The ozone layer is still healing…thanks to science

In the mid-1980s, scientists published a startling finding https://www.nature.com/articles/315207a0–a giant hole in the ozone layer over Antarctica. That’s the protective shield that blocks large amounts of harmful UV radiation. And without it, the rate of cancer, cataracts and crop failure would skyrocket. Today on the show, we dive into ozone science and examine how scientists successfully sounded the alarm and solved an Antarctic mystery. Check out our episode on an Antarctic plankton mystery https://www.npr.org/2025/03/10/1237260294/research-plankton-climate-change-whales-antarctica-polar-fjord. And, listen to our monthly https://www.npr.org/transcripts/1266983858 series https://www.npr.org/2025/04/22/1266983681/spring-flowers-earth-day-phenology Nature https://www.npr.org/2025/09/30/nx-s1-5518203/ocean-climate-change-flood-sea-level Quest https://www.npr.org/2025/05/27/1266983774/kids-climate-change-anxiety-family. Interested in more atmospheric science? Email us your question at [email protected] mailto:[email protected]. Listen to every episode of Short Wave sponsor-free and support our work at NPR by signing up for Short Wave+ at plus.npr.org/shortwave http://plus.npr.org/shortwave. This episode was produced by Berly McCoy. It was edited by Rebecca Ramirez. Tyler Jones checked the facts. The audio engineer was Becky Brown. See pcm.adswizz.com https://pcm.adswizz.com for information about our collection and use of personal data for sponsorship and to manage your podcast sponsorship preferences. NPR Privacy Policy https://www.npr.org/about-npr/179878450/privacy-policy

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• 0:00Speaker 00

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• 0:18Emily Kwong?

  You're listening to Short Wave from NPR. Hey, Shortwavers. Emily Kwong here with a love letter to the layer of the Earth's atmosphere that acts like a sunscreen. I'm talking, of course, about ozone.

• 0:32Speaker 02

  Without ozone, that would be impossible to live on Earth.

• 0:35Emily Kwong?

  This is atmospheric scientist Irina Petropadlovskaya. The ozone is a layer of the stratosphere with a high concentration of ozone molecules, each one made out of three oxygen atoms.

• 0:47Speaker 02

  And it's very good for us. It protects us from the harmful UV radiation. And that's why we want more of this, not less of that.

• 0:56Emily Kwong?

  To form, ozone needs sunlight, which bursts oxygen apart. You know, the O2 version we breathe. And then each single atom of oxygen can then connect with another O2 to form our girl, O3, aka ozone. But sunlight can also destroy ozone, and the balance generally depends on the season. But starting in the 1970s, something weird happened.

• 1:21Speaker 02

  Scientists noticed that ozone is changing slowly but surely. But they didn't know how much it's changing until maybe the beginning of 80s, when the scientists actually measured significant change. And it was happening in the springtime in Antarctica. And so they noticed that there was less ozone.

• 1:42Speaker 03

  A giant hole is forming in the Earth's protective ozone layer.

• 1:46Speaker 02

  Scientists discovered a hole in this protective ozone.

• 1:48Emily Kwong?

  Remarkable loss of ozone that occurs over the Antarctic in October. A lot of people call it the ozone hole, but it was really more of a thinning. Scientists launched weather balloons to study its size, and they found something shocking. High levels of two chemicals, chlorine and bromine, were breaking down ozone faster than it was being made, letting in the kind of radiation that causes cancer, crop failure. And it was happening because of ozone-depleting substances made by us on Earth. So the race was on to save the world.

• 2:22Emily Kwong?

  Today on the show, how researchers mobilized on a global scale to close the ozone hole, plus why the ozone layer is still recovering and what climate scientists can learn from this success. You're listening to Short Wave, the science podcast from NPR.

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• 3:49Emily Kwong?

  So, Irina, I want to focus on how the ozone is operating over Antarctica, because that's where the hole is. And I know that the ozone layer over Antarctica naturally thins, because things are a little different there, right?

• 4:03Speaker 02

  Yeah. In Antarctica, the maximum of the ozone is happening during months of December, January. And it's happening naturally. You know, there is an increase in ozone throughout the year. And then when the polar night comes in, there is no sun, and so there is no much of the ozone production happening during the wintertime.

• 4:29Emily Kwong?

  And that's because sunlight triggers ozone formation, but also sunlight destroys ozone. So the amount of ozone is always kind of fluctuating when the sun is present. And During the Antarctic polar night in June, July, and August, when there's no sun, the ozone amounts are basically steady. They don't really fluctuate.

• 4:49Speaker 02

  Yeah.

• 4:50Emily Kwong?

  And then in the spring, the sunlight comes back, and these chemical reactions start happening again. But isn't the Earth's atmosphere always moving and mixing? So like, wouldn't the air from other parts of the world that have access to sunlight mix with Antarctica's air?

• 5:02Speaker 02

  Antarctica has a very specific process. Because it's a continent, the atmosphere can create these strong winds that circulate around Antarctica. And so they separate the air that's over Antarctica from the rest of the other latitudes outside of Antarctic vortex. So there is no really way to mix it with other airflow.

• 5:26Emily Kwong?

  Oh, OK. So the atmosphere of Antarctica is isolated because of this polar vortex, which results in this seasonal cycle that has its rhythms. Now, let's go back in time. When scientists really started noticing the ozone layer was changing over Antarctica, beyond what was typical for the seasonal rhythm. And these researchers went on an expedition to Antarctica to figure out why. What did they do?

• 5:51Speaker 02

  So scientists flew into Antarctica on the aircraft, and they also set up the camp on Antarctica continent. But what the most interesting observation they made is that when they're flying inside of Antarctica, they continuously measured both ozone and chlorines, the chemicals that they thought that might be destroying ozone. And they noticed that flying into Antarctica, the ozone started to go down, and chlorine started to go up. And so that made a very good sense to them, so that those chemicals are destroying ozone.

• 6:28Emily Kwong?

  It's like their Achilles' heel. I read that one chlorine atom can destroy over 100,000 ozone molecules.

• 6:35Speaker 02

  Yeah, definitely.

• 6:36Emily Kwong?

  What the heck were we doing in the 50s and 60s that created this abundance of chemicals in the atmosphere?

• 6:42Speaker 02

  Yeah. Chemicals that we can use in refrigeration.

• 6:47Emily Kwong?

  Oh.

• 6:47Speaker 02

  Those chemicals were put in the firefighting equipment. For example, they were very effective at that. Um, they were put in the aerosols, uh, sprays. And so they've been used for fumigation of the vegetables and the fruits. So that they were working, you know, really well. But what I think people did not realize right away is that those chemicals actually are capable of escaping into the stratosphere.

• 7:13Emily Kwong?

  But I'm like curious, like, how did stuff made on Earth produce molecules that got all the way up there? Because the stratosphere is miles above our heads. It's like where planes fly. Like, how could chemicals travel upwards that high?

• 7:27Speaker 02

  Well, the atmosphere has this mixing properties. You know, there are a lot of, um, exchange between the troposphere and stratosphere and the tropics.

• 7:37Emily Kwong?

  Oh.

• 7:37Speaker 02

  And, um, they can travel also with this flow of the air from the tropics into the middle latitudes in the polar region. There is the so-called Broerdorf's in circulation in the atmosphere and they get distributed everywhere.

• 7:50Emily Kwong?

  Oh, so they hang out a long time.

• 7:53Speaker 02

  And then they can hang out for a long time, yes. Oh, there's another thing that we need to remember. Um, there is also the specific clouds that are formed in Antarctica. They're called the polar stratospheric clouds.

• 8:06Emily Kwong?

  Polar stratospheric clouds.

• 8:08Speaker 02

  So they're also very, uh, quite essential for this depletion to occur. And the reason for that is that they actually set up this, uh, activation of the chlorines that are typically not very active. Um, so they, uh, they, they set them up such that there will be, um, only chlorines and bromines released once the sun comes back. And so then those chemicals are released and then they will start to destroy ozone very, very rapidly.

• 8:36Emily Kwong?

  Yeah.

• 8:37Speaker 02

  But there are also other chemicals that get frozen into the polar stratospheric clouds that are typically neutralize this reactions. And so there is nothing to stop those chemicals to destroy ozone for

• 8:48Emily Kwong?

  Oh.

• 8:49Speaker 02

  for some period of time. Until the polar stratospheric clouds disappear.

• 8:52Emily Kwong?

  What, uh, yeah. What an accumulation of forces that led to this problem. Okay, so what did scientists do in response? Because obviously today.

• 9:03Emily Kwong?

  The ozone is OK. So what happened ultimately to save the world?

• 9:09Speaker 02

  Right, exactly. So they started to present their findings and to the public, to the governments. And so eventually they got enough people who listened to their worries that the Vienna Convention happened where the representatives from many, many countries got together and they discussed these issues.

• 9:30Emily Kwong?

  Wow.

• 9:31Speaker 02

  And then the Montreal Protocol in 1987, actually signed by every country. I mean, this is really amazing. Agreed to stop production and use of those ozone-depleting substances.

• 9:44Emily Kwong?

  Right, and that is how we get to the point now where the ozone layer is doing well. It's the, I read it's the fifth smallest since the crisis. Why hasn't the ozone fully thickened over Antarctica? Is it because people are still using chemicals even though they're banned?

• 10:00Speaker 02

  Some chemicals actually can live, once they get into stratosphere, they can live up to 100 years. So once they're released, let's say they've been released in the 50s and even before that, they have a quite a long way to go before they get completely removed from the stratosphere. So that ozone hole is recovering, but you know, very slowly because we still have a lot of these chemicals in the atmosphere still.

• 10:24Emily Kwong?

  And to this day, people are still monitoring the ozone layer, right? Like, we didn't fix the problem and just abandon Antarctica, right?

• 10:31Speaker 02

  No, we are very lucky. We still have a lot of observations. So yes, I mean, we still need to monitor it. And the reason for that is that there are some other chemicals that have been released in the atmosphere. They're not really destroying ozone, they're replacement for those CFCs. We need to know how they impacting the atmosphere. And some of them are so-called greenhouse gases. So they're heating the atmosphere. With that, there is also some impact on the way how the ozone is recovering.

• 11:03Emily Kwong?

  Yeah. Greenhouse gas emissions, we talk about that a lot on Short Wave. And it's a useful comparison because that existential issue is also human-caused and could be human-solved, so to speak. So in comparison to climate change that we're all struggling with now, why do you think the ozone issue was dealt with so swiftly?

• 11:23Speaker 02

  I think because that was a problem affecting everybody.

• 11:26Emily Kwong?

  Yeah.

• 11:27Speaker 02

  It wasn't something that would require people to stop using, for example, you know, that people were advised not to use their soils, for example, by scientists, but it wasn't a very big impact on everybody's life.

• 11:42Emily Kwong?

  Giving up CFCs was a lot easier than giving up like oil and gas.

• 11:45Speaker 02

  Yes, yes, I think that was one condition.

• 11:48Emily Kwong?

  Yeah.

• 11:49Speaker 02

  And then, of course, you know, the industry also agreed to to change and move away from the CFCs and start producing other chemicals that are not destroying ozone. And not just that, that the developed countries also said that they will set aside the finding for supporting and helping the developing countries to change their technology. And so that that still continues.

• 12:15Emily Kwong?

  How does that make you feel as a researcher? That humanity scientists working with policymakers, working with many stakeholders, were able to do this? How do you feel about that?

• 12:24Speaker 02

  I'm really excited about that. And we were very young when when we started to hear about ozone, you know, in my generation, and it was a very acute problem. And it's just really good to see that ozone is on the way to recovery. It's in the 2050s, 60s, you know, when people expect the full recovery of the ozone. But, you know, who knows? Maybe I will live too long enough to see that.

• 12:49Emily Kwong?

  I hope you do. I hope I do. Idina, thank you so much for coming on Short Wave.

• 12:54Speaker 02

  Oh, thank you so much for taking time.

• 13:00Emily Kwong?

  If you liked this episode, follow us on the NPR app or wherever else you listen to podcasts. And check out our episode about how tourists are solving a Plankton puzzle in Antarctica and Short Wave's Nature Quest series. That's where we delve into an environmental mystery driven by your questions. I'm Emily Kwong. Thanks for listening and tune in tomorrow for more.

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