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

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.

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]

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.

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.

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]

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]

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]

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]

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

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.

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.