The Fellowship of the Tree Rings

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Bartender asks, What'll you have? Tree says.

Yeah.

Oh, you want to guess?

Well, no, I'm just I'm already. I'm already dismayed by your concept. Because trees, as I last checked, can't walk, they're rooted to the ground.

Just go with it, Lulu, just go with it, come on, okay. Tree walks into a bar.

I've got a branching decision ahead of me, but I'll go with a lager.

Anything but a lager. Oh, anything but a lager. Okay, that's right, another one.

Dendrochronologists are people who look at dendrites in your brain.

No, they. There are people who study tree rings.

Oh, they just look at the rings inside a tree stump.

That's what they do, that's what they study.

Okay, so three dendrochronologists walk into a bar, and.

I mean, that's, that's, that's, that's not a joke, that's the beginning of the story.

Okay.

The rest of the story is basically, um, three tree ring scientists walk into a bar. And as the night goes on and as the talk gets a little boozier, they come up with this kind of harebrained idea. To take this one particular set of tree rings to put it next to a seemingly unrelated thing. But in doing that, they start to see all kinds of new things that they've never seen before, that maybe nobody has ever seen before. Including an invisible hand shaping the history of our world and the history of us.

All right, well before we take off on this wild tail, should we do the who we are thing?

I'm Latif Nasser.

I'm Lulu Miller.

This, of course, is radiolab.

All right, so set it up for us. Where does it all start?

Okay, so we're in Tucson, Arizona, at a bar called Tiger's Taproom. Okay, it's more than 100 years old, and it's sort of famous locally for its very old bartender, who has been serving drinks there since 1959..

Cool, all. Right now, I'm picturing Gandalf like serving drinks to these three tree ring scientists sitting there, looking at the bar, counting the rings on the bar.

We're not freaks, we go to a bar, we go and drink, we don't count rings.

This is Valerie.

Valerie Trui.

Scientist number one.

And I'm a professor of dendrochronology at the University of Arizona.

Which is in Tucson.

Where you would not necessarily expect a tree ring lab because there's not many trees around.

But kind of weirdly, she says, this is actually where the modern field was born.

Because the first dendrochronologist was actually an astronomer.

Who was studying the Sun?

Andrew Ellicott Douglas. That happened because....

He thought to himself.

Well, trees, they're sensitive to the sun.

You know, they eat sunshine.

And they get to be very old, so maybe I can learn something about the sun from the rings in trees.

So it's like original astronomers recording their solar observations.

Yeah, exactly, huh?

But what could you actually learn about the sun from the rings, isn't it? Just like each year the tree grows, it gets a ring and you learn how old it is by counting them, like, is there a thing beyond counting the rings?

Yes, so it's a very good question.

So Valerie explained, Yes, it's true. Most trees grow a new ring every year.

But what fewer people know is that not every ring is equally wide, not every ring is equally dense, not every ring has the same chemistry.

Imagine those differences, Valerie says, where you can learn all kinds of stuff about the tree, and even stuff not about the tree.

Exactly.

So like what, like what?

Well.

How hot or how cold it is?

You can see how much it rains, storms or didn't droughts, you could see trauma.

Human history as well.

All kinds of stuff.

Okay, continue.

So back to Tucson, Valerie's at this bar to meet up with two other scientists because they're all in town for this big conference.

An International Tree Ring conference.

For all of the dendrochronologists in the Americas.

Is it like four people?

No.

Okay, how many people is it?

Oh, in total, yeah, I don't know, maybe 200 250 people.

A lot, and among them were Valerie's bar buddies, Marta, Spanish scientist.

Specialized in dendroarchaeology.

Studies the wood in shipwrecks.

What?

Yeah, like. She dives down and examines the rings in the wood of the hulls of the ships that wrecked hundreds of years ago.

Ah, yeah, the treasure is the wood.

Third one.

My name is Grant Harley.

Grant.

Originally from Florida.

He's a paleoclimatologist.

Associate Professor of Geography at the University of Idaho.

Uses tree rings to study past and future climate. So it's one of the nights of this conference.

I think it was the last evening of the conference.

That they hit the bar.

That they hit the bar, so they're sitting there drinking some beers.

Yeah, like, we're sitting around this table and we start talking about this research project that had going on.

And Grant says, something like, I've got a puzzle and I'm not quite sure how to solve it. And I'm wondering if you two can help me out. Okay, for the past few years, I've been doing this research down in Florida.

Like all the way, like almost to key west, right near the southernmost point of the U.S.

On this island.

It's called big pine key.

Big Pine key studying?

These really gnarly pine trees that are basically like big bonsai trees.

And he tells Valerie and Marta one day, who's out there, you know, just doing his normal research, which is like taking these pencil-shaped core samples from these trees.

They said he saw these tree rings.

These like really, really narrow rings.

So narrow, he could barely see them.

Super, super narrow, like, really, really small. That automatically tells you, like, wow.

Something bad happened here.

That tree was really stressed.

So he's going through the list of things that he knows can stress out a tree drought. Maybe it didn't rain that much.

Insects can have a different.

Maybe the tree got attacked by beetles or it was unusually cold.

He goes through the drawing board to find out what is the signal in these tree rings.

Until he comes up with a theory.

Hurricanes.

Hurricanes.

But wouldn't a hurricane make a fat ring because it's bringing so much rain?

Well.

Yeah, according to Valerie, a hurricane just shreds a tree.

It doesn't just lose its needles, it can also lose its big branches, obviously.

But how would you prove that?

Turns out.

Has this data set?

It's just a big list of all the hurricanes that have happened in the Atlantic since 1851 that the government made by combing through old newspapers.

And we compared that list.

To those years that he saw with very narrow rings.

And.

They matched bingo.

In other words.

He was right. They were caused by hurricanes.

And Valerie says this match was exciting on a couple different levels, for one thing....

I don't think I'd heard about using tree rings to reconstruct hurricanes.

It just felt like a new way to use tree rings to understand the world. But also it gave us new hurricane data, which we don't have a lot of.

Because there are so few of them, so it's hard to calculate how frequently they happen because you have so few....

Data points kind of.

Data points exactly.

And what Grant realizes is.

They go back another 150 years-ish, to 1707.

So Grant's thinking.

How do I prove this, that this is hurricanes?

And Marta?

Marta Dominguez del Mas.

Is like.

Entire fleets going down because of hurricanes. And so I just spit it out. I'm like, what if we? what if we linked the two?

Like, what if you put the tree ring data?

Because if they do, we're seeing what.

Because if they do, it's like the shipwrecks and the tree rings are both showing us hurricanes.

It's like double reference, huh, got it?

Okay, so they have this idea at the bar that night. Literally the next morning, they get together and start looking around for a list of all the shipwrecks that have happened in that part of the world. And fortunately....

There's a very good record written documentary record.

They get their hands on this list. They eliminate the shipwrecks they know were caused by something other than hurricanes, or that are in the wrong area, or that were not in the right time of year. And then Grant takes that shipwreck spreadsheet....

I kid you not, they're almost identical.

They match.

You see the exact same pattern from shipwreck years to hurricane years with the tree rings.

So it's like, okay, fat ring, no shipwrecks, fat ring, no shipwrecks, fat ring, no shipwrecks, narrow ring, tons of shipwrecks.

And that?

Wow, there's something so like satisfying about possibly catching an objective, possibly an objective truth, an objective happening with these silent bystanders.

Yes.

It just feels harder to come by these days.

Yeah, you're spot on. That's what I really like about trees. You can't say the tree's saying this or the tree's saying that you can see it right there in the wood. You can't make it up.

Okay, and just so I am clear on what they are not lying about. What we've just learned is that the shipwreck data confirmed that Grant's skinny tree rings are in fact hurricanes, which means tree rings are now doubling the amount of hurricane data that we have.

Tripling.

So okay, so the hurricane data the government had at the beginning of all this went back to 1850, right? Then? The tree rings extended it back to 1700, so they added like 150 years. But now the shipwrecks extended back even further, all the way to 1495..

Yeah, 150 to 450 years, yeah.

Oh my god.

So these three tree ring scientists basically tripled all of the historical hurricane data that we had for the Caribbean, just by, like, lining up these three different data sets. So after they gathered this data, they sent it off to the people who make the hurricane models that, you know, predict how hurricanes are going to develop in the future. So now those models can make better predictions. Which could, in turn, you know, save tons of money and lives.

That is so cool.

Very cool.

Actually, this is we're still just at the beginning of this story. So our tree ring scientists, they sent off this data to the hurricane modelers, but they also kept it for themselves because they're scientists.

Trying to wring that sponge dry and get as much science out of that as possible.

And they want to see, what else can we notice here? Cut to a few months later.

I was staying in this really cheap motel in Flagstaff in northern Arizona.

Valerie was actually on a research trip for a different tree ring project.

But I was feeling really under the weather. And so while I was staying in and getting bored out of my head because I couldn't go do fieldwork, I went to a coffee shop.

She's at the coffee shop.

I ordered a coffee, I set myself at the window.

And she's like, I'll just kind of work here.

Pulled up the graph.

The graph of the 300 years of shipwrecks, which also kind of stand in for the hurricanes. But anyway, she'd been toying around with it, she hadn't really found anything interesting in it yet, but then?

I went to grab my coffee and when I went back.

From the counter.

Towards my laptop.

She noticed something in the graph that she hadn't seen when she was looking at it up close.

This dip.

From 1645 to about 1715, where there were virtually no wrecks.

No wrecks, that feels not hurricane-y.

Yeah, so like, kind of like a grace period or something like. It was like a 70 years of almost no hurricanes.

All the weathermen between 1645 and 715 were like, Back to you, doc.

Yeah.

So she's like, That's weird.

What is that period?

And the answer to that question? It does two things. It reveals the secret about the sun that you almost certainly did not learn in school. Okay, and it also shows how this moment.

Huh.

And we'll get to that after the break.

This week, on the New Yorker Radio Hour, a new series investigates a terrible mystery.

When Khaled got to the house, it was quiet.

No one seemed to be home and then someone came by and told Khaled the Marines had taken all the bodies to the hospital.

On the New Yorker Radio Hour.

Wherever you listen to podcasts.

Okay, okay, okay, okay. So we started a story. This is a story about a drunk idea with follow-through. That's right, they woke up the next morning and actually went and chased it out.

Nice.

So these scientists have chased down this wild idea. They've matched tree ring data with shipwreck data. It's allowed them to look deeper in the past than ever before. At Hurricanes, they discovered this weird lull.

Right, so Valerie sees this lull and she's like, that's weird, but also familiar.

The dates were 1645 to 1725.

The maunder minimum also called the maunder minimum. Okay?

What the heck is a maunder minimum?

It's a very well-known period of low solar activity, a period when the sun was weak.

Apparently the sun, the kind of solar radiation that comes from the sun, it's not constant. What?

So there are periods when the sun is like, my burner's on high, my burner's on low.

Yeah, when the sun is at its peak, it's called maximum, at its lowest point minimum.

So does that mean that during the maunder minimum, it was actually colder?

It was colder than yeah.

Huh, and would it be darker, or it would be just as bright, just as bright, just as bright, but just cooler?

Yep, exactly, I don't know if you've heard of the Little Ice Age.

I haven't. It started at the beginning of the 14th century and lasted roughly 500 years.

And it's kind of the opposite of what we're experiencing now, right? Rather than glaciers retreating, you have glaciers advancing.

According to Valerie, the coldest period of that little ice age was the maunder minimum.

The fact that the sun didn't have as much energy contributed to it being colder.

And the colder temperature of that period might have meant cooler oceans, which in theory, could mean less hurricanes.

Because the fuel that drives hurricanes is really warm at sea surface temperatures. if you don't have that, you really don't have a hurricane.

Huh.

So then that could explain why there were fewer shipwrecks.

During that time, yeah.

Hmm.

Why?

I just feel like for the deniers, for the human-caused climate change deniers. The phrase they bandied about all the time was like, No, there's natural cycles, it warms up, then it cools down.

Yeah, natural cycles can't predict the weather.

No, they do say that, yep.

So then is this showing that the sun does play some kind of role in climate change?

No, not at all.

This actually shows the opposite.

Record-breaking heat waves.

Dangerous heat waves As we all know, in the last few years, we have had the hottest years in the history of our planet summer heat wave, unprecedented heat wave. It's really hot.

We're in a week, even though it's so hot.

Yeah, exactly.

Right now, we're in the middle of a smaller, 11-year solar cycle. We hit the minimum in 2019, we're still ramping up.

A lot more heat is coming our way. Oh, no.

Yeah.

The period of the coldest period of the Little Ice age 1645 to 1750.

He recognized something else.

The golden age of piracy.

The golden age of piracy.

That's right, the golden age of piracy. Grant is a big fan of pirates. has been ever since he was a kid, turns out.

Are you going to tell me who?

Henry Morgan, A.

If I had a pistol, I'd shoot out your gizzard pin blackbeard.

Blackbeard, I be blackbeard. And even if you've never heard of any of those people, you've definitely heard of....

Pirates of the Caribbean.

Oh my gosh, really.

Yeah, you are without doubt the worst pirate I've ever heard of.

This is the age where the mythology of pirates of the Caribbean emerged.

This, by the way, is Matt Casey.

I am a specialist in the 20th century history of Haiti and Cuba at the University of Southern Mississippi.

He and Grant actually met on a bus on a field trip.

Two-hour bus, right?

To New Orleans.

And I'm not even sure that we talked the whole two hours, but very quickly within the conversation, we realized that we had a lot in common.

Among the things, their love for the golden age of piracy. And at some point, Grant asked him, Do you think that this lull in hurricanes that we found in our data could have caused the golden Age of piracy?

And I became really excited, because, yes, for a historian of the Caribbean, this just makes so much sense.

Matt says Of course, there's no one cause for anything in history. There are a million explanations for the golden age of piracy. There are social reasons, political reasons, economic, cultural. all these different reasons why pirates were in ascendancy at this time. But the fact is,....

Pirates spend a lot of time on the water. As fun as it is to see them as these kind of masters of the sea. Who just take a licking and can do whatever they want. They're absolutely vulnerable to the elements.

Like hurricanes, so less hurricanes could mean a better environment for pirating, yes.

Hmm.

But.

That was not my first thought.

Matt Casey says When he looks at this period of time, this lull in hurricanes, that lines up with the maunder minimum, that lines up with the golden age of piracy. He sees it lining up with a whole other thing.

This is the moment that shaped the history of the world in a way that people don't always recognize.

The world.

It sounds like an exaggeration, but that is not too hyperbolic.

And this moment, Matt says, is.

The Sugar Revolution.

The Sugar Revolution.

One of the first places where sugar production occurred on a large scale is in the Caribbean, probably 1620s or 1630s.

It was this massively pivotal moment in world history, Matt says, where European plantation owners brought thousands of people against their will.

Enslaved Africans, indentured Europeans.

Out to these islands in the Caribbean.

To produce sugar.

On an enormous scale.

To a sugar plantation as a factory in a field.

Between 1650 and 1725, hundreds of thousands, by some accounts, nearly a million people were kidnapped to work in the Caribbean. Many died.

Horrendous in the scale of human tragedy.

And in roughly that same time period, sugar consumption in Europe quadrupled.

That sugar produces massive amounts of wealth, so much so that European industrialization was actually paid for by how lucrative sugar was in the Caribbean.

A lot of historians, including Matt, argue that the profits from the sugar plantations were.

The startup capital of industrial capitalism in England.

And that these profits not only funded the industrial revolution, but essentially gave birth to modern capitalism itself. And the way Matt sees it. Part of what allowed for all of that to happen the boom in sugar production, the expansion in slavery, the birth of capitalism. Is this decades-long, maunder-minimum lull in hurricanes? It was a moment of calm weather that let the plantations flourish. The ships sail filled with pirates, but also enslaved people and sugar and money. This period of stability, it subtly enabled all of that to happen.

Okay, what does this all have to do with trees?

Right, so Trees is kind of the way they noticed this subtle Rube Goldberg machine that has been playing out over centuries, right?

Okay, meaning what? Yeah? What are the bells and whistles?

Right, okay, so basically these three scientists in this bar. They use a combo of information they got from tree rings and information about shipwrecks to discover. This 70-year period where the sun was dimmer, which somehow led to fewer hurricanes. And that 70-year period had this sort of disproportionate effect on agriculture, on basically slavery, on capitalism, on the way our modern world gets made, maybe.

This story is just ramping my fear. Like, does that give you anything other than just like, make you want to lie down?

No, I think it does, like, I think it's like we're like Meerkats, you know, we're like running around, foraging for little grubs. And then every once in a while, like one of us stands up and looks around. Like, that's to me what they did in the bar. Like, it's like one of those moments of like, standing up, looking around, being like, whoa, there's a big picture here.

This episode was reported by Latif Nasser with help from Aketi Foster-Keyes and Maria Paz Gutierrez. Produced by Maria Paz Gutierrez and Pat Walters with help from Aketi Foster-Keyes and Sachi Kichijima-Mulkey.

Mixed by Jeremy Bloom with mixing help from Arianne Wack, fact-checking by Natalie Middleton and edited by Pat Walters.

Big thanks this episode to Scott St. George, Nathaniel Millett, Michael Charles Stambaugh and Justin Maxwell.

That's all from us. Thank you so much for listening.

Go thank a tree.

Go thank a tree.

For its service to history.

And for its shade, that helps keep you cool by maybe one degree Celsius. Who knows? Yeah, all right.

Radiolab was created by Jad Abimrad and is edited by Soren Wheeler.

Lulu Miller and Latif Nasser are our co-hosts. Dylan Keefe is our director of sound design.

Our staff includes Simon Adler, Jeremy Bloom, Becca Bressler, Rachel Cusick, Aketi Foster-Keyes, W. Harry Fortuna, David Gable, Maria Paz Gutierrez, Sindunyana Sambandang, Matt Kielty, Annie McEwen, Alex Neeson, Sarah Khari, Anna Vasquez-Vaz.

Sarah Sandbach, Arianne Wack, Pat Walters and Molly Webster.

With help from Sachiki Tejima-Molkey.

Our fact-checkers are Diane Kelly, Emily Krieger and Natalie Middleton.

Hi, this is Jeremiah Barba, and I'm calling from San Francisco, California.

Leadership support for Radiolab science programming is provided by the Gordon and Betty Moore Foundation.

Science Sandbox, the Simons Foundation initiative and the John Templeton Foundation.

Foundational support for Radiolab was provided by the Alfred P. Sloan Foundation.