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Oral History Transcript — Dr. Mack McFarland

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Interview with Dr. Mack McFarland
By Keynyn Brysse
July 31, 2009

 
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Mack McFarland; July 31, 2009

ABSTRACT: In this interview, Mack McFarland discusses topics such as: his work with ozone depletion; his time at York University with Harold Schiff and Brian Ridley; working at the Aeronomy Laboratory at the National Oceanic and Atmospheric Association (NOAA); joining the DuPont Corporation; helping to limit chlorofluorocarbon (CFC) production; the Intergovernmental Panel on Climate Change (IPCC); the Antarctic ozone hole; Bob Watson; Dan Albritton; Ozone Trends Panel; and the Montreal Protocol (Vienna Convention for the Protection of the Ozone Layer).

Transcript

Brysse:

I have heard a little bit and read a little bit about what youíve done. I know youíve been involved with some ozone assessments, and I know youíve worked with DuPont for a long time. But Iíd like to start by generally hearing what your work to do with ozone depletion has been.

McFarland:

Well it started in 1974, when I did a post-doc at York University with Harold Schiff and Brian Ridley measuring nitrous oxide (NO) in the stratosphere. I started just after July 4. I donít remember the exact date, but it was within a month of the Molina and Rowland paper being published. Then after a year there I went back to the NOAA Aeronomy Laboratory where Iíd been working and continued to work measuring NO and then later NO2 in the troposphere and the stratosphere from balloons, ships, airplanes. I also did some work in that group measuring CFCs in the stratosphere. Then in December í83 I joined DuPont, where Iíve been ever since. I was put on loan for two years to the United Nations Environment Programme in Nairobi — the atmosphere unit. Let me see if I can get the dates right. That was most of í95, all of í96 and a little bit into í97. Then when I came back from there I went to the IPCC Working Group II Technical Support Unit in Washington. Thatís when Bob Watson was co-chair, Working Group Two. Richard Moss was the head of the Technical Support Unit in Washington. During that time DuPont paid all my salary, all my travel, and I had no reporting responsibilities within DuPont. It was just like I was with UNEP or IPPC employee.

Brysse:

You are the first person Iíve talked to whoís been involved with industry and with the ozone depletion stuff. Has that caused a tension?

McFarland:

No.

Brysse:

Good. [Laughter]

McFarland:

Itís been an exciting time. Itís a matter of being, I guess, at the right place at the right time or lucky with my career. You said any tension. The absence of tension is because of alignment of values. DuPont had based its decisions on sound science. In í86 with the í85 ozone assessment, and based on that and the growth of CFCs DuPont came out in support in September í86 of an international agreement to limit CFC production and consumption. In 1988, with the summary report of the Ozone Trends Panel that I was a member of, was issued on a Tuesday; on Friday the DuPont Executive Committee made the decision to phase out CFCs through an orderly phase out. And then later put dates on that, what that meant, how soon we would phase out. Subsequently we made statements about HCFCs, and supported time certain phase-outs for those. Right now we are out there actively working on a global agreement on HFCs, perhaps through an amendment to the Montreal protocol since itís been so successful.

Brysse:

So both of those that the í86 and the í88 decisions by DuPont were directly in response to the scientific assessments?

McFarland:

Science.

Brysse:

Was that mediated by you? Youíre the one that read them and reported back to DuPont or other people in the company?

McFarland:

Read them or participated in the assessments in both cases.

Brysse:

What exactly was your role in those assessments?

McFarland:

In í85 the í85 assessment had already been under way. It was a man from DuPont that was at that time running the modeling group, Aaron Owens, who was on the NOX chapter at the time. Since my background was NOX, he suggested that I take his place. So I was involved in that chapter of the í85 ozone assessment. By the way, as far as Iím concerned, that was the start of international scientific assessments on environmental issues. As far as Iím concerned, Bob Watson invented the international assessments with that. I was a member of the Ozone Trends Panel. Iíve been either a reviewer or an author of every one since.

Brysse:

What about the 1981 assessment? That was at least partially international, wasnít it?

McFarland:

Not to the extent that í85 was involving all of the agencies. I just didnít view that as of the same character. When youíve got so many sponsors and truly an international assessment with all of them involved. You should find an interview with Bob Watson asking him why he did it. You should find that. I canít remember where it was. As I remember that now (my memory isÖthat was a long time ago), they asked him why he organized that assessment. He talked about the different assessments that were coming out from the various governments or agencies, like the NAS and the French and the UK assessments all had their own assessments coming to somewhat different conclusions on the same science. Maybe not even different conclusions, but just highlighting different points, which are not the way to do things internationally when youíve got to have a basis for moving forward.

Brysse:

I heard that, I canít remember if it was Ted Parsonís book or somewhere else, but I know that there were something like seven different national assessments in 1979 that, as you say, highlighted different things so people that didnít really want to regulate could say, ďWell this assessment says this and that assessment says that. They donít agree so clearly more work needs to be done before I need to do anything.Ē I see a real need for an international assessment.

McFarland:

The other thing is you know when youíre looking at these, I think itís very often on all of these issues; the value judgments and the science get blurred. I strongly object when people say, ďThe IPCC assessment says we need to do this.Ē The IPCC assessment doesnít — itís supposed to be policy relevant, not policy prescriptive. Itís the same with the ozone assessments. There are value judgments that the regulators, the politicians, are paid to make, elected to make in the case of politicians. The science is one piece of information that they should use on that.

Brysse:

Have the international assessments, do you think, been like that right from the start? Policy relevant, but not policy prescriptive?

McFarland:

I think so, and theyíve improved over the years. I had discussions with Bob about this. You look at the executive summaries of those documents, and they improved drastically over the years in terms of getting more and more to the point. In some cases I still think they are too long, because I remember back in Ď80s when a report would come out I was asked to summarize it in one page.

Brysse:

It sounds hard especially without an executive summary already there.

McFarland:

Well, you know there were some, but not much. Iím sure youíve looked at those early assessments.

Brysse:

Iíve been wondering, and Iím asking everybody this question to hear what everybody says. Given that the 1985 blue books didnít have an executive summary (it had an introduction, but thatís not the same thing, and it didnít really summarize all of the conclusions), how did it get so influential? Surely the policy-makers didnít read the whole thing, so how did they find out what was in it and believe it?

McFarland:

I canít judge externally. I just know based on that I remember an internal DuPont review in the summer of í86, and going over it and looking at the prospects. If you look at the global consumption of CFCs at that time, and it was during that period that it just started to turn up — it had been flat for some time. It was that global increase in CFC consumption and the science in the Ď85 assessment that was the basis for our support. Some people have asked, and I remember all the interviews there, ďWell, isnít it based on the finding of the Antarctic ozone hole?Ē I was actually concerned at that time that the perception would be that, and if it turned out that the ďozone holeĒ wasnít due to CFCs, it would reverse something. You know, the science, regardless of what was causing the Antarctic ozone hole, had firmed up enough to have a global agreement. If the science had turned out differently for the ozone hole, then I think it would have undermined all progress toward an international agreement.

Brysse:

Right, because people would have been distracted by what was or wasnít going on with the Antarctic ozone hole. Maybe you can speak to this as one of the participants in the í85 assessment. I was surprised when I read it. I know that the final versions of the chapter werenít due until November, and that was about six months after the Farman paper came out about the ozone hole. Yet there really isnít anything in the assessment about the ozone hole. There are a couple of sentences, maybe. I was surprised about that in general. I was also surprised specifically by a contrast I noted between chapter two and chapter 13. I donít remember what the subjects were. Thirteen was model predictions. Two was I donít remember, something about chemistry? Chapter 13 sounded very cautious. There may be chemical reactions that weíre not aware of yet. There may be something going on that we donít fully understand like with the Antarctic ozone hole. Chapter two was very confident. There are no catalytic cycles we havenít uncovered yet. Weíre pretty confident about the chemistry. And I was surprised to see that seeming contradiction between two chapters of the same report. I know theyíre written by different people, but.

McFarland:

I donít remember. Thereís been a lot of water under the bridge since then. I just remember what the decision was based on. The underlying science to the point that it was reasonably certain that if you continue to increase the global consumption of CFCs, you would ultimately see appreciable ozone depletion. That was the basis for DuPontís support for an international agreement. Now the details on what youíre asking, thatís too long ago.

Brysse:

It is a while ago. So basically there —

McFarland:

I havenít — a copy of the í85 assessment is on my desk. In fact I wore out one copy back in those days. All the pages were falling out and I had to get another copy. [Chuckles] But thatís too long ago.

Brysse:

Okay. Basically, overall what you are saying is the threat of global ozone depletion was enough. Even the knowledge that thereís an Antarctic ozone hole, you didnít know enough about it yet. You donít know if itís caused by anthropogenic chemicals or not. But there is enough without it, so leave it for now. We need to learn more about it before we really talk about it.

McFarland:

Yes. And in fact again, I want to emphasize there were competing theories, and if it had turned out not to be related to CFCs and other ozone depleting substances, then it could have undermined the progress toward an international agreement and distract people from the underlying science that was firming up.

Brysse:

Great. That brings me to something that my colleagues and I are deliberating and trying to figure out. That is if there is a general hypothesis that we can come up with here. There seems to be something going in environmental assessments and environmental science to do with conservatism.

McFarland:

Well, itís just that scientists by nature are trained to be conservative. They like 95% confidence levels when youíre looking at data. Thatís just the entire training of scientists.

Brysse:

Right, but it goes beyond that. Letís say weíre talking about projected future sea level rise, and you think maybe itís going to be three meters plus or minus a meter. That means that four meters is just as likely as two meters. But most scientists, you really wouldnít hear them talking about four. Youíd hear them talking about the three for sure and maybe the two. So, itís not just conservatism in terms of the amount of certainty. Itís also conservatism in terms of making the least astonishing claims or something.

McFarland:

You know, I donít know. Youíd have to talk to people who you think are specifically doing that. I think there is a concern among some that if youíre wrong on some of this, if you overplay it, then it reflects on the scientific community and it could lead to distrust of scientists. The Ozone Trends PanelÖ I guess the findings were so significant in terms of the Antarctic ozone hole and the trends in the northern hemisphere that nobody ever pointed out that a primary reason that the Ozone Trends Panel was formed was to look at the satellite data. Don Heath had testified that we were losing a percent a year. That turned out to be a problem with the satellite data. That wasnít an assessment; it was one person. I was surprised that nobody picked up on that. If you come out and something turns out to be significantly overplayed there could be concern that it could undermine progress.

Brysse:

Another person I talked to described it as, ďYouíll get accused of crying wolf.Ē Then your credibility suffers. People wonít listen to you again.

McFarland:

Scientists donít like to be wrong. [Laughter]

Brysse:

But itís more okay to be wrong by underestimating the danger? Because in a sense thatís wrong, too.

McFarland:

You know, youíre right. It should be put out exactly as the science states it. I try to do that. Iím just telling you that thereís this concern about being wrong. On these issues that have long time consequences especially, you need the best information.

Brysse:

Yes. Something like that happened with Arctic ozone estimates, didnít it? I forget when, but there was one year that folks thought it was going to be particularly bad. Then it turned out to not be so bad, not because any of the science was wrong but because it didnít get as cold as they thought it was going to. Did those scientists suffer for that over-prediction?

McFarland:

Again, itís the difference between a scientist or a paper and an assessment. Thatís why I like to pay attention to assessments, because it is the voice of the scientific community.

Brysse:

As opposed to one scientist who —

McFarland:

Well, you know it doesnít happen much anymore but two decades ago, when a finding came out and it was published in the paper or in the news, I used to get calls, ďWhat does this mean?Ē Youíve got to look at all the information and put it together to have a firm basis for a policy decision of the magnitude you are looking at on these global environmental issues. So there are a number of things that I think are the advantages of the assessment. One of them we talked about earlier. That is because people, scientists focus on an area or on a specific field within the field, in trying to talk about the science they would tend to emphasize that area. That may have been part of these national assessments: whoís sitting down to write it, whereas you put these international assessments together. On ozone you had people from, if not every laboratory actively engaged, virtually every laboratory actively engaged on the assessment. So you get the different perspectives from the different fields, the different backgrounds. And I think thatís necessary. Scientists are just human. Thereís a quote from E. B. Wilsonís book on scientific experimentation. When was it written? Maybe 50 years ago. It goes something like, ďItís in a section on bias in the experimenter. No human being is even approximately free from subjective influence. The honest and enlightened investigator devises the experiment to avoid his biases,Ē or something like that. ďOnly the naÔve or dishonest believe his own objectivity is sufficient safeguard.Ē I used to use that quote in giving talks about why you have these assessments and you get a variety of perspectives to filter out the biases. You know, essentially when you are putting an assessment together itís a social experiment, and it is the variety of scientists with the variety of backgrounds that help filter out that bias and maintain the objectivity. That is the value of that. The other value is, and it relates back to the first point, is the different organizations, governments, and decision-makers in the private sector, NGO sector, get their information from different sources. With assessments you bring together the scientists to discuss these issues, and they agree on what are the important policy relevant facts, and they go back and they have a single voice, as it were, about what is the important information. Thatís why the executive summaries are so important. What is really important? I think it should be in those cases filtered a little more because I think there are things that may be important that should be in the technical summary, not in the executive summary. Information important to scientists, but maybe not to the policy community or the decision-makers.

Brysse:

Thatís something else Iíve been wondering. You might be able to help me with this and you might not. The assessment obviously has to be scientifically accurate, but the other important way to judge how useful it is, is if it is answering the questions that the policy-makers need answered. How do the people making the assessments find out what those questions are? Is it the scientistís best guess, or do people in the policy community actually tell them what they need to know?

McFarland:

I think it comes down to individuals. Some people have told me thatís one reason why Iím somewhat valuable on these things because I talk to the decision-makers in industry. Not only in DuPont, but our customers and sometimes competitors. What are the important things there? I attend some of the political meetings and talk to others. Itís that understanding. On the ozone assessments, I believe it came down to two people. Now there are others clearly involved, but it was Bob Watson and Dan Albritton who were so good at bridging that gap between the policy community and the scientists. They led that for years. Now youíve got a new group, the current group, that are attending these meetings and they will catch up fast. There was a gap when Bob and Dan left. I think the same thing is true on the climate. Itís just that it is so much broader. It comes down to that fact that somebody has to take the time to really understand what those issues are because youíve got to interpret what the policy community is asking, and policy makers and scientists speak different languages.

Brysse:

Another question Iím struggling with that sounds like it should have a really simple answer (and I donít know if it does), is exactly what do scientific assessments do that scientific papers donít? I think youíve helped me answer that partially by talking about getting people together and bypassing and removing biases. But in a sense with most of the assessments, if the purpose is to collate the scientific knowledge thatís current, in a sense there is nothing in the assessment that isnít already out there in scientific papers.

McFarland:

But how many papers? And what are the key points? How do you interpret those papers and the policy relevance? Itís not one paper, itís hundreds of papers. Andy Revkin told me that he had talked to someone that was in Venice two or three weeks ago at the scoping meeting for AR5. That he told him that a plot was put up about the number of papers on climate, and it was just increasing exponentially, the way he described it. Now, how do you filter out all of this information and synthesize it and take out, ďWhat do we really understand?Ē A lot of the papers are data, and it has to be interpreted in terms of information thatís relevant to the policy community. Thatís not just one paper; itís not just one review article.

Brysse:

This is helping me out a lot.

McFarland:

This is just one personís opinion.

Brysse:

Yes, but Iím collecting several of them. So I talked to Ted Parson on Monday, and he said to say hi. He also said something that I should ask you about because he said the two of you disagree on this. You mentioned it already. It was in 1988 when the Ozone Trends Panel executive summary came out and then DuPont made the decision to start phasing CFCs out. Parsonís argument is that, what I just said, there isnít new science in the assessment. Now there was a bit in terms of the new analysis of the satellite data, but he says the stuff about the Antarctic ozone hole wasnít new. That in fact it was more or less identical to some stuff that came out in NASA reports that came out in December. So his question is, why didnít DuPont change its position based on the NASA report that came out four months earlier? He said you wouldnít agree with him.

McFarland:

I didnít know — Iíll have to talk to him about it. I didnít know it was a disagreement.

Brysse:

Well, this wasnít malicious.

McFarland:

One reason for the Ozone Trends Panel report being so important is that it represents the authoritative voice of the community. Two is, I believe that re-analysis of ozone and for the first time finding ozone losses over mid-latitude is incredibly important. I heard people say, ďWell, itís over the Antarctic. Nobody lives there. Itís a frozen continent. What difference does it make? Itís in the time of the year when there is very little sunlight anyway.Ē Iím not saying that I said that; Iím saying I heard people ask that. But now when it gets down to over mid-latitude, that is very different. That wasnít out there. The international Ozone Trends Panel report was not an assessment. It analyzed data. I remember hours and hours of going over that information. Itís very different, and it was the combination of the two. There was something new in it.

Brysse:

I agree with that. I think if you call it an assessment, it is not an assessment like other assessments.

McFarland:

It is not. It is not an assessment, and it should not be called an assessment. Itís an Ozone Trends Panel Report.

Brysse:

I donít know if you can answer this. This is also from Parsonís book. He said that years ago when DuPont first started using CFCs, they obviously investigated them to see if they were harmful, but they only tested their potential effects in the troposphere, not in the stratosphere. Is that right? They didnít realize that they would be transported into the stratosphere?

McFarland:

I wasnít here then, but I can tell you what I understand about all this. People look at the toxicity and effects on humans, and they were known to be very stable. You know nobody had really asked the question. Is it covered in there? In 1972, Ray McCarthy, head of Freon Products Laboratory, invited people to a symposium on the ecology of fluorochemicals, fluorocarbons. It was based on Lovelockís measurements of CFCs in the atmosphere. As I heard the story and understood it, Ray McCarthy did a back-of-the-envelope calculation that suggested that what had been released into the atmosphere was still in the atmosphere. I donít know whether youíve seen that letter or a quote, but I could get you a copy of it. That started the fluorocarbon program panel, which I think, given the work being done, would have ultimately uncovered what Molina and Rowland did.

Brysse:

I donít think I have this quotation. That would be good.

McFarland:

Well, itís the letter that he sent out. Then there was a symposium, and then people started studying them. This fluorocarbon program panel started funding studies about what happens to them in the atmosphere. That was two years before Molina and Rowland. You hadnít come across that?

Brysse:

I think I did read in general some general information about that. I knew that DuPont was investigating it as well.

McFarland:

Well, it was all of the producers from North America, Europe and Japan. DuPont initiated the whole program. I know it became known as the Fluorocarbon Program Panel. It may have had a different name in the first year. Of course, in 1974 that program focused on stratospheric ozone. Of course when I came in í83, thatís what I did. I was the liaison to that and the DuPont modeling group. Iím not a modeler but was a liaison to the scientists that were working on that, the scientific community, and was involved in the assessments.

Brysse:

You mentioned liaising with the modelers, but youíre not a modeler yourself? That makes me feel immediately sympathetic, because I find reading about the models sometimes technically dense. [Chuckles] Hard to follow.

McFarland:

A model is just a synthesis of our knowledge, and trying to use it to project effects based on what we really know. Youíve got to have a model to synthesize that much complicated information.

Brysse:

Yes, thatís very true. Were you one of the authors for the Ozone Trends Panel report?

McFarland:

Well, there was an Ozone Trends Panel. I was a member of the panel. Then there were others that contributed beyond the panel members. You could look at the report and see the panel members.

Brysse:

Yes, I saw that you were on there. Overall, what do you think the role has been of scientific assessments and the Ozone Trends Panel report (if weíre not calling that an assessment) in leading to the Montreal Protocol and the amendments to the Protocol?

McFarland:

Well, it was the í85 report that provided the basis for the reports and assessments that followed. Whether it would have happened without that, I donít know. I questioned whether it would have, but how do you run the experiment? Thereís no doubt in my mind that it was the Ozone Trends Panel report that had a very significant impact, although the Parties wanted an assessment under the Protocol. The assessment process that was set up under the Montreal Protocol required an assessment every four years or more often if requested by Parties. After release of the Ozone Trends Panel report they immediately asked for an assessment under that provision after the ozone trends report. That was the first assessment under the Montreal Protocol in 1989.

Brysse:

I thought the 1994 was the first official one. So the í89 one is, okay. Thatís good to know.

McFarland:

The Protocol took effect in mid-í89. I donít know when it was ratified, but that 1989 assessment was issued under the Protocol. Thatís my understanding. I participated in it.

Brysse:

Iíll go back and look at the fine print.

McFarland:

Iím sure that í89 and í91. There were two before í94: í89, í91, and then it took on the four year.

Brysse:

So they didnít decide to only do them every four years until í94?

McFarland:

No. The language says, ďEvery four years or more often as requested by the Parties.Ē So they requested those reports, and then theyíve requested other special reports. The one on methyl bromide, for example, is one that the parties asked for a rapid assessment. Iíve no idea when that was.

Brysse:

Itís í92, isnít it?

McFarland:

That sounds right.

Brysse:

Yes, I have that little methyl bromide report. I have gotten the impression that one thing — Let me rephrase this. Some people, who have written books about the ozone regime, as they call it, say that one of the biggest reasons for the success of the Montreal Protocol and its amendments has been that there were alternatives to CFCs that were reasonably cheap and reasonably readily available. They contrast that with the climate change issue where they say itís a little harder to find replacements for things like gas and oil, for example.

McFarland:

If you look at most of the compounds that were used as substitutes for CFCs, the HCFCs and the HFCs, most of them (not all of them) that have been used to substitute were identified to a large extent in the Ď70s. Now the toxicity wasnít complete — the toxicology. The production processes are more expensive. Itís more expensive to make. They are multi-step processes, whereas CFCs and HFC-22 that has always been around are one-step processes from the chlorocarbons. These are multi-step processes. That just means more money to make them. In some cases, if you look at the improvements that have been made with the other gases, if you made the same improvements, CFCs would have done a better job because the physical characteristics of the CFCs made them very good refrigerants, very good foam insulating expansion agents. What the compounds were that would be used to replace CFCs we didnít know at that time of Montreal. In fact, Iíve been told by some that it was the support from DuPont and the United States industry in í86 that helped convince policy makers to agree to the Montreal Protocol. You know, the Alliance came out in support in 1986. If you want to talk with somebody else that was involved in that you might talk to Kevin Fay of the Alliance. He was the executive director at the time. That provided optimism that alternatives could be perfected, all the studies made and deployed. I was also told that DuPontís announcement for the phase out provided optimism that the phase out could happen.

Brysse:

DuPont made that announcement before knowing for sure?

McFarland:

Oh yes. DuPont had discontinued in 1980 the work on alternatives. I think thatís covered in Parsonís book, isnít it? I remember the work was reinstituted in í86 when we came out in favor of an international agreement to limit consumption of CFCs, and then it was accelerated in í88 with the phase-out announcement.

Brysse:

Do you think people are right in saying that itís even harder in the climate change instance to find substitutes, or at least substitutes that allow us to preserve our accustomed way of life?

McFarland:

Yes. [Laughs] I mean you are dealing with the very fabric of society: energy. What do we do that doesnít involve energy? Although I donít think it was as cheap as people say it was, the transition out of the ozone depleting substances was not noticeable to most people. They just see their refrigerator running, their car air conditioner running. The climate issue is not going to be the same. Even, I talked about the HFCs and developing a separate international agreement to cap and reduce their consumption. They are included in a separate title in Waxman-Markey. That separation goes all the way back to Lieberman-Warner. We donít know what the alternatives are going to be in most applications. With all the substitutes that are going to be needed there and the technologies, you are drawing the box tighter and tighter. You are looking for properties that meet all the requirements of multiple systems. Itís a very restrictive set of criteria to meetÖ Youíve got to maintain safety for the consumer. Thatís an absolute must. Then you are not only requiring that you not impact ozone, you want them to be low global warmers, and in general that means short atmospheric. You get short atmospheric lifetimes, and that means decrease in stability. Then you get to the safety issues of flammability and toxicity, so it is getting tougher and tougher to find those compounds. Thatís just in this issue. Then you look across at our energy supplies. Thereís going to be no silver bullet there.

Brysse:

Somebody else that I interviewed said something really interesting to me. I donít know that I agree with him, but I thought it was interesting what he said. I was asking him about the differences between ozone assessments and climate assessments and whatís going on. He said, well, with the ozone assessments, almost from the beginning, almost from the blue books, you could show that ozone depletion was happening, and that we sort of knew what to do about it, whereas with the climate change assessments theyíre not at that stage yet. They are not at the stage of saying, ďLook, see, this stuff is happening. Now we need to fix it.Ē I donít know if I agree.

McFarland:

I wouldnít put it as clear-cut as that, but establishing the cause and effect relationship is for climate change is not as easy as it was for ozone. For the Antarctic ozone hole especially, it was like going into a laboratory and measuring what was going on because it was so dramatic, and it was easy. It was like a laboratory experiment up there, just a little harder to get to.

Brysse:

Right. Once they detected the chlorine monoxide, that totally sealed the deal: itís CFCs for sure.

McFarland:

Itís not as clear because of the global climate system, the variability and separating that out. What is natural variability compared to anything that might be caused by the increases in greenhouse gases? It gets much more difficult.

Brysse:

Another thing that Iím interested in, I donít know if youíve been involved in these at all, is the different metrics for ozone depletion that have appeared over the years. First thereís the ODP, then thereís the CLP, and then more recently thereís been the effective equivalent stratospheric chlorine. The purpose of all of them is to tell you how dangerous the chemicals are, how much ozone depletion is happening. But they all measure slightly different things.

McFarland:

You said you talked to Ted Parson. I think he describes it very well; about the value of chlorine loading potential or EESC. Thereís a difference clearly between CLP and EESC; EESC as an improvement, but itís not a huge difference in terms of policy. Youíve got to bring the bromine in, of course. When you are looking at these ozone depleting substances itís not just how big the ODP is but how much a substance can contribute to ozone depletion. And thatís the same problem with a GWP. You know, a big ODP or GWP number is not important if the emissions are de minimis; the big number doesnít necessarily mean a lot. ODP doesnít necessarily mean a lot. If youíve got very, very low emissions of a substance it canít contribute to these global issues. Itís the product of emissions and ODP or GWP. Chlorine loading potential and the EESC just attempt to quantify the actual potential impact using scenarios of emissions to help policy makers set priorities for what they might do. As far as chlorine loading potential, I remember on the night of March 15, 1988 calculating the equivalent of chlorine loading potential for various CFC consumption scenarios and in some waves that was used as a basis for DuPontís decision to commit to a CFC phase-out. I did those calculations on a hand Casio calculator. Youíre just saying, ďOkay, this has an ODP of X but what does that mean?Ē ODP was ratioed to CFC-11, so CFC ODPs were all around one except the halons that were higher. And then the HCFCs, of course, much lower. But CFCs were all around one. Well, what does it mean? Itís got to be how much is the world using? So you have to quantify it in terms of emissions and potential impact using CLP or EESC. The other thing that I think has been valuable is, I believe in the policy area, the scenarios are not used the way they were meant to be used. ďRealisticĒ scenarios are controversial because who decides what is ďrealisticĒ and that was the controversy around the IPCC special report on emission scenarios. In ozone I think scientists got away from controversy by running extreme unrealistic scenarios to allow priorities to be set. A ďbusiness as usualĒ scenario was just one of many. Then extreme scenarios were to answer questions like: ďOkay, what if you eliminate all production? What if you eliminate all emissions? What if you do this?Ē They werenít realistic, so it gets away from controversy. It gets away from questions like is that really a realistic scenario or not? It just says that you look at the extremes and it allows you to set priorities among policy choices. For example, if you look at what happened in 2007, the HCFC phase out was accelerated. You look at the table in the last assessment report and (thatís 2006, right), it shows of all the things you could do, accelerating HCFC phase out has the most effect in terms of protecting ozone. Not to say that you could eliminate production or eliminate emissions of them immediately, but it was an extreme scenario that said, ďOf all the actions that could be taken, that would be the highest priority if you wanted to do more to protect ozone.Ē If you havenít talked to Ted, get his description of the use of CLP and EESC, because I think he does a good job of covering that issue. Well, get his description.

Brysse:

So what about this special report? Do you remember what you —

McFarland:

Thatís IPCCs special report on emission scenarios that I was talking about. I think if I remember correctly, it was — Iíll remember the terms in a minute. The economists got into it, I think, and weighed in on whether things were reasonable scenarios and argued about them.

Brysse:

And thatís not necessarily the point. The point is, as you sayÖ

McFarland:

If you look back at the history of scenarios and how they were developed and how they are used in an analytical framework, they can be very useful. Shell developed them. I donít know if they developed them, but thatís where they became very popular as an analysis tool. You should look back at the Shell scenarios and how they were used.

Brysse:

I noticed with the last two assessment reports, all of a sudden thereís this huge emphasis on 1980. Thereís the EESC, and then every graph that shows the EESC has a big gray bar that shows you when it gets back to 1980 levels. Has that been a really useful tool?

McFarland:

I think so. That table I talked about is based on that. You can ask was there any really appreciable ozone depletion before 1980? Statistically could you have really seen it before that point? So itís become the metric of choice. Is it the best metric? You could argue about it forever, but itís not very useful in the policy context, but I do think if you went back and did a careful look at the data of prior to 1980 youíd be hard pressed to say weíd seen anything.

Brysse:

Does it seem like the policy-makers find that really useful to be able to say, ďLooking at this graph, if we do this weíll be back to reasonable levels by 2015Ē?

McFarland:

I donít know. All I can say is that they appear to react to it. Youíd have to ask them.

Brysse:

I liked seeing it when I saw it there. It seemed immediately understandable in a way that a lot of things arenít.

McFarland:

To set priorities like I said.

Brysse:

Yes, exactly. It seems to me that ozone assessments have never been or tried to be quite as rigidly quantitative about uncertainties as the IPCC assessments have. Like the IPCC now has ďvery likelyĒ means specifically this, and all that stuff. Why do you suppose the ozone assessments didnít do that?

McFarland:

Talk to Ted Parson. Thatís what he describes about the chlorine loading and EESC. Yes there are uncertainties, but it gets away from talking about those, and I donít think itís mischaracterizing any of it because the uncertainties are in there. Iím paraphrasing what he says; you should get it directly from him and I think itís in his book. Itís the causal link between EESC and the potential for ozone depletion that has been established. How big the uncertainty is in that link though is not the subject of policy debate because there is the link and then you show these extreme scenarios to inform choices about what can be done.

Brysse:

I have read his book, but I will definitely go through that again.

McFarland:

Ask him about the use of the EESC.

Brysse:

Iím really interested in that specifically, because I got the impression — Like I read the 1995 paper by Solomon and two other people where the EESC is first proposed.

McFarland:

John Daniel.

Brysse:

Yes, and a third person I think. I was surprised to see that the paper isnít about, ďHey thereís this new metric, the EESC.Ē Itís about figuring out global warming potentials of ozone depleting substances. That got me thinking, is that the purpose of the EESC? The fact that it can easily be converted into GWP? Yes, this is the look Iím getting from everybody. But if you read that 1995 paper, itís all about what is the —

McFarland:

No, itís the indirect GWP. Isnít it?

Brysse:

Well, I donít understand the math.

McFarland:

I donít remember. Again, old timersí disease. It may be, from what you are saying (I donít remember that level of detail), it may be the indirect GWP because youíve got to know how much ozone depleting substances will impact ozone to understand that. So youíve got to have a metric to figure out how much ozone depletion can offset to the direct GWP of these compounds to calculate a net GWP.

Brysse:

But do you think thatís what the EESC is for? The reason to have the EESC? What does the EESC do that CLP doesnít do?

McFarland:

Chlorine loading (now Iím trying to remember because EESC is used now), but as I remember, it didnít take into account the delay between a concentration in the troposphere and getting into the stratosphere, which has recently been refined by Paul Newman and others because there are different delays for different regions of the stratosphere. Iím sure you caught up with that. It was in the last assessment. Thatís why the Antarctic may be delayed by 10 to 15 years compared to the rest of the atmosphere. When did we hit that 1980 concentration in other parts of the atmosphere? It takes that into account. Did CLP have bromine in it?

Brysse:

You could do a BLP. You could do the same thing for bromine. This is where I get stuck. Everybody thinks my idea about the fact that EESC is for GWP is nuts. But then my question is what good is EESC over CLP?

McFarland:

I donít remember enough about the paper. Talk to Susan about it. Iíd have to look at the paper again, but youíve got to have an impact on ozone over 100 years for a compound, and then translate that into impact on climate and radiative forcing. Then youíve got to subtract that to get a net GWP. So youíve got to have that metric as accurately as you can do it. Youíve got to have EESC to calculate net GWP. Also, it is an improvement over CLP in level of detail on potential ozone impact.

Brysse:

Yes. Good. That sounds like you agree with me: at least sort of, thatís what itís for. I swear thatís what the 1995 paper is about.

McFarland:

Then you havenít talked to Susan?

Brysse:

Iíve e-mailed back and forth with her a little bit and then she talked to Michael Oppenheimer, and unfortunately at the moment it looks like sheís not sure that I know enough that it wouldnít be a waste of her time to talk to me. So Iím trying to come up with a list of really detailed questions for her that are not just things that I could get from reading her papers, which I have done. But yes, this EESC question I really want to learn more about that. I find the use of these metrics really fascinating. For me, the advent of the CLP seems to represent that moment when everyone accepted that ďYes, CFCs are causing ozone depletion, and now we can just talk about chlorine loading potential because we know that once thereís chlorine loading it will go on to participate in ozone depletion.Ē

McFarland:

And that was first in a paper by Prather and Watson, if I remember correctly. The first publication.

Brysse:

Yes, that could be. I was going to say Wuebbles, but heís ODP, not CLP.

McFarland:

I think it was Prather and Watson. I think. Iím pretty sure. I remember when it was first presented to Parties. I think that was 1989 in Nairobi. You can double check.

Brysse:

I think the í89 is the first assessment it shows up in.

McFarland:

I remember parties asking, ďWell what if you did this? What if you did that?Ē As I remember Bob was faxing and calling back to Michael Prather and Michael running calculations overnight, given the time change.

Brysse:

You need the CLP because ODP suddenly got really hard to calculate?

McFarland:

No. ODP is just a number that tells you the relative impact over the lifetime of release of a kilogram of a compound like HCFC22 relative to CFC11. I remember that ODP accepted .055. Now CLP says, ďOkay, how much chlorine are you actually going to have in the atmosphere over time?Ē I actually think there needs to be something equivalent to that in climate and the radiative forcing over time for scenarios may be the equivalent. People have said, ďWell, how about the warming?Ē The further down that causation chain you go the greater the uncertainty gets.

Brysse:

So is GWP similar to ODP? It tells you how much a certain quantity contributes, but you still donít know what the quantity actually is there weíre putting into the atmosphere?

McFarland:

Yes. Youíve got to multiply by the amount to quantify in terms of relative effect. People talk about HFCs having GWPs of thousands. That gives you the impression, ďWow, thatís big.Ē Well, currently they are only a percent or so of the total contribution to global climate change. Youíve got to multiply GWP times the amount thatís getting into the atmosphere, the amount thatís being emitted into the atmosphere.

Brysse:

Okay, good. That makes sense.

McFarland:

GWP has one other thing. I guess it started because CO2 lifetime is — Itís not an exponential decay, and youíve got the carbon cycle models. You know, itís very long lived once you put it in the environment. So the GWP is calculated over a specified period of time, and whatís been accepted as part of the Kyoto Protocol and legislation is the GWP evaluated over the next hundred years.

Brysse:

All this complicated stuff. I think I might have asked you all the questions that I had written down. Is there anything else important that I havenít gotten you to talk about yet?

McFarland:

Youíve got to tell me whatís important to your book.

Brysse:

Iím interested in the different ozone metrics, like I said. Iím also really interested in the role and non-role of heterogeneous chemistry. It seems to me that some scientists as early as — Well, Molina and Rowland mention heterogeneous chemistry in the last paragraph of the 1974 paper, and Crutzen and some colleagues did a model with some heterogeneous reactions in it in 1975 just to see what would happen. So scientists, some of them were trying to investigate whether heterogeneous reactions were important in some way in ozone depletion.

McFarland:

Letís see, who was it that had some sticking coefficients on sulfate? The published value in the literature I remember was 1,000 or more too low. You put that number in a model and it says itís unimportant. So it wasnít until the discovery of the Antarctic ozone hole and how you can get that much chlorine that people started looking at it again and found that experimental error. If that number had been accurate in the first place, it might have been discovered earlier.

Brysse:

There are a couple of other factors too. Like Rowland says he didnít know that there were aerosol particles in the stratosphere. Like any. He said he didnít know that initially. Then other people like Crutzen knew about the Junge layer, but thought that it was too low and too sparse to participate in ozone depletion. I think itís about 25 kilometers, and ozone depletion was primarily thought to happen at 40.

McFarland:

The ozone depletion at 40 — Thereís not a lot of ozone up there. Youíve got to get ozone depletion down lower to have something significant. Whether it happens at 40 and how much ozone depletion there is, itís not going to affect the total column much.

Brysse:

Right. Joe Farman told me he knew about polar stratospheric cloud particles since the 1950s because thatís how long he had been working in Antarctica, but nobody else really knew about them until 1983 or so. I find it interesting that thereís all these —

McFarland:

There may have been enough — Thinking back — You know, what information did we have? You had the polar stratospheric clouds. You had what was known as the Noxon Cliff. John Noxon had measured NO2 with a spectrometer, and as you go north or south into those vortex regions, into the polar vortex, NO2 concentrations just drop like a rock. So youíve got to ask why. So there was information out there that could have pointed in the general direction of heterogeneous chemistry, but it wasnít until the publication by Farman and others that people started putting it together. If you take the published data, like we talked about earlier on the heterogeneous sticking coefficients, it just said itís not going to be important.

Brysse:

I do understand that, but another thing that interests me is that there were some papers in the scientific literature where people were trying to continue to investigate the heterogeneous chemistry and finding, ďOh, theyíre right. This doesnít happen. Oh, theyíre right. This doesnít seem like it would be important.Ē Thereís one paper, I think Molina is one of the authors, where he tests some reactions on ice particles and nothing happens. But they are doing it at only a few degrees below freezing whereas the polar stratospheric ice is really at — 80 or something. If you get it that cold, things really happen.

McFarland:

He had first done some work, and he talked about it, but thought that chlorine nitrate and HCL might react in the gas phase. But it turns out that it was happening on the walls of the container. I donít think that was at low temperatures. Again, memory doesnít serve me well.

Brysse:

I could have that paper mixed up with another paper. It interests me that really none of this made it into the assessments. Even when people are doing scientific papers about the potential importance of heterogeneous reactions you really donít see anything in the assessments. Iíd like to hint that maybe thereís this big unknown that could be —

McFarland:

I know that the Fluorocarbon Program Panel had the modeler Doc Sze [?] of AER do work to answer the question, ďCould heterogeneous chemistry be important?Ē And the answer was no with the rate constants that were in the published literature. So what do you say in an assessment? I donít know if thereís any assessment that says that itís not important, but there was work out there. It was an apparent negative result.

Brysse:

I know thatís another thing I need to talk to Susan about since she was one of the first people to think about heterogeneous reactions on PSC particles.

McFarland:

Itís just hard to imagine that heterogeneous chemistry at those cold temperatures could be important, but it happens.

Brysse:

Apparently it does. I think we might be all done.