Professor David Vaughan of the British Antarctic Survey has warned that a 50cm rise in sea levels would dramatically increase the risk of flooding in London and the rest of the UK.
The Thames Barrier is designed to protect London against all but a one-in-a-thousand year storm surge, but if such a sea rise occurred the level of protection would fall to one-in-a-hundred years.
Such a rise would be at the more extreme end of current IPCC predictions, but some scientists say a 1m rise by 2100 is possible.
Professor Vaughan also says that the IPCC predictions did not fully take into account loss of ice from Greenland and Antartica - something he is working to remedy.
How do scientists survive -30 degrees temperatures at Barneo, the temporary camp set up on floating ice near the North Pole?
Arctic glaciers are melting faster than expected fuelling a rise in sea levels, which experts believe could cost the UK billions of pounds.
As new figures show the record cold weather is persisting into April, the Met Office says it will investigate if Arctic melting is to blame.