Oral History Transcript — Dr. James Hansen
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Interview with Dr. James Hansen
Session I | Session II
Weart:Itís November 27th. Second session with Jim Hansen here at the NASA Center in New York on November 27th, 2000, the millennium. Okay Jim, this time I want to talk more about public relations. This of course is indistinguishable from the scientific department. Just a general question to start out, was there any particular time when you became aware that what you were doing was not only to long-term scientific stuff, but had short-term public interest?
Hansen:Well sure, that goes back a long time.
Weart:Yes. How did that evolve?
Hansen:Well, I was aware of that question of scientists communicating with the public from the beginning because of a friend of mine, Jim Pollack, who was a colleague of Carl Sagan. I mentioned this in a talk I gave, I guess it was called a Symposium for Carl Sagan a few years at Cornell, about public understanding of global climate change. I mentioned that Jim Pollack and I were sailing on a small lake in New Hampshire, actually becalmed on a Sun Fish. But that day, Carl Sagan came to the Gordon Conference and he was a little depressed because heíd just learned at that time that he didnít get tenure at Harvard.
Weart:Oh, that was way back.
Hansen:Yes. This was when I was a first year post-doc, 1967, maybe í68. Our presumption was that his failure to get tenure was partly because of his propensity to communicate with the public. And in fact, Jim said, ďWell someone pasted on the bulletin board, newspaper articles quoting Carl Sagan as saying the speed of light is three timesĒ you know. His colleagues didnít like his time spent on that. I guess the attitude toward that may be changing somewhat; I think thereís less negative response to that sort of thing now.
Weart:So in a sense you became aware that it was an issue.
Hansen:Yes. But see, Iím the opposite kind of a person from Carl Sagan. I have zero interest or abilities for communicating. My interest is in the sciences and trying to understand how everything works. I always give as an example Benjamin Franklin. He made suggestions for possible climate impacts of volcanoes. We actually now have a lot more potential for trying to understand those things because we can make these models and because we have global observations and things. That is what I really like to do. But nevertheless, obviously you want to try to communicate a significant issue to the public. I remember shortly after that someone recommended to the editor of Science that I write an article on the clouds of Venus, because I had written some papers about the physical properties of the clouds of Venus. And you know, I couldnít do it. I wrote the title, ďThe Veil of VenusĒ. I thought thatís a great title, and I wanted to write an article that could be understood. By a broader audience, at least other scientists. Thatís very hard to do. Of course I was busy doing other papers. I never did finish that paper. Then after I got off of Venus and into this climate problem, then I started working on a paper intended for Science on CO2 and climate change, which was eventually published in Science in 1981.1 That was the paper that was reported on the front page of the New York Times by Walter Sullivan.2
Weart:Right. I want to go over that in some detail. How come you started working on that? So you saw it as a paper for Science and you intended it to reach a broad audience?
Hansen:Yes. The topic in the 1970s was becoming of greater interest. I had written one or two papers in Science. One, in which the calculations were done by other people here. Wei-Chung Wang was the first author, a 1976 paper on trace gases.3 But basically, I wrote the paper. And then there was one on Mt. Agung, which was a test of the planetary response to a global climate forcing. The model solution. It was also sent to Science.4 If you wanted your work to get wide distribution in the community, itís a good place to publish in these general journals.
Weart:From these other papers, have you had reporters calling you up or had any interaction?
Hansen:Well not very much if there was any.
Weart:Do you remember when you first met Walter Sullivan?
Hansen:Well, yes. Across the street at the Moon Palace.
Weart:A Chinese restaurant?
Hansen:Yes, that was Dr. Jastrowís (director of GISS) favorite place for lunch. He was particularly interested in communicating with the public and interacting with the media, and in a sense was kind of a rival of Carl Sagan. Eclipsed by Carl Sagan. He must have invited Walter Sullivan for lunch to talk to about something. I believe that I went to lunch with them because of our Venus thing. We had this experiment, which I proposed for a Venus space mission, which was accepted. So therefore I went with them to the luncheon and we talked about that a little bit, but then once the paper was finally accepted—
Weart:The 1981 paper, which you wrote with a second author, I guess Lacis.
Hansen:Andy Lacis, yes and other co-authors. But a few days before it came out I sent a copy to Walter [Sullivan], and that was sort of my original sin. [laughs]
Weart:That was the first time youíd done something like that.
Hansen:Yes. Now itís normal for organizations to send out press releases or something, but this was just something on my own.
Weart:You knew it was a matter of public interest.
Hansen:Yes. And that paper, I had submitted that to publication. I had been working on it for a couple of years Ė I sent it twice to Science and once to Nature and all these time, it got sent back.
Weart:Why was that?
Hansen:It was too long. They said, ďWell the topic is of interest, butÖĒ It was like three or four times what they said their limit was. Now I know that theyíre—
Weart:They didnít object to the technical content.
Hansen:Right. Maybe the first time or two Iím not sure it got to the referees, but they kept it for some time. The editor was interested in the topic, although heís always somewhat of a disbeliever Ė Phil Abelson. He was always, I donít know, skeptical.
Weart:But I think the people who argue against global warming would say that Science and Nature gives propaganda for [their opponents]. Maybe thatís more recently.
Hansen:I would actually agree with them. And my trouble with Nature now is that itís got an editorial position, thatís for sure. Abelson, you know, writes about energy all the time. I sense some skepticism on his part, but I think itís healthy skepticism. But he certainly didnít try to stop publication of that sort of paper. He just objected to the great length of the paper. I sent it to Science twice and I sent it to Nature and it got rejected. And again they said, ďYes we like this paper, but youíve got to cut it in half.Ē Each time I rewrote it I would cut it about 10% or 15% or something and then send it back. And I still had to cut out figures that I really liked.
Weart:Do you have a copy of the original paper, the longer one?
Hansen:Yes, I think I probably do. For example, it had a bar graph with the amount of CO2 that you could get out of oil and out of gas resources and out of coal. Of course coal is 10 times bigger. Some people still donít realize, you canít double CO2 with just oil and gas. Itís not even available.
Weart:I see. So your original paper took a considerably broader view of all that.
Hansen:Well, I it was still mainly the things that were in the published paper; just additional graphs and some things had more details about how each forcing contributed, how well the model fitted the observed temperature data and things. In fact the numbers for coal and oil and gas were still included in a little table instead of a bar graph.
Weart:You sent it to Sullivan and then what happened?
Hansen:Then it got this publicity, as it was reported on the front page of the New York Times and discussed in the Washington Post and New York Times editorials, which did us no good with the Department of Energy, obviously.
Weart:Did you hear directly from them about that?
Hansen:Well it was more than that. They had a workshop in which principle point seemed to be to dispute the severity of the issue or the degree to which we could actually tell. In that paper, it did try to say things in an interesting way. For example, the potential Ė opening of the Northwest Passage Ė to try to make it get attention. So then the chief scientist for the DOE program actually wrote a criticism that was published as a letter to the editor in Science. This is the perfect example when you talk of the response of the scientific community and the political side of it, if you look at the article by Walter Sullivan. [Ask] a colleague of mine, wouldnít call him bosom buddy, but he was a student when I was a post-doc Ė thatís Steve Schneider. Weíre pretty friendly, and Iíd say now in our old age weíre quite friendly. He sort of criticized the paper when Walter Sullivan called him for comments. But Walter Sullivan said, ďBut these caveats were actually inĒ our paper. I thought we had the caveats okay. But the person who really got most upset was the person who got me my job, and thatís Ichtiaque Rasool. He submitted something to Science, which was really a fairly personal attack in a sense, and it kept getting rejected. Eventually it was published, actually it was published by Steve Schneider in Climate Change. I then responded to that and claimed that, you know, as scientists we did our best to present an unbiased projection.5 What he accuses us of is trying to get funded, trying to use this to get an increase in our funding.
Weart:Well thatís been a story for a long time, but climate scientists make a fuss so they can get more money for their research. But in terms of an official response, this is just now the DOE thing.
Hansen:Oh, itís in the DOE thing.
Weart:The DOE had been reorganized already by this point.
Weart:By the way, were you involved in any of the politicking issues of the late Ď70s about the DOE budgetís standing? Were you involved in any of that?
Hansen:I wasnít, but then when NASA said they werenít going to continue to fund our CO2 climate research, then David Slade said that they would pick up, the funding for that. And that was what paid forÖ
Weart:Thatís what paid for this paper?
Hansen:No, I never got DOE funding. In about 1977 or so I got a three year grant from NASA, and that was what supported this. Then NASA indicated that they werenít going to renew that and David Slade said that the DOE would pick it up. But then he was replaced by Fred Koomanoff. Then we went down and gave a presentation to Fred Koomanoff. But even prior to that presentation they had had this workshop near Washington with Mike McCracken, who is the guy who wrote this letter to Science criticizing our paper. And again heís a guy that I know fairly well. Heís now the head of the U.S. Global Climate Change Research Program, something like that. Although he had to understand itís really reasonable science, but still, heís not willing to recommend it to DOE for funding.
Weart:Do you have any of the correspondence from those days? Because I want to ask you about if you saved any of these letters.
Hansen:I may have a few things. Actually for a different reason last night I started to look through some of my notebooks at home. I do have some clippings, the press things, which I didnít do too good a job of saving between í81 and í88. [Looks through papers in office].
Weart:Itís good you saved something itís impossible [for historians] to find out otherwise.
Hansen:[Looking at files] Yes, so this was starting with Walter Sullivanís thing. Editorials in The Times and in the Washington Post. But as for letters. Iím still in the middle. Iím still a government employee. The one thing which had bothered me in 1980s or so is an issue of whether my being blunt about things impacts the other people at the Institute. Basically I felt, while in some ways it made it harder for me to get funding, but sometimes then there was Ė I donít know if it was guilt or something on their part Ė maybe some other people at the Institute I felt actually had a better chance of getting funding for individual grants, as a preferable alternative to me. But still, as far as our getting institutional support in computers or something, it certainly doesnít help. Unfortunately I think I do not serve as a good example which would encourage people to be too outspoken because it seems that I donít make anybody happy. From my prejudiced opinion, I believe that I try to be objective in what I claim. Now it may be that Iím just not very effective at explaining and at communicating with program managers.
Weart:But on the other hand, you havenít been identified as on this side or that side.
Hansen:Right, but if you want funding you almost have to be. Thatís one possible interpretation. I really donít want to get into details, but either political party feels that government scientists are working for them. If theyíre in power they want you to be supportive of their perspective. That type of thing. And therefore it seems I never make anybody happy. You would think in the ideal world that if you just say, ďOkay, Iím just going to try to do very objective work and understand these sciences as well as I can,Ē you would think you should be able to get support for that. But itís not necessarily so.
Weart:Especially as a government scientist.
Hansen:Yes. Itís probably not appropriate to blame any of the people in power, but thereís a lot of people in between the scientist and the people in the highest levels of power. And those people in between are trying to do what they think will please the highest levels. And theyíre the ones who you actually get the funding from.
Weart:This brings us to the next thing I want to ask you about, which is you were requested to testify before Congress. How did that come about?
Hansen:Thatís a good example, because that came about simply because of the fact that weíd been in the newspaper, not only once but sort of three times. When I testified the first time in early 1982, I had three different graphs, one for each paper. One I think was the Science CO2 paper. One was a sea level calculation we attempted Ė Sergej Lebedeff and Vivian Gornitz and I were trying to do with sea level calculations, sort of what we did with temperature.6 Instead of having temperatures at meteorological stations we had sea level observations at different tide gauge stations. We said, well, letís use the same averaging method that we used for averaging together these meteorological stations. Itís a little trickier because the relative sea level of any place also depends on crustal motion. But anyway, we calculated that sea level had gone up 12 or 15 centimeters in a hundred years. I suggested that we also calculate the thermal expansion of the ocean water. That seemed perhaps to explain part of the sea level rise.
Weart:Was that done before?
Hansen:I donít think so. I think that our paper was the first one to do that, as far as I know.
Weart:Seems like an obvious thing after itís done.
Hansen:Yes, and it is kind of small, but itís a few centimeters. So that was the second thing, and then the third one was we did a trace gas paper where we showed that in the previous decade other trace gases had become significant, in fact, their net forcing equaled that of CO2. So because of that exposure, I was called by the people organizing that hearing. I donít think it had anything to do with our funding. But the hearing was an attempt to stop DOE from terminating this kind of research. Specifically at that time I knew I was having this problem with funding, so I went and talked with the staff person organizing the hearing, I believe his name was Jenson.
Weart:Did he call you?
Hansen:Well, Iím not sure, think probably the contact with them came about via Rafe Pomeranz. Iím not certain about that. I donít know how they knew, how they invited me. It couldíve been directly from Janson calling me or it may have been Rafe Pomeranz. Because I know Rafe Pomeranz had come up to talk with us about the problem.
Weart:That was the first time?
Hansen:Yes. Iím not certain of the date the first time they called and invited me up there, but I believe it was after the workshop. So he may have been an intermediary. But in any case I went to Janson after the hearing and said I thought we were in danger of losing our funding, and I didnít think DOE would look favorably on our proposal because they didnít like the exposure of the issue. And he said, ďWhy donít you give the proposal to me and we will forward thatĒ or something. They would indicate they had some interest in it. I ended up deciding not to do that.
Hansen:Because I just feel that you may get a temporary success in funding by trying to do it through a political route, but I just didnít think it would work in the long run.
Weart:Actually since then pork barrel science has become common.
Hansen:Yes. He wasnít necessarily saying that it would be pork barrel, but rather that they would try to make sure that it got a fair hearing. Not that it would go through a different route than other proposals. I mean not that it would have a different funding source. Anyway, we did get zero out of that.
Weart:Then you did several other proposals hearings. Iím just curious about during the Ď80s, you appeared several times. I wondered if you had any direct contacts with Al Gore, Chaffee, George Brown, James Scheuer, or was it mostly with the staff?
Hansen:It included direct conversations with staffers, but more often the contact was more with people like Rafe Pomeranz.
Weart:So you didnít sit down with Gore or George Brown or ?
Hansen:Well, Iíve had several meetings with Gore subsequently, not prior to the í82 hearings.
Weart:Iím referring to the period í82 to í88.
Hansen:No. There were a few times when I talked with Gore, two round tables in his office, but those were probably both in 1989. There were other cases where I went to meetings with him. He came here to the Cathedral with Carl Sagan, trying to get religious leaders. I met him there and also there was a second meeting with religious leaders in Washington and I saw him. I think between í81 and í88 I did testify at two or three Senate Hearings. [Looking through papers] There was one in í86 and one in í87. And I notice the one in í87 was in November, The Senate Committee on Energy and Natural Resources. That one I actually prepared my testimony.
Weart:And you think it was í87 that you prepared this article for the testimony?
Hansen:Yes. This thing was reprinted from the proceedings of the first North American Conference on Preparing for Climate Changes.7 Actually, I just noticed this morning in looking at that, but that is sort of I already was making the figures for our 1988 paper. It wasnít quite the final form on that, but this was one of them. It even had the maps that I showed in 1988 testimony. This was a November hearing. I remember after this hearing talking with Rafe Pomeranz and the person for the Senate committee say, what we really need to do is hold it in the summers.
Weart:Before we get to that, you had a preparation for that I suppose. Did you write papers with an ye towards testimony?
Hansen:Again it goes back to the fact that itís really interesting to look at a series of numbers. In 1977 or '78, approximately I started trying to use these meteorological station measurements to average over the earth to get a temperature curve. I started first with this student, Jeremy Barbera. I had to program these. So I had the notion that wow, one station could really give you information for a region. You could tell that just by comparing the different station records and seeing how well they correlated. We showed in one of our first papers that thereís a high correlations out to distances of the order of a thousand kilometers between stations. So therefore we claimed that you could even say something about the Southern Hemisphere. The previous papers by Murray Mitchell, probably the best person, were just for the Northern Hemisphere. In fact he even left off the equatorial latitude just did 20 degrees north to the pole. Itís somewhat different for the Southern Hemisphere. So in the late 1970s we were trying to put together that series of numbers and noting temperature, it still wasnít quite as warm as it was, but important to know what was going on. Then in our paper, which was finally published in í81, weíre speculating and arguing that roughly despite these ups and downs, it looked roughly like the CO2 would be, in effect, a driver of this warming trend. It also should become clearer in a fairly reasonable time period. So it was very interesting to keep adding on a new year, year by year
Weart:Once you got started it was hard to stop.
Weart:Now the í87 paper you mention the urban effect.
Hansen:Thatís still an interesting thing there. Iím writing a paper right now, in which we use satellite observations of night lights taken from this defense meteorological satellite which has this photo multiplier tube which is very sensitive. On the nights when thereís no moonlight, then we look at the lights, so we donít even have reflective moonlight, and we can see very well where people live and where they donít. We use that to identify unlit areas, to identify where the stations are free of influence. We find that even the small towns there is some urban, human influence. But the issue there is of the order of a tenth of a degree on global average.
Hansen:In our í87 paper, which was the first time weíd talked about that, we did remove the large cities and that did make some difference. The best estimate of urban influence is probably somewhat smaller than the indication we were getting.
Hansen:Youíre trying to make sure youíre not fooling yourself. Right.
Hansen:In fact people, Murray Mitchell and some other climatologist had pointed out that urban warming was quite large in some places.
Weart:So come 1988, even in the í87 testimony you were already preparing for this.
Hansen:As you just said, I donít think what we were saying was that different in í88 than in the previous testimonies. Itís a little clearer than it was before, if you go all the way back to í81 for comparison. At that time temperatures had not yet passed [previous highs]. In our í81 paper we only had data through í78. Only in the 1980s did we start collecting the data in near-real-time. But by 1988 it was becoming clearer that the Earth was getting warmer, after several additional years of data. And I would say the models were more realistic, because in í81 we just used the one-dimensional radiative-convective model. In the Ď80s we had a three-dimensional GCM and were able to do these kind of simulations at least for a global mean, even though you canít do the regions with that model very well. At least we had more confidence I think in the simulations.
Weart:So it sort of passed the critical point in í88, or it was better organized in a sense. I think somebody figured out recently that that is still the hottest summers on record in Washington.
Hansen:Yes. It was convenient. The day before, either one or two days before the testimony I called Rafe Pomerance and sent him my official testimony. He either told me— I donít know if he arranged it or he just told me, but he said that there would be television network coverage.
Weart:[Inaudible]. Did reporters come at you a lot after that? A lot of phone calls?
Hansen:Oh, yes. Both í88 and í89 there was a lot.
Hansen:Yes. In that case I did the job. Frankly looking at these old things in my clippings, [inaudible]. [Looking through papers] I saw in one of these, oh yeah, I have a whole stack of 50 messages, 10 or 12 of them asking me to go on TV. Iím not going to do any of them.
Weart:Youíre not a TV personality. Thatís not your business.
Hansen:Then there really was a problem. The politicians in power were very upset, Iím told. Fortunately I was protected by John Heinz. I actually got a call Ė the Senator from Pennsylvania. Of several people Iíve met, he was the most impressive. He was very objective. He must have been a Republican, but he was certain he was an environmentalist. He organized a public discussion of this topic. He asked me to talk. At first his staff had sent me an invitation, which I had declined. Then he called me at home, and he said he had spoken with John Sununu in my defense. Actually he sent me a letter, discussing his discussion. So he did spend quite some time on this. Itís obviously that the letter could not have been written by his staff.
Weart:Do you have the letter?
Weart:Iím not saying I need to see it. Because one of our jobs, you know, at the History Center is not just to tape record interviews, but talk about preservation of papers.
Hansen:Yes. I have notebooks, which are chronological, but the letters and things to the extent I have them, are put away in some folders and not very well organized. [Looking at papers]
Weart:So theyíre not at home?
Hansen:Well, yes these things are in my file here, but most of the political things I put them in the file at home.
Weart:[Inaudible]. You never had any interaction with yourself with Ė
Hansen:No. Again, one of these clippings I noticed it has Sununuís photo and my photo.
Weart:But not in the same room
Hansen:But theyíre separate photos. [Reading a letter:] ďThe Honorable John Sununu. Dear John. In light of our conversation, I reviewed Dr. Hansenís proposed testimony in detail. Below Iíve made three observations and then follow the suggestion...Ē
Weart:This is 1989.
Hansen:This is May of 1989. So we include these changes in testimony, and so heís computing they cost a lot. Then OMB added a disclaimer, which in fact it was a closer call for [inaudible]. ďHansen did ask that OMB not change his [inaudible] testimony...Ē. See I never—
Weart:Itís an interesting case. Thatís been covered [in other published articles.] Letís backup from that for a minute. Iím curious about some of the other personal interactions. You mentioned that during this period, you knew Schneider [inaudible].
Hansen:Yes. There was a good article on that, which I think let me described ďstruggling to do science for societyĒ.8 It described Steve Schneider as a preacher. And they described me as a witness. Someone who believes he has information that is important. So, Hansen as ďa witness, Schneider as more of a preacherĒ.
Weart:Youíve known Schneider from way back, you said?
Weart:In what sense? Did you run into him at meetings?
Hansen:No, no. He was a student. He actually got his degree in engineering, but he got introduced to this topic by Ichtiaque Rasool, who was the guy who was later attacking me. The guy who got me my job and was attacking me, referring to our earlier situation. So Ichtiaque got Steve to work as a post-doc under him, I believe it was just after Steve graduated from Columbia. They wrote a paper on the effect of aerosols on climate, and ended up saying that the Earth may be headed towards the next Ice Age.9 I actually helped Steve with his calculations because he was not really a radiation transfer person, so I gave him equations for the scattering the solar part of the problem. He did the thermal part of the problem, and actually, he did a kind of slightly sticky CO2 calculation. He understated the greenhouse effect by a factor of two or so. We later figured out looking at his computer program that it was his mistake.
Weart:Iím curious. What was it?
Hansen:Just his calculation of the infrared opacity of the greenhouse gas greenhouse gas, CO2, was wrong.
Weart:Problem with the data?
Hansen:Youíd have to ask Andy. I donít remember the details. Andy Lacis, heíll probably remember. What was the point? Oh, Steve Schneider. He and I went with my wife, climbing on Storm King Mountain. So we were pretty good friends.
Weart:Mountain climbing or night [building] climbers?
Hansen:No, no, no. I spent my time mostly in science. But we did hike at Storm King Mountain so he knew about these things. We also went out once or twice to dinner and went ice skating with him in Colorado after he moved to NCAR, and such.
Hansen:I always found him, you know— he prefers to talk all the time and I prefer to do the science. So he would come stand at the doorway, and I would try to continue to do what I was doing. Sort of saying, ďGo away, Steve.Ē It was hard to get him to take the hint. But we were always friendly.
Weart:[Inaudible]. What about, did you have any personal interactions with some of your critics? People like Idso? Did you have any personal relations like that?
Hansen:Again, no. No, not personal, but I did respond to him. One of the articles that I just gave you was an Idso criticism, published in Science and I responded to that.
Weart:But this is entirely in the published literature.
Weart:Not standing up in meetings and arguing back and forth.
Hansen:No. I feel that I can do a fairer job in the written scientific interchange, but I would not have had the confidence to a public debate. Iím not a debater.
Weart:So you donít go to conferences and stand up and argue?
Hansen:No, I donít do that. Only in the last couple of years I did accept a few invitations to debate. Itís hard to chicken out when you get these invitations from someone like Frank Press. So I did officially debate Lindzen once, that sort of thing. Itís available on the web. Then one with Pat Michaels which is being published, itís about to come out.
Weart:Letís get back to the science. First, Pinatubo. [Inaudible].
Hansen:We had claimed after Agung, much after, and finally wrote a paper for Science that volcanoes would be a nice test of climate.10 A big volcano would provide a test of our understanding of climate response to a forcing. And a volcano came along, it was El ChichÚn. We resisted the temptation explicitly to jump on that. I thought I would, but the model wasnít ready.
Weart:So you already had in mind that you would do it as a prediction?
Hansen:Yes. You really like to do it about the time the volcano goes off rather than later. Our global climate model was not finally published until 1983. It took so long. Partly because we were so slow; partly because we were using coarse resolution in the model so we had a hard time with the publishers and referees. It was published in 1983, so by that time we were a couple years beyond a volcano. Also there was no SAGE up at the time of El ChichÚn. There was at the time of Pinatubo.
Weart:SAGE is what?
Hansen:Stratospheric Aerosol and Gas Experiment. It was a Langley experiment. So right after Pinatubo went off, shortly thereafter there was this meeting at NASA headquarters with observers and modelers. So we were able to get a pretty good estimate about how big the optical depth was for Pinatubo, so that was a great chance to predict before instead of after.
Hansen:It was pretty well received. We have so few examples, even though it is not really a test of decadal sensitivity. But still itís useful. It even provided some check of the magnitude of the forcing, because the ERBE [Earth Radiation Budget] measurements did claim that they could detect a change in the radiation balance of the planet. It was a couple of watts and is really at the margin of error to measure that. I think the forcing was probably more like three watts than two watts. But in any case, there was a planetary radiation imbalance. The temperature response of the system was what we had calculated with respect to the forcings. It was a simple check. A single volcano is only comparable to natural variability. If you integrate it over the whole planet, then some things like the stratosphere temperature was way above the noise level. And the global average tropospheric temperature change is somewhat above the noise level.
Weart:[Inaudible]. What relations have you had with the IPCC? [Inaudible].
Hansen:Iíd pretty much keep at arms length. I have been involved, because they need data from different things, whether itís our Pinatubo calculations or our temperature record or as one model result. Sometimes we just respond to their request and sometimes I might have been a contributing author. But Iíve never gotten heavily involved in that activity. In fact, predecessor document of the panel I thought was fundamentally flawed. This is prior to IPCC. And then in the middle 1980s there was a document which Ö This was a little earlier. This was before it was international in a major way. There was this carbon dioxide assessment.11 They concluded the climate sensitivity had to be at the low end of the range of climate models. But I claim that there was a mistake with their analysis. And that mistake—
Weart:Weíre looking now at ďClimate response timesĒ, itís 1985.12
Weart:Hansen, Russell, Lacis.
Hansen:Right. So the point of this paper, a major point was to point out that climate response time is a function of climate sensitivity. And in their big document Ė it was really supported by the Department of EnergyĖ
Weart:Yes, it was the U.S. Government... The Academy.
Hansen:Yes. It says the National Academy of Sciences, but nevertheless the key part in that was a piece by Mike McCracken. He assumed that the response time was 15, years independent of climate sensitivity. What we showed was that the response time goes like the square of climate sensitivity. So if climate sensitivity is three or four degrees then the response time is 100 years not 15 years. Then you get a very different conclusion. Thatís the kind of thing where you get a huge group putting something together, and pieces of it will depend on whatís done by one or two people. How can you track down all this? I claim exactly the same thing is going on now with—
Weart:Current IPCC [report].
Hansen:Yes. Right. They become huge. The whole stack now is not even one volume. Itís got to be in several volumes. The CO2 thing is opaque. Theyíve come to this conclusion that even if you do the Kyoto Protocol reductions in CO2 emissions it makes very little difference in the next 100 years. If you look at the CO2 growth rates, they come out with very large growth rates. But the factors that go into that, certain assumptions that go in, I just think theyíre very far off from reality. One way you can prove that is again going back and looking year by year at whatís really happening. Now youíve got 10 years of IPCC since the first document. And if you look at the rates of change over that period with some of their models, youíll see that theyíre way off.
Weart:In what direction?
Hansen:In the direction, the forcing that theyíre putting in is much larger than what is really happening. An extreme example is methane, they were off by a factor of three.
Weart:Factor of three, really?
Hansen:Yes. Even the actual CO2 growth rate falls near the lowest scenario. They have a range of different scenarios, but the observed data falls near the lowest scenario.
Weart:Why do you suppose that is? Are they trying to be pessimistic?
Hansen:Well certainly at present their scenarios are pessimistic. Back in the 1980s we would include a scenario which was assuming continued exponential growth rates for greenhouse gas emission, and that had actually been true for a number of decades. From í45 to the middle 1970s. Itís useful to warn people that if we continue to follow that kind curve, it will have very dramatic consequences. But we shouldnít only look at that scenario. We should also look at others which are also plausible. But itís impossible to influence this thing. Sure, you could go to these meetings and say something.
Weart:Thousands of people.
Hansen:Yes. And it certainly becomes somewhat political. Certainly the CDAC thing was driven by a more political thing. The CO2 assessment in the early 1980s, there was too much politics behind that, and thereís politics behind the present IPCC. I just want to do objective science.
Weart:Okay. Let me back off from that idea. Thereís one more paper that I wanted to ask you about, and thatís this one in the late Ď90s of trying to evaluate the aerosol absorption and so on that you worked on.13 Itís a little too recent for me to understand the struggle thatís going on here.
Hansen:Well, the aerosols are not a new story, as we said. That goes back not only to Steve Schneider and Ichtiaque Rasool, but it goes back to Benjamin Franklin. So itís nothing new, but earlier we could kind of get away with sort of ignoring it. You might be overestimating the forcing, because the aerosol contribution was negative. But until youíre starting to try to fit things in more detail. See, in our 1981 paper I thought, well, aerosols probably provide some cooling, but on the other hand weíre leaving out these other trace gases, so thereís some cancellation of error in there. So we kind of focused on CO2. Even our best estimates, at IPCC or our recent papers, are that probably aerosolsí direct and indirect effects are perhaps half as large as the total greenhouse forcing. And the total greenhouse forcing is about 50% CO2 and 50% all the other things. So aerosols are probably significant compared to greenhouse gasesĖ but not dominating over the long term scale. But as you try to do the problem carefully, youíve got to include those. Charlson and others began to make an issue of sulfates in about 1990 or so. I was even co-author on a paper with him, which he wanted to be in Science to catch attention.14 And he had a press conference and everything. But the disagreement that we kept having was that I said, ďYouíve got to put in a realistic single-scattered albedo from aerosols.Ē Now sulfates are perfectly white and their single-scattered albedo was one. Of course theyíre not pure. If you look at real aerosols, if you measure aerosols in the atmosphere, anthropogenic aerosols, youíll find that single-scatter albedo is less than one, because itís not pure sulfate. Most important, some is black carbon. The same processes that produce sulfate, fossil fuel burning, also produce black carbon. So our approach to that was, well, Iím just going to put in a single-scatter albedo based on observations. And then you get very different evaluation of the importance of the aerosols, but it is important to try to understand the constituents of that. The impact of the aerosol thing was that IPCC had to include these [error] bars for the forcing by but then they had to include the aerosols going into the future. At that point you could say, and Iím going to be a little bit unfair, that using aerosols as a fudge factor allowed them to explain what had happened in the past century. Now the current IPCC are going to remove the aerosols from the future because (to take a critical view) they didnít want their projected warming to come down. So theyíre now taking aerosols out of the future, so that way it still looks like weíre on the verge of disaster. But Iím being a little unfair, because I think itís not too bad an assumption to say that aerosols probably wonít get to be much more extensive in the future than they are now.
Hansen:Right. But to understand that problem and to get to have a reasonable policy you need to understand that there are different aerosols. Black carbon is probably a lot easier to control. Tica Novayov claims that the black carbon in the US has actually declined by a factor of three because these used to be coal burning on small scales. Itís not so much the big aerosols that fall out very quickly and might be the ones that you see. The important ones are the smaller ones that are long-lived in the troposphere.
Weart:And all this is based on fairly recent measurements? [Inaudible].
Hansen:Yes. And my big complaint at the moment is that weíre still not measuring aerosols, well enough to really know. This is speculation. As I say, Tica Novokov argues this, but we donít have measurements to say. We donít even know whether the aerosol forcing is increasing now or decreasing.
Weart:I wondered if maybe we could go back to the 1960s, [you asked for measurements]. . Why do you suppose it hasnít been done?
Hansen:Well I know a specific reason. This is a very prejudiced opinion. I also think itís a correct one, but anyway. We proposed an instrument, that was accepted to be on the first EOS platform, to measure aerosols. We didnít know microphysics of aerosols. Measuring full spectrum, all angles, and all the polarizations, so you could really infer not only the size distribution of the aerosols, but also the reflective index, which is composition specific information. We also proposed, and were encouraged by Al Gore and others, to do small satellite measurements of aerosols and other things. But that was not well received by the EOS program, which preferred large multibillion dollar satellites. Our experiment got thrown off of EOS. Weíre still trying to get these measurements done. As I say, itís important to know how absorbing aerosols are changing. Itís probably possible to reduce the aerosol emissions in fossil fuel burning, particularly as more and more of the fossil fuel burning is done at high temperatures in efficient power plants. You can really scrub emissions in that case. And even in vehicles itís certainly possible. But climate is just part of the aerosol problem. The other aspect is human health. These fine particles, not the big ones that fall out quickly, they can penetrate human tissue very effectively. They cause increases in asthma and all sorts of respiratory and cardiac problems.
Weart:If you look back over the last 20 years, how do you think climate science has changed?
Hansen:Iím afraid that itís changing in the sense of more emphasis on models, which I think is a mistake. You know, back in the time of Jule Charney, back in the 1970s, he was really a very thoughtful guy and he was a great person, a prime user of models. He in a sense was the father of the use of satellite information to improve the weather forecast. But still he focused on the physical mechanisms of the climate problem. Yu need complex models for that which allow you to analyze many different processes and how they interact, but you donít necessarily need the biggest, finest-grained GCM.
Hansen:Yes, thatís right. But thatís a hard argument to make. They have good reasons. Theyíll say weíve got to resolve the case of the ocean in particular. But I think my point would be, you have to choose where you use your resources. I argue that for getting the processes, vertical resolutions is more important than the finest-grained resolution.
Weart:Have there been changes in size, specialization, relationships?
Hansen:Yes, I think thereís been a progress in getting interactions with different communities. Social sciences are not that much integrated in the process. The degree to which they have gotten involved is perhaps about right. Some things havenít changed, thatís the problem. Thereís still not enough separation of science and the politics; thatís a sure thing.
Weart:[Inaudible]. [Inaudible section]
Hansen:We always have an escape valve as more and more of our energy is used for electrical power. If it turns out that the climate impacts are going to be too large to ac, even if we are burning coal at the power plants, the capture of the CO2 and sequestration is a plausible thing. And it may be cheaper than other sources of energy because coal is so cheap. Even with that added burden, it may be cheaper.
Weart:Okay. Finally, in getting back to this question of paper. We have here your administrative records of GISS, I suppose.
Weart:I suppose theyíre officially government records. Have you ever considered the National Archives for them?
Hansen:This is really a very small organization, like 20 civil servants now, which is the largest itís been since Iíve been there. And most of my things are really theirs. I donít even have an effective secretary. Thereís one secretary for this organization, we now actually have her on the sixth floor. So Iím sort of my own secretary.
Weart:Nobody at NASA has ever discussed the records. NASA by the way has a poor program for preserving records.
Weart:Let me just ask you to bear in mind that at some point The National Archives may be interested. [Papers might be offered to them when you retire.]
Hansen:Yes. At some point I will sort out my records.
Weart:And you have some personal materials at home, which should be preserved somewhere [for example Columbia University archives].
Hansen:Yes, I have [inaudible].
Weart:Another question. This is something that weíre studying possibly. What happens to your e-mail?
Hansen:The organization, you know, Iím doing it myself. And now itís reasonably well-organized.
Weart:Do you keep all your old e-mail on a disk somewhere?
Hansen:Yes, itís on the computer.
Weart:[Inaudible]. Okay. Anything else we should talk about?
Session I | Session II