As state and federal officials criticize how climate-change science is pushed on courts, a D.C. judge has ordered one prominent researcher to pay $28,000 in legal fees to two writers he accused of defamation after they questioned his findings.
Michael Mann’s climate conclusions, which include the famous “hockey stick” graph purporting to show a sharp rise in global temperatures after 1900, are cited in the Federal Judicial Center’s latest reference manual for judges in a section on climate science.
More than half of the country’s state attorneys general have called for the FJC to withdraw that portion of the manual. Similarly, the House Judiciary Committee is investigating whether climate lawyers had input on different training material intended for judges.
Those lawyers are helping to push the dozens of climate lawsuits aimed at the energy industry in state courts. Mann’s work, and the pushback it received, is referenced in some of those cases, like the antitrust lawsuit Michigan filed last month against companies like Exxon and Chevron.
Also last month, D.C. Superior Court judge Alfred S. Irving ordered Mann, formerly a professor at Penn State University and now at the University of Pennsylvania, to pay additional sanctions a year after he reversed a $1 million jury verdict for him and ultimately ordered him to pay $1.1 million of his critics’ legal expenses.
In this latest order, the judge ruled Mann’s lawyers improperly showed the jury a chart suggesting the scientist had lost $9.7 million in grants due to the alleged defamation while knowing the information was false.
“To date, Dr. Mann and his attorneys have provided no plausible explanation why they prepared a demonstrative that contained incorrect figures to be used at trial, when they could have very well prepared a demonstrative with the correct figures,” Judge Irving wrote in a Jan. 22 order. “This is particularly troubling given that the lost grant funding amounts were central to Dr. Mann’s case.”
Mann sued Rand Simberg and Mark Steyne after they criticized him in blogs published by the Competitive Enterprise Institute and National Review online, using strong terms including “manipulation” and “misconduct.” Simberg compared Penn State’s response to the “climategate” controversy over leaked emails between Mann and other climate scientists to the case of former Penn State football coach Jerry Sandusky, who was convicted of sexually abusing children.
At trial, Mann’s lawyers portrayed the blog posts as attacks on climate science and said Mann had suffered a dramatic decline in grants because of them, as well as social ostracization. They presented the chart showing millions of dollars in lost grants even though Mann had acknowledged under oath there was no evidence to support it. Mann had testified his grants fell from $3.5 million a year to $500,000 because of the alleged defamation, and “stayed there.”
A jury awarded Mann a token $1 in actual damages but $1 million in punitive damages, which Judge Irving later called “grossly excessive” and cut to $5,000. The judge then ordered Mann to pay $530,000 in legal fees to the National Review and $477,000 to Simberg. The National Review later dropped its demand for fees.
In a March 2025 order, Judge Irving said he was “quite frankly impressed, stunned” that Mann’s lawyers showed the jury the exhibit listing lost grants that defense lawyers proved were largely false.
“Clearly, the plaintiff was aware that the jury was being presented with an exhibit that contained incorrect information,” the judge said at the time. “And you wanted the jury to take that back to the jury room and deliberate on those figures.”
A lawyer for Simberg said Mann’s grants went down because he stopped applying for them. Simberg “could have called Michael Mann the Mother Theresa of Climate Science, and Michael Mann still would have seen a decline in millions of dollars of grant funding,” the lawyer said at trial.
Mann’s lawyers, including John B. Williams and Peter Fontaine, argued any mistakes were the defense’s fault, for preventing him from presenting other evidence. They said the errors in the chart were exposed during cross-examination and the jury could decide which numbers were correct.
In his latest order, the judge awarded defense attorneys about $500 an hour for the time they spent defending against the error-ridden jury exhibit.
Mann’s “hockey stick” conclusions about rising temperatures due to greenhouse gas emissions came under attack after hackers released emails in 2009 between him and U.K. researchers suggesting they manipulated data and pressured journal editors to support the conclusions of the Intergovernmental Panel on Climate Change.
Those emails also undermined the idea of scientific consensus, showing researchers argued about basic methods for calculating global temperature change.
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