By Olivia B. Waxman
April 10, 2019

The May 1985 paper, published in top scientific journal Nature, rocked the world: British scientists, backed up by harrowing images, revealed that, over Antarctica, a hole had formed in the ozone layer, the component of the atmosphere that is key in shielding humans from the sun’s cancer-causing ultraviolet rays.

At the time, President Ronald Reagan was in the White House. Environmental policy hadn’t been a priority for him and his advisers, who were more focused on fighting the creep of Cold War communism or federal involvement in issues they believed the states should handle. Even the revelation of the ozone hole didn’t change things — or at least not right away. In fact, as shown in the above clip from the new PBS documentary Ozone Hole: How We Saved the Planet, Reagan’s Secretary of the Interior Donald Hodel was ridiculed in the press for reportedly saying in a meeting that an international treaty wasn’t necessary to address the damage and that Americans should just put on sunscreen and wear hats.

But that response wasn’t enough for the public — and, eventually, neither was it enough for Reagan.

Looking back, environmental issues seem to have become personal for him around that time. The President had a skin cancerous growth on the right side of his nose removed three months after that historic study on the hole in the ozone layer. Between that surgery and his love of being outdoors, riding horses on his California ranch, the President may have been able to see how that it all related to the ozone hole, then-Secretary of State George Shultz told the Ozone Hole filmmakers. Eventually, he got behind the idea of a treaty to phase out chlorofluorocarbons (CFCs), the compound linked to the atmospheric damage.

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Reagan’s EPA Administrator Lee Thomas, who is also featured in the documentary, tells TIME that the President was “supportive” of environmental issues, in his experience, especially when it became clear that there was business support and a market for developing alternatives to CFCs. In 1987, the U.S. and about two-dozen nations signed the Montreal Protocol, the world’s first-ever global treaty to reduce pollution and phase out CFCs. The U.S. Senate ratified it unanimously in 1988. By 1996, bans on the production and importation of CFCs took effect, and scientists say the damage to the ozone layer has been healing, and that the hole could be closed up by the 2060s.

But the treaty didn’t completely solve the problem, and in fact, the alternatives to CFCs created a new set of problems. For example, hydrofluorocarbons (HFCs) found in refrigerators and air conditioners are the kind of powerful greenhouse gases that are a major contributor to climate change; in 2016, an agreement was reached to update the Montreal Protocol to include HFCs.

And, despite Reagan’s initial reluctance, the political circumstances have also gotten more difficult. Back in the Reagan era, sealing up the hole in the ozone layer was more of a bipartisan issue, but the U.S. political climate is more polarized today than it was at the time. That means it could be harder for a legally-binding treaty like the Montreal Protocol — which was unanimously ratified by a Democratic-controlled Senate under a Republican President — to get passed today. Environmental activists say the U.S. has to step up and take bold action on climate change, and even the 2015 Paris Climate Agreement was not legally binding.

Thomas argues it was easy to visualize the hole in the ozone layer then, whereas climate skeptics appear to have a harder time visualizing the research on runaway climate change. And if he has any regret, it’s not seeing link between the ozone hole and climate change sooner.

“We could have probably pushed harder on the climate-change issue, stepped back to make sure I understood the bigger policy issue and put more emphasis on the science and followed it more effectively,” Thomas reflects. “As I was leaving in 1988 and 1989, that was becoming much more of a priority.”

Ozone Hole airs on Wednesday at 10:00 p.m. ET on PBS.

Write to Olivia B. Waxman at olivia.waxman@time.com.

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