Winter is Coming

Dinosaurs, Carl Sagan, and nuclear war. There was a moment in the not-so-distant past when we learned what drove the dinosaurs extinct — and that discovery, made during the Cold War, may have helped save humans from the same fate. In this episode, we'll take a journey from prehistoric times to the nuclear age and explore how humans contend with fears of the end. See pcm.adswizz.com https://pcm.adswizz.com for information about our collection and use of personal data for sponsorship and to manage your podcast sponsorship preferences. NPR Privacy Policy https://www.npr.org/about-npr/179878450/privacy-policy

Speaker names marked ? are inferred from speaking time and the show’s known hosts — they are not voice-verified.

• 0:00Speaker 00

  This message comes from the Southern Environmental Law Center. No one voted for dirty air and water. That's why S E L C is fighting back to defend the healthy environment everyone depends on. Because it's not political, it's fundamental. Learn more at S E L C dot org.

• 0:19Rund Abdelfatah?

  Planet Earth, 66 million years ago. The moment just before the end.

• 0:42Rund Abdelfatah?

  The wind tickles a patch of ferns. The shadow of a pine leaf dances lazily over a footprint in the dirt. Somewhere nearby, a lumbering beast stops mid-stride. It's a hulking mass of a creature, three horns, teeth like shears, and it swings its head down in a low arc, listening.

• 1:13Rund Abdelfatah?

  Then suddenly.

• 1:18Speaker 02

  A flash of light, thousands of times more blinding than the sun.

• 1:24Rund Abdelfatah?

  An asteroid.

• 1:25Speaker 02

  The size of Mount Everest.

• 1:27Rund Abdelfatah?

  Enters the Earth's atmosphere, moving incredibly fast.

• 1:32Speaker 03

  Ten times faster than the fastest bullet from a rifle.

• 1:37Speaker 04

  In the blink of an eye, this asteroid will crash into Earth's surface on the edge of the ocean with an impact equivalent to 5,000 times.

• 1:47Speaker 02

  The combined destructiveness of the entire nuclear arsenal at the height of the Cold War.

• 1:53Speaker 04

  It burrows into the Earth 20 miles deep.

• 2:00Speaker 04

  Everything within 90 miles.

• 2:02Speaker 02

  Every living thing.

• 2:04Speaker 04

  Is instantly vaporized.

• 2:11Rund Abdelfatah?

  But this is just the beginning of the end.

• 2:19Rund Abdelfatah?

  A giant fireball.

• 2:21Speaker 02

  All of the rock and dust and gas.

• 2:25Rund Abdelfatah?

  Climbs back up and up and up.

• 2:28Speaker 02

  All the way into space.

• 2:30Rund Abdelfatah?

  And bursts.

• 2:31Speaker 02

  Burst through the atmosphere.

• 2:33Rund Abdelfatah?

  As the earth below shakes violently.

• 2:36Speaker 02

  Magnitude 12 or 13, rippling the entire crust of the earth.

• 2:41Rund Abdelfatah?

  Triggering unimaginably high tsunamis.

• 2:44Speaker 02

  The real bummer was all of that material that got ejected into space began to fall back.

• 2:54Rund Abdelfatah?

  Millions of tiny specks, each the size of a grain of sand, re-enter the atmosphere and catch fire again.

• 3:03Speaker 03

  This is like an uncountable number of huge stars coming into the sky above you, heating the air and the rock.

• 3:11Speaker 04

  A sea of lava descending from the heavens, unleashing hell on earth.

• 3:17Speaker 03

  If you want to see it, open up your oven, turn the broiler on, and look at the glow bar. In this case, the whole sky is glowing. There are no shadows, so you're not going to get away from it.

• 3:27Speaker 04

  Swaths of life, the culmination of millions of years of evolution, wilt under the broiler of asteroid debris. Forests catch fire. The air teems with ash and smoke. And then...

• 3:44Rund Abdelfatah?

  Comes winter.

• 3:47Speaker 02

  The soot that stayed in the atmosphere blocked out the sun.

• 3:50Speaker 04

  Blocked out the sun.

• 3:52Speaker 03

  The amount of light that would get through would be 100 millionths of the amount of light we normally see.

• 3:59Speaker 02

  It effectively turned day into night.

• 4:02Speaker 03

  Temperatures fell below freezing over all the land.

• 4:05Speaker 04

  No light meant no food.

• 4:07Speaker 02

  Plants can't photosynthesize.

• 4:09Speaker 03

  The food chains in the ocean probably collapsed.

• 4:11Speaker 02

  To say that this was a challenging environment, you know, for life to survive and continue to evolve would be an understatement.

• 4:24Rund Abdelfatah?

  It was the end of a world.

• 4:30Rund Abdelfatah?

  And the beginning of another.

• 4:42Speaker 04

  Over the last few years here at Throughline, we've been finding ourselves thinking about the end a lot, what that might look like and feel like, partly because we live in a world with climate change and nuclear weapons. So we're kind of engineering the asteroid that might destroy us as we speak.

• 5:01Rund Abdelfatah?

  And also because a bunch of us have become new parents in that time, asking ourselves, what future will our kids inherit?

• 5:09Speaker 04

  What do dinosaurs have to do with any of that? Well, it turns out that for most of human history, no one had a clue that dinosaurs had walked to Earth before us or that they disappeared in a sudden flash.

• 5:22Rund Abdelfatah?

  But there was a moment in the not-so-distant past when we learned what caused their extinction. And that discovery may have helped save humans from the same fate. That moment is where we'll be taking you in this episode.

• 5:38Rund Abdelfatah?

  I'm Rundabir Fattah.

• 5:39Speaker 04

  And I'm Ramtin Arablouei. You're listening to Throughline from NPR.

• 5:44Rund Abdelfatah?

  Today, we're traveling deep inside the Earth's layers, up above the clouds as the first nuclear weapon is dropped, and all the way to the cosmos.

• 5:55Speaker 02

  Sometimes we can avoid the worst fate that we can imagine.

• 6:04Speaker 05

  Yes, hello. My name is Janice Beck. I live in Iwakuni, Japan. Throughline is one of the best, if not the best. I wait each week for a new episode, and I'm never disappointed. Keep on doing it, please. Thank you so much. Bye-bye.

• 6:22Speaker 06

  Stay tuned for the following announcements and messages from our sponsors. Hey, it's Latif from Radiolab. Our goal with each episode is to make you think, how did I live this long and not know that? Radiolab: Adventures on the Edge of What We Think We Know. Listen wherever you get podcasts.

• 6:43Speaker 07

  We will learn something on election night, but not everything. There's a lot we will not know, especially when it comes to close races. And we'll know much more the next morning and the morning after that. So save yourself a little time scrolling and listen to Up First. We'll be there when you wake up each and every morning this week with the latest midterm election news.

• 7:06Speaker 07

  The day's top headlines, local stories from your community, your next podcast binge listen.

• 7:11Rund Abdelfatah?

  You can have it all in one place, your pocket. Download the NPR app today.

• 7:21Rund Abdelfatah?

  Part one, 45,000 miles per hour.

• 7:29Rund Abdelfatah?

  It was 1977. A geologist named Walter Alvarez was spending a summer in Gubio, a town in Italy about halfway between Venice and Rome. It sits in a valley alongside a mountain formed by a fault line. And what was once an ancient seafloor became exposed over time. So you can actually see inside the earth and look at millions of years of the planet's history.

• 7:55Speaker 02

  So you can think of like a layer cake.

• 7:57Rund Abdelfatah?

  This is David Zepkowski. He's a historian of science at the University of Illinois Urbana-Champaign and author of the book Catastrophic Thinking. His dad, Jack Zepkowski, was a prominent paleontologist around this time.

• 8:11Speaker 02

  The layer cake going from the top, being the most recent layers of the history of life, all the way down to the earliest ones.

• 8:19Rund Abdelfatah?

  Try to picture it. A swirl of colors, rusty orange, dull brown, chalk white, with fossilized creatures sprinkled throughout. Each layer is a different thickness. And Walter Alvarez was focused on one layer in particular, the KT boundary.

• 8:38Speaker 02

  The KT boundary had been well studied around the world.

• 8:42Speaker 04

  It's striking, a very thin layer of clay, much thinner than the others around it, with a distinctive, dark, ashy color, kind of like coal. Below the KT boundary is the Cretaceous layer, marking the age of dinosaurs. It's filled with shards of dinosaur bones and teeth, the outline of their footprints. And above the KT boundary is the Tertiary layer, marking the age of mammals. In that one, you won't see many dinosaur fossils.

• 9:13Speaker 02

  In fact, none.

• 9:14Rund Abdelfatah?

  None.

• 9:15Speaker 02

  None.

• 9:16Speaker 04

  Given that, paleontologists had already figured out that the dinosaurs went extinct many millions of years ago, between the Cretaceous and Tertiary layers. They didn't know how it happened, or the amount of time it took, but they assumed-

• 9:30Speaker 02

  Natural selection was a really gradual process.

• 9:33Speaker 04

  The Darwinian view of the world, that over time, the strongest and brightest species went out. As a geologist, Walter wasn't really interested in dinosaurs. He was just trying to measure how long it had taken these layers of sediment to form. This would be a big breakthrough if he could figure it out. But nothing had worked so far, until-

• 9:59Speaker 03

  One day, his father calls up with an idea that has just occurred to him.

• 10:05Rund Abdelfatah?

  We'll get to that idea in a bit, but first, we need to take you on a little detour to learn more about Walter's father, Louis Alvarez. We promise it's gonna be worth it. See, Louis Alvarez wasn't just some guy with an idea. He was a Nobel Prize-winning physicist.

• 10:22Speaker 03

  The most Walter has ever said to me on the record was that he and his father were not close, you know, that's an exact quote.

• 10:30Rund Abdelfatah?

  By the way, this is Alec Navalo Lee.

• 10:32Speaker 03

  I am a novelist, critic, and biographer.

• 10:35Rund Abdelfatah?

  His upcoming biography is about Louis Alvarez. And he says Walter and Louis weren't close because from the time Walter was born in 1940-

• 10:45Speaker 03

  His father was occupied elsewhere.

• 10:57Rund Abdelfatah?

  It was the middle of World War II. American scientists were racing to build an atomic bomb before the Germans did. Louis, a young, up-and-coming physicist, gets involved and helps the American team figure out the missing link to actually make the bomb detonate. And when the order comes down to use the bomb on Hiroshima, he volunteers to be on the plane.

• 11:19Speaker 03

  On the observation plane.

• 11:21Rund Abdelfatah?

  Following closely behind the Inolika as it unleashed, for the first time in history, the power of a nuclear weapon onto a city of 350,000 people.

• 11:35Speaker 03

  When the bomb goes off, there's a flash of white light that comes from the cockpit. And so at that moment, he knows the bomb has gone off. The entire plane bounds upward when the shock wave from the bomb hits the plane. So they feel it. They feel that shock wave even from the air. And you can see the mushroom cloud. But when he looks down, he thinks that they've missed. It's so empty that he thinks that they missed entirely.

• 12:11Rund Abdelfatah?

  Peering out the plane window at the devastation wrought by a bomb they'd named Little Boy, the gravity of what just happened begins to dawn on Louis. And then his mind turns to his own little boy, Walter, who was four years old at this point. Louis pulls out a pen and paper and begins writing him a letter.

• 12:32Speaker 06

  Dear Walter,

• 12:37Speaker 06

  This is the first grown-up letter I have ever written to you. And it was really for you to read when you were older. During the last few hours, I've been thinking of you and your mother and our little sister, Jean. It was tough to take off on this flight, not knowing whether I would ever see any of you again.

• 12:56Speaker 03

  It's partially an account Of what happened that day. But he's also trying to like, get his thoughts together about what it means to use this bomb.

• 13:05Speaker 06

  A single plane disguised as a friendly transport can now wipe out a city.

• 13:11Speaker 03

  Because he's trying to, in some ways, justify it to himself.

• 13:15Speaker 06

  What regrets I have.

• 13:17Speaker 03

  This is kind of like the, the paragraph that I come back to a lot. What regrets I have about being a party to killing and maiming thousands of Japanese civilians this morning

• 13:27Speaker 06

  are tempered with the hope that this terrible weapon we have created may bring the countries of the world together.

• 13:33Speaker 03

  And prevent further wars.

• 13:35Speaker 06

  Alfred Nobel thought his invention of high explosives.

• 13:39Speaker 03

  Dynamite, you know, Nobel's invention.

• 13:41Speaker 06

  Would have that effect by making wars too terrible. But unfortunately, it had just the opposite reaction.

• 13:49Speaker 03

  He believes on some level that the atomic bomb is just so destructive that it's going to force the world to approach things differently.

• 13:58Speaker 06

  Our new destructive force is so many thousands of times worse that it may realize Nobel's dream.

• 14:05Rund Abdelfatah?

  The dream of ending all war.

• 14:10Speaker 03

  Walter did not read it until much later.

• 14:14Rund Abdelfatah?

  Over the next few decades, Louis threw himself into work. He did wild things like search for hidden chambers in the pyramids and investigate the assassination of JFK. Louis had this kind of superpower for finding things others had missed, all using physics, a tool that had brought humans closer than ever to playing God.

• 14:36Speaker 03

  So we aren't just passively observing nature, we are actively making things happen.

• 14:42Rund Abdelfatah?

  Meanwhile, his relationship with his son grew more distant, but eventually.

• 14:47Speaker 03

  Walter did read that letter.

• 14:50Speaker 06

  Dear Walter.

• 14:54Speaker 04

  Okay, detour over. Let's get back to Gubio. By this point, father and son are on better terms. Walter is feeling stuck in his research and Louis, hoping to help him out, gives Walter a call.

• 15:08Speaker 03

  An idea has just occurred to him.

• 15:11Speaker 04

  He's staring at this gift Walter had given him.

• 15:13Speaker 03

  A chunk of rock.

• 15:15Speaker 04

  From Gubio.

• 15:16Speaker 03

  Which shows the. KT boundary.

• 15:19Speaker 04

  Which he'd never seen before.

• 15:21Speaker 03

  He thinks it's one of the most exciting things he's ever seen.

• 15:24Speaker 04

  Why is it so thin? What's up with that color? And why did the dinosaur era fossils just disappear? For Louis, it was a revelation.

• 15:33Speaker 03

  It's almost an emotional reaction.

• 15:35Speaker 04

  Keep in mind, the KT boundary visible at Gubio wasn't a secret. Plenty of geologists and paleontologists had seen it. But Louis had an idea using some tools from his universe.

• 15:48Speaker 02

  Louis, in his physics work, had developed the ability to measure very trace amounts of rare elements in samples.

• 15:58Speaker 04

  Rare meaning there's not much of it on Earth. So if you find the same amount of it in a layer in different parts of the world.

• 16:04Speaker 02

  Then we can be pretty sure that they must have gotten formed at the same time.

• 16:07Speaker 04

  And you can figure out how long that layer took to form. So then the question was, which rare element to choose? They went with one called iridium, which besides tiny trace elements at the planet's core.

• 16:20Speaker 02

  Doesn't naturally occur on Earth.

• 16:22Speaker 04

  Where can you find it?

• 16:24Speaker 02

  It tends to be found more in meteorites and asteroids.

• 16:30Speaker 03

  What happens is that they find iridium.

• 16:32Speaker 04

  Like, too much of it.

• 16:33Speaker 03

  Thirty times as much as they are expecting.

• 16:36Speaker 04

  That's way more than they were expecting, way more than seemed possible even, which makes them think, shoot, we messed up.

• 16:43Speaker 02

  You know, figure that maybe there had been contamination in the sample or, you know, some other explanation.

• 16:49Speaker 04

  They run more tests with samples from different parts of the world. And after a couple of years.

• 16:54Speaker 02

  In 1980, concluded the only place it could have come from was a very large asteroid.

• 17:02Speaker 04

  A very large asteroid.

• 17:10Rund Abdelfatah?

  They had stumbled across the answer to a question they hadn't even been asking. What happened to the dinosaurs? Louis couldn't wait to tell the world their theory. And Walter knows better, right? He knows. That they're going to be very skeptical. Soon after, in June 1980, they published a paper with their findings.

• 17:30Speaker 02

  A very long paper in the journal Science.

• 17:32Rund Abdelfatah?

  And to sum up a very long paper, they theorized that an asteroid found its way into the Earth's atmosphere and then boom, goodbye dinosaurs. Some paleontologists were immediately skeptical. Reminds them of stuff like the flood narrative. It sounds religious. It sounds biblical. Yeah, to them, it sounds like crackpot science. But Louis had witnessed the atomic bomb level a city in an instant. So imagining an asteroid with more than a billion times that power leveling the world wasn't that wild to him. Sure, it might feel apocalyptic in the way that something like Noah's Ark does, but this was different.

• 18:15Speaker 02

  We can think of the extinction of the dinosaurs as an apocalypse because it is a revelation to us, not necessarily a scriptural one, but a no less profound revelation of how violent and unpredictable nature can actually be. Even people who have some religious sensibility, I think, would see this new story as undermining human significance.

• 18:48Speaker 04

  And even if you had doubts about what came to be known as the Alvarez hypothesis, it was hard to deny that it was a really good story.

• 18:58Speaker 02

  We can kind of vividly imagine this horrific final moment, those individual dinosaurs looking up at that bright flash in the sky.

• 19:11Speaker 02

  A new consciousness is developing which sees the Earth as a single organism

• 19:17Speaker 04

  and recognizes that an organism at war with itself is doomed.

• 19:23Speaker 04

  Coming up, some scientists begin to connect that bright flash in the sky that wiped out the dinosaurs to a bright flash that could wipe out all of humanity. We are one planet.

• 19:47Speaker 00

  I am Paul Ekla from Petaluma, California. You're listening to Throughline from NPR. Stay tuned for the following announcements and messages from our sponsors.

• 19:59Speaker 06

  Hey, it's Latif from Radiolab. Our goal with each episode is to make you think, how did I live this long and not know that? Radiolab, adventures on the edge of what we think we know. Listen wherever you get podcasts.

• 20:14Speaker 00

  This episode's sponsor is HubSpot, which offers the following message. What if instead of updating your CRM, your CRM updated you? HubSpot's self-updating CRM keeps your customer context current, so you can win more deals. Learn more at hubspot.com. This midterm election season, the NPR app is your single stop for clear, independent coverage. Stay on top of national and local storylines with news, stories, podcasts, and political analysis on demand. Download the NPR app and check out the Elections 2026 tab today. Part Two. It's the end of the world as we know it.

• 20:58Speaker 04

  What ever happened to the dinosaurs? That's one of the great mysteries of archaeology. By the early 1980s, Louis and Walter Alvarez's dinosaur hypothesis was starting to get attention in local papers, on TV, and radio. Alvarez says that an asteroid crashed into the Earth and wiped out the dinosaurs. But there were still some things Louis and Walter Alvarez didn't know, potential flaws in their hypothesis. For one, where was the crater that this massive asteroid supposedly left behind? And was the environment really inhospitable enough to kill off all the dinosaurs, even

• 21:43Speaker 04

  the ones way outside the impact zone, on different continents, in different hemispheres? They needed more information, more evidence, and more scientists across disciplines were getting involved.

• 21:57Speaker 03

  So we knew about the Alvarez discovery before it was published.

• 22:02Rund Abdelfatah?

  Enter Brian Toon.

• 22:06Speaker 03

  At the time, I lived in the San Francisco Bay area and worked at NASA Ames. We're working on the Earth's atmosphere and climates.

• 22:15Rund Abdelfatah?

  Brian had grown up in the shadow of the Cold War.

• 22:21Rund Abdelfatah?

  And by the time he was at NASA in the early 80s.

• 22:24Speaker 03

  There were 70,000 nuclear weapons on the planet.

• 22:28Rund Abdelfatah?

  Most of those weapons were part of the Soviet or US arsenals, and they were pointed at each other.

• 22:35Speaker 03

  70,000 nuclear weapons.

• 22:40Rund Abdelfatah?

  So when he came across the Alvarez hypothesis about a single asteroid strike wiping out the dinosaurs, his mind immediately went to that. Because this asteroid strike, which had the estimated energy of tens of millions of nuclear weapons, would have produced a massive fireball. A fireball which would likely have risen hundreds of kilometers above the surface of the Earth.

• 23:03Speaker 04

  Then Brian called up a friend of his.

• 23:05Speaker 03

  Richard Turco.

• 23:06Speaker 04

  Who worked for a company called R&D Associates, which did research for the Pentagon and Department of Energy and had already done modeling of nuclear explosions.

• 23:16Rund Abdelfatah?

  So anyway, Brian asked his friend if hypothetically, a nuclear weapon went off, is there a way to calculate how much dust it would kick up?

• 23:25Speaker 03

  He said, "Well, yeah, I know how much dust would be raised by a nuclear weapon."

• 23:30Speaker 04

  But what if all of them went off? How much dust would be raised then?

• 23:34Speaker 03

  Let me go think about that. So he went out.

• 23:37Speaker 04

  Ran the numbers.

• 23:38Speaker 03

  Tens of thousands of weapons go off.

• 23:41Speaker 04

  And concluded.

• 23:42Speaker 03

  They're going to put enough dust into the upper atmosphere to cause a big climate problem.

• 23:47Rund Abdelfatah?

  And then there were the fires. A nuclear blast emits enough light to ignite flammable materials in cities and forests, pumping even more smoke into the atmosphere.

• 23:59Speaker 03

  And so, we heard about their idea of smoke. And we thought, oh my gosh, we didn't think of the smoke. So, we put the fires into the model in urban areas.

• 24:08Speaker 04

  Computer models were a relatively new thing at this time. Simulations of reality that were helping scientists like Brian test out theories in a virtual world.

• 24:18Speaker 03

  And so, we discovered that, you know, there might be a prolonged period where there'd be so much smoke in the atmosphere that it would cause temperatures below freezing over the lands.

• 24:31Speaker 04

  A long winter.

• 24:37Speaker 04

  In October 1981, Brian took the model he and some colleagues had made to a conference organized exclusively to discuss and test Louis and Walter Alvarez's hypothesis.

• 24:49Rund Abdelfatah?

  But for Brian, this wasn't just about dinosaurs or the past anymore. It could be the key to humanity's future, to avoiding our own potential end. This was a big idea, and they wanted one of the most well-known scientific thinkers of the time on the case.

• 25:07Speaker 03

  Should we call up Carl?

• 25:08Rund Abdelfatah?

  Carl Sagan.

• 25:11Speaker 06

  The cosmos is also within us. We're made of star stuff.

• 25:15Rund Abdelfatah?

  Yes, that Carl Sagan.

• 25:18Speaker 06

  The journey for each of us begins here. We're going to explore the cosmos in a ship of the imagination.

• 25:25Speaker 02

  Carl Sagan was in people's living rooms, talking about the wonders of the universe.

• 25:29Speaker 06

  Drawn by the music of cosmic harmonies, it can take us anywhere in space and time.

• 25:35Rund Abdelfatah?

  Carl was an astronomer turned bona fide celebrity, the so-called showman of science by Time Magazine. His television show, Cosmos: A Personal Voyage, was the highest-rated PBS program at the time, reaching over 500 million viewers worldwide.

• 25:52Speaker 02

  He had an almost like kind of Mr. Rogers-like demeanor, you know, to him. Calm, almost gentle.

• 26:00Speaker 06

  Contemplating the stars, organized collections of 10 billion...

• 26:04Speaker 02

  Billion, billion atoms. Billions and billions, that was sort of his catchphrase.

• 26:09Speaker 00

  It was completely authentic.

• 26:12Rund Abdelfatah?

  This is Anne Druian. She co-wrote and co-created Cosmos with Carl. And from the moment they'd met.

• 26:18Speaker 00

  I heard this laugh that was so thrilling. And it was the laugh of a person who had no fear.

• 26:30Rund Abdelfatah?

  Her life would never be the same.

• 26:32Speaker 00

  There was no facade. There was no baloney. There was no presentation of self to impress.

• 26:42Rund Abdelfatah?

  Carl Sagan was magnetic, and he was busy. He was on TV. He and Anne, his future wife, were falling in love. Oh, and he was also Brian Toon's PhD advisor.

• 26:55Speaker 03

  You gave him an idea. He would respond to that idea, and you'd often come back with some related idea that you would have never thought of. A lot of them were not right, but he just threw ideas out right and left.

• 27:08Speaker 02

  He had this gift for not just simplifying complex science, but making science feel personal and important to an everyday person, right? Why should we care about what happened 14 billion years ago, or even hundreds of millions of years ago? It was thinking about why science gives us insight into the big questions that matter about existence.

• 27:39Speaker 04

  And at that time, there was no bigger question than whether nuclear war between the US and the Soviet Union could end our existence altogether. So when Carl got Brian's call, he eagerly agreed to start working alongside Brian and the other scientists to answer that very question.

• 27:57Speaker 00

  I'm pretty sure it was named nuclear.

• 27:58Speaker 04

  My winter in my living room. Nuclear winter.

• 28:04Speaker 04

  Those two words summed up everything the model showed. But not everyone was so excited about their research.

• 28:12Speaker 03

  The head of NASA Ames was so mad it looked like steam was coming out of his ears. His face was bright red. Said, I'm going to fire you and everybody in your building if you keep working on this.

• 28:23Rund Abdelfatah?

  Why was it seen as being so threatening?

• 28:26Speaker 03

  He was afraid Ronald Reagan would shut down NASA Ames to stop it.

• 28:31Speaker 04

  President Ronald Reagan wasn't a fan of any science that called for more government regulation. And he believed that the more nuclear weapons the US had, the less likely the Soviets would be to attack. But Carl talked to the head of NASA Ames and convinced him to let this research continue. For the scientists working on this, this wasn't about politics. It was about following where the science took them. And some of them, like Brian Toon, thought.

• 28:59Speaker 03

  We thought if science people came up and said nuclear weapons are going to kill most of the people on the planet, that the major political figures and politicians, the Department of Defense would say, oh, my gosh, this is an important thing. We should do something about it. We're just as naive as Louis Alvarez, who thought nuclear weapons would end wars.

• 29:20Speaker 04

  But Carl knew better. He didn't think a single scientific paper was going to be enough to get people's attention.

• 29:27Speaker 03

  Carl's pretty much a loose cannon.

• 29:33Speaker 03

  Here now, reporting from Washington, Ted Koppel.

• 29:36Rund Abdelfatah?

  November 20th, 1983. Ted Koppel, the host of Nightline.

• 29:41Speaker 02

  The most watched news program at the time.

• 29:44Rund Abdelfatah?

  Was hosting a roundtable all about nuclear weapons.

• 29:47Speaker 06

  We are joined here in Washington by a live audience.

• 29:51Speaker 02

  And a distinguished panel of guests.

• 29:53Rund Abdelfatah?

  Carl Sagan was one of the guests, along with some of the country's most powerful people.

• 29:59Speaker 02

  Former Secretary of State Henry Kissinger. William F. Buckley Jr. Former Secretary of Defense Robert McNamara. Along with all cost survivor L. E. V. Sell.

• 30:09Rund Abdelfatah?

  And former National Security Advisor Brent Snowcroft.

• 30:13Speaker 02

  So it's like these people are talking and, you know, many, many millions of people stayed up and stayed tuned for this.

• 30:22Rund Abdelfatah?

  Most Americans tuning into this roundtable would have just seen a made-for-TV movie called The Day After, which debuted that night to an audience of 100 million viewers in the US. Roger, copy. This is not an exercise. Roger, understand. Major Reiner, we have a massive attack. This is a US missile

• 30:39Speaker 02

  this time. Over 300 missiles inbound now.

• 30:45Speaker 02

  And it's billed as an authentic depiction of the aftermath of a of a nuclear war.

• 30:54Speaker 02

  And this is one of the first times that anybody's tried to actually realistically reproduce what what a what a nuclear war would look like.

• 31:08Speaker 02

  Hello? Is anybody there? Anybody at all?

• 31:16Speaker 02

  And a text appears on screen at the very end saying, "The catastrophic events you've just witnessed are, in all likelihood, less severe than the destruction that would actually occur in the event of a full nuclear strike against the United States."

• 31:32Rund Abdelfatah?

  And then, as soon as The Day After credits end, Carl and the other Roundtable guests appear, ready to discuss the film everyone just saw. Henry Kissinger, not a fan. I think that this film presents a very simple-minded notion of the nuclear problem. Neither was William F. Buckley Jr. The guy who wrote it says, "I would like to see people start..." ...to question the value of defending this country with a nuclear arsenal. But Sagan.

• 32:03Speaker 04

  Sagan turns to the camera and says.

• 32:05Speaker 07

  It's my unhappy duty to point out that the reality is much worse than what has been portrayed in this movie, and this new emerging reality has significant policy implications. The nuclear winter.

• 32:22Speaker 04

  The nuclear winter that will follow even a small nuclear war involves a pall of dust and smoke, which would reduce the temperatures, not just in the northern mid-latitudes, but pretty much globally, to sub-freezing temperatures for months.

• 32:35Speaker 07

  There is a real possibility of the extinction of the human species from such a war.

• 32:41Rund Abdelfatah?

  It was a mic drop moment.

• 32:43Speaker 07

  Imagine a room awash in gasoline, and there are two implacable enemies in that room. One of them has 9,000 matches. The other has 7,000 matches. Each of them is concerned about who's ahead, who's stronger. Well, that's the kind of situation we are actually in.

• 33:10Speaker 04

  Soon after that roundtable, Carl, Brian Toon, and the other scientists published their scientific paper on nuclear winter. But the message was already out there, and Carl and Anne made sure people outside of the scientific community kept talking about it.

• 33:28Speaker 04

  That same year, they wrote an article together explaining the theory in one of the most popular publications of the time, Parade Magazine.

• 33:36Speaker 00

  Because it was inserted in the Sunday papers across the nation.

• 33:42Speaker 04

  Which most people would have gotten delivered to their front doorstep. And that morning, when they opened up the paper, they would have seen a photo of Planet Earth alight with nuclear flashes, and the words, "Would nuclear war be the end of the world?", a special report by Carl Sagan.

• 34:00Speaker 00

  He was proud of the fact that the public would be getting this information at the same time as the scientific elite.

• 34:09Speaker 04

  By the end of 1983, tens of millions of Americans had heard of nuclear winter. And as far as the average American was concerned, the messenger and man behind it all was Carl Sagan.

• 34:23Speaker 00

  People are used to having a shaman.

• 34:25Speaker 05

  Goes back 100,000 generations, you know, since we've been telling stories to each other at night in round the campfire.

• 34:35Rund Abdelfatah?

  Coming up, Carl Sagan sets out to tell the story of nuclear winter to anyone who'll listen and finds himself in a battle for the future of the human race.

• 35:00Speaker 05

  My name's Amanda. I'm calling from Portland, Maine, and you're listening to True One.

• 35:06Speaker 00

  Stay tuned for the following announcements and messages from our sponsors.

• 35:10Speaker 06

  Hey, it's Latif from Radiolab. Our goal with each episode is to make you think, how did I live this long and not know that? Radiolab, adventures on the edge of what we think we know. Listen wherever you get podcasts.

• 35:25Speaker 00

  This episode's sponsor is HubSpot, which offers the following message. What if instead of updating your CRM, your CRM updated you? HubSpot's self-updating CRM keeps your customer context current, so you can win more deals. Learn more at hubspot.com. This week on Short Wave, truth and fraud. That is the beating heart of the movie You Can See Everything. But can you spot a liar in action? Lying doesn't come with emotional and behavioral stereotypes that we think. How to detect deception for real on Short Wave, the science podcast from NPR. Part three, the pale blue dot.

• 36:14Speaker 05

  I remember it vividly. Carl would have a look on his face like he had something really great to tell me.

• 36:24Speaker 05

  And he said, I've been told that Gorbachev wants to know more about nuclear winter.

• 36:30Rund Abdelfatah?

  Mikhail Gorbachev, the leader of the Soviet Union, America's enemy in the Cold War. And not long after, Carl, Anne, and their young daughter found themselves on a plane to Moscow.

• 36:44Speaker 05

  There was a reception the day before, and Gorbachev was there. And so was our daughter, who was wearing the most adorable outfit, which made people confuse her with the Azerbaijani junior skating champion.

• 37:02Rund Abdelfatah?

  The following day, Carl made his way to the Kremlin to meet with the Soviet Central Committee and Gorbachev. A few hours went by, and then...

• 37:12Speaker 05

  He came back from this meeting.

• 37:15Rund Abdelfatah?

  Anne could instantly tell it went well.

• 37:17Speaker 05

  He was completely energized.

• 37:20Rund Abdelfatah?

  He started off talking about how the room looked, who was there, but mostly...

• 37:25Speaker 05

  Mostly, he was really talking about just how interested they were and how sober, how sober they were at this information.

• 37:35Speaker 05

  You know, the possibility that there could be a nuclear winter was a waking nightmare.

• 37:46Speaker 04

  It was 1986 when Carl got that invitation to meet with Gorbachev. He'd spent the year since the Parade article on a campaign to warn the world of the existential threat of nuclear war.

• 37:59Speaker 05

  Going everywhere.

• 38:00Speaker 04

  Spreading the gospel of nuclear winter.

• 38:02Speaker 05

  We didn't have anybody to do PR. We didn't have anybody financing this. It was personal.

• 38:10Speaker 04

  He hosted a TV special.

• 38:12Speaker 00

  For months, there would be a dark, cold, and deadly nuclear winter, no matter in what season the war might occur.

• 38:22Speaker 04

  Gave lectures around the country.

• 38:24Speaker 00

  Anything that involves the future is fundamentally threatened by the danger of nuclear war.

• 38:30Speaker 04

  Testified before Congress. One response by a senior practitioner was the following. He said, "Look, if you think that the mere..." The prospect of the end of the world is enough to change thinking in Washington and Moscow. You clearly have not spent much time in those places. He even met with the Pope at the Vatican.

• 38:49Speaker 00

  We were in the Pope's personal apartments briefing him on nuclear winter.

• 38:56Speaker 04

  Meanwhile, a symphony of media coverage continued to surround the idea.

• 39:01Speaker 06

  I just felt eager to be on the cutting edge of understanding. What's the world like? Why is it changing?

• 39:09Speaker 04

  This is Andrew Revkin. He's a longtime science journalist who got his start back in the 80s covering nuclear winter.

• 39:17Speaker 06

  There were so many things happening in that period between the United States and the Soviet Union. There was this arms race. There was the economics.

• 39:26Speaker 00

  These competing views of what the world economy should be.

• 39:31Speaker 06

  There was a technology race. Computers were advancing rapidly.

• 39:35Speaker 00

  And then each country had these client states that were actually killing each other.

• 39:40Speaker 04

  But for Carl, this competitive approach missed the bigger picture. This was about all of our futures. So people on the other side of the Iron Curtain needed to hear about nuclear winter too. For that, he needed the help of scientists inside the Soviet Union.

• 39:58Speaker 06

  To try to beat the drama of disarmament and that nuclear winter demonstrated that nuclear war was unwinnable.

• 40:04Speaker 00

  And they did because they really, you know, anyone who knows anything about science realizes that it's a global enterprise.

• 40:16Speaker 04

  Eventually, nuclear winter theory began to gain traction in the Soviet Union.

• 40:22Speaker 06

  The way it felt to me at the time when I was reporting this, it seemed pretty clear that the Soviets saw an advantage in playing up the specter of nuclear winter as a counterweight to Ronald Reagan's Star Wars.

• 40:43Speaker 03

  Further the cause of peace. But a freeze now would make us less, not more, secure and would raise, not reduce, the risks of war.

• 40:52Rund Abdelfatah?

  Around the same time, nuclear winter theory was bubbling up. President Ronald Reagan had announced a new idea of his own.

• 41:00Speaker 06

  The Strategic Defense Initiative, better known as Star Wars.

• 41:03Speaker 03

  Let me share with you a vision of the future which offers hope.

• 41:07Rund Abdelfatah?

  Reagan proposed a high-tech space shield that would shoot down enemy nukes before they could strike the US. In other words, Reagan was saying, we could actually win a nuclear war, with the asterisk that the technology hadn't been developed yet. Still, that introduced a scary possibility. If destruction was no longer mutually assured, what would stop an invulnerable country from launching a nuclear attack?

• 41:37Speaker 06

  And a lot of peace activists, including many scientists, were alarmed by that.

• 41:43Speaker 07

  If we were so foolish as to go ahead with it, we would be far less safe than we are today.

• 41:50Rund Abdelfatah?

  Carl Sagan was a vocal opponent of Star Wars.

• 41:53Speaker 07

  It is ruinously expensive. It abrogates a large number of treaties that the United States has solemnly signed. And in addition, it is likely to bring about nuclear war itself if the Soviets were to believe, as they say, that it is part of an American plan for first strike. Soviet leader Mikhail Gorbachev condemned the US Star Wars missile defense program, warning that it will increase the risk of accidental war.

• 42:28Rund Abdelfatah?

  Carl Sagan found himself in the middle of a delicate political chess match, which is how he ended up at the Kremlin, explaining nuclear winter theory to Gorbachev.

• 42:38Speaker 04

  By the way, he and Ann were also invited to the White House three times to dine with Reagan.

• 42:44Speaker 00

  And we said no each time, very politely, but no, thank you. Because this was when his administration was committing unspeakable atrocities in Central America. Ronald Reagan was the person who ripped Jimmy Carter's solar panels off the roof of the White House. His contempt for science. And in reality...

• 43:08Speaker 05

  You know, it was just the headline always about him. We just didn't want to be complicit.

• 43:16Speaker 04

  And also acknowledges that while Carl and other scientists working on nuclear winter theory never let politics impact the science itself, when it came to telling the story, they did have a political agenda.

• 43:28Speaker 05

  The entire human species was living in a hostage drama. And so, yes, we had definite political feelings, we're parents. We have children. Is that political or is that biological? I don't know. I think it's biological. It's survival.

• 43:49Speaker 04

  And although they never met with him, it's clear Reagan was aware of nuclear winter. During one press conference in 1985, he mentioned a volcanic eruption from the 1800s, which had cooled the earth and produced famines. Then Reagan asked, quote, "If one volcano can do that, what are we talking about with the whole nuclear exchange? The nuclear winter that scientists have been talking about."

• 44:18Speaker 00

  Since the original nuclear winter idea was proposed, several groups have tried to study the problem, and each has come up with a different computer model for the global effects of nuclear war.

• 44:29Speaker 06

  I learned something about science through that period.

• 44:33Speaker 06

  New science often leads to more questions, and that was absolutely the case for nuclear winter.

• 44:40Speaker 02

  I think that some people were worried in the scientific community about overstating the case.

• 44:46Rund Abdelfatah?

  David Zepkowski again.

• 44:48Speaker 06

  Nuclear winter essentially is, exists in data and models, and models are highly imperfect simulations of how the world works.

• 44:58Speaker 02

  And this is, I think, part of the reason why some folks did resent Carl Sagan. I think they thought he was a showboat a little bit, you know? He jumped the gun.

• 45:06Speaker 06

  Scientists are human beings, and they realize they have the capacity to influence world events. The scientists who were involved with Sagan, they all kind of were riding, riding this wave. And journalists like me were riding the wave, too.

• 45:21Rund Abdelfatah?

  By the mid 1980s, a few scientists had begun rebranding the theory.

• 45:25Speaker 00

  Nuclear fall, a chill rather than the dramatic bitter cold hypothesized for a nuclear winter.

• 45:32Rund Abdelfatah?

  They argued it wouldn't lead to full extinction of the human race, but it would still be really bad.

• 45:39Speaker 07

  Anybody who needs to know the weather report after a nuclear war in order to be deterred is already crazy.

• 45:45Rund Abdelfatah?

  But one scientist, Fred Singer, disagreed and said it could actually bring on a nuclear summer. What they've forgotten is that the smoke cloud also keeps in the heat. Singer was a prominent climate change skeptic, and it was later discovered that throughout his career, he had been paid by oil and tobacco companies who had hired a handful of scientists to quell concerns about the impact these companies were having on the environment. Some historians call them merchants of doubt.

• 46:16Speaker 06

  Professional purveyors of uncertainty.

• 46:18Speaker 02

  People who have set out deliberately to confuse the public about science.

• 46:24Speaker 06

  Who would just frame the questions around overstatement and uncertainties being the real story on any issue.

• 46:35Speaker 04

  And these voices got a lot of airtime.

• 46:38Speaker 06

  We in the media were addicted to conflict and debate, and so it's easy to build stories that kind of mischaracterize the uncertainty by making it a us and them fight.

• 46:53Speaker 04

  At the same time, David Sopkowski says there was some truth to the claim that Carl Sagan and other scientists sounding the alarm about nuclear winter were making things sound as catastrophic as possible.

• 47:06Speaker 02

  Absolutely, they were fear mongering. They're presenting us with some of the more pessimistic models because they want us to wake up.

• 47:14Speaker 00

  I call it prophecy, not fear mongering. If something will happen that will destroy absolutely everything you care about, even if that's a small possibility, especially human-made possibility, we've engineered for ourselves, what you have to do is sound the alarm.

• 47:37Speaker 00

  As many people as possible should have.

• 47:40Speaker 06

  Have the ability to do something to avert it.

• 47:47Speaker 06

  This goes back to Plato and Aristotle in what's called the noble lie, where you're consciously not speaking the entire truth in service of the better outcome for society. Because you know it would be inconveniently complicated or contentious to lay out the entire issue. To prove a theory really means to get everyone to accept it. And that's a matter of personal taste.

• 48:21Rund Abdelfatah?

  And the more evidence you see, the more likely you are to believe it. Louis Alvarez, who had helped kickstart all of this with that dinosaur extinction theory, had some doubts about nuclear winter, though he made sure never to share them publicly. It was a means to achieving that long awaited peace he'd hoped nuclear weapons would bring. He wrote in his memoir, "The most encouraging feature of the nuclear winter scenario is that no one has been able to disprove it. It has had a very salutary effect on the thinking of military planners on both sides of the world."

• 49:00Rund Abdelfatah?

  In Moscow, the hammer and sickle is lowered for the last time, and an era comes to an end.

• 49:12Speaker 03

  Gorbachev said it best today, just moments before he resigned his post as the last president of the Soviet Union. "If you have to go, you have to go. It's that time," he said. Both Gorbachev and Reagan wrote that the reason that they controlled nuclear weapons was because of this discovery of nuclear winter.

• 49:37Speaker 04

  And while there were economic and political realities that pushed the Soviet Union towards collapse...

• 49:43Speaker 02

  I do think that it had a role in the, you know, quote unquote, "fall of communism."

• 49:51Speaker 04

  Louis Alvarez died in 1988. He didn't see the end of the Cold War in 1991 or the discovery of the asteroid crater a year before that, which put to rest most doubts about the dinosaur extinction theory.

• 50:08Rund Abdelfatah?

  Soon after the Cold War ended, Anne remembers sitting in the audience of a talk given by the Soviet cosmonaut, Alexei Leonov.

• 50:16Speaker 00

  Who was the very first human ever to walk in space.

• 50:21Rund Abdelfatah?

  He had also been in the room at the Kremlin several years earlier when Carl Sagan explained "nuclear winter" to Gorbachev.

• 50:28Speaker 00

  Alexei Leonov, he began his talk by saying words to the effect of, "There's someone in our audience who we owe more to than any other, and that's Carl Sagan. Because when Carl Sagan came to debrief us on the nuclear winter, after it was over and Dr. Sagan left the room, Gorbachev said to us, "Well, it's over, isn't it?"

• 51:06Rund Abdelfatah?

  Carl Sagan died in 1996 with some questions still hanging over exactly how nuclear winter theory would play out in reality. While some more recent models suggest it could be better than he predicted, others show it might actually be even worse.

• 51:33Speaker 00

  The Earth is a very small stage in a vast cosmic arena. When someone tells you, "That's Earth." On it... As Carl brilliantly said, "Everyone you ever loved." Everyone you know. Everyone you ever heard of. Every human being who ever was lived out their lives. That's it. That's the reality of our true circumstances in the universe. Think of the rivers of blood spilled by all...

• 52:04Speaker 07

  Those generals and emperors, so that in glory and triumph, they could become the momentary masters of a fraction of a dot. You see how nonsensical it is to divide that planet up and to be willing to destroy it. To me, it underscores our responsibility to deal more kindly with one another and to preserve and cherish the pale blue dot, the only home we've ever known.

• 52:49Rund Abdelfatah?

  That's it for this week's show. I'm Rund Abdelfatah.

• 52:53Speaker 04

  And I'm Ramtin Arablouei, and you've been listening to Throughline from NPR.

• 52:57Rund Abdelfatah?

  This episode was produced by me.

• 52:59Speaker 04

  And me, and. Lawrence Wu.

• 53:02Speaker 00

  Julie Kane. Anya Steinberg. Casey Minor. Christina Kim. Devon Katayama. Sarah Wyman. Irene Noguchi.

• 53:11Rund Abdelfatah?

  Voiceover work in this episode was done by Casey Herman. And thank you to NPR's Indicator Podcast co-host and reporter Wayland Wong for letting her husband Alec Navalali use her home studio to record with us for this episode.

• 53:25Speaker 04

  Thank you to Jonette Oakes, Keondre Starling, Johannes Dergi, Tony Cavan, Nadia Lancy, Edith Chapin, and Colin Campbell.

• 53:35Rund Abdelfatah?

  Fact checking for this episode was done by Kevin Vogel. This episode was mixed by Robert Rodriguez. Music for this episode was composed by Ramtin and his band, Drop Electric, which includes.

• 53:46Speaker 07

  Naveed Marvi. Cho Fujiwara.

• 53:49Rund Abdelfatah?

  Anya Mizani.

• 53:51Speaker 04

  And finally, if you have an idea or like something you heard on the show, write us at [email protected]. And if you don't already, please follow us on Apple, Spotify, and the NPR app. That way, you'll never miss an episode.

• 54:07Rund Abdelfatah?

  Thanks for listening.

• 54:16Rund Abdelfatah?

  Stay tuned for the following announcements and messages from our sponsors.