Sean Davis: What Can We Learn From The Global Effort To Save The Ozone Layer? In 1988, the Montreal Protocol was the first step in a long process to save the ozone layer. Sean Davis explains the impact of the agreement, and the lessons we can apply to the crisis we face today.

Sean Davis: What Can We Learn From The Global Effort To Save The Ozone Layer?

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On the show today, ideas about the Climate Crisis.

SEAN DAVIS: This period is now the warmest in the history of modern civilization - things like increased droughts, increased heat waves, in some cases, increased flooding, melting of Arctic sea ice, land-based glaciers, ice sheets in Antarctica. You also have ocean acidification, which is already damaging...

RAZ: The crisis is so urgent that it raises a question. Can humans come together to solve it?

DAVIS: Yeah, it's a very difficult problem.

RAZ: But we've actually come together before to solve another global environmental crisis - the hole in the ozone layer.

DAVIS: That's right.

RAZ: And this example could serve as a model for climate change. It happened in 1988, and it was called the Montreal Protocol.

DAVIS: The Montreal Protocol is, essentially, the first and only example of a successful international agreement to protect the environment.

RAZ: This is Sean Davis.

DAVIS: I mean, this treaty is the first universally ratified treaty ever that has 193 countries that have signed it. The former secretary general of the U.N., Kofi Annan, said that it's perhaps the single most successful international agreement to date. So I think that that knowledge of how you can use scientific information to inform policy - like, we've been here before.

RAZ: Sean's a scientist at the National Oceanic and Atmospheric Administration.

DAVIS: So I really focus on the stratosphere, which is the layer of the atmosphere above where we live in the troposphere. And that's really where the ozone layer occurs. And the ozone layer is the Earth's sunscreen that protects us from deadly ultraviolet radiation from the sun.

RAZ: So it's like, this is - yeah. We need this thing.

DAVIS: That's right. And in fact, I believe there's evidence that life did not come out of the ocean until there was an ozone layer over it.


DAVIS: It's not an exaggeration to say that a threat to the ozone layer is a threat to human safety.


RAZ: That's Sean Davis on the TED stage. But before we get to the Montreal Protocol and how it saved the ozone layer, we have to go back to the 1970s.

DAVIS: ...When some questionable choices were made. First of all - whew - hairstyles. Second of all, objectively terrible quantities of hairspray. And third, CFCs - chlorofluorocarbons - manmade chemicals that were used as propellant in aerosol spray cans. And you see, it turns out these CFCs were a problem because they were destroying the ozone layer. And actually, ironically, it was human safety that motivated the invention of CFCs in the first place.

You see, in the early days of refrigeration, refrigerators used toxic and flammable chemicals, like propane and ammonia. For good reason, the refrigeration industry wanted a safe alternative, and they found that in 1928, when a scientist named Thomas Midgley synthesized the first commercially viable CFCs. At the time, CFCs were a really remarkable invention. They allowed what we now know as modern-day refrigeration and air conditioning and other things.


RAZ: OK. So CFCs were created in the 1920s. And for a while, they seemed pretty useful. But then what happened?

DAVIS: Well, so, really, these were sort of wonder chemicals because unlike all these other chemicals that had been used before, they were completely nontoxic and nonflammable. So you could literally inhale some of this stuff, and it wouldn't hurt you at all.

RAZ: Wow.

DAVIS: You could blow out a candle. It wouldn't cause a huge explosion. These were really kind of fascinating chemicals that people could use, and they led to this sort of explosion of uses in refrigeration, modern-day air conditioning, blowing of foam. They had all kinds of uses as industrial solvents in electronics manufacturing. But ironically, the thing that made them most useful also made them most dangerous.


DAVIS: It wasn't actually until over 40 years later in the 1970s when scientists realized that CFCs would break down high in the atmosphere and damage the ozone layer, and this finding really set off a lot of public concern. It led, ultimately, to the banning of CFC usage in aerosol spray cans in the U.S. and a few other countries in 1978. Now, the story doesn't end there because CFCs were used in much more than just spray cans. In 1985, scientists discovered the Antarctic ozone hole, and this was a truly alarming discovery. Scientists did not expect this at all.

Before the Antarctic ozone hole, scientists expected maybe a 5 or 10% reduction in ozone over a century, but what they found over the course of less than a decade was that more than a third of the ozone had simply vanished over an area larger than the size of the U.S. And although we now know that CFCs are the root cause of this ozone hole, at the time, the science was far from settled. Yet despite this uncertainty, the crisis helped spur nations to act.


RAZ: All right, so there's agreement. Everybody agrees there's a problem. And the U.S. government signs this treaty with countries around the world, I guess - right? - the Montreal Protocol - that basically says, we're done. CFC's done, and we're going to fix this. Is that more or less what happened?

DAVIS: Well, not quite.


DAVIS: The Montreal Protocol was actually sort of a baby step, it turns out. So the very first iteration of the Montreal Protocol was actually only to decrease the production of CFCs by about 50% before the year 2000. You know, the initial protocol wasn't perfect, but it really allowed - it set up the framework by which we could really hit the brakes on ozone depletion. And that's really what happened. So in the decade-plus since Montreal was signed, it's actually been amended and strengthened eight times.

RAZ: Wow.

DAVIS: And so, you know, you go from this thing that's really a baby step to now complete phaseout of CFCs, and not only complete phaseouts of CFCs and replacement of those, but replacements of the replacements. And we're now seeing that this has been really successful. And I think that's the most optimistic thing to me about the Montreal Protocol and the ozone story - is that it did seem insurmountable. And looking back on it now, you can see, well, yeah - well, we did that. You know, we phased out ozone-depleting substances. We've saved the ozone layer. And not to say it wasn't easy, but it wasn't as hard as people thought.


DAVIS: I think it's worth asking the question, as we face our current environmental crisis, global warming, what lessons can we learn from Montreal? Are there any? I think there are.

First, we don't need absolute certainty to act. When Montreal was signed, we were less certain then of the risks from CFCs than we are now of the risks from greenhouse gas emissions. Second, it takes a village to raise a healthy environment. The Montreal Protocol wasn't just put together by industry and governments or environmental advocacy groups and scientists. It was put together by all of them. And if we're going to solve global warming, it's going to take actions at all levels, from the individual to the international and everything in between.

Third lesson - don't let the perfect be the enemy of the good. While Montreal has become the brake pedal for stopping ozone depletion, at its beginning, it was more just like a tap on the brakes. It was actually the later amendments to the protocol that really marked the decision to hit the brakes on ozone depletion. So to those who despair that the Paris climate accord didn't go far enough or that your limited actions on their own won't solve global warming, I say, don't let the perfect be the enemy of the good.

RAZ: OK. So I hear what you're saying about the parallels with the Paris accord, right? But at the same time, the U.S. was on board with the Montreal Protocol, right? Like, I don't remember anyone saying the hole in the ozone layer was a hoax. Like, everybody agreed it was a big problem, and we had to solve it.

DAVIS: That's right. That's one of the surprising things in sort of looking back on this issue - is that, really, we did achieve a sort of bipartisan consensus in the U.S. that this was a problem. And that's actually evidence of that - is that the Montreal Protocol was unanimously ratified by the U.S. Senate in 1988.

RAZ: Yeah.

DAVIS: I mean, I don't even know if I can imagine anything getting unanimous ratification that, you know, motherhood and apple pie are good anymore.

RAZ: Yeah, but I have to think that carbon just seems, just by an order of magnitude, more complex, right? I mean, CFCs are CFCs. But, like, carbon emissions power the global economy.

DAVIS: That's right.

RAZ: Right? I mean, fossil fuels are still king. And so - I mean, can you really apply the principles of Montreal to, you know, a treaty that basically does the same with carbon emissions?

DAVIS: You know, that's right. There are really important differences between the ozone problem and the carbon problem. And so in the ozone problem, you had couple hundred chemicals, couple hundred different industries involved. And you know, no one really cares what the refrigerant is. They just care that the refrigerator works. So we just had to figure out what the replacements were, and then everything was going to be OK.

RAZ: Yeah.

DAVIS: I think with carbon, you have a situation where it's really one chemical, but it's many different uses. And it's fundamentally about how we produce the energy that we use to give ourselves a comfortable life. But even though the problems are quite different from one another, there is some knowledge there that can be gained.


DAVIS: I think it helps us to contemplate the world we've avoided. Indeed, the world we've avoided by enacting the Montreal Protocol is one of catastrophic changes to our environment and to human well-being. So as we write the story for Earth's climate future for this century and beyond, we need to ask ourselves, what will our actions be so that someone can stand on this stage in 30 or 50 or 100 years to celebrate the world that they've avoided? Thank you.


RAZ: That's Sean Davis. He's a research scientist at NOAA. You can see his full talk at

On the show today, ideas about the climate crisis. Stay with us. I'm Guy Raz, and you're listening to the TED Radio Hour from NPR.

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