Oral History Transcript — Dr. Wallace Broecker
This transcript may not be quoted, reproduced or redistributed in whole or in part by any means except with the written permission of the American Institute of Physics.
This transcript is based on a tape-recorded interview deposited at the Center for History of Physics of the American Institute of Physics. The AIP's interviews have generally been transcribed from tape, edited by the interviewer for clarity, and then further edited by the interviewee. If this interview is important to you, you should consult earlier versions of the transcript or listen to the original tape. For many interviews, the AIP retains substantial files with further information about the interviewee and the interview itself. Please contact us for information about accessing these materials.
Please bear in mind that: 1) This material is a transcript of the spoken word rather than a literary product; 2) An interview must be read with the awareness that different people's memories about an event will often differ, and that memories can change with time for many reasons including subsequent experiences, interactions with others, and one's feelings about an event. Disclaimer: This transcript was scanned from a typescript, introducing occasional spelling errors. The original typescript is available.
See the catalog record for this interview and search for other interviews in our collection
Interview with Dr. Wallace Broecker
Session I | Session II
Weart:This is Wallace Broecker, I am Spencer Weart, and this is November 14th, and we’re going to talk about your scientific career. My own personal interest— you know, there are so many different strands and so much going on— the thing that I am particularly interested in is following the history of the realization of abrupt climate change, which I guess at one time meant less than two thousand years, and now it means about less than two years. But there’s lots of other stuff, so we’ll go back and forth with that. So that’s the story I want to follow, but I don’t want to miss some of the other stuff that you’ve been involved in also. I know Ron Doel has talked to you about some of your background and about some of the life here*, so I want to just launch right in with your doctoral thesis. So as I understand it, that began because Ewing and Kulp started a radiocarbon program and you got involved in that?
Broecker:Yeah. Kulp actually started the radiocarbon program. Ewing was the big boss.
Weart:By the way, I am just going to write down some of the names here for the transcriber.
Broecker:Right. I came here as a summer intern in 1952 and helped in the radiocarbon lab. They needed help, even help at my level. Because they were very mediocre people running it. It wasn’t running very well, and I showed some initiative to help solve some of the problems they had. After a few months I was running the Radiocarbon Lab.
Weart:So you were doing the extractions and things like that?
Broecker:Well, a woman named Barbara Eikelmann, who was the wife of one of my fellow students, did the chemical preparations. We were making black carbon, we’d spin it on the inside of cylinders. That’s Libby’s method at that time. I was sort of in change of the counting, the more electronic part. And then when we were going to move over to this building, which was two years later in ‘54, we had decided in the meantime that we had to get away from black carbon counting, because we were getting terrible Strontium-90 contamination, or cesium or something, when we dried the carbon. There was so much fallout in those days that all the dust had radioactivity on it, so we would get counts from radiocarbon and God knows what else. It was really bad news. So when we moved in here we went into gas counting. I designed the Gas Counting Lab, basically using circuit diagrams and counter designs from Argonne National Laboratory. They were doing Krypton-85 measurements. Kulp and I made a Krypton-85 measurement, I suppose in 1953 probably, and Kulp went to Washington, very proudly announcing that we had found, the fission products from Alamagordo and, the two Japanese bombs in krypton from the air. The FBI arrived here the next day and said, you know, “Forget it, fella. You never did that.”
Weart:That was 1953. Right, uh-huh.
Broecker:See, Kulp had just calculated from the kilotonnage and the fission curves how much there should be, and he predicted 10 dpm per liter or something and we measured 8. I mean, it was very, very close to what he predicted.
Weart:It was close to seeing the Russian bomb too, then.
Broecker:Well, there weren’t any then, but wasn’t only the bombs. If you breed plutonium [in reactors], you can’t get it out without letting the krypton off. So their game, Turkovitch’s idea, was it was a great espionage technique, that we subtract U.S. and Britain from world total.
Weart:Then you found out how much the Russians were making.
Broecker:Yeah. I went to Argonne, I suppose around the summer of ‘54 probably and spent a few weeks there, and they taught me all they knew about gas counting, and I then introduced that to here and we went to counting gaseous CO2. So I did my thesis on various aspects of radiocarbon dating, I worked on the ages of ocean cores and we wrote a paper on the abrupt change in climate 11,000 years ago.*
Broecker:We worked on deep ocean water and we showed that Kulp’s early measurements were wrong, which was not a very pleasant thing for him to find out. I worked on Great Basin Lakes, when they were high, I worked on Mississippi Delta sedimentation, when it changed at the end of the glacial period. And so all those things have been, you know, part of my career ever since. I have spent a lot of time on the Great Basin Lakes, I’ve spent a lot of time understanding ocean circulation using radiocarbon, and I’ve spent a lot of time on climate history. Radiocarbon and oceanography and the paleoclimate came together, you might say, with the conveyer belt—
Weart:Right. In the eighties really.
Broecker:These two things I’d been studying actually were one.
Weart:Well, actually even in fact at the beginning the two things were there in your thesis to some extent. I’m curious why you chose, you know— You’ve got the labs for radiocarbon measurements, why you chose to study these particular things. For example, one of the big problems of that time and since has been trying to understand the cause of the Ice Ages, and I wonder if that was presented to you as one of the problems.
Broecker:Well, actually Kulp wanted me to have a last chapter in my thesis in 1957 written about the cause of the Ice Ages. But you know, when I first came here it was sort of a dead subject in that the Milankovitch thing, there had been a big to-do about it, and then a lot of people said, “Ah, that’s bullshit,” and they sort of put it aside. Flint at Yale talked about a solar-terrestrial hypothesis, which is really a lot of words. I mean, it didn’t have any quantitative meat in it. And then Ewing and Donn, I suppose they are the ones that rejuvenated the world’s interest in the subject by creating this crazy theory about the Arctic being open during glacial times.*
Weart:Yeah, I wanted to ask you whether that played any role in your thinking as you were writing your thesis, because they must have been talking about that about the same time, right?
Broecker:Yeah, actually I working with Ken Hunkins here and Guy Matthew to kind of check out their idea. Because if it was open, the Arctic sediments ought to show it up like a sore thumb, you know. The Arctic [Ocean] has very low productivity today. And we did, Ken and Guy did coring up there, and I did the dating on it.
Weart:And when was this? Was this still while you were working on your thesis, or was this afterwards?
Weart:Because Ewing and Donn’s first paper was ‘56, so—
Broecker:Right. So I suppose this was probably in the early sixties that we first started. I could check that out.
Weart:But getting back to the time of your thesis, I’m curious—
Broecker:Well, Ewing was very excited about my thesis work. He liked the idea of a big change 11,000 years ago, because he tied it into his idea about the Arctic. I don’t think I was ever captivated by that idea. And eventually I wrote a paper, because I was kind of angry at Ewing at the time, and I sent him a preprint and I put a special title on it that it was the Nuod Gniwe theory of climate change, and that’s Ewing and Donn spelled backwards. He did not like that. Boy, he was smoked. But basically the work in the Arctic showed that the Arctic was even more tightly closed with ice during the glacial period, which is quite what you’d expect.
Weart:Not too surprising. Okay, so it was in the air, but it wasn’t necessarily anything that pushed you towards looking for abrupt changes.
Broecker:No, but it pushed a lot of people toward thinking about it. Donn was a glib promoter of this, and he’d go around and give lectures that made everybody mad. But in making them angry, they really started to get into it. Johannes Geiss started thinking about how important the albedo was, and how could you really cool off the earth. And then, wait I’ll tell you why. In 1955 or ‘54, Emiliani published a paper showing that Milankovitch cycles were probably really important. And he, for the first time, provided a long record which sort of had those frequencies. Although it wasn’t well spelled out, it looked like you had a 100,000-year cycle. So I was already thinking about that. And some of the work in the sixties, you know, we found eventually in Barbados those high shorelines, that—
Weart:Right. Whoa, whoa, whoa, we’ll get up to that, we’ve still got a ways to go. Because even already in your thesis you said that one of your concerns was to check—
Weart:A brief hiatus. Already in your thesis you mentioned that one of your concerns was the stability of the ocean circulation. You wanted to check whether it was sort of the old constant, steady state flow kind of thing, versus a non-equilibrium model. And I wonder if—
Broecker:Oh yeah, that’s right. You know more about my thesis than I do.
Weart:Well, I just read it. You probably haven’t read it for quite a while.
Broecker:I probably never read it again, but I know what you mean.
Weart:You’d even talked about there being possibly two stable states. I just don’t know where that idea came from at that point.
Broecker:Well, it all goes back. I worried about what we call terminations from way back then. I used to think about it in terms that the glacial cycles were basically either rectangular or, later on when we got the O-18 and started looking at it, the sawtooth.
Weart:You got the sawtooth, yeah.
Broecker:But there was a sharp change in the sawtooth, and the question is what the hell was that. I have always had in my mind that it was a transition between two states. But, until the eighties, it was never really well developed as to what I was really thinking about.
Weart:Yeah. Already in your thesis you found that there could be changes in as little as a thousand years.
Broecker:Right. I overemphasized them. I mean some of those were—
Weart:Yeah, you were clearly looking for it.
Broecker:You know, it’s an interesting story connected with that. There was a guy over here named David Ericson who worked in part of the library in there, that nice, big room were you over there before?
Broecker:Okay. Well, if you go straight in the doors and back in there, that was David’s lab. He had realized that a [foraminifera] species called globertalia menardia, (and it’s mentioned in my thesis), was present in the interglacials and absent during glacials. As he went back in time, it turned out in hindsight that worked well back through the last two cycles. But then he had a long, long period where globorotalia menardia was absent all the time. He thought it was either a very long interglacial or glacial—I can’t quite remember. But I was using in my thesis, as an index of the end of the glacial period, the appearance of globertalia. Now it wasn’t until years later that a man at Woods Hole, Glen Jones, showed an interesting thing. The onset of menardia in the cores turned out, when they were both measured in the same core to be reasonably close to where the O-18 change was. Not exactly. And that change in the O-18 was centered at about 11,000 years. That’s the midpoint of the melting. The actual date of the entry of menardia into the Atlantic was 6700 years ago. The way he did that was by going down core taking menardia samples with the accelerator. Now you could do that. I had to measure bulk stuff. And so the age gets older and older until you get to 6700 and then it stays the same, down maybe 10 more centimeters. That’s a tail of bioturbation. So Ericson by chance was looking at the 6500 years plus one bioturbation depth. And it put him right at the—
Weart:Right. Just by accident.
Broecker:Just pure accident, put him at about 10,000 years ago. But I looked at those curves of his. He used to plot them in a funny way. There was a big [step], when it went from rare to nothing, [laughs], in his graphs.
Weart:He sort of made a step function.
Broecker:Yeah. He didn’t use numbers, so I guess I was never aware of the fact that there was an important increase in abundance through the Holocene, that must mean something. Some of those curves, as he drew them, were like that, and that’s where I got the sharpness. Many times in my career some of the discoveries have been based on false things. But still you go back around and actually the discovery itself was valid, even though the thing that led you to it was wrong. That was one of them.
Weart:Well, there were a lot of step functions in the record. I mean, you know, just this latest paper that you loaned me, you talk about the sudden hiatuses in the geological record. One of the things that existed at that time but that nobody seems to have remarked on then was the pollen. I didn’t notice if you mentioned pollens in your thesis, but were you sort of aware of those things at that time? Can you remember when you became aware of the Younger Dryas and those sort of things?
Broecker:Well, I think I was aware of Younger Dryas in my thesis, wasn’t I, or did you not notice it?
Weart:I didn’t notice it. You mentioned Allerod and so on.
Broecker:See, in the ocean records we never saw the Younger Dryas. In fact, because it’s short duration it would be bioturbated out in any sediments we were looking at then, because with bioturbation depths like that the sedimentation rate during Younger Dryas is—.
Weart:Is much shorter, uh-huh, so you just wouldn’t have seen it.
Broecker:I thought that the high stands of the lakes in the Great Basin might have been Younger Dryas. I was wrong. Those samples of tufa from the high shorelines that I collected, I just ran them; I didn’t then clean them up, I didn’t do anything. And subsequently when people did it more carefully and took the densest tufa and leached it, the ages got about a thousand or so years older. So what I called 11,700 is more like 12,700. Of course we weren’t so sure what the age of the Younger Dryas was anyway.
Broecker:No, I have been aware of the Younger Dryas for a long time. I think I had it in my mind a lot of the time when I looked at these records, but there weren’t an awful lot of really good pollen records then.
Weart:Right, it was just starting to come out.
Broecker:Just starting. There was Van der hammen and people that were looking at pollen. I always found some of those early diagrams looked kind of crazy. I’m a person that looks for unity in things. When I see a really noisy curve, I kind of turn off and say, “Well, God, I don’t know what you can do with that.”
Weart:Yeah. Come back when you have it better. Uh-huh.
Broecker:Yeah. I can’t trust it that it’s really telling me something that’s worth knowing.
Weart:Speaking of which, when you came out with your own thesis with these fairly abrupt changes, did you get any reaction to that? Do you recall whether anybody made anything of it one way or another?
Broecker:I remember people that traditionally studied the lakes in the Great Basin, although Russell— he was the one that did it in the late 1800s, he and Gilbert mapped Bonneville— he put the high stand at Lahonton late. Subsequent workers got the idea that the lake came down in steps and that therefore the highest level is, you know—
Broecker:And when I got the really young radiocarbon dates, I got a letter from a guy, I can’t remember his name right now, but he said I proved that Lake Bonneville dried from the bottom up.
Broecker:That’s what he thought about it.
Weart:Do you remember anything else about the response to your thesis? Did it seem generally acceptable and successful?
Broecker:Well, there’s a difference between then and now, in that we geochemists were not well connected with the geological establishment, and we generally made them mad. I remember some of people or students dated the rocks at Bear Mountain that are about a billion years old, and there was some professor over at, I don’t know, NYU or something, who was really upset because he hadn’t picked the right rock. Qnd he said, “The age you’re going to get depends on the rock” Well, the whole damn area was metamorphosed. You could date almost any rock and get the same age. But there was that kind of conflict. So when we swept in and with a few measurements upset— It would be like when the Alvarezes said they found the cause of [dinosaur extinction]— The establishment immediately gets their hackles up, because they can’t believe that something that they’ve been struggling over for two decades, you come along and solve the problem quickly with some dates.
Weart:With one measurement. Yeah. In a lab.
Broecker:And in many cases isotope work did that. I would guess that we mainly went to meetings with isotope geochemists, and of course they were more interested in things like the theory of the Ice Age, you know, in a more theoretical rather than a field point [of view]. And then with time these fields have nicely blended so that students now know the best of both worlds. My success I think is, I learned early on to appreciate the geology. I worked with Phil Orr, and he taught me a lot of practical field geology. So I paid more attention to results obtained by different methods than a lot of people did.
Weart:Well, another interesting feature is that you had both this field geology, and yet you also classify as an oceanographer in some respects, which is also combining things in I think an unusual way.
Weart:And while writing your thesis you were doing a lot of dry land stuff but you were also looking at cores. Was this regarded as jumping boundaries in those days?
Broecker:Well, when I was a student there were like 45 geochemists in the whole country. There’s probably now 5,000, or God knows how many. So we covered everything from meteorites to, you know, atmospheric chemistry.
Weart:You’d just take any sample. Uh-huh.
Broecker:So each of us cut a very broad swath. I was writing, a thing for Turekian’s birthday of 70 years I think. I wasn’t able to go, but I said of all of us he was the one that maintained the greatest breadth of all. He still worries about meteorites and the mantle of the earth, and I’m pretty broad but I shucked off all that kind of stuff and don’t really think about it very much.
Weart:Okay. One more question about oceanography in your thesis. You know, even to this day you read about being warmed by the Gulf Stream and so on, and I wonder at what point, if you can think, did you at any rate become aware that the warm water is transported up en mass, that it’s this deep circulation rather than the surface currents that are the real story.
Broecker:Well, that gets to when Oeschger pointed out that in the ice cores there were the two stable states. It’s much later, in the early eighties, that I tried to figure out what they were. And I said, Gee, what if you turned on and off the North Atlantic Deep Water? Well, from my thesis I knew it was something like 20 Sverdrups, and I knew that it came in at 13 degrees and went out at 3 degrees. It was an easy calculation, and I was astounded by the amount of heat that it had.
Weart:So it really was then. You know, I’ve wondered, because it seems like it should have been something that was accessible to people already in the 1950s, and yet I don’t see anybody talking about it until—
Broecker:Well, it must have been done, but it was never talked about. Everybody talked about it as the Gulf Stream.
Weart:Yeah, to this day people talk about the Gulf Stream.
Broecker:Yeah, even now. Of course a lot of the heat does move up the Gulf Stream, and more particularly probably the deeper roots, in that the warmest water doesn’t really get up there. I mean that whole complex is moving up. But you know, one thing I never thought about: in the Pacific there are two gyres and the Kuroshio [Current] goes straight across the Pacific to North American and turns south. In the Atlantic the Gulf Stream, you know, a lot of it goes up into the Norwegian Sea. And probably during the glacial period the Atlantic was more like the Pacific, at least at times. So that heat still is coming up the Gulf Stream, but it was going straight out from New York here over to Portugal, and it wasn’t penetrating up into those higher latitudes, and that’s what’s getting warmed by this water. Of course the Gulf Stream I mean carries what, 30 Sverdrups up to what, 50 or 60 Sverdrups and it’s very warm, so—
Weart:It’s very warm, yeah, it carries a lot [of heat].
Broecker:A lot of it’s recirculated, and people were not—well, I don’t they were so much into heat budgets. And there probably was a wing of the field that was, but the cross-over to the rest of us was—
Weart:I haven’t seen it yet. Okay.
Broecker:You haven’t seen it. Well, I haven’t thought about looking it up. I’m not good at doing history. I get too busy doing the present.
Weart:Right. Okay, back to the fifties. I want to quote you something that Wenk wrote in his book on politics of the oceans.* He talks about the oceanographic institutions at the time, Scripps and Woods Hole and here. And he talks about “a personality cult at each with internal loyalties expected and received from staff and students, and with a clear disdain for those in rival camps”. Little cooperation among the three labs. Does that sound right?
Broecker:Oh yeah. Yeah, I’ll tell you a classic story. The year that Stephen Jay Gould at Harvard got his job there as an assistant professor, one of my student, Telu Li, now in Hawaii, got a job there too. We were very proud of him, because as a student he really did beautiful stuff. And I went to Ewing, and I was so proud, and I said, “One of my students got a job teaching at Harvard.” Ewing’s reaction was, “Well, if he was so good, why in the hell did we ever let him get away to the enemy?”—and that’s the way he said it! You know, our ships were only populated by Lamont people or their buddies. In 1972 during GEOSECS, I was the first person to be chief scientist on a Woods Hole ship who wasn’t from Woods Hole. That’s how late that was. And I was given a big lecture about, you know, “They’re uneasy about this, Broecker. Don’t do any nutty things.” [laughs]
Weart:So when it cores for example, was there any sharing with cores, or did you work pretty strictly with cores that had been pulled by Lamont?
Broecker:Well, there was a lot of bitterness. David Ericson very generously gave Emiliani the key cores that he first did his O-18 on, and then without ever telling anybody Emiliani published a paper. There’s some very bitter correspondence between Emiliani and Ewing.
Weart:This was back in the fifties?
Broecker:Oh, wow. And I know those directors used to have to divide up the pot. If you want to find out about those days, go to Dick Barber. He was the young guy from Duke, you know, sitting in with Revelle and Ewing and Paul Fije.
Weart:Uh-huh. I guess I can go and look in Ewing’s correspondence too.
Broecker:Yeah. But, being a young person in those days, I wasn’t privy to what was really going on. One just picked up anecdotal things.
Weart:Right. Well let me ask you about one thing that is connected with this. You and Ericson and some others wrote up some of your stuff in Science in 1956, and you reported this business about there had been an end of the glacial within about a thousand years, and then Emiliani came back with a paper the next year saying that wasn’t so, it must have been bioturbation*
Broecker:Well, that’s that menardia versus O-18. Emiliani was right. Yeah.
Weart:Uh-huh. Did you have any personal interactions with him about that?
Broecker:Not about that, but we had some personal interactions about some other things. In fact, we got into a bitter debate. Emiliani got some people, Piccioto and Geiss, and they took a core from the Caribbean, and they did uranium series ages on it to establish a better time scale. Because radiocarbon didn’t go back very far. And they got an age for what we now call Termination 2 of 80,000 years. I picked that up and we did our own work here, and we showed that they were wrong, that it was 100,000 years. Now, this made a big difference when you compared it with Mikankovitch, or actually 120,000 years, so it was a big difference.
Weart:Right. This was in the seventies, right?
Broecker:No, that was in the sixties, wasn’t it?
Weart:I don’t know. Let me check here. Yeah, right, the key paper was Broecker and Van Donk in 1970, so that was where you published.*
Broecker:Right. But were already arguing about it before. There were some papers by Elizabeth Rona and this dragged out a long time. Just about the time CLIMAP was starting, when IDOE started in the very late sixties, Emiliani had finally been beaten on all these things. He said two things. He argued with me about the time scale, and he argued with Imbrie, et al. saying that the main reason the O-18 changed in the Caribbean was temperature, whereas people were by then saying ice mass. He fought— [end of Tape 1, Side A] [beginning of Tape 1, Side B]
Broecker:Emiliani was a classic case. That paper of his in ‘54 or ‘55 in Geology was, I would say, one of the all-time great papers, his first O-18.* It’s a superb paper. Well, he was the kind of person that everything had to be right, you know. So what we were arguing about was some minor points really. I mean it didn’t really take that much away from the paper. But he stuck doggedly through his whole career, and he ruined his career that way. After he left Chicago and went to Miami, he did very little of any significance scientifically. Here is a guy of great talent and so forth who loved to argue with people about anything.
Weart:What kind of forums were these in? Are you talking about face-to-face at meetings, or mostly in the literature, or letters?
Broecker:He was funny. Emiliani never flew, so he didn’t go to that many meetings. But I remember we had a special, like, debate session at the Geological Society of America. It was held in Miami. Of course he could go, that’s where he was. That was his Waterloo, because then everybody ganged up on him. He was trying to hang onto a couple of these points when the world had decided that that isn’t the way it was.
Weart:And that it was really ice volume. Uh-huh.
Broecker:Emiliani was a really difficult person to get along with. I mean, the same as [Harmon] Craig—charming guy, I mean you know a really interesting person, but so combative that he just drove people nuts. So CLIMAP I think very wisely did not let him in.
Weart:Is Emiliani still around, by the way? Could I go and talk with him about some of these things?
Broecker:Dead. A few years ago. I mean you could talk to Imbrie about his—
Weart:Well I’m interested of course in that 1950s work.
Broecker:Yeah. Well, the way Imbrie got interested in this whole business of late Quaternary science was that we held in the mid-sixties sometime— the first meeting I ever organized, held here at Lamont— a debate between Ericson, who said his menardia stratigraphy was the best way to look at past glaciations, and Emiliani, who said O-18 was the best way. Of course I think Emiliani had to win that hands down, because it just made more sense. Why would you get oscillations that did go with the glaciers and then more oscillations that didn’t go with the glaciers? That was an important meeting in that it brought these two people who were angry with each other, especially Ericson was angry with Emiliani. Emiliani came up here by train.
Weart:This isn’t the Miami GSA meeting, this is another meeting now that you’re talking about.
Broecker:This is a meeting held here at Lamont, a few years earlier. I think Imbrie must have left here about ‘68. It was just before he left, and that got him started, it got him interested in the whole Milankovitch problem.
Weart:I see. Well, let’s move on then to your work on Milankovitch and so on, because we need to talk about how you got involved in it. Now I ran across a reference by Ericson and Wollin, in their book The Deep and the Past, where it seems like their main interest in all these things was establishing a time scale for human evolution.
Broecker:You know, Wollin was a real piece of work. He was a Swedish journalist with no formal training in anything who came here to Palisades, God knows why, and was desperate for money, and he got a job opening cores for Ericson, and then worked his way up to being Ericson’s equal. Wollin had this idea he wanted to win a Nobel Prize. I mean the guy was, you know, basically bonkers. And where were we—?
Weart:Well, of course there’s the motivation. Why study time scales anyway? You know, what’s the reason for trying to get exact timing in these cores?
Broecker:Well, I think the reason that a lot of us were trying to improve the time scale is the correlation with Malonkovitch, you know, how did O-18 changes match with the insolation curves.
Weart:So you got inspired basically by Emiliani’s work then.
Broecker:Originally interested. And then, what really turned me onto it was when Robley Matthews from Brown called me up and said, “Wally, would you be willing to date a couple of raised [coral] terraces in Barbados?” Now he was not interested in climate; he was interested in diagenesis, because oil companies wanted to know how long it took coral to lose its porosity or whatever. So we dated two of these terraces and we got like 124 and 82, [thousand years]. And the old Milankovitch curves, emphasized a 40,000-year cycle, because the way he calculated it, he was looking more at high latitudes— in fact I’m not quite sure why he did that. Well, I called up Matthews and said, “My guys here got those two ages, and look, they’re right at the 40,000-year frequency.” And he said, “Well Wally, there’s a third terrace which is halfway in between.” So he sent me that, and that was 105. So then for that paper I wrote on this— Broecker and Van Donk or somewhere— in one of my papers I redid the radiation calculations my own way.
Weart:The insolation calculations.
Broecker:Insolation. And I showed that if you looked at latitudes like 45 or 50, there was a lot more 20,000-year power in there. And in particular, a peak that was just a small shoulder on the original Milankovitch curves became a decent-sized peak. And that was 105, so I said, “Aha, we’ve got it pegged right on.” Those were the right on the Milankovitch dates. And of course those dates have stood the test of time. Now with the new mass spectrometry they get the same age with a much higher precision. But that really got me interested even more so in Milankovitch, and just moved a step along.
Weart:Did you encounter resistance to that? Did you find there were anti-Milankovitch people?
Broecker:No, not at that time. [laughs] No. Well I think the people who were more mathematical probably weren’t yet convinced, and then Hays, Imbrie and Shackleton in that paper* really swept them into the fold by showing that if you did a power spectrum you would get the proper frequencies.
Weart:Right. Well you also went and got those New Guinea terraces too. Did you go there, to New Guinea?
Broecker:Yeah. That was great.
Weart:That was field work.
Broecker:I was going on a test cruise for GEOSECS and I took a side trip over to New Guinea and spent a week with Bloom and Chapell, and we climbed around there and lived in the mission house.* This was when there were cargo cults, I mean it was really exciting. The coast we were on, I think there were besides us only three other white people within 50 miles. We went on a mission boat that dropped us off at Sialom, and it was rough as hell.
Weart:So the access was by way of the missionaries.
Broecker:I was the only one, except I suppose the captain, who wasn’t throwing up. It was awful! [laughs] Really. I don’t know how I kept my stomach. [laughs] But yeah, that was an exciting trip, and those are amazing terraces.
Weart:Had you done other field work in between on these things? There was Barbados I guess—
Broecker:Well, I worked in the Great Basin a dozen times and—
Weart:That’s right. But the Barbados ones they sent you those samples, you didn’t go there yourself?
Broecker:I went there later with Matthews to see them. I went there three times, because once I got interested I wanted to see them. One of my students, Mike Bender, who is at Princeton now, did helium-uranium dating, and we put a lot of effort into trying to understand the whole sequence of.
Broecker:But the field work I did most of the time was mostly at sea. I mean I did Bahama Banks work, I was on the ODP [Ocean Drilling Program] drilling ship in Cariaco Trench. I think I’ve spent about two years of my life at sea. But the place I did the most field work other than that was the Great Basin.
Weart:You went back there several times.
Broecker:In 1988 or ‘87, whatever it was, I organized a field trip to the Southern Andes, which got Denton started down there.
Weart:Oh, is that so?
Broecker:Oh yeah. That was funded by Exxon, twenty-five-thousand-dollar field trip. We took 20 people. I think there were ten South Americans from various countries and ten people from other places. We had Australians—
Weart:This gets us out of chronological sequence, but what were you looking for? Why did you pick the Southern Andes?
Broecker:Well, I had realized that mountain glaciation was enormously important, because the snow line is—
Weart:The snow line went down [in glacial times], yeah.
Broecker:And then went down on both Hemispheres, by about the same amount. There were lots of debates about the dating and this and that, so I wanted to see them myself. We went from Ushuia up to Mendoza, and we looked at six or seven localities and we had a marvelous, marvelous time. And Denton, because of that, went on. In fact, one of his Chilean students, just gave a lecture. That was one of the things I had to do instead of see you, was that he came and George said, “Please listen to this guy,” and I said, “Oh my God, how am I going to do that?” So, anyway.
Weart:Okay, now let’s get back to the 1960s. One of the interesting things that is starting to come out there is you had a paper in 1966 which is one of the places where you talk about the Milankovitch triggering a mode shift, and that gets us back to the whole idea of various modes and so on.*
Broecker:In ‘66 what was it—was that the one given in Colorado?
Weart:Yeah, I was going to ask you about that ‘65 Boulder Conference seems to have been interesting. A lot of people.
Broecker:Yeah. Peter Weyl talked about the stagnation of the Atlantic and vapor transport across the—
Weart:Exactly. That was I think the first place he talked about that.
Weart:Can you recall, do you think that was the first place you started to become aware of salinity as being a major feature?
Broecker:The only thing I can think of is some gorgeous woman I met there. [laughs] I remember that meeting, but not very much.
Weart:You remember Weyl was there.
Broecker:Yeah. You know, I look at that volume every now and then, and I remember being there, but I remember I went back many years later and tried to figure out where I had been on the campus, and either my mind had forgotten so much or the campus had changed so much, I could hardly place, my first trip there.
Weart:Okay. Well let me mention a couple of other things that were sort of in the air at the time. There was ideas about albedo feedback, there were people excited about that.
Broecker:That was Geiss who wrote a very nice paper, Johannes Geiss.* He’s a sort of an asteroid or comet physicist at Bern. He went to Miami for a sabbatical, and he wrote a paper on that. Because were all searching. I mean, we still are. What in the hell caused it, how could the earth ever get itself into such a different climate state?
Weart:And there is no question that there was glacial and there was nonglacial. That’s clearly two modes.
Broecker:We knew the ice was in Cincinatti. We may not have known how much the tropical temperatures were. That was the big surprise, of course, of CLIMAP that Emiliani didn’t like, that they maintained that the temperature change was quite small. Now the pendulum has swung back somewhat toward Emiliani.
Broecker:Because, you know, the tropical temperature change, CLIMAP said it was one or two degrees, and it probably was three or four degrees. And another thing about this, I got so interested in the snow lines, because there was no way CLIMAP could explain the lowering of snow lines that much in the tropics with one degree. So with Dorothy Peteet and David Rind, you know, we got into thinking more about the snow lines.*
Weart:Right. Let me ask you now about this, when you realized that it was a sawtooth kind of a curve, your paper with Van Donk in 1970. Do you recall the origins of that, how you came to see things that way? Just did it naturally fall out of the curve?
Broecker:Just looking hard at those curves. One of the things that was interesting, to go back to Emiliani’s paper, the only curve that really didn’t look triangular was, a core about 43 degrees north in the Atlantic, the only one he ran, and that had much more of the Milankovitch, you might say subfrequencies in it. It may be because it was a higher deposition rate. See, a lot of this was how much of the record is sort of, schmoothed out. But a lot of those early records looked like that. Then when people got into looking at higher deposition rate cores, then these curves assume more structure, you know, there’s more there. It just wasn’t found. They also started to do benthic [foraminifera], which Shackleton started— learned how to do benthics, which are very rare. Emiliani did them, but only in cores that had incredible amounts of dissolution. In a normal deep sea core for every 400 planktonics there is one benthic. So if you have to pick 200 of them to make an analysis, well, it’s almost impossible.
Weart:It takes a lot of looking, yeah.
Broecker:But when you dissolve away the carbonate, the benthics tend to be the most resistant, so there are cores in the equatorial Pacific that there is one for one. You pick those out. In hindsight you got a lot of funny numbers, and there may have been all kinds of bioturbation effects and things that we never thought about in those days. Shackleton was the first one to come along and really show that. Because see, Emiliani said that the deep amplitude was very small, and he calculated sort of a minimum amount of ice volume with a minimum O-18 fractionation, and got that that was only three or four tenths per mil, and all the rest of it was [due to] temperature. He said that didn’t appear in the deep sea and therefore it couldn’t have been ice volume.
Weart:Okay. Now, getting back to this 1970 paper, one of the interesting things in there is that you use this to extrapolate into the future. Now we’re getting where we haven’t mentioned before, the anthropogenic global warming story.
Broecker:I like that paper. [laughs] I intend some day— wait a few more years— and put over my simple curve that I got in that ‘76 paper, the actual temperature trend.* Because what I predicted, using just this funny thing from the ice cores, probably was one of these false findings. Dansgaard said that there was appreciable 80 and 180-year periodicity, so I just took that and extended it. I said well, that means that during the times when the globe wasn’t warming, it was just in a natural cooling phase. And I said, “Boy, one of these years when they start to work together and CO2 has gone up a lot faster, it’s going to take off.” And basically it’s done that.
Weart:But now I wanted to differentiate here between two papers, because your paper with Van Donk in 1970 just talked about the broad trend, which of course would be just taking the large scale Milankovitch cycles, which would be for continual gradual cooling.*
Broecker:Oh, predicting the Greenhouse future, oh yeah.
Weart:Then in 1975 you put in these Dansgaard cycles, and also at that point you put in global warming, where there is carbon dioxide going on. Sometime in between there— I mean you had known about the idea of global warming since before, but at some point there you became aware of it as a problem.
Broecker:Well, you know, one of the things, during that period when it wasn’t warming, various people said various things. Gordon MacDonald wrote a paper once where he said— it’s interesting, because it’s one of these that nobody put much stock in it at the time—well, they did and then they dropped it—was that sulfate was cooling the earth and these two things were canceling.
Broecker:And so I said well maybe it’s not the sulfate. Then sulfate sort of disappeared from the screen for what, almost 20 years, and then suddenly in the nineties has reemerged as a major issue.
Weart:Right, right. In the seventies there was also Bayson talking about his particulate as a cooling factor.
Broecker:Oh yeah. Now that was a can of worms, because he took some data that apparently the measurement technique hadn’t been recalibrated. When they put the calibration in, a lot of what he said went away. He said the sky was becoming a lot less transparent. It’s interesting to go back and say in hindsight how close were the people and how much of it was true and how much of it was a hunch that they had that they were defending with lousy data. Because a lot of what we did turned out to be, making wrong assumptions about what measurements were trying to tell you. That’s how I got into the whole abrupt change thing, it was through CO2 and the Greenland ice cores, and those big changes are phony. But it led me into thinking about it.
Weart:Now just a minute, which change are phony?
Broecker:Well, the thing that really turned me on about abrupt changes, and sent me to the ocean, was when like ‘84, around there, the Swiss showed a record during mainly stage three where they had CO2 changes that were rectangular. That’s a lot of noise, but they had a whole group of points of up here and a whole group down here. And it went from like 195 to 245, 195-245, and for a long time we thought those were correct. So I said, “Well, hell, if that’s the case, it’s got to be the ocean, and there’s got to be big time changes in the ocean to ever do this.” So then I started to think in terms of well, you don’t do this with a minor change in the ocean; you better upset the whole circulation and do something different. Oeschger then, when he gave that talk showing these things, said, “I think this is telling us that climate had two states.” So he was thinking in terms of those things too. A lot of us had passed all those noisy stuff off, in Greenland, I don’t know, it’s like the curves I was telling you about, I don’t know why in Greenland, it’s just something to do with Greenland. There was no repetition, you know, it was just a one time [observation].
Weart:Right. It could have been something happening in the ice, the ice slipping and so on.
Broecker:Yeah, who knows. It was so different and it was very interesting, but we didn’t put any stock in those things. At least I don’t think any of us did, until the CO2 measurements were made, and that caught everybody’s attention. Because we knew CO2 screamed “ocean”.
Broecker:I remember the meeting we had in Florida in 1984. We discussed this, and it was almost impossible to think of how in the hell you could ever change atmospheric CO2 so fast. Well it turns out now, we’re almost positive, that those intermediate high CO2s were from the fact that the ratio of acid to dust in there was such that during the lithification or thereafter the acid released some CO2 from the dust.
Weart:So it was the dust events you were seeing, uh-huh.
Broecker:And so it was false. One of the things we should have known is there is no lag, no offset in the ice between the O-18 changes, which are in the ice, and the CO2 changes, which are in the bubbles. And how could you do that? I mean unless by coincidence. Then Oeschger at one point had a student who did very detailed measurements, and they found that this whole change occurred in 2 centimeters in the ice or something, and it became more and more ridiculous. Then they went and looked in Antarctica, and the Bern group wrote a paper where they didn’t have the chronology very well, but they hammered away so many points and said no way we could have missed it, we were in the right section of the core. They did like 200 [data] points, and they were, none of them showed the 240 values; they all showed the low glacial value. But it’s interesting that that’s how this whole thing got started.
Weart:Okay. Getting back to the seventies, I want to ask you now, getting more into the area of political kind of things. You began to write some articles, you know, “Are we on the brink of global warming”? you gave testimony to Congress and so on*. How did you get involved with the idea of warning people about global warming? Is there any particular person who was involved in getting interested in that, or—? This is a period when other scientists, too, were starting to do that.
Broecker:I was thinking the other day, because I was a little bit pissed off at Jim Hansen for something he did, that— you know, I stopped that after ‘75 or whenever I wrote that article, because Jim Hansen at GISS really picked it up and he went into it with more vigor, and he looked at volcanos and looked at all aspects of it, what might have been controlling the natural fluctuations. And I went away from it.
Weart:Were you concerned about government funding climate studies?
Broecker:That’s what I was just thinking about. We were trying to get that CO2 program going, because we wanted the research money for one thing. But I never would have said it if I didn’t believe it, because that’s not the way I am. I mean, you know, I really—
Weart:No, but there are reasons for going and trying to affect the public and talking to Congress and so on. This is a CO2 program, the CO2 monitoring program in the early seventies. And what was your involvement with that? Did you have anything to do with getting that started?
Broecker:Well, I had been involved all along in trying to understand the fate of the CO2. You know, because I’d done gas exchange in the ocean, vertical mixing, GEOSECS was all about trying to get the data—
Weart:Yeah, we have to get to GEOSECS.
Broecker:I was very much involved in trying to understand the carbon cycle, and of course that involved trying to understand the fate of fossil fuel CO2, so it’s a natural thing to think about. I used to teach in my classes, I remember using one paper that had a lot of influence on me— a paper that Manabe wrote with his professor back in, like, ‘63, where they did a one-dimensional model of the atmosphere and they calculated the water feedback.* I found that fascinating, how do you go about doing that. They came to the conclusion that it was sizeable, that [feedback] kicked up the warming from one degree to four degrees or something. They had about the same kind of result you’d get in a general circulation model.
Weart:Yeah. It’s always puzzled me that that one-dimensional model already gave the—
Broecker:Yeah. It already gave it. And I think that convinced me that this was a thing to worry about, if this water vapor feedback was so strong. I suppose it came out of teaching courses, for one thing. A lot of what I do comes out of teaching courses, because it makes you think about things a lot more than you would if you didn’t teach courses.
Weart:You have to go back to the basics, yeah. Well, let me ask you about what relationships you may have had with people in Washington. First just to check off some things, did you do any work for the DARPA program? Because DARPA was doing some things.
Weart:There was the CIA climate study.
Weart:Okay. Any work with JASON or those people?
Broecker:No. I never.
Broecker:I’ve never done classified work, and I’ve never been a consultant to anyone except for four or five times in my whole history where I sold my brain to somebody else. [Laughs] I’ve been a real ivory tower academic.
Weart:Okay, well then let’s talk about DOE, or maybe also we should ask about you and Harmon Craig and GEOSECS. Do you want to talk about how that got started?
Broecker:I was just writing about that in that little chapter. I was at Woods Hole for some meeting, and Henry Stommel came around to the meeting (it didn’t have anything to do with him), and I think Ed Goldberg was there with me, and he took us aside and said, “You, Wally, measure radiocarbon in the ocean, and you want to learn more about circulation. You’re never going to make it pay until you do a real traverse, at least the whole length of the Atlantic, and do stations every five degrees”. And I quickly calculated what that would cost, a thousand dollars a measurement, twenty stations, that’s a half million dollars. And I said, “That’s a great idea, but nobody would pay for that”. We were a small field, fifty thousand dollars was a lot of money. So he said, “Well I’ll tell you a secret, there’s going to be a new program called IDOE”. International Decade of Ocean Exploration– for the ‘70s. Stommel heard it around Woods Hole. So the next time we were there, and I can’t remember how many months went by, I had told Harmon Craig about this, and Harmon Craig and I went to visit Paul Fije. I’ll never forget– we were waiting in his outer room, and there was a book o his coffee table that showed events at Woods Hole. And there was one of Paul Fije presenting the Bigelow Medal. He had this thing in his hand, you know, a black leather thing opened up showing the medal, and so we cut out a piece of paper and wrote a bubble like you’d have in a comic strip. It says, “I’m Paul Fije from the FBI.”
Weart:[laughs] Like showing a badge.
Broecker:It looked exactly like a badge, and Paul Fije had the very much a look of an FBI guy. [end of Tape 1, Side B] [beginning of Tape 2, Side A]
Weart:So you’re in his office at Woods Hole.
Broecker:Yeah. And so we went in and talked to him, and he explained the IDOE to us. He said there was an interim committee that was going to choose the programs. They said they really liked the idea of having a pilot program, because these were exactly the kind of thing they’d started to think about, to do an ocean survey. And so we moved in on the ground floor, we got what we wanted. We expanded it from just radiocarbon to almost every geochemical property we could think of that would be valuable to measure.
Weart:The “we,” was this you and Craig who worked this up or—?
Broecker:Well, originally John Hunt worked with us at Woods Hole, and then Derrick Spencer took over for John. We were the triumvirat.
Weart:These people were all spread out, right? You were here, Craig was at Scripps, and these people—
Weart:Do you have correspondence remaining from those days?
Broecker:I don’t know, I suppose we do. I never look at stuff like that. God knows what’s in there or whether we’ve thrown it all out.
Weart:Would your secretary know about that?
Broecker:No. I mean, she could go look, but Ellen Cox died, too bad, she died about a year ago. She would have known.
Weart:Maybe we ought to go to look for it sometime. Because that would be interesting, give you a good way to see how it evolved.
Broecker:I don’t know. We did a lot of stuff by telephone and in meetings. But we agreed to run this program, and we hired a man named Arnold Bainbridge, who was a scientist at Scripps. He turns out to be the most important person in the whole thing, bar none.
Broecker:Because he put together all the apparatus, hired all the technicians, wrote all the computer programs, did all of this in a period of like 18 months. Absolutely incredible. Because they had so many things to do. They ratcheted up the whole field in technology by like an order of magnitude. And you know it hasn’t really ratcheted another order of magnitude since then. We’re using basically a lot of the same things that we installed in the early seventies. And he made it work, as I said in my chapter, he never missed a beat. Everything went off as it should. We made very few mistakes. The quality of the data was universally high. We’d pick people—we were allowed in those days to do things you couldn’t do now— in other words, we orchestrated it. We decided who the people would be; we had test cruises; and anybody was allowed to compete, but then we picked the best analyst. Of course in many cases we knew already who was the best analyst. Because we wanted high quality data.
Weart:Again, who is the “we” here?
Broecker:Spencer and I and Craig, and a committee of about eight geochemists, Osland and Stuiver, who did the radiocarbon, Karl Turekian at Yale, and the four of us, Bainbridge, Spencer, Craig and I.
Weart:So would you get together on the phone or—?
Broecker:Well, no, we used to meet all over the place. No, we did a lot of personal meetings, and that’s when we accomplished things. Then Bainbridge put all this group and stuff together at La Jolla, and we did a test cruise off California, and we did a test cruise off Woods Hole, and we did a third test cruise off Samoa. That’s when I went to New Guinea on that same trip.
Weart:Oh, you stopped off there.
Broecker:Yeah. And then we did the real thing starting in what, September 1972. That went on until 1978, with somewhat of a hiatus where NSF couldn’t decide whether they wanted to let us do the Indian Ocean. Luckily we did.
Weart:Oh. It was just a matter of waiting for them to decide and pounding on them?
Broecker:Oh, yeah, getting the money together, I don’t know. Feenan Jennings, who managed the IDOE, he was just, boy, talk about a guy who knew how to do it, and kept us all happy. At least our program—what was it called? MODE, the physical oceanographers program, and CLIMAP were all very successful. One reason was that this kind of thing had never been done, and the power of putting all these people together, where you have a virgin field in a sense, nobody’s ever done this. Now it gets crowded, and there’s a lot of competing programs and territories, you know, the cream has been skimmed off. Well, we skimmed off a huge amount of cream in those years, you know.
Weart:Right. For GEOSECS there was room for everybody.
Weart:There weren’t that many people.
Broecker:We had institutions all over the country. And we had people from Germany, India, Devendra Lal from India was a big part of it, K.O. Munich from Germany, and people from every oceanographic institute in the U.S. We didn’t try to keep it at all within our institutions. We picked for each property the best person, wherever they were.
Weart:Was there ever any question about ownership of the data, who would get to publish or whether things should be approved for publication?
Broecker:Actually it turned out not to be a big problem, because I was the only big publisher. Craig didn’t write many papers. I would say, not as much as there is now. Minze Stuiver was a bit pissed off with me a couple times because he thought he wrote about things that I shouldn’t have, but I said, you know, “This is five years after we gave you the samples. You’ve had the results for two years. How long have we got to wait?” But Minze and I have remained really good friends, so it was just one of those things— that was a minor problem; it was not a major problem, a very minor problem.
Weart:And you were satisfied when the money ran out that it was more or less at the point you expected and you had enough money to do it?
Broecker:We had enough money to finish it. What I calculated originally would be a half a million dollars, with ship time a million, came to twenty-five million. [laughs] But it was a bargain. God, the number of properties we measured. It is the foundation for all chemical oceanography and tracer oceanography. Everybody builds on that original dataset. Expeditions are planned according to it. I mean, it’s the standard. So that was a real Camelot. Those were really heady days. We all got along well, we had a lot of fun, we traveled around the world, the technical group that Bainbridge put together was— I don’t know how he ever found such a group of wonderful people—hard workers, pleasant to be with.
Weart:They were here?
Broecker:No, they were all Californians mainly.
Weart:Uh-huh, so at Scripps.
Broecker:Yeah, because Bainbridge was located there. It’s now changed names, but it’s still an oceangoing logistics group. It does nutrients, temperature, salinity. Bob Williams runs it now. He was a key member. I’ve got to go at about five-five-thirty.
Weart:Yeah, yeah, I was going to say. I wondered if we have—
Broecker:That’s okay. We can go to 5:30.
Weart:Okay. Well, let’s just talk about one or two other things. I don’t think we’ll get quite through this. This just flows to some extent out of GEOSECS. As you started to get interested, you and Peng did some carbon cycle box models, you got interested in the oceans as a sink for carbon, and not the biosphere.* So first of all, who is Peng, and where did he come into this?
Broecker:Peng was a student of mine. He did a thesis on gas exchange in the lab, and also did work with me on radon measurements at sea. He stayed on here as a postdoc, or a young scientist, for a number of years. I think it was in 1980 when I got lymphoma, and I didn’t know whether I was going to survive or not. Eventually it went to the third stage. I’m a lucky person.
Weart:Yeah. I had noticed, and I was going to ask you, there was a period in the eighties when you didn’t produce very much [journal articles]. Was that because you were laid up?
Broecker:No. I wrote Tracers in the Sea* while I was in therapy.
Weart:Oh, oh, you were writing.
Broecker:It was entirely written. So that sort of was a summary of GEOSECS.
Weart:I see. So you were busy doing that.
Broecker:Well, in the early eighties. I don’t know what controls that, but I was trying to update my Vita. I noticed I have three hundred and forty-some papers now in about 40 years, so I suppose about nine a year. I ought to make a histogram sometime of how many in each year and what were the high years and what were the low years. Anyway, Peng got into modeling, and he is very good at it. We worked very well as a team. He could do the programming and run the stuff, and keep up with the improving computer world, and I could do the thinking. So in 1980 he got an offer at Oak Ridge, and I said, “For Christ’s sake take it, Tsung-Hung, because funding is getting difficult, and you’re getting expensive, and it’s hard to keep you on soft money.” I said, “I don’t know what’s going to happen to me, you ought to, we can still work together.” And so we did. We worked together up until a few years ago when he want down to Miami. The things that we could do well together we’d done. We’re still good friends. That collaboration went for, God, a long time. There were a lot of Broecker and Peng papers.
Weart:Yeah, there certainly are, right.
Broecker:He a really nice guy. I remember when he first came here, Jim Simpson, who still teaches here, and Mike Bender, who is now at Princeton, used to tease him. They said “Look, Tsung-Hung, when Broecker tells you something, he expects you to respond in the right way. You’ve got to show him you realize what he said was important.” So Tsung-Hung says, “What do I say?” They said, “Just say, ‘Bullshit’.”
Weart:[laughs] Okay, you do these models for how the carbon goes into the ocean.
Broecker:Bomb radiocarbon is the king of all these tracers for the carbon cycle, it carries the most information. We’ve done a lot of stuff on various aspects of the radiocarbon cycle, both natural and, particularly, the bomb. That’s the time tracer that tells us how to make a model that more or less replicates what’s really going on. The box models we made and other people made are amazingly close to the general circulation models for CO2 uptake. And that’s because there’s a lucky [circumstance]. Oeschger first pointed this out. He made a model with a mixed layer and then a diffusive ocean below it, and all you had to have in that model was the thickness of the mixed layer and the diffusivity of the underlying layer.
Weart:Oh, it’s just the two-layer models, uh-huh.
Broecker:And Tsung-Hung and I showed later that this model works amazingly well, even though it violates heat [balance]— you know, if you had the ocean operating that way it would be warm at the bottom. Natural radiocarbon gives us an overall ventilation time of the ocean of about a thousand years, and that’s for a thickness of 3800 meters. Bomb radiocarbon said, on the time scale of ten years, the ocean mixed to about, on the average, 350 meters. Well, a thousand, uh, 3800 over— That’s the square root relationship between time and distance. So that [two-layer] approach worked very well. I don’t know whether the general circulation models give a better number or a worse number, but that number is certainly within the error of both. We both for the period of the eighties got like 2 gigatons [of carbon] going into the ocean. And there was this huge debate, you know—
Weart:Yeah. And don’t just jump pass that. Tell me about that. How did that start? This is Woodwell and the other people?
Broecker:This was that asshole Woodwell, yeah. You can put that in.
Weart:Okay. That’s on the tape now.
Broecker:He went to Venezuela, and he found this area which is one 1300th of the total global area or continental area, I can’t remember. It was on the border between Venezuela and Columbia. It was being heavily logged, really heavily logged. He took that number and extrapolated it—
Weart:Multiplied it by the area of the— Uh-huh.
Broecker:By 1300, you know, and he got originally that the amount of CO2 being released by deforestation was five times higher than the amount [usually estimated]. He used to drive me nuts. And then this number gradually came down. There is a paper that Simpson and I and Taro, I think, wrote.* The last line was pretty good. We said, “When we do the budget it appears that the global biomass has stayed about the same. And so that means that any forest cutting, whatever it was, had to be balanced by some kind of greening”
Weart:By uptake somewhere, mm-hmm.
Broecker:And up until Keeling’s work— it wasn’t Keeling (Keeling started to do it better, because he could do the oxygen,)— up until about the late eighties, that was probably about right. And then for some reason, probably a climate change, the biosphere is packing away carbon like beJesus. But that’s not going to persist. It can’t. I mean that stuff’s got to be eaten, so that it won’t go on for very long.
Weart:But for quite a period there, people were quite uncertain as to—
Broecker:Missing [carbon] sink. So people proposed all kinds of things, and everything they proposed was shot down. One of the neatest things Garrels did is just saying, “Well, take all the nitrogen that’s ever been fixed, and say that no matter where it went each nitrogen atom mated with ten carbon atoms, because that’s the average for plankton, and so on.” He said, “That’s an upper limit on how much the nitrogen could have done.” And that turned out to be a couple tenths of a gigaton. It was small. That was a way to look at the whole damn thing. And then if you used the CO2 growth enhancement that came out, and did models that way, I’ve always been interested in soil radiocarbon. Susan Trumbore, who is now a superstar at the University of California, Irvine, and another student after her, Kevin Harrison, now a professor at Boston College, were able to establish the turnover time of the humus in soil. That’s important because if you’re perturbing it by adding more carbon, then you have to have that time in order to figure out how it’s going to evolve.
Weart:What I’m not sure about is what was at stake here. Why did this become, you know, there’s a lot of uncertain numbers. Why does it become—?
Broecker:It was biologists versus oceanographers. They used to say, “Your ocean models are wrong,” and we used to say, “Bullshit. Our ocean models are good.” We’d just say, “You’re just overestimating what’s happening on the continents.”
Weart:So it was because they weren’t able to follow your models and you weren’t able to argue in their language?
Well, I would say there was no way in hell they could evaluate, with the information they had, what was going on in the continents. Of course, when this all started in the seventies, you could argue about the ocean models. But we always vigorously defended that, because of the argument I just gave you, that we could not be very far off. We knew the gas exchange to a gnat’s eyebrow, really. And then the natural radiocarbon and the tracer tritium and bomb radiocarbon really— [phone rings]
Session I | Session II