3C of warming will leave world cities below sea level

How Shanghai would look with a rise of just 2C: the UN warned this week of a potential 3C scenario. Photograph: Nickolay Lamm/Courtesy Climate Central

Hundreds of millions of urban dwellers around the world face their cities being inundated by rising seawaters if latest UN warnings that the world is on course for 3C of global warming come true, according to a Guardian data analysis.

Data from the Climate Central group of scientists analysed by Guardian journalists shows that 3C of global warming would ultimately lock in irreversible sea-level rises of perhaps two metres. Cities from Shanghai to Alexandria, and Rio to Osaka are among the worst affected. Miami would be inundated – as would the entire bottom third of the US state of Florida.

South Beach, Miami, would be mostly underwater. Photograph: Nickolay Lamm/Courtesy Climate Central

In Miami – which would be almost entirely below sea level even at 2C warming – the sense of urgency is evident at city hall, where commissioners are asking voters to approve a “Miami Forever” bond in the November ballot that includes $192m for upgrading pump stations, expanding drainage systems, elevating roads and building dykes.

A 3C rise would lead to longer droughts, fiercer hurricanes and lock in sea-level rises that would redraw many coastlines. Depending on the speed at which icecaps and glaciers melt, this could take decades or more than a century.

At least 275 million city dwellers live in vulnerable areas, the majority of them in Asian coastal megacities and industrial hubs such as Shanghai, Shenzhen, Bangkok and Tokyo.

Japan’s second biggest city, Osaka, is projected to lose its business and entertainments districts of Umeda and Namba unless global emissions are forced down or flood defences are built up. Officials are reluctantly accepting they must now put more effort into the latter.

Read the complete article on The Guardian newspaper site.

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