NOEL KING, HOST:
Oceans are rising because of climate change. We know that. But how fast is it happening? To answer that with some degree of precision, climate scientists are digging into these dusty handwritten archives. Here's NPR's Lauren Sommer.
LAUREN SOMMER, BYLINE: Just off the coast of Liverpool, England, there's a small, windswept island known as Hilbre Island. No one lives there now, but in the late 1800s, a handful of people did. They ran a telegraph station, launched lifeboats and recorded the tide levels every day.
ANDY MATTHEWS: I can just about see some of the buildings.
SOMMER: Andy Matthews lives close to Hilbre Island, where the remains of those buildings still are. He's also a data scientist at the Permanent Service for Mean Sea Level, an organization that gathers ocean data worldwide. That's where those old tidal records are now kept, along with others, like from the Port of Liverpool. To help ships dock safely in the 1800s, workers there dutifully wrote down tidal data every 15 minutes in huge handwritten tables.
MATTHEWS: You can see some of them have a very intricate handwriting, and other ones are pretty squirrelly as well (laughter), so...
SOMMER: Altogether, it's tens of thousands of pages of extremely detailed scientific data.
MATTHEWS: We've never got them off the ledgers. So they're not in a digital format at the moment for us to use in our research.
SOMMER: Matthews is hoping to make it usable. He's posted them on a site called Zooniverse so volunteers can help. With many people stuck at home, he's hoping they'll pitch in with the transcription online. And it's not just about historical preservation; the data is crucial to understanding climate change because it sets the baseline.
THOMAS FREDERIKSE: One of the really difficult things of sea level rise is that it happens everywhere on a different pace.
SOMMER: Thomas Frederikse studies sea level rise at NASA's Jet Propulsion Laboratory. He says oceans are rising because glaciers are melting. So are the ice sheets on Antarctica and Greenland. The oceans are also warmer, and warmer water expands. So sea level could rise between 3 and 6 feet by the end of the century. But it'll be slightly different in every city.
FREDERIKSE: Sea level rise is not rising everywhere with the same speed. Like, for example, the U.S. East Coast has seen a lot of sea level rise.
SOMMER: It's not like a bathtub, where the water rises evenly. The Earth's crust is slowly changing all the time. A huge weight, like a massive ice sheet, pushes the crust down. When the ice melts, the Earth slowly rebounds, kind of like a cushion when you get off the couch. Frederikse says historical records reveal how these processes work, and that's key for forecasting future sea levels in different parts of the world.
FREDERIKSE: If we don't have that information, it's easy to be, like, a few feet off if we don't have local records of sea level.
SOMMER: There's a problem, though. Most of the historical records are from the U.S. and Europe.
ARIEL TROISI: The Southern Hemisphere - it's not really well covered.
SOMMER: Captain Ariel Troisi is technical secretary of the Naval Hydrographic Service of Argentina. He's been working to recover historical records from the Port of Buenos Aires to help fill in the gap of data from the Southern Hemisphere. On some papers, the ink is already fading.
TROISI: These observations are unrepeatable. So if we don't recover them, it's difficult to understand what has happened.
SOMMER: In Cameroon in Central Africa, tidal data is in the archives of former colonizers. As colonial powers extracted resources from African countries, they kept detailed maritime records. Ph.D. student Yannick Fossi Fotsi is piecing together records from when Germany and France took control of Cameroon, starting in the late 1800s.
YANNICK FOSSI FOTSI: (Speaking French).
SOMMER: "You can't accurately predict sea level worldwide without records from African countries," he says. But he's also hoping the data will provide a clearer forecast for his own country. Douala, the economic capital, already experiences extreme floods. To prepare a city of millions for sea level rise, they'll need detailed local forecast informed by records from the past.
Lauren Sommer, NPR News.
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