The sea is higher than we thought and millions more are at risk, study
finds
[March 05, 2026]
By SETH BORENSTEIN and ANNIKA HAMMERSCHLAG
Climate change's rising seas may threaten tens of millions more people
than scientists and government planners originally thought because of
mistaken research assumptions on how high coastal waters already are, a
new study said.
Researchers studied hundreds of scientific studies and hazard
assessments, calculating that about 90% of them underestimated baseline
coastal water heights by an average of 1 foot (30 centimeters),
according to Wednesday's study in the journal Nature. It's a far more
frequent problem in the Global South, the Pacific and Southeast Asia,
and less so in Europe and along Atlantic coasts.
The cause is a mismatch between the way sea and land altitudes are
measured, said study co-author Philip Minderhoud, a hydrogeology
professor at Wageningen University & Research in the Netherlands. And he
attributed that to a “methodological blind spot” between the different
ways those two things are measured.
Each way measures their own areas properly, he said. But where sea meets
land, there's a lot of factors that often don't get accounted for when
satellites and land-based models are used. Studies that calculate sea
level rise impact usually “do not look at the actual measured sea level
so they used this zero-meter” figure as a starting point, said lead
author Katharina Seeger of the University of Padua in Italy. In some
places in the Indo-Pacific, it's close to 3 feet (1 meter), Minderhoud
said.
One simple way to understand that is that many studies assume sea levels
without waves or currents, when the reality at the water's edge is of
oceans constantly roiled by wind, tides, currents, changing temperatures
and things like El Niño, said Minderhoud and Seeger.
Adjusting to a more accurate coastal height baseline means that if seas
rise by a little more than 3 feet (1 meter) — as some studies suggest
will happen by the end of the century — waters could inundate up to 37%
more land and threaten 77 million to 132 million more people, the study
said.
That would trigger problems in planning and paying for the impacts of a
warming world.
People at risk
"You have a lot of people here for whom the risk of extreme flooding is
much higher than people thought,'' said Anders Levermann, a climate
scientist at the Potsdam Institute for Climate Impacts Research in
Germany, who wasn't part of the study. And Southeast Asia, where the
study finds the biggest discrepancy, has the most people already
threatened by sea level rise, he said.
Minderhoud pointed to island nations in that region as an area where the
reality of discrepancy hits home.
For 17-year-old climate activist Vepaiamele Trief, the projections
aren't abstract. On her island home in the South Pacific archipelago of
Vanuatu, the shoreline has visibly retreated within her short lifetime,
with beaches eroded, coastal trees uprooted and some homes now barely 3
feet (about 1 meter) from the sea at high tide. On her grandmother’s
island of Ambae, a coastal road from the airport to her village has been
rerouted inland because of encroaching water. Graves have been submerged
and entire ways of life feel under threat.
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Children play on an uprooted tree along a beach in Mele, Vanuatu,
July 19, 2025, that was once lined with vegetation, now largely lost
to storms, erosion and other environmental pressures. (AP Photo/Annika
Hammerschlag, File)
 “These studies, they aren’t just
words on a paper. They aren’t just numbers. They’re people’s actual
livelihoods,” she said. “Put yourself in the shoes of our coastal
communities — their lives are going to be completely overturned
because of sea level rise and climate change.”
Paying attention to the starting point
This new study is pretty much about what is the truth on the ground.
Calculations that may be correct for the seas overall or for the
land aren't quite right at that key intersection point of water and
land, Seeger and Minderhoud said. It's especially true in the
Pacific.
“To understand how much higher a piece of land is than the water,
you need to know the land elevation and the water elevation. And
what this paper says the vast majority of studies have done is to
just assume that zero in your land elevation dataset is the level of
the water. When in fact, it’s not,” said sea level rise expert Ben
Strauss, CEO of Climate Central. His 2019 study was one of the few
the new paper said got it right.
“It’s just the baseline that you start from that people are getting
wrong," said Strauss, who wasn't part of the research.
Maybe not so bad, some scientists say
Other outside scientists said that Minderhoud and Seeger may be
making too much of the problem.
“I think they’re exaggerating the implications for impact studies a
bit — the problem is actually well understood, albeit addressed in a
way that could probably be improved,” said Gonéri Le Cozannet, a
scientist at the French geological survey. Most local planners know
their coastal issues and plan accordingly, Rutgers University sea
level expert Robert Kopp said.
That's true in Vietnam in the high-impact area, Minderhoud said.
They have an accurate sense of elevation, he said.
The findings come as a new UNESCO report warns of major gaps in
understanding how much carbon the ocean absorbs. That report said
that models differ by 10% to 20% in estimating the size of that
carbon sink, raising questions about the accuracy of global climate
projections that rely on them.
Together, the studies suggest governments may be planning for
coastal and climate risks with an incomplete picture of how the
ocean is changing.
“When the ocean comes closer, it takes away more than just the land
we used to enjoy,” said Thompson Natuoivi, a climate advocate for
Save the Children Vanuatu.
“Sea level rise is not just changing our coastline, it’s changing
our lives. We are not talking about the future — we’re talking about
the right now.”
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