When I was in my late 20s, I was living in San Francisco and playing in a reggae band. At the time, I fervently believed that global warming was a real, man-made problem. And I was vocal about it. Among other things, my friends and I would slap bumper stickers on SUVs that said: “I’m Changing The Climate, Ask Me How.” I didn’t like yuppies, and I resented their big SUVs struggling to climb the city’s steep hills, needlessly warming our planet.

It seemed obvious to me that there was a climate change problem. I heard about it—and read about it—every day in the news. Eventually, I started to study the issue, thinking that I needed to understand it better to write informed articles on the subject.

The first time I experienced a twinge of climate change doubt was when I learned that carbon dioxide (CO2) comprised less than 0.04 percent of the atmosphere. In truth, such a seemingly small amount shouldn’t be underestimated since CO2 starts trapping heat quite effectively at far more minuscule concentrations. But at the time, I thought, “That’s strange. I would have thought it was a lot more.”

The point is I had been barraged with so much global warming hysteria that I figured CO2 must comprise one percent or five percent or 10 percent of the atmosphere. But since it was only 0.04 percent, it seemed to me that the people making the case for global warming should be more careful and to not exaggerate their claims—to not lose credibility.

Regardless, I continued to believe that man was changing the climate. And I was unhappy with friends who seemed like stubborn, cranky holdouts when they disputed this indisputable fact—that humankind was indeed warming the planet.