Winter is Coming

Summary

Throughline Podcast Episode Summary: "Winter is Coming"

Release Date: March 13, 2025
Hosts: Rund Abdelfattah and Ramtin Arablouei
Description: Throughline explores historical moments that have shaped our world. In "Winter is Coming," the episode delves into the asteroid impact that led to the dinosaurs' extinction and the subsequent development of the nuclear winter theory during the Cold War, highlighting the interplay between scientific discovery and global politics.

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1. The Catastrophic End of the Dinosaurs

Timestamp: 00:29 – 05:55

The episode opens with a vivid portrayal of the asteroid impact 66 million years ago, setting the stage for the extinction event that wiped out the dinosaurs. Rund Abdelfattah narrates the scene, capturing the sudden and devastating effects of the asteroid's collision with Earth.

Key Points:

• Alvarez Hypothesis: Geologist Walter Alvarez, alongside his father Louis Alvarez, proposed that a massive asteroid impact was responsible for the dinosaurs' sudden extinction. This theory was a significant shift from the previously held belief of gradual extinction through natural selection.

• KT Boundary Discovery: While studying the sediment layers in Gubbio, Italy, the Alvarez team identified a thin clay layer enriched with iridium, a rare element not commonly found on Earth's surface but abundant in asteroids. This discovery provided critical evidence supporting the asteroid impact theory.

Notable Quote:

"No one had a clue that dinosaurs had walked to Earth before us or that they disappeared in a sudden flash."
— Rund Abdelfattah [05:20]

2. Birth of the Nuclear Winter Theory

Timestamp: 21:42 – 35:47

Transitioning from ancient extinction events to contemporary global threats, the episode explores how the study of the asteroid impact influenced the understanding of nuclear warfare's potential consequences.

Key Points:

• Cold War Context: During the early 1980s, the world was gripped by the fear of nuclear annihilation, with the United States and the Soviet Union amassing vast arsenals of nuclear weapons.

• Brian Toon's Role: Brian Toon, a NASA scientist, connected the Alvarez hypothesis to nuclear warfare. By modeling the aftermath of multiple nuclear explosions, Toon and his colleagues, including physicist Richard Turco, concluded that a "nuclear winter" could result, drastically altering Earth's climate.

• Carl Sagan's Advocacy: Renowned astronomer Carl Sagan became a pivotal figure in publicizing the nuclear winter theory. His involvement lent credibility and urgency to the scientific findings, advocating for nuclear disarmament to prevent such catastrophic outcomes.

Notable Quote:

"A sea of lava descending from the heavens, unleashing hell on Earth."
— Ramtin Arablouei [03:21]

3. Influence and Impact on Global Policy

Timestamp: 35:47 – 53:38

The narrative shifts to the broader implications of the nuclear winter theory on international relations and policy-making.

Key Points:

• Media and Public Awareness: Carl Sagan and his team leveraged media platforms, including a significant appearance on Ted Koppel's Nightline, to disseminate the dangers of nuclear winter to the public and policymakers.

• Political Resistance: Despite growing scientific consensus, there was considerable pushback from political figures like President Ronald Reagan, who initiated the Strategic Defense Initiative ("Star Wars") to bolster nuclear capabilities, inadvertently increasing the risk of nuclear conflict.

• Soviet Union Engagement: The theory found resonance in the Soviet Union, influencing leaders like Mikhail Gorbachev to reconsider nuclear strategies, contributing to the eventual détente and the end of the Cold War.

• Legacy of the Alvarezes: Louis Alvarez's contributions laid the groundwork for cross-disciplinary collaborations that bridged geology, physics, and climatology, emphasizing the interconnectedness of Earth's history and human actions.

Notable Quote:

"Our responsibility to deal more kindly with one another and to preserve and cherish the pale blue dot."
— Carl Sagan [53:04]

4. Reflections and Ongoing Relevance

Timestamp: 53:38 – End

Concluding the episode, the hosts reflect on the enduring legacy of the nuclear winter theory and its lessons for contemporary global challenges.

Key Points:

• Scientific Responsibility: The episode underscores the importance of scientists engaging with the public and policymakers to address existential threats, drawing parallels between past and present challenges like climate change.

• Human Survival: Emphasizing Carl Sagan's perspective, the narrative highlights the fragility of human existence and the need for collective action to ensure the planet's sustainability.

Notable Quote:

"The Earth is a very small stage in a vast cosmic arena."
— Carl Sagan [52:22]

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Conclusion

"Winter is Coming" masterfully intertwines the story of the dinosaurs' extinction with the contemporary fears of nuclear war, illustrating how scientific discoveries can profoundly influence global policies and societal perspectives. Through interviews, historical accounts, and insightful analysis, the episode serves as a poignant reminder of humanity's responsibility to safeguard its future by learning from the past.

Transcript

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[Rund Abdelfattah]

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

[David Sapkowski]

A flash of light thousands of times more blinding than the sun. An asteroid the size of Mount Everest.

[Rund Abdelfattah]

Enters the Earth's atmosphere, moving incredibly fast.

[Brian Toon]

10 times faster than the fastest bullet from a rifle.

[Ramtin Arablouei]

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 the combined.

[David Sapkowski]

Destructiveness of the entire nuclear arsenal at the height of the Cold War.

[Ramtin Arablouei]

It burrows into the earth 20 miles deep. Everything within 90 miles, every living thing, is instantly vaporized.

[Rund Abdelfattah]

But this is just the beginning of the end. A giant fireball.

[David Sapkowski]

All of the rock and dust and.

[Rund Abdelfattah]

Gas climbs back up and up and.

[David Sapkowski]

Up, all the way into space.

[Rund Abdelfattah]

And bursts.

[David Sapkowski]

Bursts through the atmosphere as the Earth below shakes fire violently, magnitude 12 or 13, rippling the entire crust of the.

[Rund Abdelfattah]

Earth, triggering unimaginably high tsunamis.

[David Sapkowski]

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

[Rund Abdelfattah]

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

[Brian Toon]

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

[Ramtin Arablouei]

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

[Brian Toon]

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.

[Ramtin Arablouei]

Swathes 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.

[Rund Abdelfattah]

And then comes winter.

[David Sapkowski]

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

[Ramtin Arablouei]

Blocked out the sun.

[Brian Toon]

The amount of light that would get through would be a hundred millionth of the amount of light we normally see.

[David Sapkowski]

It effectively turned day into night.

[Brian Toon]

Temperatures fell below freezing over all the land.

[Ramtin Arablouei]

No light meant no food.

[David Sapkowski]

Plants can't photosynthesize.

[Brian Toon]

The food chains in the ocean probably collapsed.

[David Sapkowski]

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

[Rund Abdelfattah]

It was the end of a world and the beginning of another.

[Ramtin Arablouei]

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.

[Rund Abdelfattah]

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

[Ramtin Arablouei]

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.

[Rund Abdelfattah]

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. I'm Rund Abdelfattah.

[Ramtin Arablouei]

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

[Rund Abdelfattah]

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.

[David Sapkowski]

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

[Carl Sagan]

Yes, hello, my name is Janice Beck.

[Ann Druyan]

I live in Iwakuni, Japan.

[Rund Abdelfattah]

Truline is one of the best, if not the best.

[Alec Navala Lee]

I wait each week for a new.

[Ann Druyan]

Episode, and I'm never disappointed. Keep on doing it, please.

[Rund Abdelfattah]

Thank you so much.

[Ann Druyan]

Bye Bye.

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[Rund Abdelfattah]

Part 1 45,000 miles per hour it was 1977. A geologist named Walter Alvarez was spending a summer in Gubbio, 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 sea floor became exposed over time. So you can actually see inside the Earth and look at millions of years of the planet's history.

[David Sapkowski]

So you can think of like a layer cake.

[Rund Abdelfattah]

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

[David Sapkowski]

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.

[Rund Abdelfattah]

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.

[David Sapkowski]

The KT boundary had been well studied around the world.

[Ramtin Arablouei]

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, the you won't see many dinosaur fossils.

[David Sapkowski]

In fact, none.

[Rund Abdelfattah]

None.

[David Sapkowski]

None.

[Ramtin Arablouei]

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.

[David Sapkowski]

They assumed natural selection was a really gradual process.

[Ramtin Arablouei]

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.

[Advertiser 2]

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

[Rund Abdelfattah]

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 going to be worth it. See, Louis Alvarez wasn't just some guy with an idea. He was a Nobel Prize winning physicist.

[Advertiser 2]

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

[Rund Abdelfattah]

By the way, this is Alec Navala Lee.

[Advertiser 2]

I am a novelist, critic and biographer.

[Rund Abdelfattah]

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

[Advertiser 2]

Born in 1940, his father was occupied elsewhere.

[Rund Abdelfattah]

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.

[Advertiser 2]

On the observation plane, following closely behind.

[Rund Abdelfattah]

The Enolake as it unleashed, for the first time in history, the power of a nuclear weapon onto a city of 350,000 people.

[Advertiser 2]

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 shockwave from the bomb hits the plane. So they feel it. They feel that shockwave even from the air and you can see the mushroom cloud. But when he looks down, he thinks that they missed. It's so empty that he thinks that they missed entirely.

[Rund Abdelfattah]

Peering out the plane window at the devastation 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.

[Ann Druyan]

Dear Walter, this is the first grown up letter I've 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.

[Advertiser 2]

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.

[Ann Druyan]

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

[Advertiser 2]

He's trying to in some ways justify it to himself.

[Ann Druyan]

What regrets I have.

[Advertiser 2]

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

[Ann Druyan]

Japanese civilians this morning are tempered with the hope that this terrible weapon we have created may bring the countries of.

[Advertiser 2]

The world together and prevent from further wars.

[Ann Druyan]

Alfred Nobel thought his invention of high.

[Advertiser 2]

Explosives, dynamite, you know, Nobel's invention would.

[Ann Druyan]

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

[Advertiser 2]

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.

[Ann Druyan]

Our new destructive force is so many thousands of times worse that it may.

[Rund Abdelfattah]

Realize Nobel's dream, the dream of ending all war.

[Advertiser 2]

Walter did not read it until much later.

[Rund Abdelfattah]

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.

[Advertiser 2]

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

[Rund Abdelfattah]

Meanwhile, his relationship with his son grew more distant.

[Advertiser 2]

But eventually, Walter did read that letter.

[Ann Druyan]

Dear Walter.

[Ramtin Arablouei]

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

[Advertiser 2]

An idea has just occurred to him.

[Ramtin Arablouei]

He's staring at this gift Walter had given him, a chunk of rock from.

[Advertiser 2]

Gubbio, which shows the KT boundary, which.

[Ramtin Arablouei]

He'D never seen before.

[Advertiser 2]

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

[Ramtin Arablouei]

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

[Advertiser 2]

It's almost an emotional reaction.

[Ramtin Arablouei]

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

[David Sapkowski]

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

[Ramtin Arablouei]

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, then we can.

[David Sapkowski]

Be pretty sure that they must have gotten formed at the same time.

[Ramtin Arablouei]

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.

[David Sapkowski]

Core, doesn't naturally occur on Earth.

[Ramtin Arablouei]

Where can you find it?

[David Sapkowski]

It tends to be found more in meteorites and asteroids.

[Advertiser 2]

What happens is that they find iridium.

[Ramtin Arablouei]

Like too much of it, 30 times.

[Advertiser 2]

As much as they are expecting.

[Ramtin Arablouei]

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

[David Sapkowski]

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

[Ramtin Arablouei]

They run more tests with samples from different parts of the world, and after.

[David Sapkowski]

A couple of years in 1980, concluded the only place it could have come from was a very large asteroid.

[Ramtin Arablouei]

A very large asteroid.

[Rund Abdelfattah]

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.

[Advertiser 2]

And Walter knows better, right? He knows that they're going to be very skeptical.

[Rund Abdelfattah]

Soon after, in June 1980, they published a paper with their findings, a very.

[David Sapkowski]

Long paper in the journal Science.

[Rund Abdelfattah]

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.

[Advertiser 2]

Reminds them of stuff like the flood narrative.

[Rund Abdelfattah]

It sounds religious, it sounds biblical.

[Advertiser 2]

Yeah, to them it sounds like crackpot science.

[Rund Abdelfattah]

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.

[David Sapkowski]

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.

[Ramtin Arablouei]

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.

[David Sapkowski]

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

[Carl Sagan]

A new consciousness is developing which sees the Earth as a single organism and recognizes that an organism at war with itself is doomed.

[Ramtin Arablouei]

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.

[Carl Sagan]

We are one planet.

[Ann Druyan]

I am Paul Ecklaw from Petaluma, California.

[Carl Sagan]

You're listening to Throughline from npr.

[Advertiser 2]

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[Rund Abdelfattah]

Part 2 It's the end of the World as we know It.

[Carl Sagan]

Whatever happened to the dinosaurs? That's one of the great mysteries of archaeology.

[Ramtin Arablouei]

By the early 1980s, Louis and Walter Alvarez's daughter dinosaur hypothesis was starting to get attention. In local papers, on TV and radio.

[Carl Sagan]

Alvarez says that an asteroid crashed into the Earth and wiped out the dinosaurs.

[Ramtin Arablouei]

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

[Brian Toon]

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

[Rund Abdelfattah]

Enter Brian Toon.

[Brian Toon]

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.

[Rund Abdelfattah]

Brian had grown up in the shadow of the Cold War, and by the time he was at NASA in the.

[Brian Toon]

Early 80s, there were 70,000 nuclear weapons on the planet.

[Rund Abdelfattah]

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

[Brian Toon]

70,000 nuclear weapons.

[Rund Abdelfattah]

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.

[Ramtin Arablouei]

Then Brian called up a friend of his, Richard Turco, who worked for a company called R and D Associates, which did research for the Pentagon and Department of Energy and had already done modeling of nuclear explosions.

[Rund Abdelfattah]

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?

[Brian Toon]

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

[Ramtin Arablouei]

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

[Brian Toon]

Let me go think about that.

[Ramtin Arablouei]

So he went out, ran the numbers.

[Brian Toon]

Tens of thousands of weapons go off.

[Ramtin Arablouei]

And concluded they're going to put enough.

[Brian Toon]

Dust into the upper atmosphere to cause a big climate problem.

[Rund Abdelfattah]

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.

[Brian Toon]

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.

[Ramtin Arablouei]

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.

[Brian Toon]

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

[Ramtin Arablouei]

A long winter. 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.

[Rund Abdelfattah]

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. So we call up Carl, Carl Sagan.

[Carl Sagan]

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

[Rund Abdelfattah]

Yes, that Carl Sagan.

[Carl Sagan]

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

[David Sapkowski]

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

[Carl Sagan]

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

[Rund Abdelfattah]

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

[David Sapkowski]

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

[Carl Sagan]

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

[David Sapkowski]

Billions and billions, you know, that was sort of his catchphrase.

[Alec Navala Lee]

He was completely authentic.

[Rund Abdelfattah]

This is Ann Druyan. She co wrote and co created Cosmos with Carl. And from the moment they'd met, I.

[Alec Navala Lee]

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

[Rund Abdelfattah]

Her life would never be the same.

[Alec Navala Lee]

There was no facade, God, there was no baloney. There was no presentation of self to impress.

[Rund Abdelfattah]

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.

[Brian Toon]

You gave him an idea, he would respond to that idea, and he'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.

[David Sapkowski]

He had this gift for not just kind of 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, you know, hundreds of millions of years ago? It was thinking about why science gives us insight into the big questions that matter about existence.

[Ramtin Arablouei]

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.

[Alec Navala Lee]

I'm pretty sure it was named Nuclear Winter in my living room.

[Ramtin Arablouei]

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

[Brian Toon]

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.

[Rund Abdelfattah]

Why was it seen as being so threatening?

[Brian Toon]

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

[Ramtin Arablouei]

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.

[Brian Toon]

Thought, you know, 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 about it. We are just as naive as Louis Alvarez, who thought nuclear weapons would end wars.

[Ramtin Arablouei]

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

[Brian Toon]

Carl's pretty much a loose cannon.

[Carl Sagan]

Here now reporting from Washington, Ted Cobble.

[Rund Abdelfattah]

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

[David Sapkowski]

Most watched news program at the time.

[Rund Abdelfattah]

Was hosting a roundtable all about nuclear weapons.

[Carl Sagan]

We are joined here in Washington by a live audience and a distinguished panel of guests.

[Rund Abdelfattah]

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

[Carl Sagan]

Former Secretary of State Henry Kissinger, William F. Buckley Jr. Former Secretary of Defense.

[David Sapkowski]

Robert McNamara, along with Holocaust survivor Elie.

[Rund Abdelfattah]

Wiesel and former National Security Advisor Brent Snowcroft.

[David Sapkowski]

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

[Rund Abdelfattah]

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 U.S. copy.

[Advertiser 2]

This is not an exercise, Roger.

[Carl Sagan]

Understand, Major Reinhardt. We have a massive attack against the.

[Ann Druyan]

U.S. mission at this time.

[Carl Sagan]

Over 300 missiles inbound now.

[David Sapkowski]

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

[Rund Abdelfattah]

Hello, is anybody there?

[David Sapkowski]

Anybody at all? 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.

[Rund Abdelfattah]

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.

[Carl Sagan]

I think that this film presents a very simple minded notion of the nuclear problem.

[Rund Abdelfattah]

Neither was William F. Buckley Jr.

[Carl Sagan]

The guy who wrote it says, I would like to see people starting to question the value of defending this country with a nuclear arsenal.

[David Sapkowski]

But Sagan Sagan turns to the camera.

[Carl Sagan]

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

[David Sapkowski]

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.

[Carl Sagan]

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

[Rund Abdelfattah]

It was a mic drop moment.

[Carl Sagan]

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.

[Ramtin Arablouei]

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 Ann made sure people outside of the scientific community kept talking about it. That same year, they wrote an article together explaining the theory in one of the most popular publications of the Parade.

[Alec Navala Lee]

Magazine because it was inserted in the Sunday papers across the nation, which most.

[Ramtin Arablouei]

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.

[Alec Navala Lee]

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

[Ramtin Arablouei]

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.

[Alec Navala Lee]

People are used to having a shaman goes back 100,000 generations, you know, since we've been telling stories to each other and night around the campfire.

[Rund Abdelfattah]

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.

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My name's Amanda.

[Alec Navala Lee]

I'm calling from Portland, Maine and you're.

[Advertiser 1]

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[Rund Abdelfattah]

Part three. The pale blue dot.

[Alec Navala Lee]

I remember it vividly. Carl would have a look on his face like he had something really great to tell me. And he said, I've been told that Gorbachev wants to know more about nuclear winter.

[Rund Abdelfattah]

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

[Alec Navala Lee]

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.

[Rund Abdelfattah]

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

[Alec Navala Lee]

He came back from this meeting.

[Rund Abdelfattah]

Ann could instantly tell it went well.

[Alec Navala Lee]

He was completely energized.

[Rund Abdelfattah]

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

[Alec Navala Lee]

Mostly he was really talking about just how interested they were and how sober, how sober they were at this information, you know. The possibility that there could be a. A nuclear winter was a waking Nightmare.

[Ramtin Arablouei]

It was 1986 when Karl got that invitation to meet with Gorbachev. He'd spent the years since the parade article on a campaign to warn the world of the existential threat of nuclear war going everywhere, spreading the gospel of nuclear winter.

[Alec Navala Lee]

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

[Ramtin Arablouei]

He hosted a TV special for months.

[Carl Sagan]

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

[Ramtin Arablouei]

Gave lectures around the country.

[Carl Sagan]

Anything that involves the future is fundamentally.

[Ramtin Arablouei]

Threatened by the danger of nuclear war, testified before Congress.

[Carl Sagan]

One response by a senior practitioner was the following. He said, look, if you think that the mere 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.

[Ramtin Arablouei]

He even met with the Pope at the Vatican.

[Alec Navala Lee]

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

[Ramtin Arablouei]

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

[Ann Druyan]

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

[Ramtin Arablouei]

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

[Ann Druyan]

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.

[Alec Navala Lee]

He's competing views of what the world economy should be.

[Ann Druyan]

There was a technology race. Computers were advancing rapidly.

[Alec Navala Lee]

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

[Ramtin Arablouei]

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 to try.

[Ann Druyan]

To beat the drum of disarmament. And that nuclear winter demonstrated that nuclear war was unwinnable.

[Alec Navala Lee]

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

[Ramtin Arablouei]

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

[Ann Druyan]

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.

[Carl Sagan]

Many of you seriously believe that a nuclear freeze would further the cause of peace.

[Brian Toon]

But a freeze now would make us.

[Ramtin Arablouei]

Less, not more, more secure and would.

[Carl Sagan]

Raise, not reduce the risks of war.

[Rund Abdelfattah]

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

[Ann Druyan]

The Strategic Defense Initiative, better known as Star Wars.

[Brian Toon]

Let me share with you a vision.

[Ramtin Arablouei]

Of the future which offers hope.

[Rund Abdelfattah]

Reagan proposed a high tech space shield that would shoot down enemy nukes before they could strike the U.S. 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?

[Ann Druyan]

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

[Carl Sagan]

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

[Rund Abdelfattah]

Carl Sagan was a vocal opponent of Star Wars.

[Carl Sagan]

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 a first strike. Soviet leader Mikhail Gorbachev condemned the US Star wars missile defense program, warning that it will increase the risk of accidental war.

[Rund Abdelfattah]

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.

[Ramtin Arablouei]

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

[Alec Navala Lee]

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 reality even, you know, was just the headline always about him. We just didn't want to be complicit.

[Ramtin Arablouei]

Ann 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.

[Alec Navala Lee]

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.

[Ramtin Arablouei]

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, 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.

[Advertiser 1]

Since the original nuclear winter.

[Ann Druyan]

Idea was proposed, the several groups have.

[Carl Sagan]

Tried to study the problem, and each has come up with a different computer model for the global effects of nuclear war.

[Ann Druyan]

I learned something about science through that period. New science often leads to more questions, and that was absolutely the case for nuclear winter.

[David Sapkowski]

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

[Ann Druyan]

David Sapkosky Again, nuclear winter essentially exists in data, in models, and models are highly imperfect simulations of how the world works.

[David Sapkowski]

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.

[Ann Druyan]

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 this wave. And journalists like me were riding the wave too.

[Rund Abdelfattah]

By the mid-1980s, a few scientists had begun rebranding the theory nuclear Fall, a chill rather than the dramatic bitter cold.

[Ann Druyan]

Hypothesized for a nuclear winter.

[Rund Abdelfattah]

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

[Ramtin Arablouei]

Anybody who needs to know the weather.

[Rund Abdelfattah]

Report after a nuclear war in order.

[Advertiser 1]

To be deterred is already crazy.

[Rund Abdelfattah]

But one scientist, Fred Singer, disagreed and said it could actually bring on a nuclear summer.

[Carl Sagan]

What they've forgotten is that the smoke cloud also keeps in the heat.

[Rund Abdelfattah]

Singer was a prominent climate change skeptic, and it was later discovered that throughout his career he had been paid by oil and deposit 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.

[Ann Druyan]

Professional purveyors of uncertainty.

[David Sapkowski]

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

[Ann Druyan]

Just frame the questions around overstatement and uncertainties being the real story on any issue.

[Ramtin Arablouei]

And these voices got a lot of airtime.

[Ann Druyan]

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.

[Ramtin Arablouei]

And them fight at the same time. David Sapkowski 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.

[David Sapkowski]

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

[Alec Navala Lee]

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. As many people as possible should have the ability to do something to avert it.

[Ann Druyan]

This goes back to Plato and Aristotle and 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.

[Carl Sagan]

To prove a theory really means to get everyone to acceptance. And that's the a matter of personal taste. And the more evidence you see, the more likely you are to believe it.

[Rund Abdelfattah]

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.

[Carl Sagan]

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

[Brian Toon]

Both Gorbachev and Reagan wrote that the reason that they control nuclear weapons was because of this discovery of nuclear winter.

[Ramtin Arablouei]

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

[David Sapkowski]

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

[Ramtin Arablouei]

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 more most doubts about the dinosaur extinction theory.

[Rund Abdelfattah]

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

[Alec Navala Lee]

Human ever to walk in space.

[Rund Abdelfattah]

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

[Alec Navala Lee]

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?

[Rund Abdelfattah]

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.

[Carl Sagan]

The Earth is a very small stage in a vast cosmic arena.

[Alec Navala Lee]

When someone tells you that's Earth on it, as Carl brilliantly said, everyone you.

[Carl Sagan]

Ever love, everyone you know, everyone you.

[Alec Navala Lee]

Everyone you ever heard of, every human.

[Carl Sagan]

Being who ever was lived out their lives.

[Alec Navala Lee]

That's it. That's the reality of our true circumstances in the universe.

[Carl Sagan]

Think of the rivers of blood spilled by all those generals and emperors so that in glory and triumph they could become the momentary masters of a fraction of a.

[Alec Navala Lee]

You see how nonsensical it is to divide that planet up and to be willing to destroy it.

[Carl Sagan]

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.

[Rund Abdelfattah]

That's it for this week's show.

[Ramtin Arablouei]

I'm Rund Abdelfattah and I'm Ramtin Arablouei and you've been listening to Throughline from npr.

[Rund Abdelfattah]

This episode was produced by me and.

[Ramtin Arablouei]

Me Ant, Lawrence Wu, Julie Kane, Anya.

[Rund Abdelfattah]

Steinberg, Casey Minor, Christina Kim, Devon Kama, Sarah Wyman, Irene Noguchi. Voiceover work in this episode was done by Casey Herman. And thank you to NPR's Indicator podcast co host and reporter Waylon Wong for letting her husband Alec Navala Lee use her home studio to record with us for this episode.

[Ramtin Arablouei]

Thank you to Johnnette Oakes, Keandre Starling, Johannes Durgi, Tony Cavan, Nadia Lanci, Edith Chapin and Colin Campbell.

[Rund Abdelfattah]

Fact checking for this episode was done by Kevin Voelkel. This episode was mixed by Robert Rodriguez. Music for this episode was composed by Ramtin and his band Drop Electric, which includes Naveed Marvi, Sho Fujiwara, Anya Mizani.

[Ramtin Arablouei]

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

[Rund Abdelfattah]

Thanks for listening.

[Advertiser 1]

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