The stark warning has been issued by An Taisce, Ireland's equivalent of English Heritage, which claims the Irish Sea will eventually reclaim the land on which Dublin's 18th-century streets and squares are built.
Heritage officer Ian Lumley said the threat to Dublin was 'mounting and overwhelming'.
'Unlike the Medieval centre running along the ridge between Christ Church and High Street, much of the Georgian city is built on land reclaimed from the sea, as tidal waters ran close to Merrion Square until the 18th century,' said Lumley.
He accepted that scientists remain divided over the exact timescale for sea-level rises, but said the threat to Dublin should put Ireland at the forefront for international action on climate change.
Saving Georgian Dublin from flood will demand 'hundreds of millions of euros' to implement, according to Dublin City Council.
The council has confirmed a review of drainage systems in Dublin and the surrounding counties is under way to help prevent the kind of severe flooding already seen in the city.