The Ozone Hole Showed Humans Could Damage Earth and That We Could Heal It

A worldwide effort to heal damage to the ozone layer is showing early progress.

Earth’s ozone layer acts as a protective shield, absorbing and blocking harmful radiation from the Sun. In the 1970s, scientists began to worry that the ozone layer was being depleted by manufactured chemicals like chlorofluorocarbons, or CFCs, commonly used as a refrigerant and in aerosols.

Soon pressure grew for global action. In 1987, a United Nations summit in Montreal brought global leaders, scientists, and industry representatives together to address the problem. The treaty they ratified, known as the Montreal Protocol, was ultimately a success, pushing chemical companies to invest in profitable alternatives to help save the ozone. Earlier this year, scientists announced that Earth’s ozone layer was starting to recover. 

The Montreal Protocol has been recognized as a template for encouraging science-based policy and global cooperation to address environmental challenges. Today, as global warming caused by burning fossil fuels has become the most pressing climate problem, will the world be able to duplicate the Montreal Protocol’s success?


[CLIP: 1989 NEWS REPORT: The Earth’s protective ozone layer.]

[CLIP: 1986 NEWS REPORT: The hole in the ozone shield is the size of the continental United States.]

[CLIP: 1989 NEWS REPORT: The timeframe for action has become dangerously short.]

David Doniger: People didn’t even really know we had an ozone layer.

[CLIP: ABC, 3-7-89: AL GORE: This problem is of a completely different nature than any we’ve ever faced before.]

Doniger: The threat to the ozone layer was the first global environmental hazard that really broke through.

[CLIP: CBS, 11-5-86: The new study warns that over the next 88 years, Americans could suffer 800,000 cancer deaths.]

Doniger: It’s the first time people could see that we could really damage the entire world.

[CLIP: CBS, 11-5-86): Scientists worry without immediate action, the sun that we’ve always worshiped, our children will soon fear.]

Narrator: Starting in the 1970s, researchers began to worry that the ozone layer, which protects Earth from the Sun’s harmful ultraviolet rays, was being damaged by a new breed of chemicals called chlorofluorocarbons. CFCs, as they were known, had revolutionized the consumer goods industry.


This little can with a button on top is used in hundreds of ways to make your life easier and more pleasant, used as cooling agents in the coils of your refrigerators and as propellants in aerosols of all kinds.]

Narrator: The chemicals made home refrigerators and air conditioners less toxic and more affordable, and were pervasive in American homes.

[CLIP: DUPONT FREON ADVERTISEMENT, 1955: Try Hidden Magic, the perfect solution. Holds without being sticky.]

Narrator: But research by University of California chemists Mario Molina and Sherry Rowland raised new questions.

Durwood Zaelke: In 1974, they came up with a hypothesis that CFCs were migrating to the upper atmosphere and destroying the stratospheric ozone layer, which we need to keep intact because when we destroy it, it lets in ultraviolet radiation.

[CLIP: NBC, 9-13-76: REPORTER: They say this could cause a dramatic increase in skin cancer.]

Doniger: When the news media, the three networks, ran these big stories, it alarmed people.

[CLIP: NBC, 1975: NEWS REPORT: The Earth might be losing as much as 1 percent of its stratospheric ozone every year.

Narrator: The threat to the ozone even entered the pop culture.]


MIKE: Yeah, your hairspray, my deodorant. All spray cans. I read that there are gasses inside these cans, Gloria, that shoot up into the air and can destroy the ozone.

Gloria: What’s the ozone?

Mike: Ozone is a protective shield that surrounds the Earth and protects us against ultraviolet rays. ]

Narrator: But the hypothesis was soon challenged, by some in the scientific community, and by industry.

[CLIP: NBC, 6-11-75: SPRAY CAN MANUFACTURER: It’s complete nonsense.]

Zaelke: They said oh, no, this is a joke. You’re telling us that these invisible chemicals are destroying an invisible layer of stratospheric ozone and letting other invisible rays come down to harm all of humanity?

[CLIP: CBS, 6-12-75: NEWS REPORT: Industry representatives argue most strongly that the case against fluorocarbons is not proven.]

Narrator: The scientists who developed the theory were put on the defensive.

[CLIP: CBS, 6-12-75: REPORTER: Dr. F. S. Rowland was asked if he had changed his mind.

DR. F.S. ROWLAND: No, we have not.]

Zaelke: Molina and Rowland, they were really shunned. They were not invited to any meetings of the chemical associations that normally, professors would go to. They really made it very hard on them.

Susan Solomon: The first time I talked about the ozone layer was at a scientific meeting. You have to recognize that, you know, I was 29 years old. I was probably the only woman in the room at that time. And everybody laughed.

Narrator: Susan Solomon is an atmospheric scientist who began working in the field in the 1980s.

Solomon: We were subject to criticism and questions. I think that is the normal and appropriate way of science. Science has to be able to stand up to criticism. That’s why people should believe it. Because by the time it survives that process, my word, it is strong. There’s no better truth than what the scientific process can give us.

Narrator: Then in 1985, British scientists found new evidence that the ozone layer had developed a hole in the Antarctic. So the following August, Susan Solomon led a team of scientists there and found the first direct evidence that chlorine from man-made CFCs, which had migrated to the Antarctic, was reacting with polar stratospheric clouds and sunlight, causing ozone depletion.

Solomon: Then of course we found out the Antarctic ozone hole was far, far worse than our worst nightmare. It’s enormous, and it’s happening right now.

[CLIP: NBC, 1987: NEWS ANCHOR: Today, scientists who recently returned from the Antarctic told Congress that the ozone layer still is disappearing at an alarming rate.]

Solomon: The sledgehammer that actually dealt that blow had to be the chlorofluorocarbons. Because the chlorine in our atmosphere in general is something like 80 percent man-made.

Narrator: By the mid-1980s, the U.S. had a partial ban on CFCs in aerosols, and calls for more bans and international action were growing during President Reagan’s administration.

Eileen Claussen: It was the Secretary of the Interior, Don Hodel who –  I think as a result of pressures from some countries that did not want to move forward with a treaty on ozone depletion – we were actually asked to develop a cost analysis for everyone to wear hats and sunglasses when they went outside, rather than stop producing the chemicals that destroyed the ozone layer. We had to actually look at the number of people in the United States, multiply it by 237 million to come up with a cost estimate.

[CLIP: ASSOCIATED PRESS, 1987: REPORTER (SPEAKING TO PRESIDENT RONALD REAGAN): How are you feeling, sir? How serious is your nose?]

Claussen: President Reagan had had skin cancer on his nose, and so apparently, that captured his imagination and he agreed that we could go forward and negotiate a solution to the problem.

Doniger: The industry decided they were losing this fight, and as one of their lobbyists told me, it’s better to be at the table than on the menu.

Narrator: In 1987, with the scientific evidence growing on the dangers of CFCs to the ozone, a U.N. summit in Montreal brought global leaders, scientists and industry representatives together to address the issue.

Claussen: I thought Montreal was very hard because it isn’t easy to get your own government in the right place, or 180-odd countries to agree to something. It’s basically almost unwieldy when you think of that many countries with that many issues. And it took all of us to actually get the job done.

[CLIP: NBC, 9-16-87: NEWS REPORT: Representatives completed 10 years of off-and-on negotiations, and this afternoon, most signed what some called an historic agreement to limit production of chemicals many believe threaten the ozone layer in the atmosphere.]

Claussen: One of the interesting things about the Montreal Protocol is that it started off with a 50 percent reduction in CFCs, chlorofluorocarbons. It moved on to make that eventually into an entire phase-out. The science and technology assessment process showed that there were substitutes, and they wouldn’t be that expensive.

Zaelke: The Montreal Protocol is a start-and-strengthen treaty. The developed countries had to develop the substitutes. They had to drive down the price. And then, 10 years later, the developing countries had to do the same thing, and they had funding from the Montreal Protocol.

Doniger: By the 1990s, everyone could see that the Montreal Protocol really was working, had every country in the world joining up.

Narrator: The Montreal Protocol was the first treaty in the history of the U.N. to achieve universal ratification. But the world has been unable to duplicate that success, even as CO2 emissions and climate change become a more pressing issue.

Claussen: In Montreal, we tackled the big issues first — the CFCs — but then went on, piece by piece, to add all these other ozone depleters. If you applied that approach in climate, you’d probably have to start with CO2, which of course is the hardest thing of all. I think what scared a lot of people about climate agreements was that the requirements that people put forward, including the U.S., were something that were not achievable at a lower cost. 

Narrator: Claussen says a key factor in the success at Montreal was that some chemical companies not only began to accept the scientific evidence, but were persuaded to invest in profitable alternatives to help save the ozone.

Claussen: But in climate change, the renewables industry is totally separate from the fossil fuel industry. You have winners and losers in a way that you didn’t really have in Montreal. One thing I have learned is that the lessons from the past are helpful, but they’re not necessarily a recipe for success in the future.

Narrator: But new solutions for CO2 are being explored.

Solomon: Many of the fossil fuel companies now are actually trying things like carbon capture and storage, where they put the CO2 back in the ground at a power plant instead of letting it vent out to the atmosphere. That would be perfectly fine if it’s economic. So far it’s not yet practical.

Claussen: I don’t see how you can get to the level you need to get to with greenhouse gasses unless you deal with carbon capture of some kind. And there have been efforts, but I don’t think they’ve been as robust as they should have been.

Patrick Collins: Ah, 10:15, do you want a pre-launch call? O.K., awesome. Thanks.

Narrator: It’s been 35 years since the Montreal treaty when the world began to work together to heal the ozone. And scientists are carefully monitoring its health.

Collins: So this is the ozonesonde. We’re pulling in air through here, and then any ozone molecule that gets pulled through and goes into our solution, that reacts with the potassium iodide and makes an electrical current.

Narrator: The National Oceanic and Atmospheric Administration launches balloons into the stratosphere each week to measure the ozone layer. And in early 2023, there was good news.

[CLIP: NBC, 1-9-23: NEWS REPORT: Scientists today say the Earth’s ozone layer is actually healing. Look at these pictures. This is a big deal.]

Narrator: Steve Montzka leads a team of scientists at NOAA.

Steve Montzka: One way to characterize what we do is, we’re the global atmospheric policemen or detectives, understanding how atmospheric composition is changing and whether or not those changes are consistent with the controls put in place internationally by the Montreal Protocol. Back in the 1980s, the concentrations of ozone-depleting gasses were going up between 5 and 10 percent per year. It’s amazing to think about the progress that the Montreal Protocol has been able to make in reducing concentrations of these chemicals in the atmosphere.

Solomon: I think the ozone story is astonishing. It should give everyone hope for the future of the environment. What we have is an ozone layer that is already starting to heal. I mean, we should be very proud of ourselves as a humanity.

Montzka: If we continue on our track of vigilance, we can expect recovery of the ozone layer on those time frames – 2050, 2060. I don’t know that I’ll be alive in 2060, but I hope that my children and my grandchildren will be around and be able to say that – Look at that progress, and just think about the efforts that so many people, maybe even including my grandpa, were involved in to make that happen. 


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