Climate skeptic Bjørn Lomborg has built his global brand on keeping his cool. “Cool it,” his best-selling book told those worried about the warming planet. For some reason, however, he seems to have difficulty sticking to the blasé tone when it comes to a 16-year-old climate activist from Sweden.

Lomborg has repeatedly mocked and criticized Greta Thunberg, the prominent young activist who has been sailing across the Atlantic to attend the UN’s Youth Climate Summit and other meetings in the U.S. In June, he tweeted out a cartoon that implied Greta was only useful to climate activists because being young made her unassailable—in four years, it joked, she’d be replaced with someone younger still. Earlier in the year, he’d asked why the World Economic Forum was listening to her at all, and approvingly shared a Quillette article which called Thunberg a fanatic and “absolutist” and which argued adults had a duty to correct her childlike naiveté.

And Lomborg’s on the more civil end of Thunberg’s critics. In April, while tweeting that her policies were “unrealistic” and “costly,” he added that, “of course, she should be treated respectfully, just like all participants in the climate debate.” Several of his followers didn’t seem to care for the caveat, attacking Thunberg with comments about her age and mental health in replies.

As Thunberg approached America, she was followed by a tsunami of male rage. On her first day of sailing, a multi-millionaire Brexit activist tweeted that he wished a freak accident would destroy her boat. A conservative Australian columnist called her a “deeply disturbed messiah of the global warming movement,” while the British far-right activist David Vance attacked the “sheer petulance of this arrogant child.”

In the U.S., former Trump staffer Steve Milloy recently called Thunberg a “teenage puppet,” and claimed that “the world laughs at this Greta charade,” while a widely shared far-right meme showed Trump tipping The Statue of Liberty to crush her boat. We can expect a surge of similar attacks in the U.S. as she arrives in New York this week.