300 million face annual coastline flooding by 2050

Coastal areas currently home to 300 million people will be vulnerable by 2050 to flooding made worse by climate change, no matter how aggressively humanity curbs carbon emissions, scientists said Tuesday.

By mid-century and beyond, however, choices made today will determine whether Earth's coastlines remain recognisable to future generations, they reported in the journal Nature Communications. Destructive storm surges fuelled by increasingly powerful cyclones and rising seas will hit Asia hardest, according to the study. More than two-thirds of the populations at risk are in China, Bangladesh, India, Vietnam, Indonesia and Thailand. Using a form of artificial intelligence known as neural networks, the new research corrects ground elevation data that has up to now vastly underestimated the extent to which coastal zones are subject to flooding during high tide or major storms. "Sea-level projections have not changed," co-author Ben Strauss, chief scientist and CEO of Climate Central, a US-based non-profit research group, told AFP.

With the global population set to increase two billion by 2050 and another billion by 2100 - mostly in coastal megacities - even greater numbers of people will be forced to adapt or move out of harm's way. Already today, there are more than 100 million people living below high tide levels, the study found. Some are protected by dikes and levees, most are not.

"Climate change has the potential to reshape cities, economies, coastlines and entire global regions within our lifetime," said lead author and Climate Central scientist Scott Kulp. "As the tideline rises higher than the ground people call home, nations will increasingly confront questions about whether, how much and how long coastal defences can protect them." Several factors conspire to threaten populations living within a few metres of sea level.

One is the expansion of water as it warms and, more recently, ice sheets atop Greenland and Antarctica that have shed more than 430 billion tonnes per year over the last decade. Since 2006, the waterline has gone up nearly four millimetres a year, a pace that could increase 100-fold going into the 22nd century if carbon emissions continue unabated, the UN Intergovernmental Panel for Climate Change (IPCC) warned in a major report last month.