More than four years ago, I wrote an article highlighting the views of one of the world's most pessimistic commentators on the climate.

Guy McPherson is a professor emeritus of natural resources and the environment at the University of Arizona. He's also the author of Going Dark and created the website Nature Bats Last.

Back in 2017, I noted why McPherson was predicting that human beings could go extinct by as early as 2026. He linked this grim outcome to current concentrations of greenhouse gases in the atmosphere.

After examining enormous amounts of research, McPherson concluded that large amounts of methane are in the process of being released from the Arctic.

He argues this will trigger abrupt climate change, with the average global temperature rising four degrees Celsius above pre-industrial times, baking the planet.

It's an idea dismissed by many scientists, who say there's still time to prevent a climate breakdown caused by rising emissions. One of the most prominent climate scientists, Penn State University's Michael Mann, says that "McPherson-like false doomism rhetoric is extremely destructive".

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Science educator Scott Johnson has also slammed McPherson's work.

McPherson, on the other hand, repeatedly insists that scientists and the media invariably underplay climate impacts.

He makes that argument again in the video below.

It was posted on YouTube on June 30—the same day that the British Columbia town of Lytton burned to the ground after setting Canadian temperature records on three consecutive days.

The mercury peaked at 49.6 C (nearly 122 F) on June 29.

Meeting Bill Nye

In the wake of record temperatures being recorded in dozens of B.C. communities, I checked out what else McPherson has said recently.

I came across a short video, posted just over two months ago, which included a surprising story by McPherson.

He revealed that on September 10, 2015, celebrity science commentator Bill Nye visited his home to film part of an episode of National Geographic Explorer. It was called Bill Nye's Global Meltdown.

In the video, Arnold Schwarzenegger played Nye's therapist, which McPherson described as "hilarious".

But McPherson's video is anything but amusing—it's actually deadly serious.

According to McPherson, "Nye made a big scene when he arrived—in front of everybody—and shouted at the top of his lungs. Everybody there could hear it. And he questioned human extinction by 2030.

"He thought that was just ridiculous and he made it obvious that that was the way he felt."

Five or six hours later, after shooting a lot of video and having many conversations with McPherson, Nye and the production crew were ready to leave the property. That's when McPherson alleged that Nye said something quite different in private.

"Nye pulled me off to the side, away from any interested ears, and said 'human extinction by 2030? Don't you think that's too conservative?' " McPherson recalled.

He told Nye that yes, he did think that 2030 was too conservative. McPherson acknowledged in the video that he's "typically conservative when it comes to reviewing evidence, because I'm a scientist". 

"Both Bill Nye and Arnold Schwarzenegger now play the part of the misinformed conservationists," McPherson continued. "They insist that you stop burning fossil fuels. That you plant trees. That you go vegan.

"I've commented in the peer-reviewed literature on these strategies. Needless to say, they offered no way to preserve habitat for humans on Earth.

"But in a society that prefers the opinions of celebrities over the science-rich evidence, nonsense sells. And that's not funny."