Rising sea levels driven by global warming are on track to dramatically boost the frequency of coastal flooding worldwide by the middle of the century, especially in tropical regions, researchers say.
A 10cm to 20cm jump in the global ocean watermark by 2050 – a conservative forecast – would double flood risk in high-latitude regions, they reported in the journal Scientific Reports on Thursday.
Major cities along the North American seaboard, such as Vancouver, Seattle, San Francisco and Los Angeles, along with the European Atlantic coast, would be highly exposed.
But it would take only half as big a jump in ocean levels to double the number of serious flooding incidents in the Tropics, including along highly populated river deltas in Asia and Africa. Even at the low end of this sea rise spectrum, Mumbai, Kochi and Abidjan, and many other cities would be significantly affected.
Coastal flooding is caused by severe storms, and is made worse when large waves, storm surge and high tides converge.
Hurricane Sandy in the United States in 2012, which caused tens of billions of dollars in damage, and Typhoon Haiyan in the Philippines in 2013, which left more than 7,000 dead or missing, both saw devastating flooding. Rising seas – caused by the expansion of warming ocean water and runoff from melting ice sheets and glaciers – are also a contributing factor.
But up to now, global estimates of future coastal flooding have not adequately taken into account the role of waves.
Sea levels are currently rising by 3mm to 4mm a year, but the pace has picked up by about 30 per cent over the last decade. It could accelerate even more as continent-sized ice blocks near the poles continue to shed mass, especially in Antarctica.
The US National Oceanic and Atmospheric Administration [Link: ] predicts that global average sea level will rise by as much as 2.5m by 2100.
Global average temperatures have increased by 1 degree Celsius since the mid-19th century, with most of that happening in the last 70 years.
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Source: Agence France-Presse, 18 May 2017