Nuclear Winter with Ann Druyan and Brian Toon

Summary

StarTalk Radio: Nuclear Winter with Ann Druyan and Brian Toon
Released: July 4, 2025
Host: Neil deGrasse Tyson
Guests: Ann Druyan, Brian Toon
Award Mentioned: Future of Life Institute Award

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1. Episode Introduction

Neil deGrasse Tyson welcomes listeners to a special archival episode of StarTalk Radio, focusing on the critical topic of nuclear winter. He introduces the co-host, Chuck Nice, and announces that the episode features two recipients of the Future of Life Institute Award: Professor Brian Toon, a co-author of the original nuclear winter paper and former student of Carl Sagan, and Ann Druyan, Carl Sagan's widow and longtime collaborator.

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2. Understanding Nuclear Winter

Neil deGrasse Tyson begins by contextualizing the concept of nuclear winter, a term that gained prominence during the Cold War era. He explains that nuclear winter refers to the severe and prolonged global climatic cooling effect hypothesized to occur after widespread firestorms following a nuclear war, potentially rendering life on Earth extinct.

"[...] because there's the Future of Life award and this year's award goes in part to Carl Sagan. And Carl Sagan has not been with us. He died back in '96. And so Ann, you will be receiving this award on his behalf."
— Neil deGrasse Tyson [04:11]

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3. Ann Druyan's Perspective

Ann Druyan shares her insights on the resurgence of nuclear winter concerns in the contemporary geopolitical landscape, particularly referencing recent nuclear tensions involving figures like Putin.

"I fear that nuclear winter could be all the rage now too because of the instability of our human social organization and of course because of the flirting with nuclear war that that Putin has done recently."
— Ann Druyan [05:05]

She discusses the historical context of the 1980s when there were approximately 60,000 nuclear weapons on high alert, creating a precarious global hostage situation. Ann highlights the collaboration with Carl Sagan and their collective efforts to communicate the dire consequences of nuclear warfare to the public.

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4. The Original Cosmos Connection

The conversation delves into the influence of the original 1980 Cosmos series, co-produced by Neil and Carl Sagan, on shaping public consciousness about climate change and nuclear threats.

"If we hadn't been pumping all this carbon dioxide and other greenhouse gases into the atmosphere, the scientific forecast for the planet was great climate for the next 50,000 years."
— Ann Druayan [12:30]

Ann emphasizes Carl Sagan's deep understanding of planetary science, referencing his PhD thesis on Venus and its runaway greenhouse effect, which served as a cautionary parallel to Earth's climate vulnerabilities.

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5. Brian Toon Explains Nuclear Winter

Professor Brian Toon provides a detailed explanation of how nuclear winter was conceptualized and its scientific underpinnings. He recounts the initial studies on volcanic eruptions and their climatic impacts, which later informed the nuclear winter hypothesis.

"Human beings would barely be in broad daylight. Middle of the day, it would look like a moonless night."
— Brian Toon [26:35]

Toon describes the catastrophic aftermath of a nuclear exchange, including massive plumes of smoke reaching the stratosphere, blocking sunlight, and causing global temperatures to plummet. This scenario would lead to widespread agricultural collapse and mass starvation.

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6. Scientific and Political Reactions

The episode explores the mixed scientific reactions to the nuclear winter theory. While many scientists supported the findings, prominent figures like Freeman Dyson criticized the hypothesis without engaging with the actual research.

"Freeman Dyson, who was a notable physicist, lots of interesting ideas, who likewise said stupid things about it, having never read the paper either."
— Brian Toon [46:04]

Despite initial government censorship and attempts to suppress the research within agencies like NASA, Carl Sagan played a pivotal role in disseminating the findings to a broader audience, including influential political leaders.

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7. Impact on the Cold War and Beyond

Brian Toon discusses the significant impact of the nuclear winter theory on Cold War dynamics, particularly in influencing treaties aimed at reducing nuclear arsenals.

"There was the Intermediate Range Nuclear Forces treaty in 1986 between Ronald Reagan and Gorbachev, which basically tried to get rid of the missiles in Europe and it started a build down of nuclear weapons."
— Brian Toon [56:45]

Both Reagan and Gorbachev acknowledged the scientific findings, leading to policy changes that have largely persisted, although recent developments under administrations like Trump's have seen attempts to undermine these efforts.

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8. Modern Implications and Current Threats

The discussion shifts to contemporary issues, highlighting the ongoing development of advanced, less controllable nuclear weapons and the risks they pose due to reduced decision-making times and increased automation in weapon systems.

"The problem is that we're advancing to this state where human beings are not going to be able to control the weapons because the warning times are too short."
— Brian Toon [59:24]

Toon raises alarm over the 8,000 nuclear weapons currently maintained by the U.S. and Russia, emphasizing that the sheer number ensures mutual destruction rather than strategically controlled limitations.

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9. Overcoming Scientific Communication Barriers

Neil deGrasse Tyson and Ann Druyan reflect on the challenges of effectively communicating scientific threats to the public and policymakers. They stress the importance of storytelling and public engagement in fostering a scientifically informed society.

"If we're going to make our way out of this mess, it's going to be with that coalescing community of people who care about the future of life and the state of this gorgeous pale blue dot."
— Ann Druyan [62:57]

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10. Concluding Thoughts and Hope for the Future

Ann Druyan concludes the episode with a hopeful message, emphasizing the power of global communication and the collective will to preserve life on Earth.

"My hope is based on the fact that all of us are communicating at the speed of light right now, with people all around our planet, there is a coalescing community of people who have access to more information than at any other time in the history of the world."
— Ann Druyan [62:57]

Neil deGrasse Tyson wraps up by acknowledging the ongoing relevance of Carl Sagan's work and the importance of continuing to advocate for scientific awareness and policy change to prevent nuclear catastrophe.

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Notable Quotes with Timestamps

• Neil deGrasse Tyson [04:11]:
  "Ann, you will be receiving this award on behalf of Carl Sagan, Carl Sagan's widow and longtime collaborator."

• Ann Druyan [05:05]:
  "I fear that nuclear winter could be all the rage now too because of the instability of our human social organization and of course because of the flirting with nuclear war that that Putin has done recently."

• Brian Toon [26:35]:
  "Human beings would barely be in broad daylight. Middle of the day, it would look like a moonless night."

• Ann Druyan [12:30]:
  "If we hadn't been pumping all this carbon dioxide and other greenhouse gases into the atmosphere, the scientific forecast for the planet was great climate for the next 50,000 years."

• Brian Toon [46:04]:
  "Freeman Dyson, who was a notable physicist, lots of interesting ideas, who likewise said stupid things about it, having never read the paper either."

• Brian Toon [56:45]:
  "There was the Intermediate Range Nuclear Forces treaty in 1986 between Ronald Reagan and Gorbachev, which basically tried to get rid of the missiles in Europe and it started a build down of nuclear weapons."

• Brian Toon [59:24]:
  "The problem is that we're advancing to this state where human beings are not going to be able to control the weapons because the warning times are too short."

• Ann Druyan [62:57]:
  "My hope is based on the fact that all of us are communicating at the speed of light right now, with people all around our planet..."

---

Final Thoughts

The episode underscores the enduring relevance of nuclear winter as a concept in understanding the catastrophic potential of nuclear warfare. Through the collaborative efforts of scientists like Brian Toon and communicators like Ann Druyan, the podcast highlights the critical need for continued advocacy, scientific research, and public awareness to prevent global annihilation and preserve the future of life on Earth.

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Keep Looking Up!

Transcript

[Ann Druyan]

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[Chuck Nice]

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[Neil deGrasse Tyson]

Hey, start talkings Neil here. You're about to listen to an episode specially drawn from our archives to serve your cosmic curiosities. Check it out. Welcome to StarTalk, your place in the universe where science and pop culture collide. StarTalk begins right now. This is StarTalk Talk. I'm your host Neil Degrasse Tyson, your personal astrophysicist. Today's topic is nuclear winter. You might have remembered that from some decades ago, old timers word that came out and it changed geopolitics. People realizing that not only are there no winners in a nuclear exchange, maybe all of life on earth would be rendered extinct. I've got with me of course, my co host Chuck. Nice Chuck.

[Chuck Nice]

Hey Neil, how are you?

[Ann Druyan]

Hey.

[Neil deGrasse Tyson]

Yeah, good, good, good. Like I was around and cognizant and watching news stories and science stories when this was a big deal because we were still in the cold war. So why are we going there? Because there's a place called the Future of Life Institute that gives an annual award to people who by their actions or their research or decisions or their influence have managed to preserve civilization in ways we should all be thankful. And we have on today's program two of this year's recipients of that award for their participation in the Nuclear Winter project. We first have Professor Brian Toon, who we're going to get to in our second segment. He is a former student of Carl Sagan's and was one of the co authors on the original Nuclear Winter paper. We also have who will be accepting the award on behalf of Carl Sagan, Carl Sagan's widow and longtime collaborator, Ann Druyan. And of course, Ann Druyan is a Emmy and Peabody award winning writer, director and producer and she's also the creative director of NASA's Voyager Interstellar Message. Oh yeah, these are the signals we're trying to give to aliens, tell them who we are and have him not kill us. And she's a longtime friend and collaborator of mine, Andrea. Welcome back to StarTalk.

[Ann Druyan]

It's great to be back with you, Neil, and you, Chuck, too.

[Chuck Nice]

Well, thank you. Now let me tell you, Neil, Ann just became my favorite guest of all time.

[Ann Druyan]

That was easy.

[Chuck Nice]

Yeah, because no, because you know, I'm not here to be acknowledged. But I appreciate it.

[Neil deGrasse Tyson]

But that was still a little barred, Chuck. It just. So what's going on here is that there's the Future of Life award and this year's award goes in part to Carl Sagan. And Carl Sagan has not been with us. He died back in 96. And so Ann, you will be receiving this award on his behalf. You are a 35 year collaborator, Carl Sagan. You were there in the middle of all of this, publishing books with him, co producing Cosmos with him, the original one from 1980. And so, and you would like you're the right person to have to begin this conversation about what was going on in the early 1980s with this whole notion of nuclear winter. Cause I know you were Carl's most trusted collaborator on all fronts. And so what was going on back then?

[Ann Druyan]

Well, you know, you started by saying that nuclear winter was all the rage back then. And I fear that nuclear winter could be all the rage now too because of the instability of our human social organization and of course because of the flirting with nuclear war that that Putin has done recently.

[Chuck Nice]

Yeah.

[Ann Druyan]

But back in the 1980s, there were some 60,000 nuclear weapons on hair triggers around the Earth. It was a kind of epic hostage drama in which everyone on Earth was held hostage to a nuclear arms race that was out of control and to the fact that the superpowers were engaged in ratcheting up technologically as well as numerically of nuclear weapons.

[Neil deGrasse Tyson]

Just to remind people back then there were Only two superpowers, the United States and the Soviet Union. Today we might think of China as one, but definitely not.

[Ann Druyan]

But China, even back then was a, you know, had some nuclear weapons.

[Chuck Nice]

Yeah, they were a player in the game.

[Ann Druyan]

They were definitely a player in the game.

[Neil deGrasse Tyson]

Yeah.

[Ann Druyan]

As well as a number of other countries. And so while we were already deeply concerned and Carl was spreading the alarm about climate change even back then, at the time, because we hadn't begun to see so palpably the effects of, of climate change that we see now, the danger of nuclear war was the great shadow on our future. And there was research being done. And your next guest will speak to it far more knowledgeably than I can, modeling with what we would consider now primitive computer capabilities, the effects of what a nuclear war would be. There had been studies of the volcanic effects. For instance, the effects of the Tambora volcano in 1816, which was also called 1800, and almost freeze to death because of the long winter then. And so there were intimations. Two scientists named Crutzen and Birx had done some research in this area. There were intimations that there would be unforeseen consequences of a nuclear exchange, not just the immolation of millions and the burning of cities and the horrendous nightmarish scenarios that were already known, but then also the long term consequences. And of course, Neil, you said that. I'm accepting this on Carl's behalf. I am deeply honored to be doing that. But my role in Nuclear Winter was that it unfolded in my living room. And while we did collaborate on so much, this was really a collaboration between Turco Chun Ackerman Pollock and Carl Sagan. And all credit goes to them for the science and especially I think, to Carl in the area of educating the public on this unforeseen danger. Which, of course, at the time, the defense industry and political establishment had little interest in promulgating this information to the public because it really made them look so bad. They had spent trillions on weapons of mass destruction and hardly anything on researching the consequences of, of their extravagant foolhardiness. And so it's against that backdrop, an intransigent Ronald Reagan who felt that Star wars defense system, you know, shields, could protect us from incoming nuclear weapons and an unwillingness to deal with this evil empire that he saw, as he saw the Soviet Union. And so against this backdrop, nuclear winter unfolds in the scientific community.

[Neil deGrasse Tyson]

So, Ann, I'm just wondering, in the original 1980 Cosmos, were there any tap roots there that you think would have Sensitized you and Carl to sort of rising, trying to rise up to make this message known.

[Ann Druyan]

Oh, absolutely, Neil, I'm so glad you mentioned that, because, remember, just to put.

[Neil deGrasse Tyson]

Time in context here, you would have been working on the 1980 Cosmos in like, 1979 or 1978, and the nuclear winter paper came out a little deeper into the 80s. So this is this 83. So this. This predates it by a few years. Yeah. What do you have to say there?

[Ann Druyan]

You know, Carl, of course, as I mentioned, had been thinking about climate change, and he was familiar with the groundbreaking work that colleagues and friends of his, including Jim Hansen, were doing. Roger Efal, were doing on this fledgling climate science, this area of climate science.

[Neil deGrasse Tyson]

Which was, just to be clear, Jim Hansen, we know him in StarTalk. And you're saying he was at it 40 years ago?

[Ann Druyan]

I believe that's correct.

[Neil deGrasse Tyson]

Oh, my gosh.

[Ann Druyan]

And very courageous. And took a lot of heat because of it, as did Carl, because you mentioned Cosmos, the original Cosmos series twist broadcast in 1980. So in that series, there was episode four, which was called Heaven and Hell, and it was a contrast between the planet Earth and a sister planet, Venus. And Carl had done his PhD thesis in, I think, 1961, on the runaway greenhouse effect on Venus. He was, in fact, the first person, I believe, to know the actual temperature of Venus and to understand what had turned Venus from possibly a clement world. We don't know that for sure yet, but possibly clement, or certainly more clement than it is now, to an inferno, a hellish inferno.

[Neil deGrasse Tyson]

And the thinking for that Venus is the same size as Earth and the same surface gravity, and it's near us in orbit around the sun. And there it is, this hellish fire. Oh, my gosh.

[Chuck Nice]

Not to mention they also had Venusian Exxon, let's not remember.

[Ann Druyan]

Yeah, well, I'm not so sure about that, Chuck. But. But so we were very conscious of what we were doing to. And we said so in Cosmos with Steven Soder, our co writer. We were very conscious of what we were doing to the Earth's atmosphere and that we were inadvertently altering the climate of this planet, which was especially heartbreaking because if we hadn't been pumping all this carbon dioxide and other greenhouse gases into the atmosphere, the scientific forecast for the planet was great climate for the next 50,000 years. Here was this paradise that we evolved to be happiest on of all the worlds in the universe. And yet here we were, mindlessly, thoughtlessly ruining this planet for our civilization. And, you know, you mentioned the Future of Life award, which is the occasion for, for this, this delightful conversation with you guys. And you know, I don't think there was ever a person or to my knowledge, there's never been anyone who took so to heart our responsibility to protect the future of life, as did Carl Sagan. And so just to tie it up, I'm really thrilled that he is getting this award. I think it's wonderful and very just.

[Neil deGrasse Tyson]

And anyone who's seen any of the cosmos, no one is saying, okay, I have to sit through a documentary. Again, the word documentary isn't even in the conversation because Cosmos sits separate and apart from every other attempt of science professionals and educators to communicate science. What is the secret sauce that distinguishes Cosmos from all other documentaries we've ever seen?

[Ann Druyan]

Well, thank you, Neil. Well, the point always was from the beginning, for me as a non scientist, as someone who was told by a science professor that I was ineducable, someone who felt very much excluded from science, alienated from science, was as an outsider, it always seemed to me, and, and luckily I was working with someone who was an insider, but who also. Two insiders, Carl and Steve, who also understood and felt the power of the scientific perspective as a transforming emotional, spiritual experience. Be completely cold and dispassionate as you gather the evidence, analyze it, create your hypothesis, no emotion in any of that. But once you have some findings, some tiny, incomplete insights into how nature is put together, feel it, take it within, take it to heart. And I think that's the biggest big danger about the future of our lives and our children and grandchildren is that if we keep this concept of science as a jumble of amazing facts that are somehow external to us and don't take it to heart as deeply as the most spiritual feelings we've ever had in our lives, then we are doomed. Because it's not separate. It's the story of us and everything that we value and love. Only it's a more disciplined approach to trying to find out a little bit of truth, not any absolute truth. And just finally, I mean, this is my passion of my life.

[Neil deGrasse Tyson]

You can't top that, Anne. How could you can't go along like that.

[Chuck Nice]

And in conclusion, someone who's earned these.

[Ann Druyan]

Feelings as an outsider, as a person who has no credentials, but has really just had great teachers who have opened this way for me and that is, you know, whenever you feel and think it's, I'm all for it. I don't want to take that away from anybody. But for me personally, the most soaring spiritual experiences of my life have been this kind of way of loving nature, which is to look at nature not with your projections and your fears and your fantasies, but to be as cold eyed and as real as you possibly can be in order to know it and still love what you see.

[Chuck Nice]

Well, I'm sure that person who told you you were ineducable, they're short sighted. Rudeness. They're certainly choking on it right now, aren't they?

[Ann Druyan]

Well, I think he's probably dead.

[Chuck Nice]

Oh, okay.

[Ann Druyan]

On the happy side.

[Chuck Nice]

Wait a minute. And once again, you win.

[Ann Druyan]

Yeah. Really? Absolutely. I know I've been very lucky. Ridiculously lucky.

[Neil deGrasse Tyson]

So we're going to take a break. When we come back, we're going to bring in Professor Brian Toon. And Brian is a professor at the University of Colorado at Boulder and he was a graduate student of Carl Sagan. And Professor Thun is also getting the Future of Life award for his role in the research that told us all about nuclear winter and why we should care. When we come back.

[Unknown Speaker]

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[Ann Druyan]

Hello, I'm Thinky Brooke Allen, and I support startalk on Patreon. This is startalk with Nailed Grass Tyson.

[Neil deGrasse Tyson]

We're back. Startalk. I got with me Chuck. Nice. And the topic today is nuclear winter. And not only that, the Future of Life award is something given annually to people who had something to do with protecting civilization. And we have in this segment Professor Brian Toon. Brian was a co author with Carl Sagan in a research paper in the 1980s highlighting nuclear winter, what it means and why it is important not only scientifically but geopolitically. So, Brian, welcome to StarTalk.

[Brian Toon]

Thank you.

[Neil deGrasse Tyson]

So, you know, we come as a, as a cold war, baby, as am I. And anyone in this call is we kind of knew nuclear war was bad. Okay. And made it clear. Yeah, you, you, you're immolated if you're in ground zero where the bomb strikes and all your buildings are leveled. So this was kind of well known or, or at least well feared. And now you came up with another reason to fear nuclear exchange. So how does tell me exactly how nuclear winter works?

[Brian Toon]

Well, let me tell you how we discovered it in the first place. And so what happened at the time I worked for NASA and we were studying things like how volcanic eruptions could change the climate, which was partly triggered by Carl's interest in the wave of darkening on Mars, which people thought might be vegetation advancing over the Martian surface, but really he thought, well, more likely dust storms. And so that got me into studying dust of the atmosphere, which people thought could come from volcanoes, which turned out not to be right either. It turned out to really sulfuric acid is what they put in the atmosphere. Anyway, in about 1980, I was studying volcanic eruptions and the climate of the Earth, supersonic transports, their effect on the Earth's climate and other kinds of.

[Neil deGrasse Tyson]

This is the commercial airplane, the sst, Right, Exactly. Transport.

[Brian Toon]

Yeah, yeah, exactly. And we had thought about Nuclear weapons, and hadn't really thought of any way they could do anything terrible to the climate. But then the Alvarez group at Berkeley discovered that an asteroid had hit the earth 66 million years ago and killed the dinosaurs. And so we started saying, whoa, wow, how did that happen? And we concluded, well, this is because of the debris in the atmosphere from the impact.

[Neil deGrasse Tyson]

Well, just to be clear, an asteroid hitting the Earth kills any dinosaur where the crater is, but this one killed all the dinosaurs on all of the Earth. So that was the big conundrum here. How do you kill everything if the. If the impact is local to some region? Okay, go on.

[Brian Toon]

And it killed about 75% of the species on the planet and not just the dinosaurs. So in any rate, I gave a talk about this early on because there is huge skepticism about this idea of. A geologist said, no, no, this violates all the tenets of geology. Nothing catastrophic ever happened. It's all just a continuum. And actually asteroids fit into that continuum because the moon formed from an asteroid impact on the Earth about the asteroids, about as big as Mars. And there has been constant collisions. We had one a few years ago in over Russia that was quite large and hurt thousand people or more. So it is a continuum. But nevertheless, people were skeptical of that. And so I evaluated how the dinosaurs might have been killed by that. And someone said, oh, what about nuclear wars? And so we went back and I called up Richard Turco, who I knew worked for a company that knew something about nuclear weapons. And I said, well, maybe we should look into this. So he and I started doing some calculations of dust in the atmosphere and said, wow, it could actually do something bad. And then Crutchen and Burke's thought about forest fires being started by a nuclear war. And, you know, Rich said, no, no, that's not it. Cities are set of fire. You have a big nuclear explosion and you'll set the city on fire. And this is what happened in Hiroshima, in Nagasaki. In Hiroshima, there was a firestorm that started a few hours after the nuclear explosion released a thousand times as much energy as a nuclear explosion to burn all that material. And it produced a plume of smoke that rose up into the stratosphere. And so we realized from that that you burn all these cities around the world, you're going to put smoke in the atmosphere, and smoke is very absorbing. Anybody who's looked at their fireplace knows there's all this black junk all over it. It's called black carbon, and it absorbs sunlight very well. And so we did these calculations and found that the sunlight would be diminished at the surface of the Earth. Now we think it would be so dark at the surface of the Earth that it'd be like a moonless night. Human beings would barely be in broad daylight.

[Neil deGrasse Tyson]

Would be like a moonless night.

[Brian Toon]

That's right. Middle of the day, it would look like a moonless night. And because of that, it's just like every other night. The temperatures start dropping. It's just like winter. You let the light go down for a long time, the temperatures keep dropping. And so we found that you'd have sub freezing temperatures in the continental areas all over the Earth. And when we found this, we knew Carl was interested in this problem. And Jim Pollack and I were both students of Carl. And so we called up Carl and said, you know, hey, Carl, you want to, want to work on this problem with us? Carl's interest came from a different place, which is very interesting. Carl was trying to figure out how many civilizations there were in the galaxy we live in. And he calculated how many stars there were and how many planets around the stars and so on and so forth. And at that time, all those things are guesses. Now we know how many planets there are around the average star. He guessed pretty well. And so we're pretty far down in that chain of the Drake equation trying to figure out how many civilizations there are. And the answer is a lot. And Carl was really bothered by that. He said, well, where are they? Why aren't we communicating with them? Why aren't they visiting us? And he concluded the answer was that because they destroyed themselves very quickly, as soon as they developed the understanding of atoms and the energy that's en masse, they would start fighting among themselves and destroy their civilizations. And he was concerned that that would be what the fate of the Earth would be. And so to Carl, and he has a famous quote that it would be elementary planetary hygiene to get rid of nuclear weapons. So Carl came in from a different direction than the rest of us.

[Neil deGrasse Tyson]

Plus he already had a following. So if he gets to speak on this, on his platforms, this could work its way into geopolitics in every way that it should, because we know none of those folks are reading the journals that you're publishing in.

[Brian Toon]

Absolutely. So Carl played a critical role in this. You know, he was fairly aware of the science. He understood the science from his work on Venus and other problems. And he'd work with us on other issues like the volcano problem. So Carl understood the science behind this, but his major role was to communicate this idea. The danger of These weapons, you know, I have to say, I. To me, this was just a science problem. You know, I was young at the time, I didn't anticipate the political aspects of this. So I was kind of surprised at the huge interest in it. And I'm likewise surprised nowadays. In the last 10 or 15 years, we've shown, for example, that a war between India and Pakistan could kill billions of people by this, that politicians just showed no interest in that. So we really need a curl in the modern day to try to wake people up to this problem.

[Neil deGrasse Tyson]

But I think we're missing an important link in this chain here. We already know nuclear exchange of nuclear weapons is bad. So why would this get any special attention beyond just saying the cities will burn? How did it work its way into the geopolitics of the day?

[Brian Toon]

So what happens when you burn all these cities? It's just what happened after Hiroshima. And is it the smoke from the burning city reaches the stratosphere? And this matters because if you put stuff in the stratosphere, there's no rain there, so it's not washed out quickly, and the stuff stays in the upper atmosphere for years before it's finally removed.

[Neil deGrasse Tyson]

I gotta add something. So what we're saying there is when you get particles in the lower atmosphere, raindrops nucleate on them and then the raindrop takes it out, clearing the air. But you're saying the stratosphere is too high for that to happen. And once it's up there, it has a very long lifetime.

[Brian Toon]

Absolutely. And so we see this in the modern day. You know, I live in Colorado, down winter, California, it's choking here, summers, all that smoke, you know, but that's, you know, only a couple of days old, and it gets washed out. It doesn't pollute Washington D.C. unfortunately, but you put it in the stratosphere. We've also seen this happen twice in the last two years. Never have we seen this before. But in 2017, there was a fire in British Columbia. But smoke in the stratosphere, we could see it for almost a year. And in 2020 and the new Year's were big fires in Australia, they also put smoke in the stratosphere. We could see that from satellites for more than a year. And we could see not only that, but the smoke rose. The sun heated it, made it warm, and it rose to high altitude, 20 or 30 kilometers. And in our models of nuclear winter, it rose to 80 km, which is way up in the upper atmosphere. So the smoke sits there, it stays there for a long Time, of course, these forest fires that we saw in the last few years, that isn't very much smoke. Whereas you burn all the cities on the Earth or the ones in Europe and United States and Russia is a huge amount of smoke. And that smoke absorbs sunlight and prevents it from reaching the surface.

[Chuck Nice]

So which, which work informed the other more? Because you're looking at the dinosaurs and their nuclear winter and then you're looking at an actual, you know, our, our own self destruction. So which, which came first? Were you saying like, oh, now we look, you know, we had Hiroshima, so we can look back and say, see, we're right about the dinosaurs. Or was it the dinosaur modeling that said, see this is what's going to happen with the nuclear attacks that we'll have.

[Brian Toon]

Well, with the dinosaurs there is a layer in Colorado, you can go down and touch it if you happen to be in southern Colorado left from this asteroid collision. And there's full of asteroid debris, but it's also full of smoke. There's 66 million year old smoke there. And in order to get that much smoke, you had to burn everything on the surface of the Earth, all the trees, all the grasses and even some of it probably that was subsurface. And so the dinosaurs probably largely perished in the fire and the glowing skies from the infalling asteroidal debris. But in the oceans it was pitch black. The plankton couldn't reproduce. And so the oceanic extinctions were caused by the light going away. And of course it got very cold there also. So if any dinosaurs survived the initial fires, they would have died in the cold. And so that's a strong parallel with what happens after a nuclear war.

[Chuck Nice]

Amazing.

[Neil deGrasse Tyson]

So at the end of the day, you don't simply destroy your enemy, you destroy all of the Earth, everything. So that, so that's the, that's the takeaway here, right?

[Brian Toon]

That's the takeaway is if you start a nuclear war, not only do you kill your own people, but you kill everybody on the planet. As I we studied a war between India and Pakistan, which were threatening each other with nuclear weapons. Frequently we thought 50 to 100 million people there would die from the initial blasts. But now we think that a hundred or a billion to 2 billion people around the world would die if there were a war between India and Pakistan because of all this smoke in the stratosphere blocking sunlight. And we think if there were a war between NATO, the US, Russia, probably 5 billion people would die. And the reason for that is that with no sunlight, the temperatures fall. We've Looked at say Iowa and the Ukraine, which are two major breadbaskets, it quickly falls below freezing there. Even in the summer. Every day the mean low temperature is below freezing for several years. You're not going to grow anything in mid latitudes.

[Neil deGrasse Tyson]

By mean low temperature, you mean the average low temperature, right?

[Brian Toon]

Yes.

[Neil deGrasse Tyson]

Commenting on the emotional state of the temperature.

[Chuck Nice]

Temperature feels so personal, Right.

[Neil deGrasse Tyson]

It's so mean temperatures.

[Brian Toon]

Yeah, you probably feel that way. Yeah. So we've looked at the agricultural response of this and it's devastating. Yeah. Across the Earth, we've actually looked at every plant, every country now in the earth. Some countries are very sensitive to this, like Russia. Russia would lose most of its population from starvation in a case like this. And so would the United States and Canada. High latitude countries just couldn't farm in these circumstances. There'd still be some ability to farm in the tropics because it get quite so cold.

[Chuck Nice]

But Brian, I hate to be a self serving, self centered person, but is there a place on Earth where your models say that one might be?

[Brian Toon]

Okay, well, New Zealand and Australia, because they raise a lot of sheep which they export. And so if they stopped exporting their sheep who live on grass, they could eat the sheep and probably not be calorie deficient.

[Neil deGrasse Tyson]

But the rest live way longer than everybody else.

[Brian Toon]

Yes.

[Chuck Nice]

Okay.

[Brian Toon]

People don't realize how vulnerable the Earth is. You know, people have heard this story in the Bible and in the Quran. It's in both books about Joseph advising the pharaoh about bad weather. Pharaoh's dreaming of cows and needs seven fat cows and seven, seven skinny ones. Yeah, exactly. And so Joseph says, give me seven good years, store up grain and you can feed the Egyptians for then seven years afterwards. And the pharaoh does this. Got a longer term than the president and his big hero after 14 years. But that isn't the real world. The real world, there's only 60 days, about two months of grain in storage. You have a global catastrophe from an asteroid impact, from a large volcanic eruption, from a nuclear war. Agriculture is going to shut off. There's about enough food in a city for a week. That's it. You got to bring in more food. There's only enough food around the Earth for 60 days. After that, mass starvation was going to occur and there's not much you can do about it. There's people thinking about, well, maybe we could raise mushrooms, maybe we could harvest kelp. Well, yeah, sure we could if we had time to think about it. But you're only in that 60 days to respond. And if it's a global nuclear war. There's no more oil refineries. There's no more transportation. Most of the science people in the country are trying to figure out how to survive themselves. The agricultural people don't have any fuel anymore. You're not going to quickly solve this problem by doing something different than what you've been doing.

[Chuck Nice]

Well, I am moving to New Zealand and stocking up on shiitakes.

[Neil deGrasse Tyson]

Okay, so we're gonna take a break. When we come back, we're gonna bring Andrean back into the conversation and we just wanna sort of explore the geopolitics of the day. What was the reaction from people, from fellow scientists, from politicians? And just to ask ourselves, how close were we to this catastrophe? On Starclock.

[Brian Toon]

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[Ann Druyan]

If you haven't heard, I have a.

[Brian Toon]

Podcast that's called Literally with Rob Lowe. And basically it's conversations I've had that really make you feel like you're pulling up a chair at an intimate dinner between myself and people that I admire, like Aaron Sorkin or Tiffany Haddish, Demi Moore, Chris Pratt, Michael J. Fox. There are new episodes out every Thursday, so subscribe please and listen wherever you.

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[Neil deGrasse Tyson]

We're back on Star talking about nuclear winter. Why? Because the Future of Life award is going to people who had something to do with first figuring it out. It was real, a real thing to worry about and having the world know about it. We've got here Brian Toon, who's one of the co authors on the original paper for this. And we have Ann Druyan, who will be accepting the Future of Life Award on behalf of Carl Sagan, her longtime lifetime collaborator. Let me just ask both of you, could you comment? What was the initial reaction? Was it one of disbelief? Maybe we can start with the public and Carl's colleagues. Anne, you saw this firsthand, right?

[Ann Druyan]

I did. And what happened was coinciding with the publication of the scientific paper that Brian and Carl and their colleagues published, I think it was. Was it in Science or Nature? Brian? I'm trying to remember which one in Science. Carl published an article in Parade magazine, which was a Sunday supplement in a pre online world, which got to 70 million people in the United States. And so this was an article written for the public and it was revealing heretofore unsuspected consequence of nuclear war. And so, because Parade at that time was so tremendously influential and the reason that Carl and later and together we wrote for Parade magazine was because it was penetration to the readership that was not reading Scientific American or any of the excellent public science communication publications. It was for everyone and in the plainest and most, you know, as always, Carl, tremendously eloquent. It described this consequence that Brian and Carl and their colleagues had discovered. And the impact was enormous. It's been a while since I went through the papers of that moment, and so my impression is a bit anecdotal, but Carl was on the big TV shows of the time, which again, in a pre online culture, were tremendously influential, like Nightline, in which I think he was on 10 or 20 of such programs in a very short space of time, again in the most crystalline possible language, explaining these consequences. And I can talk personally about one perhaps the most impactful reaction to nuclear winter, and that is that Carl was asked to brief the Pope. So we went to the Vatican. He was asked to brief a central Committee of what was then the Soviet Union, the governing body where all the power was in the former Soviet Union. And Gorbachev was the premier, then prime minister. And when it was over, we were told later, the first human ever to walk in space, a cosmonaut named Alexi Leonov, he said that Gorbachev and the other members of the Central Committee looked at each other when Carl was. When Carl left the room, and one of them said, well, it's over now, isn't it? And that is in the midst of Gorbachev making a tremendous effort with Ronald Reagan, trying everything he could think of including, by the way, a unilateral test ban on nuclear weapons that the Russians did, and the United States under Reagan, refused to join. And that led to us being arrested three times at the Nevada nuclear test site, inspired, in fact, by this unilateral test ban by the Russians. And when I was told by another, by a member of the administration, that when Gorbachev came to the White House to see Reagan, he was carrying with him a copy of Carl's article, which had been published in Parade, again to a vast audience and in Russian, simultaneously called Together to Mars. And he was brandishing a copy of this to show Reagan and was summarily rebuffed. Because what Carl was thinking at that time was if we could become involved in a joint venture which would channel all of that testosterone that went into these wars and create a kind of an adventure that Russians and Americans could watch from home and could participate in, in an epic mission to Mars, that there would be a way to work out what seemed like these intractable issues. And unfortunately, Reagan was not at all interested in that. And so here we are.

[Neil deGrasse Tyson]

So, Brian, what was the scientific reaction to these results? Was there criticism? Was there praise?

[Brian Toon]

Well, it was rather mixed. There was initially a group of people who made comments in the press and had never even read the paper, one of whom was the editor of Nature magazine. And he and Carl got into quite a dispute over his comments since he was running the theory down and hadn't even read the paper. There were other people like Freeman Dyson, who was a notable physicist, lots of interesting ideas, who likewise said stupid things about it, having never read the paper either. And so there was a reaction like that. And this is part of a continuing thing where started during the days of the tobacco problems, there's a whole group of people telling you cigarettes were good for you. The same group of people did everything they could to try to make nuclear winter look like there was a problem with it, and then they tried to make global warming look like there was a problem with it. You know, the same group of people as old books written about the merchants of doubt. So there. There was a big thing like that. I think Carl and the rest of us were all called communists in the Wall Street Journal. Dupes of the communists. But nevertheless, most of the science community saw this like a science problem. They set to work to find anything wrong with it that they could. There was quite a few people who worked on it, but it was blocked at the time by the government. And so in NASA, I was told I was going to be Fired. And everybody in my building would be fired if I didn't stop working on this. And we were told, we tried to present a paper about it, and we were forced to withdraw that paper because it hadn't been reviewed. And so that was a really important decision that NASA, the local NASA, made to say the paper hadn't been reviewed, because Carl took that as an opportunity to review it. And so what he did was he sent a copy of the paper, draft paper, around everybody in the world, including to Russian scientists, who immediately reproduced the results with their own models, which are even better than our models at the time.

[Neil deGrasse Tyson]

And again, as Ann said, with very primitive computing compared to today.

[Brian Toon]

Exactly right.

[Neil deGrasse Tyson]

I mean, that's. That was. You do better with 40 years ago.

[Brian Toon]

Better with an iPhone, at any rate, you know. So a couple of hundred scientists got together at a meeting in Boston, I believe, in October. So I recall and debated the science of the problem. And, you know, those people did have continuing interest in it. And there were like two people in the National Science foundation who were allowed to work onto the 10 car. There were some people from the Department of Energy who at that time collaborated.

[Neil deGrasse Tyson]

With other people about ncar. National center for Atmospheric Research. That's correct.

[Brian Toon]

That's correct. But most of the other agencies, including NASA, the science people are told, you can't work on this. Noah forbid anybody and Noah from working on it. So it was an interesting censorship of science at the time, which I've never seen happen on any other issue. But nevertheless.

[Neil deGrasse Tyson]

But that doesn't bode well for science. I mean, did this last a short amount of time? Did it drag on? What did it take for people to come around?

[Brian Toon]

It's still going on.

[Ann Druyan]

Still going on?

[Chuck Nice]

Oh, it's still going on. It hasn't yet.

[Brian Toon]

There's no.

[Chuck Nice]

How is this still going on?

[Ann Druyan]

If I may speak to you, just several years ago, I want to say about four or five years ago, there was what I consider to be a scurrilous article in the New Yorker, of all places, which was called something to the effect of Nuclear Autumn. And what really shocked me, because the New Yorker has always had such a glowing reputation for fact checking, was this uncritically reported nuclear autumn really nothing more than really a comment, not a scientific paper made by a scientist named Steve Schneider many, many years before. And the person who wrote this article and the staff at the New Yorker uncritically published this article which said, you know, that Carl Sagan had made poor choices and that this theory had turned out to be just not A big effect, not a significant effect at all. And it was absolutely horrifying, first of all, because there have been publications in the last 10 years in these same scientific journals that we've been talking about by Alan Robach and others, saying that with greater computer capabilities, the results are every bit as robust as the original scientists of the TAPS paper publish. And if anything, more robust. And so it really hasn't stopped. And again, it's just this casual, smirky casting of Dillo without anyone doing the absolutely critical homework to know what's true.

[Chuck Nice]

So may I ask of all three of you, because, first of all, I hate to say this, but I'm terrified right now because, you know, when you look at what Brian is talking about, which is the story of the dinosaurs and how it directly mimics and mirrors the story of our own destruction, if we so decide to walk that path, and then you think about the people who are naysayers, it seems to me like there needs to be some kind of storytelling that happens to get us back re engaged with this. And, you know, Neil is an incredible communicator and Cosmos, I mean, everybody watches all of them still to this day because it tells a story, right? You know, and Brian just told this story of the dinosaurs that is, you know, truly compelling. What do we have to do to kind of get people to feel like I feel right now?

[Neil deGrasse Tyson]

I can. I can tell you this, that my profession, or science in general, does not reward storytellers. There's no mechanism to promote the communication of science. In fact, I and could take this over in two sentences when I'm done here. Just the time that I spend communicating with anybody is at best neutral to my professional standing. That's at best because there's always somebody saying, well, he should be in the lab or he should be in this, and he should be that. And this is Carl Sagan's whole life, right?

[Ann Druyan]

Absolutely. And I know that if it were possible for him to decide, you know, to do it all over again, he would have done exactly what he did. He followed his bliss. And he felt that this knowledge was such a precious and thrilling and emotionally and spiritually uplifting understanding of nature that how could you not share it with everyone? He used to say, famously, when you're in love, you want to tell the world. And that's how he felt. He worried about the future of a society that aspires to be a democracy, such as we have. If so few of us have the critical faculties, the ability to know when we were being manipulated or lied to, the inability to search more deeply to find out what is real. And of course he wrote about that in the Demon Haunted World. And now you see it, you know, on Instagram and online every single day, these warnings, these prophecies of what happens in a society based on science and high technology in which most of us are excluded from it.

[Neil deGrasse Tyson]

Yeah, it's a sad state of affairs. I mean, we can lament what the world is like today, but then I, I wonder to myself how much worse it would have been had it not been for Carl. And you know, I hate thinking that way because every so much still looks so bad today. And I'm and Brent are very disappointed to learn that there's still this resistance to that cause. What we do know is that the Future of Life Award is going to both of you and on behalf of Carl. And I'm delighted by virtue of this program to participate in the publicity of what that award means, why it was created, what it's for, and why such an award should continue forever. Because there are always such people, in some cases behind the scenes, in some cases in front of who are really just trying to make a better world here. And let me ask you, Ann, we only have a couple of minutes left. Do you think this nuclear winter scenario hastened the end of the Cold War? Do you think it played a role?

[Ann Druyan]

Well, I'm not sure it's over. No. Okay. I mean, I think it may have hastened a kind of a little bit of a change. But of course there were so many other factors, too many variables, too many other very significant factors to say whether or not it did. I think it did. I think it led to a change of attitude in the Kremlin, I'll say that, because I did see that.

[Brian Toon]

But I think there's clear evidence, there's clear evidence that this mattered, as there was the Intermediate Range Nuclear forces treaty in 1986 between Ronald Reagan and Gorbachev, which basically tried to get rid of the missiles in Europe and it started a build down of nuclear weapons. It's continued to this day. Every American president, every Russian president since then has reduced arsenals, although there's still plenty of them to cause a nuclear winter. And at the time, just before this thing, Ronald Reagan gave a quote to the New York Times in which he explained about the year without a summer and how nuclear winter worked and said that scientists are warning us that this could happen. And he believed that and he was going to do something about it. And Gorbachev.

[Neil deGrasse Tyson]

Okay, so Carl did get through to Reagan that's what it sounds like. And.

[Brian Toon]

Gorbachev also, after the fact, gave a similar quote saying, and this is important, Russian and American scientists. So this goes back to Carl's review. You got the Russian scientists to do the same thing. Gorbachev said Russian and American scientists are telling us that no one can win a nuclear war and people of high morals must do something about this. And so he agreed with Reagan to do something. So I think there was an effect there and on world policy, it's lasted since that time. Of course, Trump walked away from this agreement a few years ago, but nevertheless, and I think Carl definitely was the person that communicated that information to Reagan and Gorbachev and other people in the political establishments that did something.

[Neil deGrasse Tyson]

Okay, so I guess my point then is if you read the history books, there's no mention of it. They talk about glasnost and they talk about all these other things. They talk about the collapse of the economy. And it seems like they're missing a very important cog in this wheel that that got turned that to bring all of that to an end, or at least to bring leaders to a new level of sensibility in decisions they might make.

[Brian Toon]

Yeah.

[Neil deGrasse Tyson]

Wow.

[Brian Toon]

The Soviet Union ended in 1992, you know, so it was about six years after we started building down these weapons. And so I think the build down of weapons is what triggered it. But as Ann just said, there are lots of other things happening. There was very costly to keep building these weapons. And there are other things. Which brings me to a point, I think that's important to know about the present day. The United States and Russia are both building new weapons of mass destruction. This is partly coming out of the Obama administration, which, in order to get an agreement on limiting weapons, agreed to give the Department of Defense hundreds of billions of dollars to build new weapons. So now we're entering an era where we have hypersonic gliders, we have drone submarines that are both built by the Russians who want to reduce the warning time. Pretty soon we're going to have computers deciding whether or not there's been a launch. And we should launch our missiles because a war has started.

[Neil deGrasse Tyson]

So we're dropping the level of nukes but increasing other lethal weapons of different kinds of.

[Brian Toon]

Well, we have plenty of tactics. We have plenty of nukes left. The United States and Russia, between them, have something like 8,000 nuclear weapons left. There's 500 cities in the United States and Russia. 500 cities, 8,000 weapons. That's enough weapons to attack every city with more.

[Neil deGrasse Tyson]

It's called overkill Overkill.

[Brian Toon]

There's still overkill. But the problem is that we're advancing to this state where human beings are not going to be able to control the weapons because the warning times are too short. My computer doesn't work that well. I don't know about yours. I sure won't want to trust those things to decide for me that we're going to kill everybody on the planet.

[Ann Druyan]

I don't know if you have enough time for this, but there's. What's so disturbing is that even when we were terrified of nuclear war back in the day, there were client state wars going on, but not a hot war in Europe, and not a hot war in Europe conducted by a society in which there is virtually one decision maker who is dealing with a rapidly declining economy, rapidly loss of status, a country that now has been effectively completely made a pariah state by virtue of its own actions of invading a friendly neighbor. And so I really worry about nuclear winter, I think virtually as much as I did back then, because the instability, I think, is greater now in some ways.

[Neil deGrasse Tyson]

Well, let me ask. We gotta land this plane. Brian, do you have a social media footprint that you might share with us? Are you on social media?

[Brian Toon]

I gave a TED Talk a few years ago.

[Neil deGrasse Tyson]

Oh, we'll look for that. Yeah. What's the title of that talk?

[Brian Toon]

I've been studying nuclear wars for 35 years and you should be worried. The interesting part of that is that about six months ago, there were 4 million views of this. The last time I looked there, there are 8 million views of this.

[Ann Druyan]

Wow.

[Neil deGrasse Tyson]

Okay, so. So, Anne, where can we find your.

[Ann Druyan]

My name on Instagram and various places.

[Neil deGrasse Tyson]

Andrew. Yeah. D R U Y.

[Ann Druyan]

And Carol Sagan. And.

[Neil deGrasse Tyson]

And Carl Sagan's got a footprint still.

[Chuck Nice]

Oh.

[Neil deGrasse Tyson]

In fact, still active.

[Ann Druyan]

I think that Carl is more revered, more beloved, and a greater influence in many ways than ever before. And what a tribute to a man who's been gone for 25 years that I think more people around the world are really beginning to get what he was teaching all along.

[Neil deGrasse Tyson]

And by the way, whatever was the early resistance from NASA to these ideas, let me remind the public or alert them for the first time that NASA has a fellowship in the name of Carl Sagan for students to study planetary science. So I don't know if that fully makes up for this, but it's certainly some admission or confession that Carl was onto something all along. Ann, I want you to take us out with a positive thought.

[Ann Druyan]

Okay, I have a positive thought.

[Neil deGrasse Tyson]

I know you're capable of this. But please.

[Ann Druyan]

I am.

[Brian Toon]

Please.

[Ann Druyan]

Because I am filled with hope. And my hope is based on the fact that all of us are communicating at the speed of light right now, with people all around our planet, there is a coalescing community of people who have access to more information than at any other time in the history of the world. Science, math, literature, history. It's all there for you. And I believe that if we're going to make our way out of this mess, it's going to be with that coalescing community of people who care about the future of life and the state of this gorgeous pale blue dot.

[Neil deGrasse Tyson]

And you never fail to remind me why I persistently think of you as one of the most enlightened people I've ever met.

[Ann Druyan]

Thank you.

[Neil deGrasse Tyson]

This has been Nuclear Winter edition. Thank you, Professor Brian Toon. Thank you, Annie. It's been a delight to have you back on StarTalk. Oh, and Chuck.

[Chuck Nice]

Yeah, that's okay. I'm filled with hope now, too. And.

[Neil deGrasse Tyson]

No, no, we're good with Chuck.

[Chuck Nice]

I'm also buying property in New Zealand.

[Neil deGrasse Tyson]

There you go. All right. This has been startalk, and I've been your host, Neil Degrasse Tyson. As always, I bid you to keep looking up.

[F]

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