Scientists have embarked on an expedition to Antarctica in the first few weeks of the year to study the Thwaites Glacier, which is melting at an alarming rate. If it completely breaks, it could raise global sea levels by up to 2 feet over several decades, affecting tens of millions of people around the world, according to a New York Times analysis.
The map below shows some of today’s most at-risk coastal cities and densely populated low-lying areas that could be threatened if glaciers collapse.
1.7 million
This is just the minimal impact the collapse of Thwaites could have on the world’s coastlines. As glaciers break, global warming will melt Greenland’s ice and increase ocean volume, causing sea levels to rise even further. And Thwaites acts as a plug for many Antarctic glaciers on the surrounding land. If it collapses, it may break apart and flow into the sea.
“It will eventually sweep through all of West Antarctica,” said Richard Alley, a professor of geosciences at Penn State University.
Beach cities around the world are at risk, but as you can see in the map below, the threat is particularly acute in Asia, which contains some of the fastest-growing urban areas in the world.
The cost of preventing higher storm surges and more frequent flooding would be enormous. One proposal from the U.S. Army Corps of Engineers to protect parts of New York City would cost more than $52 billion, a price that most of the world cannot afford.
“We will defend the highest-value places we can defend, but there will be other places we cannot defend,” said Benjamin Strauss, senior scientist at Climate Central, a nonprofit scientific organization that produced the altitude model used in the article.
City by city, the Times’ analysis found that densely populated areas tended 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. A 2-foot rise in average sea level would affect an additional 4.7 million people.
Population by altitude in Shanghai
Like many of the most vulnerable places, Shanghai is located in a soft marsh triangle that is naturally prone to sinking, but humans often speed up the process by building structures and draining groundwater. The city has also been adding and strengthening seawalls and replacing concrete with wetland parks to absorb stormwater.
Jochen Hinkel, director of the Global Climate Forum, an international research institute based in Germany, said that in places like Shanghai, the cost of defending a city is relatively small compared to its value. “There is too much capital concentrated in small tracts of land,” he said.
But not all places have the resources to protect themselves. Dhaka, the capital of Bangladesh, is expected to have a population of more than 50 million by 2050 and will rely extensively on borrowings to prepare for the worst.
Dhaka’s population at different altitudes
Bangladesh, a low-lying delta country, is experiencing more unstable monsoons and stronger cyclones as the planet warms. The village has already been erased as the tides rise and the area’s rivers change shape. Sea tides have devastated farmland and driven rural residents into the already crowded capital.
limits to adaptation
In the United States, a two-foot rise in sea levels would not affect as many people as in parts of Asia, but the cost of adaptation would be astronomical. And even in the world’s wealthiest countries, flood defenses are far from perfect.
In 2005, Hurricane Katrina caused a network of pumps and levees to fail, resulting in a disaster that killed 1,400 people and left more than 1 million homeless. New Orleans’ recovery cost is approximately $140 billion. Dozens of small communities along the Gulf Coast may not be so lucky.
120,000 people Within 2 feet of high tide
protected area
to the embankment
125,000
Other coastal cities are bracing for rising sea levels. Protecting part of San Francisco’s waterfront will cost $13.6 billion. $2 billion would be needed to improve protection in Stockton, farther inland in California. Nationwide, building a massive wall at New York City’s harbor could cost $119 billion.
However, damage to people and buildings continues to accumulate. Despite being a very difficult city to protect, Miami has seen its population and real estate values explode in recent years.
A clear answer to whether and when Thwaites may collapse could make a big difference to how well coastal areas can adapt. “The value of the information is grotesquely higher than what we invested in it,” Dr. Alley said.
Under President Trump, the United States abandoned research that could have better predicted the impact of melting ice in Antarctica. It also promotes the use and burning of fossil fuels, increasing greenhouse gas emissions that are heating the planet dangerously. This could accelerate the rate of glacier collapse.
The consequences of decisions made today may not be felt immediately, but “this is why we commit to the future,” Dr. Strauss said.
methodology
The Times’ analysis included cities with more than 300,000 residents and 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. This model reflects local water levels more accurately than the global average. For city boundaries, we used the European Commission’s Global Human Settlement Layer (GHS-UCDB) data, and for population estimates, we used Worldpop’s 2026 data.
The sea level rise scenarios in this article focus only on the impacts on Antarctica. As the continent loses its ice, it is expected to lose its gravitational pull against ocean water. If that happens, parts of the Northern Hemisphere, including the United States and most of Asia, will experience a higher-than-average impact from sea level rise than areas closer to Antarctica.
The maps and total population counts were adjusted to reflect these dynamics using data from Harvard geophysics professor Jerry Mitrovica. They do not account for similar dynamics due to ice loss in Greenland or other impacts that could cause uneven distribution of sea level rise.
