with Spencer Greenberg
the podcast about ideas that matter

Episode 195: The alternate histories and possible futures of nuclear weapons (with Carl Robichaud)

Enjoying the episode? Want to listen later? Subscribe on any of these apps or stores to be notified when we release new episodes:

February 3, 2024

Has the world been "lucky" so far with respect to nuclear weapons? How many people have died from nuclear weapons? To what extent do nuclear weapons actually deter aggression? How many countries currently have nuclear weapons or are in the process of building them? How can we discourage continued proliferation of (or even the desire to own) nuclear weapons? How tightly linked are the technologies required to build nuclear energy programs and nuclear weapons programs? How does the International Atomic Energy Agency verify that countries have exactly the nuclear programs and materials they claim to have? What are the best nonproliferation or disarmament interventions being considered right now? What can the average citizen do to make a difference on these enormous issues?

Carl Robichaud co-leads Longview's program on nuclear weapons policy and co-manages Longview's Nuclear Weapons Policy Fund. For more than a decade, Carl led grantmaking in nuclear security at the Carnegie Corporation of New York, a philanthropic fund which grants over $30 million annually to strengthen international peace and security. Carl previously worked with The Century Foundation and the Global Security Institute, where his extensive research spanned arms control, international security policy, and nonproliferation.


  • At 00:23:10, Carl said "Stanislav Arkhipov", but he meant to say "Vasily Arkhipov".

JOSH: Hello, and welcome to Clearer Thinking with Spencer Greenberg, the podcast about ideas that matter. I'm Josh Castle, the producer of the podcast, and I'm so glad you've joined us today. In this episode, Spencer speaks with Carl Robichaud about the history, development, and present threat of nuclear weapons.

SPENCER: Carl, welcome.

CARL: It's great to be here. I love your podcast and glad we got a chance to chat.

SPENCER: Thanks. Today, we're going to talk about an incredibly important topic, which you're an expert in, which is nuclear war, nuclear disarmament, and how risky are nukes for the world. I imagine that a number of listeners have already heard podcasts or YouTube videos on this topic. So today, I really want to go into things that I've always wondered that I've never heard someone talk about, and see if we can get some answers. Some of them are gonna be difficult questions that nobody knows the answer to but I at least want to hear your opinion.

CARL: Yeah, that sounds great.

SPENCER: So let's start with a thought experiment: Suppose that we could rewind history, again and again, from the beginning of when nuclear power and nuclear weapons became feasible, how often do you think we would have had much worse outcomes where there just was way more use of nuclear weapons than we actually saw? In other words, have we been really lucky or did we get the kind of typical situation that you would expect to occur?

CARL: I love this question, and I think it gets at the heart of the problem that we have: that we only have this one history to look at. And then you have some people, when they think about the role of nuclear weapons in the past 80 years, who would say, "Look at these weapons. They coincide with the greatest period of great power and peace in history. You don't have large scale wars of the type that you used to have every 20 or 30 years between large powers, and nuclear weapons have to be part of that story. They've averted war, and they are a great thing." And you have other people who say, "No, look at what actually happened during this time period. Look at how close we came on all these occasions. And if we continue to run those risks, we're going to end the world or end civilization or lead to hundreds of millions of people dead. These weapons are unsafe for any hands, and we should get rid of them." And often, each side kind of retreats to their camp and sticks with those arguments, and there's not a lot of data that can contradict these claims. I think that the right way to look at these weapons is to think: in expectation, have nuclear weapons been good or bad for the world? And again, it's hard to determine how close we came. One thing we can tell, with some degree of confidence, is what the consequences would have been if nuclear weapons were used, especially at the height of the Cold War. You're looking at estimates of 300 to 500 million people dead in the course of the first couple days of a nuclear exchange between the United States and the Soviet Union, like in 1963, around the time of the Cuban Missile Crisis. And that outcome just counts the prompt and immediate deaths from the blast. It doesn't take into account the fires or any of these second order effects, which we've since learned about in terms of climate effects, nuclear winter, the second order effects of radiation, etc. So the outcome of a nuclear war is really bad, and we can kind of put parameters around how bad it would be, although there's a lot of uncertainty there. How likely is it that nuclear weapons are used? I think you have a couple moments during the Cold War where the use of nuclear weapons seemed to be pretty likely, maybe not more than 50%, but the Cuban Missile Crisis is the one that I come back to. And I think Kennedy estimated the risk of nuclear use during that crisis was between 1 in 3 and 1 in 2. I don't know what to make of that estimate. I think it sounds pretty plausible to me, actually, after having looked at the history and how many different potential incidents there were that could have led to nuclear war. But let's say you think it's 1 in 3 in expectation, that crisis would have led to hundreds of millions of deaths.

SPENCER: So for context, how many total people do you think have ever died from nuclear weapons in history?

CARL: I think from Hiroshima and Nagasaki, we have estimates that range from around 130,000 to 230,000 direct victims from those bombings, with additional deaths in the subsequent years from cancer, leukemia, and other consequences. That number is a pretty wide range, and I think it's disputed because there are limits to how many people you can say directly died from the blast. You also have various health effects from nuclear testing, but I think those probably pale in comparison to the actual use in Hiroshima and Nagasaki.

SPENCER: Can we say confidently that less than a million people have ever died from nuclear weapons?

CARL: Yes.

SPENCER: So it's less than a million. So then, let's say we take the bottom part of your estimate of how many people might have died in exchange between the Soviet Union and US, you said 300 million to 500 million. So let's say 300 million to be conservative. Even if there was a really small probability of that occurring, that would still be way more than a million people in expectation. So even if that had, let's say, a 5% chance of occurring, that would already be 15 million deaths. So that math suggests that we were actually incredibly lucky that the number of deaths we got fell dramatically below sort of the expected value. And that's just considering one near miss. What would you say to that?

CARL: Yeah, I think that sounds right to me. Now, some people would say, "Well, nuclear weapons may have prevented another World War II." Some estimates that there were about 40 million deaths of civilian and military personnel in World War II. So on the other hand, some people argue that the existence of nuclear weapons kept the Cold War cold, so to speak, and avoided what would have been a military conflict on the scale of World War II, between the Soviet Union and the West. And World War II led to about 40 million deaths of civilians and military personnel, and what types of risks would you need to take with nuclear weapons for it to be worth it to avoid a war like that? That's assuming that nuclear weapons actually avoided a war like World War II. That's a really contested premise. And there are a lot of people who think that even absent nuclear weapons, there never would have been a war between NATO and the Soviet Union because both sides were so exhausted, and they had ideological views that, over time, their side would prevail. And so they may not have engaged in a large-scale war in Europe anyway. Instead, they fought a lot of proxy wars, which did have a massive number of deaths and cascading consequences from those.

SPENCER: It seems to me that there are three different questions that we're circling around here. And so I just wanted to distinguish them just for clarity. The first question is: The number of deaths we actually experienced in history from nuclear weapons, was that far lower than the expected value or the average we should expect, if we can rewrite the history? And I think you made a pretty compelling argument that, actually, it seems way below the expected value. And so in that sense, we seem really lucky. The second question you could ask is: On average, have fewer deaths occurred because of nuclear weapons or not? And there, you'd have to actually also take into account the counterfactuals like, "Did nuclear weapons prevent other wars from occurring?" And that seems really tricky because we just don't know. You can make an argument that maybe it prevented other wars, but it's hard to say. Then there's a third thing you could ask which is: Was the scenario we actually got an unlikely scenario or was it kind of actually the typical scenario? And this draws a distinction between sort of the mean and the mode. It may be that our outcome was way below the mean outcome — so we were much luckier than mean — but we might have gotten the modal outcome. Maybe in most rewritings of history, there is no massive nuclear war. It's just that when there is, it's so so bad, that it kind of makes the mean absolutely horrible. And so I'm wondering, on that third question, do you think that we got the most likely outcome, that in most rewriting history, we would not have had a nuclear war? Or do you think, even on that way of looking at the modal outcome, we actually were pretty lucky?

CARL: I've never thought of it quite that way. I think that's a really good observation. And my hunch is that the modal outcome is no nuclear war, or at least no large nuclear war. Actually, I think the modal outcome might be a small use of nuclear weapons somewhere in the world in the past 80 years that doesn't escalate and lead to all out annihilation. So the equivalent of a nuclear battlefield use or a nuclear warning shot, that seems to me the modal outcome. And we didn't have that.

SPENCER: This is reminding me of a strange conversation I once had with a very wealthy person, where they were telling me about the investment strategy they use and how they almost went bankrupt. And so this is a huge amount of money, and they were running this investment strategy where they would buy options in such a way that 98% of time, they would make money on them. But in 2% of cases, they would lose a ton of money. But then whenever they would lose money, they would double down. So they would literally borrow a bunch of money and double down the bet. And so one time during a financial collapse, they had to double down three times. So they kept doubling their bet three times on borrowed money, and it all ended up recovering. But if things had gotten a little worse, they would have literally lost their entire multi-hundred million dollar fortune in that one investment.

CARL: I think that's exactly the right analogy, that we are basically banking our nation's future, and maybe our civilization's future. We're betting that every year and we believe that the odds are low enough that it's worth doing because we gained some benefits every year by making that bet. But if we ever roll that double zero, we're going to be in a lot of trouble.

SPENCER: This raises a question that people might have, which is: can we really unwind things from here? Sure, a lot of people might agree that if, at the beginning, we could somehow have had this credible commitment where nobody ever builds nuclear weapons, then maybe that would have been better. Some dispute that, but many people think that the world would be better. But then that's a different question. But given where we are, given that now, you can learn about how to build nuclear weapons in a textbook — maybe you can't learn everything, but you can learn the basics — can we ever go back? What is your thought on that?

CARL: I think if we ever were to go back, we would be living in a world that's pretty similar to 1944, in which everyone knows that nuclear weapons are possible — I say everyone; not everyone but many leading physicists — and many industrial nations recognize that it will be possible to build nuclear weapons, but it's going to be expensive, and you might not get there in time, and you're diverting resources from other things, and nobody knows exactly what these weapons can do. So if we were to eliminate nuclear weapons, you can't eliminate the knowledge of how to make nuclear weapons, and you can't change the laws of physics. Physics will always permit this dangerous technology to exist in the world. You need to be pretty confident and live in a different world in order to move to a place where you have none of these weapons and nobody else has them either, but where the potential to build them is there. I think it's possible because I believe that humanity could have a very long future. And I think, given long enough, we will come to the conclusion that it's best not to live alongside these nuclear weapons, and we will find other ways to mediate our differences. But the laws of physics aren't going to change. Someone will always be able to build these weapons. One of the surprising things, in my view, is that there are only nine nuclear weapon states. And that was not believed to be the most likely outcome, especially by the 1960s and 70s. So you have two dozen countries that have pursued nuclear weapons and were very serious in their approach, and others that were kind of hedging as well. Very few of those countries actually crossed the line and built nuclear weapons because they believe they could get their security by other means. It's an expensive commitment.

SPENCER: Do you think that because there are a few really powerful countries with nukes, that actually has disincentivized a lot of smaller states from building them? Whereas if it wasn't, let's say, the United States with dominant nuclear power, maybe a lot of other countries would feel, "Okay, we need nukes because we need to make sure that our neighbors were not that friendly with or some other countries we worry about they don't have nuclear power over us."

CARL: Yeah, that's absolutely the case during the Cold War, in which you have the United States offering protection to its NATO allies and some of its allies in the Pacific, in return for those countries not pursuing their own nuclear weapons program. And you have similar dynamics with the Soviet Union leaning on the Eastern Bloc countries, some of which had explored nuclear weapons. So that was one of the dominant factors for why we don't have more nuclear countries. And that's a product of the Cold War competition. And it's one of the areas where the superpowers actually work together to limit proliferation. Then in the 1970s, you have a dynamic where India tests a nuclear bomb. That freaks out the United States, the Soviet Union, and many other countries because India is not allied with either of those countries and it's doing its own thing and pursuing its security this way. And everybody starts to wonder: are lots of other countries going to develop these weapons as well? And that leads to a real strengthening of the Nuclear non-proliferation regime, which is a set of rules and laws and export control agreements to try to prevent nuclear weapons from spreading everywhere. So that's something of a wake up call within the international community that these weapons might spread. And to go back to your question about modal outcomes, I think nine nuclear weapon states is not the modal outcome. I think it's a little surprising that we were able to control the spread of these weapons the way we were, because this is an old technology. Think about any other technology that was invented 80 years ago, it's basically spread everywhere. And nuclear science is hard. But once it's been demonstrated to work, the principles are not that difficult. It's really just an engineering challenge. There are lots of stocks of uranium everywhere in the world. And since then, we've built research reactors and power generating reactors in many countries that now have access to uranium and plutonium and a scientific base of people who know how to work with these materials. So I think that is one area where we've been surprisingly successful in limiting the spread of nuclear weapons. And I believe that the addition of more nuclear armed states to the equation would, in turn, make nuclear use and nuclear war more likely, because each new decision maker you add, creates new competitive relationships with their neighbors and new opportunities for miscalculation or technical error. So the fact that there were very few nuclear weapon states in comparison to all possible futures, I think that's one of the things that contributed to the non-use of nuclear weapons in the past eighty years.

SPENCER: I've heard some people claim, at least in the past, that it'd be better if all countries have nukes. That always struck me as completely insane, but I'm wondering what's the steel man of that view?

CARL: The steel man is that if many advanced industrial countries were able to develop nuclear weapons, their security would be assured, and nobody would threaten to invade them or mess with their core interests, and the world would become a more peaceful place. And this is the argument that the noted political scientist Kenneth Waltz makes in a famous political science article (that maybe you read if you took political science in college). And it has a certain logic to it, that countries become more cautious in the face of nuclear annihilation. And I do believe that to be true, when you look at the historical record. The problem here is that — well, there's many problems, but one is that — states are not rational actors in the extreme. Leaders make mistakes, they make miscalculations. And for nuclear weapons to be effective, they have to be integrated into a system that allows them to be used only when they're authorized, and never when they're not authorized. And that's a really difficult problem, especially in the face of competition. So you have an adversary that may want to take out your nuclear weapons. Well, how can you ensure that your weapons are safe? It's not an easy problem to solve. So those competitive pressures, I think, lead to some crises. And a lot of the crises we've had around nuclear weapons have been about countries trying to build new nuclear systems and get to a point of security. So the Cuban Missile Crisis was about the Soviet Union putting weapons in a country in order to ensure that Cuba would not be invaded again.

SPENCER: Yeah, if I think about a world where lots of countries have nuclear weapons, I start thinking about these different types of failure modes. One is technological, that a nuclear weapon gets set off by accident. Or, as has happened in the past, that there's a missed detection, where a country thinks it's being attacked with nuclear weapons is wrong, and sends a counter attack. There's the technological error. Then there's the sort of madman concern. What if the person in charge is actually crazy or schizophrenic or is just authoritarian and evil? And then you have other concerns that are just normal human direct concerns where it's like, Country A thinks that Country B is gonna nuke them, and so they nuke them preemptively, but they're actually wrong. Country B wasn't gonna nuke them. But given the information they had, they actually thought that was gonna occur. So I don't see how someone could think that with more of these pairwise relationships, you wouldn't eventually have something really horrible happen.

CARL: Yeah, I think it's really folly to put, as you said, we're rolling the dice every year, the more people are rolling dice every year, the more the chances are that something goes terribly wrong. And based on my reading of the Cold War history, there were both technical errors, and there were problems with people being pre-authorized to use these weapons, even down to relatively junior commanders. And if you run that history again and again, I think you're going to have nuclear use. And the more countries that are doing that, the more dangerous it gets.

SPENCER: We talked about the Cuban Missile Crisis. Some people talk about Stanislav Petrov as someone who may have actually saved the world from nuclear attack just through his good decision-making. Do you buy that? That actual nuclear war would have occurred had Petrov acted differently in that situation?

CARL: Yeah, I celebrate the decision that Petrov made, and we had Petrov day about a week ago. Let me set the scene a little bit. In 1983, the Soviet Union had just shut down a Korean airliner. And we know now from declassified information that they were very concerned about a US and NATO nuclear first strike. The US, when they learned of this, they were like, "How did they think we were going to do this?" But in fact, the Soviets were very concerned about this, and they had installed this new early warning system. Stanislav Petrov was a lieutenant colonel in the Soviet forces. His job was to look at this radar readout and authenticate whether the attack was incoming or not. And when he did, he would pass that up to his superiors, who presumably would make a decision to use the weapons. So on September 26, 1983, he saw a radar output that there were five incoming US warheads. And against the protocols, he decided not to pass that warning up. He said, "This tech doesn't make sense to me, based on what I know of the system, it's prone to error." And shortly later, he was vindicated when it turned out to be light reflecting off clouds. But we know that the Soviet Union had fears of this US pre-emptive attack, and was especially concerned about nuclear decapitation — which is an awful euphemism — but refers to: if you strike the other side's leadership, you might be able to essentially cut-off the head that would then authorize retaliation. So I don't know what the odds are of nuclear war if Petrov passes up that warning, but it's a good thing he didn't.

SPENCER: I think it's really nice that some people have started celebrating Petrov day on September 26 commemoration because what can we better celebrate?

CARL: Yeah, there should definitely be more Petrov statues out there, along with Stanislav Arkhipov, who was the Soviet naval commander who prevented the launch of a nuclear torpedo during the Cuban Missile Crisis. So the captain of the ship had ordered the use of the torpedo, and Arkhipov was the commandant on the boat, and he halted that order. So that's another really close call that was prevented from individual action, a single person sitting in that chair and making the call. And there were times when Khrushchev and Kennedy also made that call. There were other false alerts throughout the Cold War, in which someone had to take information that was coming in and say, "Wait, that doesn't make sense. The stakes are too high. Let's pause for a second."

SPENCER: You mentioned earlier that India developed its own nuclear weapons, and this kind of made a lot of different countries concerned. What was the kind of motivation there? As far as we understand it, what do you think India was thinking at the time? And what can we learn from that in terms of preventing other states from seeking out nukes?

CARL: India had emerged from a period of colonization, where they had been bullied and they wanted to establish themselves, their place as a great nation. And they felt that nuclear weapons would provide them not just security, but status. And they noticed, as many people have noticed that the five countries with permanent seats on the UN Security Council happened to also be the five countries that tested nuclear weapons before 1968 and are enshrined in the nuclear non-proliferation Treaty as the countries that are essentially allowed to have nuclear weapons into the future under that treaty. And so I think part of it was security concerns and part of it was bureaucratic politics and domestic politics. And part of it was a desire for status. And I think there are other countries that may look at the nuclear club and say, "Yeah, well, I don't know if these weapons really matter, but you should get to sit at the big table when you have them; people seem to take you more seriously." I think it's been an issue of status for Pakistan as well, because they didn't want to allow India to have nuclear weapons and for them to not have nuclear weapons themselves. And you could see countries like South Korea, which is protected under US security guarantees, including nuclear security, but may fear that the US won't always be there, and to say, "Well, if North Korea is going to have nuclear weapons, we ought to have them too." So the existence of nuclear weapons in the world is a prompt for other countries to consider these weapons. And that's one of the reasons I think it's surprising that we have as few nuclear states as we do, because a lot of countries have decided that they don't want to go that route, even though other countries have. And it takes a lot to say, "Well, my neighbor has nuclear weapons, but I'm not gonna acquire them, even though we have the technical and economic means to do so."

SPENCER: So it sounds like India, when they developed nuclear weapons, that kind of triggered Pakistan to do it themselves. How do we think about preventing new states from developing them, if that's what you think we should be doing? And also, how do we help ensure countries that, "Okay, you don't need to develop your own weapons because you're actually gonna get the benefits as though you had developed them, even though you're not actually going to do it."

CARL: I think there are two key factors. One, states tend to develop nuclear weapons primarily because of acute security concerns. So the more we can reduce the acute security threats that countries face, the less likely we are to see new nuclear weapon states. But as I said, there's also issues of status, etc. It's important that if a state does cross the threshold and acquire nuclear weapons, that they're not greeted as being legitimate in that pursuit. So the fact that North Korea continues to suffer tremendously, as a result of their pursuit of nuclear weapons, is a good thing. In many ways, they haven't been rewarded for seeking nuclear weapons. They've seen their economy deeply constrained. And that's a message to other countries who want to, in violation of their international commitments, pursue nuclear weapons. But I do think there's a fundamental problem at the heart of this non-proliferation regime, in that it separates the world into haves and have-nots. And there's virtually no other international treaty in the world that has that kind of delineation between countries that are allowed to do something and countries that aren't. And so, as long as there are countries that have nuclear weapons, that will be an impetus for countries to pursue them. Right now, it's expensive and difficult to get nuclear weapons, because we have built up this international non-proliferation regime. And it's treaties that countries agreed to. Those treaties are backed by verification measures through the International Atomic Energy Agency. There are also export controls in place to keep countries from taking civilian materials, acquiring them, and then using them for a nuclear weapons program. And we're at the point now, where there's really only one country that seems to be close to developing a nuclear bomb, and that is Iran. So Iran would be the most likely 10th country to add to that list. Under the Joint Comprehensive Plan of Action, there were a lot of inspections and constraints on the Iranian nuclear program. But after the Trump administration pulled out of that deal, those constraints have gone away. And there's now this very contentious period where Iran tries something, everybody gets upset, but they move forward and each year they get a little closer to getting the bomb.


SPENCER: What is your thought about how the world should handle Iran seeking nukes? And also, what do you think is sort of driving the motivation for them right now?

CARL: I think security and status are the primary motivators. And they see themselves as a very important civilization and representing the Shi'ite faith. And they have also seen some of their neighbors invaded by the United States, including Iraq and Afghanistan. And they have heard threats by US presidents about the use of weapons against them. They're in a very dangerous neighborhood, where they don't just face the United States but they also have Saudi Arabia and Israel and other countries around them. It's a dangerous neighborhood. They've also committed a lot of resources to this path. And so, there's a sunk cost fallacy going on there where, "Are we really going to give this up after suffering so much and spending so much to acquire this?" There are also probably people in Iran who legitimately want nuclear energy and see that as a really important thing. So their program is dual use: they're moving forward with a nuclear energy program but it also has the potential to be a bomb. And so, there's a variety of motivations. I think that the best approach right now is different from the best approach 20 years ago, where you may have been able to really constrain Iran's nuclear program tightly. They've moved so far along that path, that the only way you're going to tightly constrain their nuclear program is through war. And I think that's something that nobody wants. Iran is a member of the Nuclear Non-Proliferation Treaty. And they have certain obligations under that treaty, including reporting certain things to the International Atomic Energy Agency. Unfortunately, those agreements allow for a lot of latitude, and there's a lot of gray area in terms of what countries can do. So, I think we should try to make it as difficult and costly for Iran to acquire a nuclear weapon, because I think that the world is a more dangerous place if Iran is nuclear armed. But there's only so much you can do. Because if a country is really set on getting nuclear weapons, they will have the technical means to do so. And so the only option then would be military action.

SPENCER: What about a combination of a kind of carrot and stick where a whole bunch of other countries in the world say, "Hey, if you don't develop this, we'll give you this reward. And if you do finish the development, we're going to give you this big punishment." Obviously, this is like a really obvious idea but I'm just wondering, why can't that work?

CARL: Well, that is the approach that the Obama administration took with this Joint Comprehensive Plan of Action, which essentially provided Iran a pathway to the civilian benefits of nuclear energy, while tightly constraining parts of their program that could be used for a military program. And in return, it also unlocked a lot of money that was Iran's money that had been frozen in international bank accounts. And I think that approach makes a lot of sense. But of course, it's controversial because there are people who say, "Well, the constraints on Iran's activity are not tight enough, and we shouldn't be rewarding a bad actor by unfreezing their money." And so the domestic political costs in the US and in other countries became hard to sustain. And when the Trump administration came in, they said, "Hey, we're going to take a different approach of maximum pressure. We're not going to do sticks and carrots, we're just going to do sticks." I think ultimately, the solution will be some combination of sticks and carrots, but it's hard to figure out what that formula looks like. It was a very carefully negotiated deal. And I think we're in a more dangerous place now without that deal.

SPENCER: You mentioned the development of nuclear energy. Something that I've actually heard inconsistent information on is how linked nuclear energy development is to building nuclear bombs. I've heard literally opposite views on this. I've heard some people say, "Yeah, if you allow countries to build nuclear energy unrestrained, it's gonna make it easy for them to build bombs." And then I've heard others say, "No, that's completely wrong. In fact, you can build nuclear energy without any risk of being able to repurpose it." So yeah, what's actually the truth on that?

CARL: Yeah, it's complicated and nuanced. So nuclear reactors themselves pose very little risk of proliferation. What is the risky part of the nuclear enterprise is what they call enrichment and reprocessing. So enrichment is when you're making nuclear fuel. You're taking unenriched uranium and you're enriching it up to U-235. And if you enrich it to 4%, it can be used in a nuclear reactor. If you enrich it to 90%+, it can be used in nuclear bombs. And the equipment that's used to enrich it to 4% looks an awful lot like the equipment used to get to 90%. On the other end is reprocessing. This is taking spent nuclear fuel, or used nuclear fuel, and running it through a chemical process to isolate the Plutonium. Plutonium is a really good material for use in a nuclear bomb, but it also has use in nuclear reactors. It's very energy dense and there are types of reactors that run on plutonium or run on a mix of uranium and plutonium and a mixed oxide fuel. And so, this uranium enrichment and plutonium reprocessing are the dangerous parts of the nuclear fuel cycle. It's not people running nuclear reactors. So, if every country in the world were running nuclear reactors, there would be very little increased risk of proliferation. However, if many countries start to enrich their own nuclear fuel, or reprocess the fuel that leaves the reactor, that is essentially building bomb-making facilities in every country that does that. That's what we're concerned about Iran doing, for example, is building this enrichment facility. North Korea built reprocessing facilities and enrichment facilities, and that's how they get their bomb. The A.Q. Khan Network in Pakistan was selling this enrichment process on the illicit black market, and spread it to a bunch of different countries. If you were to have a tightly regulated and well-operating international market for fuel, and a process to take back the used fuel from reactors, and that was an international process that was housed in a country where nobody was really worried about building a nuclear bomb, either a country that already had nuclear weapons or was clear was not going to pursue them, then nuclear energy really becomes de-linked from nuclear weapons. Does that help at all?

SPENCER: Yeah, that's really clarifying, and it also helps explain why people are on opposite sides of this, because maybe they're just making different assumptions about what it means to have nuclear power. Does it imply having the enrichment facilities or does it just imply being able to use the material?

CARL: There are lots of countries that, if you're pursuing nuclear energy for energy independence — if you don't want to be dependent on someone else providing you oil or natural gas — then you probably want to control all dimensions of that nuclear fuel cycle. If you just want cheap, clean energy, then you're probably fine running a reactor. You don't want to mess with enrichment, which is expensive, and reprocessing which is dirty. You would just be happy if someone took your used fuel and took it back and dealt with it right. And you don't need to worry about disposing of it or anything else. So there's some really good proposals out there for an international consortium to take back the used fuel from reactors. And there are good proposals for a fuel bank. And there's one operating now in Kazakhstan. So any country that needs enriched fuel to run their reactor, they can get it from this international entity. They're not dependent on one or two suppliers. This becomes a supplier of last resort, so to speak.

SPENCER: This raises another issue that has always confused me about nukes, which is their verifiability. There's a lot of talk of, "We'll have these inspection programs that will check if countries have nukes." I don't really get this. I know that there's radioactive material. Does that mean that you can somehow get a fingerprint and you can actually tell if it's being developed in a country, even in a secret facility? Because I imagine knowing that a country doesn't have a secret facility just sounds ridiculously hard if there's not some way to detect it.

CARL: Yeah, exactly. It's a challenging problem, and for much of the history of nuclear technology, there have not been very good inspections, either inspection protocols or inspection technology. It's only in the past 15 years or 20 years or so that we've really developed the science but also the authority for the International Atomic Energy Agency to be more intrusive in its inspections, to really take these measurements. So there's a couple things that an inspector is looking for. One, they're visiting, and they're trying to see if anything seems amiss. So like, "What's this thing over here? Why do you need that? What do you have? Also, is there any material that's unaccounted for?"

SPENCER: Who's even visiting? I think I'm a little confused.

CARL: You're right to be confused. It really depends because there are 70 countries that have some level of nuclear activity in their country. And that can be everything from a tiny research reactor, to isotopes that are used in cancer treatment, to a full scale nuclear plant. So the IAEA enters into a safeguards agreement with each of these countries and the country delineates, "Here are our nuclear facilities." And you can come and monitor them. Now, until the 1990s, countries had to declare which facilities they wanted monitored, and every other facility was off limits to the IAEA.

SPENCER: That sounds insane.

CARL: It sounds insane, right?

SPENCER: Yeah. Yeah.

CARL: So, inspection was really weak for most of the nuclear age, and relied on not the IAEA but on really national intelligence to gather evidence that a country was doing something wrong. So here's what happened in 1991. After the first Iraq war, they discovered that Saddam Hussein had a nuclear weapons program, and it was at these facilities that were just over a hill from the declared facilities. So you had the IAEA, verifying the absence of illicit activity at the facilities they could visit, and they would sometimes ask, "What about that building over there?" And the Iraq people say, "Oh, no, that's a military facility. You can't go there." And over time, they became suspicious, but there was nothing they could do about it. And then after the war, they realized that Iraq had a very advanced nuclear weapons program, they probably would have gotten a nuclear bomb within five years or so. And so that led to a change in the way that we do safeguards. So I'm talking specifically about countries that don't yet have nuclear weapons. There are now protocols in place to allow the International Atomic Energy Agency to verify the absence of military activities. And they can take samples, they can look at satellites. But again, there are limits to their authority, and every country is very careful to try to preserve their sovereignty, and they don't want the IAEA mucking around, especially around their military facilities. So that's why I believe that the primary obstacle to preventing more countries from getting nuclear weapons is ensuring that countries don't want them, because if they really want them, they can find a way.

SPENCER: So just one quick point of clarification. So is the idea with Iraq that they actually had a nuclear weapons program back in the 80s but they didn't actually have one in the 2000s when people thought they did?

CARL: Yeah, this is the great irony. They did have a nuclear weapons program and then they ended it, but they kind of pretended that they didn't end it. And so Saddam Hussein was really playing both sides, because he wanted his neighbors to think that, "Maybe he did have this, maybe he did have chemical and biological and nuclear weapons."

SPENCER: Talking about one of the worst bluffs in history. Oh, my gosh.

CARL: It was. It was a massive miscalculation. And it fed into some real motivated reasoning by the George W. Bush administration, because they wanted to deal with Iraq. They didn't want this as a lingering problem. So, Saddam Hussein way overplayed his hand and the Bush administration made some huge errors along the way. The intelligence community made errors, and it was a disaster for everyone involved, especially the Iraqi people. I've been talking about verification of civilian nuclear infrastructure. There's another type of verification that we talk about in nuclear space, and that is Arms Control Verification. So these are countries that are negotiating limits to the nuclear weapons that they deploy. There's currently a treaty between the United States and Russia called the New START Treaty, and this limits the number of deployed warheads of both sides. And here, verification is different. There are some onsite inspections and there are a lot of data exchanges, and this is a way for each side to signal that we're holding to the limits of the treaty. And at various points, countries have alleged that the other side is cheating on arms control agreements, and then it has to be negotiated. But one of the interesting things is, with these treaties, we've only limited the number of delivery vehicles. So you're counting missiles and bombs, rather than the actual nuclear warheads. And that's because the nuclear warheads are very small. It's difficult to verify whether an object is a weapon or not. And so we don't yet have a reliable verification mechanism for looking at warheads. And that hasn't been a limit so far to Arms Control Agreements. But if you ever want to get a world with much lower numbers of nuclear weapons, you're going to have to deal with that problem, because you're going to go from counting delivery systems to counting warheads.

SPENCER: I might be being dense here, but I still just can't wrap my head around how a country can be sure that other countries are not developing nukes. Is there now good detection technology that actually helps verify it? Couldn't a country just find some bunker somewhere and use that to build it?

CARL: They can and they have. And that's one of the reasons why — again, I returned it — it's a little surprising that we have as few nuclear states as we do. But to tell you, if you were to start a nuclear weapons program, let's imagine you just came to power, Spencer. You're feeling a little nervous about your neighbors and you want to start a nuclear weapons program. Well, where do you start? If you have an ally that has nuclear weapons, you might go to them and ask for some help. But if you don't, you're going to need to build a domestic set of scientists who are able to do this. So you want to send them off to universities, probably in other countries, because you don't have any nuclear universities in your own country. And you have to build a cohort, and then you have to believe that those people are going to be loyal to you and not spill the beans about your secret program. So you might want to sequester them away in special laboratories. And then they've got to buy the uranium. Well, you can't buy weapons grade uranium, so you have to buy the type of uranium that you'd use in a nuclear power plant. And then you've got to build the enrichment machinery in order to do that. That stuff is tightly controlled, there are export controls on it. And there's lots of spy networks running around trying to figure out who's trying to buy what. So chances are, you're going to be discovered at some point. And a lot of it is just human intelligence, rather than spy satellites, and people detecting isotopes somewhere, if that makes sense.

SPENCER: Yeah, it does make sense. So do you think most countries would actually get caught if they were doing it, but maybe some small percent could get away with that?

CARL: Yes, that's what I believe.

SPENCER: And in terms of detecting isotopes, is there a good technology that actually works for that, or they're just too many steps around and you get too many false positives?

CARL: No, the science is pretty sophisticated. So the IAEA inspectors, now, if they're invited in or if they have the authority to get there, they will go and take samples, and there are certain isotopes which will suggest that certain activities have gone on. So if you find isotopes of uranium that were enriched to 80%. Well, a country has got to explain that, right? Because you would never get those particles if you have purely a civilian program. And so the other side might say, "Well, these are medical isotopes, or maybe we want to use these for research." Well, does that story hold up or not?

SPENCER: Another thing I've wondered about that's related to this is whether it's getting easier to build nuclear weapons. Because if you think about something like bioterrorism, one of the big concerns there is that biological science is advancing so fast that every year it seems easier to be a biological terrorist to make more deadly compounds more quickly, with less equipment and less knowledge. Is a similar thing happening with nuclear or is it not happening? Or is it just on a much slower curve?

CARL: In general, I think it's getting easier to do anything in the world. Because of the technology for manufacturing and our ability to harness knowledge from different places and integrate it using sophisticated software or AI, every year it gets a little better. The Manhattan Project costs $2 billion and there were something like 100,000 people who worked on this task. It wasn't just the scientists at Los Alamos, it was massive industrial facilities in Tennessee and Washington. Today, you could achieve that same level of production with a much smaller team, much smaller geography, much less money. And I think every year, it gets a little bit easier. So, you need a team with a pretty diverse set of expertise in order to build nuclear weapons, but AI allows fewer people to do more (not just AI, just other advances). But these people are talking a lot about AI, "Would AI make it easier to build a nuclear bomb?" I think it does. At the same time, we talked about detection. It is something of a cat and mouse game because our ability to detect activity anywhere on the Earth's surface is much better than it ever was. And that's obviously true of nations with really sophisticated surveillance technology. But even citizens, our ability to buy commercial satellite imagery to know what's going on in the world, it becomes harder to conceal anything. So you have these two dynamics: one makes it easier to build a bomb, one makes it easier to detect when someone's building a bomb. We should be investing in better detection technology and better governance systems that allow us to intervene if we find someone developing nuclear weapons, because every year it's gonna get a little easier to build a bomb.

SPENCER: This raises a question for me which is, it seems like there's a phase transition when you go from, "You have to be a country to build a new nuke," to, "You have to just be 10 smart people to build a nuke." The latter just opens the door to many, many more potential groups, whether it's terrorist groups or radical groups or religious fundamentalist groups or whatever. So if you look at the kind of cost curve of developing these, are we gonna be, in our lifetimes, living in a world where it could just be 10 people doing it?

CARL: Potentially. I think that if you had a small group of people who wanted to do a lot of harm, there might be cheaper ways to do that than to develop nuclear weapons, specifically biotechnology, but there might be other ways as well.

SPENCER: Because we're screwed on biotech we don't have to worry about nukes [laughs].

CARL: [laughs] I think we ought to worry about both. And there was a big effort starting in the 1990s and it really culminated with this nuclear security summit process that was pushed by the Obama administration. And the goal there was to really make it hard for non-state actors to get access to a nuclear bomb. And the way you do that is by securing all of the weapons' usable material. Well, the problem is there's a lot of usable nuclear materials in the world. Most of it is in the hands of the countries that have nuclear weapons, and not all of it is even accounted for. So there's a real problem there. If a non-state actor were to get nuclear weapons, it would most likely be through the theft or diversion of existing nuclear material, rather than starting from scratch. And we've done a much better job to secure that material over time. There's been a lot of international cooperation in this domain. I think the main fear for nuclear terrorism right now is the insider threat. So some disgruntled jihadist within the military service of Pakistan decides to pass some weapons off to a non-state group that he thinks will be more successful in advancing that goal. That's a real concern.


SPENCER: So as we get towards the end of the episode, I want to make sure we touch on what we can do to make the world safer. So when you think about potentially effective interventions that can help with nuclear concerns, what's sort of at the top of your list and why are you excited about those things?

CARL: I think we're entering a really dangerous nuclear moment, because we have Russia using nuclear threats to prevail in a conventional conflict in Ukraine. And you have a new standoff emerging between the United States and China that will inevitably involve the threat of use of nuclear weapons. So in the face of these dynamics, what can we really do? Well, I think first, we need a failsafe review in the United States and in all countries, to ensure that these weapons are really as safe as they need to be. And so, we need extreme care and caution around the entanglement of conventional and nuclear forces. And we need to understand how our technologies, some of which are highly advanced, may threaten the other side's nuclear weapons in a way that may make us less safe. Second, I think we need to keep the lines of communication open. The US and Russia have a lot of differences right now. But when it comes to nuclear weapons, these weapons represent this shared threat to their entire nations and to civilization itself, and they need to be managed with that in mind. And that was one of the breakthroughs that happened in the 1960s, between Kennedy and Khrushchev, and later between Reagan and Gorbachev. There was a recognition that a nuclear war cannot be won and must never be fought, and that we must think about the existence of these weapons as a shared challenge that we can only work on through cooperation. They're not just military weapons, where having more of them gives you an advantage. They are this shared threat. We need to be careful that we're not deploying, especially high-risk, nuclear systems. So should we be developing missiles that have very short-time of flight, that are ambiguous in terms of what target they're going to hit, and which the other side can't tell whether they have conventional or nuclear warheads on them? That's a really risky and escalatory system. And I don't think the US should be developing those in our arsenal, but Congress has put money back in for the sea-launched cruise missile, so that has those characteristics. Fundamentally, I think we need to return to this notion of nuclear sufficiency. The US has a lot of nuclear weapons, 1550 deployed nuclear weapons plus more in reserve. It's hard to imagine any scenario in which an adversary would risk even a handful of nuclear weapons going off in their major cities. And enough is enough. We don't need to engage in a new quantitative or qualitative arms race, even though China is building up its nuclear arsenal, even though Russia will not be constrained by the New START Treaty starting in 2026. I think the US will retain nuclear sufficiency and should say, "We're not going to run this arms race, if you don't." And I think that allows us to deter adversaries for less money and with less risk. So those are a couple things that I think governments can do.

SPENCER: I think a problem that occurs in this topic is that people hear ideas like that, and they might be really promising ideas, but they just seem like the sort of idea that, "Okay, maybe the president can work on that. Maybe the Senate can work on that." But it just seems so, "Okay, well, what can you do as a person or what can even a nonprofit do that wants to help with this?" Because it just feels like there are so few people that really have the ability to control the kinds of things you're discussing.

CARL: Yeah, in many cases, these are only things that the President, members of Congress, senior advisors can act on. But these are people who respond to incentives. And if they see that people are open to negotiation with Russia and China to prevent nuclear war, even though the strategic situation is really grim, they're going to be open to that as well. So we need to create political space and not punish politicians for engaging in dialogue with adversaries. Second, throughout the nuclear age, the non-governmental community — NGOs and academia — played a really important role in auditing the conventional wisdom in providing new ideas and providing greater sunlight and transparency to what's really going on with these nuclear policies. And absent that, we would likely have much worse outcomes. So as we're thinking about preventing a new nuclear arms race and reducing the risk of nuclear war, we really need a voice for citizens and experts in that conversation. And that's one thing that philanthropy can do. It can support these deep expert voices to weigh in and to simplify and disentangle some of these complicated issues. So that's one of the things we're doing at Longview Philanthropy, helping support the next generation of non-governmental experts and leaders to introduce good ideas and to problematize bad ideas. I think it's really important work.

SPENCER: Besides your organization, are there specific nonprofits that work on this that you'd point to, saying they have some really promising ideas they're pursuing or they seem to be doing stuff that that really might make an impact?

CARL: Well, the Ploughshares Fund has done really great work over the years supporting both research and advocacy on nuclear issues. So I would recommend people check out the Ploughshares Fund. They make it really simple, because they have expert staff on board that allocate the financial donations of their members. You have the Nuclear Threat Initiative that was established by Ted Turner and was chaired by Senator Sam Nunn, and they've been really good at helping policy ideas become policies, by working with people in government and taking good ideas and increasing the maturity of those ideas, and having non-governmental people go into positions of influence in the government in order to execute them. So, they were really important in that nuclear security summit process I mentioned, or in the effort to establish a nuclear fuel bank. And they're also working on some of these failsafe issues. Those are two organizations. There are many others: the Council on Strategic Risks is another, the Arms Control Association, the Federation of American Scientists, the Center for New American Security. There are a lot of these groups that have really strong experts on board. And as some of the funding has been constricted, there's an opportunity for them to do more with just a little bit more resources.

SPENCER: I was surprised when I learned about how small the funding that goes to this. Obviously, the government spends a huge amount of money on nuclear stuff. But in terms of philanthropy that's actually trying to improve this incredibly important problem, can you give us a sense of the size of the philanthropy going on?

CARL: There's a lag in reporting, but we think it's somewhere between $30 and $40 million total in all philanthropy on nuclear weapons issues.

SPENCER: It seems so oddly small. Do you have an idea of why that is?

CARL: I think we forgot about this issue. And if you look at the past 30 years, since the end of the Cold War, we've been in a relatively benign security environment in which nuclear weapons were not front of mind. And people think that the problem is solved, or they think it's unsolvable. And it's not either. The decisions that we make with regard to nuclear weapons, what types of weapons we have, how we plan to use them, how we create safety and security in these systems, those decisions matter a lot. In addition to moving on, I think there are a lot of psychological barriers with dealing with hugely consequential complicated issues like this. It's just easier not to think about them. And as a philanthropist, you want to be funding things that are exciting, that are bringing good positive change in the world. And I think it's really hard to measure progress in this area because a lot of the progress we've made is keeping bad things from happening. I think if you look at the past 80 years, we've been pretty successful in avoiding further nuclear detonations and avoiding the spread of nuclear weapons to every country in the world. That's a success story. But I think it's hard to attribute it to any particular action or grant because these are such big, complicated systems. What do you think? Why do you think people aren't more focused on this issue, Spencer?

SPENCER: I suspect it has to do with the low probability that in any particular year, the world is annihilated from it. And so, even though the expected value of working on it might be high because it's just so bad if it happened, when it's a low probability like that, I think people tend to just sort of round it down to zero. And from the point of view of an individual lay person, it seems pretty reasonable. There are a lot of really bad things that could happen. You're focused on your family and your job and so on. Do you really want to spend a bunch of time worrying about possibly being hit with a nuclear weapon? So it's just hard to make it to the top of people's priorities. But then if it's not at the top of an individual's priorities, it's hard for politicians to prioritize it because, on the local incentive level, they're usually better off just doing what is going to make people satisfied right now. And so you need some kind of additional incentive on top of that, or some commitment, to realize this is a really important problem that we all should have on our radar if we're in the position to make a difference.

CARL: Yeah, there have only been a few moments in the nuclear age where this issue was salient enough that it became a real issue of public concern. And one of those was in the early 1980s with the arms build up. There was a concerted effort. A million people in Central Park, standing up and saying, "We need a freeze to this nuclear arms race." I don't expect that this issue will reach that same level of public salience. I hope it doesn't, because if it does, it means something has gone terribly wrong. But I do think it's important for people to consider this as one of the many issues they consider as part of their portfolio of concerns, and to express that concern to their elected officials. I also think that through individual philanthropy, you don't need to be an expert on nuclear weapons policy, because there are people out there who have spent their lives working on this issue, and have good ideas and want to make them happen. And by contributing to an organization like the Ploughshares Fund or Longview, you can get that money in the hands of the people who really do know this issue. So you don't have to become an expert. We just want to make it really easy for people to make a difference on this issue.

SPENCER: It seems to be like the classic case where most people are like, "Oh, yeah. Of course, it's important that someone work on this." But yet, they're still surprisingly few that make it their thing [laughs].

CARL: Yeah. And it's a tough path to walk for some of the reasons we've discussed, like it's psychologically challenging to think about these issues all the time. But there are people who do it. And I'm concerned because as the field contracts, we risk losing some of those people.

SPENCER: Well, we should all be grateful for those people that wake up every day thinking about nuclear holocaust, so that we reduce the chance that we ever have to experience that. Before we wrap up, Carl, how about doing a rapid fire round where I ask you ridiculously hard questions and you just have to give you a really quick take?

CARL: All right, I'll do my best.

SPENCER: All right, first question. Do you think that right now we're in an elevated risk period for nuclear weapons, with US-China tensions, Russia-US tensions, Iran, North Korea, and so on?

CARL: Yes, I mean, everyone who works on an issue talks about how this is a crucial moment and a moment of elevated risk. But I think, objectively, it is. If you look at the situation in Ukraine, there is the risk of nuclear use there. North Korea has gone from two to twenty nuclear weapons, and they are making threats with those weapons, they're testing new technologies. The situation between the US and China is on a collision course. So yeah, I do think the risk is elevated, certainly to where it was 10 years or 20 years ago, and maybe to the highest point since it's been since the Cold War.

SPENCER: I've heard debates about nuclear winter, where some people say the idea is kind of overblown and other people think, "No. It's actually a really big concern." Could you just very briefly summarize: what is nuclear winter? And then, how overblown or realistic do you think it is?

CARL: Nuclear winter is a theory that emerged in the 1980s that posited that the effects of a nuclear war would include lofting soot, massive amounts of soot, high in the stratosphere where if it once it's high in the stratosphere would stay there for a very long time. It would reduce the amount of sunlight hitting the Earth and would lead to crop failures, and could essentially shroud the earth in darkness for a long time, and could potentially lead to human extinction. So that theory was initially put forward. Some of the initial numbers were flawed, but the core mechanism has been validated and subsequent climate models show that this is something we should be concerned about. Now, the devil is in the details. It really matters how the weapons are used, how much soot is lofted, how high it goes, how does the world respond to it, and how long does it remain in the atmosphere? I think it's really hard to know the answer to all those variables. But we should be concerned, not only with the first order effects of nuclear war, but also the second order effects because it would lead to massive disruptions in a variety of areas. And one of the mechanisms that could do that are through these nuclear winter or nuclear autumn effects. The latest scientific models do validate that this is something we should be concerned about. But the extent of that concern really depends.

SPENCER: A related question: what's the chance that full scale nuclear war would actually wipe out literally every single human? Because obviously, it'd be incredibly awful if 99% of humans got wiped out. But from some people's point of view, it would be far worse if 100% got wiped out because then there would be no humans forever, there'd be no civilization, all the value would stop. So yeah, do you think that even is plausible or does that sort of seem impossible?

CARL: I think it's implausible unless you consider the extreme nuclear winter scenarios, which based on my understanding of the science, are just very unlikely, unless there's lots of stuff that we just don't understand. So the idea that nuclear weapons could extinguish all life on Earth doesn't seem likely to me. I think the second and third order effects would be devastating, and it would put humanity on a different track because I don't think the first nuclear war would be the last nuclear war either.

SPENCER: Do you ever worry about developments in fundamental physics? If we look back, before we knew about the possibility of nuclear power, we didn't know that technology or science advancement could create something this devastating. Is it possible that we're gonna, one day, invent something even worse than nukes, and we just don't see it around the corner, just like nuclear weapons weren't seen around the corner?

CARL: So in the movie Oppenheimer, they are discussing some calculations they have run that suggest there's a chance that the first nuclear detonation could ignite the atmosphere and lead to the end of all life on Earth. As it turns out, that's not the case, fortunately. You also have to remember that we went 40 years or so before anyone even surfaced this theory of nuclear winter. So we're constantly learning new and dangerous things about the world. So Spencer, to answer your question, I don't worry about the laws of physics, but maybe I should because Fermi Paradox is out there. There don't seem to be a lot of other civilizations that exist in the universe and there may be some obstacles to our survival.

SPENCER: Another very difficult question. So it's been much debated whether the United States detonating atomic bombs on Hiroshima and Nagasaki was really "necessary" for ending the war. Some people say that neither of them were necessary. Some say that maybe one of them was justified, but not the second one. What are your thoughts on this?

CARL: Well, the Soviet Union was about to enter the war. And at that point, Japan would have known that the war was essentially over, and Japan had been essentially defeated at that point. But there were some bitter-enders who probably would have fought to the last man. So the question is, at what point would the Emperor have decided to surrender and under what conditions? I believe that the war could have ended without the use of nuclear weapons, but I don't think that was ever a realistic possibility, because the United States had developed these weapons and wanted to use it to save the lives of US service members, to end the war, and to demonstrate this new technology they had to shape the post Cold War order by showing the Soviet Union that they had this trump card. So I think that we can imagine alternate histories in which the bomb wasn't used, but I think once it was developed, it was virtually inevitable that at least one bomb would have been used. Now, the Nagasaki bomb was used three days after the Hiroshima bomb, and Japan was still making sense of what happened. There were already some conditional surrender proposals that had surfaced at that point. So I think that we could have avoided the use of that second bomb, which killed over 70,000 people. But historians will debate this forever.

SPENCER: So one concern that people have about nuclear weapons is that the decisions that decision-makers have to make around them can be incredibly tense and difficult on short timelines. So for example, a decision maker may have to decide whether to initiate a counter attack, if they see on the radar that nuclear weapons might be heading towards their country. How can we help prevent issues that arise from these kinds of short timelines related to nuclear weapons?

CARL: This is one of my fundamental fears. People don't make decisions well under extreme time pressure, especially when the stakes are high. And we should be doing everything we can to increase the amount of time that leaders will have to make that choice. So that means investing in command and control, and ensuring that we have good information as soon as possible about what's really going on on the ground. But a broader point: that time pressure is somewhat self-imposed because the United States and Russia, at least, have a secure second strike capability, which means that even if the adversary attacked with their best shot, they would be able to retaliate at their time of choosing. And so in some ways, this time pressure is self-imposed. We should remove that from our policy. So one way to do that would be to remove the intercontinental ballistic missiles from the Arsenal because they are one of the systems that's driving this need to respond quickly. The US submarines are essentially undetectable and could provide a secure second strike under all circumstances. So there's the decision making architecture, but there's also the nuclear architecture, and both of those could be changed in a way that makes us safer.

SPENCER: Carl, thanks so much for coming on. This is a fascinating conversation.

CARL: Yeah, thank you.


JOSH: A listener wanted to know what you thought about the following question from Clearer Thinking's life changing questions program. Summarized in just a few sentences, what is your life story?

SPENCER: There are a lot of ways to talk about one's life story. You can talk about it very abstractly or concretely. Or you can say, "Well, first I was born in the city and I did this thing, etc." But I tend to lean towards more abstract. And so when I think about my life story, I think of it as the story of someone who is very technically inclined, like I love mathematics, I love computer science, but my real passion is psychology and trying to understand how human psychology works. That's really my life's focus. And so, I think of my life story as being someone who comes in with mathematical and computer science-based tools, but applying them to the very squishy topic of understanding human nature.




Click here to return to the list of all episodes.


Sign up to receive one helpful idea and one brand-new podcast episode each week!

Contact Us

We'd love to hear from you! To give us your feedback on the podcast, or to tell us about how the ideas from the podcast have impacted you, send us an email at:

Or connect with us on social media: