It is already taking shape as the 21st century urban nightmare: a big storm hits a city like Shanghai, Mumbai, Miami or New York, knocking out power supply and waste treatment plants, washing out entire neighbourhoods and marooning the survivors in a toxic and foul-smelling swamp.
Now the world’s leading scientists are suggesting that those same cities in harm’s way could help drive solutions to climate change.
A draft report from the Intergovernmental Panel on Climate Change (IPCC), obtained by the Guardian, says smart choices in urban planning and investment in public transport could help significantly lower greenhouse gas emissions, especially in developing countries.
The draft is due for release in Berlin on Sunday, the third and final instalment of the IPCC’s authoritative report on climate change.
“The next two decades present a window of opportunity for urban mitigation as most of the world’s urban areas and their infrastructure have yet to be constructed,” the draft said.
Around 1 billion people live in cities and coastal areas at risk of sea-level rise and coastal flooding – and those figures are expected to rise in the coming decades.
Most of the high-risk areas are in Asia, but the US east coast, where the rate of sea level rise is three or four times faster than the global average, is also a “hotspot”, with cities, beaches and wetlands exposed to flooding.