The maps, created by technology firm Mapflow using its own aerial survey data, reveal an unrecognisable coastline of Dublin Bay a century from now, based on an 11 metre increase in sea level.

The map is not a prediction, but is based on a worst-case scenario for climate change similar to that spelled out earlier this year by environmental guru Professor James Lovelock.

Sea levels are currently 120 metres higher than their low point during the last ice age around 18,000 years ago, when more of the earth's water was frozen in glaciers and ice sheets. Although they have been relatively stable for the last 2,500 years, sea levels are now rising because of further melting of ice sheets in Greenland and Antarctica. Some climate scientists argue that the melting of polar ice has already passed a tipping point where the effects are irreversible and accelerating, resulting in catastrophic damage.

Scientists including John Sweeney of NUI Maynooth, a member of the Intergovernmental Panel on Climate Change, have already urged a ban on further development near vulnerable coastlines, a crash programme of flood defences and a plan to "climate-proof" future development, especially of key infrastructure projects.

Running on the south side through St Stephen's Green roughly down Leeson Street, the new coastline would create beachfront property in Ranelagh, with the N11 becoming the new coast road.

Most of Drumcondra and all of Marino would be under water. Howth Head becomes the Isle of Howth, accessible only by boat.

Dublin wouldn't be the only Irish city affected, however.

"Cork city would be gone, " said Jonathan Guard of Mapflow, which provides mapping and location services to insurance and telecommunications firms.

"It would be far worse than New Orleans after Hurricane Katrina."

Less extreme but more specific predictions of how climate change is increasing flood risk of particular areas are a hot topic in the insurance industry worldwide, which has faced mounting claims as a result of natural disasters including floods.

According to the Irish Insurance Federation, the cost to insurers of major floods in Ireland in 2000, 2002 and 2004 exceeded 176m.

Insurer Norwich Union recently compiled a digital map of the entire UK that allows it to assess the flood risk to a particular property. Other insurers are following suit to more accurately assess risk.

The Office of Public Works, the lead government agency dealing with flood defences, is building a digital flood hazard map of Ireland. The first phase, which will be accessible through the agency's website and will note historical flood events, is expected to be completed by the middle of this year.

Dublin City Council and Fingal County Council commissioned a 1.2m study by consultants Posford Haskoning, part-funded by the OPW, to determine what flooddefence measures around Dublin would be required to prevent a repeat of the floods that affected the south inner city village of Ringsend and the northside district of Drumcondra in 2002.

Among the possible options for flood defence mentioned in the report, which has not been released, were a metre-high glass wall atop the banks of the Liffey near the IFSC and lengthening the promenade at Sandymount Strand. Another option was an inflatable PVC "mobile dam" that would be a tube in 250-metre segments that could be rolled out along the length of the Liffey and inflated with water.

But the measures proposed in the report were based on protecting against a storm surge of 3.25 metres above high tide at Dublin Port. As our maps show, the worstcase scenario would require a far more dramatic rethink of whether Ireland's coastal cities can survive at all.