Even if climate targets are met, rising oceans threaten to displace millions and overwhelm coastal defences within decades, landmark study finds.
A new scientific analysis has delivered a stark warning: even if the world manages to cap global warming at 1.5°C – the key threshold set by the Paris Agreement – rising sea levels will still trigger unprecedented levels of inland migration and long-term coastal devastation.
The study, published in Communications Earth and Environment, synthesises decades of climate data, modern satellite observations, and geological records going back 3 million years.
Its conclusion is clear: ice loss from Greenland and Antarctica, which has quadrupled since the 1990s, is now the principal driver of rising seas, and that rise is happening faster than nations can build defences.
Despite recent diplomatic momentum, including renewed pledges at last year’s COP summit, the world is currently on track for 2.5°C to 2.9°C of warming. At those temperatures, the study warns, critical tipping points for ice sheet collapse would almost certainly be breached, leading to eventual sea level rises of up to 12 metres.
That would inundate major cities, erase low-lying island nations, and displace hundreds of millions.
Currently, about 230 million people live within one metre of sea level. A billion reside within 10 metres. By 2050, even a modest 20cm rise could generate annual damages exceeding $1 trillion across 136 major coastal cities.
In the UK, one metre of rise would flood the Fens and Humberside. For lower-income nations, like Bangladesh or Belize, where resources to build large-scale sea defences are limited, the consequences would be far more severe.
Carlos Fuller, Belize’s longtime climate negotiator, said the report reinforces the urgency to stick to the Paris Agreement.
Even with massive emissions reductions and technological breakthroughs to remove CO2, the ice sheets will take hundreds, possibly thousands of years to recover. Any land claimed by the ocean in the meantime will likely remain submerged until the Earth enters its next ice age.
The study’s authors stressed that all is not lost. Every fraction of a degree of warming we avoid buys time, said Bamber.
With sea level rise now viewed as the most enduring legacy of the climate crisis, scientists are urging governments not just to cut emissions but also to begin planning for large-scale migration, redesigned infrastructure, and the transformation of coastal economies.
