Accelerating sea level rise driven by warming oceans and melting ice threatens coastal cities worldwide, placing up to a billion people at risk before the end of the century.

In what must rate as one of the worst forseeable disasters ever to confront humanity, the remorseless rise in the oceans will menace the homes and livelihoods of a billion people before the end of the century.

From 1900 to 2018, global sea levels rose by about 20cm (a long-term average of 1.7mm/yr), but measurements since 1993 (when global satellite data first became available) show the rate of global mean sea-level rise then doubled to 3.3 mm/yr - and has since accelerated to 4.4 mm/yr.

However  world sea levels do not rise uniformly like water in a bathtub. In a recent study of worst case scenarios, scientists warned that some coastal communities may face total rises as high as nine or 10 metres by 2100.

“By 2100 almost 45 per cent of the global coastline would experience sea level increases above the global mean of 4.2 m, with up to 9–10 m for the East China Sea, Japan and North European coastal areas," they said.

“Up to 86 per cent of coastal locations would face sea level rises above 3 m by 2100, compared to 33 per cent currently.”

Sea level rise was listed in the Global Risks Report 2025 as one of the critical changes to the Earth System that together constitute the third greatest threat to humanity in the coming decade. The United Nations (UN) has rated it "a global crisis" that is already........

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