Asked by: Richard Wren, Lancaster
In the last couple of decades, the sea level has risen by about 3.2mm per year – double the average rate last century.
A further 2m rise by 2100 is now within the range predicted by many experts. This would put a lot of Cambridgeshire permanently underwater, as well as much of Hull, Great Yarmouth and Glastonbury. But the sea level isn’t constant around the globe. Ocean currents and the shape of the land masses mean the waters of the South Pacific and China Sea are already 30cm higher than the average. Falling salinity due to increased rainfall lowers the density of seawater, so the sea level in these areas rises faster too.
Forty per cent of the world’s population lives within 100km of the coast, while 250 million people live less than 5m above sea level. Hurricanes and storm surges can magnify even small sea level rises dramatically. Flood levels that would previously be expected just once a century will occur on average once a decade. The US has 20,000km (12,400 miles) of coastline and protecting it will cost $15bn. Bangladesh fares much worse, in 2016, more than 3.7 million people were affected by floods theres (pictured). It will need 8,000km of dykes over 10m tall to protect it, and without them will lose more than 16 per cent of its total land area, including the Sundarbans mangrove forest – one of the last homes of the Bengal tiger.