PARIS: Even if humanity beats the odds and caps global warming at 1.5 degrees Celsius above preindustrial levels, seas will rise for centuries to come and swamp cities currently home to half-a-billion people, researchers warned on Tuesday.

In a world that heats up another half-degree above that benchmark, an additional 200 million of today’s urban dwellers would regularly find themselves knee-deep in sea water and more vulnerable to devastating storm surges, they reported in Environmental Research Letters.

Worst hit in any scenario will be Asia, which accounts for nine of the ten mega-cities at highest risk.

Land home to more than half the populations of Bangladesh and Vietnam fall below the long-term high tide line, even in a 2C world.

Built-up areas in China, India and Indonesia would also face devastation.

Cities currently home to half-a-billion people will be swamped by rising sea levels, warn researchers

Most projections for sea level rise and the threat it poses to shoreline cities run to the end of the century and range from half-a-metre to less than twice that, depending how quickly carbon pollution is reduced.

But oceans will continue to swell for hundreds of years beyond 2100 — fed by melting ice sheets, heat trapped in the ocean and the dynamics of warming water — no matter how aggressively greenhouse gas emissions are drawn down, the findings show.

“Roughly five per cent of the world’s population today live on land below where the high tide level is expected to rise based on carbon dioxide that human activity has already added to the atmosphere,” lead author Ben Strauss, CEO and chief scientist of Climate Central, said.

Today’s concentration of CO2 — which lingers for hundreds of years — is 50pc higher than in 1800, and Earth’s average surface temperature has already risen 1.1C.

Published in Dawn, October 13th, 2021