Even at 1.5°C warming, melting ice sheets could flood coasts for centuries, scientists warn

When world leaders rallied behind the 1.5°C global warming target a decade ago, the goal was framed as a guardrail—hold the planet’s temperature increase to that limit and avoid the worst consequences of climate change. But a new study published this week in Communications Earth and Environment suggests that even meeting that target may not be enough to stop devastating sea-level rise, the Washington Post reported.

Drawing on more than 150 scientific papers, researchers found that Earth’s two massive ice sheets—Greenland and Antarctica—are already melting at alarming rates and will likely continue to do so even if warming holds at the current level of 1.2°C. Their conclusion: the threshold to prevent long-term catastrophic sea rise may actually be closer to just 1°C of warming.

A race against rising seas

Greenland and Antarctica together contain enough ice to raise global sea levels by more than 210 feet. Today, they are losing around 370 billion metric tons of ice each year—a rate that has quadrupled since the 1990s. That ice loss is projected to continue for centuries, with devastating consequences for coastal communities around the globe.

“There was a kind of misunderstanding that 1.5 was going to solve all our problems,” said Chris Stokes, a glaciologist at Durham University and co-author of the study. “It’s an existential threat. Some of these entire states are going to be underwater in a few centuries.”

Lessons from the past: When the planet was this warm before

To understand what the future might hold, scientists looked back 125,000 years to the Last Interglacial period—the last time Earth was as warm as it is now. Evidence from ancient coral reefs, ice cores, ocean sediments, and even DNA from deep-sea creatures shows that polar ice sheets collapsed quickly during that time, raising sea levels by over 20 feet.

What’s more alarming is how fast it happened. Sea levels rose in bursts, suggesting that once certain temperature thresholds were crossed, ice sheets could suddenly destabilize and release massive amounts of water into the ocean.

Modern modelling confirms ancient warning signs

Using this ancient data, researchers tested Earth system models to see if their simulations aligned with the historical evidence—and they did. That gave them confidence in future projections, which showed that even if warming is limited to 1.5°C, irreversible ice loss could raise seas by several meters over the next few centuries.

“Every fraction of a degree matters,” said Andrea Dutton, a geologist at the University of Wisconsin and study co-author. “We can’t just adapt to this type of sea-level rise. We can’t just engineer our way out of this.”

An uncertain future for millions

Approximately 230 million people currently live within one meter (about three feet) of sea level. As seas rise, entire coastal cities and nations could be swallowed. Low-lying island nations near the equator, such as Micronesia and some Caribbean islands, face an outsized risk due to gravitational redistribution of meltwater.

With sea levels locked into a slow but unstoppable rise under current conditions, the study makes one thing clear: hitting climate targets alone may not be enough. To protect the most vulnerable, global efforts may need to go beyond mitigation—toward urgent adaptation, relocation, and bold emissions reductions that push warming below today’s already dangerous levels.