is sea-level rise worse than we thought?

Just two years ago international climate scientists agreed on a forecast that sea levels would rise by around 50 centimetres by the end of this century. Now scientists meeting ahead of global climate talks later this year believe that may be too conservative an estimate so says the ABC in Australia (Broadcast: 11/03/2009, reporter: Shane McLeod ). Is this true? Whose estimate of increasing ocean levels can we believe?