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Interview of Tony Cox by Keynyn Brysse on 2009 March 16,
Niels Bohr Library & Archives, American Institute of Physics,
College Park, MD USA,
For multiple citations, "AIP" is the preferred abbreviation for the location.
In this interview Tony Cox discusses topics such as: ozone depletion; the Atomic Energy Research Establishment; chlorofluorocarbons (CFCs); stratospheric research; National Aeronautics and Space Administration (NASA); Robert Watson; World Meteorological Organization (WMO); Coordinating Committee on the Ozone Layer (CCOL); F. Sherwood Rowland; Mario Molina; carbon dioxide; Montreal Protocol; Airborne Antarctic Ozone Experiment (AAOE).
Let’s talk about your involvement with ozone depletion science and assessments.
I worked at the atomic energy research establishment at Harwell, and we were under contract with the UK Department of the Environment, which was only formed in 1974, and they took over responsibility for air pollution research. As part of that they took over responsibility for the CFC issue, which had actually been raised by Sherry, Rowland, and Molina in a paper in nature in 1974. So it landed on the desk of the government department, which we were already talking to about ordinary air pollution near the ground, which I had been working on. In fact prior to that, the stratospheric pollution issues in the UK were handled through the Meteorological Office. We weren’t involved in that science, although we knew scientists that were involved with it as part of the UK group. There was a group at Oxford doing that as well. So basically, I got into it at a fairly early stage because of that contract we were on. I met Bob Watson in about ’77. I’d actually met him at a science conference before that, but I think it was in connection with the setting up of what was then the co-data panel, which did the evaluation of the kinetics and photochemistry data that went into the models that we used for calculating the ozone loss.
Bob Watson told me I should ask you what those periodic co-data assessments were called because he couldn’t remember the title of the report that would come out of it.
I’ve got the original one here.
Great. Also, he couldn’t remember when they started coming out.
This is the first one so it was 1980. It was printed in the Journal of Physical Reference Data. The group was called the Co-data Task Group on Chemical Kinetics. Just to fill you in a little bit to the background of that, at about the same time that this was set up, NASA took on the responsibility in the US for doing the stratospheric research, although it took awhile. There were several organizations funding stratospheric research in the US. One of them was the FAA, the other one was the CMA, which is the Chemical Manufacturers Association, and then NASA was given task to essentially do it as well. They were all fairly well-established programs in all those organizations. But NASA set up a data evaluation panel of their own. I think it was felt because the issue was international, and the data at that time, which was before that had any real measurements of ozone in the stratosphere that could be used to say anything about the impact of the pollutants, basically relied on these chemical models by which the behavior of pollutants and their impact on ozone was calculated. It turned out that the ozone depletion was extremely sensitive to the chemistry, so it was quite an important issue whether the chemistry was right and whether the numbers that were put in the models for figuring the calculations was right. So this was a major issue. They basically set up two panels. One was this one, and the other one was set up in the US. In fact there was some cross-membership of the panels, Bob Watson being one of them. The other one who was on both panels was Bob Hansen from the National Bureau Standards. That’s how this was set up. We had our first meeting in 1997, and we produced this data book, which is somewhat more elaborate than the NASA book. It was more of a handbook than a list. NASA was more of an annotated list, but this was more of a handbook. The basis of the evaluation and the recommendations was more — well firstly, there were more cited experimental data in these, and secondly, there was more discussion about the rationale behind the numbers. But this is not to say that this was any better than the NASA because in fact they basically often came up with the same picture. But not always, and it had some quite interesting dynamics when there was the disagreement in what should be presented.
When you say different recommendations and evaluations do you mean, “Use this rate for this reaction when you are trying to…”
Yes. That’s the bottom line of it for the calculation of the atmospheric was the number and the actual reactions, which the number applied to. And there was in some cases where it was equivocal. The experimental data was not good enough to decide exactly, and then you had to essentially make an informed guess about what was going on, and that may not always come out the same from the two panels.
There’s not enough computer power at that time to run a model with all of the possible rates for all of the possible reactions.
It depends how big the model you put in. You could in principle do a simplified model many times, but it was not considered a really — I mean there were attempts to do these type of vary the constants and see how the calculation sensed it. But generally it was pretty sensitive to these things, so if you put another number in you get another answer. It was quickly realized that the important chemistry had to be pretty certain if you were going to have any confidence in the model, and if it was going to have any predictive power. That’s how it turned out.
You’re working at a lab measuring these rates?
Yes. I had a small group and we did measurements of right constants. We put them in the pool along with everybody else’s, then we’d periodically get together and discuss what the best values were, and then they would be put into a list of recommendations. That started at this time, and there were a few major changes that took place in the early years. Ultimately it started to stabilize as the data got better and the techniques — there was a very big stimulus to improve the methods for doing these measurements in the laboratory. That led to a much improved collection of knowledge on which to do the ozone process.
Was some of the pressure coming from the fact that policy-makers wanted to make policies about regulating ozone and therefore they needed to know what was going on? Or was it just about getting the science right for the sake of science?
I think it was essentially driven in the direction of getting the best possible scientific answer by the realization… well, by the belief of some of us that this was a problem that was potentially really serious, and that we wanted to get to the bottom of it. When you first come to look at these problems, the idea that — you have to remember that in the ’70s the idea that human activities could effect the global atmosphere was really quite radical. It was generally believed that pollution was a local thing, and the idea that you could actually impact the whole atmosphere was a completely new idea. A lot of people didn’t believe it. A lot of scientists didn’t believe that it could affect the whole atmosphere. But then as the science evolved and you realized that what goes up, if there isn’t anything to take it away, will build up. Do the sums, quite simple sums, you can show you are in trouble if you have something that’s not being removed from the atmosphere and it’s starting to affect some remote part. That was the position at the end of the ’70s. People were working quite hard to understand some of the reactions. With some observational data, which came from the early satellite instruments, which showed, for example, the presence of nitric acid in the stratosphere, nitrogen oxides in the stratosphere, which had originally been proposed as participating in the SST story. In the UK, in these early days, this is pre-ozone hole I’m talking about; we had a group that was looking at it independently from the NASA group. That was quite a high-powered group. In fact, some of the people in that group included Michael Klein, who died rather young. He was the supervisor for Bob Watson’s PhD, and he was the guy that did some of the fundamental measurements of the elementary reactions that were involved in the ozone depletion story. His experiments done in the late 1960s and early 1970s in the lab in London, Queen Mary College, were the fundamental things that gave the idea that you could get this catalytic depletion. We had a group that was interested in the problem here. We produced a report in about 1979 to the UK government summarizing what we thought and what the potential for ozone depletion was. I would say that the quality of the work was — it was done in an international dimension. We communicated with the people in the US, and we all had models that ran alongside the American models. I think we were all quite convinced it was a serious problem, which we should keep pushing forward.
Did it convince the government that you submitted it to?
Yes, I think they took it pretty seriously actually, yes. Through the government connections, we did have dialog with the industry, we had periodic meetings with the industry. We were also coupled with fluorocarbon producers in America. Because ICI in the UK was one of the largest producers. One of the big issues at the end of the ’70s is that okay, if you can’t use the CFCs what are you going to use for some of the applications? One of the molecules that was being used was 1, 1, 1-Trichloroethane which is methyl chloroform, which you’ve probably heard of that. ICI was a big producer of that. But on the face of it, because it’s sort of removed from the atmosphere, it was thought initially and naïvely to be okay. But the huge production of it and the relatively long lifetime in the lower atmosphere meant that it was potentially a big ozone depleter. ICI looked at this and they made a decision to actually go ahead with large-scale methyl chloroform production at the end of the ’70s. It was to some extent a judgment made against the advice that the scientists gave them.
I was going to ask about that. When you met with ICI people did you find them receptive to…?
Yes. They were very serious, and they really did have a pretty strong team on this problem. Good scientists, and we had a very good dialogue with them. Obviously their business managers didn’t consider it was important enough to change their plans.
So the problem wasn’t the scientists.
No, I don’t think it was. The other thing I should say about the methyl chloroform thing, which we were very heavily engaged with in it in our group, because it was an issue, which involved the lower atmosphere, which is where we had come from. We were pollution people, and we actually had one or two people, myself included, who were interested in global tropospheric chemistry, the lifetimes of the more reactive halogenated compounds in the troposphere, which is something I’m still interested in. This side of it has been a lifelong interest. By the early ’80s, we were fairly well engaged from this point of view, and involved in the international discussions. I had been along to the WMO. They had an ozone convention that was set up in the 1970s and there was a committee called CCOL, which was a WMO committee, a joint UNIP WMO committee. I went along to quite a few of those meetings as a technical support for the official UK representation on the CCOL. It was quite interesting to me as a young scientist getting involved in the political side of it and drafting the statements. So you got to realize how the politics of regulation, or potential regulation, and what was said from the scientific community was pretty important. You had to be sure that you were saying the right thing in the right way to actually have the impact you wanted. But then there were always people that didn’t want it said that way — countries had different agendas on this.
Did you find that the CCOL was a useful body? I’ve read about it in a few books. I think it was Parson who says the CCOL tried, but they didn’t have long enough meetings often enough, and that there was no government or official body that had to accept their report and act on it.
Yes. I suppose with hindsight you might say that. There was no proof at the time that this was going to happen. I think people thought we had more time. Because the science was becoming more complicated, the basic proposal was modified and the various developments in the science, and it wasn’t really clear that the ozone layer was going to be destroyed by this mechanism at the rate it was going. They effectively were looking at column ozone and skin cancer and these sorts of things. I think that people thought they had more time. There wasn’t really anything measurable until…
I was on the first Blue Book. That’s where the CCOL effectively changed to the leadership that led to the production of the Blue Books.
The first one is 1981, or do you literally mean the ’85 Blue Books.
No, I mean 1985. The 1985 Blue Book, which was effectively the first international assessment of the ozone issue, and it was just prior. In the final versions of it, there were — well, certainly in the chemistry chapter, which I was the chairman of that time, there were a few things indicating that the polar regions might be different.
As they turned out to be.
As they turned out to be. There was nothing to say that this huge perturbation was going to occur.
I can’t remember; does it talk about polar stratosphere clouds at all?
I think it did. I can’t remember the guy who did that. [Per Cambridge Seminar, Pat McCormick]. There was a satellite that saw them.
I think there was a paper in ’82.
The extent was clearly quite a large extent. Then there had been, at the same time, the suggestion that there might be this heterogeneous chemistry on surfaces which led to the redistribution of the chlorine from the reservoirs into the reactive vaults.
Where are those suggestions coming from?
I think Sherry Rowland was the first to say, “Hey look, we can react chlorine nitrate with HCL in a glass tube and it makes chlorine.” That gossip was going around the scientific community, but there was no real impressive publication of it. Sherry did pretty crude experiments in the lab by and large; he wasn’t really at frontier science in the lab. He was well known as a good scientist, but his stuff in this area was rather quick experiments, because by that time he spent a lot of his time on the hoof around the world promoting his hypotheses. Neal worked with him at that time. Then he started doing the measurement program, which is what Neal use to do.
In Molina and Rowland 1974, the very last paragraph of the paper they say we haven’t looked at heterogeneous reactions and they might turn out to be important, so we should keep that in mind. I’m obviously paraphrasing. I thought before I talked to anybody that meant they were suggesting somebody should look at heterogeneous chemistry. Rowland said actually he just brought it up to dismiss it. He didn’t think it would be important because he didn’t know there were any particles in the stratosphere. When I talked to Paul Crutzen, he said he always knew there were sulfates in the stratosphere.
That had been discovered back in the ‘60s.
It was his predecessor at the MPI in Maines [?], he said.
Yes, Christian Junger.
He said, “Well, there weren’t many of these sulfates.”
Firstly, they were in the wrong place.
They were too low. The amount of them was tiny.
Yes. Too low and too few.
You could do simple sums on heterogeneous chemistry in the free atmosphere, and really even in the higher parts of the troposphere — the surface area — once you get away from clouds, water clouds, then the surface areas are so small that they’re not really…
So it’s not that no one knew about heterogeneous chemistry or that no one had thought about it.
That’s true. It isn’t that nobody had thought about it, but a simple-minded looking at the problem, knowing the fluxes through the gas reactions and the photochemical reactions, they were so huge compared with what you could get even for the most efficient processes taking place on the small particles. It was generally held that the heterogeneous reactions in the atmosphere were largely confined to liquid water droplets in clouds where you have got a large body of condensed material, and it was limited to the types of reactions that would operate in cloud water.
That changed when people realized the extent of the polar stratospheric clouds?
Yes. The extent of the polar stratospheric clouds opened the way that you could have — If you could find a heterogeneous reaction that was fast enough and did things that were relevant, and then it would be potentially important. I think that it was about that stage in the first Blue Book, the 1985 assessment, the words that were in there were sort of hinting that was the case.
I seem to remember reading that. Then right after that Joe Farman discovers the Antarctic ozone hole. It’s a very unusual thing that no one had expected. And so one must look for unusual chemistry to explain it and you start considering heterogeneous reactions.
Yes. I think that’s what it was. In fact, the heterogeneous reaction that was proposed came out of an experiment that Sherry Rowland had done around 1982. It was in a glass bulb, and the idea that this may occur on an ice surface was really quite radical. Then we did some experiments in our lab that showed this could occur on a glass surface. But to actually measure reactions right on ice surfaces is much trickier; nobody knew how to do it at the time. It took a little while to get any kind of quantitative data. Really it wasn’t until ’88 I suppose that anybody got any quantitative data that would give you some confidence that this is what was going on. The other thing about it, looking in perspective of the chemistry point-of-view, the kind of reaction that occurred was really extremely unusual in chemistry. Most of the heterogeneous reactions took place in the lower atmosphere, in the cloud droplets. They involved oxidation of compounds into more stable forms that could be rained out. A lot of the thinking about heterogeneous chemistry was the conversion, for example, of sulfur dioxide to sulfuric acid. This reaction is quite a strange one where you take two different kinds of chlorine species (two chlorine compounds) in two different oxidation states, which react together and produce a new chlorine compound in a neutral oxidation state that is molecular chlorine. The other bit being nitric acid, which is where chlorine nitrate and nitrogen goes into. These are quite unusual types of reactions — they are really odd. They had been discovered before, but it was never really thought that they would be rapid in the atmosphere because they’re two closed-shelled molecules and they shouldn’t really react quickly. There was this driving force with this particular strange reaction, and there turns out to be quite a number of examples of it in the chemistry of the halogens. We know now that it applies to bromine, chlorine, piadine — the chemistry of those things in the atmosphere is dominated or is affected by these strange reactions.
Another thing about heterogeneous chemistry is that it can be really difficult to measure in the lab. And even if you measure it, you’re measuring it on laboratory surfaces, glass bulbs, bowls and beakers and things, so you’re not sure how that applies to the real atmosphere. Given those things and given that before the Antarctic ozone hole and the polar stratospheric clouds, even if there was heterogeneous chemistry going on it would have been a very, very minor component compared to the gas face chemistry. So it just made no sense to look into it.
Well, you apparently didn’t need it to explain what you saw. From what we did see, it was largely explicable, and it would be considered to be small perturbations at the edges, so to speak. I have to confess I was strongly of that opinion. The atmosphere is complicated enough, so I felt that you didn’t really want to complicate it more by worrying about minor effects. But in fact it did turn out to be important because of this rather curious type of reaction, and the presence of the polar stratospheric clouds, which are needed to produce this thing.
You’ve been involved in a few assessments. You said you wrote the chemistry chapter.
In 1985 I did the chapter on that. I’ve been involved in every one, but the last one I wasn’t involved very heavily, the final, 2006 was it?
Every one of the WMO/NASA.
Yes, that’s right.
Can you talk a little bit about what it’s like to work on these assessments? How is it different than co-authoring a scientific paper with two or three other people? Is it just a question of scale or is it really a different process?
It is a different process than meetings, but it’s stimulating. You basically have some knowledge, and you set the general terms of reference of the particular assessment presented to you. They evolve after the early meetings on the assessment. I’ve been involved with the discussion of the content. It’s a fairly intensive period of traveling and meeting with people, and then going away and collecting information and then starting to organize its assembly. I think the discussion meetings we’ve had on the chapter meetings are generally pretty hard for stimulating science. Then you try and put together something that you think is going to stand the test of the review. I learned a lot actually in science from participating in it.
Learned a lot about ozone science? Or learned a lot about how to write?
You learn about how to collect information together and present it succinctly. You learn to compromise. To get what you think is the right answer is not always straightforward. You’ve got to persuade others and others might come up with ideas you hadn’t thought of, and you have to incorporate those. So it’s a fairly rigorous process, I would say. But you also learn about other people’s science, broader than you would normally know, because the assessments, although they are a collection of chapters, by going through the meetings you are aware of what the other chapters are doing, so you see your work, or your specialty, in the context of the overall thing. This is a rather unusual thing, really, in science. You usually these days have to beaver away in your little specialty area. This is another way of getting stimulus by listening to other scientists doing different things, which I think is quite a useful thing.
Was there a lot of negotiation at these meetings about particular terms used, ways to express things, or how do we handle uncertainty if this scientist came up with this estimate and someone else came up with another one, how do you put them both in the same assessment? Was there a lot of that?
We usually try to resolve conflict of that kind and come up with the best answer and get everybody to agree with it. It does occur. I would say that in my own work we usually would come up with something that stands the test of time. I would say that it does ultimately get the best possible answer at the time, and then other research may prove you haven’t got the full story.
Most of the time you would try to put a consensus view in the chapter as opposed to presenting the uncertainty.
Yes. Basically in a chapter you are the experts — you’ve just got to try and just do it. You’ve got to highlight the uncertainties of things you don’t know, and you’ve got to highlight the things you do know that you think are robust, put them forward and make the statement to support it. The main thing about this sort of writing is not to leave it “on one hand and on the other hand” and try leaving it to some non-expert to try to reach a conclusion, because they are more likely to get it wrong than you are.
Bob Watson said one strategy was to use a lot of “if-then” statements, which don’t tell you what policy to choose, but they tell you, “If you do this, this is what will happen.”
That’s certainly true. That’s a good point, which came out from the very early stuff from CCOL. You don’t tell the politicians what to do. You tell them what the consequences of certain actions are, and then you hand it to them to make the decision about what actions to take.
Yes, very different things. Did you notice an evolution in the format of the assessments in the whole time you were involved with them? For example, Bob Watson said his big regret about the 1985 Blue Books was that they didn’t contain an executive summary and then later assessments did. Were there other things that changed over time in the way things represented or in the formatting?
It did change because the emphasis of what it was trying to do changed. In the early days there were a lot about substitutes. Or at least in the 1985 one, there was a lot of debate about substitutes in the assessments in the ’90s, for example, what to do about the HCFCs and all these sorts of things. That changed the pattern a little bit from the basic atmospheric physics and meteorology to the lifetimes of all the different molecules that were either proposed and the degradation products from any new molecules. You didn’t want to put something in that was going to affect the atmosphere in a deleterious way that you hadn’t thought about by degrading some other thing. The assessment went strongly into that area, and I think really that was partly a way of persuading the industry to help them get over the impact of the regulation of the CFCs. Then in more recent times, the climate and the meteorology became a much more important part of it, the climate impact on the ozone layer. Of course the other thing about it was as the measurements and observations became more sophisticated with the balloons and satellites and polar campaigns, all sort of real dense information of atmospheric observation and their interpretation came in. So it did change the character, and it became a much less cozy club, really I suppose, because much more expertise in other areas was needed, and consequently much more debate about what was good and so on.
There was a point I think right after the ozone hole was discovered. Prior to that most people had been talking in the assessments and in the papers about things in terms of the ozone depletion potential of a given substance. After this moment, whenever it was, people were talking about chlorine loading potentials. My understanding of that shift is that it happened because the chemistry with the Antarctic ozone hole and the heterogeneous reactions suddenly got so complicated that you couldn’t really calculate the ozone depletion potential of everything very easily and with great accuracy. But people had accepted that CFCs and other substances are causing ozone depletion; that wasn’t contested anymore. So you can simply talk about the chlorine loading potential of something with the understanding that putting chlorine in the stratosphere is bad. Have I got this right? Did that happen?
This was part of the evolution that I was trying to portray when I said that we got in the early ’90s or late ’80s about the substitutes, and this concept grew and evolved during that discussion. Because the most important thing and the bottom line of it was the amount of inorganic chlorine present in the stratosphere, which was going to be a contribution from a number of different substances. In the simple idea of CFCs, they were all destroyed in the stratosphere. The troposphere wasn’t really a consequence to the CFCs; they just mixed around and went up and then they would degrade in the stratosphere. As soon as you had things degrading in the troposphere, then the global circulation of the troposphere became an issue. It was much more difficult to relate an emission at the surface to an ozone depletion in the middle or upper stratosphere. Then it starts becoming important what part of the stratosphere the molecules are actually getting to. The whole business of the atmospheric circulation became much more important.
Do you know who it was that came up with the chlorine loading potential and pushed for using it instead?
I think it was probably Don Wuebbles, actually. Neal would probably know. I think Don Wuebbles.
To me the fact that you can talk about chlorine loading potential instead of having to talk about ozone depletion potential tells me that in general the community has accepted that ozone depletion is real, that it is caused by anthropogenic chlorine
By that time it was accepted that there was a problem, and it was really about how to manage the global emissions so that the overall impact on the ozone layer was essentially optimized or reduced. It had been accepted, and then how do you manage it? That was really all the discussions in the later protocols were based on this essentially chlorine loading potential. How much chlorine would be in the stratosphere as a function of time in the 21st century? Then an algorithm was brought in to include the bromine so that all the ozone depletion could be lumped under this chlorine loading even if it was in the form of bromine.
Bob Watson made this analogy. He said it’s really the CO2E for ozone. That was really interesting.
Yes. Well in fact, of course, the ideas of CO2 were modeled on that.
I should look at this myself, obviously, in the different assessment reports to see when you started talking about chlorine loading potential. But do you remember when that happened? You said early 1990s?
Well were certainly were talking about it in the mid-1990s in our assessments here, and I think they more or less followed — We continued in the UK to have these so-called SORG [?] reports. [Looks through reports in his files] We have 1993, ’96, ’99, and ’88. These are the reports we put together here. Let’s look at ’93, whether we looked at chlorine loading here. Hmm, yes, certainly by ’93 we were talking about projections of chlorine loading from CFCs, carbon, blah, blah, blah, “as shown in our report in ’91.” These were the kinds of things that the scientific community was offering to aid in the regulation. This was in ’93, so these reports are actually what we produced for Department of the Environment in the UK as a kind of local advice for them to take with them to the Montreal Protocol meetings, so they didn’t only rely on the WMO thing.
Speaking of the Montreal Protocol meetings.
You should mention the SORG reports.
Yes. I’ll have to look at them myself too. Some authors that I’ve read, for example, Richard Benedick, in his book, Ozone Diplomacy, he says, “The discovery of the Antarctic ozone hole had no affect on the Montreal Protocol negotiations.” Other people have said it had a huge affect on the Montreal Protocol negotiations. What would you say?
The point is that Montreal Protocol was signed in 1987.
I think about three weeks before the first Antarctic expedition results for the AAOE were…
Before the really convincing cause-and-effect relationship, the explanation of the massive depletions in Antarctica. I think that the Blue Book did consolidate all the science up to 1985, which did indicate that there was a potential problem. I think people felt you just couldn’t keep putting chlorine into the atmosphere because there were various scenarios, even without heterogeneous chemistry, where you would start perturbing the parts of the atmosphere where the ozone resides, and the impact of that was all pretty uncertain. People realized that it was a potential problem, which warranted some sort of restriction. I forgot what the Montreal Protocol actually said, the first one. Was it complete cessation?
No, I don’t think it was.
When you look at the original Montreal Protocol, it wouldn’t eventually have helped anyone really. I think the situation is that there was basically a consolidation of the science, with the knowledge of this unexplained problem in Antarctica that certainly from the scientific point of view, you were getting more and more convinced that there was a problem.
That’s sort of how I feel.
So I don’t know about Richard Benedick’s statement. He was a fairly kind of skeptical person — think he would be skeptical about anything.
He says, “Because we didn’t yet know for sure the cause of the Antarctic ozone hole, we negotiators agreed not to discuss it during the negotiations.” But that is not the same thing as each individual negotiator possibly being concerned.
Having the knowledge. He may not have been formally, but people did have the knowledge that there was a perturbation which had been unexplained.
Exactly, a very large perturbation.
After that the acceleration of the protocol process was really driven by the knowledge that if something wasn’t done…
Yes. So it certainly had an affect on later stuff. I could ask you many more questions, but I think it’s almost 1:00 o’clock. I should probably have lunch.
I hope I’ve been some help.
Oh, definitely. Thank you very much. [Break]
This is the first one of the data. The data evaluation still goes on. It’s expanded now really to provide information on tropospheric chemistry.
I think that was the question Bob Watson said I should ask you: Do you think they are going to stop doing ozone assessments or should they considering you sort of have the issue nailed down?
I think now that it could be folded into an overall health of the atmosphere theme. I wouldn’t have thought that it needed to be at the intensity that we’ve done it, for two reasons. First, the changes in the understanding of the science is really much more constant now. There are no big changes. Second is that the issue is tied in also with the climate change. So what happens to the ozone layer now depends on what the temperatures are going to do.
That makes sense. We need to keep looking at that.
You need to be looking at that. It could be done together, probably.