A May 1985 report in the journal Nature was alarming. High above Antarctica, a massive hole had opened in the ozone shield that protects life on Earth from the sun’s ultraviolet rays.

The finding confirmed what scientists had warned of since the 1970s: Atmospheric ozone was being broken down by the wide use of chlorofluorocarbons, chemicals known as CFCs, which were found in aerosol sprays, refrigeration and air conditioning.

Slightly more than two years later, dozens of nations meeting in Montreal signed an agreement to significantly reduce CFCs, which the Environmental Protection Agency estimated would prevent 27 million deaths from skin cancers.

“This is perhaps the most historically significant international environmental agreement,” Richard Benedick, the chief U.S. negotiator, said at the time.

Ever since, the Montreal Protocol, as the pact is known, has stood as a milestone of collective action in the face of a planetary environmental threat, as well as a rebuke of the lack of international resolve to tackle the more dire and complex threat of climate change.

Benedick, who was a career diplomat in the State Department when the Montreal Protocol was signed in 1987 and who patiently wore down opposition from foreign nations while withstanding powerful internal critics in the Reagan administration, died March 16 in Falls Church, Va. He was 88.

His daughter, Julianna, said he suffered from advanced dementia.

It is no small paradox that a global treaty to address atmospheric pollution was negotiated during the presidency of Ronald Reagan, who was elected as a champion of business and a sworn enemy of government regulations.

But support for addressing the threat of CFCs to human health was possible because environmental issues were less bitterly partisan than they would later become and because U.S. industry, chiefly DuPont, the largest maker of the chemicals, preferred an international treaty to the possibility of more draconian cuts by Congress.

Benedick, described as energetic and dogged by colleagues, was instrumental to the success. “He was a tenacious guy; he was like a terrier with a bone,” John Negroponte, then an assistant secretary of state who was Benedick’s superior and ally, said in an interview. “I don’t think it would have happened without him.”

In the Reagan administration, leaders of the State Department and the EPA favored regulating CFCs. But in the middle of the international talks, strong opposition emerged from then-Interior Secretary Donald Hodel and William Graham Jr., the White House science adviser.

Hodel said Americans worrying about skin cancer from ozone loss should not expect more government regulation, but should try “personal protection,” namely, hats, sunglasses and sunscreen.

In the end, Reagan came down on the side of Benedick and the State Department, overruling the anti-regulatory faction in his administration. Among the reasons suggested for the decision was that Reagan recently had a cancerous growth removed.

The Montreal Protocol, which required cutting the use of CFCs by half, was signed by 24 countries in September 1987. It was ratified unanimously the next year by the U.S. Senate. In 1990, the protocol was toughened to phase out CFCs entirely eventually. Today, nearly every country in the world has banned them.

Concentrations of long-lived ozone-depleting chemicals in the stratosphere have gradually declined, with the ozone hole above Antarctica expected to heal by the 2060s, according to the National Oceanic and Atmospheric Administration.