Scientists spent the first few weeks of this year on an expedition to Antarctica to study the Thwaites Glacier, which is melting at an alarming rate. If it completely collapses, it could cause global sea levels to rise by two feet over the next few decades, affecting tens of millions of people around the world, according to a New York Times analysis.
The map below shows some of the coastal cities and densely populated low-lying areas that could be under threat if the glacier were to collapse today.
kolkata, india
1.7 million
These are just the minimal effects that Thwaites’ collapse could have on the world’s coastlines. When the glaciers collapse, global warming causes Greenland’s ice to melt, expanding the ocean’s volume and causing sea levels to rise further. And Thwaites acts as a plug, holding back much of the Antarctic glaciers on the surrounding land. If it collapses, there is a risk that it will break into pieces and flow into the sea.
“Eventually it’s going to wipe out all of West Antarctica,” said Richard Alley, a professor of geosciences at Penn State University.
Coastal cities around the world are at risk, but the threat is particularly acute in Asia, which includes some of the world’s fastest-growing urban areas, as the map below shows.
The costs of preventing higher storm surges and more frequent flooding will be significant. One U.S. Army Corps of Engineers proposal to protect parts of New York City would cost more than $52 billion, an amount that is out of reach for many people in the world.
“We’re going to protect the most valuable places that are defensible, but there are going to be places that aren’t,” said Benjamin Strauss, principal investigator at Climate Central, a nonprofit science organization that created the elevation model used in this article.
A Times analysis found that, city by city, densely populated areas tend to be near the coast, rather than in higher, safer areas.
Shanghai, one of the major cities under threat, already has more than 600,000 residents living below sea level. An additional 4.7 million people would be affected if average sea level rose by 2 feet.
Population at each altitude in Shanghai
Like many of the most vulnerable places, Shanghai is located on a soft wetland delta, a terrain that is naturally prone to subsidence, but humans often accelerate subsidence by building structures and draining the groundwater below. The city has also added and strengthened seawalls to absorb rainwater and replaced concrete in wetland parks.
Jochen Hinkel, director of the Global Climate Forum, an international research organization based in Germany, said that in places like Shanghai, the cost of protecting a city is relatively small compared to its value. “There’s so much capital concentrated in a small piece of land,” he says.
But not all places have the resources to protect themselves. Bangladesh’s capital Dhaka, whose population is expected to swell to more than 50 million by 2050, will rely heavily on borrowed funds to prepare for the worst.
Population of Dhaka at each altitude
Bangladesh, located in a low-lying delta, is experiencing more unstable monsoons and more powerful cyclones as the planet warms. Villages are already disappearing as the tides rise and change the shape of the region’s rivers. Tides of salt water are ravaging farmland and driving rural residents into the already crowded capital.
Limits of adaptation
Although a two-foot rise in sea levels would not affect as many people in the United States as it would in some parts of Asia, the cost of adaptation would be astronomical. And even in the world’s wealthiest countries, flood defenses are not bulletproof.
The pump and levee network failed during Hurricane Katrina in 2005, a catastrophe that killed 1,400 people and displaced more than 1 million people. Rebuilding New Orleans cost approximately $140 billion. Dozens of small communities along the Gulf Coast may not be so lucky.
new orleans
120,000 people Within 2 feet of high tide
protected area
by the embankment
miami metropolitan area
125,000
Other coastal cities are also preparing for sea level rise. It would cost $13.6 billion to protect parts of San Francisco’s waterfront. Inland California needs $2 billion to improve protection in Stockton. Nationally, building a giant barrier at the Port of New York City could cost $119 billion.
However, harm continues to accumulate on people and buildings. Miami’s population and real estate values have exploded in recent years, even though the city is notoriously difficult to defend.
A clearer answer to whether and when Thwaites will collapse could make a big difference in how well coastal regions can adapt. “The value of information is grotesquely higher than the amount of money we invest,” Dr. Alley says.
Under President Trump, the United States abandoned research that could better predict the effects of melting Antarctic ice. It also increases the use and burning of fossil fuels, increasing emissions of greenhouse gases that dangerously heat the planet. This could accelerate the collapse of glaciers.
Although the impact of decisions made today may not be felt immediately, “this is what we are signing for the future,” Dr. Strauss said.
methodology
The paper’s analysis includes cities with populations of 300,000 or more that are within 100 miles of the coast.
We used elevation data from Climate Central’s CoastalDEM 3.0 to calculate the average high tide for each location. The model reflects regional water levels more accurately than the global average. Data from the European Commission’s Global Human Settlement Strata (GHS-UCDB) was used for city boundaries, and WorldPop’s 2026 data was used for population estimates.
The sea level rise scenarios in this article focus only on impacts from Antarctica. As continents lose ice, they are expected to lose the gravitational pull of ocean water. Parts of the Northern Hemisphere, including the United States and much of Asia, would then be more affected by sea level rise than areas closer to Antarctica.
The maps and population totals have been adjusted to reflect this dynamic using data from Jerry Mitrovica, a professor of geophysics at Harvard University. These do not take into account similar dynamics due to ice loss in Greenland or other effects that may cause an uneven distribution of sea level rise.
