Some of the world's biggest cities face a flood-hit future as climate change induced sea-level rise compounds urban development problems, says a new report published by Christian Aid this week.
As nations meet this week in South Korea for the Intergovernmental Panel on Climate Change's report on limiting global warming to 1.5 degrees, Christian Aid reveals that well-known coastal cities are set to become extremely vulnerable to storm surges and flooding.
Sea level rise is expected to exceed 40cm if global warming is not limited to 1.5 degrees Celsius. With the world's urban population expected to grow to 59% by 2030, city dwellers will become increasingly under threat.
Report author Dr Kat Kramer, Christian Aid's Global Climate Lead, said: "Some of the world's most famous cities are sinking under the waves as climate change drives up sea levels. We're starting to see what happens when climate change acts as a threat-multiplier, compounding poor development decisions.
"We're already at around one degree of warming and we are getting a picture of what happens if we exceed 1.5 degrees. Worryingly the world is currently on track for more than three degrees of warming, which would have disastrous consequences for the millions of people living in these coastal cities. It's vital that governments heed the findings of the IPCC and agree to increase their Paris Agreement pledges.
"These global metropolises may look strong and stable but it is a mirage. As sea levels rise, they are increasingly under threat and under water."
The cities featured in the Sinking Cities, Rising Seas report include:
As Indonesia suffers from the devastating impact of a tsunami it's vulnerability as the world's fastest sinking city is exposed for the world to see. Now 40% of the city lies below current sea levels and it is reportedly subsiding at a rate of 25cm a year. Natural sea defences like mangroves have been removed making it vulnerable to storm surges while ground water extraction to supply the city's residents has contributed to the problem. A further rise in sea levels from climate change will make it even more in danger to further coastal flooding.
The home of America's oil and gas industry is literally contributing to its own downfall as extraction of the minerals leads to subsidence. Downtown Houston already stands only 15m above sea-level and 12,000 km2 of the greater Houston-Galveston area has already experienced a lowering of the land surface by as much as 3m. Parts of it continue to sink at two inches a year and in 1983 the up-market residential peninsular of Brownswood was rendered uninhabitable by a hurricane. Ironically Brownswood was home to a number of oil and gas executives.
London is sinking partly due to the melting of the UK's glaciers, which weighed Scotland down during the last ice age and meant the south was lifted up like a see-saw. With the glaciers gone, Scotland is rebounding and London is sinking into the rising seas. The Thames Barrier designed to protect the river-lined capital from flooding was opened in 1984 and predicted to be used two to three times a year. It is already being used six to seven times a year and with another 40-50cm of sea level rise, will Parliament keep its supremacy, or will the waves rule Britannia?
Shanghai is too heavy for the ground it's built on. The sheer weight of its infrastructure, combined with the extraction of groundwater and rising seas, means it is sinking into the sediments below. Subsidence cost the city two billion dollars between 2001-10, a figure likely to grow much bigger in coming years.
Nigeria's capital could see 740,000 residents losing their homes with a sea level rise of just 20cm. Such is the concern that the government has sought to fine or imprison people who drill boreholes without authorisation. However this has proved controversial as access to water is limited and 70% of the city's population live in informal settlements.
The Philippines is no stranger to extreme weather, with the country still rebuilding following September's Typhoon Mangkhut, the strongest storm to hit the island nation since Typhoon Haiyan killed more than 6,300. With Manila only having an average elevation of 5m and sinking at 10cm per year, the city may be living on borrowed time. This opens up the risk of high tides penetrating deeper inland causing salination of previously fertile soils.
Bangladesh is another country on the front line of climate change where sea level already appears to be causing migration. People have been displaced in the lowest lying river deltas which has seen an additional 1.5 million people join Dhaka's five million slum dwellers. Urbanised areas in the city are a mere 6-8cm above sea level and sea level rise appears to be happening at a rate ten times greater than the global average in the Bay of Bengal, southwest of the city.
Three years ago, the Thai government published a report which concluded that Bangkok could be underwater in the next 15 years. At only 1.5m above sea level, the city's sinking feeling has been made worse by its skyscrapers that reach for the sky. It has 700 buildings with 20 floors or more and 4,000 buildings with 8-20 floors, the sheer weight of which are pressing it downwards towards into its underlying sediments.
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