Michael Mann, among the world's most renowned climate scientists, won a defamation case in D.C. Superior Court against two conservative writers.

Mann, a professor at the University of Pennsylvania, had sued Rand Simberg, a policy analyst, and Mark Steyn, a right-wing author, for online posts published over a decade ago, respectively, by the Competitive Enterprise Institute and the National Review.

Mann is partly responsible for one of the most consequential graphs in climate science, one that helped make the steep rise in global average temperatures from fossil fuel use understandable to a wide audience.

The writers rejected Mann's findings. In his online post, Steyn had called Mann's work "fraudulent." Simberg called Mann, who formerly worked at Penn State, the "Sandusky of climate science" - a reference to Jerry Sandusky, the former Penn State football coach and convicted child sex abuser. Simberg wrote that Mann had "molested and tortured data."

After a day of deliberations, the jury ruled that Simberg and Steyn defamed Mann through some of their statements. The compensatory damages were just $1 for each writer. But the punitive damages were larger. The jury ordered Simberg to pay Mann $1000 in punitive damages; it ordered Steyn to pay $1 million in punitive damages.

Mann did not respond to requests for comment. But in a statement posted to the social media platform X, formerly known as Twitter, he said: "I hope this verdict sends a message that falsely attacking climate scientists is not protected speech."

Steyn did not respond to a request for comment. Simberg's attorney sent an email that cast the decision as a victory for him.

Mann's trial comes at a time of increasing attacks on climate scientists, says Lauren Kurtz, executive director of the Climate Science Legal Defense Fund, who notes that her fund helps more scientists each year than the year before.

"I don't think there's been anything like it. There's never been a case like this," says Kert Davies, director of special investigations at the Center for Climate Integrity, a climate accountability nonprofit, "No one has ever taken the climate deniers to court like this."

Davies says while this ruling may not impact anonymous attackers online, the liability verdict and the dollar figure of this judgment may deter more public figures from attacks on climate scientists. "It may keep them in check," Davies says.