Ray Weiss

Ray Weiss

Professor Emeritus, Scripps Institution of Oceanography, University of California San Diego

By David Zierler, Director of the Caltech Heritage Project

December 12, 2023

DAVID ZIERLER: This is David Zierler, Director of the Caltech Heritage Project. It's Tuesday, December 12, 2023. It is great to be here with Professor Ray Weiss. Ray, it is great to be with you. Thank you so much for joining me today.

RAY WEISS: Thank you for initiating the interview, David. I greatly appreciate it.

ZIERLER: Wonderful. Ray, to start, would you please tell me your current title and institutional affiliation?

WEISS: I am a Professor Emeritus at Scripps Institution of Oceanography, which is part of UC San Diego. I've returned to active duty as a Research Professor. I am still doing work. The University of California had a very liberal retirement system when I joined, and it turned out to be economically wise to retire and return to active duty.

ZIERLER: As a Research Professor, does that mean you get to continue doing all the fun stuff and you don't have any of the administrative burdens?

WEISS: That's exactly right. I had some significant administrative burdens. I was responsible for all the academic reviews and appointments, overseeing all of that and serving on many committees for 13 years. As a returned-to-active-duty person, I can mostly do what I want to do, which is mainly research and advising and having graduate students and postdocs.

ZIERLER: We'll start at a very broad level. What kind of a scientist do you call yourself?

WEISS: Well, when I'm having cocktail-party conversation, I call myself a fallen chemist. [laughs]

ZIERLER: [laughs]

WEISS: I was a chemistry undergrad at Caltech, and I got into geochemistry in my senior year. I was at Caltech from 1960 to 1964. In those days, and to some extent today, chemistry was divided between physical chemistry—which was basically quantum physics and how reactions work—and organic chemistry and biochemistry, which of course has grown enormously in the intervening years. Caltech had, in the sophomore year, introductory courses that were not required in the freshman year. They were in geology, biology, engineering, and astronomy. I don't know if I've left anything out. I was attracted to geology and applying chemistry to geological problems, so in my senior year I went to work for Sam Epstein, as my undergraduate advisor, and I was hooked.

ZIERLER: With geochemistry, does that mean no matter where the siting of your research—the oceans, the atmosphere, lakes—it's geochemical processes that you're focused on?

WEISS: Yes, it is, and in my career, it has been using chemical measurements and chemical tracers to study natural processes. For example, deep ocean circulation can be studied with time-dependent tracers that are measured in the ocean, and that's one of the things I did a lot of earlier in my career.

ZIERLER: Have you done a lot of field work or are you generally a user of data that comes from other expeditions?

WEISS: I think I'm mainly a field person. Even today, when I don't go to sea anymore because I'm working mainly in the atmosphere, I'm a measurement person, and I'm hands on, and I don't just buy boxes and turn them on and believe what they generate. I get involved in how things work.

ZIERLER: What have been some of the major research questions that have propelled your academic career? What have you focused on?

WEISS: In the beginning of my career, it was understanding deep-ocean circulation rates using chemical tracers. That involved things like measuring dissolved gases and things that are altered in the deep ocean as a result of biological processes and mixing and transport. It was a pretty exciting place to begin my graduate education at Scripps. It was the time of Roger Revelle, who really was the man who founded UC San Diego. Roger was very good, as they were at Caltech in those days, at hiring a lot of good people, including many who came from the University of Chicago and wanted to go to California. Gerry Wasserburg at Caltech was one of them. Sam Epstein was one of them. A lot of people went west in those days after World War II and into the 1950s, and Roger Revelle recruited a lot of them here at Scripps. So, it was an exciting place, working on all kinds of different problems.

As you mentioned earlier before we started recording this, the issue of seafloor spreading and continental drift and problems to do with the carbon cycle—Dave Keeling was here, Charles David Keeling, who had the foresight—I think he got the original interest from Harrison Brown at Caltech to study CO₂ in the atmosphere. He was the one who figured out that you really needed to go to remote places and make measurements at the South Pole and at Mauna Loa in Hawaii to understand the global cycling of carbon and CO₂. All that was happening at Scripps, and it was an attractive place for me to go after I left Caltech. I think then and now, there was a tradition that you didn't stay where you were when you went from being an undergraduate to a graduate. Scripps was one of my options.

ZIERLER: You mentioned that atmospheric work came a little later in your career. What were the circumstances for you getting involved in atmospheric science?

WEISS: One of the things that I've done a lot in is using atmospheric trace gases and their solubilities as time-dependent stamps on how the ocean circulated. One important emphasis there was on the CFCs. Beginning in the 1970s and 1980s, we were using dissolved CFCs as conservative tracers in the ocean. All you had to know was the history of the concentration in the atmosphere and the solubility in order to basically have a time stamp on surface ocean water which would then sink and circulate into the deep ocean, mainly from cold areas of course, because cold water is denser than warm water. To do that, I had to measure atmospheric CFCs and reconstruct a history based on commercial manufacturing data and things of that sort, because there weren't a lot of data on the time trends of CFCS and that was the calibration for the clock. I got interested in doing that.

I also got interested in measuring nitrous oxide, which is also the natural modulator of the stratospheric ozone layer. Of course, in the 1970s and 1980s, this all became a very big deal because of the depletion of the ozone layer. In the late 1980s, I was asked by a colleague of mine at MIT, Ron Prinn, if I would take over the experimental side of a joint experimental-modeling initiative that he had started, to answer the question of whether the Montreal Protocol was working or not, by actually measuring what was in the atmosphere instead of believing all the countries' reporting. Countries were required to meet certain restriction constraints on the amounts of CFCs they were manufacturing, and there was some uncertainty about whether that was actually working. The real answer, by the way, was "yes", it was working, and it did work. It has been a remarkably successful treaty.

Because I was doing a lot of work with these compounds already, I was invited to take over the experimental side of this project, which is now an international collaboration called AGAGE, Advanced Global Atmospheric Gases Experiment, that involves 13 countries. We built, here at Scripps, the central calibration laboratory. We developed the instrumentation. We built the instrumentation and put it all over the world. Now this is even going commercial, with networks being built in China and elsewhere, and monitoring emissions in the atmosphere has some traction. I took this on because I thought I could do it and because I thought it was immensely important, but I remember having sort of a swallowing feeling, because if it got to be really big, which it has, I would have to give up the things that I was doing then and take on these new things. It has worked out well, and that is one of the reasons I haven't retired yet, because it's so important to do this.

ZIERLER: You mentioned the Montreal Protocol and ozone depletion. I can only imagine how relevant your research also is for climate change in general. Have you gotten involved on the policy side of things? Have you been a member of boards or governing bodies that really have a hand in climate policy?

WEISS: Yes, I am involved, but one is never sure whether it had much of an effect. [laughs] There's a lot of bureaucracy. We're having this interview at the time of the end of the COP28 meeting in Dubai where the scientists are already beginning to say that not very much was accomplished. When CFCs were successfully banned by the Montreal Protocol, there was a time when people were afraid that the applications for which CFCs were used wouldn't be doable any longer, but that turned out not to be true. The chemical engineers were brilliant at developing new compounds which could do the functions of refrigeration and solvents without having long lifetimes in the atmosphere and without containing large amounts of chlorine and bromine, which are the components of the CFCs that destroy ozone. For example, many are fluorinated compounds. Fluorine doesn't play a role in the stratospheric ozone depletion. But it turned out that all these new compounds that were taking the place of the CFCs were potent greenhouse gases. This project that I am engaged in now measures over 50 compounds in the atmosphere, and many of them are not ozone depleters. So, it was a natural progression to go in that direction. Plus of course being here at Scripps with the Keeling CO₂ record and other long-term observations, it was natural to get involved in that.

Your question about policy is a difficult one. The World Meteorological Organization is supposed to be coordinating measurement projects, but they don't have the financial resources. The same idea that was the background of the AGAGE program is that you actually measure what's in the atmosphere and try to assess whether emissions reporting is accurate or inaccurate. Then, of course, we don't exist as an integrated human enterprise, we're divided by countries. So you have to figure out whether a particular country is doing what it reports it is doing. That's still in the future because there aren't the resources to monitor the planet in the way that is needed. The total cost of effective monitoring compared to the size of the impact on the global economy of greenhouses gas emissions is miniscule. I'm one of those people who believes that, by policy, you ought to have monitoring to figure out whether the policies are working or not. In many respects we already know that it isn't. And there's greenwashing, and people claiming, for example, that when you want to buy an air ticket, you should buy a tree to make up for the fuel emissions from your travel. It's not clear that any of that is actually working.

ZIERLER: All of your research is dependent on technology. What have been some of the most significant technological advances, either in instrumentation or in computation, that has made your research possible over the years?

WEISS: It gets complicated quickly. It turns out that this area of atmospheric climate research and ozone depletion research is very collaborative. I can understand how the models work, but I'm not a modeler, so it becomes important for me to work together with modelers, who tend to have an idea of how the instruments work but aren't instrument people. It is this collaboration that generates the net value in the research. Atmospheric research and climate research is extremely collaborative, and I think that's wonderful. Besides building long publication lists, you get to know people who do things that are different. That is one of the enriching things of being a scientist. If we all were the same, it would be less enriching.

ZIERLER: That's right. The fun stuff that you get to focus on these days, what are you currently working on and what's most interesting to you in the field?

WEISS: These are long-term observations that tend to be based on specific types of instrumentation. We've developed pre-concentrations technologies to basically do fractional distillation of the gases of interest that are in the air by collecting a large sample of air and then trying to get rid of the nitrogen and oxygen, and other gases that are rather large abundance compared to some of the ozone depleting substances. You distill them off at variable temperatures on traps and then inject them into a gas chromatograph/mass spectrometer, a GCMS. That's the fundamental technology that is being used now. In fact, we've had several companies interested in commercializing this.

There was a big incident in the early 2000s. After 2010, the production and sale of CFCs was totally banned by international agreement. Then, unexpectedly, we and our colleagues at NOAA who also monitor the atmosphere, saw that the global rate of decline of one of these gases, CFC‑11, had been reduced by a factor of two. In other words, it was still going down but only half as fast. If you know the lifetime, you can calculate how much new emission must have been associated with that, and the answer was 13,000 tons of this gas a year. It turned out that by having stations on Korean and Japanese islands, working with the modelers and the measurement folks, we were able to map the emissions of CFC-11 from eastern China, which accounted for about half of this increase. The Chinese have since fixed the problem, so it's a positive story. I think it was probably the entrepreneurial Chinese industries that were doing this. The Chinese are now building their own atmospheric monitoring network. The importance is for us all to work together, the Chinese scientists and the scientists around the world, to integrate these observations in a way that's meaningful, and share calibration standards and techniques, so that the interpretations are not skewed by a measurement or calibration issue.

ZIERLER: With all the rise in computational power, this of course leads to better modeling. I wonder if you can reflect in your field how better modeling leads to better science.

WEISS: It's critical here, of course. These inversion calculations model what you see if you sit at a particular point on the Earth. When the winds come from different directions where there are sources or no sources, the values of these compounds in the atmosphere fluctuate. If you make high-frequency automated measurements, you can use that information to basically back-calculate the distributions and sizes of the sources. . If you have a long enough time series, you can actually build a reliable model. That requires pretty sophisticated computations, maybe not the full level of supercomputer that we have today, but getting there. So it's that collaboration that's so powerful. It is based on modeling transport from weather systems and using the global observations of pressure and temperature; the basic foundations of understanding meteorology go into that. Mixing in the boundary layer and other physical processes are big parts of the problem.

ZIERLER: Ray, to give a sense of the overlapping academic communities that you are a part of, I wonder if you can give a sense of the most important journals to publish in, the most important conferences to present in, the most important scientist societies to be members of.

WEISS: There is the American Geophysical Union and the European Geophysical Union, and they both have a series of journals where we publish a great deal. There of course are the very prominent journals of Science and Nature. Some of this work has been published in those journals, but they tend to be summaries rather than in-depth research papers because there are length limitations. I think it's mostly the society journals and then Science and Nature. Probably more Nature than Science: Nature has played a fairly central role in this work.

ZIERLER: Ray, some administrative questions. Can you describe the relationship between UC San Diego and the Scripps Institution of Oceanography? Is Scripps purely within UC San Diego or is it independent to some degree?

WEISS: I don't know how many hours you have for me to answer that question!

ZIERLER: [laughs]

WEISS: [laughs] UC San Diego was created out of Scripps. It was created by Roger Revelle who was then the director of Scripps. Of course, UC San Diego is a major U.S. research university. If you think of UCSD as the child of Scripps, Scripps is now a component of its much larger offspring.

ZIERLER: [laughs]

WEISS: UCSD has become one of our nation's largest research universities. The budgets of its medical and engineering schools are enormous. Scripps is now a department of UC San Diego. It has been historically an unusual transition to go from being the father to being the child [laughs], or something like that.

ZIERLER: [laughs] Do you have a dual appointment within UC San Diego or your professorship within Scripps is a UC San Diego professorship?

WEISS: It's the latter. I'm a UC San Diego professor. I have these calling cards that have the emblem of Scripps in one corner and the emblem of UC San Diego in the other. [laughs]

ZIERLER: Let's go all the way back to the beginning. Of course, what brings us together is Caltech. How did you hear about Caltech? Where did you grow up and how did that get on your radar?

WEISS: I have a very strong Caltech connection. It begins with my father, who was an engineer. He finished his first three years of education in engineering at the ETH in Zürich at the beginning of World War II. My father and his family were lucky enough to get out of Europe, and he needed to finish his degree, so he finished his fourth year in engineering studies at Caltech.

ZIERLER: Do you know how he learned of Caltech, how he got there?

WEISS: This is a family rumor, but I think he knew that Caltech was a great place, because this was the time of the early international evolution of quantum physics and Caltech was part of that, of course. I'm not sure I know the answer to that, but I think he knew that it was a good place. I never knew what kind of an academic record he had at the ETH, but Caltech was impressed enough to admit him. And I think he liked the idea that he could focus on the engineering he wanted to do instead of being told to take courses in things he wasn't interested in. [laughs]

ZIERLER: He finished his degree at Caltech?

WEISS: Yes, and then he went on to be one of the pioneers of digital computing. He was interested in analog computing devices and then digital ones. He went to work for Northrup Aircraft, which was a very progressive place, and he and a bunch of his fellow engineers started a computer company. I think it would have been in 1948 when they had vacuum tube computers. It was in the southern Los Angeles area, across the road from the airport where Northrop Aircraft was located. I knew I was interested in science because of that sort of science and engineering heritage from my father. I went to high school here in La Jolla, to public high school. I applied to Caltech and MIT and Berkeley. I got into all three, but I thought I should go to Caltech because it was the hardest one to get into.

ZIERLER: Did you graduate at the top of your class?

WEISS: In my high school class? Probably, or close. But I was mediocre by Caltech standards. I was playing catch-up against these kids from Bronx High School of Science and Andover and Exeter and various other nice, fancy places! [laughs]

ZIERLER: What year did you arrive on campus? Was it 1960?

WEISS: 1960.

ZIERLER: Was the plan chemistry for you from the beginning?

WEISS: Yes, I wanted to be a chemist, and I finished as a chemist, but as I explained earlier, I diverted over to geochemistry.

ZIERLER: How did that happen? Was there a particular class that you took by chance and that captured you?

WEISS: I think it was mainly because I was attracted—one of the professors who did the introductory geology course was Clarence Allen. He was a great lecturer, and it inspired intrigue amongst those of us who weren't sure we wanted to do math, physics, or chemistry, because those were the limited choices as a freshman. I started exploring and I took various courses in geochemistry. I took a course from Harrison Brown. I took a course from Clair Patterson. I went to work for Sam Epstein doing stable isotope measurements, originally on plants. There's this whole area of research on how the isotopic composition of oxygen, hydrogen, and carbon change when air masses move across an area where there are plants, and whether you can use the plants to study those changes with elevation and distance from the ocean where everything came from. I worked on that with Sam Epstein and some of the people in his group, and that's how I got interested.

ZIERLER: On the social side, what house did you live in?

WEISS: I was in Ricketts.

ZIERLER: What was Ricketts known for? What was its character on campus?

WEISS: I'm not sure I know the answer to that question. We had these brake-drum riots, which some of the other interviewees of yours have mentioned. There's a mild kind of hazing of people coming into a student house. There was then, and I suppose there is today. I have no idea. [laughs] You can't get in and look around now—you need to have somebody let you open the door—but people used to wander around the place in those days.

ZIERLER: Did you stay on campus during the summers? Did you do research?

WEISS: In the last summer, I did. In earlier summers I went home and worked, I think. I had a job putting electronic stuff together in the company that my father worked for. You know how kids are. I think one summer I worked for a contractor digging trenches and stuff like that.

ZIERLER: As I mentioned earlier, I'm fascinated by this question about how the Seismo Lab missed the boat on plate tectonics, on seafloor spreading. I'm sure as an undergraduate you wouldn't have had view into this, but did you ever interact with Seismo Lab faculty? Did you understand Frank Press and his interest in getting involved in oceanography and how that was not working out at Caltech?

WEISS: I may have met Frank Press once or twice. His heritage was from MIT, if I remember correctly. Scripps is an observational place. Whether it's CO₂ in the atmosphere or magnetic lineations in the seafloor, Scripps is strongest in observations, in my view. Here at Scripps, there was Vic Vacquier, who was a geophysicist, who had developed flux gate magnetometers for the Navy during World War II in order to tow them behind ships. You can't do magnetic measurements from a metal ship very easily, so they would tow these magnetometers behind Navy ships and look for submarines and mines, I guess. That technology was adapted to study magnetic lineations in the seafloor. The Earth has magnetic field fluctuations—roughly every 100,000 years, the magnetic field reverses. These reverses are recorded in rocks that are formed at spreading centers on the seafloor. There's a place off of Iceland called the Reykjanes Ridge, and Vic Vacquier had towed a magnetometer across the Reykjanes Ridge and found these lineations that were symmetrical in both directions, showing that the seafloor was spreading. Those data, I don't think anyone at Scripps put together that this was the proof, but it turned out to be one of the proofs of sea floor spreading, and these lineations turned out to be all over the place, particularly in the Atlantic. Others put the different parts together. Vine and Matthews at Cambridge came up with the major synthesis of seafloor spreading, and of course it originated much earlier in the Wegener hypothesis because of the shapes of the coastlines. I think without the Vacquier observations Vine and Matthews might not have figured it out.

ZIERLER: By the time you were a senior and you were thinking about next steps, were you focused on graduate school at that point? Did you want to go into industry first?

WEISS: It was the time of the Vietnam War. Because of that, there were vulnerabilities to not continuing. In fact, the war actually played a role in whether I ended up doing what I wanted to do. In those days, if you even changed what you were doing and moved to a different school or a different department, it would count against your progression. You had to continue along a particular path to avoid the draft, so I just stayed on that path. I think it was only when I had a PhD and was more senior, and the Vietnam War had ended, that I began to question whether I had done what I wanted to do. Of course, the answer is that I didn't know, and I still don't know. In all such life decisions, you can't do the control experiment.

ZIERLER: Was geochemistry what you were focused on, thinking about grad programs?

WEISS: Yes, because I was interested in the isotope work I was doing with Sam Epstein at Caltech, and there were these stars of that field—they were all people who had gotten into isotope applications to the Earth through Harold Urey, who was at the University of Chicago then and eventually moved here to UCSD. Harold Urey, of course, discovered deuterium and won the Nobel Prize for it, but Harold was interested in using these things to study Earth processes, and his students did that. Among them were Gerry Wasserburg at Caltech and Harmon Craig here at Scripps. Harmon had a reputation for being difficult. You had your interview with Ken Farley who focused on some of that. My father was also difficult, and when people have asked me how I survived with Harmon, my answer was that I was used to it. My survival strategy was an effective one and I did fine. So, I continued working for Harmon. There were some other giants of geochemistry in those days. Among them was Wally Broecker at Columbia. Harmon and Wally were sort of the drivers of the creation of an oceanographic research program that I worked on as a graduate student. It had the great acronym of GEOSECS, that stood for Geochemical Ocean Section Studies.

ZIERLER: [laughs]

WEISS: With my interest in using chemical tracers to study the ocean, that was obviously what I did. I worked on measuring gas solubilities. Those are still my most highly cited papers, with the equations for calculating oxygen and CO₂ solubilities in the ocean. Those are used all the time. So, I did that, and I began to do a few things on my own. Eventually, when I finished, I stayed working on these projects here at Scripps in a postdoctoral, and then a research, position for a number of years. Then, eventually, I was offered a faculty position at MIT at the full professor level. Scripps apparently decided I was worth keeping and made me a similar offer. I stayed, in large part for personal reasons. As I said earlier, my family was here. My father had died and my mother was still here. I thought it was important to be near her. And Scripps was good place to be a professor, so that's what I did. The irony is that my closest collaborations are now with people at MIT!

ZIERLER: [laughs] To go back to your work as a graduate student, what were the main research questions at that point, and how did they influence how you put your dissertation together?

WEISS: I think the main questions were, how rapidly did the deep ocean circulate, which is of course critical for so many questions, whether it's the flux of things out of the Earth at the spreading centers—of course, seafloor spreading was new. We knew in those days, and in fact Ken Farley has done a lot of work in that area, that helium isotopes coming out of the Earth interior were quite different from the ones in the atmosphere, and you could trace them—you could use them to study ocean circulation, because anything you can measure that changes in the ocean becomes a time-dependent tracer. I think it's the broad question of the nature of deep-ocean circulation and its velocity, its time. It's hard to assign an age because there's mixing, but the average age of deep water in the north Pacific Ocean is thousands of years, or one or more thousands, and a few hundreds of years in the Atlantic. Those things weren't particularly well known when I got into this, and I think they're pretty well known now.

ZIERLER: Given the inaccessibility of the deep ocean, how do you study it? How do you get there?

WEISS: You went to sea on a ship, in those days. Nowadays, people do things with automated floats. Ships are very expensive to run, but the way you did this in these various expeditions was that you spent a month at a time or more on a ship. In the middle of the ocean, you would put down instruments on wires, and also collect water samples that were either saved for subsequent analysis in a lab on shore or measured on the ship.

ZIERLER: You spent a lot of time at sea as a graduate student?

WEISS: I did, probably more than a year and a half or two years of my life, I think. They were a month at a time when you went to sea, except in the Antarctic where it was more like two or three months at a time.

ZIERLER: Did you enjoy it? Was it fun to be out at sea?

WEISS: It's one of those things that you're apprehensive about when you're about to do it, but glad you did it when you get back. [laughs] Also it gave me an opportunity to see a lot of the world that I wouldn't have had otherwise.

ZIERLER: What was your funding as a graduate student?

WEISS: I think I had a fellowship for a while from the Department of Energy, but it was generally the National Science Foundation.

ZIERLER: Obviously we have Ken's perspective. What was it like to work with Harmon and how did you navigate that?

WEISS: I tried to avoid confrontation. [laughs] I found, later on really, that with a lot of people are strongly opinionated, Harmon was not the only one, you find that if you push back with logic, that that actually works.

ZIERLER: Because it's about the science. We're not talking about interpersonal conflict.

WEISS: Exactly. You have to depersonalize the whole thing. I think it's a mistake to personalize all this stuff because it's not about that.

ZIERLER: What were the conclusions of your research and how did that contribute more generally to these broad questions about the impact, the nature, of deep ocean currents?

WEISS: I would say that I didn't really hit my stride until I became one of the leaders of the development of using the CFCs to study the ocean, and then there were a lot of really interesting discoveries—western boundary currents flowing down the Atlantic and bifurcating at the Equator, which had been predicted by the modelers but nobody had ever seen, things of that sort.

ZIERLER: After you defended, did you stay on as a postdoc? Were you hired as a staff scientist?

WEISS: I didn't do the CFCs as a graduate student. I don't think the impact of my graduate student research was that large, except perhaps in quantifying solubilities and writing equations that would represent their dependences on temperature and salinity. That has lived on. My other activities included the early phases of measuring the carbonate system in the ocean and other ocean chemistry parameters that are more fully understood today.

ZIERLER: Staying on as a postdoc, was that simply an opportunity to continue on with this research or did you take on new projects?

WEISS: A little bit of both, I would say. Moving into the CFCs began to happen when the Nobel Prize was given for stratospheric ozone depletion chemistry to three people. One of them was Paul Crutzen, who was working mainly in Germany but also was here at Scripps for a while. In fact, Paul and I taught a class together. He had raised the question of nitrous oxide, because it's the so-called odd nitrogen that destroys the stratospheric ozone. That's a natural modulator of the ozone layer. There was some controversy when people explained that we would have to give up hairsprays and refrigerants and things of that sort because of the CFCs. Little was known about the lifetime and cycling of nitrous oxide in the atmosphere and there were some people who said, "Well, if you're worried about CFCs, you should really be worried about fertilizers, because nitrogen fertilizers, if they produce a lot of nitrous oxide you would have to trade off between growing food and protecting the ozone layer."

One of my colleagues, Mike McElroy at Harvard, was deeply concerned about this. Working with Harmon, and Sherry Rowland, who was one of the Nobel Prize winners at UC Irvine—and also from the University of Chicago, by the way—got me interested in whether I could actually measure nitrous oxide in the atmosphere well enough to figure out what was going on. I succeeded in that. [laughs] So, I can claim that I discovered the actual abundance of atmospheric nitrous oxide, and its rate of change and difference between the hemispheres. That allowed people to begin to figure out how important this postulate was. It turned out to be not as important as feared, I think mainly because the amount of nitrous oxide produced from agricultural fields was less than postulated—but it's still important, and it's still going up in the global atmosphere like crazy even though it is supposed to be limited under the Paris Agreement.

ZIERLER: Nitrous oxide is a greenhouse gas?

WEISS: It's a greenhouse gas, and it's also an ozone depleter.

ZIERLER: To clarify the timing, you got involved in the CFC research first as a postdoc?

WEISS: I think I was a researcher at that point.

ZIERLER: How did it get to you? What were the issues that got you involved?

WEISS: I wanted to use them as ocean tracers, and people were talking about doing it but they weren't doing it very well. I thought I could do it better, and I jumped in.

ZIERLER: What does that mean, to use a CFC as an ocean tracer?

WEISS: It means being able to measure the CFCs in the water with sufficient accuracy, sensitivity, and precision, really, to be able to see changes in the ocean. Our detection limit was quite small. We would collect water samples and make the measurements on the ship with a gas chromatograph using the electron capture detector which was a tremendous advance in our ability to measure things in nature.

ZIERLER: From the ocean research, how does this then get you to atmospheric nitrous oxide?

WEISS: I think it's just having the measurement capability and hearing about the problem. Maybe the linkage between nitrous oxide and the CFCs is both being ozone depleters.

ZIERLER: People are starting to raise alarm bells about atmospheric nitrous oxide, you realize that you have a measurement capability, and that's what compels you to get involved?

WEISS: Yes. Also, of course, you need to get away from local sources to get an idea of what the planet is doing. You can either do that by going to the top of a mountain or you can go in the middle of the ocean, assuming that the ocean is not a big source of nitrous oxide. It's a moderate source, but it's not a big one. I had the capability to measure the nitrous oxide dissolved in the ocean and in the atmosphere from research ships while I was doing other things.

ZIERLER: How far back did these concerns about nitrous oxide go in the atmosphere? How well developed was the field at the point that you got involved?

WEISS: I think it was just beginning. The emphasis on it as an environmentally important gas came from the reactions for destroying ozone that were worked out by Paul Crutzen.

ZIERLER: Did this start out as a theory, or these were observations?

WEISS: I think it basically started out as a theory. Also true of the CFCs.

ZIERLER: You have this oceanographic capability; how do you then apply it for atmospheric studies?

WEISS: I had the capability to measure things in the atmosphere already, so the idea was applying it to nitrous oxide in the atmosphere. One of the things I was doing was a little bit related to the work that Charles David Keeling did. I put instruments on ships that would measure the partial pressures of CO₂, methane, and nitrous oxide in the surface waters of the ocean and in the atmosphere at the same time by alternating the instruments between measuring the air and measuring the water. The water was measured using something called an equilibrator, where you could basically sprinkle the water into this chamber and measure the gas abundance in the gas phase in the chamber that you have to show is in equilibrium with the water that is flowing through the chamber. We built these instruments and put them on ships as add‑ons for expeditions that were already funded to go all over the oceans.

ZIERLER: If I have the history correct, the concerns that led to the Montreal Protocol, that happened pretty quickly? Scientists were beginning to understand there was a major problem that needed to be solved quickly? Is that how it felt to you?

WEISS: Yes, but it also had an instrumental origin. Jim Lovelock, of whom you've probably heard, became a rock star, basically [laughs]. He just died at 103 a couple years ago. Jim had invented the electron capture detector. That made it possible to actually detect these CFCs in the atmosphere. There was an expedition, I can't remember whether it was a British ship or an American ship, but it went down the Atlantic Ocean together with some scientists from the Naval Research Lab in D.C. They took one of Jim Lovelock's detectors on this ship and they showed that they could measure CFCs. With the gas chromatograph and the electron capture detector, they could measure in the atmosphere CFCs ubiquitously all over the planet. That got people thinking, well, what is happening to this stuff?

ZIERLER: Was it obvious that ozone depletion was human caused from the beginning, or there was a hunt for the cause?

WEISS: I don't think people thought it was that obvious when it was postulated, until the ozone hole evolved. The chemistry of the ozone hole is somewhat different from the chemistry around the whole planet's stratospheric ozone layer because it involves interactions with ice particles in stratospheric clouds and reactions on those surfaces when the Sun comes up in the polar spring. But that got people's attention. The postulate was there, and it really referred to the gas phase reactions in the stratosphere, but then the ozone hole was found, and it was clearly driven by the same kinds of compounds but in a different kind of chemical reaction.

ZIERLER: Was it the CFC measurement work that attracted MIT to you?

WEISS: I think I was generally known for doing a lot of different kinds of experimental work. I had also done a lot of work on deep lakes, which we haven't talked about, using the same kinds of tracers to study deep metabolic processes by getting the overturn rate. I was an up-and-coming mid-career guy, I had colleagues at MIT who knew about my work, and I think that was the reason that I got an offer from them.

ZIERLER: Obviously Scripps countered, and that was an easy decision for you?

WEISS: It wasn't that easy. MIT is a great institution, as is Caltech.

ZIERLER: Let's talk about the deep lake research now. How far back does that go? Did you do any work as a graduate student in deep lakes?

WEISS: No, I did not. But as a graduate student, because of my ability to develop sampling technologies, I did go to the Red Sea. I've also done work on thermal springs in the seafloor in the Galapagos spreading zone and various other places. And I've been on dives in the Alvin submersible as well, to collect samples of these gases and figure out what's coming out of seafloor spreading centers by hydrothermal emissions sampling. My early work in this area was as a Scripps graduate student on a Woods Hole ship in the Red Sea, because that's one of the first places where people realized that there were emissions into the deep ocean at spreading centers.

ZIERLER: The term "deep lake," how deep makes a lake deep? Is there a threshold? Does it have to be saltwater? Can it be freshwater?

WEISS: Freshwater is more interesting in some ways. I've also worked in deep partly saline lakes. The deepest lake in the world is Lake Baikal. During the Cold War, the U.S. and the Soviets didn't do a lot together, but there was a treaty on climate change, and under that umbrella, American and Soviet scientists would meet. I had the opportunity to go to a meeting in what was then Leningrad, where I sat at a shiny table in this room that probably once belonged to a Russian nobleman and was then a government meeting place. I had an American flag in front of me and the guy across the table had a Soviet flag in front of him. We looked for things we could do together. I don't think the Soviets spent a lot of money on Earth sciences, but they, of course, had a big chunk of the world. I suggested to my Soviet colleagues that we might study Lake Baikal using oceanographic techniques. That turned out to be very interesting, and we worked with a lot of people from other countries, including from Switzerland, where they have a lot of lake science.

Freshwater behaves differently because it has a temperature of maximum density at four degrees Celsius. The temperature of maximum density in seawater, because of the added salt, is below the freezing point. So, the physics of circulation in lakes works differently because when the surface water gets colder than the deep water, if it's below four degrees, it doesn't sink anymore; it goes to a different depth. People wanted to understand how that worked, and so the CFCs would be a great way to figure out the mixing rate in the lake. Besides, that lake had a great history. Mendeleev, who invented the periodic table, he was interested in Lake Baikal, so it was a great opportunity to go there.

ZIERLER: What did you learn about Lake Baikal from that research?

WEISS: We learned something about the overturn rate that drives the cycling of nutrients. It's a mile deep. We ran two expeditions in the lake, and we got to know Soviet scientists, which was also very interesting.

ZIERLER: What were some other major lakes that you have worked in?

WEISS: When I was a postdoc with Harmon, we worked in Lake Tanganyika. That's the second deepest lake in the world. Then one of my students did his thesis working in Lake Malawi using these tracers and developing new tracer technologies including sulfur hexafluoride. All these anthropogenic gases that are quite long-lived in the atmosphere are basically conservative when dissolved in water, so you can use them as time-dependent tracers. Then we went to Issyk-Kul which is in Kyrgyzstan. Those are the deep lakes I've worked on. Oh, and in the U.S. I worked a little bit on Lake Tahoe, and a little bit on Crater Lake.

ZIERLER: Is there a complete story that you can put together from having this dual perspective of oceans and lakes, or is it essentially two separate stories?

WEISS: It's almost separate stories except for the nature of collaborations in different disciplines, which I also find interesting. As I said earlier, the atmospheric folks are more collaborative. If you're a measurement guy—and as I also said earlier, Scripps is famous for measuring things more than for leading-edge modeling—so when I was doing all these tracer measurements in the ocean, they would be used by modelers, but I wouldn't usually get my name on the papers. In research on lakes and the atmosphere it tends to be more collaborative, and the modelers and the measurers work together, and we could decide that this graduate student or that graduate student would be the first author on this new measurement or interpretation.

ZIERLER: Some words that come up over and over in your publications are vents and ventilation. What does it mean in this oceanographic context?

WEISS: Seafloor vents refer to the hydrothermal vents on the seafloor where ocean water circulates through cooling rocks and emits a broad range of things into the deep ocean, including nutrients that drive a food chain that is separate from the surface where all these tubeworms and things live. That's what we mean by vents. Ventilation has to do mainly with the exchange of dissolved gases with the atmosphere. It's surface processes that drive ventilation. Right now we have to worry about things like how quickly the oceans are going to take up the excess CO₂ that we're putting in the atmosphere, and that's a ventilation problem.

ZIERLER: If I heard you correctly, is that to say that there's seawater under the seafloor, that it seeps below, it's in these vents themselves?

WEISS: Yes, it circulates into the newly cooling crust and comes out at these hydrothermal vents. Because it's under very high pressure, it doesn't boil. The water can be 300 degrees Celsius and still be liquid water.

ZIERLER: How far down can you get? Your experiences in submersibles, how far down can you get to the ocean floor to study these phenomena?

WEISS: It depends on the ratings of the submersible. The Alvin, which is the most famous research submersible, from Woods Hole, now has a limit of six and a half kilometers. The hydrothermal vents tend to be less deep because they're at the top of spreading ridges, so maybe two or three kilometers, something in that range.

ZIERLER: What is the deepest you've ever gone?

WEISS: I've been to almost five kilometers. I also worked on manganese nodule studies for a while.

ZIERLER: What is that?

WEISS: Manganese nodules are these nodules that grow very slowly on the seafloor, and they're rich in heavy metals including manganese, nickel and iron. People are now talking about mining them, because of the need of all these metals for things like making batteries for electric vehicles and solar energy storage. There was a project that I worked on for a while that studied the chemistry of how nodules form, and we put a lander on the seafloor, sort of copying what people were doing when they sent things to the Moon and planets. We would put instruments on the seafloor with chambers on them and collect water samples from those chambers. That is again the kind of instrumentation that I was pretty good at and loved to do, so I became involved in that for a while, but I didn't stay there.

ZIERLER: What is it like when you go down five kilometers? How do you prepare for it? What are the sensations when you're there?

WEISS: The sphere in Alvin has a six-foot internal diameter. It's cold, because of course the water outside is two or three degrees Celsius. You can't drink too many fluids because you can't easily pee [laughs]— it takes basically a whole day. It takes two or three hours to go down, and two or three hours to come back up, and you get two or three hours on the bottom, with a pilot and two scientists each looking out a tiny porthole. It's a fascinating experience to do it. In the end, if you're for example collecting samples from a hydrothermal vent, it's much easier to look at the TV screen inside that uses the camera outside, to see what's going on, than to try to see it through the little window, because it's a window that is I think four inches in diameter inside, so you can't see very much.

ZIERLER: Do you feel the pressure differential? Do your ears pop?

WEISS: No, no, it just gets cold. You don't feel the pressure differential at all. Of course, it's dependent on the CO₂ that we exhale being absorbed. That's also the way it works in military submarines. They have to circulate the air through, I think it's lithium hydroxide, that takes up the CO₂.

ZIERLER: To go back to the policy discussions, when did you get involved in the Montreal Protocol itself?

WEISS: Like so many things like that, there was political controversy associated with it. I was a fairly young guy, but because I was making measurements in that area, I got to know some of the pioneers, including Jim Lovelock, Sherry Rowland, Mario Molina, and Paul Crutzen. I went to meetings they went to, and they would come talk to me about my measurements. It was a rarified atmosphere. But then being a Caltech undergrad had also been a rarified atmosphere!

ZIERLER: That's right, that's right! The Montreal Protocol—we've already established this contrast—a huge success. Then we look at COP28, the IPCC process, and there's a lot, to state the obvious, to be desired. What made the Montreal Protocol so successful, and how could it be or at least how should it be a model, for climate change negotiations?

WEISS: First, it's an easier problem. Second, the chemical engineers came up with alternatives that worked just fine, so that you could afford to give up the things that you were doing with the CFCs. The other thing that made it a success, it seems like a small distinction, but if you're worried about gases that are produced both naturally and anthropogenically like carbon dioxide, that's a much harder problem to solve, because the carbon dioxide flux that comes from us burning fossil fuels is order one percent of the natural flux that goes in and out of the atmosphere all the time—in and out of plants, in and out of the oceans. Even though the rise in CO₂ in the atmosphere is clearly due to the burning of fossil fuels—and to some extent deforestation. But the main signal is fossil fuels. You can show that by measuring the radiocarbon in the atmospheric CO₂—fossil fuels are so old that they have no radiocarbon in them, so you can really prove the role of burning fossil fuels in atmospheric CO₂. But then you're trying to regulate something that's one percent of the natural flux. It's hard to get your head around that, to say, "Well, if it's only one percent of the natural flux, why is it going up?" That's a little bit of a complicated problem already.

For the Montreal Protocol gases, you're simply regulating production and sales, and you make assumptions then about what emissions would be, based on reported production and sales. It's regulating in a different phase of the process. In fact, we now have the HFCs, hydrofluorocarbons, which have been moved from what was then the Kyoto Agreement to the Kigali Amendment under the Montreal Protocol. They're not ozone depleters at all, but it's enormously successful because you can actually measure and quantify in a top-down way whether the production and sales are being limited, and they are. Those success stories are partly because it's easier to study something that's entirely manmade than it is to study something where man's impact is on a very complicated natural system.

ZIERLER: A connecting point is that the Montreal Protocol, even as relatively easy as it was, it still needed political will and international cooperation to happen.

WEISS: Right, I think that's true, and I think the key again lies with the chemical engineers. [laughs] Because big companies like DuPont, they were originally opposed, and then they came around rather early. In fact, they had the trade name of freons, and they wanted to make sure that people didn't refer to these things as freons because that implicated DuPont, and DuPont was among the leading companies to phase CFCs out. It was also wise, of course, for them to make and sell other things that would do the same job.

ZIERLER: Just as a thought experiment to convey the impact of this work, absent the Montreal Protocol, absent any concerted effort to come up with replacements for CFCs, what would the world look like now? How scary would it be?

WEISS: There are analyses that people write in Montreal Protocol assessments called "the world avoided." I think as far as those go, they are projecting what the emissions would have been from economic models. There would have been a serious impact on the global ozone abundance, not just on the ozone hole. But I don't know if I am qualified to answer that question. It's a modeling and prediction question.

ZIERLER: When it's everywhere, is that to say that it's most prominent at the hole but that there is depletion everywhere in the atmosphere?

WEISS: Yes, stratospheric ozone depletion is a global phenomenon. The polar ozone holes is a separate problem that results from having these same ozone depleting compounds attached to polar stratospheric ice particles when the Sun comes up in the Antarctic or Arctic spring. That's when the ozone hole is generated by surface reactions.

ZIERLER: I don't know where it comes up in the chronology, so I'll just ask now—the Weddell Sea. How did you get involved in studying the Weddell Sea and why is it so important?

WEISS: It's the major source of Antarctic bottom water, sinking cold water. I've been on a couple of expeditions to the southern Weddell Sea in order to study the processes there.

ZIERLER: What processes does the Weddell Sea drive globally?

WEISS: The cold water that fills the world oceans comes either from the north or the south. The Pacific doesn't go very far north, so the northern water that enters the global circulation system comes from the Arctic Ocean through the Atlantic, east of Greenland and around both sides of Iceland and down into the deep Atlantic. That water, much of it eventually goes into the Southern Ocean, all the way down the Atlantic Ocean, where there's even denser water that's formed around Antarctica, most of it in the Weddell Sea but also in other areas. That high-density water involves heat exchange, with the bottoms of the floating ice shelves, which is out of exchange with the atmosphere. Then there are so-called intermediate water masses, which again mostly come from the Southern Ocean and to some extent from the north. So, it's a very complicated circulating system, and there's mixing all the way along.

The purpose of going to the southern Weddell Sea was to try to figure out, for example, the role of ice shelf melting in the isotopic composition of the coldest, densest water that is formed in the Antarctic. It turns out there is a role for ice shelf melting, and it goes along with the heat exchange for cooling the water. That's an area that people still work on today. It was interesting to do some of the first geochemical sampling of those waters. That was also done by putting water samplers into the ocean from a ship, from an icebreaker, to collect the samples.

ZIERLER: I can imagine there were two possible avenues of research that got you more involved in climate change, both the atmospheric CFC work but also the ocean current work. Was it both of them that compelled you into climate change research, one or the other, or something entirely different?

WEISS: I think both.

ZIERLER: Do you have a clear memory of when climate change began to be an issue of concern? Of course, there's Roger Revelle going all the way back to the 1950s. There's James Hansen and his famous testimony in the 1980s. When does it become real for you?

WEISS: Oh, I think it became real when I was a beginning graduate student. One of the first jobs I had was on a summer research cruise from San Diego to Easter Island and Chile. Charles David Keeling asked me to collect air samples for him on that expedition, and I did. He was always saying something that I think is germane today, namely that it's going to be really hard to understand the global carbon cycle, but to save the climate we should just stop using fossil fuels. He was saying that in the 1960s.

ZIERLER: That's to say that the greenhouse effect was already established science that early?

WEISS: Oh, the greenhouse effect dates—I'm not sure who was first—from the late nineteenth century.

ZIERLER: I think Sweden in the late nineteenth century?

WEISS: Yes, Svante Arrhenius, one of the first Nobel Prize winners in chemistry, logically asked, knowing that CO₂ absorbs infrared radiation, whether the climate would change as a result of the Industrial Revolution. It was in the late 1800s that he asked that question, and I think there were people even before that who postulated that it would be a problem.

ZIERLER: The theory, the postulations, have a long history; when is the experimental evidence really solid? Is that already there when you're a grad student?

WEISS: It depends on what you think is solid evidence. If you want to actually measure the change in the Earth's temperature, that's a very complicated problem. I once heard climate deniers being addressed by Ron Oxburgh, Lord Oxburgh—he was one of the leaders in the politics of climate change for the U.K.—I remember hearing him talking to these deniers at a meeting saying, "Well, there are only three things that you need to know, and which one of them do you question? Do you question that CO₂ is going up in the atmosphere?" And the answer is that nobody really questions that. It's really measured, thanks to Dave Keeling and many others. "Do you question that CO₂ absorbs infrared light?" Well, I don't think they question that either. So then the third question is, "Do you question that the rise is due largely to burning fossil fuels?" As I noted earlier, there's a proof for that by measuring the radiocarbon in the CO₂ in the atmosphere, because you're adding CO₂ without radiocarbon and you're diluting the radiocarbon that is generated by cosmic rays in the atmosphere, so over time the radiocarbon in the CO₂ in the atmosphere has been diluted by burning fossil fuels. In a way all you need are those three things! Why shouldn't the climate change? How that changes, that's the hard problem.

ZIERLER: Were you taken aback by the denialism early on? Were you surprised that the public, the industry, would pose such a protest against the science?

WEISS: I think I was a little bit taken aback, but it's hard to underestimate the role that people's beliefs play in what they think. It begins with a question of whether there's a God or not. People believe things and they interpret their own way. It's the old expression, "You're entitled to your own opinion but not your own facts." I don't know. People ask me often whether I'm discouraged because I work in this area. I don't spend a lot of time thinking about it—because I think then I would be discouraged!

ZIERLER: As you were explaining before, phasing out CFCs, the Montreal Protocol, that was a much more straightforward problem because it was a chemical that had a replacement. Maybe part of the answer with the denialism is just how completely dependent modern civilization is on fossil fuels.

WEISS: Of course, yes.

ZIERLER: And how there is, certainly not 30 or 40 years ago, and really even today, no viable alternative if we want to continue our standard of living.

WEISS: Yes, yes, and it all gets obfuscated these days because there are other legitimate issues like social justice. Here in California, we have a problem, because a lot of people, including me and maybe you, have solar cells, and we have batteries as well—we can afford them—but somebody who is not as well-off can't afford them. The question is, who is going to pay for the grid? You need the grid when the Sun isn't shining. With our solar cells we can manage basically off-grid all summer, but in the winter it gets a little dicey. I have noticed like a factor-of-three change in the generation of electricity during a cloudy, winter day versus a sunny, summer day. The people who cannot afford rooftop solar are paying for the grid because they're paying by the amount of electricity they use, and people who have solar cells and batteries don't use very much. Now they want to change the charging structure here in California, which makes investing in the solar cells less financially attractive, so the only reason to do it is if you really care about the climate more than if you really care about saving the cost of energy. A lot of people are motivated more by money than they are by really buying into the whole concern about climate change. Here you have a conflict of legitimate social requirement and having that conflict delay the progress toward getting off of fossil fuels. Those are not easy problems.

ZIERLER: As you got more involved in the scientific community broadly conceived that was focused on climate change, what about the scientists themselves who questioned what they called the dogma? How did the broader community react to this? Obviously there's always room for skepticism, but those like Will Happer or Steve Koonin who were really out in front of these issues, how were they regarded generally by the mainstream?

WEISS: I don't know how to answer that question. One of my friends and colleagues is Naomi Oreskes, who wrote on this—Merchants of Doubt is the title of her best-known book. She has also done other work. She is now at Harvard. She works in that area. It has surprised me that I have known some very sharp scientists who are deniers, and I'm still having trouble wrapping my brain around it. I think there's a tendency for very smart people to think they can figure anything out, because they never get cut down to size, [laughs] as they say.

ZIERLER: Have you ever engaged directly, scientist to scientist?

WEISS: With someone who was a denier? Not often. If I knew they were a denier, I usually wouldn't bring it up! [laughs]

ZIERLER: [laughs] The idea of very smart people, has that ever caused you to think maybe we're missing something here, or do you see the scientific evidence as so overwhelming that it's not even worth paying that much mind?

WEISS: That's a really good question, because I actually have a friend from my class at Caltech who turns out to be a denier. I won't mention his name because I think it's too controversial, but he's extremely highly regarded. He has to be a "he" because when I went to Caltech there were no "she's."

ZIERLER: Fair enough!

WEISS: I think part of what you said may be part of this—that if you're good at navigating the complexities of a problem, you might find surprises. I think it's that kind of thinking that has been reinforced by the success of these really smart folks that encourages them to not quite accept. There must be some part missing. There must be some effect of water vapor or something that's driving this that's got nothing to do with fossil fuels. But it would have to be an offsetting argument, to return to the thing that I mentioned before. If you believe that it's going up, and it's fossil fuel produced, and it absorbs infrared light, why should the climate not change? I think that's the great question.

ZIERLER: There's also the complicating factor that obviously climate change is extraordinarily complex, there are so many moving parts, and scientists have to be careful about not asserting that they know everything, and that their observations or their hypotheses are subject to change as new data come in. That itself is very conducive to sowing that doubt from these merchants that Naomi writes of.

WEISS: That's correct. I suppose we should just discount people who have a financial interest. Whenever I get a grant from someplace, I have to fill out these enormous forms that neither I nor my wife gets any money from this or that organization, et cetera, et cetera.

ZIERLER: You've been at this for a long enough period of time. In your own experiences, have you changed your views? Not in terms of the overall paradigm of what is causing climate change, but more refining them based on what the data, what the observations are telling you?

WEISS: I suppose so. There's the terrestrial biosphere, and I haven't done a lot of work in that area but it's obviously important. Going back to selling you a tree, the trouble is that tree may have been sold to 10 other people already. Then there are surprising findings. I go to a lot of these conferences that the World Meteorological Organization puts on together with people who study the terrestrial biosphere, and there have been some surprising findings about the regrowing of things in the Amazon as a result in the changing of the moisture in the atmosphere there and wind patterns changing. Yes, it's complicated, and some things may work in an opposite direction than people first assumed. Even in ocean modeling, the computers are not big enough to resolve all the small eddies in the ocean, so they put some assumptions in there about the viscosity of the ocean. They basically represent the eddies by changing the viscosity. Those are all assumptions that we hope will work, but I suppose there could be surprises. It's not my area! [laughs]

ZIERLER: A question on the teaching and mentorship side, as you got more involved in climate science, did that change the kinds of students—the grad students, the postdocs—that wanted to work with you? Generally, have students become more environmentally focused, or they're interested in applications at least as much if not more than the fundamental science?

WEISS: I think that's true, just observing students in my field, not just my students. I'm about to be 81 years old next month, so I'm not taking any students unless it's a perfect overlap. I don't have any now. It's hard for me to calibrate with direct experience, but I think that social awareness has increased a great deal.

ZIERLER: This affects not only the kinds of things that students want to study but the kinds of jobs they want to go into?

WEISS: I suppose. Everybody wants to make a difference if they care about these enormous crises.

ZIERLER: Back on campus, when did you start taking on administrative leadership responsibilities?

WEISS: I would say 1990 or thereabouts. I was already in my fifties.

ZIERLER: This is when you became the associate dean of Academic Affairs?

WEISS: Yes, and before that I was the director of one of the research sections here, the research divisions. That might have been in the middle 1980s.

ZIERLER: What were your responsibilities as associate dean?

WEISS: As associate dean, I was supposed to assure integrity in the review and appointment process. You asked earlier about the relationship between Scripps and UCSD. The Scripps directors have historically had three crowns: the director of SIO, the vice chancellor for marine sciences, and the dean of marine sciences. In order to maintain the relationship with the main campus in the best position for Scripps, one of the former Scripps directors created this associate dean position to basically take the dean responsibility of reviewing all the files and writing on them away from the director so the director could still have the final call on things. Because there's also this tradition in academia, that in review or appointment processes, you only get one shot. So, it isn't correct for someone to write the letter and have it go through all the committees on the main UCSD campus and then come back for final approval; that's two shots. One of the former directors of Scripps, Ed Frieman, realized that, and he created the position. I think I was the third person to hold it.

ZIERLER: How long were you in that role?

WEISS: Thirteen years.

ZIERLER: Going back to the joke about how many hours do you have, did you see the relationship between Scripps and UC San Diego change? Did you witness those changes over those 13 years?

WEISS: Oh, absolutely.

ZIERLER: In what ways?

WEISS: Scripps has become a smaller fraction of the total UC San Diego enterprise.

ZIERLER: That's not because it's shrinking; it's because the school is growing?

WEISS: I think that's right.

ZIERLER: Does that mean it has influence? Does that register at all for Scripps? Does it matter one way or the other?

WEISS: I'm not sure. But I think it must [laughs]. .

ZIERLER: When did you start thinking about going emeritus?

WEISS: When I was still the associate dean. I kept doing it for three years after I went emeritus because I realized two things. First of all, there were financial issues in the UC system. The UC system is widely described as the greatest public university in the country if not the world. I just watched the Oppenheimer movie and saw all the material about Berkeley. But the emphasis from the legislature has been increasingly on undergraduate teaching and on not teaching people who are not Californians, and the university was running out of money. In my position as associate dean, I knew how much we were running out of money. At the same time, as I mentioned earlier, the UC retirement system was very generous. In order to compete with Caltech and all the other great privates—Stanford, Harvard, MIT, et cetera—we couldn't offer the same salaries, but we could offer very generous benefits, and we did. That was unsustainable. I realized at some point that retirement and returning to active duty was a financially viable alternative, so that's what I did. It gave the institution money, retained a comfortable income, and it gave my FTE back so Scripps could give it to a younger person.

ZIERLER: A win all around, it sounds like.

WEISS: It was a win-win-win, and I didn't have to do things I didn't want to do. Except I thought it was important so I kept being the associate dean for three years. Then eventually they got someone else to do it. [laughs]

ZIERLER: Now it's the good life. [laughs]

WEISS: It's not entirely the good life, because there are certain rules in the UC system that keep me from being actively engaged in some of the processes I learned so much about over those 13 years. Retired people are not supposed to be involved in recruitment and hiring of people, so I am excluded from sharing much of what I learned.

ZIERLER: You still maintain an office? You go in when you like?

WEISS: Yes, I'm there right now, if I get rid of the picture behind me in this video! [laughs]

ZIERLER: [laughs] For the last part of our talk, I'd like to ask a few retrospective questions about your career, and then we'll end looking to the future. First, Caltech, it's what brings us together—what has stayed with you from your undergraduate days at Caltech? What helps you understand the world as a scientist that you got as an undergraduate?

WEISS: My full appreciation for how much Caltech has helped me to become a real science citizen came later. When I was there I was just trying to keep up. But the active research environment that I was thrown in the middle of—and I just mentioned seeing the Oppenheimer movie—well, we had Richard Feynman coming to our student house and telling us stories, and classes from Linus Pauling. That's an exposure to greatness! And of course not just those people, but a whole list of people. Clair Patterson. Harrison Brown. Those are people who changed the world. Gerry Wasserburg. They are people who changed the world by the way they thought about things, and by their independent means of thinking. Just being exposed to that, and to an active research environment, gave me a real heads-up. I have had graduate students who came from absolutely first-rate colleges where there was not an active research environment, and for them it was a little bit of a shock. They would either adapt or they would leave and go to law school or something. It was a different background that they experienced. So, I fully appreciate that Caltech gave me a great start on my academic research world.

ZIERLER: This is a retrospective appreciation. You're saying this now looking back.

WEISS: Yes, that's right. I didn't realize at the time that I was in this rarified place. I guess that's the way to put it.

ZIERLER: Of all of the research that you've been involved in, what has been most satisfying, in terms of an irrefutable point of evidence that you discovered or something that was really vital to policy outcomes?

WEISS: I think the greatest impact is running a program that has played an active role in making the Montreal Protocol work. That's a pretty big deal. The Chinese have spent a fortune now setting up their own network, and it's all based on work that wouldn't have happened without the contributions of me and my colleagues. Again, it's collaborative.

ZIERLER: Do you see that as a closed chapter? Is there still upkeep work to make sure—?

WEISS: Oh, it's anything but a closed chapter! In fact, what we really need to do is to persuade the policy folks that they shouldn't believe what people report about what they're doing. The Chinese story I don't think has any bad faith in it. I don't want to drag this out, but there's an irony in that story according to The New York Times. Again, it's not my job to do the causal stuff—it's to find out what's going on and let the policy people decide what to do about it—but involvement with the press has been important in my life. I went to the COP in Copenhagen and ended up talking to people from The Economist and trying to make this same point, that if you don't measure what's actually going into the atmosphere, then you have trouble believing all these treaties that are supposed to be regulating it. One of the ways to put it, which has been repeated in a lot of places, is that without measurements it's like going on a diet without ever weighing yourself. That weighing needs to be done.

What happened with the Chinese was that they seemed—according again to the press and to some other activist institutions—that they ordered better insulation in new buildings in China, because they wanted to reduce the fossil fuel consumption. I don't know the reasons for that. It's probably partly the climate and partly people's health, because a lot of dirty coal was burned to generate electricity in China and that gave people respiratory infections and things of that sort. So for one reason or another, the Chinese ordered that the buildings be better insulated. This put pressure on the people who do the insulating, which is done by blowing foam. The gas that used to be used to blow foam was CFC-11 but that had been banned. We're now talking in 2010 to 2012. The replacement gas is a mild ozone depleter and it is in the process of being phased out, so the price is going up and the availability is going down. This put the Chinese foam-blowing guys in a strange position. Apparently, what they did was to go to the chemical manufacturers and get the old stuff that worked better anyway. They achieved their goal of making better insulation, but in the process the country seems to have emitted about 13,000 tons a year of this banned substance. Then the government clamped down and fixed it.

Now we have this sort of wishy-washy Paris Agreement about the climate. It's relatively easy to monitor the atmosphere for a wide range of regional emissions; we should do it around the whole world. In fact I wrote a comment piece that was published in Nature about how poorly the world is covered just for the ozone-depleting substances. If you extend that to greenhouse gases, it's the same problem. If somebody claims to be emitting less something-or-other, it would be nice if you could measure the atmosphere well enough to confirm that.

There are three problems that are related to emissions of things that mankind is supposed to be worrying about. One of them is greenhouse gases, another one is ozone-depleting substances, and the third one, the one that is the best funded, is monitoring gases that are emitted from processing nuclear materials. The Comprehensive Test Ban Treaty Organization has a global network. They have 80 stations where they measure radionuclides in the atmosphere, gases emitted from nuclear processing. They can, I presume, figure out whether it's plutonium or thorium or uranium or whatever is being worked on, using these 80 stations around the world. The treaty, the ample funding, the global network and their own satellite data link, are possible because people are terrified about being blown up. They're less terrified—this boils down to human nature—they're less terrified about ultraviolet radiation and skin cancer—and evidently least terrified about the changing climate because they figure if they're well-off they'll just adapt or something. It bothers me that we're not collaborating, and that we're not spending as much on the climate and ozone issues as we're spending on things nuclear.

ZIERLER: The takeaway here is vigilance, that even though the Montreal Protocol was a success, it requires vigilance to keep it a success.

WEISS: Absolutely. Absolutely.

ZIERLER: Finally, Ray, looking to the future, you mentioned before that you don't spend much time dwelling on it, so I'll ask you [laughs] to do that now—where are you bullish that we have, as a civilization, the political wherewithal, the appreciation of the severity of the challenge before us, the technological solutions, that we're going to find a solution to climate change before it's too late, however we define "too late"? Where are you pessimistic, not maybe in your lifetime, but for little kids, in your family or not, that are going to have to live with the choices that our generation and previous generations made?

WEISS: I don't know how to answer that, David. It seems to me that one source of optimism is young activists. As you said, they're going to have to live with what is happening. I'm fond of saying that if you dropped the neutron bomb and killed all the people, climate would still keep warming for hundreds of years.

ZIERLER: Because it's baked in, literally.

WEISS: It's baked in, yes. Those things are all in the atmosphere, and I don't have confidence that there will be a way to get them all out, although we probably have to do that. In the meantime, the poor people in the world will suffer and the rich people will be relatively okay. So, my optimism has to focus on ingenuity.

ZIERLER: Does that include geoengineering, or that's a no-go as far as you're concerned?

WEISS: No, I think we have to think seriously about geoengineering, but we have to think about it in a complete way. For example, if we put things in the atmosphere that absorb sunlight and reflect it to space so that the Earth doesn't warm so much, that doesn't affect the fact that we are making the ocean more acidic with the CO₂, and that has impacts that we don't think about so much, including the stability of dissolved carbonates and the growth of marine organisms. And the sea level rise, if it's rapid, could have a severe impact on certain parts of the planet, and again, poor people are least likely to be able to deal with it.

ZIERLER: That brings the social justice aspect back into this.

WEISS: Yes. I do have confidence in ingenuity—I think we have to have confidence in ingenuity—but I'm not sure what the ingenious answer is. I'm upset about the social justice slowing our path when only rich people can afford to do the right thing, but that's what's happening to the whole planet right now. We do have a problem—in my pressure to monitor things around the world—if we care about the terrestrial biosphere, we ought to be monitoring in places that are not necessarily flourishing democracies. Where some country's monolithic ruler is selling forests that don't actually exist so that I can buy an air ticket, how do you come to grips with that? The best example of observations around the planet I know of is the Comprehensive Test Ban Treaty Organization. [laughs] But that has its problems, too, because certain key countries haven't ratified it.

ZIERLER: It sounds like what you're saying is there is glimmers of hope in the sense that we do have the tools, we have demonstrated the capacity, at least to some degree. There's something to go on.

WEISS: Yes. Another glimmer of hope is that as we become more urban and better educated, our rate of population growth goes down. That's something people are afraid to talk about, but it's of course part of the problem. Maybe as we prosper more, we might have less of a population problem. There are parts of the world now where the population is declining. I think South Korea is one of them, and Northern Italy. In Southern Italy, it's not, but in Northern Italy where all the industrialization is, I believe its population is declining.

ZIERLER: There, the idea is obviously as simple as fewer people, fewer emissions?

WEISS: Yes, of course, and that raises another thing. I'm afraid we could talk for a long time here!

ZIERLER: [laughs]

WEISS: People are always comparing the U.S. and China for emissions, but at the point where the Chinese passed the U.S. in these calculated emissions—because they're not measured, but they're estimated emissions—their population was I think seven times ours. That means the average Chinese person was emitting only about one seventh of what the average American was emitting at that point. It's not that different now, maybe it's one sixth instead, but if you believe every human being has an equal right to the planet and to breathe air and to eat, then we shouldn't be comparing the emissions of China to the emissions of the U.S. except on a per capita level. On that basis I believe Canada comes out really bad because they live in a place where it gets pretty cold in the winter and a lot of fossil fuels are burned to keep things warm. It's also a big country with large distances between population centers.

I'll give you another one! The economists will tell you that if the Chinese are emitting something to make a product that Americans or Europeans are buying, the driving force for those emissions is the fact that we or the Europeans are buying it! So those should be our emissions. Like the European value-added tax system where the taxes are added on as a product moves from one country to the other and gains value, that's probably how we should deal with emissions, and certainly the economists will tell you that. Yet we blame the Chinese for emitting stuff to make things that we buy. That's a little disingenuous.

ZIERLER: As you're demonstrating right now—as earlier in our conversation we were wondering where the denialism comes from—just listening to you, the more you think about it, the more complex is it, maybe it's just easier to deny it? It's just as simple as that?

WEISS: Yes, maybe so.

ZIERLER: Ray, on that note [laughs], this has been a terrific conversation. I want to thank you so much for spending the time.

WEISS: Thank you, David. It's been a honor!

[END]