Sea Levels Could Rise by Several Metres Even If 1.5°C Warming Target Is Met, Scientists Warn

Even if the world succeeds in limiting global warming to the much-discussed target of 1.5°C, the planet could still face devastating sea-level rise of several metres over the coming centuries, scientists have warned.

Nearly 200 nations have pledged to aim for the 1.5°C threshold to avoid the worst impacts of climate change. However, new research shows that this target should not be considered “safe” for coastal communities.

The warning comes from a review of the latest scientific studies on how ice sheets are responding to current climate change—and how they have reacted to past periods of warming.

While limiting warming remains critical, the scientists stress that every additional fraction of a degree we can avoid will significantly reduce long-term risks.

At present, global temperatures are on track to rise by nearly 3°C by the end of the century compared to pre-industrial levels, based on current government policies and emission trends. This level of warming far exceeds the targets set in the 2015 Paris Agreement, where countries committed to keeping temperature increases “well below” 2°C and preferably under 1.5°C.

“Our key message is that limiting warming to 1.5C would be a major achievement – it should absolutely be our target – but in no sense will it slow or stop sea-level rise and melting ice sheets,” said lead author Prof Chris Stokes, a glaciologist at Durham University.

However, the researchers emphasise that even stabilising global warming at 1.5°C would not stop the continued melting of the Greenland and Antarctic ice sheets. These massive ice bodies respond to temperature changes over centuries, meaning their full reaction to today’s warming has yet to unfold.

The new study, published in Communications Earth and Environment, brings together three key lines of evidence.

First, geological records show that during previous warm periods—such as around 125,000 years ago—sea levels were several metres higher than today. Around 3 million years ago, when atmospheric carbon dioxide levels were similar to today’s, sea levels were an estimated 10 to 20 metres higher.

Second, modern observations show that ice melt is already accelerating, although the rate can vary from year to year.

“Pretty dramatic things [are] happening in both west Antarctica and Greenland,” said co-author Prof Jonathan Bamber, director of the Bristol Glaciology Centre.

While East Antarctica remains relatively stable for now, other regions, particularly West Antarctica and Greenland, are losing ice at an increasing pace.

“We’re starting to see some of those worst case scenarios play out almost in front of us,” added Prof Stokes.

Third, computer models simulating future climate scenarios predict substantial ice loss, especially if warming reaches critical “tipping points.”

“Very, very few of the models actually show sea-level rise slowing down [if warming stabilises at 1.5C], and they certainly don’t show sea-level rise stopping,” said Prof Stokes.

These thresholds, once crossed, could trigger irreversible and self-reinforcing ice melt, although scientists are still uncertain about exactly where those points lie.

“The strength of this study is that they use multiple lines of evidence to show that our climate is in a similar state to when several metres of ice was melted in the past,” said Prof Andy Shepherd, a glaciologist at Northumbria University, who was not involved in the new publication.

“This would have devastating impacts on coastal communities,” he added.

Currently, around 230 million people live within one metre of the present high tide line—making them highly vulnerable to rising seas.

Determining a truly “safe” level of warming is complex, as different regions and populations face varying degrees of risk. However, the researchers note that if sea levels begin rising by one centimetre per year or more—primarily due to melting ice and expanding oceans—it could overwhelm the adaptive capacity even of wealthy nations.

“If you get to that level, then it becomes extremely challenging for any kind of adaptation strategies, and you’re going to see massive land migration on scales that we’ve never witnessed [in modern civilisation],” argued Prof Bamber.

Despite the concerning outlook, the scientists emphasise that this is not a reason to give up.

On the contrary, it reinforces the urgency of cutting emissions and limiting warming as much as possible.

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