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Susan Solomon and Stephen Andersen on Saving the Ozone Layer

16 September, 2021

  • The industrial and commercial uses of chlorofluorocarbons (CFCs)
  • How we discovered the atmospheric effects of CFCs
  • The Montreal Protocol and its significance
  • Dr. Solomon's, Dr. Farman's, and Dr. Andersen's crucial roles in helping to solve the ozone hole crisis
  • Lessons we can take away for climate change and other global catastrophic risks


Watch the video version of this episode here

Check out the story of the ozone hole crisis here

0:00 Intro

3:13 What are CFCs and what was their role in society?

7:09 James Lovelock discovering an abundance of CFCs in the lower atmosphere

12:43 F. Sherwood Rowland's and Mario Molina's research on the atmospheric science of CFCs

19:52 How a single chlorine atom from a CFC molecule can destroy a large amount of ozone

23:12 Moving from models of ozone depletion to empirical evidence of the ozone depleting mechanism

24:41 Joseph Farman and discovering the ozone hole

30:36 Susan Solomon's discovery of the surfaces of high altitude Arctic clouds being crucial for ozone depletion

47:22 The Montreal Protocol

1:00:00 Who were the key stake holders in the Montreal Protocol?

1:03:46 Stephen Andersen's efforts to phase out CFCs as the co-chair of the Montreal Protocol Technology and Economic Assessment Panel

1:13:28 The Montreal Protocol helping to prevent 11 billion metric tons of CO2 emissions per year

1:18:30 Susan and Stephen's key takeaways from their experience with the ozone hole crisis

1:24:24 What world did we avoid through our efforts to save the ozone layer?

1:28:37 The lessons Stephen and Susan take away from their experience working to phase out CFCs from industry

1:34:30 Is action on climate change practical?

1:40:34 Does the Paris Agreement have something like the Montreal Protocol Technology and Economic Assessment Panel?

1:43:23 Final words from Susan and Stephen



Lucas Perry: Welcome to the Future of Life Institute Podcast. I'm Lucas Perry. This is a special episode with the winners of the 2021 Future of Life Award. This year's winners are Susan Solomon, Stephen Andersen, and Joseph Farman, who all played an essential part in the efforts related  to identifying and mending the ozone hole. In this podcast, we tell the story of the ozone hole from the perspective of Drs. Solomon and Andersen as  participants to the mystery of the ozone hole and the subsequent governance efforts related to mending it. Unfortunately, Joseph Farman passed away in 2013, so his role in this story will be told through our guests on his behalf.

For those not familiar with the Future of Life Award, this is a $50,000/person annual prize that we give out to honor unsung heroes who have taken exceptional measures to safeguard the future of humanity. In 2017 and 2018 the award honored Vasili Arkhipov and Stanislav Petrov for their roles in helping to avert nuclear war. In 2019 the award honored Dr. Matthew Meselson for his contributions to getting biological weapons banned. In 2020, the award honored Bill Foege and Viktor Zhdanov for their critical contribution to eradicating small pox and thus saving roughly 200 million lives so far.

For some background on this year's winners, Dr. Susan Solomon was the Chemistry and Climate Processes Group of the National Oceanic and Atmospheric Administration until 2011. She now serves as the Ellen Swallow Richards Professor of Atmospheric Chemistry and Climate science at MIT. Dr. Solomon led an Antarctic ozone research expedition which both confirmed that CFCs caused the ozone hole, and showed that sunlit cloud tops catalyzed the ozone destruction process to be much faster.

Dr. Stephen Andersen is the American Director of Research at the Institute for Governance and Sustainable Development, and is former co-chair of the Montreal Protocol Technology and Economic Assessment Panel. Andersen’s tireless efforts brought together leaders from industry, government and academia to implement the  needed changes in CFC use to mend the ozone hole. His efforts played a critical role in making the Montreal Protocol successful.

Joseph Farman was a British geophysicist who worked for the British Antarctic Survey. In 1985, his team made the most important geophysical discovery of the 20th century: the ozone hole above the Antarctic. This provided a stunning confirmation of the Rowland-Molina hypothesis that human-made chlorofluorocarbons were destroying the ozone layer, and much faster than predicted. This galvanized efforts to take action to mend the ozone hole.

And with that, I'm happy to present the story of the ozone hole and the fight to fix it with Susan Solomon and Stephen Andersen 

Lucas Perry: So I'd like to start off with the beginning where it's the early 20th century, and we have CFCs, chlorofluorocarbons, which is a difficult word to say. And they're in quite a lot of our manufacturing and commercial goods. So I'm curious if you could start there by just explaining what CFCs are and what their role was in the early 20th century.

Susan Solomon: They weren't actually discovered until I think around the twenties, if I recall, maybe Steven can correct me on that, but they were initially used in air conditioning. So that was a great advance over using things like ammonia, which is toxic and explosive and all kinds of horrible things, and the great thing about the CFCs is that they're non-toxic at least, when you breathe them, although they're very toxic to the ozone layer, they're not toxic to you directly. And they became really widespread in use though, when they began to be used as spray cans in aerosol propellants and that didn't really happen until somewhat later. I think that the spray can business really started exploding in the Post-World War Two era, probably in the 50's and 60's. And then it was discovered that these things have very long lifetimes in the atmosphere, they live, depending on which one you talk about, for some 50 to a 100 years.

So that is just staggering because what it means is that every year, whatever we put in, almost all of it will still be there the next year. And it'll just pile up and pile up and pile up. So initially, a few people who worked on it thought "Hey, this is great! It's a terrific tracer for atmospheric motion, how cool is that?" But it turned out that although that's somewhat true in the lower atmosphere, in the upper atmosphere, they actually break down and make chlorine atoms, and those chlorine atoms can go on to destroy ozone. And we first became aware of this through some wonderful work by Molina and Rowland in the mid-seventies, which later won the Nobel Prize for chemistry, all along with Paul Crutzen.

Stephen Andersen: I could circle back on a little bit of the details of the technology if you'd like?

Susan Solomon: Sure, go for it, Steve.

Stephen Andersen: The year was in the twenties, 1929, and it was invented by Thomas Midgley, who was working for Frigidaire Division of General Motors, and just as Susan said, this was viewed as a wonder chemical because the chemicals at that time were things like methylene chloride and ammonia and even gasoline is a refrigerant, so it was very dangerous there were lots of injuries, by that time America's waters were polluted, so it was difficult to use ice from ponds.

And so it was immediately commercialized to replace these flammable and toxic refrigerants, and then just as Susan said, the companies that produced it slowly looked at other markets; aerosol starting with pesticides for soldiers in World War Two, and then finding a commercial market and then solvents, because it's a very effective solvent for electronics and aerospace, and then there were other uses that came along such as making rigid and flexible foam, and then finally towards the end there were elegant uses such as hospital sterilization, and as the aerosol for metered-dose inhalers that are used for asthma patients. So it had extraordinary uses and it was not appreciated until 1974 when Mario Molina and Sherry Rowland discovered that these chemicals could destroy the ozone layer.

Lucas Perry: So before we get to Molina and Rowland, I was curious if we could actually start with James Lovelock because we're releasing and creating all of these CFCs, and it seems like he's the first person who actually takes a look at these things in the atmosphere. So could you explain James Lovelock's role in this story?

Susan Solomon: Sure. He invented the gas chromatograph and made a lot of money off of it and became independently wealthy because it's a very useful instrument for measuring all kinds of things. And he took it on a... He was British, and he took it on a British research vessel and sailed from the Northern Hemisphere down to almost the Antarctic, and showed that he could understand exactly what the distribution of the CFC that he was measuring was, based on the amount that had been emitted. And he said "Oh, isn't that cool? It's a great tracer for atmospheric motion", as I've mentioned before. In fact, I'm pretty sure in his paper, there was some kind of sentence like "this couldn't ever conceivably pose any hazard because it's so non-toxic", but of course, having less of an ozone layer is not good for life on the planet because ozone absorbs ultraviolet light that is very, very important for protecting us from sunburn and cataracts and protecting animals and plants and all kinds of things.

Susan Solomon: So depletion of the ozone layer is actually a threat to both humanity and the planet. I do want to say it wasn't until somewhat later, 1985, when scientists from the British Antarctic Survey actually discovered the ozone hole and what they were doing was measuring total ozone in the Antarctic, they'd been doing it since the 1950s, and they were able to show that sometime around the late seventies, it started dropping like a rock way, more ozone depletion than Molina and Rowland had ever imagined.

So it turns out that these chlorofluoro chemicals are actually even more damaging to the ozone layer in the Antarctic, and actually also to some extent at mid-latitudes as we now know, than we originally thought. So it's been sort of a cautionary tale of don't be too sanguine about any chemical made in the lab. When you make something in the lab that nature doesn't make, I think you should always do a double-take, especially if it has a very long atmospheric lifetime and builds up in the way that I described. So that means you can't get rid of it if you stop using it. You can't eventually, but it's going to take a long time for the atmosphere to cleanse itself.

Lucas Perry: Could you explain why James Lovelock was initially interested in CFCs and what his investigation led to scientifically?

Susan Solomon: As far as I know, he really just wanted to see what their distribution was like to get some sort of a handle on what they might be... What his instrument might be useful for. I don't actually know of a use beyond that, do you, Steven?

Stephen Andersen: No, I think that's right. He was looking for gases that were indicators, as you suggest, and of course he had a device that would measure other chemicals, but I think he was immediately struck by the fact that he was seeing the same chemical at all locations that he sampled, and then he made the natural connection of saying "Where did this chemical originate? How long did it take to mix in the lower atmosphere"? So I think it was a good, solid, scientific inquiry of a very intelligent person with a new instrument.

Susan Solomon: Maybe we should clarify, I said he went all the way down almost to the Antarctic, but I neglected to underscore that of course there is no chloro fluoro carbon emission in the Antarctic, right? At that time there was nobody even... There were no stations, there was nobody there. So any chlorofluorocarbon that could get there had to of have gotten there by atmospheric transport and it would also tell you that it has to have a fairly long lifetime because if you emit, let's just say sulfur dioxide from a power plant in the Ohio Valley, yeah it's a serious issue, it can cause acid rain, it can cause little particles that are bad for your lungs, it does a lot of bad things, but it's not going to be found in the Antarctic. It just doesn't have that long of a lifetime, it rains out. So this proved that they were a great tracer in his mind I think that's what he was attracted by.

Lucas Perry: We're in this world where CFCs are basically being used for a ton of different applications. Our current understanding at that time was that they were nonreactive and non-toxic, so basically a wonder chemical that could be used for all sorts of things and was much safer than the kinds of chemicals that we were using at the same time. And here comes James Lovelock, who, from my reading, it seemed like he first got interested in it because his view from his house was hazy, and he didn't know why it was hazy and he wanted to figure out if it were manmade chemicals or what this pollution that was obscuring his vision was.

And so he starts measuring all these CFCs everywhere, and now we're in a world where it seems very clear that the CFCs are abundant in the lower atmosphere. So let's start to pivot into Mario Molina and Frank Rowland's role in this story and how we begin to move from noticing that there are so many CFCs in the atmosphere to finding out that there might be a problem.

Susan Solomon: I will say that Dr. Rowland has passed away, unfortunately, so has Molina more recently, but he never went by Frank, he went by Sherry. His name was indeed F Sherwood Rowland, but he was known to everyone as Sherry Rowland.

Lucas Perry: Okay.

Susan Solomon: Go ahead, Steve, do you want to take this one?

Stephen Andersen: Yeah, sure. The story of it is actually another great science story. Mario Molina had finished his doctors degree at University of California, Berkeley, and had taken a post-doctorate study with Sherry Rowland at University of California Irvine, and they looked at four or five interesting topics, and I think that the history is that Molina saw this one as being particularly intriguing, even though it was slightly outside either of their expertise.

So it was a stretch for them, but it gave them a chance to look at something that could be potentially very important. And then the story is that as they began to investigate, it started to seem more and more obvious to them. And it became a rush for a conclusion because they were worried about the effect of their work. There's one story that Sherry Rowland tells us, that he came home from work one day and his wife, Joan, asked "How did your day go? How is your work"?

And he replied something like "Well, the work is fantastic, but I think the earth is ending". So you can imagine the tension, the creative tension, and then they published their article I think in April of 1974, and there was no uptake by the press, there was no scientific confirmation. It was a quiet time until that fall, the Natural Resources Defense Council, NRDC, saw this, the scientists there, and recognize this was a big public policy issue. So at the American Chemical Society fall meeting, they had a presentation by Molina and Rowland, and then by the best of good luck of ruthless corporate behavior, the industry attacked them and made this scientific study news worthy.

So this was a tremendous good fortune, oddly enough, because then all of the press was asking "What are you talking about? Why is it important and what could happen?" And that cultivated in Molina and Rowland, the ambition and... Sherry Rowland called for a ban on aerosol cosmetic products; hairspray and deodorants. And so this was stepping out of their role of a normal scientist and becoming an activist, and of course there was a boycott that was quite spectacularly successful in the United States, and then some product bans.

Susan Solomon: Yeah and actually I just want to say, I think we should be proud in the US that there was a consumer boycott. People turned away from spray cans and that actually, interestingly enough, did not happen in Europe, they kept using them. So we can look back on that time as one in which people were environmentally very aware in this country, not just on the issue of the ozone layer, but also for things like smog and clean water, all those issues had attracted a lot of attention right around this time. I will also say that it's interesting that at the time of the Molina & Rowland work, they were talking about the fact that from the best of our understanding of the day, in a hundred years we might see a few percent decrease in the total amount of ozone.

So kind of a small effect, far in the future, kind of like the way some people used to talk about climate change until maybe this year or the last few. And the Antarctic ozone hole was a huge wake up call because what they found was that ozone had dropped by more than 30% over Antarctica already by 1985, something that no one had anticipated. So it was a huge shock to the science community. And at first a fair number of people didn't really take it seriously. I can remember being in scientific meetings with people who said "Oh, that British group, they must just be wrong". I won't say who they were, but it of course turned out that they weren't wrong. They were confirmed quickly by other stations in the Antarctic and also by satellite data. And we now understand the chemistry that actually made the chlorofluorocarbons even more damaging than we thought they would be much, much better than we did before.

Lucas Perry: Could you explain a little bit of the scientific mystery and the scientific inquiry that Molina and Rowland were engaged in, the kinds of hypotheses that they had and the steps from going from okay, there are lots of CFCs in the lower atmosphere to eventually understanding the chemical pathways in their role in ozone depletion.

Susan Solomon: The big issue that they had to deal with was how do these compounds get destroyed, and what is their atmospheric lifetime? And they actually went into the laboratory themselves to try to make measurements relating to that. So they were able to show, I think through the measurements that they made, that the CFCs didn't react with... They didn't rain out, that they weren't water-soluble, so that was not an issue. That they didn't react with sand, there was some idea that somebody had suggested that they would be destroyed on the sands of the Sahara and that turned out, of course, not to be true. And then they looked at the way in which they would break down, what would happen to them them? If they have no way to break down in the lower atmosphere, the only place for them to go is up, up, up, up, and as you go up, you reach much more energetic sunlight, the higher you go.

Obviously if you're in the limits of space, you're getting the direct light from the full spectrum of what the sun can put out. But if you're down on the ground, you got a lot of atmospheric attenuation. So they began to realize that once these molecules got into the stratosphere, that they would eventually break down, make chlorine atoms, and it was known already that those chlorine atoms could go on to react with ozone. And then there's a another process, which I'm not going to go into, that actually leads it to a catalytic cycle that destroys ozone pretty effectively, and that process was already known from other work.

Lucas Perry: Could you actually say a word or two about that? Because I actually think it's interesting how a single chlorine atom can destroy so much ozone.

Susan Solomon: Sure. The chlorine atom reacts with ozone, that makes chlorine monoxide plus O2. Now, if that was all there was, it would be a one-way process, you could never deplete more ozone than the chlorine that you put in. But what happens is that the chlorine monoxide can react with atomic oxygen, for example, so there's... If you go up into the well... In the lower atmosphere, most of the oxygen as we know is in the form of O2, right? So it's the oxygen that we breathe is O2. That's actually true as far as total oxygen, pretty much all the way up, but as you get up into the stratosphere, oxygen actually also encounters that high energy ultraviolet light, which breaks it down and makes atomic oxygen, and ozone can also be broken down by high energy light, and that makes it atomic oxygen, ozone is O3.

So basically what first happens is the O2 breaks down with ultraviolet light making atomic oxygen, the atomic oxygen reacts with another O2 to make ozone, but then the ozone, let's say photolyzes to make O, so now if the O comes along and reacts with the ClO, making chlorine atoms again, plus O2, you've liberated the chlorine atom, it can go right back around and do it over, and over, and over, and over.

And the reason that's actually happening in the stratosphere, it's in the sunlit atmosphere, ozone and atomic oxygen are exchanging with each other really quickly, so there's always some of both present anytime the sun is lit. At night the O goes away, but during the day, there's ozone... Breaks up as sunlight enough to make some O. So you can just drive this catalytic cycle over and over again and you can destroy hundreds of thousands of ozone molecules with one chlorine molecule, chlorine atom, from a CFC molecule, in the timescale that this stuff is in the stratosphere.

Lucas Perry: Right, and so I think the little bit of information about that is that the chloro in the chlorofluorocarbon meaning... That means chlorine, right? So there's these chlorine atoms that are getting chopped off of them, and then once they're free in the atmosphere they can be used to basically slice many ozone molecules, and the ozone molecules are heavier and more dense and so reflect more UV light?

Susan Solomon: No, no, no, no, no. Density and heaviness has nothing to do with it. The ozone molecule is just capable of absorbing certain wavelengths of ultraviolet light that no other molecule can in our atmosphere to any appreciable extent. That's why it's so important to life on the planet surface. It's just a really good light absorber at certain wavelengths.

Lucas Perry: Okay. And so at this point for Mario Molina and sorry, it's Sherry Rowland?

Susan Solomon: Yes.

Lucas Perry: And so for both of them, this is still theoretical or model based work, right? There hasn't been any empirical verification of this.

Susan Solomon: That's right.

Lucas Perry: So could you explain then how we move from these lab based models to actual empirical evidence of these reactions happening, and I guess starting with where Robert Watson fits in?

Susan Solomon: Bob Watson was a chemical kineticist originally, and actually had measured some of the reactions that we've just been talking about in the laboratory. So what people do is they go in the lab, I should have said this earlier, they go in the lab and they evaluate how fast individual chemical processes can happen, it's really very elegant work, and flow tubes, and lasers, and all that kind of stuff. And it's something that Watson was known for but he got an opportunity to become a leader of a research program at NASA, which he took up, and he became very much a leader in the community, as far as both organizing missions, field missions to go out there and look at things in real time, and more importantly perhaps, a huge leader in the assessment process which brought the scientists and the policy makers together. I think that you can really look at Bob as a tremendous founder of the whole way that we do scientific assessment, together with a gentleman named Bert Bolin, who has passed away unfortunately.

Lucas Perry: After Watson, could you then bring in how Joe Farman fits in?

Susan Solomon: Yeah, Joe Farman led the British group that discovered the ozone hole, as I mentioned earlier. So they noticed that their ozone over their station at Halley, Antarctica, it just seemed to be decreasing at an alarming rate. And they checked it with another station that they have, which is at a slightly higher latitude, not quite as far to the pole... I should have said lower latitude. Anyway, 65 South is where the other station is, I think Halley is about 73 South, it might be 78. And they found that there was ozone being lost at the other station too, just not as much. And that's when they decided that they just had to publish, so they did, and it attracted my attention along with the attention of a lot of people. I started working on what chemistry could possibly cause this, and what I came up with was that "Hey, maybe..." And we knew that there was no ozone hole over the Arctic.

We knew it was only over the Antarctic, because we had measurements from places like Sweden and Norway and Canada, if anything was happening, it was nothing like the Antarctic. So measurements in other places showed ups and downs, variability from year to year, but they weren't showing any kind of trend at that point. They later did, and we can talk about that, but we're talking about 1985 here, so really early. I was a young scientist, I was 29 at the time, and I decided that I was going to try to take my photochemical model and beat on it and pound on it and make it stand on its head until it produced an ozone hole.

And so I did that, and I figured out that the reason that it was happening was because Antarctica really is the coldest place on earth, and it's so cold that clouds form in the Antarctic stratosphere. The stratosphere is very dry, so normally there just aren't any clouds, but down in the Antarctic because it's so cold, the vapors, mainly water vapor but also actually nitric acid and other things can condense and form these incredible polar stratospheric clouds. And the clouds completely changed the chemistry, we can talk about that, but I think I've maybe gone on too long for my enthusiasm for which I apologize.

Lucas Perry: Hey this is post podcast Lucas. I'd like to add some more details here around the story of Joseph Farman's discovery of the ozone hole, to paint a bit of a better picture here. I'm taking this from the UC Berkeley website, and you can find a link to the article in the description: Dr. Farman started collecting atmospheric data at Halley Bay, Antarctica in 1957, sending a team to measure ozone levels and concentrations of gases, like CFCs. In 1982 his ozone reading showed a dramatic dip of around 40%. He was initially skeptical that this was an accurate reading and thought it must have been an instrument malfunction due to the severe arctic cold. He also reasoned that NASA had been collecting atmospheric data from all over the world, and hadn't reported any anomalies. His instrument was ground-based and only had a single data point, which was the atmosphere directly above it. Surely, he reasoned, NASA's thousands of data points would have revealed such a drop in ozone if there had been one. Given this reasoning, he ordered a new instrument for next year's measurements.

The following year, Dr. Farman still found a drastic decline, and going through his old data, discovered the decline actually started back in 1977. He now suspected that something odd was happening strictly over Halley Bay, leaving other areas unaffected. So the next year, his team took measurements from a different location 1,000 miles northwest of Halley Bay and also discovered a large decline in ozone there as well. With the same data at two different locations the mounting evidence for the ozone hole was clear and he decided to publish his data. This data both shocked and intrigued many scientists, including Susan Solomon, which thus catalyzed further research and inquiry into the ozone hole, the mechanism that was creating it, and the needed governance and industrial solutions to work towards mending it. Alright back to the episode.

Stephen Andersen: Let me just say one thing before we go back to the ozone hole. One of the interesting things that happened was of course, Farman and his research group declared that there was this serious depletion happening in Antarctica. So all the scientists that had been building the case with Sherry Roland and with Mario Molina, instantly jumped on it in the press, and in fact it was Sherry Roland that coined the phrase, ozone hole. He was the first person to utter that phrase.

And that was also a very good case that the public could grasp that, they could look at the NASA graphics, they could talk to scientists, and so there was really a great expectation that someday there would be the smoking gun like this and Antarctic ozone hole or other evidence, and people were ready and prepared to go to the press and go to the public, and in fact the politicians by this time had been briefed a lot, and that the United Nations they'd been working on this since 1970, when they organized a working group on stratospheric ozone depletion. So this great scientists and great science was welcomed into the community and they took full advantage of this and then other great scientists like Susan jumped on it to say, "Well, how can we go beyond simple finding of the ozone depletion and track it back to its origin, the CFCs and the other ozone-depleting substances." So it was science and politics at its best.

Susan Solomon: Yeah, I guess I also want to say that I didn't assume that the ozone hole was necessarily due to chlorofluorocarbons. I tried to produce it all kinds of ways with reactive nitrogen from the Aurora with dynamical changes. I just couldn't get it to happen any other way. And what we knew already, and again I think it's a real achievement, was that people had been interested in the idea of reactions on surfaces for a while, but mainly because they thought they were perhaps interfering with the measurements they were trying to make in those flow tubes. The flow tube is basically just a glass tube and people assumed that there was no surface chemistry that could happen in the stratosphere. We know there is chemistry on surfaces, in the lower atmosphere, in the troposphere, and it can be really important. Acid rain is a great example.

Surfaces can make chemistry do things that just doesn't happen in the gas phase. That's why you have a catalytic converter in your car, it's a surface that converts the pollutants into something else before it gets out the tailpipe. Surfaces lead to chemistry happening very differently from gas phase. And we assumed the stratosphere was just gas phase, there couldn't possibly be any surfaces. But interestingly, we sort of knew that there were these polar stratospheric clouds they'd been observed by explorers going back, I think 200 years in the Arctic and 120 or so in the Antarctic. We knew they were there, we just didn't really carefully evaluate their chemistry. But when people started doing these experiments in the laboratory, they thought certain processes were actually going in the gas phase. They saw, for example, certain kinds of chlorine molecules going away in their flow tubes, and they thought they'd discovered some new gas phase chemistry, turned out to be something happening on the surface.

And they said, "Oh, okay, doesn't matter. It's just on the surface." Well, it turned out to be not just on the surface of the float tube, but also on the surface of those polar stratospheric clouds. And that's actually the connection that I made. I thought, "Hey, if this is happening in the lab, there's no, necessarily, reason that it couldn't also happen on polar stratospheric clouds." Now that was a leap that perhaps I shouldn't have taken, but anyway, I did.

Lucas Perry: It's good that you did. Yeah, could you explain what that moment was like, more so. I mean, that was basically a key, super important scientific discovery.

Susan Solomon: Yeah. I had a very hard time believing it when I... This was back in the days when I was running a computer model. This was in the days that you would wait a long time for your output because things were very, very slow. I don't remember. I don't think it was still in the computer punch card day. I think I actually did have a file that I submitted, but the wait for getting it back, I think, felt interminable. And when I did get the results back, I was just shocked to see how ozone behaved. And one of the key things about it is that it doesn't happen in the winter. In the dead of winter when the polar regions are dark, this process won't be very important. You have to have not only cold temperatures so the polar stratospheric clouds are there, you also need sunlight to drive certain parts of the chemistry.

And I could go into the details of that, but I'm not sure you need me to do that. It's a process then that occurs in the Antarctic spring, as it comes out of its long period of dark cold winter, it's still cold, but the sun starts coming back. And that's the combination that then drives the ozone depletion. And that began to start happening in my model. So I was pretty shocked. It wasn't quite for the right reason, I have to admit. The process that I had driving that final step of... What I did identify correctly was that the key reaction is the hydrochloric acid and chlorine nitrate from the chlorofluorocarbons react together on the surface of the polar stratospheric clouds, they do not react in the gas phase.

We thought maybe they did at one time, but then we figured out it was just on the surface of the float tube, so we forgot about it, everybody, except until I remembered. And then the hydrochloric acid and chlorine nitrate react on the surface of those clouds that makes molecular chlorine CO2, which fertilizes breaks apart very readily with sunlight, that makes chlorine atoms, and now you're off and running to produce ozone depletion. So, that part I had all correct. What I thought was that the chlorine monoxide might react with HO2 to close the catalytic cycle. Cause you don't have much atomic oxygen in the lower stratosphere where the ozone hole was happening. You need to close that catalytic cycle, we were talking about earlier, with something else. Turned out that really the key thing is ClO reacting with itself to make something called a ClO dimer, which then fertilizes. But we didn't actually know that chemistry yet. We learned about it not too long after. That was discovered in '87.

Lucas Perry: I see. So, essentially there are these glass tubes and labs where the scientists at the time were trying to basically create atmospheric conditions in order to experimentally test the models that they were generating for what happens to ozone up in the atmosphere. And because it's a glass tube, there's a lot of surface on it and so they were discounting what they were observing in that glass tube, because they're saying the upper atmosphere doesn't have any surfaces. So, any surface related reactions don't really make any sense.

Susan Solomon: Right. That's basically it.

Lucas Perry: So, you were looking at that, what made you think that maybe there were surfaces in the sky?

Susan Solomon: Well I mean, we knew that polar stratospheric clouds could happen in the Antarctic and also in the Arctic. Like I said, people have visually... You can see them. I've seen them myself. They're clouds. They're actually very beautiful. There they look like they're almost a rainbowy kind of appearance because the particles are almost all one size and that creates a particular kind of beauty when the sun hits it. But yeah, you can see them, they'd been seen, literally. There were also satellite data that had been published a couple of years earlier that helped to inspire me to think about it. But I actually knew about the explorers, I was just intrigued by that kind of stuff. So then I was very excited to work with Bob Watson when we formulated a mission to go to the Antarctic and to actually go down there and make measurements that might help to determine whether reactions like that were indeed happening. And that happened in 1986.

Lucas Perry: Right? So you're creating these models that include the surface reaction. And so you've got this 1980s computer that you're submitting this file to, and... What do you get back from that model? And how does that motivate your expedition to go there and get measurements?

Susan Solomon: If I remember I had it programmed to make plots of the percent change in ozone, and there was this, I didn't call it a hole at the time, but there was this area over the Antarctic where once I put those reactions in, I got a lot less ozone. I recall something like 30% less. It's published in my paper that I published on this in 1986. So I wrote it up and submitted it to nature, and it was published in '86, and that was the same year that a lot of us began thinking about how to get down there and test the different ideas that have been put out because the idea of chemistry involving chlorofluorocarbons was not the only idea out there, other people had meteorological theories. And as I mentioned, there was this possibility that it might be solar activity, I guess somebody thought about, so the...

Scientists are always stimulated to come up with ideas, and we needed to get down there and make the measurements that could discriminate between the different ideas. So, I was very fortunate to be young and able to get on an airplane and go to the Antarctic. So I did, 1986. It was great. Most incredible scientific experience in my life, actually.

Lucas Perry: What made it so incredible, and what is it that you saw? What was your favorite parts about your expedition to the Antarctic?

Susan Solomon: Well, just going to the Antarctic is an unbelievable experience. I mean, even if you just go on a cruise ship, it's like another planet. It is crystalline, beautiful, unpolluted, full of optical effects that are just amazing. And of course, brutally, brutally cold. We went down in August of 1986. When I got off the plane the temperature was about -40°C, which is also -40°F. So I like to joke that if you're ever on Jeopardy and the Final Jeopardy question is, "At what temperature are Celsius and Fahrenheit the same?" The answer is -40. I'm originally from Chicago, I've been in cold weather, but I've never been in anything colder than I think about -15 before. And it was, it's a shocker.

But after a while, after a couple of weeks, -15 actually feels very warm. You really do. It's amazing how you acclimatize. Everybody laughs. Stephen's laughing as I'm saying this, but it's true, it's true really. I thought I would just kind of curl up in my room the whole time, but I didn't, I found that it was easy to acclimatize. Yeah, really. Well, actually people do. People actually even go jogging with shorts on, at -15. Yeah, it's incredible. Depends on if it's sunny or not. The atmosphere is very dry also down in the Antarctic. Basically, the cold has rung all the paper out of the air. So-

Lucas Perry: Did you go jogging in your shorts and T-shirt at -15?

Susan Solomon: No, no, I didn't do that. But I'd certainly remember feeling warm at -15 and opening up my jacket and stuff like that. And I definitely kept my window open if it was -15. So yeah, I did. But, I made some measurements with my colleagues using visible spectroscopy. So we use the sun, or the moon, or the sky as a light source, and we measured chlorine dioxide, which is a closely related molecule to chlorine monoxide, and we were able to show, particularly with the moonlight measurements, that the values we found were a hundred times more than they should have been. We couldn't measure them anywhere else because they were below our detection limit, but they were actually quite measurable in the Antarctic. So, that was the key measurement that we made and it was an incredible night, the night that we actually did that. And then, I think it was the next day that I made the data analysis and there it was. It was an amazing, amazing moment.

Lucas Perry: Could you explain more about how that particular data that you measured fit into the analysis and what it proved, and the feelings and experience of what it was like to finally have an answer?

Susan Solomon: First of all, there's the getting of the data which involves putting mirrors up on the roof of a little building in the Antarctic and directing the moonlight right down into the instrument. And doing that when it's cold and windy can be a bit of a challenge. So setting it up for measurement is physically challenging. And then taking the data, analyzing the data. I was, I think, careful enough to realize that that wasn't going to be the only thing it would take to convince everyone that chlorine was the cause of the ozone hole. The chlorine dioxide that we measured, had to have come from the chlorofluorocarbons. There was no other even conceivable source for it. And it was a hundred times more of it than there should have been, and that's because it had gotten the reactive species, and chlorine dioxide is a reactive form of chlorine had gotten liberated from un-reactive forms of chlorine, like hydrochloric acid and chlorine nitrate, which reacted on the surfaces of those clouds. And they don't do that anywhere else.

So that's a little more detailed than I thought you might've wanted, but that's why you take these, what we call reservoir species for chlorine, hydrochloric acid, and chlorine nitrate, and you convert them to active chlorine. And now you're really often running for ozone depletion. And that's what happens on those clouds.

Lucas Perry: You're getting this data about these particular chemical molecules, and then you're... Tell me a little bit more about the actual analysis and what it's like being in the Antarctic feeling like you've discovered why there is a potentially world ending hole.

Susan Solomon: Well, I'll tell you this, I was really careful, I think, maybe Stephen can correct me if he thinks some wrong, but I was pretty careful about not broadcasting the news before we were really, really sure. So the moon measurements alone were not enough to convince me. And one of the things that actually excited me a lot was when we realized we could also see this in the scattered sunlight that we got. If the sun was low enough on the horizon, there was even enough chlorine dioxide to measure it then. So what it is is a visible spectrograph, it's got a diode array in it, it's actually very similar to the diode array that reads the prices when you go to the supermarket today. Back in the '80s those were incredibly expensive because they had just been invented. And we had one that was cooled to very cold temperatures to keep it from having too much noise in it.

And we had a spectrograph, which you can think of as being sort of like a prism that you shine sunlight through, and you separate out the wavelengths of light and the colors of light come out as a little rainbow that you see when you put a crystal in front of a source of light. And so that's essentially what we're doing. We're putting a grading, in this case, a diffraction grading in the beam of the moonlight, and we're collecting the separated wavelengths of light on our detector, and we're looking for the absorption of atmospheric chemicals. And we can measure ozone that way, we can measure nitrogen dioxide at a different wavelength, but chlorine dioxide has a particular band structure in the visible, that is what we measured. And we can also see it. The fact that we could also see it in the skylight and that the difference between the skylight and the moonlight was consistent with what we expected from chemistry and consistent with what you would need to deplete the ozone layer, got me pretty excited.

There was another group on our expedition that measured chlorine monoxide using a different method on microwave emission technique, which is the same one that's used nowadays by satellite but in those days it was only used from the ground, and they also measured high levels of chlorine monoxide. And last but not least, I'll say that the following year in 1987, Watson organized another mission, which actually flew on airplanes from Chile down to Antarctica, and measured chlorine monoxide yet another way by laser resonance fluorescence onboard an airplane that actually literally flew right into the ozone hole. So, I would say fair to say that from the science community point of view, when all those measurements were in, people got pretty convinced, but they also had to be written up. I mean, it had to be peer-reviewed before something that important could really be talked about as a known piece of science. So I was very cautious about spreading the word too early.

Stephen Andersen: So if you look at the history of the Montreal Protocol, what you see is that in 1985, there was something called the Vienna Convention that was passed by the United Nations that had about two dozen members signed it. And this is what's called a Framework Convention that makes it possible to have something like the Montreal Protocol. So that was in the spring of 1985. And shortly thereafter, Berman published his article which was a tremendous reinforcement to the policy members that had anticipated that soon there would be evidence and that they needed to be prepared. And then as we went into 1986, and Susan is doing with her college, this brilliant work in Antarctica, the preparations are underway for the Montreal Protocol. And the scientists were telling the Montreal Protocol that it could be another explanation for the ozone hole, so that you should hold your fire until you're sure of the results.

And you can find that in lots of the accounts at the time. But by the time of the medium, September of 1987, there was still a lot of uncertainty. But the policymakers were able to talk to their national scientists and others and felt confident enough to go ahead and confirm the Montreal Protocol. So I would view it from my point of view and perspective, that it was a continuous improvement in the science and the threshold of belief occurred for different people at different times. But you could then say, of course there were still skeptics in 1987, but it was my experience that they were mostly gone by 1990. And so the work I was doing mostly with corporations, there was rarely a meeting where there would be science skeptics after 1990, that they were gone from the earth has moved on to climate, in fact.

So it was a tremendous contribution of science. And the other thing that's important to realize is that the industry that used these chemicals was not devoted to them. They'd been reassured by DuPont and others that they were completely safe and that there was no reason to worry. And then, as soon as the Antarctic ozone hole came along, they panicked and they rushed to the market to find alternatives. And that's one of the reason the Montreal Protocol happened so fast, is the industry in some ways was faster to grasp the science than even the policymakers.

Lucas Perry: Stephen, I'd love to bring you in here to describe, in particular, the transition from the discovery Susan was involved in to the Montreal Protocol. So, what are the steps between the discovery and the Montreal Protocol, and how do we eventually get to the Technology and Economic Assessment Panel that you co-founded?

Stephen Andersen: I'm glad to describe that. It's exactly what Susan said, is that there's a laborious process to prove the science, and then there's another process to communicate it. And that's probably partly what Susan did, and Bob Watson and another scientist, Dan Albritton. And they were masters of communication. And there were lots of meetings held between the scientists and the diplomats. But also the scientists and the companies, including the National Academy of Engineering, did its own review of the science on behalf of industry and came up with a confirmation report, I would call it no. New science, a narrow view of science, but nonetheless, it was the message coming from the people they most respected, and Sherry Rowland was involved in that and many, many others. So the communication was very quick. And in fact, I would say by January of 1988, you could see big changes.

So the protocols signed in September '87. In January of '88, there was a large conference, and at that conference, there were several important announcements. The most spectacular was that AT&T announced that they had found a nature based solvent made from the terpenes from oranges and lemons, pine trees that could clean half of the electronics equally or better than the CFC-113 had replaced. And they said that transition was technically possible within one year. So they went from skepticism and standing back to becoming the driving force. And it was also important because this terpene was not another synthetic chemical. It was naturally derived and harvested from the disposal of the orange rinds and the lemon rinds, and then put to positive purpose. So this was an eye-opener to a lot of people that thought you had to have an elaborate chemical to have an elegant solution.

And then at that same meeting, the auto industry step forward and realize that most of the emissions from car air conditioning was from servicing and from leakage. And so for the first time they got together a partnership that developed commercial recycling for air conditioning. They did that within one year and the next year after they confirmed and approved the technology, they sold a billion dollars worth of recycling equipment all across the world. So there's this enthusiasm of going from panic, that there would be high costs and disruption to the enthusiasm of profits and saving money. So it was the science that drove this, but it was the technical innovation that did this. And then very shortly thereafter, and in an overlapping way, there were similar breakthroughs in foam, so it was a commitment by the American food packaging institute to halt use of CFC in foam within one year, and to switch away from all fluorinated gases as quickly as possible.

So we've seen this building momentum and enthusiasm. You have international companies that are pledging to get out, and all the while we haven't reached the Montreal Protocol entering into force, because that occurs later after the signing. And when it was signed and the first big assessment which Susan was involved in as well, was done in 1989. And so this was an assessment that you alluded to, it included the Scientific Assessment Panel, it included the Environmental Effects Assessment Panel, and then it included the work on technology and economics. And this was the idea of how do you make the best available information readily absorbed by policy makers and business community.

Susan Solomon: But Steve, I would just add one thing that you already said, and that is, it all starts with people understanding the problem. You talked about the fact that people everywhere the public all around the world could look at these satellite images of the ozone hole and say, "Hey, that's actually pretty scary stuff." And that created the will, the political will, that generated the demand for all the products that you've just described. I think without people understanding the whole thing, nothing happens, personally.

Stephen Andersen: You're absolutely right. And in fact, in the case of that food packaging, it was a school teacher in Massachusetts and her children in the class that wrote to McDonald's corporation and said, "Why are you destroying the ozone layer?" So the people at McDonald's commissioned a survey of their customers, including children, and the customers responded, they did not want to destroy the ozone layer. And it made a big difference to where they chose to eat. And in the case of McDonald's, children drive parents to the restaurant, the parents say, "Where do you want to go today?" And they say, "McDonald's." So it was a huge impact. It was an eyes-open business decision. And they had announced, prior to the packaging institute changing, that they were going to stop the purchase.

Susan Solomon: Yeah. They were putting hamburgers in foam clam shells, and they switched over to cardboard, which is fine because McDonald's is so delicious. You eat it so fast anyway, you don't need the foam. McDonald's is so delicious. You eat it so fast anyway, you don't need the foam.

Stephen Andersen: That's right. Hot side hot, cold side cold, was the slogan. But this is exactly right. What Susan's saying is, you have this circular effect, where you have the customers pushing the companies, you have the companies pushing their suppliers, and you have the policy makers setting deadlines. And pretty soon, you've got this wheel turning very fast. And as quickly as you catch up with the available technology, then you look to the next strengthening of the Montreal Protocol. And that's what we saw over the decades of the Montreal Protocol, more and more chemicals control, faster and faster phase out.

Lucas Perry: Steven, could you explain more specifically what the Montreal Protocol was, and who the key stakeholders were, and how it came together and then was signed and ratified, and what that meant?

Stephen Andersen: So my role, I was very fortunate, because I was hired by the EPA in 1986 in preparation for the negotiations of the Montreal Protocol. I'm an economist by training. And so, I had the highest interest in showing that this was going to be cost-effective and feasible, and that the technology would come together. The mastermind behind the Montreal Protocol was the head of the United Nations Environment Program, Dr. Mostafa Tolba, who was a botanist himself and an accomplished author. And I think was very quick at grasping the science.

So you have the force of the United Nations organizing the meetings. And then you have the science that's providing the justification for the treaty. And then you have leadership countries that were advocates of a treaty. And that included a group that was called the Toronto Group, because it was partly stationed in Toronto, but that was United States, Canada, Norway, Denmark, many other countries, Sweden, that got together as a group and helped craft the language that they could sell to other countries.

And so, it was a masterfully designed document in retrospect. And included in that document was the idea of start and strengthen. So if you look at it, it only was two chemicals, CFC, and then a fire extinguishing agent called halon. And then the first negotiation in 1987, it was just to freeze the production of halon, stop it from growing, and cut back CFC's 50%. but that was not hard to do because 30% was still aerosol and convenience cosmetic products. So it was a very conservative start. But the science was so persuasive in the years ahead, that they said to the policy makers at the Montreal Protocol, that's not enough. You will not protect the ozone layer with those two chemicals. And you certainly won't with those modest reductions. So then they added more CFCs. They added carbon tetrachloride, metal chloroform, methyl bromide. A litany of chemicals were added. And then each time that they would meet, every two or three years, they would have an acceleration of the phase out.

So it was a very practical approach that was done on an international basis. And one of the beauties of this treaty, is it includes incredibly strong trade restrictions so that if a country did not join the Montreal Protocol, they would lose access to these ozone-depleting substances even before the phase out. So it had lots of clever features and lots of brilliant leadership. And what Susan said about people mattering, they mattered a lot over and over again. And there were 200 or 300 people that had a chance to become ozone champions and make a real difference to the world.

Lucas Perry: Could you explain who were the main stakeholders involved in the Montreal Protocol? Was this mostly developed nations leading it?

Stephen Andersen: That is a great question. That's a fantastic question, and explains a lot of why it was such a challenge. So if you look at the full set of chemicals that are controlled by the Montreal Protocol, they were divided into 240 separate sectors. So, distinguishable industry groups that had their own interests in keeping these chemicals or to phase them out. So if you look at those, and some other ones that Susan mentioned, the air conditioning and refrigeration, and that includes industrial refrigeration, because many chemical processes require that, and commercial refrigeration, and also what's called cold chain, the processing and the freezing and refrigerating of food in order for it to reach market.

So that alone would have been daunting. But in addition to that, there were these chemicals used as solvents in aerospace, in electronics, in the manufacture of medical devices. It was used as a sterilant. And as I mentioned, as an aerosol for metered dose inhalers. It was used in fire-fighting, including enclosed areas like on airplanes and submarines and ferries and ships and places that you can't evacuate if there's a fire, where you have to stay on board the burning vehicle. So it included all of the NASA satellites and the space labs and the rocket equipment. Manufacture of solid rocket motor for the space shuttle required methyl chloroform.

So you have these, and then the were laboratory uses. So it's used as a tracer-gas, as Susan mentioned. But also, it was used to have a dense gas for a wind turbine. And it was used for pressure check testing of scientific instruments to make sure there were no leakages of gases in or out. So as it got going, also, it was discovered that every weapons system in every military organization depended on ozone-depleting substances. All the command centers were protected with halon. All the ships, tanks, submarines, protected by halon. All the electronics and aerospace manufactured in service with CFC and methyl chloroform, all the gyroscope manufacturing for the weapons guidance. Whole list, all the way down. All the optical raiders, all the AWACS. Everything that they could look at had some use.

And so it required these stakeholders to look fundamentally at the basis of what they were doing, and decide how do you shift from using this chemical to a performance standard that would allow industry to compete as how they could produce an alternative that would be a pure replacement. And so, one measure that I think your listeners will find interesting is that if you ask the public today, or even the effective industries, no one has stories of train wrecks or disappointment or failed systems, because it was so successful. Most consumers would have their entire house changed, and they would not notice this. The glues they used to assemble furniture were ozone-depleting substances, but people have not stopped buying furniture. And so, if you went back, it's the smallest list of uses that found no substitutes. So it's quite remarkable.

Lucas Perry: Steven, you were on this panel, I believe the chair of it, for many years. So I'm curious if you could explain, more so, what that experience was like, what is it that you necessarily did on the technology and economic assessment panel, and what the impact of that was for implementing the solution that was needed after Susan helped to discover the mechanism of the problem?

Stephen Andersen: Yeah. Thank you for asking me that, because that's what I'm most proud of, of course. When I was appointed with Vic Buxton, from Canada, to set up the first technical panel, we were like-minded and we had a great idea, and that was, instead of casting out for experts from various sources and seeking wide participation and balance of interests, we didn't do that at all. We recruited the experts from the organizations that were already committed to protect the ozone layer, because these would be people motivated to find a solution rather than intellectually interested in describing solutions, or even worse, be a stakeholder against a new alternative, and they would become internal critics.

So the notion was that, on a technical committee, you could not have a better set of people than the people whose success in their enterprise depends on finding alternatives, and realized that a team could find the alternatives faster than others. The other secret of our success is, we had something called self affecting technical solutions. And so, for example, one of the chairs of the Halon Committee, studying halon, was the chair of the National Fire Protection Association that set the standards for where halon is used. So as quickly as a use could be eliminated with an alternative, he would go back to his committee and decertify halon on that use.

We had members of the coast guard on the committee. And as quickly as there were alternatives on ships, they removed from the requirements of the United Nations Maritime Organization the use of halon. So it went from compelling the use for safety to prohibiting the use for environment. So it was this remarkable internal group. And if you go back also, and you'll notice that some of the most important technologies were invented by people that only met on the committee for the first time. So you had groups of military suppliers that got together to tell the communication suppliers and invented something called no-clean soldering that eliminated the use of solvents and save the ozone layer, but it also increased the reliability of the products. And they were enthusiastic about commercialization to the extent that they patented the technology and then donated it to the public domain so it could be used anywhere in the world at no expense to the user.

So you have this enthusiastic group of genius engineers working on a short deadline and constantly resupplied with motivation from scientists like Susan, because as fast as they would take satisfaction in what they'd accomplish, they were being told, it's not enough. It's not enough to just do these chemicals. We have to do more. It's not enough to do these chemicals on the old schedule, we have to go faster. So some of these sectors halted their uses years ahead of the deadlines of the Montreal Protocol or the Clean Air Act. It was really quite inspirational. And most of those people would tell you, it was the best part of their life because they never would have been allowed to work with the engineers from the competing corporations if it hadn't been for the TEAP drawing those together for public purpose.

Lucas Perry: So, is a good way to characterize this then that there's this huge set of compounds, that when they get up in the upper atmosphere they release chlorine? And the chlorine is really the big issue. And so, these hydro chlorofluorocarbon are being used in so many applications. You've described a lot of them. And so, the job of this committee is to, one, slowly, through regulation, phase out this long list of ozone depleting chemicals, while also generating alternatives to their use that are not ozone depleting.

Stephen Andersen: Yeah. That's right. Generating or identifying. And there's a subtle problem we faced. It's now being faced again for climate. And that is, as Susan mentioned, most of these chemicals have long atmospheric lifetime. So when you stop producing the CFC, it can be a slow decline in the chlorine that's been contributed to the stratosphere over many, many years. Others of the chemicals like methyl chloroform, and most of the HCFCs have short lives. And so, any reductions you make in these chemicals that do all their damage within their short number of years has a bigger effect immediately than doing the same amount of effort on one of these other chemicals. And what the scientists were telling the Technical Actions Committee and the Montreal Protocol was that we had to worry about the long run and the short run.

And so HCFCs as refrigerants and foam blowing agents were viewed as a transitional substance. So if you stopped using CFC11 and you started using HCFC22, that was an improvement in both the GWP, and the forcing of ozone depletion. And the same thing for methyl chloroform. So the ambition of the Montreal Protocol was to work incredibly quickly to get rid of the short term chemicals and uses with an alternative that would be solvents, for example, using methyl chloroform, but at the same time, allow some HCFs so that you didn't have to endure the continued use of the CFCs. And that was the technical challenge, to keep your eye on the long run, and at the same time, keep your eye on the short run. And some of the scientists were also over motivating that kind of ambition, because there was a concern that we might go too far in sending chlorine and bromine to the stratosphere, and do irreparable damage, or damage that would take much longer to solve.

So, true or not. It was highly motivational. And it caused a tremendous effort on our committees, first of all, to get rid of methyl chloroform. If you look at the curve of methyl chloroform and the overall ozone protection, it was a critical first step. And it was accomplished probably in two and a half years worldwide.

Susan Solomon: So let me toot Stephen's horn a little bit. And then also clarify one point. I think the invention of the Technology and Economic Assessment Panel, TEAP, as we call it, of the Montreal Protocol was a real master stroke because it brought the engineers and scientists from industry into the process to help figure out what could be done. And so, the way the assessment process worked is, on a systematic basis. The science group that I was part of would assess the science. Steve's group would assess, okay, the science says, we got to phase these things out. What can we phase out? What is technically feasible?

And we would provide these reports, along with the one from the impacts panel, that would say if you keep doing this, you're going to have so many skin cancer cases a year by 2050 and stuff like that. All three of those reports would be explained to a group of policymakers in a UN meeting. So the decisions weren't actually made by Steve. But Steve's group was highly, highly influential in educating the policymakers and guiding them, really, on what would make the most sense, what could be done the most cost effectively, the most quickly, et cetera, et cetera. And then they made the decisions.

But the great thing about it is it's not a political group at all. In the old days, we would call them a bunch of guys with slide rules. And that included the people who came from industry. They weren't the political leaders of those companies, they were the people in the trenches trying to actually figure out what to do instead. And that's what made it work so well. I really have often wished that we had a similar way of doing the intergovernmental panel on climate change assessment process. We have a science panel that's pretty similar, but we don't really have quite the same technology panel. And many people have commented that the technology panel that Steve put together was just huge in making the Montreal Protocol work as well as it has. And the ozone layer is actually finally beginning to heal. So it's a real testimony to their success.

Lucas Perry: Yeah. Steven, please, I invite you to toot your own horn a little bit more here because your contribution was extremely significant towards the elimination of the ozone hole. I have a fun fact here that is from a paper of yours. So in 2007, Steven, you released a paper with Velders' team, published the importance of the Montreal Protocol in protecting climate. And the team quantified the benefits of the Montreal Protocol and found that it helped prevent 11 billion metric tons of CO2 equivalent emissions per year, and delayed the impacts of climate change by seven to 12 years. So please, what are some of your favorite achievements? And this is something you're involved in for decades.

Stephen Andersen: Yeah. That's a great story. And I'm of course, very glad to tell it. One of the things people know about me, that have worked with me for many years is, I worked by slogans a lot. So I try to reduce my ambition to something that's like a chant or a short instruction that I can give myself to move ahead. And after years of working with Susan and many other scientists and Mario Molina and Sherri Rowland, and struggling with these issues year after year, after year, and waiting for the science to come on board, and there'd be a missing link, and there'd be something that was misinterpreted, and we'd have to go back to square one. I came up with the slogan, science too important to leave to chance. And what that meant was that it was my job to say, what kind of information are the policy members missing? Those are the people I hang out with all the time.

Because at the same time, I was the deputy director for Stratospheric Ozone Protection at the EPA. I was the liaison to the department of defense on climate and ozone layer protection. So I was in those meetings where people were trying to decide, is it worth investing another millions of dollars in this new technology, or should we do something else? So in working with Susan in 1995 on a joint report between the IPCC and the tape, I realized that the Montreal Protocol had done a lot for climate that wasn't well appreciated over at the Montreal Protocol, that these facts were available. So I put together what we called a dream team, which included Guus Velders, who was the lead author, a brilliant scientist from the Netherlands. It included David Fahey, he was one of the colleagues of Susan at Noah, and John Daniel. And then it included Mack McFarland, who's a scientist who was once at Noah, but worked the better part of his career at DuPont. And then myself, who had been on the TEAP for oh, so many years, and then EPA.

So the idea of the team was to say, just how big was the contribution of the Montreal Protocol to protecting the climate, and how do we communicate that to the Montreal Protocol so they would consider that as part of their obligation and part of their legacy? Because we were coming up, my concern, we were coming up to a very long interval of HCFC in years, that the Montreal Protocol had plateaued its ambition. And they had accomplished so much, they were resting on their laurels, and they had lost this impulse to get more stringent.

So this committee was put together, it quickly put together all the facts, incredibly complicated at the time, although people have done work like this since confirming it. And this dream team came up with the conclusion that the Montreal Protocol had already accomplished more than the Kyoto Protocol could have accomplished if every party, every state government in the world had joined Kyoto, and if all of them had met its obligations. So this was huge. It was shocking to us. It was shocking to the world. We brought it back the same year, 1997, excuse me, 2007, to the Montreal Protocol. And that year, they accelerated the HCFC phase down.

So it was it a tremendous victory. And it was exactly what I would hope would happen, is if we assembled science in a new way that was headline news, that the policy makers would get the message and do something important. And then two years later, the same team decided, well, why don't we show the Montreal Protocol, how important it could be if the chemicals that replaced 15% of the ozone depleting chemicals, which are HFCs were phased down under the Montreal Protocol, ozone safe chemicals controlled by the Montreal Protocol. And that was accomplished in 2016. Took a decade. But we're very proud of ourselves. And I think it's a perfect example of the advantage of a group of people with a wide set of skills working together, including somebody like me who's not an atmospheric scientist, working with atmospheric scientists and making more clear what the policy makers need to know.

Lucas Perry: I'd love to pivot in here now into extracting some of these lessons that you're sharing, Steven, for how we might do better with modern climate issues, from greenhouse gases and also other global catastrophic risks. But I think you guys have done an excellent job of telling the story of the science and the discovery, and then also the strategic part, and the solution making of the story of the ozone hole. So as we get to the end of that, I'm curious if you have any thing else you'd like to wrap up on about that story. What is a key insight? When you look back at everything that you've contributed and been through, what is it that stands out to you?

Stephen Andersen: My theory of change, I think, is the same as Susan's, that people matter the most. That the ability to bring the right people together, at the right place, with the right instructions, is bound to have an important conclusion. And one of the things that I always found was, if you have the best engineers, no matter what their attitude, if they have the goal that is coincident of the environmental protection, they'll find a solution. So I think this accumulating of the science and the engineers and coordinating the activity, these assessment panels are just everything, that if you do that, you can't help but be successful.

But the other thing that I'm realizing now is that, when you're in a hurry, like we are with the climate, you have to take advantage of the existing institutions. So as quickly as we added HFCs to the Montreal Protocol, I would like to add other chemicals, N2O, nitrous oxide, which is an ozone-depleting greenhouse gas that was neglected by the Montreal Protocol. And then there's other gases like methane that have nothing to do with the sectors that are involved in the Montreal Protocol, but the framework of the Montreal Protocol might be perfect for a methane treaty. So you might have the Montreal Protocol people help design a methane treaty. Or if the Montreal Protocol can find its way to create new capacity with new skill sets, you could have methane drawn into the Montreal Protocol because it's genius is partly that you turn off the chemical at the source and force all the downstream changes to occur. And that's different than something like EPA, where you often find one part of the problem, catalytic converters and gasoline, and you implement that, but you're not focusing on the big picture, which is electrification of the cars.

And so, there's this inherent advantage of the Montreal Protocol, top down, turn off the chemical, bring on the technical information, bring people together for solutions, reinforce and reward. So I could go on for the longest time. I'm very enthusiastic about the success of the Montreal Protocol. I absolutely believe the lessons could be taken up better than they have been. And I think if they were taken up, we'd be well on our way in many other environmental problems.

Susan Solomon: Yeah. I like to tell students in my classes, and I feel like I've learned this over the years with Montreal, and I've seen it in so many other problems as well. There's three Ps that determine how well we do on any environmental problem. The first one is personal. Is the issue personal to me, to us? And in the case of the ozone issue, it was deeply personal because skin cancer. I mean cancer, it doesn't get any more personal than cancer, right. But also all the other attendant things that it can do. The second P is perceptible. Is the issue perceptible to me? The best case is if I can see it with my own eyes, like smog, but seeing the satellite images that we talked about earlier, that was good enough to make it perceptible to a lot of people. And the third big P is, are there practical solutions? And that's where Steven's type of work has been so important. So when you think about climate change and you think about the three P's, people haven't really considered it personal until pretty recently because it seemed like a future problem, not a today problem. And we can talk all we want to about caring about our grandchildren, but really what we care about is us, right?

So, and we do care about our grandchildren. Of course, we do, but not as much as we care about us. That's just a fact, I think. It's natural and normal and we don't need to be embarrassed about it. Particularly when you're talking about a future problem and you can always hope that there'll be other solutions in place by then. So is it personal? For a long time we thought it wasn't. Is it perceptible? For a long time we didn't feel like it was. Nowadays, I would say more and more people are recognizing it as personal and perceptible. The kinds of things that have happened in the world this year have just been amazing. And being wake up calls because so many places have flooded, so many places have had massive fire. These are all the sorts of issues that we knew were happening. So much erosion is going on because of rising sea levels.

People are just, and actually when people would say to me, well, it's not really perceptible yet. My answer to that would be, yeah, I know. And it's a problem but it's going to fix itself with time. And I think we're just about there. It has fixed itself. And then there's that big third P is, are the solutions practical. And there's been a lot of propaganda out there saying the solutions are not practical, but I think we're reaching the point now where we recognize that they are. So I think that we're really at a turning point on climate change.

Lucas Perry: I'd love to pivot here more into exploring lessons to extract for what we can do about climate change and other global catastrophic risks for the theory of change about what we might do about those. And I'm also mindful of the time here. So if we could hit on these a little bit faster, that would be great. One thing I don't think that, or one thing I would like to hit on more clearly is what is the bad thing that would have happened if the work of you, Steven, and the work of you, Susan, and all of the others who were involved in the discovery and solution towards the ozone hole, what is the bad thing that would have happened if we had just continued to use CFCs?

Susan Solomon: There is a lot of work on that now, people call it the world avoided scenarios. So what world did we avoid? Well, by mid century, it would have been about a degree hotter than it's actually going to get. So that's a degree Celsius by the way. So instead of a degree from, a degree in AF from mainly CO2 and methane that were trying to avoid, we would have an extra degree on top of that from CFCs that we would have had to avoid. That's a big deal. Something like 20 million skin cancer cases in the United States sticks in my mind by mid century, but I would have to check that number to be absolutely sure.

Stephen Andersen: Yeah, Susan's absolutely right. The latters can cancer cataract, but one of the things you can look at is you can say two interesting things. You could say, what if Molina and Rowland had not had this hypothesis? And certainly you could say, well, someone would eventually. But if it had been five years later, or 10 years later, it would have been catastrophic because it did take time as Susan said. It does take time to make a hypothesis, to confirm it, to do the ground measurements, to do the aerial flights and so forth. So it was just in time or a little bit too late that it was really a tight schedule that was working when you include diplomacy and corporate changes and all of those facts. But you can also look and say, what if the Montreal Protocol and Molina had been delayed some period of time.

And what you can see is exactly what Susan said, that the CFCs would have grown in climate forcing, let alone ozone depletion to a level that would have been untenable for earth. That they could have been almost the same level as the CO2 climate forcing. So we were incredibly fortunate to have this early announcement. It was incredibly fortunate that the Antarctic ozone hole was noticed finally, and announced and it was such a spectacular persuasion. And then fortunate that the Montreal Protocol was able to take this and then in a derivative that the corporations were able to make their reductions. I also think it's important to remember that this really was a training ground for a lot of people, that scientists had not worked together successfully on assessments this large and so continuously brilliant over so many years. If you look back at each of the assessment panels, I find almost no valid criticism of any of the findings at any of the points in time that this was a well done process, actually stunning.

So the World Avoided, if you read the Nobel Award for 1995 for Crutzen and Molina and Rowland, it says that life on earth would not have been possible as we know it. If you read Paul Newman's report on World Avoided, you find out that it would have been untenable to go outside at most latitudes for very long, without sun protection, far beyond what people wear when they go out today. So it would have been a lot of joy taken away, a lot of misery brought on by these medical effects. And it would be a less successful world because these technologies that replaced the ozone-depleting substances are purely superior, better energy efficiency, less toxic, more durable, more easy to repair and reliable. It's quite a success story.

Lucas Perry: So let's explore these P's as Susan has put it. So we have the issue of greenhouse gases warming the climate today. And a lot of what you were involved in Steven was the economics of making transitions. So both the innovation required to replace HFCs and then also the questions around that being economical. So this is the importance also of industry being involved in the process. So I'm curious if you could explain your experience with industry and how difficult or easy it was to get industry to make this transition and how that compares to the transition that industry and governments need to make in the modern day around climate change. And how much of that difference is a bit circumstantial around the technologies and innovations that need to be made.

Stephen Andersen: Yeah, that's a great question. Susan, I think agree, and I agree that some of the stakeholders on the climate side were more persistently ruthless than we've experienced under the Montreal Protocol. The early days when Molina and Rowland came up with their announcement, they couldn't thought to have been more ruthless. Character assassination, there were lists of people that were not to be hired. The region said the University of California prohibited Sherwood Rowland for applying to certain organizations for funding and on and on. But if you look at what's been done by the coal companies and petroleum companies, I think that that was orders of magnitude worse over a longer period of time, including interjecting a lot of wrong science over and over again, which was a terrible distraction and also took a lot of energy away. So there's no doubt about the differences of the two. But what I have found out working on ozone layer is even sectors that have a bad reputation for other topics can be leaders on a topic once motivated as Susan Solomon says, and come to regret what they're doing.

I'll give an example. The automotive industry was among the most rigorous in getting rid of their solvent. Their foam uses, foams and cars include what are called safety fonts. So the, under the dash of the car originally, it was underneath the surface of the fabric, it was all ozone-depleting substances. It was all ozone-depleting substances for the refrigerant, for the solvent to make the components for the electronics and so forth. But they looked at science, they got motivated, and they stopped using these chemicals as quickly as the other sectors. So they were one of the fast to go. So what my lesson is you shouldn't judge a book by the cover. You should not hold it against an institution because they misbehaved in the past and you should give them a chance to make a new start on leadership right now.

The other thing I would add is the public right now is much more engaged in climate than they ever were in ozone layer protection. So if you go back, there were very few of the industry projects that had active involvement of non-government organizations, environmentalist, because it was being done so well by the companies themselves that would have been futile use of those talents. But you look today, there are thousands of organizations that are demanding changes in industry. They're in the streets, they are protesting. This did not happen for the ozone layer. It was the smallest amount of activity. So there's the difficulty of the fossil fuel industry, but it's offset by the ambition of the non-government organizations and some of the governments. So lots of things are happening there. What would you add Susan?

Susan Solomon: Well, I think you summarized it pretty well. I think the other thing I would add is the engagement of young people today, they have been exercised and have become pretty upset about the future that they see themselves inheriting. Greta Thunberg has done a fantastic job I think of mobilizing worldwide in a sense. The ability to get together on things like the tools that we now have with the internet have allowed that to become an international movement much more effectively than we could have ever done in the 80s for climate. No matter how concerned we were, the telephone only worked so fast. So I think you see a public engagement on climate change that is driving a lot of what's going on and having a huge influence.

Lucas Perry: Is there anything that you both wish or would suggest as actions or things that are really important for the generation? The generations that face climate change. What it is that they need to understand and do. I mean, we're talking about making things practical, personal, and then is the last P perspective?

Susan Solomon: Personal, perceptible and practical.

Lucas Perry: Yeah, and so there's still this, I mean, a large problem also beyond these issues, global catastrophic and existential risk issues, beyond making them personal. And there is certainly difficulty around making action around them practical. With the last P for perceptible, a lot of people don't even agree about the science of climate change. So I'm wondering if there's any similarities between that and what you experienced with HFCs, and what you suggest there is to do about that. I mean, because the climate issue has become politicized, certainly.

Susan Solomon: Yeah, I mean, I would argue that it is becoming perceptible. I think most people around the world have noticed that the summers are hotter than they used to be. That heat waves are more extreme than they used to be. So perceptible is not so much the problem anymore I don't believe. What is the problem is the practical, that they believe that it would cost too much and that it's not practical to do it. That is increasingly becoming less and less tenable when it comes to power plants, for example. It is, nowadays if you're going to build a new one, it is cheaper to do it with solar and onshore wind than it is to do it with either coal or gas. And so, and nuclear of course, too are more expensive. So there has been a pivot in the power industry to renewables that's been very rapid. I think that we need to put a lot more investment into that because it does take an upfront investment.

It's true that when it came to some of the things we could do for the ozone layer, a lot of them were really, we were getting rid of things that we didn't have a deep investment with. I mean, how invested are you with your can of spray deodorant in your medicine cabinet? Probably not very, you can throw it away and or maybe you can even use it until it runs out and then go out and buy a roll-on, right. But probably a lot of people went out and just bought the roll-on because they figured it was a very good thing to do for the planet. But so this is indeed a lot tougher because of our investment in existing infrastructure, some of which is tremendously expensive. But I don't think there's any real barrier to making the transition.

And as soon as those things become... As soon as the alternatives become cheap enough, they essentially pay for themselves because energy drives everything. So if we can make energy more cheaply with solar and wind, then the cost of doing absolutely anything that requires energy becomes automatically cheaper too. And that makes a sort of a snowball effect of greater and greater demand. We need to make our grid more robust to things like intermittency and able to transmit electricity over broader spatial ranges. That is doable. It's not, other countries have already done it actually. So it's not something we couldn't do. There's a lot of things that are beginning to really happen quite quickly. And I'm very optimistic, but we do need some real changes in our existing infrastructure. There's no doubt about it.

Stephen Andersen: Yeah, so there's two things I would add. The first thing is the United States is now behind the rest of the world on barrier removal. So in Europe, you can use technology that's been in the market for five years now, absolutely proven safe and effective energy efficient that's prohibited by the USCPA for use in the United States. So they are a wall against new technology where they used to be a door. And so somebody has to get in there and motivate and get approval.

Susan Solomon: Can you give an example?

Stephen Andersen: Example, there's a refrigerant called HFC32 that has a third of the global warming potential that has 20% higher energy efficiency. It's mildly flammable, but it hasn't been approved in the United States. Similarly, there are natural refrigerants that have not been approved. And if you look at the timeline and another example, which is easy to understand is they approved years ago, a decade or more ago, a chemical that has a GWP of less than one to replace HFC134a, which has a GWP of 1,300. This was allowed for light trucks and cars. But the industry at that time did not apply for what's called highway trucks to big trucks that move cargo and off-road vehicles like farm tractors and construction equipment, mining equipment, forestry. And that the industry applied months and months ago to have this year's further equipment.

There's no difference in using it on an off-road equipment or an on-road equipment or a big truck or a small truck because the cab of a big truck is about the same size as the interior of a car. But for some reason, the EPA has not finished that process, which is now way beyond the statutory limit of time. And they say it's because they just haven't had time to do it. Well, this is not acceptable. You have to have a government moving at the pace of industry. And then the last thing, probably important, the United States military and military organizations all over the world we're a part of protecting the ozone layer. So far that's not the case. If you look at inside at the documentation of military organizations, they say it's a force multiplier, it makes everything worse in national security. They say it's an amplifier of conflict. There's tremendous concern about the displacement of populations and immigrants across borders and distractions from security because you have to do humanitarian relief. That's all in the documentation.

But so far, all they do mostly is to do resiliency of their own facilities. So they're doing what they need to do to protect against the effects of climate change, but they haven't engaged yet in stopping climate change, which is much more cost effective. The last thing you want to do is let climate change happen and then try to run away and hide and build against it because that's brutally, brutally expensive. So I think those two things, if we were more aggressive on approving new technology, and if we had the military organizations involved as part of the skill set and part of the solutions and so forth, I think we'd go a long way.

Lucas Perry: As a final question here, so Steven, your panel, the technology and economic assessment panel was super successful in this strategic and coordination front on the technology and the replacement of the technology, which is something we're also just exploring. Does the Paris Climate Accord have anything similar? And do you see a panel like this as being something also that's crucial for the climate change crisis and also the governance around other global catastrophic and existential risks?

Stephen Andersen: Yeah, I think you're right. And Susan and I have both tried over many years to get the climate convention to do something like the tape. Recently, I realized that if you don't want to wait for the IPCC to do this, you could do it as a shadow chip. And that it's very easy I think for an individual sector to organize itself under the same principles of being objective and including members that have the coincidence of interest in changing the market and changing the technology. You could put that together within an industry and then bring forward the solutions that you'd like to see implemented. And this is almost happening in Europe right now because they're phasing down HFCs much faster than the United States. And they're doing it on a sector by sector basis and they're involved in the stakeholders. And the stakeholders have figured out that if they come to the EU with a single plan that cuts out their share of the goal, that the European Union will approve that. If they come in with separate views and lots of disagreement, the EU will choose their own plan for them.

So they have two choices, do it their way or do it the government's way. And so far, they always chose to do it. The practical cost effective technology that they understand the best. And that's exactly what the team did. So I'm very enthusiastic about that model. And in fact, that's where, if I were an industry, that's where I would put my money right now is I try to say, how do we become the leaders on this so that these activists that can cause mayhem in our company would say no use messing with that company that shows an in-state runs, let's go bother someone else. Let's let them solve their problems and we'll go on to a recalcitrant truck sector and to give them bloody hell. I think that's a very persuasive argument.

Lucas Perry: All right, Steven and Susan, thank you so much for coming on. If you have any final words for the audience about climate change, the ozone hole and existential risk, here's a space for you to share it.

Susan Solomon: I hope we've given you some hope in this period of talking. I mean, it's easy to become kind of despondent about climate change because there're terrible events making people suffer day after day. On the other hand, I really do believe there's light at the end of the tunnel. I think the ozone issue demonstrates that. And I think we are on the road to getting to a solution.

Stephen Andersen: Yeah, I would just add to that that organizations like Future of Life Institute are a tremendous part of the solution. I do believe that recognition and explanation and all of those things make a big difference to getting people motivated, to take on this very hard work. It's work you love when it's over, but it's always hard while you're doing it. So we have to have the highest motivation possible. And you folks are part of that solution.

Lucas Perry: Well, thank you very much, Steven and Susan, for coming on the podcast and also for your scientific and strategic coordinations to a global risk in our lifetimes.

Susan Solomon: Thank you, Lucas.

Stephen Andersen: Thank you very much.

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