Russ Roberts

John Christy and Kerry Emanuel on Climate Change

EconTalk Episode with John Christy and Kerry Emanuel
Hosted by Russ Roberts
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John Christy of the University of Alabama in Huntsville and Kerry Emanuel of the Massachusetts Institute of Technology talk with EconTalk host Russ Roberts about climate change. Topics discussed include what we know and don't know about global warming, trends in extreme weather such as hurricanes, rising sea level, the likely change in temperature in the next hundred years. Both scientists also give their perspective on what policies might be put in place to reduce risk from climate change. This episode was recorded before a live audience at the College of Business Administration at the University of Alabama in Huntsville.

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0:33Intro. [Recording date: March 3, 2014.] Russ: Welcome to a special edition of EconTalk, recorded live at the College of Business Administration at the U. of Alabama in Huntsville.... Our topic for today is climate change, and I'll be moderating a conversation in front of a live audience between two scientists with different perspectives on the issue. Climate change reminds me a lot of macroeconomics. We have a complex system, many causal factors, and we're often interested in the impact of one key variable. In macro, it might be fiscal policy or monetary policy or a change in taxes. With the climate, we are interested in temperature or how rainfall or hurricanes respond to human activity, and in particular increases in carbon dioxide in the atmosphere. In both the climate, and the economy, there are experts on both sides of the issue. We are highly confident they understand how these complex systems work. Everyday citizens--those of us who are not experts--we struggle with finding out where the truth lies. How do we evaluate which expert is credible? Who can we trust? Is that the wrong model? Is it possible for anyone to figure out where the truth lies? And what I'm interested in discovering today is where there is agreement, where there is disagreement, and why does disagreement persist in this very important area of public policy and science. Now, to introduce our guests. John Christy is.... Kerry Emanuel is....
2:43Russ: We're going to start with each guest making a brief statement, one to two minutes, about what we know and don't know about the climate, to get us started. John Christy, go ahead. GuestC: Thank you, and it's a delight to welcome both of you here at the U. of Alabama in Huntsville. Ultimately the question before us is a moral question, not a scientific question. Is it good to enhance and [?] human life. Today and for the foreseeable future, the reliable energy that enhances human life and which is economically viable comes from burning carbon. That will continue no matter what our country decides to do. Does extra CO_2 cause climate problems? The observations tell us not much is happening to the climate that hasn't happened before. Now, a fundamental aspect about the scientific method is that when we understand a system, we can predict its behavior. That has not happened for our climate system. It is true that we have an expensive climate modeling industry that shows scary changes. But they are unable to replicate the actual climate system today. In fact, 100% of the latest climate models overshoot the key target variable of climate change detection. And there is no model that has been rigorously validated for reliability. We are not bad people for burning carbon. Indeed, from my experience from living in Africa, I can say with conviction that we are good people, because of the immeasurable enhancement to human life that carbon now provides.
4:18Russ: Kerry Emanuel, what is your view, what we know and don't know? GuestE: Well, thank you for inviting me here. It's delightful to be with you all this evening. In the middle of the 19th century, the gifted Irish physicist, John Tyndall, made a remarkable discovery using a laboratory apparatus--it was [?]--that is that all of the absorption of infrared radiation that takes place in our atmosphere is done by a tiny amount of gas that makes up less than 1% of the atmosphere. That was quite a shocking revelation at the time. And not long after that, the Swedish chemist, Svante Arrhenius, found out that the climate is heavily regulated by one of the greenhouse gases, carbon dioxide, whose mass represents four ten-thousands of our atmosphere--a tiny trace. And calculated that without that four ten-thousands part of our atmosphere that is carbon dioxide, the earth would be a snowball. We wouldn't be here. We couldn't survive. This is not in dispute, this finding of the scientific community. It was not made with supercomputers. It was made with pencil and paper, and it can be replicated today. If that tiny amount of greenhouse gas is what is making our planet habitable, then there would be no surprise that if we double or triple it, we are taking a risk with the climate system. And that's how it has to be viewed. It's a risk. So, going forward, we are taking a risk. Not with ourselves--not with me. I'm old enough that it doesn't matter. But with future generations. And a rational people deal with a risk rationally. And my whole program is to try to de-tribalize this debate. You know, it's not about this is going to be a climate catastrophe on the one side, or nothing on the other. And it's also not about trying to do something about it--it will be an economic catastrophe on one side or won't have any effect on the other. That's not the way the world works. The world is more complex. We have a set of poorly quantified risks for action, and a set of, maybe, as poorly quantified risks in taking action. That's the problem we have to deal with. And that's what I'm here tonight to talk to you about it.
6:29Russ: So, I want to start us off by talking about the idea of climate models. John, you said that climate models have been poor predictors. I want to get your opinion on that, Kerry, in a second, but before we talk about the quality of these models, Kerry, I wonder if you could start us off by explaining how these models are actually constructed. So, in economics what we do, we have a lot of data, say, about a macroeconomic variable--GDP (Gross Domestic Product) or labor, the amount of unemployment, the number of hours. And we know it's a factor of a lot of different variables, so we try to use very statistical techniques--typically multiple regression analysis, a fancy term--to try to hold other things constant while one thing changes, and look at the impact of that one thing. And the statistical techniques that do that are pretty good. And then there are issues: Have you measured things correctly? Have you controlled accurately for these variables as legitimate, is there correlation going in both directions? Etc. Is that what we do in climate modeling, or is it a little bit different? GuestE: Let me just preface my answer here to your important question by saying that a lot of what we know about the climate system was predicted long before there was such a thing as a climate model. It's a mistake to think that everything we knew about climate or predictions about climate are based on complicated models. Having said that, we have built over the years a hierarchy of increasingly complex models that really are some of the most complicated pieces of software that the human race has ever constructed. They have their origins in models that were built for a much more pedestrian but important purpose, which is weather forecasting. And they are very complex. In the case of weather forecasting, arguably you can test them twice a day and see how well they are doing. With climate, it's much more difficult to test them because we don't have that many climate states. But we do experiments that are much along the lines of what you had just described as done with economic models. We try to hold certain variables constant, like sunlight. And vary another external factor, like carbon dioxide, to see how the system responds. Russ: In the case of economics, what we typically do is we take, say, data up to the present. And then we say, based on the relationship between these variables in the past, here's what's going to happen in the future. Is that the same idea in climate modeling? GuestC: Uh, no, it isn't the same. Because there is a huge difference between climate modeling and economic modeling. We know the equations. You guys don't. Okay? And we actually know the equations we are trying to solve. And the problems come with actually trying to solve them. And arguably our computers aren't nearly powerful enough to really solve them exactly; and they won't be for generations, unless there is some unbelievable breakthrough in computation. So, that philosophy is very different. We are actually solving or trying to solve known equations, for the most part. Russ: So in economics--I don't want to miss a chance to get in my favorite joke in economics, which is: How do you know a macroeconomist? And the answer is because a macroeconomist uses decimal points. And that's clearly an illusion of precision in the case of macroeconomics. Whereas, here, the isn't the precision of the underlying equations. It's: How do the underlying equations interact? Is that a correct way to summarize what the issue is? GuestC: It's a fair way to summarize the issue.
9:53Russ: Let's talk also about--and we are going to get into the implications of these models in a second. Before I do that, one more bit of foundation-laying, which is: John, I'd like you--you talk about how we actually measure the raw variables we want to talk about. Because John has done a lot of work on that here at the U. of Alabama in Huntsville. And I think most of us who are not climate scientists tend to think, Well, there's a thing called 'The Temperature.' But of course the world's a big place. And 'The Temperature', the thing we are trying to explain and measure, is not so straightforward. So, talk a little bit about what--the amount, the level of complexity involved in that is. GuestC: Well, it's quite a bit, I think. Let me first of all say that we don't have a thermometer that can tell us how much warming is due to human effects and how much is due to Mother Nature. We just don't have a thermometer to do that. And so it comes down to, a lot of times, about opinion. About how much is one way or the other. Now, to measure at least what the temperature is doing, the way Roy Spencer and I have done it is through is through the fact microwaves in the atmosphere from atmospheric oxygen, up well and are captured by satellites and the intensity of that radiation is proportional to the temperature of the atmosphere. That's fairly straightforward. And you are talking about measuring the thermometers on the surface--it's a much more murky process because a thermometer is commonly go[?], the instruments change, a lot of places aren't monitored, the setting around the thermometer changes with parking lots or farms or so on. So that's kind of a bit more of a complication there. Russ: Kerry, is there any dispute about the underlying data to be explained? Is there any--how precise is that? GuestE: In science, there is always a dispute about the underlying data. You never get around it, nor should you get around it. Um, however, the surface temperature record for the last 80 years or so was pretty robust. How do we know that? Well, we can take the analyses that are based on the observations, and arbitrarily throw away about 70% of the data--just throw it away, to review the analysis. And we see the same long-term trend. Versus the little wiggles from year to year and decade to decade. It's a pretty robust record. But it is not by any means the sole piece of evidence, observationally, for the fact that the earth is changing. Now.
12:14Russ: So, let's get into that. We'll start with John. John, you have just said in your opening remarks, and you've written recently in the Wall Street Journal, that climate models have consistently over-predicted the amount of warming. Correct? GuestC: Yes. We looked at 100 into the latest simulations. That's all that we were able to download. And in every single case, we saw that the portion of the atmosphere that is most sensitive to greenhouse forcing, in the models at least, over-predicted by at least a factor of 2, what has actually happened in the world of the past 35 years. So we are not talking about just 10 or 15 years. This is over a third of a century that we can see these models are over-projecting what is actually happening on the planet. Russ: Do you agree with that, Kerry? GuestE: Not particularly. I would say--I actually share with John an inherent distrust of complicated models. I don't like them particularly. It's one of the necessary evils. And I want to get back to the point that we base projections, even projections along more than models. Yeah, it depends very much on where you look, when you look, and the time period over which you look. If you look at Svante Arrhenius's prediction about what would happen in 1897 he said that doubling CO_2 would give rise to about 4 degrees Centigrade change in temperature. Russ: Four. GuestE: Four. Today, with all of our supercomputer models we estimate that doubling would result in a temperature increase of between one and a half and four and a half. See, that's not bad for 19th century when you were doing things with paper and pencil. If you look at the temperature records and natural logarithm of CO_2 content over 100 years, it's a spectacular correlation between the two. Is it perfect? No, because there is natural variability. There always will be. And it's poorly quantified. I don't think we understand it very well. I will say that as predicted, most of the heat that you are putting into the system from excess greenhouse gases actually goes in the ocean. It's much more massive and has a higher heat capacity. We haven't been able to measure the ocean nearly as well as the atmosphere until quite recently. But in the last few decades it's very clear that the heat content of the ocean is going up. So we have lots of different, completely independent pieces of evidence, none of which I would argue--here I agree with John--is a smoking gun, but all of which together amounts to a very compelling case that the climate is changing and we're doing it. Russ: Do you agree, John? GuestC: Not exactly. No. I'm not going to argue about the fact that the temperature has risen. Well, here's a news flash: The temperature has always risen, and fallen, in the earth's history. It has been warmer than it is today. It has been cooler than it is today. Without the impact or the influence of mankind. And so, I go back to that other point: We don't have a thermometer that can tell us: this much is due to humans, this much is due to mother nature. And so someone can make the case that it's all due to human effects, or someone can say it's all due to mother nature, because you don't have a way to separate that. I can say from the models, though-- Russ: Kerry, do you agree with that? GuestC: that the hardcore evidence we have, and anyone can repeat this, is that every single one of the models overpredicted what happened over the past 35[?] years. Russ: I want to focus on two issues here. One is the overprediction of the particular--the sophisticated--models, not the back of the envelope. And 2, do you agree with his statement, which I know you don't, that we cannot disentangle any actual increase between human and natural causes. GuestE: Well, let me first say that clearly the climate has always varied. And one of the spectacular successes of climate science is to begin to understand how it's varied in the past. I'm not going to get into it here; we pretty much understand the root cause of the great glacial cycles. There have been roughly ten in the last 3 million years. So, there is something about climate science. But, the fact that it's always changing, right, does not mean we shouldn't be concerned about the change that's going on now. Saying that it's always changed in this context is rather like a defendant in a murder trial saying, yeah, well, people are always dying. Right? It's true, but we're concerned about this change and what it portends for the future. So, I'm afraid I've lost track of the[?]-- Russ: So back to the--the specific question I want to challenge John's claim is that: Well, there's been some warming. And in a minute I'm going to press each of you to talk about how much, because magnitudes matter a great deal, I think, particularly when you get to the policy implications. I think there is a [?] real, genuine consensus from people that the climate is warmer today than it was 40 years ago. And then the crucial question is: how much warmer and why? John says we can't measure why it's warmer, dividing between, disentangling human versus natural causes. I don't think you agree with that. GuestE: I don't agree with that. I agree with that on the 10 or 15 year time scale. I don't agree with that on a 50 year time scale. The fact is that most of the changes we see in climate on these longer time scales are forced, and there are a variety of things that force--it's not just greenhouse gases. There is solar variability. There is cooling of the planet, demonstrably when volcanoes erupt. And there's cooling of the planet that's caused, demonstrably I think, by us, through aerosols and things. The fact of the matter is that solar output, which has been measured very carefully for a few decades has if anything been going down. This warming that we've seen in the last 40 years, I would say with 95% confidence, and 95% of my colleagues agree, has been caused by greenhouse gases building up. Now, is there a chance that John is right and it's not? Or whether regardless of how John feels about it, it's not going? Yes, there is. This is what risk is. If you sit here and say, I need a complete guarantee that we are taking a risk before I do anything, you are not treating this part of risk the same way you treat any other part of risk. If I said to you, I'm going to let my toddler cross the street unless you can guarantee with 98% certainty that that toddler won't get run down, I'm not going to be very comforted. Right? That's the problem we are dealing with. Can I prove absolutely in a court of law? Probably not. But to the satisfaction of 97% of my colleagues, yes. Russ: John? GuestC: That 97% is a canard, I think. That is a very simple question about do humans contribute to climate change at the root, the meaning of that question, which I would agree with. So I'm in the 97%. But like I say, we can't tell why it is warming. But one of the tools that you can use to untangle this is the climate model. And so we can put CO_2, extra CO_2, in the model and see how it warms. Well, using the same amount of CO_2 putting in the model that is actually in the real world turns out to produce, on average, models that are three times warmer than what has actually happened. So my claim is: Whatever is happening in the world, at least the climate models are over-doing it. It's very clear they are. There's no question about that. Because that's what the evidence and the numbers show. And so I don't see, the real prominent things that probably are happening with negative feedback and internal variability--just the way the internal physics of the thing works--can lead to rises and falls in temperature. And so they have happened in the past. And it's hard to convict carbon dioxide of committing a crime if he can look back and say this has happened before and I wasn't there. Russ: What's your answer to that, Kerry? GuestE: Well, I think it's relatively easy, and the fact Svante Arrhenius did it in 1897 without big supercomputers--my students do it after taking a couple of semesters with models they've built themselves. I don't think it's that difficult. But I would agree that internal random variability is there. And the climate would change even if all the forcing agents I talked about before were constant. We're confident of that. We're not terribly confident that we know this noise quantitatively. For example, it might be that if it weren't for carbon dioxide increasing that the climate of the earth would cool, would have cooled over the last 15 years. We don't know that that's not true. These fluctuations occur on top of the forcing. So it's a little bit like, you know, here in Alabama you can have a day at the end of April which is colder than a day at the beginning of April; and you wouldn't conclude from that, that summer isn't coming. Weather, superimposed on the seasonal cycle. I will say that climate models have been wrong in a lot of different regards. And there, John and I agree. Their predictions aren't particularly good. But it's not one-sided. For example, no climate model predicted the demise of summertime marking CIs[?] at the rate it's actually occurring. It's going much faster than the models--any model--predicted. And I'm in the field of hurricanes, and I actually made predictions back in the 1980s about how fast hurricanes would respond to climate change. In at least the Atlantic, they've been responding much faster than I can account for. No, I don't know why. Okay. So, these models aren't particularly good. But all the evidence points to a pretty compelling picture of risk here.
22:05Russ: I want to come back to the economics point. We just passed the 5-year anniversary of the American Reinvestment and Recovery Act--the so-called stimulus package. And proponents of the stimulus package would tell you that it worked. And they'll point to historical examples where stimulus worked. But they won't point to the examples where it didn't work. And they can't predict the impact--they did not accurately predict the impact on [?] unemployment, which is they grossly underestimated the impact on employment. The question is: what do you do about that. You concede that the models are inaccurate, but you don't concede that there is inaccurate in only one direction. Would that be a correct way to summarize that? John, you want to say anything else in response to that? GuestC: I would just say, yeah, none of the models predicted that the Antarctic sea ice would increase, either. GuestE: That's right. GuestC: So that Arctic one needs to be balanced by that. But in terms of this fundamental parameter of the bulk atmospheric temperature, every single model went the wrong direction. Russ: Is that accurate? Do you agree with that? GuestE: Not entirely. I'll tell you why. Because these models are not just run once. They are run many times, to try to account for their own internal random variability. And you can find 15, 20, 25 year stretches in all of these projections where the temperature not only flattens out but it actually goes down a little bit. So, if you take the ensemble mean, then it's correct that the last 30 years, the models have overpredicted the temperature. I might add that 30 years before that, they underpredicted it. And this is what happens when you superimpose natural variability on forced variability.
23:42Russ: So, in your book, you suggest that over the next 100 years--and I'm addressing Kerry now, for those of you listening at home who can't see us up here and can't tell the voices apart as well as you might--you suggest the next 100 years, "if nothing changes"--and of course that's a, it's hard to, you didn't really mean that literally if you said that. It meant if we don't do anything radical to slow down the accumulation of carbon dioxide in the atmosphere--that the temperature would grow by approximately--not by approximately--it would grow in a range of 2.5-9 degrees Fahrenheit. So, the low estimate of the impact would be 2.5 degrees. The high estimate would be 9 degrees. How confident are you of that range? And we'll talk about the implications of it in a sec. But how confident are you of that? GuestE: Well, if you choose the range large enough it's easy to be confident. Russ: More confident. You can get more confident. That's a large range, but it starts with a--the lower end is pretty high. So that's why-- GuestC: Is this Fahrenheit? GuestE: Fahrenheit. Yeah. This is something that any serious climate scientist--and I think the two of us on this stage represent this, in this respect--would immediately tell you, is that we are very uncertain about these projections. Nobody pretends to be certain about it. But there just isn't much certainty in that. To say it's between 2.5 and 9 degrees for a doubling or more of CO_2, Fahrenheit, it's to confess that we don't know. All right? And so what we are dealing with is a problem of the[?] t-curve. Okay? The near end, it doesn't morph, it's 2.5 degrees--we don't have to worry very much, I would argue. And I don't think many of my colleagues would suggest we do. If it's in the middle range, there will be problems. Probably we'll adapt to them. If it's up at the higher end, that could be catastrophic. And the question for me is: Do we do nothing to avoid, even a small risk of catastrophe for our grandchildren? To me, that's the moral question. Russ: We're going to come to that in a second. Maybe a little more than a second. Toward the end I want to talk about what ought to be done, if anything, to cope with this. But I want to get John Christy's reaction to the 2.5-9. It's a modest claim on the surface because it's a large range. It's like when the CBO (Congressional Budget Office) says things about the impact on employment. They are very often vague. Which gives it an unscientific air. It does raise the question of the precision of the estimate. But again, it's a large range. You'd think that would engender confidence. Does it engender confidence in you, John? GuestC: Well, I would go with the very low end part of that range. We have, you know, 35 years period that has a couple of volcanoes that helped tilt the trend a little bit higher. But it is rising at about 2.5 Fahrenheit per century right now. So that's some evidence that that's about the rate it wants to go. Russ: He can't make you more nervous for your grandchildren? GuestC: No, I love my grandchildren. I think I am more nervous about something the government might do that would harm them more than anything the climate might do. Russ: It's a cynical approach. It's a cynical remark that I am of course sympathetic to. But we are going to put my sympathies to the side until we get to the discussion, discussion of policy.
27:15Russ: I want to bring up another issue, in terms of what we know and don't know. What is your feeling, Kerry, about the apparent--and you can challenge the claim if you like--the apparent pause in temperature rise over the last 15 years? Again, as a crude, empirical--a mere social scientist, yes, I confess. When I look at the raw numbers of the temperature nominally over the last 15 years, it looks awfully flat to me. Is that correct? And given that the rise in CO_2 over that period has been the same as before--it's been rather dramatic--how do you explain that and what's your position on it? GuestE: Well, I would be dishonest if I told you I understood that. First of all, just [?], yes. The temperature, the global mean temperature, is pretty flat for 15 years. It was also pretty flat from about 1952 to the 1970s or so. So it's not the first time it's flattened out. And what we're--I don't think the community of scientists is very sure about, is we're seeing a manifestation of internal variability, natural oscillations that happen to be working against the radiatively[?] forced signal at the moment, or whether there is something about the radiative forcing that we haven't understood. For example, my colleague at MIT (Massachusetts Institute of Technology), Citizen Solomon[?], just last week published a paper--I think it was in Science, I don't know if you saw it--suggesting that the fact that we've had a large number of relatively mild volcanic eruptions in the last 10 or 15 years may have put enough aerosol[?] collectively into the atmosphere to affect the temperature. Now I haven't had a chance to digest that. I think the scientific community does have to get on top of this. And in fact all the other periods of reduced and enhanced warming in the past. Russ: Does the Pause give you pause? You were confident that there is a small chance of a large rise, based on the rough science and some of the models. Does it cause you to be a little more conservative? GuestE: Well, no. Not really. I think that range was generous enough that I would stick with it, until--maybe if we had 30 years of Pause. That would give me pause. Russ: We'll be back in 2029. Perhaps. Go ahead. GuestE: What would we all be saying if the next 15 years is rising at twice the rate the models predicted? Would we be trying to revise our estimates? I would have to say that I probably wouldn't revise my estimate upward, either, in response to that. There's a certain amount of natural variability that goes on. Russ: What are your thoughts on the so-called Pause, John? GuestC: I have no idea why it happened, but my thoughts back to what I have said in the introduction. When we understand a system in a scientific way, we can predict its behavior. I know of no one who predicted a flat temperature trend for the past 15, 16, 17 years. We were all under the belief--me, included--that CO_2 forcing would cause even more warming. And yet it did not happen. Russ: However, we do see--and I notice this elsewhere, on this platform, that people who are worried about global warming and climate change will point out there have been many plateaus in the past; that the underlying trend is what matters; small, short-term variability, of again--15 year's is one person's eon and one person's blink, another person's blink. You are suggesting it's closer to an eon. Kerry thinks it's a blink. Can't really make any conclusion from it. Past times, we've had plateaus. Is that just the difference here? Just a question of [?]-- GuestC: Well remember [?] when we talk about 120-30 years, we are starting at one of the coldest periods in the earth's history in the last 10,000 years. So the fact it's warming at all could be completely due to the natural variations. I happen to think the actual carbon dioxide, there is no way you could say it is not a forcing mechanism. It is doing something. And it turns out, and from what I gather and from what I can understand, is that there are ways that the earth's system itself actually feeds back in a negative way, so that that heat energy is not being stored like a climate model stores it. And so therefore the temperature is rising much more slowly, if at all. Russ: Kerry, can you convince him? Can you try to take a shot? Here's what I think. You can't argue with his basic point, because you conceded it, that of course, in any one year, any 5 years, maybe 15 years things happen we don't fully understand. The world is a complicated place. But the underlying science, which [?] back to 1897, which seems very convincing: Why can't John Christy see that this large increase in carbon dioxide accumulation is inevitably going to cause significant warming? Why do you think you can't convince him of that? GuestE: Well, because I'm a climate scientist and not a psychiatrist. I guess. Russ: A cheap shot. But go ahead. But an amusing one. The crowd really liked it. Go ahead. GuestE: I could have said something better [?]. Russ: Uh, I join you on most of that. [?] GuestE: You really do, I think, to look at, when you look at the earth's history, the response to forcing as at long time scales, I think you really do have to look at the 100 year time scale. That's very hard for us. We're much more interested in what's happening today and tomorrow, and very early on. When you look at the very long term, let's say not even that long by geological standards, 3 million year record, of climate, on the earth, and you see the spectacular fluctuations of climate--yes, and they were natural. And yes, in the case [?] usually--carbon dioxide itself, content itself fluctuated. In fact, most climate scientists believe that the tropics cooled and warmed was because of changes in CO_2. What you see, when you look at that record, is the last 7 thousand years, up to about 100 years ago, was remarkably stable. Sea levels remarkably stable. The climate was remarkably stable. We were very blessed to generate civilization in that 7000 years. Okay? And yes, if we didn't do anything at all, the orbital forcing suggests that we would be slowly cooling. As we in fact were, up until about 100 years ago. I agree with that. And we would continue to cool until maybe in 10 or 20,000 years--that's really a long time away--we would plummet, and probably will plummet, into another ice age. This thing is short. What we are doing now is short by geological standards. But still fairly long on the human time scale. I can't convince myself, as much as I would like to, that we aren't running a risk. I think we are running enough of a risk with our grandchildren that we should pay attention to that. Russ: John? GuestC: Um, was I supposed to be convinced by that? Russ: I don't know. Yeah. You could invoke, you could mention psychiatrists if you want. Or anything else you can think. GuestC: No, I, you know, I just go back to the hard numbers of the data. We just do not see these kinds of changes that are dramatic, that are hard[?], that were predicted. They are not happening. And so I am just am rooted in what's really happening in the planet.
34:39Russ: Well, let's move on to a different area. Which is sometimes as far as I can see goes under the name of 'extreme climate events.' This would be hurricanes, droughts, famines, etc. Kerry, your specialty is hurricanes. Have hurricanes and other extreme events gotten worse over the last 40 or 50 years, and can we attribute that to climate--to human activity? GuestE: I'm sorry to have to give a nuance. Russ: I like nuance. GuestE: In the Atlantic, demonstrably hurricane power has increased over the last 30 years by a big factor, too. I don't profess to understand that. It's gone up hand in hand with the tropical Atlantic surface temperature in the summer time. It's a tiny piece of the globe. And maybe some of that is global warming. I don't honestly know. I don't want to try to give you the illusion that I understand this. When you look globally, the problem there is a problem with data. The data are very poor outside the Atlantic. In the Atlantic we fly airplanes. I've done that. We fly airplanes into hurricanes. But we don't do that anywhere else in the world. 90% of the world's hurricanes occur outside the Atlantic. And so we are forced to rely on data which is not particularly suited for this. There is some indication of an upward trend in the most intense hurricanes, but I wouldn't want to put my money on that. Russ: Did you say you've flown airplanes into hurricanes? GuestE: Yes. Russ: What was that like? GuestE: Better than some flights I've had on Delta Airlines. Seriously, it's not as bad as you might think. Russ: As someone who doesn't want to take a lot of risk, that would make me a little bit nervous. It sounds like it was probably a pretty exhilarating experience. As a scientist. GuestE: Everybody should see the eye of a hurricane. When I retire, I'm going to start a hurricane safari operation, seek paying customers. Russ: That would be awesome. John, what do you think about hurricanes? GuestC: Dr. Emanuel is the expert on that. And I think he gave a terrific answer there. I look at other kinds of climate variables that are more readily available to us in terms of longer data sets, and those are things like droughts and floods and so on. And we are nowhere near the kinds of extremes that have occurred in the past thousand years in this country, for sure, where we have had mega-droughts. These are hundred-year kind of droughts, out West, and the periods of dryness and in fact the temperature here in Alabama has actually declined in the past 103 years. So when you look at those kind of extreme events, you don't see any change, really. Russ: Do you think there is hope of modeling hurricanes more precisely? GuestC: That's not a question I can answer. I always hope we can get better tracks because we are exposed on our Gulf Coast and it would be a terrific advancement to have. Russ: Are we getting better at it? GuestC: Over the last 40 or 50 years we've gotten substantially better at forecasting hurricane tracks. Really demonstrably better. Not much improvement at all in hurricane intensity. Russ: The tracking thing--they have a band of uncertainty around it. And I remember as a kid they were always off. And now they are really pretty good. I'd always say, when I'd look at the picture: Who knows? But they are pretty reliable now. Seems that way.
38:00Russ: Let's talk about another thing people care a lot about, you've mentioned briefly, which is sea level and Arctic ice. It's an issue that came up in a recent EconTalk episode with Judith Curry. What's going on with ice in the north and the south? How much do we know about it? How much uncertainty do we have about its impact on sea level? Kerry, you go first. GuestE: So, sea level is going up. And apparently at an accelerating rate. Russ: Can I ask, before you go on: How do you measure that? The sea is in a lot of places. GuestE: That's right. So, before the satellite era, it was measured with tide gauges. There's a real sampling problem with that. By the way, most people think the sea level rises uniformly around the globe. It doesn't. You can actually find places where it is going down. Just like temperature. [?] that's because it's affected by wind and things. In the satellite era, we've been able to measure the absolute altitude of the sea level globally, with absolutely stunning accuracy. The magicians at NASA (National Aeronautics and Space Administration) somehow figured out how to do this. And there's no question that it's going up globally, now, with those measurements. The ice is more complicated. First of all, sea ice, which we see a lot of changes, it doesn't affect sea level, when it melts it doesn't change sea level. Russ: [?] In general? GuestE: No. The sea ice doesn't change it at all. Russ: That's not an issue? GuestE: No. In fact, if you don't believe me, right after this talk go and mix yourself a nice Scotch on the rocks; I highly recommend it; and watch the ice melt. Tell me what happens to the Scotch. Russ: It's simple science. GuestE: Or if you are a teetotaler you can use Coke; that's okay. That's allowed. Anyway-- Russ: People don't talk about it that way, though. They talk a lot about the ice melting affecting the sea level. Is that-- GuestE: Well, the land ice, when that melts, it does affect it. So when ice melts that's sitting on land, like Greenland or Antarctica, melts, that affects the sea level. When it melts, the sea level goes up. The sea ice doesn't really change things. The Arctic sea ice in the summertime has been in decline since we've been able to measure it, which isn't terribly long. Antarctica is mixed, but in general, actual sea ice is increasing in Antarctica, not decreasing. Mountain glaciers, which are another[?] form of ice, almost all of them in retreat now, and we see big changes historically in glaciers. It's much harder to measure what's important for your sea level with[?] the big ice sheets in Greenland and Antarctica. And we are getting better and better at measuring those, but I think it's a little too soon to say what's happening to them. In both[?] the weight of the evidence is that they are losing mass, but they are certainly not losing mass everywhere. Russ: And what kind of magnitudes of sea level change do you think we are talking about here? GuestE: Well, this is--the best estimates from the last IPCC (Intergovernmental Panel on Climate Change) reporter on the order of a meter or so--3 feet by the end of the century. But everybody who is in that business says there is much more uncertainty about that than anything else. And one of the problems is that we don't actually understand the physics very well. You'd think we would by now. If I'd written a book called "What We Don't Know about Climate Science," it would have been an encyclopedia. Russ: Longer book. GuestE: But we don't really understand the physics at which ice slides off of big continents, like Greenland. It's not just melting and the water trickling into the sea. There's actually glaciers that flow off the ice sheets and calve into icebergs. That's what did the Titanic in, in the ocean. And we don't know whether that will accelerate. Here's what we can say: is that there were various times in the geological past, in previous interglacial periods, where apparently most of the Greenland ice sheet was gone--not all of it. If you did melt it all, somehow, and it would probably take a long time to do that, you are talking about 7 meters of sea level rise. You know, 25 feet or so. It's a big number. And Antarctica, if you melted that, I can't remember the exact number but it's much more. It's 50 meters or something like that. That's an awful lot of ice, and everybody I know in the field thinks it would take an awfully long time to do that. Russ: The implication is that small or potentially large parts of currently inhabited parts of the world would be under water. GuestE: So, if we go into an extreme-- Russ: I'm sorry, I just want to say, I've seen these, you may have seen these where Florida drops off the face of the earth and becomes an underground island. My attitude on that is partially--well, overnight it would be really bad. Over 150 years, not so bad. If it happened over 10 years, much harder to deal with. Might not be our best thing. What are your thoughts? GuestE: Well, the time scale is everything. It certainly won't happen--we don't think it will happen--in 10 years. But here's some food for thought. I think, and I'm now speaking a little more philosophically, that historically science and scientists have been very concerned with it in their estimates of risk. We didn't predict that there could be a magnitude 9 earthquake off of Japan that caused that huge tsunami. The largest estimates were for 8.3, which is way lower, actually. There are a lot of things that we haven't predicted. What we do know from the ice core records in the past, particularly in cold periods, the earth was capable of rather sudden changes, flips if you will, in the climate, at least locally, and we don't understand those flips. So, you know, what keeps us awake at night are the risks that we are missing. Okay? And we don't think that Greenland ice is going to go very fast. But there are a few models on it that say, yeah, once it gets going, it's really going to go. Nobody attaches a lot of importance to that, and we've put a very low probability on that, but we are frightened by what we don't know about that problem. Russ: John, talk about your thoughts on ice and sea level. GuestC: Well, the sea level is rising. And it will continue to rise because there is more land ice to melt. If you go back to the last interglacial, about 130,000 years ago, we find that sea level reached 6 meters higher than it is today. So, that should go on about an inch per decade just on that. Remember that out West in the Rocky Mountains and so on, those glaciers only appeared between a period of 3700 and 1900 years ago. So they are relatively new in the sense of our most recent climate. When I advise people about sea level, I say it's going to go up about an inch per decade, and if you are on the Gulf Coast, that's not your problem. It's the 15 feet in 6 hours when the next hurricane comes. That's your problem. Russ: For sure. GuestC: So that's the attack and that's the vulnerability you have there on the coast. Russ: So, you don't think there is a social or civilization issue that over the next hundred years we are going to lose some important things. GuestC: Well, it would happen very slowly. When people are building infrastructure on the coast and I have to do some kind of reports for those, I tell them: Look, if you are going to be there 100 years, plan for a meter of sea level rise. And if you build your infrastructure for that way, that much I think you are okay with. The hurricanes are what are going to hit you. Russ: Do you think we can do something about that meter? In other words, can human, can public policy, human behavioral changes, reduce the threat of the meter increase? GuestC: No. I presented evidence in Federal court before Congress and so on that the legislative action being planned and so on just will have no impact on that. Russ: Do you agree with that, Kerry? GuestE: I don't think it will have a direct impact, but I think it could have a pretty big indirect impact. Like all movements that go on, it starts small and it starts with something doable whose direct effect is probably not measurable. So in that sense I agree with it. But we have to start somewhere. You can't start with solving the whole problem in one day. That doesn't work. You have to start somewhere. I suppose at some point we'll talk about solutions to that. Russ: In about a minute. But I want to go back to John's claim, because the way I understood John's claim is that the rise in the sea level over the last century and the expected rise over the next century is overwhelmingly driven by a large trend that has nothing to do with human change, human activity, which is the recession of the ice age and glaciers, where carbon dioxide has virtually nothing to do with it. GuestE: Well, right now, the carbon dioxide influence hasn't had a whole lot of time to build up. It's only been around a few decades, really. And these are big blocks of ice, and they take a lot of effort to melt. And so it takes thousands of years for these things to melt. Is carbon dioxide adding to that? I think so. I think it is adding a little more. That's why I say an inch per decade instead of the 3/4 of an inch from last century that we experienced. Russ: One of the greatest things in the world that I didn't know about till recently is that until refrigeration people made money carving out large blocks of ice, putting them in the holds of ships, and taking them to very hot places so they could have a cold drink. Which now is not a viable economic enterprise because of refrigeration. But it does take a long time for a big piece of ice to melt, which is rather remarkable.
47:40Russ: Let's talk about policy implications of this conversation. I'll try to summarize it. Maybe there's nothing more to say. Because it may be that reasonable people can disagree on this. What I understand, Kerry, is in your view there's a small chance of a really horrific action, and therefore we should act. Again, Robert Pindyck in a recent EconTalk episode--he's an economist, that's his assessment of the risk that's involved. This is not really a scientific--it's partly a scientific question but at some point it becomes a philosophical question and--John Christy, you called it a moral question. But it's a small chance of a horrific risk. We should try to do something about it. It sounds to me, John Christy, that your view is that, well, it would be great if there were something we could do about it that was likely to work; you don't think the risk is very high and you think the risk of the solution is likely to be worse. So, John, I'll let you go first. Does that summarize your view of the difference between the two of you? GuestC: Somewhat. The risk of something bad happening by making energy expensive is real. People will suffer if energy prices go up; we already know that; there's just no question about that--and as I said, living in Africa, I know what energy poverty does--it kills people. And so anything we can do to allow energy to expand into those areas that do not have it, it's going to enhance human life and welfare. So, solutions to--if you are really concerned about the carbon dioxide then how can you create energy that is affordable--that's the only kind that really works in the economy--what choices are out there? And the big one that can answer the question is actually nuclear power. We're sitting right here between a couple of big power plants, actually. And it's difficult. It's a bet-the-company move right now for the few that are trying to build nuclear power. And that's probably going to change. Russ: Kerry? GuestE: Well, I actually agree with that. I think it's a mistake to do anything that increases world poverty. The history of this is very clear. Economic gains particularly in developing countries are largely, very strongly tied to the consumption of energy. So, we have to be clever about how we attack this risk. And I'm not of the camp that says, we should just go cold turkey on fossil fuels. We can't do that. Nobody in their right mind would suggest we do that. But we should try to approach this risk as intelligent people by exploring all kinds of alternatives. The experts I talk to are and I'm certainly not one say it's a question of doing a lot of little things that amount to a big thing, like building more energy efficient buildings. Even in developing countries. It actually ends up saving people money because they are not consuming as much energy. Energy is still going to cost something. Migrating away where it's practical from fossil fuels toward renewables. So there are some parts of the world, including Africa, where it actually makes sense to have a supplemental supply. Can't do everything with solar power, or maybe wind. I'm a big proponent, I get into lots of trouble with my colleagues over this, but like John, I'm a big proponent of nuclear energy. I'm so tired of being told we can't do it. France went from almost no nuclear to 80% nuclear in 15 years. Are you seriously telling me that the United States can't do, cannot do, what France did? I don't think so. There's one other piece of technology which would allow us to burn at least natural gas as much as we want to, if we could only get there, which is to capture the carbon from the atmosphere and sequester it. And I think it makes a lot of sense to put some money, not to jeopardize the economy, but some research and development money, into trying to develop this technology to the point where it might some day make economic sense to do that. We are not that far from being able to do it even today. So these are sensible things. We don't have to bet the farm. We just do sensible things. Russ: Do you think those sensible things work? Do you think geoengineering is feasible or will be feasible, it would offset some of the human impact? GuestC: Okay, geoengineering now is a different kind of question. That's where you want to do something explicit to stop whatever climate changing and gear it toward something you think you can. I think it is frightening to me to think of geoengineering. Because if we cannot predict the system now, how can we know what we are going to do if we try to geoengineer something? Like put up a bunch of panels that reflect sunlight or aerosols[?] in the stratosphere that reflect sunlight. Those are scary options to me because we do not know what might ultimately happen as a result of something like that. Russ: It seems like a good time to invoke my favorite quote of F. A. Hayek: The curious task of economics is to demonstrate to men how little they really know about what they imagine they can design. Which would be what you are worried about. Do you agree with that concern? GuestE: Yeah, very much so. [more to come, 52:50]

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COMMENTS (28 to date)
Brian G writes:

One of your best episodes in years. Both guests were respectful and informative.

Brad writes:

Thank you Russ, such a breath of fresh air to hear from people who've spent their lives studying these issues and are intellectually honest enough to admit when they do not know something.

mtipton writes:

LOVED the format, guests and moderator! Thanks for providing this content for us Russ. I wish it could have been longer. You did an excellent job at trying to nail down where the disagreements lie, and what the nature of the disagreement is. But more time was probably needed to really push them on their arguments and go back and forth. On scientific knowledge I was left wondering what their disagreement was with respect to CO2 in the long and short-term, it seemed like Emanuel was saying that even though CO2 wasn't able to predict climate temperatures in the shor-term, if you look at the long term it clearly does, was Christy disagreeing with this? I'll listen to it again see if that helps clarify.

Peter J writes:

Excellent panel discussion.

I am more optimistic than the panelists about the improvement in the models we can expect in the coming years. Moore's law continues apace for computing and satellite data provides high quality global data over longer time scales as they continue to orbit. We need to stimulate the development of models to take into account the biosphere response to climate change for example. So much more to learn and understand.

rhhardin writes:

then it's correct that the last 30 years, the models have overpredicted the temperature. I might add that 30 years before that, they underpredicted it. And this is what happens when you superimpose natural variability on forced variability.

This is what happens when you tune the model to match historical data and it's coming out too hot.

You go with an underprediction of past values to get a least squares best fit of all the data.

Models are secret curve fits, not physics.

rhhardin writes:

On CO2 forcing must cause warming --

Consider the gyroscope. If you force it west, it moves not west but south.

Are there cycles in the climate too?

Lee Jamison writes:

Excellent discussion! For possible future episodes I would like consideration of a few questions, though.

1. We always talk about the rate of change upward, but no one ever asks what it would take to slow change or to reverse it. How much inertia is built into the system as it is, and if we significantly changed our output of CO2 (as I fully expect we will when solar actually begins to near the cost of fossil fuels) what are the foreseeable rates of change?

2. We laypeople need a better sense of the dynamism of the climate system of the Earth over what are really not long timescales geologically. In this interview we heard a snippet about how stable the last 8000 years have been, but we heard nothing about how dramatically unstable the previous 110,000 years had been, nor did we hear how only in the relatively brief interglacials (such as we have been in for the whole of recorded human civilization)is the climate similarly stable. Sea levels commonly varied by as much as 400 feet during the last glacial period. Sometimes it varied by 100 feet in a century.

Other factors greatly affect climate as well. Our star is getting warmer, but in the last 50 million years the Earth appears to have been cooler than it was in the previous 200 million years. Tropical forest used to grow on Antarctica, even though it was then still in the Antarctic Circle.

So the second question is: Are there insights we can gain from understanding these relatively short (250,000 years), medium (millions to tens of millions of years), and long (hundreds of millions of years)climate timescales?

3. This question is really an economic one. I believe when costs of less encumbering systems near those of more encumbering systems there is often rapid, and even radical change. We saw this as the costs of hydrocarbon liquid fuels and their machinery fell into the range of the use of animals.
Is there any way we can begin to tell when such radical changes will be instituted as portable and non-networked renewable energy sources like solar fall in price?

Are there ways we haven't been broadly discussing to ease that process along? (I suggest devising roof-solar easments for utility companies to actually own the solar equipment on a house, for example).

Finally: When we talk about risks shouldn't we also consider the political and economic risks of precipitous action on carbon mandates? What might these include?

Rufus writes:

Very interesting discussion and I like how Econtalk seems to be directly challenging or engaging in the debate.

In this case, one of my questions regarding the model and predictions is: Why, if the following is true:

Well, I think it's relatively easy, and the fact Svante Arrhenius did it in 1897 without big supercomputers--my students do it after taking a couple of semesters with models they've built themselves. I don't think it's that difficult.

that the results of the various climate models all overpredict the warming by a significant amount? I suppose it is like the average CBO estimate of GDP or unemployment that also has huge errors. It may also be a case where having more data does not lead to a better result, only more spurious correlations and confusion.

The proponents of these forecasts only live in the present/future and never look back at their failures. It really is a curious phenomenon.

Victor Venema writes:

Rufus, the climate models are not running hot.

John Christy used a very short period, which Kerry Emanuel warned against. This gives a lot of possibilities to cherry pick; multiple testing in statistics is especially a problem for such short datasets with large trend uncertainties. He used these possibility to artificially shift the model results up, with a wrong method to align the models with the measurements.

For details see this post by a climatologist.

Mateo writes:

Great great episode!

It is so rare to have a discussion on this topic where two opposing views are presented with respect being given to facts and respect also given to (and earned by) each presenter.

A future episode that reviews the proposed mitigation strategies would be fantastic.

The wayward arena writes:

I found many interesting points as always and I have a few more interesting questions to propagate in my workplace and my classroom, thank you.

My Problem is deciding what to do or not do still eludes me. I just find it very difficult to access the risk.

Rob writes:

This is a really great exchange. What I find interesting as much more of a skeptic is that in terms of good and effective responses to the proposed risk I don't think there is actually any real disagreement. Energy efficiency, research into energy generation, and nuclear power in degrees that don't seriously weigh on the economy are not going to be controversial for anyone on the right even on simple national security terms. Even among the hardest core of skeptics that wouldn't be opposed. So ironically I think there is a consensus that probably ranges from right-wing skeptics a long way into the center-left on energy policy. Yet the actual policies from Ontario to Germany and America which never ratified Kyoto have been the kind that literally leave people hungry, cold and in the dark in the first and third worlds. That's the consensus that we really need to hear about and the one that can change the debate from being tribalized as it is.

MG writes:

Great exchange in the spirit of intellectual honesty. Perhaps because of that I wished a few other "screwballs" could had been tossed at the participants.

For Mr. Emanuel, for example, when discussing sea level rise, the effect of real (but non-sexy, from the CO2 perspective) man-made effects such as aquifer water being added (on net) to the water cycle (and thus eventually back into the oceans. Also, when discussing temperature data sets, the urban zone hot spots and its effect on everstating measured temperatures.

For Mr. Christy, I don't think we need a "psychiatrist" to fully understand his objections to Mr. Emanuel. However, I wished we had a better insight on where he would come down on a battery of risk-aversion experiments. This would be useful in evaluating his objections.

John writes:

Mr. Roberts,

I've been a fan of your show for a long time but I have to agree with most of the previous commenters, this was one of your best episodes. Not only was it informative but it felt balanced, not aggresive or defensive and addressed some key questions. I hope that you consider doing more of these panels.

I do wish however that there had been some more pushback regarding some of their assertions. Especially regarding the climate models. Mr. Emanuel said that we should be concerned because even though all the models overpredicated the fact that they overpredicated should be a worry. But why? If they all overpredicted then why should we rely on them at all? Similarly for Mr. Christy how, if at all, can we find out and be sure whether or not humans are the cause of global climate change? And if we cannot determine then shouldn't we still try to hedge our bets to make sure that we aren't causing the problems?

Thanks again for the great episode.

mtipton writes:

Hi Russ,

I've been looking into the inequality debate. It would be such a great exchange to see, Piketty and Saez and Burkhauser discuss their findings in a similar format.

Just and idea. Thanks!

Michael Byrnes writes:

This was an outstanding podcast! Well moderated and both guests presented their arguments well.

It was interesting that both guests favored more use of nuclear power. I used to think that more nuclear made sense, but lately I am less convinced, for a few reasons:

1. It seems that recently, with access to cheap natural gas from tracking, nuclear energy is less competitive on price. Some old nuclear plants (such as Vermont Yankee) are closing.

2. Nuclear power is not without risks. Christy noted that he was skeptical of the long-term risks of climate change and that the risks of anti-global warming policies might outweigh the benefits. Couldn't a similar case be made for nuclear power (risks outweight benefits). The probability of a nuclear disaster in the US is extremely low... but the costs (financial and otherwise) of such an event would be extremely high. Both probability and costs need to be considered.

3. On the topic of financial costs, I think it is fair to say that there is not a single private company that could bear the costs of a nuclear catastrophe. I doubt that even a consortium of private energy companies could bear the costs. The financial burden of a nuclear disaster would fall squarely on the taxpayer. Given this burden nuclear power would have to be either a state-owned enterprise, as in France, or a enterprise with private gains and socialized losses.

Apologies for the digression. I've been very curious about the economics of nuclear power for a while and I found it somewhat surprising that both guests endorsed it. (I would love to hear an Econtalk episode on this topic).

Urstoff writes:

Michael, pebble bed reactors are meltdown-proof: http://www.americanscientist.org/issues/pub/2014/2/a-path-for-nuclear-power

Rufus writes:

Seems like the transcript was cut a bit short as I recall some discussion of what people should do to become more informed - with Blogs being mentioned as a place to avoid. I find that quite curious and I think that academics have not adjusted to the fact that the Internet has liberated knowledge and there are millions of intelligent and passionate people who do have important insights and are very, very capable of spotting flaws in the logic of published research.

First, go back and listen to the Jonah Lehrer episode that discusses creativity and how companies have found that using teams with dissimilar backgrounds, or even posting problems to public sites, has led to breakthroughs. Why can that not be the case for climate science?

Second, instead of papers being published in dusty journals that sit on shelves or travel in the backpacks of grad students, seldom read, the Internet allows a rapid distribution of information to a very broad audience. Perhaps scientists should learn to expect this level of scrutiny, and perhaps it will improve the level of diligence in conducting research. (Always keep an eye on Retraction Watch for when it doesn't).

Finally, I was listening to a podcast on a medical topic today and the doctor and interviewer talked about the Democratization of science. Instead of multi-million dollar trials and locked down information, people with real needs are able to learn about things that may help them in the near term - not have to wait years for FDA approval. Yes, there are safety concerns in such an approach, but there are also risks of not being treated or using the wrong treatment simply because it is the currently recommended course of action. This trend allows a bright shining light to cast down upon the "designs" which might show flaws at an earlier stage before they can do as much damage.

Dan Hanson writes:

Peter J said:

I am more optimistic than the panelists about the improvement in the models we can expect in the coming years. Moore's law continues apace for computing and satellite data provides high quality global data over longer time scales as they continue to orbit. We need to stimulate the development of models to take into account the biosphere response to climate change for example. So much more to learn and understand.

The problem of modeling the climate is not the lack of computing power - it's that a complex system like Climate is intrinsically hard to model in a predictive fashion. When every change causes cascading interactions, and there are feedback loops which cause even small effects to grow large or vice versa, prediction becomes a very difficult thing.

These systems adapt over time, and the direction of the adaptations is very sensitive to small changes in initial conditions. They also tend to have an element of randomness to them.

For example, ant colonies are complex adaptive systems, and we understand how they work much better than we understand climate. We can model ant colonies in a computer very well. And yet, we have no capability at all to predict the exact form a new ant colony will take in the real world. We can't predict how fast it will grow, the pattern of food harvesting it generates, etc. Tiny changes in initial conditions dramatically affect its development, and there is an element of randomness as gatherer ants that are not following food trails explore randomly.

The same may be true for climate. If we could bottle our entire climate system so that we could reproduce it in exact detail over and over again to experiment, we'd likely find each time we started fresh, added some CO2 forcing and let it develop the final result would look very different from the last time. How do you predict the future of a system that behaves that way?

Eric Falkenstein writes:

[Comment removed for policy violation.--Econlib Ed.]

nmz writes:

This was one of the best climate discussions I've ever heard. It was great to hear two opposing sides discuss issues rationally. It helped that they were able to clearly articulate and disentangle the points of agreement (e.g., temperatures are rising) from the disagreements (e.g., causes and impacts). One of the better points I thought was the articulation of how these models differ from economic models, i.e, in that the physics is known, but extremely complex in weather prediction, whereas in economics even the equations can be a mystery and require regression.

Many thanks to the participants and great moderator.

Brian Rosen writes:

Fantastic debate.

Daniel Barkalow writes:

Looking at the global average surface temperature (which is what those graphs tend to show), is a bit like looking at someone's bank account. It's a pretty good approximation of how much money they have, but there's going to be a lot of variability, based on not knowing what outstanding bills the person has, and the person is presumably earning income continuously, but only getting paychecks at particular times. This mostly averages out, but there's the risk in looking at any particular moment that it's a really uncharacteristic moment.

In particular, it seems to me that the "pause" idea is based on the fact that 1998 was warmer than nearly every year since, while neglecting that 1998 was warmer than 1997 or any previous year by more than 15 years of predicted warming. If this were someone's bank account, we'd guess that it reflected an event like having their home purchase fall through after selling their old home: some huge asset not usually included ended up in their bank account for a certain period before going back to wherever it was. You wouldn't then think the person had stopped saving, just because they hadn't saved up to a level that matches when their house money was in their bank account. You'd say that there was weird accounting in 1998, rather than an incredible gain followed by a mysterious loss.

Russ Roberts writes:

Daniel Barkalow,

It has nothing to do with 1998.

Ignore 1998. The global temperature has been flat since 1999. It's either a temporary plateau or indicated there is something we don't fully understand about the climate. But it's not an overreaction to 1998.

Victor Venema writes:

Daniel Barkalow writes: "Looking at the global average surface temperature (which is what those graphs tend to show), is a bit like looking at someone's bank account."

That is a great analogy, I hope you do not mind I have cited it to my article with climate myths translated into econ talk.

Russ Roberts writes: "Daniel Barkalow, It has nothing to do with 1998. Ignore 1998. The global temperature has been flat since 1999. It's either a temporary plateau or indicated there is something we don't fully understand about the climate. But it's not an overreaction to 1998."

If you want to claim that the temperature is flat, you have to include 1998. If you start in 1999, the temperature did rise, just not as fast as the decade before, which had an exceptionally fast temperature increase, faster as projected.

That one year makes so much difference already signals that this period considered is much too short and the uncertainties consequently very large. In fact the uncertainties are so large that you cannot reject no trend, but you can also not reject that the trend has continued at the projected rate.

That the short term trends vary is no reason to claim that we do not understand the climate system. We know that there is natural variability, it has always been there and it will remain. Most of the heat of the climate system goes into the ocean, the atmosphere is just a small part of the climate system. It is important for us, but small. How much of the energy goes into the atmosphere thus depends on ocean circulation. And that seems to the main reason for the current short term weaker trends.

Since 2008 the growth rate has slowed down. Would you therefore claim that markets are no longer efficient? Would you claim we do not understand the economy? Or would you simply call this a recession and point to the financial sector as an explanation?

It is the same way with climate.

Brett Gosage writes:

Kerry Emanuel began his remarks by citing work on IR radiation absorption by John Tyndall. He described Tyndall's work as showing that "all of the absorption of infrared radiation that takes place in our atmosphere is done by a tiny amount of gas that makes up less than 1% of the atmosphere." I assumed he was referring to CO2. This would only be true of dry air. We know that the widest and strongest IR absorption bands in the atmosphere are due to water vapor.

In fact, Tyndall " concluded that among the constituents of the atmosphere, water vapor is the strongest absorber of radiant heat and is therefore the most important gas controlling Earth's surface temperature. "

http://earthobservatory.nasa.gov/Features/Tyndall/

[broken html removed--Econlib Ed.]

Steve Sedio writes:

Great discussion, no name calling, no vitriol, unique in this debate.

BUT, there were a few significant questions that weren't answered.

As I've asked before, what do we do about it?

Improving efficiency will reduce per capita production, but the population is increasing faster than efficiency is. And there is a limit to efficiency improvement. (As far as saving money, what a laugh - reducing energy use results in higher per unit costs, and higher bills).

We need CO2 neutral (actually CO2 minus) sources of energy. We can spend a huge amount of money to create a patchwork of variable sources, solar, wind, tidal, etc. We can build hundreds of nuclear plants. At best, that addresses electricity. What do we do about transportation?

Outrageous energy costs for decades in Europe hasn't resulted in any alternative energy break throughs. Why would increasing taxes globally have different results?


IMHO, climate change is a minor concern compared to the other things we need to protect our grandchildren from. I would be less suspicious of political motivates if the same energy was spent to:

1. Fix the national debt, and unsustainable social spending (mostly for retirees).

2. Prevent major loss to total extinction from an asteroid?

3. Prevent major loss from an eruption at Yellowstone, from landslide based tidal waves?

4. Deal with MRSA, pandemics, bio-warfare?

5. Reduce diet related chronic illness?

Rn Crossland writes:

Terrific show. Fantastic moderation. Russ, you may want to explore you moderator skills more often - you did a really good job. I read about climate change and this was the best exchange of experts I've had the pleasure to hear.

The overall take-away, for any complex science, is that explanations are almost never simple, and all of us suffer from congeniality or confirmation bias. I support the view that shifting the conversation from which tribe is correct to a better level of understanding or attempting to form better questions to discuss usually yields better outcomes. To overcome our human tendency to side with a tribe, however, is not something we work at hard enough in private, educational, or social life.

Thanks for demonstrating that it is possible.

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