Oral History Transcript — Dr. Richard McPeters
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Richard McPeters; June 3, 1999
ABSTRACT: In this interview, Richard McPeters discusses topics such as: National Aeronautics and Space Administration (NASA); Earth Probe Total Ozone Mapping Spectrometer (TOMS); Massachusetts Institute of Technology; University of Florida; Alex Green; atmospheric physics; ozone; NASA Goddard Space Flight Center; Nimbus 7 spacecraft; Pawan Bhartia; Shigeru Chubachi; chlorofluorocarbons (CFCs); Arlin Krueger; Susan Soloman; Joe Farman; Don F. Heath; Al Fleig; Moderate Resolution Imaging Spectroradiometer (MODIS); British Antarctic Survey; Neil Harris; Gordon Labow; Mark Schoeberl.
Norton:My name is Steve Norton, and Iíll be interviewing Dr. Richard McPeters, Principal Investigator of NASAís Earth Probe TOMS. Dr. McPeters, just to confirm what we already discussed, the interview will be taped, transcribed, and once youíve got the chance to review it and make corrections or any additions it will be archived at Neils Bohr Library at the American Center for Physics and be available for future use by historians and scientists and other scholars.
Norton:I want to begin first getting a little background information on yourself. No telling what might come up, but I was actually interested in what your undergraduate and graduate training was in and how you actually got involved over here at NASA.
McPeters:I did my undergraduate work at MIT, degree in Physics. I did graduate work at the University of Florida. Again, Department of Physics, but I was working for Dr. Alex Green in the area of atmospheric physics. In 1976 I came to work with the original ozone processing team who was working on the BUV data. At that time I was working for a company called Systems and Applied Sciences. You recall in the mid-70s this whole problem of the possibility of catalytic destruction of ozone came up in the context of the supersonic aircraft program, and we initially began work on that while I was at the University of Florida. So that was kind of a lead-in that there was an ozone data set that came from an instrument called the backscatter ultraviolet instrument on Nimbus four. That instrument was launched in April of 1970. It had good data for about two years and then there was power problem so there wasnít nearly as much data.
Norton:So you were working on the BUV data —
McPeters:As a graduate student. Actually I had just finished up my degree when I was hired by SASC to work on this. So I was a fresh doctorate. But the point is that originally nobody was interested in ozone. It was just another trace gas, and who cares? In the mid-í70s, all of a sudden it became a big issue, and a group was put together to go back to satellite data that no one had cared about before and process it systematically, and that was the origin of the ozone processing team. So it had been in existence about a year when I began to work with them.
Norton:So the ozone processing team was actually formed here at NASA?
McPeters:At Goddard, yes.
Norton:It was a Goddard group. And it had members from private corporations that were contracting with NASA as well?
McPeters:A group of contractors who were supporting it, supporting a group of scientists who were NASA Goddard scientists. Correct.
Norton:So the contractors would write technical reports and that for whatever the researchers wanted?
McPeters:Our main job was to take all this data sitting on tapes that had never been processed and go through and systematically process it to create an ozone data record. It just hadnít been done before. It was more the sort of a small effort science program where you get data and a little bit of it got published. Nothing was done with it as a whole.
Norton:Was the data primarily total ozone measurements or was it ozone profile data?
McPeters:It was both. To make the distinction, TOMS is sort of a small version of BUV or an SBUV. The BUV and the SBUVs, measure twelve wave lengths from 259 nanometers out to 340, which allows them to do total ozone using the long four wavelengths and the profile using the shorter eight. The creator of the SBUV, Don Heath, had the idea in the mid-í70s to take just the longest four wavelengths, build a specialized instrument that only did those, but did it very rapidly, and then scan back and forth across the orbit path. Then he could map the entire world. This is what he called the Total Ozone Mapping Spectrometer, which was a small version of the SBUV.
Norton:The TOMS actually uses six wavelengths? Itís like two of them are calibration purposes or?
McPeters:It has the same four as the BUV, plus it had two extra reflectivity wavelengths out at 360 nanometers and 380 nanometers. They worried about the possibility that reflectivity might be a function of wavelength and it turns out that it wasnít very much of a function of wavelength, but in the past few years each wavelength has turned out to be useful with use for getting aerosols out of it. It was something we hadnít thought about originally. So, correct. It has two wavelengths that SBUV doesnít. Theyíre very similar.
Norton:So you began work on the ozone processing team, which was the BUV, and then that basically moved over and you started processing the data from the SBUV and TOMS as well?
McPeters:The Nimbus 7 space craft was scheduled to go up in late Ď78 with a double instrument on it, the SBUV and TOMS. The SBUV was a direct descendant of the BUV. Then the TOMS were brand new, but it was a fast version of SBUV. So this group that had been processing the BUV data was the obvious group to fold into the new project and do the data processing right from day one, which is what happened.
So was a whole ozone processing team folded into the — what was it called originally? The Nimbus Experiment team?
McPeters:The nimbus experiment teams were sort of at the high level. They were guiding the science. Don Heath was the head of the Nimbus Experiment team, but those were mostly outside scientists. But a group like that is not the right group to do day-to-day production. So the agreement was that the ozone processing team, which really meant the group of contractors under it, was given the job of doing the day-to-day production processing every day when it became available. At about that time in 1978 I was hired directly into the government from the SASC. So Iíve been with the government since Ď78, pretty much working on the same project.
Norton:So when you got hired the government — I guess Iím a little confused. So you were no longer a member of the ozone processing team and you became a member of this —
McPeters:The ozone processing team had the contractors, but it also had the Civil Service component. So I just changed tasks.
Norton:Werenít you also a member of the Nimbus Experiment team?
McPeters:Not originally. Those of us who did set up a — were part of the ozone processing team were eventually named as a part the net, but originally we were not.
Norton:How many members were there of the net?
McPeters:Something like eight or ten.
Norton:Do you remember their names?
McPeters:My advisor, Alex Green, at the University of Florida was one of them, which was sort of my introduction. I actually donít remember most of the others, but I think I can probably find out.
Norton:The next question I wanted to ask you was about the development of the TOMS data filters. This is what initially got me calling you is Iíve been reading a lot of the literature of the history of it, and everybodyís talking about the range between 180 and 650 Dobson units and being over at Maryland I had access to all the technical reports. So I actually was pulling those up and looking at them and something wasnít coming across right. There was a disconnect between what I was reading in the technical manuals in the historical accounts. And so I talked to you and you told me that the range was actually not for eliminating data, which it didnít appear to be to me from the technical manuals. So you have a 180 DU were flagged as unreliable, possibly due to encoding transmission and instrument error. The flags were monitored. Then you told me that when the TOMS data from 1983 were being checked with quality control that an unusual number of flags appeared. The question I have is what exactly was the basis for determining what constituted too many flags? Was it just prior number of flags or statistics?
McPeters:Statistics. Right now weíre processing data from the Earth probe TOMS. Out of the Earth probe TOMS data sent, if you go and look at the statistics we have flags for profile shape errors, various other things that are algorithm related, others that might be instrument related. To this day, any data sent that we process there will be some amount of data that will be flagged. Thatís why you create the flags in the first place. But the number of data that get flagged tend to be maybe tenth of a percent or a hundredth of a percent range. I canít always tell you why they get flagged. It may be that you are getting three sigma or four sigma noise. If you have enough data points, if you get a quarter of million points a day youíre going to see four sigma event, youíre going to see five sigma. When you have a large enough data set these will occur and when they occur in the right combination, they will be picked up in the algorithm as something really unusual. But what was different about this case in Ď84 when we were looking at the Ď83 data was that it wasnít little sporadic incidents. It was a cluster of these things and they were very persistent. So we started looking at it pretty closely.
Norton:So then the statistical model is based — I mean, you build statistical models of what the expected number of flags should be from transmission and coding and other sorts of things, so you have some idea beforehand?
McPeters:Not really. The way the real world works is you have too much work and not enough time to do it. So it comes down to a matter of experience, that the person sitting there day after day turning this stuff out knows that he expects three or four of these. And if all of a sudden he sees hundreds of them, then he comes and says, ĎHey, thereís something funny going on.í In the world of perfect you would do exactly what youíre saying, and today weíre a lot closer to that. We have plenty of time to do the software. We have automated quality control to go and keep track of the flags, and you can do the plots and all that. At that point, though, we werenít quite as systematic about it. But still there was no substitute for somebody whoís knowledgeable watching it, and he spotted it.
Norton:Weíll get to that question in a second. So the idea is you basically have some idea that youíre going to expect a certain number ofÖ
McPeters:Whatís normal, yes.
Norton:And the errors that you were getting when you were processing the ozone data were just so wildly out of bounds you knew something was haywire?
Norton:So there was no computer processing — there was no sort of computer algorithm that then shut the number of flags to tell you? This was something that was done by hand?
McPeters:When you did the data processing
(you have to remember, this is done on the IBM main frame), the output consisted of these big computer print outs and every time a job went through the guys who are doing the actual production flipped through and circled the last page there of the statistics for the run for that date. It was a matter of a person actually looking at it, but this was part of their job and they did that.
Norton:So there would actually be physically someone in the print out in the number of flags?
McPeters:Right, in each of the flag categories. And there are half a dozen of them or more. They noticed that all of a sudden this one category started getting a lot of hits and brought it to the ozone processing team saying thereís something funny going on.
Norton:So the only thing thatís being done by the computer then is just some sort of automatic calculation of the number of flags. Youíve already defined the number of categories to collect.
Norton:So I guess the next issue I want to get into is the timing. Specifically, the lag between the collection and the analysis. This is something weíve gone over before, but I just want to get it down for completeness. So again, the data for October of 1983 was being analyzed first in July of 1984. What Iíd like you to go into a bit is the logistics involved between the time of collection and in the time of analysis and why it took so long.
McPeters:Sure. You tend to forget the computer environment at the time because we have machines that are so fast. We have connectivity. We have high density data storage. The TOMS data set was a very large data set for its time. The EOS data sets that will be coming in a couple of years are, youíre talking terabytes of data. So at the time it was a challenge. Step one, how do you get the data from the ground station to the place where itís processed? Today if we just FTP it up over the Internet it takes a matter of minutes. At that point, the data was downloaded, I believe in Wallops. It was recorded on the 6250 bpi IBM tapes. As I recall, they were actually mailed up here. Meanwhile, once we got the tapes, we had to do a certain amount of data set merging. For instance, when one of the data sets was brought in, we had to get the definitive satellite ephemeris so that we would know that this scene was taken at precisely this location and that the solar zenith angle is precisely this.
Norton:Doesnít that come down with the regular data measurements?
McPeters:No, no. The spacecraft doesnít know where it is. Thereís a group called Flight Dynamics. The group is still here at Goddard to this day doing the same job. Even for the Earth probe spacecraft, if we want the definitive ephemeris, which is the absolute most accurate, it takes some weeks after the event before they have the definitive space craft location and attitude.
Norton:There is some information coming from the satellite that theyíre using to determine the satellite ephemeris?
McPeters:Thereís a predictive ephemeris, and in the mid-í80s, especially as getting the ozone data in a timely fashion became more important, we realized that we could switch over from waiting for the definitive to using a predictive and come pretty close. Thatís what we do with the Earth probe processing today. We use a one-week-old predictive ephemeris. Turns out if you use a four-week-old predictive you start making significant errors because of the atmospheric drag, which varies depending on the solar activity. So today we use the predictive. But at that point we used the definitive, and that took a little while.
Norton:So again, the definitive ephemeris is basically that you get some information from the satellite and they basically —
McPeters:Actually, I donít know precisely how they do it. I know one the input is, say, radar data. When we had some problems with the spacecraft and we werenít quite sure where the spacecraft was, and Norad was able to use radar to tell us pretty closely where it was. Itís an interesting field that I donít know much about, but itís an external data set. Itís great. Today you can put a GPS receiver on a spacecraft and it does know where it is, but thatís new technology.
Norton:Who would I be able to talk to find more about how the definitive ephemeris were calculated?
McPeters:Itís not a crucial point here.
Norton:I know itís not crucial for this history, but I mean itís something I —
McPeters:The flight operations team guys could probably give you a name. Theyíre actually located in the building right next door, and thatís where they TOMS control center is. The data, every day, is downloaded at wallops at midnight and at noon. Its FTPíd up here. The flight operations team, right next door, does the actual spacecraft control. They put together the command loads that tell the space crafts do this and do that, and they receive the data, strip it to what we call a level zero data set, and then itís sent to our computers. Then we process it to level one where you calibrate the radiances, to level two where you turn it into ozone, and then level three, which is where you grid it. The STI (computer) sitting right there is the back-up product processor for the TOMS. The primary machine is just a couple of doors up, and thatís where the TOMS data is actually processed. But if that one ever fails this one is set up identically so it could take over and continue to do the processing.
Norton:So this is pretty much the same process that occurred in 1984?
McPeters:In 1984, they would get the tapes; they would mail them up here.
Norton:Other than the FTPs?
McPeters:After a while, somebody would catalog them put them in the tape library, then they would wait for the definitive ephemeris to come in. I believe at that time we were getting the snow-ice data from the Airforce. We have a problem that you need to know whether or not youíre over a cloud, because clouds are up here and the ground is down there. The only way we have to tell if itís a cloud or not is if itís a very high reflectivity, but over snow and ice then thereís an ambiguity. So we were taking the snow and ice data sent from the Airforce and merging that, getting the (solar zenith) angles and merging those. Plus, just physically swapping tapes in and out took a while. So we were running about nine months behind.
Norton:So how long did it actually take to get the ephemeris from October of Ď83? I mean there was stuff you could do in the meantime without the ephemeris, right? Or do you have to wait?
McPeters:Well, we ended up using a predictive ephemeris and that provided us a fairly fresh prediction that would get you pretty close the angles that you need. But there was no urgency. We were running nine months behind, but we thought that was a pretty good pace. So there was no one out there demanding the data more quickly than that.
Norton:So at this time, as far as the NASA team was concerned, no urgency whatsoever. Whereas Farman, he pretty much thought he was onto something by July of Ď84?
McPeters:He had the data from just one station there, going back to 1960. So he was very much focusing in on this one location and seeing this change in ozone. So he picked it up much more quickly than we did.
Thereís a point here. The ozone processing team had one job and that was to process the data and get accurate ozone. The analysis of the data wasnít really the job of the OPT. We would create the data, and then other scientists were supposed to take it and look at it. Thatís to say, a little bit of a fault. Today, when we process the ozone data, itís absolutely true that the best quality control you could have is to have scientists looking at the data. You can consider that part of the quality control. So it was a little bit of a blunder on our part that we werenít doing the geophysical analysis, and we felt like thatís not our primary job. Our primary job was to do the crank turning and get that data out there. So what we were not doing was taking zonal means, for instance, and looking at those as a function of time, or ozone at a location as a function of time. We werenít looking at what Farman was looking at.
The second point is satellite data sets are big. We have data from all over the world, and there are plenty of things going on. There are other problems we were looking at. So we werenít focusing on this one thing until it popped up out of the weeds.
Norton:Is there some way to find out exactly when all the pieces came together so far as when the data arrived, the exact data to arrive from Wallopís Island? The exact date you got the definitive ephemeris? The exact date you got the — was the Airforce —
McPeters:P.K. can probably answer some of those questions a bit better. I do have some records that Iíve dug out that are interesting. Let me get this in the right order. These are the minutes of the ozone processing team. August 30th it was written up. This was for the July 31st meeting. This is the relevant issue. Lee was the fellow who was in charge of doing the actual production processing. Heís the one who was literally hanging tapes, his people, getting the printouts and looking through them. They say here that, (Production: Lee has reported the problem with the October Ď83 ozone data in the Southern Hemisphere. SBUV and TOMS thatís both instruments, not just one of them) report ozone values of about 180 DU over Antarctic. Whereas, Dobson reports 350.í
Norton:Thatís referring to the South Pole station?
McPeters:This is the South Pole station. So he was doing his job. He saw something funny and had already done the first step, which is ask what does the ground base data say? Now P.K. was the one who was in charge. At that point he was still with SASC. He was a contractor doing the processing. Now heís also with the government. As a matter of fact, heís the branch head here in 916. Bhartia noticed that the low values disappear as latitude decreases. So itís systematic. He does not believe that the problem could be with the ILTs, which is the image location tape. One way to get that error is the ephemeris. If the spacecraft thinks itís here, but itís really there you can get exactly this kind of behavior. We have actually run into that problem once.
Norton:Yes, I actually heard something that Heath was saying that in an interview with someone else. But at this point, August 3rd, Bhartia —
McPeters: He pretty much ruled that out. He said, ĎWell, itís the software.í He says, ĎThe possibility that there may have been a cloud at 40 millibars in October is being investigated.í If you have a thick polar stratospheric cloud, which turns out really does happen. Itís part of what goes on and what creates the ozone hole. That was a possibility.
Norton:Would a cloud like that pretty much have to be over all of Antarctic?
Norton:They donít normally get that big, do they?
McPeters:As it turns out they donít, but at this point all we knew is there was something funny going on. One way to get it would be if you had a cloud that was really extensive and at very high altitudes. So that was a possibility we were looking at. Letís see, this is a week later for the August 7th meeting. ĎRegarding the Southern ozone discrepancy with Dobson in October Ď83, Bhartia has spoken with the Langley group operating the Sam II instrument.í Thatís the stratospheric aerosol instrument. ĎThey report no 40 millibar cloud in October of Ď83.í So we followed up and found error.
Norton:That eliminated one source.
McPeters:Unfortunately, I kind of wish I had the whole series of these (OPT reports), but I found some.
Norton:You think Bhartia or someone else might have more of them?
McPeters:The SASC became STX, which became Hughes STX. Theyíre now re-organized, but a lot of the same people are still there and it may be that they can have some that fill in.
Norton:I can get copies of these.
McPeters:One interesting quirk is in September of 1984. Every four years thereís an ozone symposium in Greece. That was in September, so a whole bunch of us were writing papers for that and we disappeared for several weeks in September. Thatís one reason thereís a little bit of a hole in my record, at least.
Norton:You guys didnít report anyóbecause Iíve read a lot of the papers in that ozone volume and one from Ď88. But in the Ď84 conference you didnít report anything there.
Norton:You can maybe correct my pronunciation. I was wondering about Chubachi. Now, he didnít report low ozone at that conference.
McPeters:Well, thatís interesting. This is a copy of Chubachi. Someone else was asking about this. Actually, see that blue book right there?
McPeters:Those are the original proceedings. This is a Xerox side of that. Thereís a few interesting things. This is Chubachiís paper. He says, ĎThere are only two ozone stations operating at high latitudes in Antarctica. Syowa Station at 69 South and Amundsen Scott at 90 South, where the total ozone has been observed in sunlit spots only.í He doesnít know that the (Halley Bay) ozone exists, and pretty much we didnít either because the British Antarctic survey doesnít have a record of their data at AES ĎAtmospheric Environment Service) up in Canada. I donít remember if we knew they (Halley Bay) existed. We certainly knew that there was no ozone data from them that was going to do us any good. I suspect that we didnít even know they existed. And Chubachi doesnít here.
Norton:Now, I actually read a book by Susan Rhone, and she actually interviewed Sherwood Roland.
Norton:About this, and he says that — I donít think he recalls Chubachiís paper, but —
McPeters:I donít either and I was there.
Norton:What he does recall is that there was no discussion about anything abnormal so far as low ozone levels.
McPeters:Whatís interesting, though — this is what I was looking for where Iíve marked it a little bit. This is the figure. Thatís the ozone hole. Thatís it. Itís right there in his data.
Norton:Whose paper is this?
McPeters:This is Chubachi. This is the other copy I was looking for. But notice his interpretation. ďA sudden increase in the total ozone occurred on October 28th.Ē So heís focusing on the going up. Chubachi sees it. He doesnít recognize it. In a sense, heís doing the same thing that the O.P.T. did, and he sees something there and doesnít know what he has.
Norton:Well, it seems like what heís doing is heís focusing on the fact that itís going up as opposed to it going down.
McPeters:That there was a sudden recovery — the sudden increase. That was the thing he focused on rather than the decrease. When P.K. wrote his abstract for the meeting the following year about the anomalously low ozone, he at least keyed in on what the different was that it was low. It was a little bit later, though. But in both cases you have to give Farman credit for one thing. He saw that it was low and going down, but he made that connection with the CFCs. Chubachi wasnít even focusing on the fact that it was going down; he certainly didnít focus on the fact that it was CFCs. Now, the interesting thing is that the branch here (at Goddard) is pretty big. There are components that do the ozone measurement (thatís us), there are components that do the ozone modeling, plus there are three-dimensional modelers who try to get the dynamics of the atmosphere. As soon as Farmanís paper really hit the market and they started to hear about it, some of them, Rich Stolarski in particular, immediately realized that this is very significant. The interesting thing is they read Farmanís paper and said, ĎHeís obviously totally wrong. Itís not a direct CFC connection. It doesnít matter, though. Heís onto something.í
Norton:That was Stolarskiís initial reaction that it was all the CFCs?
Yes, the people who were really into the modeling all knew that what he was proposing was wrong, but he had raised a big flag, and immediately there were a lot of people working hard on it. Probably May of '85 — the paper came out in March, I think.
Norton:Actually, it came in May. Iím almost positive it was May.
McPeters:Yes, you could be right.
Norton:But I think probably a lot of people would have known about it. Because I think Susan Soloman was one of the reviewers on the major paper, so she would have known about it right about the beginning of Ď85.
McPeters:Yes. We didnít get an early warning from her. Now, the real piece of irony. The principal investigator for the Nimbus 7 TOMS was Arlin Krueger, who occupies the office right across the hall here. Someone was telling me, and I actually havenít confirmed it with him, that he had actually reviewed that paper or someone had shown it to him and he thought, ĎOh well, thatís interesting,í but he didnít really follow up on it either. So thatís kind of a missed opportunity.
Norton:Because I actually read a number of papers by Krueger and it looks like someone else here at NASA that were published in the reviews of Geophysics on the issue that was on the ozone depletion. That big issue where — I think it had two papers in there where he was pretty much saying that it wasnít chemistry that was doing it. That it was some atmosphere dynamics that was causingí
McPeters:Are you thinking Krueger or Schoeberl?
Norton:Maybe it was Shhoeberl and Heath. Maybe thatís what it was. For some reason I keep getting Heath and Hoover mixed up in my head.
McPeters:Well, Don Heath is the one who designed the original BUV and the SBUV. He is extremely good at the instruments. Heís the guy who hired me into the government and he still works with us on instrument design. Kruger was in Donís branch, and he was the one put in charge of the TOMS instrument. So Kruger is more the instrument person. Mark Schoeberl is more a theory person. Susan Soloman is more of a theory person.
Norton:Well, Schoeberl I think was definitely an author on the paper. Thereís another one that was in the group that was an author, too.
McPeters:Heís not really the specific one. I do remember a year or so after the whole issue came up and everybody was trying to figure out exactly what was causing the ozone hole. I remember being in a meeting where Susan Soloman was pushing heterogeneous chemistry in ice crystals and Schoeberl was pushing dynamics, and Susan won. But there were a lot of people with different theories at that time because nobody knew until some more data came in.
Let me show you two more pieces here. By late September, the October 1st meeting, we were still trying to figure out what the heckís going on. Anomalously low ozone over the Antarctic. Instrumental problems in clouds have been ruled out as causes. The TOMS also measures the ozone. The Amundsen Scott station does not measure during this period. A possible explanation could be a short-lived anomaly in the spacecraft attitude.í Namely that instead of looking straight down itís actually looking over here and weíre assuming that itís looking there and causing error. So at the end of September we still had the idea that it could be something wrong with the data.
Norton:So at this point nobody is like really jumping around thinking, ĎWeíve really got something here.í Itís pretty much we probably have a serious problem and weíve got to figure out what the problem is.
McPeters:We didnít get really excited until the theoreticians jumped on it and said, ĎHey, this is something going on. This is very significant.í
Norton:The theoreticians here.
McPeters:The experimental group, we thought, ĎWell, thatís odd.í But we never did get that excited because we didnít understand what it was.
Norton:And that includes Bhartia?
McPeters:Yes. By late October, okay, ĎKrueger showed that TOMS detected low ozone values in the Antarctic, and that the low ozone values were localized to just one or two distinct areas. He reported that areas of low ozone in the region have occurred on previous occasions as well.í Itís taken us about two months to really go back and start looking at the history of this, that this is not something that just happened this year, but itís happened before. Weíre finally starting to do the right thing, but it took a while.
Norton:This is October then of Ď84?
McPeters:October of Ď84. He was finally looking at previous years and saying, ĎWell, this is not a one-time event. This is something that has been going on.í
Norton:So why wasnít it going on? Why hadnít it been picked up before?
McPeters:Probably it had more to do with Ďthe fact that) it takes a fair amount of time to go look at these, at what was considered to be a big data set. I just donít have a good answer. In 20/20 hindsight, if weíd immediately looked at previous years we would have had a lot better clue that this was not an instrument effect but that it was something geophysical. So we were slow to look at that. By a little bit later than that I personally had looked at some profile data from the instrument and reported back that thereís just nothing funny about it — that whateverís going on looks real. And by that winter I think weíd all gotten to believe that there was something. We believed our data no matter what the Dobson said.
Norton:When did Bhartia submit his abstract?
McPeters:Letís see, where did that go?
Norton:It was at a conference in Prague in July of Ď85?
McPeters:March 28th is when the letter submitting the two abstracts, one including an observation of an anomalously small ozone densities in south polar stratosphere during October Ď93. So it was March 28th.
Norton:So this was before Farmanís came out?
McPeters:This is something P.K. had written to Stalarsky at one point. ďThe first announcement of NASAís discovery of the ozone hole was made at the fifth assembly of IAGA / IAMAP Assembly Prague in August, 1985, less than three months after the British paper appeared in Nature. An abstract of the paper authored by me, D.F. Heath, and A. Fleig was submitted on March 28th, by coincidence on exactly the same day that the British paper was accepted by Nature.Ē Thatís what I was looking for.
Norton:It was accepted on the same day that he submitted the abstract. And so at that point you didnít know about Farmanís results untilÖ?
McPeters:Most of us didnít know about the results until it came out in Nature. I hadnít heard anything about it until the Nature came out with it.
Norton:By the time that abstract was submitted, it was pretty clear that it was something serious going on over the Antarctic?
McPeters:We believed our data, that we really were seeing some low ozone.
Norton:And at that point, though, you didnít know what was causing it? You had made no connection with CFCs or anything?
McPeters:We kind of made the same error that Chubachi did, that it was low ozone, but we didnít get excited about it. We didnít understand what we had.
Norton:See if I need to go over this becauseÖ As I said, one of the books I looked at was the Ozone Crisis by Susan Roan. Itís actually got a little bit more accurate history than some of the other ones, but she seems to be waffling on certain points, too. She says in one paragraph that NASA missed it because the computer programs eliminated the data. Then on the other hand, and apparently she had interviewed Don Heath, and she says that he said that, ĎNo, we were looking at it at the time.í So she never resolves that conflict.
McPeters:Well, what Iím telling you here is that by the end of July, as soon as we get that part of the data where the data was being Ďthrown outí and the flags were set we were trying to figure it out, but we really suspected that it was our instrument.
Norton:How was Don Heath involved in this? From this account here it seems like he was heavily involved in the analysis. But what Iím hearing from you, Bhartia was one of the key people.
McPeters:Well, Don was the principal investigator for SBUV in this. But for the TOMS it was all Krueger. So he was sort of the high level scientist. Don used to come to the ozone processing team meetings occasionally, but certainly not to everyone. Arlin Krueger would come occasionally.
Norton:They werenít actively involved in?
McPeters:They were active, but not intensely involved. At that point I was a pretty junior low level scientist and I was much more focused on it. I used to come to all the meetings pretty much. So I tended to be there. Don wasnít. He was looking more at new possible instruments, and he was particularly interested in the solar flux measurements from the Nimbus 7. That was more his thing. Whereas P.K. and the OPT group, that was their job — to process this data. So they were really focusing on it, of course.
Norton:So anybody else I havenít identified yet so far as I need to talk to that was involved in the actual processing? I mean you had mentioned the person Lee?
McPeters:Oh, he was sort of a lead programmer type. Actually, heís long gone. I think heís moved out to Texas. I kind of lost track of him. He hasnít been involved in a long time. P.K. was actually in charge of it and heís here. You can talk to him now if you want. The head of the ozone processing team was Al Fleig. Heís also here locally. As a matter of fact weíve started working with him again. Heís going to set up the data processing system for this new instrument weíre working on. Itís the ozone monitoring instrument on EOS Chem (Aura). Right now heís working with setting up the MODIS data system. If you know anything about that, with MODIS weíre talking terabytes and data, rooms full of computers running parallel.
Norton:This is all ozone data orÖ?
McPeters:MODIS is a lot of chemistry related measurements — itís a lot more species than just ozone. But the point is, Al was the one who was in charge of the OPT then, as you can see from the minutes. Heís around, and you can talk to him sometime if youíd like.
Norton:Yes, Iíll definitely do that. But Lee, from what you were saying though, is the first person that actually saw the number of flags?
McPeters:And he immediately went to his boss, who was P.K., and he brought it to the OPT.
Norton:Basically, though, I guess the second half of Ď84 you were trying to determine whether or not if this was an artifact of some error or something and then you determined itís not. At what point were the pretty pictures made? The graphics made that really show the —
McPeters:Summer of Ď85.
Norton:Summer of Ď85. Was it before that conference in Prague?
McPeters:The Farman paper came out in June. Very quickly, because we had the modelers and theoreticians in our branch, who for years didnít care much about TOMS data, all of a sudden it was important. Once that was realized, we actually developed a lot of this capability to do the imaging. And again, you have to remember the computers and the environment. We used to take printouts and flip through them and plot numbers one by one. You wouldnít even think about doing that today. But more particularly, when you get large data sets you have to be able to do things graphically, and the tools were actually created immediately after the ozone hole was discovered and we started analyzing it. So thatís what drove us to create a lot of this stuff.
Norton:So a lot of heavy duty effort went into developing visualization tools.
McPeters:Thereís one interesting story. I was visiting the British Antarctic survey eight or ten years ago. I was talking to this fellow over a beer and he said, ĎI named the ozone hole.í I said, ĎWhat do you mean?í He said, ĎJoe Farman was giving a talk in our lab. So I announced the thing and I said Antarctic ozone hole.í And Farman came to and said, ĎThereís no reason to think itís an ozone hole. Thereís no evidence of that.í He objected to the name. It wasnít until we made the first TOMS pictures that showed it really was an ozone hole and you could see it. The name caught on and stuck. He claims credit for inventing it.
Norton:This was someone that was working at the British Antarctic?
McPeters:The British Antarctic Survey. Iíve forgotten his name, but he was over at the British Antarctic Survey.
Norton:Maybe when I go visit them theyíll be able to track him down.
McPeters:Have you talked to Neil Harris?
Iíve actually e-mailed him, but Iím probably — the only people Iíve scheduled to interview are Farman, Gardner, and Shanklin. Iím probably going to interview more people while Iím over there.
McPeters:Neil Harris was working for Sherry Roland in the late Ď80s when we started doing this ozone trend analysis. He was a graduate student at the time, but I think heís now in charge of one of the groups over there. So Iím sure youíll meet Neil at the Arctic survey in Cambridge.
Norton:I know Farmanís retired. Itís very difficult trying to get in touch with him because he doesnít use e-mail.
McPeters:Well, heís always tough to get to. I was visiting over there and ran into him in the hall.
Norton:When did you actually hear about the anomalously large number of flags? Was this in one of the OPT meetings?
McPeters:That July 31st meeting. I was actually there. If you look at it (the minutes), you know, weíre looking at a number of different things. That was one issue that came up, that thereís something funny going on.
Norton:One more problem to deal with from the data.
McPeters:It wasnít that it was this big flash of light or anything. It was just one more problem of a series of them.
Norton:Do you actually remember when you realized that this was actually something real and not an artifact?
McPeters:One of the things the instrument can do is to sweep through the spectrum instead of measuring twelve discreet wavelengths, and that was something that I was especially interested in. I was doing some research on nitrous oxide by looking at the spectral structure. One of the things they had me do was to go back and pull the data for that period of the ozone hole and see if the spectrum looks reasonable or if it looks like it might be an instrument artifact. Towards the end of October I came back and said the spectrum looks perfectly reasonable. Thereís absolutely nothing funny about it. I think itís real. The reason is short wavelengths, which is where you would probably see instrument effects, originates very high in the stratosphere. If youíve read about the ozone hole, that is not affected at all. All of the effect is in the fifteen to twenty-five kilometer region at the bottom (of the stratosphere). So the upper stratosphere was unchanged; it looked perfectly normal. So I came back and said, ĎI think itís real.í That was my personal involvement.
Norton:Weíve already gone over what things were checked. The Amundsen Scott station sent full data. When you were checking all this other stuff I know you had mentioned something about Bhartia thought there was something wrong with the Dobson data from the South Pole.
McPeters:Eventually we had a problem that if we believed our data, then the South Pole data had to be wrong. The real question is, if you look at the several years of the South Pole data it would have been immediately obvious that the October Ď83 data was totally different.
Norton:The South Pole data?
McPeters:Right. So the question is did we look at that? I donít remember that ever coming up or if we did look at it.
Norton:Thatís right, because you had just showed me the thing where you said that Lee had checked the Dobson data and the October data was like 350 DU, which is anomalously high compared to previous measurements.
McPeters:If he had looked at Ď82 where it was 210 you probably would have caught on a lot earlier that, ĎHey, there may be something wrong with the Dobson data.í
Norton:Maybe thatís something I can ask Bhartia about directly because I know there was the — This is one thing I havenít seen yet, the red book that has the ozone data in it and the, I guess, sort of some wave pairs that were used.
McPeters:Yes. This was a paper in, I guess it was Ď86. There was a special issue of GRL. This was a paper by Walt Komhyr. Iíve worked with Walt for years and pressed him on this. This is the only statement heís ever made in print about what went on. Walt is based in Boulder. He was in charge of the entire U.S. Dobson network, which included the South Pole station. So, first of all, he was in charge of this data at the time, but obviously he was not at the South Pole taking measurements. So this is the only statement that he made, ĎThat data previously reported for October Ď83 had been identified as erroneous. It was measured in wrong wavelengths pair: A prime, C prime, D prime, rather than measured in A, C, D. Thatís the only statement on what went wrong there that appeared in print.
Norton:I guess thatís something Iíll ask him when I talk to him.
McPeters:Are you going out there?
Norton:Yes, Iím going out there to talk to him and Bob Evans, who I guess was in charge of the day to day calibrations. Thatís what Iíve been told.
McPeters:Yes, he certainly is now. I didnít remember if he was doing it in Ď83 or not.
Norton:It was Gordon Labow. He had actually said that he thought that Evans was in charge of the day to day calibrations back then. Thatís something Iíll have to check on before I actually go out there.
McPeters:Yes, Gordonís actually a couple of doors up here. Iím not sure, but I know Walt was in charge back then.
Norton:Another question I guess for the analysis of the data was the length of the TOMS record. Because the instrument only went in Ď78, I guess. It was November of Ď78 so you didnít have measurements on the Antarctic decreases. It was spring then. So you had a much shorter record than Farman did. Did that effect the — well, I guess in some way it wouldnít. Because I mean that you were saying that 300 people werenít even looking at the data.
McPeters:We werenít really looking at it in that particular way until we realized a little bit what was going on from the theorists. Once that happened we did have the old BUV data, and that was something that I worked on personally, going back to the Ď70, Ď71, Ď72 time period, and it looks just like Ď79. So very early we had that established and it was doing one thing and all of a sudden it started down. We actually had the pieces in hand; if you looked at the right things we could have figured it out.
Norton:Thatís always the problem, isnít it?
McPeters:Oh, yes, knowing the right thing to look at.
Norton:Well, I guess one thing, too, is what is your feeling on Farmanís paper and the interpretation of his results? Because I know there was this paper by Susan Soloman that came out shortly thereafter in Ď86 where she was saying that there was still the problem of large scale waves that could have been responsible for the fluctuations in the ozone at Halley Bay, and that she seemed to be suggesting that Farman and his team didnít really deal with that issue too well in the paper and that was still open.
McPeters:Yes, probably true. As I say, for some time there was a lot of controversy on proving what was causing the ozone hole. The two strongest theories were Susanís approach that it was chemical, but the key was they knew enough about the chemistry that they knew for certain that just increasing the chlorine, which is what Farman was talking about, wasnít nearly enough to do it. You had to have another key element in there and Susan figured out that the heterogeneous chemistry on the surface of an ice crystal could be the accelerator that you had to have. She turned out to be right. The other possibility was Mark Schoeberlís theory that dynamics or some kind of wave thing could do the same thing. If you think about it, ozone is very low. At low altitudes it gets higher, and then it decreases again. If you take low altitude air and move it up you decrease ozone. So vertical motions can give you changes in ozone, and the trick is to tell the difference between that and chemistry. There are ways to do it, but you need good measurements. Itís not just a total ozone.
Norton:Do the atmospheric dynamics at all account for any of this decrease?
Norton:Whatís the status of — one of Schoeberlís papers I read where theyíre talking about, I forget what latitudes it was, but it was from the South Pole to a certain latitude where you had the decrease over Antarctic, but you had an increase at the lower latitudes, and he says that pretty much the total amount of ozone was conserved. So that was a reason for thinking the atmosphere of dynamics.
McPeters:I think they were kind of making that argument at one point. After all, you do have a certain polar height, but I think the actual data didnít support it very well. That as time went on the highs got lower and lower and there is a general decrease over the Southern Hemisphere on an average basis. I certainly believe that at some point he was making that argument, but as more data came in it didnít hold up. I know that. Again, Markís in our branch right down the stairs. Lots of people here had their hands in the fire.
Norton:One other thing to ask you, too, is the thing about Stolarski, his comments he made in 1987. I better ask him about this too, but the comments made in 1987 Nova broadcast where he was basically, ĎYes, we missed it.í When Farmanís paper came out we went and processed the data and low and behold there it was. Have you talked to him about that?
McPeters:The morning after that aired I went into his office and I said, ĎRich, you donít know what youíre talking about.í I jumped all over him. Heís still a little sensitive to this day.
Norton:So if I ask him about this —
McPeters:Heís been harassed enough. This is the letter I had forgotten existed. This is a letter P.K. wrote to Rich immediately after that taking him to task about the whole thing. I thought it was interesting to dig that one out.
Norton:Deeply hurt by the allegations. Actually, I guess weíre almost done with this tape. I think Iím pretty much all set right now. I think Iíve uncovered a number of things, which have been clear so far as the timing. Iíll be able to go from here. As I say, Iím going to pretty much try and get everybody first, then probably go second and clarify things and all of that.
McPeters:Youíll probably get a little bit different story from different people, but I think the basics of it are there.
Norton:I think the basic point is that you guys didnít screw up.
McPeters:We didnít screw up, but we made the same mistake Chubachi did. We didnít know what we had. We just missed it.