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Story Publication logo February 3, 2017

Kerry Emanuel: A Climate Scientist for Nuclear Energy

Nuclear power

Can and should nuclear power play a significant role in combating climate change?

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The Doomsday clock, the logo of The Bulletin of the Atomic Scientists, showing two and a half minutes to midnight.
The Doomsday clock, the logo of The Bulletin of the Atomic Scientists, showing two and a half minutes to midnight.

In early December of last year, MIT meteorologist Kerry Emanuel and three other prominent climate scientists were worried. Not just about global warming, but also about the international climate negotiations that had begun a few days earlier in Paris. Something was missing from the discussion.

On the fourth day of the conference, Emanuel and his three colleagues—James Hansen of Columbia University, Ken Caldeira of Stanford University, and Tom Wigley of the University of Adelaide—published an op-ed in one of Europe's leading newspapers, writing that "we have become so concerned about humanity's slow response to this challenge that we have decided we must clearly set out what we see as the only viable path forward." Their solution: a rapid ramp-up of nuclear power, along with increased investment in renewables. "Nuclear will make the difference between the world missing crucial climate targets or achieving them," the four scientists wrote (Hansen et al. 2015).

It was not the first time that they had argued in favor of nuclear energy. In November 2013 they published an open letter to "policy influencers," warning that "continued opposition to nuclear power threatens humanity's ability to avoid dangerous climate change" (Caldeira et al. 2013).

Emanuel and his three distinguished colleagues in some ways resemble the four US statesmen who have repeatedly made a public case for nuclear disarmament—former Secretaries of State Henry Kissinger and George Shultz, former Defense Secretary William Perry, and ex-Georgia Senator San Nunn, collectively dubbed the "four horsemen" of the nuclear apocalypse. When they speak, people listen.

The 61-year-old Emanuel specializes in atmospheric matters and is best known for his work on hurricanes. His research has shown that global warming is likely to increase the intensity—although not necessarily the frequency—of hurricanes and tropical cyclones. He is the author of "What We Know About Climate Change" (MIT Press), and the co-founder of the MIT Lorenz Center, a climate think tank. In 2006, Time magazine named him among the 100 most influential people of the year.

In this interview with Bulletin contributing editor Dawn Stover, Emanuel explains why he believes nuclear power is essential for decarbonizing the global electricity system—and why he thinks it might happen under a Trump administration. He also responds to the criticism that his support for nuclear power is "a new, strange form of denial that has appeared on the landscape of late, one that says renewable sources can't meet our energy needs" (Oreskes 2015).

In this interview, MIT meteorologist Kerry Emanuel explains why he and three other prominent American climate scientists have been outspoken about their support for ramping up nuclear power as a solution to climate change. He discusses issues of safety, cost, waste, and proliferation. Emanuel emphasizes that all energy technologies have dangers, and that the dangers of nuclear power must be weighed against those of other technologies. He suggests that a society powered entirely by renewable energy, even if that were to be technically achievable, might not be the best possible solution from an economic or environmental standpoint. He explains why he views the climate problem as not just a risk, but also an opportunity to transform the electrical power system and improve the economic well-being of the developing world.

climate change, Mark Jacobson, Naomi Oreskes, nuclear energy, proliferation, renewable energy, safety, waste

BAS: What made you decide to write your November 2013 open letter advocating for nuclear energy?

Emanuel: In my case, that came out of an insight by a Republican ex-Congressman from South Carolina, Bob Inglis, who is rare among his party in accepting climate change as a risk. His insight is that people are afraid of what the solution will look like. The solution that's been painted for a great many people basically gives them the impression that they'll have to cut back on their use of energy, and/or the price of energy will go up a lot, and the economy will sink. That motivated me to try to see whether there was a more optimistic picture that one could paint, and that is how I started to become enthusiastic about nuclear solutions.

BAS: How did you come to collaborate with your three colleagues on that letter and also on your more recent op-ed in The Guardian?

Emanuel: Climate science is a relatively small field, and most of us know each other through interactions at conferences. We discovered, by talking to each other, that we were among the rare breed of scientists who could see that any real solution to this problem is going to have to involve nuclear energy—barring some other kind of technical breakthrough, either in energy storage or in carbon capture and sequestration. We were taking our own science very seriously—that there is a risk—and to confront that risk, we really have to start becoming serious about solutions. We came to understand that renewables, at least today, can't be the entire solution to our energy problems.

BAS: In that first letter, you did express some support for renewables.

Emanuel: Yes.

BAS: Are there renewable technologies that seem especially promising to you?

Emanuel: The price of photovoltaics has dropped very reassuringly over the last few years. When we consulted people who, unlike us, are energy experts, the picture we formed is that you can ramp up solar power and other renewables without it being an economic disaster—up to the point where they are supplying somewhere between 30 percent and maybe 50 percent of current power needs in most countries. But then you start to get into trouble, because solar and wind power are intermittent. Unless we can solve both the transmission problems, which I think are the easier problems to solve, and the storage problems, which are very hard, we can't economically ramp up renewables to cover our entire needs. And even if we could do it technically, it's not clearly the best solution either from an economic standpoint or from an environmental standpoint.

BAS: Nuclear currently provides about one-fifth of US electricity. What do you think the ideal mix of energy sources should be, both in the short term and the long term?

Emanuel: I don't feel qualified to answer that in any kind of quantitative way. But if you just look at the history of nuclear power and renewable power, what you see is that the countries that have decided to ramp up nuclear very quickly—Sweden and France being probably the top examples, and the United States maybe in third place—they have been able to do that. In 10 to 15 years, you can go from almost nothing to, in the case of France, 80 percent of your electrical power. Whereas the history of renewables, even where they have been deliberately ramped up quickly, such as in Germany, it's a much slower pace leading to a much smaller fraction of total energy demand. And that's what led us to think we really have to do two things today if we're serious about attacking the climate problem: Deploy the light water reactor technology we already have available, and at the same time put a lot more resources into developing what you might refer to as next-generation or Generation IV fission reactors that have certain advantages over the old light-water technology.

BAS: Would you divert any subsidies or incentives or government grant support from renewables to nuclear to make that happen?

Emanuel: I think our basic philosophy is that there should be a broadly level playing field among all of these energy sources, except that you might want to penalize carbon-based energy to force fossil fuel companies to pay for their externalities, such as the enormous health cost associated with burning fossil fuels. As to what the level playing field looks like, that gets into nitty-gritty politics. Should we subsidize both nuclear and renewables, or should we subsidize neither—and also take away the subsidies for fossil fuels, and maybe pass a carbon tax? That is a very interesting and complex set of questions that the four of us don't feel qualified to answer. But we do think that maybe there's enough evidence and enough published papers by experts to suggest that nuclear is being left out in the cold right now, compared with incredibly cheap natural gas and highly subsidized renewables. It's not as though nuclear has no subsidies, but it's not being subsidized at anything like the level of renewables.

BAS: If you really wanted to level the playing field, would you take away the liability protection that the nuclear industry has?

Emanuel: I think we all regard the liability insurance as a form of subsidy. And again, whether that is in some sense quantitatively equal to the subsidies being given to renewables is something for the experts. The other problem is that if you shut down a wind farm or a solar farm, it's not that big a deal to reopen it. If you shut down a nuclear power plant, that's probably permanent. And if you lose the expertise—the engineers, the manufacturers of parts, and so forth—then it's not something you can get back. From that standpoint, there is a legitimate reason to be a little bit more protective about nuclear.

BAS: Let me go back to your original letter, because in that you talked about deploying "safer nuclear energy systems." That language makes it sound like something other than existing nuclear power technology. What did you mean by that?

Emanuel: There are two things we meant. One is just modernization of light water reactors to make them more passively safe. We were thinking about some of these designs to put Westinghouse AP1000 pressurized water reactors on offshore platforms—an idea that I've seen floating around in several papers. But we were also thinking about the need to put more resources into the development of Generation IV fission reactors, which are based on different kinds of reactions that involve things like thorium, and are cooled differently—with molten salt, that sort of thing—that can be designed to be more passively safe. When the four of us give talks, we often cite statistics that show that, over the lifetime of nuclear power in the world, in terms of mortality per kilowatt-hour, existing nuclear is far and away the safest energy source we've ever had. So making them safer shouldn't be interpreted to mean that the existing ones are dangerous. We don't mean to imply that.

BAS: Your original op-ed created a lot of divisiveness among climate scientists and activists, and I'm wondering whether you saw that coming. Should you have been more supportive—or less dismissive—of renewable energy?

Emanuel: Climate scientists and environmentalists are really very distinct groups. There might be a little bit of overlap, but the public and indeed scientists outside our field don't necessarily see that difference. Climate scientists usually don't even concern themselves with things like energy, so the pushback came from social scientists, environmentalists, and other people. Aside from one article by [Harvard University science historian] Naomi Oreskes, there wasn't that much pushback. I think a lot of environmentalists are beginning to recognize that if we're really serious about the climate problem, nuclear has to be part of the solution—again, barring some technical breakthrough.

BAS: Since you mentioned that op-ed in The Guardian by Naomi Oreskes, how did you feel about being called a climate denier?

Emanuel: You might be surprised to hear that she's a friend of mine.

BAS: That does surprise me.

Emanuel: In fact, she and I have been working together on an entirely different project that has nothing to do with energy. So, you know, this is just part of the to-and-fro in the scientific arena, and people shouldn't read all that much into it. But there are, of course, different opinions about what mix of carbon-free energy is optimal—and what we should subsidize, and what we should not. There is a group of people led by scientists at Stanford, notably Mark Jacobson, who believe that it's technically possible to go 100 percent renewables in the United States. And there's another group of people who are suggesting that such a plan is based on a lot of very dicey assumptions.

BAS: Why haven't you published detailed analytical studies, in peer-reviewed publications, comparing nuclear power's pros and cons with renewables?

Emanuel: The simple answer is that I don't feel qualified. But others who are qualified, like Armond Cohen of the Clean Air Task Force, are publishing such things. In the debate as it's been framed—for example, by Naomi Oreskes—there's a tacit assumption that if you can do it with 100 percent renewables, that's what you should do. I push back on that as a matter of logic. In other words, if you can do it technically, the other questions you have to ask are: Is it the best way economically? And is it the best way environmentally? There are environmentalists, I'm sure, who would rather see a few nuclear power plants scattered around the country than to see huge swaths of it covered with solar cells and/or windmills. It's not clear that the environmental consequences of nuclear power are more severe than the environmental problems associated with renewables.

BAS: Is there a nuclear power technology that you see as especially promising today?

Emanuel: I think we have to take into account costs, safety, and very importantly, how fast we can ramp it up. The real growth in energy consumption won't be in countries like the United States, but in places like India, which is sitting on very large deposits of very dirty coal. How are you going to convince them, if they undergo the kind of expansion that China did, to do it in a carbon-free way? How to power the United States is an important problem, but it isn't the most important problem. So, this question of ramping up nuclear: One difference between France (which was able to ramp up very quickly) and the United States (which didn't ramp up quite as quickly) is that France had a cookie-cutter design for its light water reactors. They had interchangeable parts, and the personnel were interchangeable between plants; whereas the United States did this one-off model, which I think is, in the end, causing us a lot of grief and expense. And as far as expense goes, there's no question that, in the United States anyway, the upfront capital costs of building a light water reactor are pretty impressive. But the lifetime costs seem to be fairly competitive with the lifetime costs of renewables—in fact, better than the lifetime costs of renewables. It depends upon how you look at the economics. It's quite a different answer for short-term economics versus long-term economics.

BAS: But even in France and Sweden, where there was a rapid ramp-up, nuclear production there peaked by 2010, and the average reactor is now more than 30 years old. So there are some huge economic challenges.

Emanuel: That's right. If you're sitting in Sweden and you need to replace an old power plant or build a new one, boy does natural gas look attractive, particularly if you're a politician—because the upfront costs of building a gas-turbine power plant are so small compared to building a nuclear power plant. If you are, on the other hand, a rare example of a politician committed to the long-term energy needs of a country like Sweden, you might ask: "What will gas cost in 20 years? And don't we have some responsibility to the environment? And what if the Paris process eventually leads to a whopping carbon tax?"

BAS: Here in the United States, there are some Republican "clean energy" groups that agree with you that renewables alone will not be enough to deal with climate change, but they also strongly support natural gas as well as nuclear. Is that a mistake?

Emanuel: That depends on what the strategy is. If you can quickly replace coal plants with gas-powered plants, that's a short-term big plus for the environment, for the simple reason that the carbon intensity of coal is about three times that of natural gas. If it's a long-term strategy, on the other hand—if we're going to burn gas for the next 40 years, say—then it doesn't make much sense.

BAS: Let's talk about your December 2015 op-ed in The Guardian, in which you argued that policy "must be based on facts and not on prejudice." What prejudice were you referring to?

Emanuel: The prejudice is that it's dangerous and expensive, and that there are unacceptable risks. We haven't talked about the big one, which is the nuclear proliferation problem.

BAS: Let's talk about that, because you have supported reprocessing. People worry about reprocessing not just because it's expensive but also because it's a way to separate weapons-usable material from spent fuel. That doesn't worry you?

Emanuel: Oh, it does worry me. It worries me a lot. And it should worry everybody. It's the downside of nuclear. There are a lot of people who get hysterical about the safety of nuclear power plants when they should be getting anxious instead about the safety of the fuel cycle. The problem is, that cat is out of the bag. China and Russia, for example, are already building lots of light water reactors, and they're selling or leasing them to other nations. And that's what, if I were a security analyst, I would be focused on, rather than the stockpiling of nuclear waste in the United States—which is also an issue, but not where I would focus my concern. What can the United States, for example, do about China selling light water reactors to third-world countries? Not much. We can't tell China that they can't do that. We can't tell those third-world countries they mustn't buy from China. The only way we can deal with it is to out-compete them. And by that, I mean make it more attractive for other nations to buy clean energy from us than from them. If you're worried about proliferation, shutting down Western nuclear reactors is not necessarily the right thing to do. In fact, it may even be counterproductive if the world turns to less scrupulous regimes to supply nuclear energy.

BAS: What about the waste issue? The best-case scenario here in the United States is that the Energy Department will open a permanent repository in 2048. How can you make a case for expanding nuclear power when we still haven't figured out what to do with the waste from last century?

Emanuel: I think it's a big problem, but nuclear is not the only energy source that has a waste problem. The waste from coal is very dangerous; it's even fairly radioactive. So I think waste is a serious issue, but it's not in my mind a showstopper.

BAS: You have described 100 percent renewable energy scenarios as wishful thinking. But at the same time, you suggested that building 115 nuclear reactors per year would decarbonize the global electricity system. That is 25 times greater than the average number of reactors built per year in the past decade. Why isn't that wishful thinking, too?

Emanuel: You're right to call me out on that as wishful thinking, but it's a different kind of wishful thinking. You might call one wishful thinking, and the other magical thinking. To get to 100 percent renewables, we have to rely on breakthroughs that haven't yet occurred—in power transmission and particularly storage. With nuclear, we don't have to make that bet. We may be wishing for something that is quantitatively difficult, but it's not technically impossible.

BAS: Jim Hansen called the Paris talks a "fraud." Do you agree with that assessment?

Emanuel: No, Jim and I don't see eye to eye on that.

BAS: How did you feel about the Paris Agreement?

Emanuel: I thought it was a good step forward, in the sense that you had 195 nations actually sit down and agree to take some concrete steps. That was a very important first step.

BAS: You held a press conference in Paris to call for including nuclear power in climate solutions. What effect did that have?

Emanuel: Oh, probably not very much!

BAS: It was reported.

Emanuel: That was the idea. We basically went there to try to keep the nuclear card on the table. Because if we hadn't gone there, I don't think it would have been on the table at all. You have countries like Germany that responded to Fukushima by basically deciding to close down their nuclear power industry, and environmentally that's been a disaster. They stepped up renewables, which is great, but they've also reopened coal-fired plants, which is terrible. Their carbon emissions have not gone down, and they are buying part of their power supply from France—which is largely nuclear. So they didn't really get off nuclear; they just got it out of their own backyard. We didn't think it was very rational to react to Fukushima by trying to shut down the whole industry.

BAS: In the United States, support for nuclear power in Congress tends to run along conservative lines, and not many big environmental groups are gung-ho about nuclear power. Why do you think that is?

Emanuel: I can answer the first part of your question a bit more easily. Republicans—some of them, not by any means all of them—get that, regardless of whether climate change is happening or not, the rest of the world is making the bet that this is happening and is turning to other sources of power. For a lot of Republicans, it's all about American economic competitiveness. If China is building lots of reactors, if they will build Bill Gates' relatively new design and sell it, we're losing our competitive edge. There was a recent column in Forbes online by James Taylor that was one of the most compact expressions of the position of an increasing number of Republicans. It was really interesting to me because James Taylor is very high up on the list of people we call climate change deniers. And he doesn't actually back off that in this column, but he says in no uncertain terms that we've got to be playing the game on clean energy, and we ought to be ramping up nuclear power and nuclear research. I consider it progress when Republicans are arguing for nuclear power, as opposed to arguing against doing anything at all. What kind of clean energy we're going to have is a much better argument to have than whether we need any at all.

BAS: As someone who was a conservative Republican for many years, how do you feel about the prospects for climate action with Donald Trump as president-elect?

Emanuel: I have been an Independent since about 2009 and do not identify at all with those who today claim to be conservatives. In fact, I regard their agenda as radical. If Trump and Congress make good on their pre-election rhetoric on climate change, we are truly in trouble. But I am an optimist and believe that once the new administration recognizes the economic opportunity associated with the transformation of the $6 trillion global energy sector to carbon-free sources, they will do something that previous administrations have lagged on, which is to greatly accelerate research, development, and deployment of clean energy—including nuclear. They can do this in good faith whether or not they regard climate change as a serious risk. I sometimes feel a bit frustrated that I spend half my time dealing with conservatives who deny we have a problem, and half my time with environmentalists who fantasize about what the solutions will look like. Everybody is always talking about risks and downsides and high prices and all that, but there is an opportunity now to transform our electrical power system in a way that makes sense in the long run, because sooner or later we will run out of fossil fuels.

BAS: We hear a lot about the scientific consensus regarding human-caused global warming, but much less about the support among scientists for nuclear power—for example, the American Association for the Advancement of Science survey that found two-thirds of its members supportive. Why?

Emanuel: Nuclear is against the ideology of the environmental movement, at least in this country and in many other countries. I say to my environmentalist friends: "Look, if you shut down a nuclear power plant somewhere and replace it with coal or even gas, and generate the same amount of electricity, a lot more people will die!" It's not that they're dying dramatically in a meltdown; they're dying one at a time from horrible respiratory diseases and so forth, but they're still dying.

BAS: Isn't it reasonable to think in terms of other types of damage besides death? Fukushima and Chernobyl, for example, contaminated huge areas of the countryside, and that has a profound effect on people even if it doesn't kill them.

Emanuel: Yes, it does. But strip mining is also extremely degrading to the environment, and fracking has its own problems. So I absolutely am for a quantitative comparison of all these downsides. But it is interesting that in most industries, if there's a big accident—like if an airplane crashes—we find out what happened, and we solve the problem so that it won't happen again. But if there's a nuclear accident, the reaction is to shut the whole industry down, and that I don't understand. Shouldn't we expect, and demand, that plants in the future will be safer than the plants of the past? The bottom line is: We can't compare the dangers of nuclear power to the safety of having no power at all. Realistically, we have to weigh all the dangers of nuclear power against the dangers of every other power source.

BAS: Why do so many people focus on technology solutions that would increase the energy supply? Do you have more faith in technology than in the human capacity to reduce our energy demand?

Emanuel: Conservation is great, and I'm all for it. I have solar panels on my house, and I replaced all my bulbs with LED bulbs this summer. But energy consumption should go up rapidly in the developing world, because economic and social well-being depend upon that, and population growth is very much correlated with economic well-being. In countries with good economies, people don't feel the need to have so many children. But if we promote the use of carbon-based energy in the developing part of the world, we're all going to have a terrible problem. So what's the solution? A rapid escalation of carbon-free energy for the developing world. I think that's a matter of justice.


Caldeira, C., K. Emanuel, J. Hansen, and T. Wigley. 2013. "Top Climate Change Scientists' Letter to Policy Influencers." CNN, November 3.

Hansen, J., K. Emanuel, K. Caldeira, and T. Wigley. 2015. "Nuclear Power Paves the Only Viable Path Forward on Climate Change." The Guardian, December 3.

Oreskes, N. 2015. "There is a New Form of Climate Denialism to Look Out For—So Don't Celebrate Yet." The Guardian, December 16.



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