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Wait, you're listening to Radio Lab from WNYC. Okay, I'm just gonna start. Tree walks into a bar. Okay. Bartender asks, what do 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. Okay. Yeah. Bartender says, what do you have? 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. Yeah.
Another one. Okay. Three dendrochronologists walk into a bar and... Okay, wait. Yeah. Dendrochronologists are people who look at dendrites in your brain. No, they're 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 not a joke. That's the beginning of the story. Okay. The rest of the story is basically 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 planet and the history of us.
All right. Well, before we take off on this wild tale, 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. Wow.
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 are freaks.
We go to a bar, we go and drink. We don't count drinks. This is Valerie. Valerie Truet. Scientist number one. And I'm professor of dendrochronology at the University of Arizona. Which is in Tucson. Where you would not necessarily expect a trimming 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. Like trees are the original astronomers recording their solar observations. Yeah, exactly. 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 the counting the ring? 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. And it's in 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... You could learn about the weather. How hot or how cold it is. You can see how much it rained. Storms. Or didn't. Droughts. You could see trauma. Yeah. You know, which could create a very skinny ring. You can see fires, which leave scars. Or bugs, which leave these red or blue stains. 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. Marta Dominguez del Mas. 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.
He's a paleoclimatologist. 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. So he says, for the past few years, I've been doing this research down in Florida, like all the way, like almost the Key West.
Right near the southernmost point of the U.S. On this island 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. And he notices something he hadn't seen before. ♪
These like really, really narrow rings. So narrow, he could barely see them. Super, super narrow, like really, really small. That automatically tells you that, 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 it different. Maybe the tree got attacked by beetles. Or it was unusually cold. Keep on going back to the drawing board to find out what is the signal in these tree rings. Until he comes up with a theory. Hurricanes. Hurricanes? Yes.
But wouldn't a hurricane make a fat ring because it's bringing so much rain? Well, I mean, a hurricane, as you know, is pretty powerful. 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... Noah. Noah, as in the government weather people... 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 of 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 he might be sitting on a lot more hurricane data points because his trees, the trees with the skinny rings that seem to represent hurricanes, they go back way...
way further than the government data. Correct. They go back another 150 years-ish to 1707. So Grant's thinking he might be able to use his tree rings to almost double the amount of historical hurricane data we have for this part of the world.
Problem is, he now needs something outside of the tree rings to prove that. And this is essentially the puzzle that he brings to Valerie and Marta at the bar. How do I prove this, that this is hurricanes? And Marta... Marta Dominguez del Mas. Is like, it's funny you say that because a lot of the shipwrecks I dive at...
wrecked because of hurricanes. 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, where you have the skinny rings that you think are hurricanes, next to a big list of all the shipwrecks that happened for the last few hundred years? Would they match up? 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. So, 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 of the Spanish shipping trade from 1492 up until it ends around 1825. And when they would wreck it,
They would keep track of where they wrecked, when they wrecked, why they wrecked, whether it's pirates or hurricanes. 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, you know, were not in the right time of year. And then Grant takes that shipwreck spreadsheet and merges it with the free-ring spreadsheet
And I kid you not, they're almost identical. They match. You see the exact same pattern when you compare the 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, yeah, that was the moment where I'm like, yeah, this is it. This is working. Oh, wow.
There's something so satisfying about possibly catching an objective, possibly, an objective truth, an objective happening with these silent bystanders. It's just like...
A tree. 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 a tree's saying that because you can see it right there in the wood. You can't make it up. It's right there. Trees don't lie. Okay, and just so I am...
clear on what they are not lying about. I think 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. Hmm.
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'm just going to 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 good.
Hurricane-y? Yeah. So like kind of like a grace period or something. Like it was like a 70 years of almost no hurricanes. And once you see it, you can't unsee it. All the weathermen between 1645 and 715 were like, back to you, doc. So she's like, that's weird. What is, what is that period? And the answer to that question is,
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, this 70-year stretch, this clear-skied time of very few hurricanes, sort of shaped the world we live in today. And we'll get to that after the break.
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I'm Maria Konnikova. And I'm Nate Silver. And our new podcast, Risky Business, is a show about making better decisions. We're both journalists who moonlight as poker players, and that's the lens we're going to use to approach this entire show. We're going to be discussing everything from high-stakes poker to personal questions. Like whether I should call a plumber or fix my shower myself. And of course, we'll be talking about the election, too. Listen to Risky Business wherever you get your podcasts.
Lulu. Latif. Radiolab. Lulu, why don't you just tell me what you have gotten? Where we are? Yeah, where we are. Okay, 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, this time where there were less hurricanes. And then you were about to tell us how that lull shaped the modern world we live in today. Right. So Valerie sees this lull and she's like, that's weird, but also familiar. The dates were 1645 to 1725. I'm like, I know those dates somewhere from what is that period? Yeah.
It came to me pretty quickly. This period, this exact period is the Maunder Minimum. 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...
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.
Huh. So does that mean that during the Maunder Minimum, it was actually colder? It was colder than yet. 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 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.
That makes me feel weird. 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. What?
Check this out. Record-breaking temperatures. 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. It's going to be a brutal couple days. It's like we're setting records all over the place, right? Yep. Weather stations are logging a sea of red as temperatures hit record highs. All of this has happened at a time when we're not even at a maximum yet.
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. Okay, so back to this story. Okay. So Valerie was in the coffee shop. She saw the lull in the shipwreck data, and she recognized it as the Maunder Minimum.
But when Grant looked at that same time period... 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 this is common knowledge among pirate nerds, but...
In almost these exact same years, there was an explosion in bands of pirates basically robbing and hijacking ships. In the Caribbean specifically and in the Atlantic more broadly. Like it was when piracy became, first of all, more common, but also like became way more culturally visible. Many of the most famous pirates you know of came out of this very period.
Are you going to tell me who? Henry Morgan, a.k.a. Captain Morgan. Captain Morgan. He's real? Yeah. We have captured a Spanish galleon. And Bonnie and Mary Read. If I had a pistol, I'd shoot out your gizzard pin. 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. To our bus ride. 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 is
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. And so 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 this lull in hurricanes that lines up with the Mondra 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 didn't.
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 were...
indentured Europeans out to these islands in the Caribbean to produce sugar on an enormous scale. People refer 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 Europe.
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, we're... Okay, okay. What does this all have to do with trees? Right. So trees is kind of the way they noticed this, like, subtle Rube Goldberg machine that has been playing out over centuries, right? Okay. Meaning what? Yeah. What are the bells and whistles? Right. Okay, well, so basically these three scientists in this bar, they use a combo of information they got from tree rings and...
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 is all a big theory. And I think the thing that makes this story worth telling right now is like all of that, the Maunder minimum, their estimate is that that was about one degree Celsius of cooling. And now we are doing this to ourselves, but like in the reverse.
We are now the sun. Huh? Whereas the sun cooled the planet down by one degree. We are now turning up our own thermostat by two degrees. Maybe. Can we keep it to two degrees? Like, like to me, it's like, like we're changing our climate and what new possibilities and even kind of what new cruelties like, are we going to unleash? Are we going to open up?
I don't know. I don't know if you can say for sure. It's unimaginable. This story is just ramping my fear. Like, does that...
give you anything other than just, like, make you want to lie down and... No, I think it does. Like, I think it's, like, I think it's, like, so... We're like meerkats, you know? How so? We're, like, running around foraging for little grubs. Yeah. And then every once in a while, like, one of us stands up and looks around. Yeah. 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. Mm-hmm.
It takes those kinds of like bar, bus, whatever, wherever moments to like kind of sit back and be like, wait a second, all this stuff is connected. Like all this stuff is like we're trying to like divide up the world to make it comprehensible, but it's actually it's all woven together.
This episode was reported by Latif Nasser, with help from Akedi Foster-Keys and Maria Paz Gutierrez. Produced by Maria Paz Gutierrez and Pat Walters, with help from Akedi Foster-Keys 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. See you soon. Okay. Bye-bye.
Radio Lab was created by Jad Abumrad and is edited by Soren Wheeler. Lulu Miller and Latif Nasser are our co-hosts. Dylan Keith is our director of sound design.
Our staff includes Simon Adler, Jeremy Bloom, Becca Bressler, Rachel Cusick, Akedi Foster-Keys, W. Harry Fortuna, David Gable, Maria Paz Gutierrez, Sindhanyana Sambandang, Matt Kielty, Annie McEwen, Alex Neeson, Sara Khari, Ana Rasku-Edbaz, Sarah Sandbach, Arian Wack, Pat Walters, and Molly Webster. With help from Sacha Kirijimomolki. 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, Simons Foundation Initiative, and the John Templeton Foundation. Foundational support for Radiolab was provided by the Alfred P. Sloan Foundation.