Researching Ocean Level Rising From Historical Logs : Short Wave Archival records may help researchers figure out how fast the sea level is rising in certain places. Millions of people in coastal cities are vulnerable to rising sea levels and knowing exactly how fast the water is rising is really important. But it's a tough scientific question. NPR climate correspondent Lauren Sommer explains how scientists are looking to historical records to help get at the answer.

For more of Lauren's reporting, follow her on Twitter @lesommer. Email us at
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Saving Sea Level Records: What Historical Records Tell Us About The Rising Ocean

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Saving Sea Level Records: What Historical Records Tell Us About The Rising Ocean

Saving Sea Level Records: What Historical Records Tell Us About The Rising Ocean

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  • <iframe src="" width="100%" height="290" frameborder="0" scrolling="no" title="NPR embedded audio player">
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You're listening to SHORT WAVE from NPR.


Hey, everybody. Emily Kwong here with climate correspondent Lauren Sommer, who promises - at a time when many of us are still at home - to take us on a journey.

LAUREN SOMMER, BYLINE: Yes, a journey through space and time.

KWONG: Ooh. All right, where are we going?

SOMMER: We're going to a tiny, wind-swept island off the coast of Liverpool, England, called Hilbre Island. It's a tidal island, so it's connected to the mainland for part of the day, and then when the tide comes in, it's cut off.

KWONG: So it's an island sometimes.

SOMMER: Yeah. No one lives there right now. It's just somewhere people go for a daytrip. But the people who used to live out there, they had to keep track of the tides. In the late 1800s, there were a handful of people there that ran the small telegraph station and a lifeboat rescue station.

KWONG: Sounds like my kind of place. Sounds lovely.

SOMMER: (Laughter) They actually recorded the height of the tide every 15 minutes...


SOMMER: ...In these huge paper ledgers. And they did this for decades.

KWONG: I imagine a huge data collection.

SOMMER: Yeah. It's just a ton of data. And for a long time, it's been sitting in an archive because it seems kind of obscure, right?

KWONG: Yeah.

SOMMER: But now this data is becoming incredibly valuable because the oceans are rising increasingly fast in a hotter climate. And the key question is - how fast? Millions of people in coastal communities need to know that in order to prepare in some way, whether it's building infrastructure to keep the water back or just moving people out of the way.

KWONG: Yeah.

SOMMER: And scientists say a crucial way to make really detailed forecasts about the future is to find these long-running data sets from the past.


KWONG: So today on the show, why sea level rise is such a tricky problem for scientists to forecast and why they're racing to rescue historical records from around the world. You're listening to SHORT WAVE, the daily science podcast from NPR.


KWONG: So, Lauren, you sent me a picture of one of these century-old title logbooks. And it's so cool. It's really detailed. You can see where it says, 1 a.m., someone's written 13 feet; 1:15 a.m., 14 feet, 1 inch - in this really lovely old penmanship, tracking the tide. Did people really do this 24 hours a day, every day of the year?

SOMMER: They did. They had technology that actually made it easier, though. In the late 1800s, they developed an automatic system which had this float that rested on the surface of the water, and then it fed information to kind of a pen that recorded the movement. So then people just had to read off the values and put them into the ledgers. And this was done in other places, too, like near Hilbre Island, the Port of Liverpool also has a really long-running tidal record.

KWONG: That makes sense because this was the era of ships, right? Watercraft was the way that people and things got around.

SOMMER: Yeah, exactly. You had a lot of ships going in and out of port, and so there were shipping companies that had to keep track of the tides so it could be done safely. Today, some of those old records are archived at the Permanent Service for Mean Sea Level, which is an organization in the U.K. that gathers ocean data worldwide. Andy Matthews, a data scientist there, told me the data are pretty reliable, you know, most of the time.

ANDY MATTHEWS: There's one record where, at one point, there's a little hand-scrawled note saying, you know, no data this week because the tide gauge operate was off sick. You do get little insights now and then.

KWONG: Everybody needs a sick day, right?

SOMMER: Of course. And he says they're trying to organize a bigger effort to find these records because, you know, since they're kind of obscure, they're hard to find.

MATTHEWS: Yeah, they can be anywhere, these kind of things - in archives, in libraries. You know, I think quite often people don't - they'll be archives that you don't quite know what they are.

KWONG: Yeah, this is quite the quest. And an even bigger issue, I imagine, is that when they find them, the data is still stuck on those pages.

SOMMER: Yeah. Matthews and his colleagues, they've scanned about 16,000 pages.

KWONG: Whoa.

SOMMER: But, yeah, the numbers are on the page, and they haven't been digitized, so they're really not usable by scientists. They're trying to use computers to do it through character recognition, but, I mean, you saw that writing, right? It's kind of like, the script and the formats can be really hard to decipher.

KWONG: Yeah.

SOMMER: So Andy is hoping that the public will help. He recently put the images up on Zooniverse, a website, and so volunteers can kind of pitch in and read the numbers and type them up.

KWONG: I love this approach. I mean, we're all bored at home looking for something to do this pandemic, so why not some historical data entry? (Laughter).

SOMMER: Right. Yeah, I mean, it's data entry for a greater good.

KWONG: Seriously. But to get into the nitty-gritty of it, why exactly is it important to look at data from the 1800s to understand sea level rise today and into the future?

SOMMER: Right.

KWONG: Why does that matter?

SOMMER: Yeah. Right. I mean, it has to do with how complex sea level rise is because it's being caused by a number of different things. I mean, first, you've got glaciers melting, right?

KWONG: Yeah.

SOMMER: Hotter temperatures causes them to shrink, and that water runs off into the ocean. And the same thing is happening in Greenland and Antarctica, where there are these massive ice sheets on the land, and there's so much ice melting that it's measured in gigatons, and it's happening increasingly fast.


KWONG: And I know that oceans are also rising because the water itself is warming up, and hotter things expand, so the water is, like, taking up more space.

SOMMER: Yep, you got it. And actually, this is kind of cool. Sea level rise did slow down in the 1960s and '70s because that was the era of dam building around the world - when, you know, when these big reservoirs were being constructed. They held back so much water, it was actually measurable.

KWONG: Oh, that is so strange. And it really shows how we humans do impact the oceans. That's, like, a tangible detail of how quickly we can do that.

SOMMER: It's a huge scale. But it's not really a factor anymore because, you know, dams aren't really being built at the same rate these days.

KWONG: Got it. Yeah.

SOMMER: Anyway, since 1900, there's been about 8 inches of sea level rise. And by the end of this century, we could be looking at 3 to 6 feet of sea level rise or even higher, depending on how much carbon humans emit. But that's globally. The water is rising at a different pace, depending on where you are.

KWONG: Yeah. How exactly does that work? Because wouldn't the ocean fill evenly kind of, like when you fill a bathtub?

SOMMER: Actually, no. And here's where it gets a little weird. The Earth is slowly changing, slowly getting a different shape. Like, you know, when you've been sitting on the couch a while and you kind of get up and the cushion rebounds, like, morphs back into its old shape?

KWONG: Yeah. Not all couches. But sure. Theoretically, yes.

SOMMER: (Laughter) Well, OK, that same thing happens to the Earth's crust. During the last ice age - you know, kind of started waning 11,000 years ago - there was a lot of ice on Canada and Greenland. And it's super heavy, and it was pushing down the Earth's crust. Since that melted, the crust has been slowly rebounding. And that's actually not good for the East Coast, especially around the mid-Atlantic region because, you know, it's on the same tectonic plate as Canada and Greenland, and when one side goes up, the other side goes down.

KWONG: So what you're saying is where I live on the East Coast is on the lower end of the seesaw, basically.

SOMMER: Yeah, sorry.

KWONG: Like, we are sinking...

SOMMER: Sorry about that. Yeah (laughter).

KWONG: ...Slowly.

SOMMER: I mean, the East Coast has seen more sea level rise than other parts of the country. And then there's a whole bunch of other things that can cause that too. You know, ocean currents, these big things that span hundreds of miles in the ocean...

KWONG: Yeah.

SOMMER: ...They cause the water on one side of them to be higher than on the other side, you know. So because of currents and gravity, the oceans themselves are just kind of lumpy, which is why sea level rise is different everywhere.

KWONG: I am learning so much right now. You're basically saying is that sea level rise is local, essentially, and if cities want to plan for this and figure out what and who is at risk, they'll need tailor-made information for their location.

SOMMER: Yeah, and that's where these historical records come in. You know, they reveal what these geologic processes and ocean conditions are doing in each place.

KWONG: Right, right, right.

SOMMER: And that helps scientists refine their computer models, you know, which are those high-powered ways that we get forecasts about climate change. I spoke to scientist Thomas Frederikse at NASA's Jet Propulsion Laboratory about this, and he said local records really matter.

THOMAS FREDERIKSE: If we don't have that information, we're - easy to be, like, a few feet off if we don't have local records of sea level. So especially when we try to project, like, high water levels of, like, extreme sea levels - that's how we call them - it's very difficult to get an accurate picture of that.

SOMMER: But there is a big issue with the historical records they already have. Almost all of the ones that have been digitized come from Europe and North America.

KWONG: So what you're saying is we got to find more places, more Hilbre Islands, so to speak, with historical sea level data all around the world.

SOMMER: Yeah. And this is a problem across many kinds of climate data, actually. The Southern Hemisphere hasn't been covered as well with things like weather stations and other kind of data collection, historically. So there's just this big effort to find these historical records outside of Europe and the U.S. In Argentina, they're working to digitize records from 1905 that were taken at the Port of Buenos Aires. But to go back farther in some countries, it means looking at the records of former colonial powers that took control because when countries like, you know, the U.K. and Germany and France extracted huge amount of resources from colonies, you know, often through force, they did it largely through shipping.

KWONG: Colonialism - stealing and keeping a good record of it.

SOMMER: Yeah, pretty much. So right now in France, the National Hydrographic Service is digitizing these tidal records from dozens of their former colonies, from Madagascar to Vietnam. Some of those records, though, aren't as long running. You know, they were gathered as part of geographic mapping or, you know, to study an area where they were putting in a port project. But I spoke to one person who is working with the French to stitch together a longer-running record dating back through his country's colonial history.

YANNICK FOSSI FOTSI: Je m'appelle Yannick Fossi Fotsi.

SOMMER: Yannick is from Cameroon, and he's a Ph.D. student in France right now. He started in German archives because that was the colonial power in the late 1800s, until France took control. So he's gathered the French records as well, and then he did the Cameroon records after it became independent in 1960.

KWONG: Yeah, that's a really interesting project and just a clear example of how the legacy of colonialism continues to impact science today.

SOMMER: Yeah, yeah. I mean, it's digging through this legacy is how he's kind of finding these records. And there's really only one other long-term record in Africa, and that's from Dakar, Senegal. So he knows Cameroon could be crucial for improving global climate models. But it could also be really helpful for Cameroon itself.

FOSSI FOTSI: (Speaking French).

SOMMER: He told me that the country's largest city, Douala, sits right on the Atlantic coast in an estuary, and it's extremely vulnerable to flooding already. I mean, just last year, there was a huge flood that displaced thousands after really heavy rains. So when you add sea level rise to that, it just makes the flooding issue worse. So he's hopeful that the historical records he's finding will lead to more detailed forecasts about, you know, just how fast the ocean is rising there because Douala, like other cities, you know, needs to start preparing now. Communities need to decide whether to move out of the way or build some kind of protection. And time is running out.


KWONG: Well, Lauren, thank you for this global trip. And I didn't even have to rebound off my couch.

SOMMER: (Laughter) Right. Any time.

KWONG: And if you feel inspired to help out transcribing this old tidal data, we've got the link to that on our website.

This episode was produced by Thomas Lu, edited by Gisele Grayson with help from Maddie Sofia and fact-checked by Rasha Aridi. The audio engineer for this episode was Josh Newell. I'm Emily Kwong. Thanks for listening to SHORT WAVE from NPR.


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