Waterworld: Hong Kong and Shanghai will be under water if temperatures rise by 4 degrees Celsius

Large swathes of Shanghai, Mumbai, New York and other cities will slip under the waves even if an upcoming climate summit limits global warming to two degrees Celsius, scientists reported.

A 2 degrees rise in earth’s temperature would submerge land currently occupied by 280 million people, while an increase of 4 degrees - humanity’s current trajectory - would cover areas lived on by more than 600 million, the study said on Sunday. China would be the nation worst hit by a 4 degrees scenario, and much of Hong Kong would be immersed.

“Two degrees Celsius warming will pose a long-term, existential danger to many great coastal cities and regions,” said lead author Ben Strauss, vice-president for sea level and climate impacts at Climate Central, a US-based research group.

Sea level rises corresponding to these 2 degrees or 4 degrees scenarios could unfold in 200 years, but would more likely happen over many centuries, perhaps as long as 2,000 years, according to the research, published by Climate Central.

Today, some 145 million people live in Chinese cities and coastal areas that would eventually become ocean were temperatures to climb 4 degrees, the study found.