Science is under siege. How Penn’s top climate scientist is fighting back.

The world looked very different on Nov. 1, 2024 — the day that arguably America’s best-known climate scientist, Michael E. Mann, accepted a high-profile new post at the University of Pennsylvania, where he’d already been teaching for a couple of years.

Mann recalled that on this day, he was looking forward not only to the 2025 publication of a major book he was coauthoring — on fighting back against scientific disinformation — but he also had his fingers crossed that an election victory by Democrat Kamala Harris would keep the U.S. government focused on climate action. His new, additional hat at Penn — joining the administration as vice provost for climate science, policy, and action — captured the zeitgeist of what both he and the university thought would be a pivotal but hopeful time in the fight against man-made global warming.

That optimism was crushed just two days later when Donald Trump defeated Harris and soon returned to the White House to implement a reign of anti-science terror — siding with Big Oil to abandon the climate fight, picking the nation’s best-known vaccine skeptic as his top health official, and slashing research dollars beyond recognition.

The perfectly timed new book, Science Under Siege: How to Fight the Five Most Powerful Forces that Threaten Our World — coauthored with high-profile vaccine expert Peter J. Hotez — came out last month at a moment of extreme turmoil for U.S. higher education. And Mann now felt he had to make a difficult choice.

He explained to me that he could hold onto his administrative post at Penn — which, in the contentious Trump era, has doubled down on institutional neutrality, in which the university doesn’t pick a side on controversial public issues. Or he could heed the advice of his own book, and keep brawling in the rough-and-tumble arena for scientific truth.

Mann chose to fight.

“I want to be judged by history as having done everything I could to sort of try to right this ship,” the much-honored climate scientist told me this week. “And obviously that means climate, but it means so much more than that, right? It means the defense of science-based policymaking, the defense of fact-based discourse.”

Late last month, with the political thermometer ratcheted up to Baghdad-in-July levels after the assassination of right-wing icon Charlie Kirk, Mann surrendered his vice provost position, although he remains head of Penn’s climate center and a professor of earth and environmental science. Just as importantly, if not more so, Mann continues to wage war against anti-science smears wherever the battle takes him, from the hothouse of cable TV news to the dirtier trenches of social media like Elon Musk-owned X.

Mann told me the conflict in an increasingly dystopian mid-2020s goes beyond science, that “we need to be using our voice and we need to be using our vote and we need to be using all of the tools that are available to us to try to right this ship — this ship that is the American democratic experiment.”

I’d been planning to write about Science Under Siege ever since Mann told me last year that he and Hotez — a top pediatrician who teaches at Baylor University in Texas, and has also become a leading TV voice defending science — had teamed up to work on it. In the decade since Trump won the presidency for the first time, it’s become clear that the book’s main topic — disinformation and hostility toward science — has become a key driver of the political crisis.

What neither I nor Mann knew in the fall of 2024 was how risky it would get to fight back.

Now that it’s finally on bookstore shelves, Science Under Siege more than meets the moment. The soul of the book is an effort to spell out exactly who is behind the anti-science movement that denies the realities of climate change, or the established science around public health protocols like vaccines — and why.

Mann and Hotez tried to make it easier for the reader with a simple mnemonic device, casting blame toward “the five Ps”: plutocrats who use their billions to fund science denial, petrostates like Saudi Arabia and Russia clinging to fossil-fuel hierarchies, pros at public relations who get big bucks to push their message, the propagandists who boost these memes for clicks, and a passive press that doesn’t challenge any of this.

Their book quoted the famed 20th-century scientist Carl Sagan’s writings on pseudoscience, “foretelling a future when ‘no one representing the public interest can even grasp the issues.’ He feared that the populace would be increasingly unable to differentiate between ‘what feels good and what’s true,’ dependent ‘on media soundbites, predigested science, and pseudoscience.’ That premonition has unfortunately now been realized.”

Science Under Siege pulls back the curtain to reveal the hidden and tangled motives that would cause many of the world’s richest people — including many who became billionaires on the backs of America’s decades of scientific leadership — to promote anti-science narratives. The authors note that the peak of 2020’s COVID-19 stay-at-home orders caused a steep, if temporary, drop in automobile use, which thus made oil barons and their allies more hostile to good public health policies.

“It was like PTSD,” Mann told the audience at a book event at the Penn Bookstore in University City on Tuesday night, explaining that watching the COVID-era attacks on wearing masks, social distancing, experts like Hotez or the government’s public health guru Anthony Fauci, and ultimately vaccines, made him want to “understand the commonalties” with Big Oil’s long war against climate science.

The rise of anti-science has shaped Mann’s career as a climate expert and changed him, for good. The first half of his tenure, in which his research led to breakthroughs in mapping global temperatures over time and the famous “hockey stick graph” forecasting a steep rise in warming from human pollution, was all about the lab.

But a major scandal in which hackers tried unsuccessfully to discredit Mann by publishing his private emails — which led to personal attacks and even death threats — sparked a second act that’s focused on the need for scientists to also focus on winning over the public, and fighting back against lies. The center he leads at Penn, launched when he came to Philadelphia from Penn State in 2022, focuses on how to better communicate the need for climate action.

» READ MORE: Why top U.S. climate scientist moved to Philly | Will Bunch Newsletter

What’s most important about his new tome with Hotez is the belief that understanding the nefarious and powerful roots of science denial should motivate not just their fellow scientists, but also regular folks to join them in fighting rampant disinformation.

Unintentionally, the latest plot twist in Mann’s career arc feels like a metaphor for the choices some Americans are beginning to confront as the man who would be king in the Oval Office dismantles our democracy, and one many more will likely face in the months ahead.

Time and time again since Trump took office in January, we’ve seen elites — whose hefty paychecks depend on not understanding the current crisis — bend the knee. That’s meant editors in Big Media pulling their punches, university presidents sacrificing academic freedom, and CEOs placing profit ahead of morality.

Mann is trying to show us with his own example — walking away from an influential post at an Ivy League school to keep speaking out — that there are other paths besides capitulation.

That’s a bitter pill for boomers or Gen Xers, who have rarely been confronted with harsh societal challenges. But, like it or not, the time for choosing has arrived. Mann told me everyday people have a powerful role to play in changing the conversation away from the manufactured lies of the anti-science brigades.

He encourages citizens who support sound science to start “talking to people, using their voice … speaking out, speaking truth to power. And I couldn’t be advocating for that in good faith if I hadn’t left the administrative position that I was in, because I wouldn’t have been able to accept my own advice.”

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