Nature Quest: How High Will Sea Levels Rise?

Summary

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Short Wave — "Nature Quest: How High Will Sea Levels Rise?"

Date: September 30, 2025
Hosts: Emily Kwong (NPR), Rebecca Hersher (NPR Climate Reporter)
Listener Question: Peter Lansdale, Santa Cruz, California

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Episode Overview

This episode of Short Wave tackles a pressing listener question: How much will sea levels rise in the next few decades, and will that impact be the same everywhere? Hosts Emily Kwong and NPR climate reporter Rebecca Hersher dive into the scientific consensus on sea level projections, regional variations, and what can (and cannot) be done to slow sea level rise in the future. Using concrete data and a blend of humor and clarity, the episode guides listeners through why some regions are more vulnerable than others, what factors contribute to changes, and how to look up local projections.

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Key Discussion Points & Insights

1. Listener's Question and Framing

• Peter from Santa Cruz, CA, asks for sea level rise projections and wonders if there is scientific consensus on how many feet to expect in the next decades, especially since his region has seen recent coastal damage.
  • Peter: “We've seen a lot of damage recently on our coast ... But it would certainly accelerate if the sea was any higher than it already is. So I'm wondering if there's consensus on how many feet we're looking at.” [01:01]

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2. Global Scientific Consensus on Sea Level Rise

• Short-term projections are highly certain:
  • Rebecca: “Scientists have a really good idea of how much sea levels will rise in the next three decades or so.” [04:29]
• Concrete numbers:
  • Historical context: Seas are already about 9 inches higher than in the 1880s.
  • By 2050:
    • Global average sea level will be about 15 inches higher than the 1880s. [04:48]
• Confidence in data:
  • “They're really sure. So 2050 is actually pretty soon in scientific terms. ... Even if humans totally stopped burning oil and gas and coal today, there would be a lag ... that would take decades.” [05:15]
  • “There's not a lot of scientific uncertainty about what's happening in the couple decades between now and 2050.” [05:43]
• Short-term rise is “basically locked in,” meaning aggressive mitigation now won’t change numbers before 2050.

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3. Regional Differences—Not All Coasts Are Equal

• In Santa Cruz:

  • Projected rise is about 1 foot by 2050 compared to 2000. This is a little less than the global average. [06:04]
  • “There's not a lot of uncertainty about that number ... plus or minus a few inches.” [06:26]

• Other U.S. cities:

  • Seattle: Less than a foot
  • Annapolis, MD: About 1.5 feet
  • Galveston, TX: Upwards of 2 feet
  • New Orleans, LA: Almost 2.5 feet [07:47]

• Why do regions differ?

  • “The ocean is not static. It's not like a bucket of water ... It has currents moving through it.” [09:15] — Rebecca waxing Ben Hamlington (NASA/JPL).
  • “It's definitely not a bathtub. So it's not like it's just going up and down as though you're filling up a bathtub with a faucet.” [09:23] — Ben Hamlington [NASA].
  • Ocean currents, proximity to melting ice, and how the land itself is moving all play a role.

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4. Factors Affecting Local Sea Level Rise

• Thermal Expansion: Warmer water takes up more space.
  • “The ocean water is absorbing most of the extra heat … and when water absorbs heat, it expands.” [08:17-08:35]
• Proximity to Melting Ice: Near melting glaciers (e.g., Greenland), you see less sea level rise.
  • “If you live very close to an ice sheet … you experience less sea level rise. And that's basically because of how the water moves and also how the land that's under the ice changes as the ice melts.” [09:29]
• Land Movement (Subsidence and Uplift):
  • Sinking land raises relative sea levels faster.
  • “On the Gulf coast … where we have oil extraction … we actually cause the land to sink a little bit.” [11:12] — Ben Hamlington
  • “So when you combine the sea sinking land with the rising water, effectively what you get is faster sea level rise.” [11:16]

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5. How to Check Local Projections

• “Sea Level Rise Viewer”:
  • Ben Hamlington suggests this online tool (used by many local governments) to see projections anywhere in the U.S.
    • “You can just go to that source, which is called the sea level rise viewer. ... We'll put a link in the show notes.” [12:02]

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6. Can We Slow Sea Level Rise?

• Short-term (by 2050): Too late to make meaningful impacts through reduced emissions — "sea level rise in the next few decades is pretty unavoidable." [12:10]
• Long-term (beyond 2050): Significant difference if emissions are cut now.
  • "If humans stopped pumping planet warming pollution into the atmosphere now, sea level rise after 2050 would be a lot less severe." [12:10]
  • “That kind of extreme sea level rise [3, 4, even 10 feet] will happen if we do nothing and let all the ice sheets melt. But our choices today can avoid that.” [12:50]

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Notable Quotes & Memorable Moments

• “Scientists have a really good idea of how much sea levels will rise in the next three decades or so.”
  — Rebecca Hersher [04:29]

• “Globally, the oceans are about 9 inches higher today than they were in the 1880s.”
  — Rebecca Hersher [04:48]

• “So 2050 is actually pretty soon in scientific terms. ... Even if humans totally stopped burning oil and gas and coal today, there would be a lag while all that extra heat dissipated and the glacier stopped melting.”
  — Rebecca Hersher [05:15]

• “It's definitely not a bathtub. So it's not like it's just going up and down as though you're filling up a bathtub with a faucet.”
  — Ben Hamlington [09:23]

• “So it's either the sea's gonna rise to you, or you're gonna lower to the sea.”
  — Emily Kwong [11:12]

• “Sea level rise in the next few decades is pretty unavoidable. ... But our choices today can avoid [extreme sea level rise].”
  — Rebecca Hersher [12:10, 12:50]

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Timestamps for Key Segments

• 00:29 — Episode Introduction / Listener Question Introduced (Peter, Santa Cruz)
• 03:53 — Nature Quest Segment Begins; Setting up the consensus question
• 04:48 — Historical and 2050 Global Sea Level Rise Projections Discussed
• 06:04 — Santa Cruz-specific Projections Given
• 07:47 — Comparison of U.S. Cities (Seattle, Annapolis, Galveston, New Orleans)
• 08:17 — Explaining Thermal Expansion and Ice Melt Effects
• 09:02 — Ben Hamlington (NASA) on Why Sea Level Rise Differs by Region
• 10:27 — Thought Experiment: Land Sinking vs. Sea Rising
• 11:12 — Role of Land Subsidence Explained (Gulf Coast Example)
• 12:02 — How to Check Local Projections (“Sea Level Rise Viewer”)
• 12:10 — Implications for Climate Action Pre-/Post-2050

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Conclusion

The episode provides reassurance that the science of near-term sea level rise is solid: by 2050, much of what will happen is already determined, and about a 1-foot rise is expected for Santa Cruz (with more drastic rises elsewhere). After 2050, dramatic increases are possible — but major emission reductions now can help prevent truly catastrophic outcomes. Listeners are pointed to reliable tools for checking local projections and reminded that their choices in the coming decades can still shape the planet’s future.

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Explore more:
Check the “Sea Level Rise Viewer” (link in show notes) for town/region-specific projections.
Send your environmental science questions to Short Wave for future episodes.

Transcript

[A]

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[B]

You'Re listening to Shortwave from NPR. Hey, shortwavers, Emily Kwong here with NPR climate reporter Rebecca Hersher.

[C]

Hi.

[B]

Who is bringing us this month's listener question for Nature quest. Okay, Becky, what do you got?

[C]

All right. This month's question comes from a listener in Santa Cruz, California.

[B]

I love how we are automatically game show hosts right now welcoming onto the stage Santa Cruz. It's on the coast, right? It's an area a little bit south of San Francisco.

[C]

Yeah. I've actually never been there, but I've heard it's very gorgeous. I've seen pictures. There are cliffs, there are beaches. This listener, though his name is Peter Lansdale, is kind of worried about what's going to happen to that landscape in the future.

[D]

Hey, shortwave, this is Peter from San Cruz, California. I am wondering what the projections are for sea level rise in the next couple decades. We've seen a lot of damage recently on our coast, and to some extent that's normal because we're built on sandstone and everything is always changing here. But it would certainly accelerate if the sea was any higher than it already is. So I'm wondering if there's consensus on how many feet we're looking at.

[B]

All right. What do you think, Becky?

[C]

I love this question. I do. It's such a simple and important one. Yeah. Basically, is there a scientific consensus about how much sea levels will rise and how quickly it'll happen? And since we don't all live in beautiful Santa Cruz, we'll also answer a different question, which is, you know, is the amount of sea level rise that's happening different in California versus, say, Louisiana or Virginia?

[B]

So for this month's Nature Quest, we are tackling sea level rise, how fast it's happening, happening, what humans could do to slow it down and how to find out what the future looks like where you live. You're listening to Short Wave, the science podcast from npr.

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[B]

It is Nature Quest Day. This is my favorite segment. It's our monthly segment that brings you a question from a short waver who's noticing a change in the world around them. And we've brought on one of the best, Rebecca Hersher, climate reporter at npr. Okay, Becky, let's start with the first bit of Peter's question about sea level rise. Is there scientific consensus about how high the water will get?

[C]

An excellent question and a fun one to answer because the answer is yes.

[B]

Well, I guess that's it then. That's the episode. Okay, you've been listening to shortwave from npr.

[C]

Can you imagine we just end the.

[B]

Episode, get out of here.

[C]

Yeah, if only. If we're that simple. So basically the answer is yes, Scientists have a really good idea of how much sea levels will rise in the next three decades or so. Okay. And I'm going to give you some concrete numbers because just from listening to Peter, I kind of get the feeling that that is what he's yearning for.

[B]

Me too.

[C]

Yeah. Okay, so let's start really big picture. Globally, the oceans are about 9 inches higher today than they were in the 1880s. So that's the worldwide average for all the oceans everywhere. And sea level rise is accelerating. So by 2050, sea levels are projected to be about 15 inches higher than they were in the 1880s. Again, that's the global average, the whole planet.

[B]

How sure are scientists about those numbers?

[C]

They're really sure. So 2050 is actually pretty soon in Scientific terms. And it takes time for the planet to react to the extra heat that humans have trapped in the atmosphere. So. So even if humans totally stopped burning oil and gas and coal today, there would be a lag while all that extra heat dissipated and the glacier stopped melting. And that lag would take decades.

[B]

So this is all happening for sure, the next 25 years.

[C]

Yeah, there's just, there's not a lot of scientific uncertainty about what's happening in the couple decades between now and 2050.

[B]

Which means I guess scientists can be more confident.

[C]

Indeed.

[B]

So I'm hearing an average of about 15 inches of sea level rise globally by, by 2050. It's good for planning, imagining the future of different shorelines. But what about specifically in Santa Cruz where Peter lives?

[C]

Right, yes. So let's zoom in. Scientists expect about 1 foot of sea level rise in that area by 2050 compared to the year 2000. So that's a little less than the global average.

[B]

Why less? Is it something about how Santa Cruz is situated that makes it that way?

[C]

Not particularly. It's just sort of how the math. Maths when you look at Santa Cruz in the context of the whole planet.

[B]

Gotcha.

[C]

So again, there's not a lot of uncertainty about that number though. Like with any prediction about the future, there's going to be a range. So we don't know exactly how much planet warming pollution people are going to emit in the next couple decades. But okay, so there's not a huge range. So for the sea level rise in Santa Cruz, what about going up to 2050, the low end of that range is a little less than a half a foot high in just scientists, one foot. And so when we say there's a lot of certainty, that's what we're talking about, you know, compared to feel confident. So that's a sea level rise in that area about a foot by 2050, plus or minus a few inches.

[B]

Honestly, it's really nice to hear about something where there's not a lot of uncertainty. You know, there's so many science stories out there about what we don't know yet, the mysteries. But this sounds altogether not that mysterious.

[C]

Yeah, it's really not that mysterious. We know a lot about. Right. At least sea level rising short term science is very well understood about one.

[B]

Well, let's talk about the second piece of question. Not everyone lives in Santa Cruz, California rising faster in other parts of the.

[C]

U.S. yeah, there is variation. So here are some more numbers. You ready? So remember, in Santa Cruz there will be about a foot of sea level rise by 2050. In Seattle, it's less than a foot. In that same time period in Annapolis, Maryland, it's about a foot and a half.

[B]

Oh, close to where I live.

[C]

Yeah. In Galveston, Texas, upwards of two feet. And in New Orleans, it's almost two and a half feet. So it really varies depending on where you live in the US.

[B]

Again, like, why? It just doesn't make sense to me intuitively. Like, glaciers are melting. That should put extra water in the ocean. So why wouldn't the water just rise the same amount everywhere?

[C]

So, first of all, just one thing to note here. It's not just glaciers and ice caps that are melting that drive sea level rise. It's that the ocean water is absorbing most of the extra heat that's trapped by carbon dioxide and other greenhouse gases. And when water absorbs heat, it expands, it gets bigger.

[B]

Right.

[C]

Space. Yeah, we've talked about this before on shortwave. And that's also a big driver of sea level rise around the world. So, anyway, I just had to mention that before we go any further, but going back to your question, why do different places have such different amounts of sea level rise? Because I don't think I've fixed that problem.

[B]

Well, just because melting ice and expanding water both seem like they'd affect every part of the planet somewhat equally.

[C]

Yes, exactly. So I called up one of the top sea level rise scientists to talk about this.

[D]

My name is Ben Hamlington. I am a research scientist at the NASA Jet Propulsion Laboratory. I'm also team lead of the NASA Sea level change team.

[B]

Oh, cool.

[D]

And I study pretty much everything to do with sea level science and coastal impact.

[C]

So the first thing Ben pointed out is that the ocean is not static. It's not like a bucket of water. It has currents moving through it.

[D]

It's definitely not a bathtub. So it's not like it's just going up and down as though you're filling up a bathtub with a faucet.

[C]

So depending on where you are relative to ocean currents, you might see more rapid or less rapid sea level rise. And actually, if you live very close to an ice sheet, like in Greenland, for example, you experience less sea level rise. And that's basically because of how the water moves and also how the land that's under the ice changes as the ice melts.

[B]

Wait, that's really counterintuitive. So you're saying the closer you are to the melting ice that's causing sea level rise, the less sea level rise you personally experience?

[C]

Yeah, the Earth is Very weird and wonderful at times, clearly.

[B]

So the reason different places in the US Are experiencing more or less sea level rise is because of ocean currents and how close you are to melting ice.

[C]

Yeah. Those are two of the reasons. But in the US there's actually a third reason that's even more important, and that's about how the land itself is moving. So let's do a thought experiment. Emily Kwong, are you ready?

[B]

I'm ready.

[C]

Imagine. Imagine. Close your eyes. Imagine.

[B]

Yeah.

[C]

Imagine that you live in a house next to the ocean.

[B]

I wanted to before this story, but go on.

[C]

Yes. And your front door is one foot higher than the water. Okay. If the water rises one foot, you get wet.

[B]

Yeah.

[C]

Right. If the land sinks one foot, you are also wet. If the water rises six inches and the land sinks six inches, you're still wet.

[D]

That movement of land really does contribute to differences along the coastlines of the U.S. so, for example, on the Gulf coast of the U.S. where we have oil extraction, removal of things from underground, we actually cause the land to sink a little bit.

[B]

So it's either the sea's gonna rise to you, or you're gonna lower to the sea.

[C]

Yeah. So when you combine the sea sinking land with the rising water, effectively what you get is faster sea level rise. And in fact, Ben says the Gulf coast of the US has some of the highest sea level rise rates in the world because of this.

[B]

That's fascinating. Okay. And I feel like some people must be listening to this. I certainly am. And I'm wondering about my own home. Is there a way to find out how much sea level rise is predicted for your town?

[C]

Yes. So there are lots of different resources out there on the Internet, including from local governments, but actually, almost all of them use the same source material. And you can just go to that source, which is called the sea level rise viewer. Ben Hamlington, the scientist you heard from, worked on it, and we'll put a link in the show notes.

[B]

Sea level rise viewer. I'm gonna check it out. Becky, in the meantime, is there anything that can be done to slow sea level rise, especially beyond 2050?

[C]

Yeah, definitely. This actually goes back to the uncertainty piece we were talking about before. You know, sea level rise in the next few decades is pretty unavoidable. Like cutting greenhouse gas emissions wouldn't make a big difference right away, but that doesn't mean it's useless to pivot to cleaner energy. If humans stopped pumping planet warming pollution into the atmosphere now, sea level rise after 2050 would be a lot less severe. So just by using sources of energy like solar and wind, sources that don't emit as many greenhouse gases, we can still avoid really catastrophic amounts of sea level rise. And we're talking, you know, three, four, even 10ft higher than the ocean is today. That kind of extreme sea level rise will happen if we do nothing and let all the ice sheets melt. But our choices today can avoid that.

[B]

Rebecca Hersher, NPR Climate Correspondent, thank you for coming on shortwave. Thanks and thank you, Peter, for the great question. Shortwavers if you have a question about changes in your environment, please email [e-mail] and we'll consider it for a future Nature Quest episode. This series comes out the last Tuesday of every month. This episode was produced by Hannah Chin. It was edited by our showrunner, Rebecca Ramirez and Burleigh McCoy. Tyler Jones checked the facts. Jimmy Keeley was the audio engineer, Sam Poulson wrote and composed our Nature Quest theme music. Beth Donovan is our senior director and Colin Campbell is our senior vice president of podcasting strategy. I'm Emily Kwong. Thanks for listening to short wave from NPR.

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