Once upon a time, Donald Trump accepted the scientific reality that human activity, primarily burning fossil fuels, causes climate change. He signed on to an ad calling on President Obama to take action on climate change. That was 2009. In the decade since, Trump's Fox News fixation has led him down a steep path of dangerous denial, culminating in his quoting of an industry PR flack who appeared on Fox and Friends to make some profoundly ridiculous claims.

Patrick Moore, who falsely claims to be a co-founder of Greenpeace, claimed that the "climate crisis" is "Fake Science" and that "carbon dioxide is the main building block of all life."

First off, the people who call Puerto Rico home, or Paradise, California, or any number of cities and towns across the country and indeed the planet who have felt the already devastating impacts of climate change would beg to differ. Climate change is already making the heat waves that cause heat strokes worse. It's already raised sea levels, making coastal flooding more common and problematic. It's already doubled the area burned by wildfires in the past few decades. My own research, in fact, shows that state-of-the-art climate models, if anything, are underestimating the impact climate change is having on extreme weather events.

Unlike Moore, I'm actually a climate scientist. But even if I weren't, these findings are readily apparent in even a cursory reading of the National Climate Assessment. That's the major climate report Trump's own administration released last year, and it goes into detail about how climate change is already hurting American communities from coast to coast.

Those details aren't even necessary to point out how ludicrous Moore's other suggestion is, that carbon dioxide is "the main building block of all life." While we are certainly carbon-based lifeforms, it is proteins and nucleic acid, not carbon dioxide, that are the building blocks. In fact, it is classified as a deadly toxin at high concentrations. I'd challenge Moore to prove he believes what he's saying by trying to survive on carbon dioxide.

It wouldn't be the first time someone challenged Moore to prove he means what he says. Back in 2015 Moore told an interviewer that one of Monsanto's pesticides (Roundup) is not only not cancer-causing, but in fact that "you could drink a whole quart of it and it won't hurt you." When the interviewer offered some to Moore to drink, and prove his point, Moore of course became agitated and angry and stormed out in a huff.

This is the sort of person Trump is apparently turning to for advice. A man who has spent decades doing the industry's dirty work while trading off a youthful involvement in Greenpeace. A man who, in response to Trump, tweeted to indicate that he, too was in DC, attending a meeting of William Happer's CO2 coalition, a fossil-fuel funded pro-pollution advocacy organization.

William Happer is also the man chosen by Trump to potentially lead a panel to conduct an "adversarial" review of climate science. Happer is a former physics professor who was caught in a sting in 2015 agreeing to take money from unknown oil and gas interests in exchange for writing a report full of climate denial. As to the quality of Happer's climate science, well that's hard to speak to because he doesn't actually do any climate science, and never has. What he has done, though, is say insane (and offensive) things, like comparing the treatment of carbon dioxide to the "demonization of the poor Jews under Hitler."

That's the quality of advice Trump is seeking.

It's one thing for Fox's primary audience, with their failing faculties and dulled critical thinking skills, to be suckered in by their constant barrage of alternative facts and persuasive fictions. It's quite another for the supposed leader of the free world, who has a thousand scientists at his disposal, to embrace such obviously unscientific claims with such conviction.

Fortunately, some in his party appear to now recognize that outright denial of human-caused climate change has no place in honest political discourse and they seem to be embracing a pivot to the more worthy debate over what we do to address it. Let us encourage this shift and allow climate change deniers to become increasingly isolated as the fringe, irrelevant relic that they are.

Michael E. Mann is Distinguished Professor of Atmospheric Science at Pennsylvania State University. His most recent book, with Tom Toles, is The Madhouse Effect: How Climate Change Denial Is Threatening Our Planet, Destroying Our Politics, and Driving Us Crazy (Columbia University Press, 2016.)

The views expressed in this article are the author's own.​​​​​