With the sea level rising and storms strengthening thanks to climate change, will much of the world's most valuable real estate find itself underwater?

Justin Rowlatt visits London's main line of defence against the sea - the Thames Barrier - a hugely expensive piece of engineering that will need to be replaced by an even larger barrier later this century, according to its operator Steve East, and coastal risk manager Cantor Mocke.

The oceans will eventually rise by two metres at the very least, says climatologist Ben Strauss of US think tank Climate Central, putting many of the world's great cities at severe risk of inundation. The giant global real estate investment firm Heitman has been looking at which properties in its portfolio are most at risk. Company strategist Brian Klinksiek tells of his fear that the market has yet to price in the cost of the giant storms of the future.

The biggest city in the world vulnerable to the rising waters is Shanghai in China, and flood risk researcher Qian Ke of the Delft University of Technology explains the work she is already doing with the Shanghai city authorities to prepare for the coming storm.

Producer: Laurence Knight

(Picture: People are taken ashore in a boat after being rescued from their homes in New Orleans after Hurricane Katrina in 2005; Credit: Mario Tama/Getty Images)