Meanwhile, in West Antarctica, scientists plumbing the 74,000 sq mile Thwaites Glacier – about the size of Florida – found new evidence of ice melting faster than ever previously imagined. Not for nothing is the glacier called the “doomsday glacier”. Further east, iceberg A68, about five times the area of Hong Kong and made up of a trillion tonnes of ice, is after a couple of years of dithering at last moving out into the South Atlantic Ocean.

It seems hard to get alarmed when scientists say Antarctic ice melt is raising sea levels by 3mm a year, but drip by drip we should be afraid. As evidence accumulates of speeding ice melt, they are talking now of oceans that will be between 1 to 2 metres higher by the end of the century.

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Cities in Asia are among those at greatest risk. Around Shanghai, an area from Lianyungang in the north to Hangzhou in the south (about 570km), and 250km inland embracing Wuxi, Suzhou, Changzhou and Nanjing, is under threat. Around Hong Kong, an area west from Shenzhen and Dongguan to Jiangmen and up to Guangzhou could be submerged daily at high tide by 2050.

In northern Vietnam, flooding will extend 100km inland to Hanoi, while the entire area 200km south from Ho Chi Minh will be under water.

Climate Central predicts that 93 million people in China – 26 million around Shanghai – face displacement, along with 42 million in Bangladesh, 36 million in India, 31 million in Vietnam, 23 million in Indonesia and 12 million in Thailand.

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In the absence of good local estimates, modellers have estimated that Hong Kong’s losses from Typhoon Mangkhut in 2018 were around US$18 billion, with even larger losses on the mainland.

Perhaps they could compare notes with the Netherlands, which even Roman author Pliny the Elder described 2000 years ago as “a pitiful land flooded twice a day”. After tragedies over the centuries, the country has developed the “poldermodel” – a consensus-oriented decision-making process that includes various stakeholders in society – to protect the community with an efficiency and effectiveness that is the envy of the world.

“The Dutch … tend to be in awe of nations that are good at rescuing people from rooftops or flying in soldiers to clear wreckage,” Simon Kuper wrote in the Financial Times recently. “Instead, the Netherlands does prevention.”

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For decades the government has spent around €1 billion (US$1.09 billion) a year on what it calls “dry feet insurance”. The showpiece of this policy is the €450 million Maeslantkering barrier that protects Rotterdam at the mouth of the Rhine as it flows into the North Sea. As Kuper notes, “the ‘door’ needs to close just once in its lifetime to earn its money” because any flood that shuts Rotterdam could cause damage worth hundreds of billions.

In contrast to the Dutch focus prevention, Kuper observes that “the US devotes awesome energy to response – rebuilding after disasters”. However, the rebuilt structures are vulnerable to future storms. “The National Flood Insurance Programme has repeatedly bailed out more than 30,000 ‘severe repetitive loss properties’, each flooded on average five times,” Kuper says.

But even here, the severity of the future challenge has Kuper worried. After examining how much the world might learn from the Dutch approach to flood protection, his conclusion was stark: “I began my research thinking that the Dutch could save the world, but finished by doubting whether they could even save the Netherlands.”

David Dodwell researches and writes about global, regional and Hong Kong challenges from a Hong Kong point of view