Climate Tipping Points And The Damage That Could Follow : Short Wave If Earth heats up beyond 1.5 degrees, the impacts don't get just slightly worse--scientists warn that abrupt changes could be set off, with devastating impacts around the world. As the 27th annual climate negotiations are underway in Egypt and the world is set to blow past that 1.5°C warming threshold,
Emily Kwong talks to climate correspondents Rebecca Hersher and Lauren Sommer about three climate tipping points--points of no return that could cause big changes to the Earth's ecosystems.

Email the show at shortwave@npr.org.

Climate Tipping Points And The Damage That Could Follow

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EMILY KWONG, HOST:

You're listening to SHORT WAVE from NPR.

Hey, SHORT WAVErs, Emily Kwong here with NPR climate correspondents Rebecca Hersher and Lauren Sommer. Hey.

REBECCA HERSHER, BYLINE: Hey.

LAUREN SOMMER, BYLINE: Hey there. So today, we have a story about how change happens. Changes like this...

(SOUNDBITE OF WATER FLOWING)

KWONG: Is that a rushing river, a waterfall?

SOMMER: Yeah, kind of. It's a sound that I recorded standing on a massive piece of ice. It's, like, two miles thick in the thickest part. It's the Greenland ice sheet.

KWONG: Oh, that's an important place. It also just sounds more like water than ice.

(SOUNDBITE OF WATER FLOWING)

SOMMER: Exactly. That's kind of the problem. The ice is melting as the Earth gets hotter, but it's not, like, this slow, steady process, where a little more warming means a little more melt, and so on and so on. At a certain point, it accelerates. It gets faster and faster.

HERSHER: And the big question is how much faster? Because all that meltwater is ending up in the ocean, and it's raising sea levels. And that will affect millions of people living on coastlines.

KWONG: But do you know when that's going to happen, if it's speeding up? Because knowing the timing of it all seems important, especially for people living in Greenland.

SOMMER: Exactly. Yeah. And there are changes like this one that are happening all over the world - right? - where there's these things like sea level rise. They go from relatively slow to happening much faster, which causes huge effects. And right now, the Earth is on track to hit several of these so-called tipping points.

KWONG: Tipping points, OK. And is that something that happens quickly, like one thing sets off a chain of events?

HERSHER: Not quite, or probably not quite the way you're thinking. Because we're talking about the timescale of Earth here. So nothing will be that rapid. You should think about these more like really big changes that will slowly happen over the course of decades or even centuries. But they're such big changes that everyone will feel their effects, and they'll be irreversible, in some cases.

KWONG: So today on the show, three climate change tipping points that humans could start experiencing, even in the next few decades, and what the world can do to avoid them or at least slow them down. You're listening to SHORT WAVE, the daily science podcast from NPR.

(SOUNDBITE OF MUSIC)

KWONG: All right, Rebecca and Lauren, so ice is melting as the climate gets hotter. That melt is speeding up, especially around the Earth's ice caps, these big masses of ice, like, in Greenland.

HERSHER: Right. So what's happening in Greenland, it's also happening in Antarctica, at the other end of the Earth. The ice is melting really fast, and that rate of melting is accelerating. And when we talk about these tipping points, these are really big changes, there's one part of Antarctica that's ground-zero - west Antarctica.

SOMMER: And there's kind of, like, this cascade of events happening there. West Antarctica has a lot of ice, and some of that ice is on the land. And then at the edges, the ice kind of extends out and floats on the ocean, and those parts are melting the fastest; so much so that some of it's, you know, cracking and breaking apart.

KWONG: Yikes. OK. And what happens to the rest of the ice when the floating ice out on the water breaks?

HERSHER: Well, you can think of the ice on the edge like a pie crust. It's holding all that ice on land back. Like, I like to think of it, personally, as a pumpkin pie. And that's because it seems like it's solid. But actually, if you were to totally remove the crust, eventually it would slump. It would just ooze out. And so when I think of this big ice sheet, that's what I imagine, this big pumpkin pie with pieces of crust just falling off.

SOMMER: I'm just going to say I - I'm going to think apple pie. I don't know.

HERSHER: All right.

SOMMER: I'm not going to science fact-check you here. But doesn't that seem more oozy? I don't think pumpkin pie oozes.

HERSHER: I don't know about your pumpkin pie. I'm lactose intolerant. So my pumpkin pie is, like, a little bit less firm.

KWONG: I don't know if that's the point here. The metaphor appears pie-like. You're saying that the ice, on the edges, if it disappears, the pie is not in good shape.

SOMMER: Yeah. Because all that melting ice makes sea levels rise. And once that melting process gets going, it really gets going. It's an abrupt change.

KWONG: But as we discussed, abrupt to whom - to people around Antarctica, to planet Earth - who will feel this and when?

HERSHER: So it will take a while. It will take anywhere from 100 years to hundreds or even 1,000 years for the whole piece of ice to collapse.

KWONG: That is a massive range. Like, you and I will be long gone by the time that happens.

HERSHER: Yes. Yes, we will. But it still matters to a lot of us humans. Because first of all, we have to prepare for this, right? And there's a big difference between hundreds of years and thousands of years. We want to build roads and bridges and houses that won't be underwater in the future.

KWONG: Yeah.

HERSHER: So I talked to Ian Joughin about this. He's a climate scientist who studies melting ice sheets.

IAN JOUGHIN: We don't use a lot of infrastructure from 1,000 years ago. We do have a - quite a bit of infrastructure from 100 years ago. So just the scale that this collapse occurs on is quite important for how we're able to adapt to it.

SOMMER: And humans kind of control that timeline, to some extent. I mean, to be clear, sea level rise is already happening now. There's melt happening now. But when it comes to this collapse process that we're talking about, the hotter the Earth gets, the faster it heats up, the sooner that collapse could happen. And because these ice sheets are so big, they have a lot of inertia. It's really hard to stop this process once it starts.

KWONG: OK. So you're saying that ice melt is almost a runaway effect. It happens, and then it builds and builds. Let's talk about the second climate-tipping point. What big-scale change speaks volumes to you?

HERSHER: I'm really glad you asked. I want to take you to the Arctic but not to the ice. I want to talk about the ground. The permanently frozen earth in the Arctic is thawing. And, like the ice sheets, that's happening faster and faster. It's accelerating. Like, I talked to a scientist named Merritt Turetsky at the University of Colorado in Boulder, and she's been watching the ground thaw in the Arctic for decades.

MERRITT TURETSKY: We are saying goodbye to the permafrost in field sites where I've been monitoring permafrost change for 20 years now.

KWONG: Yeah, melting permafrost, it is a major problem for Arctic coastline communities. Not only - I've heard, you know, talking to folks - that is the ground disappearing beneath you, sometimes taking your backyard and your house along with it. But it has all these ripple effects on transportation, on public safety, on community life. Traditional hunting grounds diminish. And in places where subsistence is the way of life, it can make having enough to eat a real challenge.

HERSHER: Yeah, yeah, I know you've really grappled with this because you lived in Alaska. You have a lot of friends there. It's also really bad for people who live far away from those areas, though, because permafrost stores a huge amount of carbon dioxide and methane, the stuff that's heating our Earth up. So when the ground thaws, it releases some of that carbon into the atmosphere. And the faster it thaws, the more extra greenhouse gas emissions there will be in 10, 20, 50, 100 years.

KWONG: We don't talk about that enough. That's absolutely true. And it's a feedback loop that really worries me, that more warming means more thawing, means more emissions, means more warmth. And it's like we're caught in this climate death spiral.

HERSHER: Yes. Yes. Although, like ice melt, humans do have some control over how bad this gets. Like, if humans stop burning fossil fuels, it will help.

TURETSKY: The faster we can decarbonize society today, the more permafrost carbon we can keep in the Arctic ground, where it belongs.

KWONG: It's really as simple and as complicated as that. So we've talked about permafrost. We've talked about ice melt. Anywhere else where runaway global warming is nearing a tipping point for you both?

SOMMER: Yeah. We got one more tipping point for you today. And it's a really tough one for the scientists who study it, like Erik Franklin. He's at the University of Hawai'i at Manoa, and he studies coral reefs.

ERIK FRANKLIN: It's difficult. I mean, it's - you hope the models are wrong.

KWONG: OK, I think I know where this is heading.

SOMMER: Yeah. You know, coral reefs, they're incredibly rich ecosystems. They're actually, like, a really small part of the ocean, but they support around a quarter of all marine life. And they're very sensitive to heat. So as ocean temperatures get hotter, marine heat waves are hitting coral reefs, and that stress bleaches them.

KWONG: And bleaching is where coral reefs turn that ghostly pale color, right?

SOMMER: Yeah, exactly. Yeah. They're actually expelling the algae that live inside them. The algae are kind of like their super-important roommates. They make food for corals. The bleaching doesn't necessarily kill coral reefs. They can bounce back after that. But after repeated heat waves, it's much, much harder.

KWONG: OK, so this is the third tipping point. I think I understand what you're saying now about tipping points, in relation to climate change. It's like you can't go back once this happens.

SOMMER: Yeah, especially for coral reefs because the whole ecosystem collapses. And the oceans are also getting more acidic due to climate change. Because they're absorbing a lot of that carbon dioxide that humans are putting into the atmosphere. So there's more stressors than just heat. And Erik worked on a study that looked at all those, plus things like pollution, and he found that by 2035 - so not that far away - half of all coral reefs worldwide will be in conditions where they probably can't survive. And yeah, that's a huge hit to biodiversity. It's also big for the millions of people who depend on coral reefs for their food and for their livelihoods.

FRANKLIN: There's entire societies and economies that are built around reef systems, especially in equatorial and tropical regions. And so these societies will be in dire straits.

KWONG: So that's the next 15 years. But beyond that, are we going to one day live in a world where there are no coral reefs, where they'll all die off?

SOMMER: I mean, that's a real question that people are trying to figure out. Because it really matters how much warming there is. If humans can keep it to that 1.5 degrees Celsius goal, some corals have a chance. Beyond two degrees of warming, it's estimated that 99% of all coral reefs will die.

HERSHER: And that difference, whether it's 1.5 versus two degrees, or even more than that, that matters a lot to all three tipping points, really.

KWONG: Yeah. You - we talked about this last time you were on the show, that if we maintain the status quo, if we don't do anything, we are on track to exceed two degrees of warming, right?

HERSHER: Yeah. Yeah, we are. Now, it is possible to keep warming to two degrees or less. We're not doing that right now. Humans are on track to blow past that temperature limit. Greenhouse gas emissions would need to plummet, basically, immediately to avoid that. The thing that I really try to remember and that multiple scientists have pointed out to me during this reporting, is that every 10th of a degree really matters.

SOMMER: Because the slower the climate change happens, the better, right? I mean, the idea is to just stave off these big abrupt changes. Or if we can't do that, we can at least delay them, so humans have time to get prepared and adapt.

KWONG: Yeah. These next 15 years are going to be really important for taking some of these actions, making these decisions. And that's what world leaders are trying to do at COP27 right now - right? - these climate negotiations that are about halfway done in Egypt.

HERSHER: Yeah.

SOMMER: Yeah. Yep.

HERSHER: Yeah, exactly. And we'll be back, soon actually, once they wrap up, to tell you how that all went.

KWONG: OK. I look forward to that. Thanks so much.

HERSHER: You're welcome.

(SOUNDBITE OF MUSIC)

KWONG: This episode was produced by Margaret Cirino. It was edited by Gisele Grayson, who is our senior supervising editor, and fact-checked by Abe Levine. The audio engineers were Tre Watson and Neal Rauch. Brendan Crump is our podcast coordinator. Our senior director of programming is Beth Donovan. And the senior vice president of programming is Anya Grundmann. You're listening to SHORT WAVE, the daily science podcast from NPR.

(SOUNDBITE OF MUSIC)

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