitimacy of the allegedly defamatory statements. For his part, Plaintiff proffers seven experts to support his claim that the statements are defamatory. The question for the Court is whether it may, as gatekeeper, admit into evidence the witnesses' opinion testimony and, if so, whether the subject matter of the testimony should be limited in any fashion.

Applying Rule 702 of the Federal Rules of Evidence, and the Daubert standard for scientific evidence, Judge Irving concluded that most of the proffered expert testimony was inadmissable because the experts failed to identify the methodology they used in reaching their conclusions about the contested statements. As Judge Irving explained:

none of Plaintiff's proffered experts explain the methodologies that they used to formulate the opinions contained in their reports. This error, in and of itself, is fatal because the Court is rendered unable to determine whether the Parties' experts used reliable methodologies. . . .   [A]s gatekeeper, the Court cannot allow an expert to testify concerning documents and articles that they have reviewed, unless the expert can establish that they have used some technique or methodology that systematically gathers, organizes and catalogs the documents such that another expert with similar training could follow the same procedure and arrive at the same result. . . .

The methodologies of the expert must be grounded in the scientific method, such that another person with similar expertise could replicate them. See Daubert 509 U.S. at 591. Reviewing a selection of documents, summarizing them, and giving an opinion about their conclusions is not a proper methodology grounded in the scientific method, but, unfortunately, it is precisely the methodology used by most of the proffered experts, here. For that reason, the Court is constrained to grant all of the subject motions and exclude all of the proffered expert testimony, with the exception of Dr. Wyner's expert testimony.

So, for example, here is a portion of Judge Irving's discussion of why he found the proffered testimony of Dr. Naomi Oreskes wanting:

When asked about the methodologies that she used in this case, Dr. Oreskes responded: "If you want me to tell you what my method is, it's reading and thinking. We read. We read documents. And we think about them."

That is the problem, here. Reading and thinking about documents are not the types of "reliable methodologies" typical of an expert witness, which leaves the Court unable to distinguish why Dr. Oreskes is more capable than the average juror, who can also read and think about documents. See Parsi v. Daioleslam, 852 F. Supp. 2d 82, 89 (D.D.C. 2012) (rejecting an expert opinion based solely on the experts "reading and viewing" and finding that reading, alone, does not constitute an acceptable methodology). Dr. Oreskes "reading and thinking" have not been peer-reviewed, have no known success rate, and cannot be replicated by other experts in her field. . . . Dr. Oreskes opinion is not derived from the scientific method and is more aptly described as a historical narrative or research compilation than scientific testimony. See Daubert, 509 U.S. at 590; Meister, 267 F. 3d at 1127 (finding that to identify scientific testimony, "forces the court to focus on principles and methodology, not on the conclusions they generate, and thus demands a grounding in the methods and procedures of science, rather than subjective belief or unsupported speculation.") (internal citations omitted.)

On the other hand, Judge Irving found Dr. Wyner's proffered testimony on statistical methods to meet the applicable standards.

In sharp contrast with the reports of the other experts that the Parties have proffered, Dr. Wyner's report offers substantial analysis and explanation of the scientific principles and methods he employed in forming his opinion. Dr. Wyner, a trained and recognized statistician, explains there are "aspects of Dr. Mann's work that can reasonably be construed as manipulative, if not in intent than in effect, as the word is used in common parlance." Wyner Rep. ¶ 9. Plaintiff argues that Dr. Wyner's opinion is "little different than the Curry opinion expressed in her report." MIL Curry Mem. 9. A comparison of the two reports controverts this theory. Dr. Curry seeks to offer a review of criticisms of the Hockey Stick and excerpts of the polemic surrounding the graph, all to support her expert opinion that it would be reasonable to call it fraudulent. Dr. Wyner, in contrast, offers detailed analysis of the statistical methods used to construct the Hockey Stick graph, and why the methods may be reliable and, thus, tending to support a basis for Defendants' statements.

For example, Dr. Wyner states that "constructed random sequences, simulated like playing cards drawn from a deck, are no less skillful for reconstructing temperatures than naturally occurring proxies." Wyner Rep. ¶ 33. He explains in detail how he applied "crossvalidation," which is "an effective method of exploring and countering overfitting and measuring model reliability accurately." Wyner Rep. ¶ 38 n.13. Plaintiff does not, and likely cannot, assail the principles and methods that Dr. Wyner applies. His opinion is plainly beyond the ken of the average juror, and his testimony regarding the reliability of the Hockey Stick graph will be useful in aiding the jury's determination of actual malice and falsity.

The court's order does not necessarily mean that all other expert testimony will be excluded. Judge Irving noted his "expectation that the Parties will likely attempt to elaborate on the methodologies that their experts used in subsequent pleadings," but for now, the order stands as another blow against Dr. Mann's case, nine years after the suit was first filed.

Finally, as I noted in my last post on this litigation:

DISCLOSURE: As I've noted in prior posts on this case, I am a contributing editor at National Review Online, which means I have a fancier byline when I submit articles to the publication and occasionally contribute to The Corner and Bench Memos. It is not a salaried position. I also worked at the Competitive Enterprise Institute from 1991 to 2000 — many years before the events at issue in this litigation. If either of these facts makes you suspect bias on my part, so be it.

Note that while I was once something of a climate skeptic (much like Jerry Taylor), my views have changed. Today I have profound disagreements with CEI on the subject of climate change, having argued in defense of the scientific "consensus" on climate change and in favor of a carbon taxamong other measures to address the climate threat. My interest in this litigation arises from this implications for robust debate on matters of public concern, as I explained in this post.