Michael Mann Wins Defamation Lawsuit After 12-Year Battle Against Climate Deniers

On February 8, 2024, a jury unanimously decided in favor of climate scientist Michael Mann in his 12-year defamation battle against Rand Simberg and Mark Steyn, who had compared him to convicted child molester Jerry Sandusky in 2012 blog posts. The jury found Simberg and Steyn guilty of defamation and awarded Mann more than $1 million in damages, representing a landmark victory for scientists facing harassment from climate denial campaigns. The verdict came after years of legal delays and established potential consequences for the most extreme character assassination tactics targeting climate researchers.

Jury Verdict and Damages

The jury awarded Mann $1 in compensatory damages from each writer, along with substantial punitive damages designed to deter similar defamation in the future. The punitive damages reflected the jury’s determination that Simberg and Steyn’s comparisons of Mann to a child molester were not merely offensive but legally actionable defamation intended to destroy his professional reputation. The verdict validated Mann’s 12-year pursuit of accountability for attacks that went far beyond legitimate scientific criticism to personal character assassination.

Significance for Scientific Community

The verdict sent a powerful message to climate scientists who had faced years of coordinated harassment campaigns: there were legal limits to the attacks they could face, and the most extreme defamation could result in substantial financial penalties for perpetrators. For over a decade, climate denial organizations had operated under the assumption they could say almost anything about scientists without legal consequences. Mann’s successful lawsuit challenged that assumption, potentially affecting how climate denial campaigns calibrated their attacks on researchers.

Broader Context of Scientist Harassment

Mann’s case occurred within a pattern of systematic intimidation of climate scientists by fossil fuel-funded denial organizations. Following the manufactured 2009 Climategate scandal, scientists faced death threats, subpoenas from hostile politicians, and coordinated campaigns to damage careers. The Heartland Institute’s 2012 billboard comparing climate scientists to the Unabomber, Competitive Enterprise Institute’s attack advertisements, and years of Freedom of Information Act harassment all contributed to a climate of intimidation designed to discourage scientists from public communication about climate change. Mann became a particular target because his “hockey stick” graph effectively communicated climate science to public audiences.

Limitations and Ongoing Challenges

While Mann won his case against individual writers Simberg and Steyn, the publishers—Competitive Enterprise Institute and National Review—were dismissed from the lawsuit in 2021. A judge ruled they did not meet the “actual malice” standard required for defaming public figures. This split outcome revealed both progress and limitations: individual writers could be held accountable for the most extreme defamation, but the organizational infrastructure publishing and amplifying attacks on scientists remained largely protected. Additionally, in March 2025, punitive damages were reduced from over $1 million to $5,000, though the verdict’s symbolic significance remained.

Significance

Mann’s defamation victory after a 12-year legal battle represents the first major accountability success for a climate scientist subjected to systematic harassment by denial campaigns. The verdict established that comparing scientists to convicted criminals could constitute legally actionable defamation, not protected political speech. For scientists who had endured years of attacks designed to intimidate them from public climate communication, the verdict provided validation and potential deterrence against the most extreme harassment tactics. However, the difficulty of the 12-year legal battle—and the reduction of damages on appeal—demonstrated the immense obstacles to accountability and the asymmetry between the ease of defaming scientists and the difficulty of achieving legal consequences for defamation.