Researchers have forecasted a continuous rise in water level in the coming centuries due to global warming.

"Based on the current situation we have projected changes in the sea level 500 years into the future," says Aslak Grinsted, a researcher at the Centre for Ice and Climate, the Niels Bohr Institute at the University of Copenhagen. His group forms part of a team that has calculated the long-term outlook for rising sea levels in relations to the emission of greenhouse gases and pollution of the atmosphere.

Using climate models that were developed in collaboration with researchers from England and China, the group made calculations for four scenarios: pessimistic, optimistic and two realistic.

According to the researchers, in the optimistic scenario, sea level will rise by 60 cm by the year 2100 and 1.8 meters by the year 2500. However, for the optimistic scenario to happen, there must be extremely dramatic climate change goals, major technological advances and strong international cooperation to stop emitting greenhouses gases and polluting the atmosphere.

In the pessimistic scenario, sea levels will rise 1.1 meters by the year 2100 and will have risen 5.5 meters by the year 2500.

For the two more realistic scenarios, the results show that there will be a sea level rise of about 75 cm by the year 2100 and that by the year 2500 the sea will have risen by 2 meters. These calculations were based on the presumptions that emissions and pollution are stabilized.

"In the 20th century sea has risen by an average of 2mm per year, but it is accelerating and over the last decades the rise in sea level has gone approximately 70% faster," Grinsted said.

"Even if we stabilize the concentrations in the atmosphere and stop emitting greenhouse gases into the atmosphere, we can see that the rise in sea level will continue to accelerate for several centuries because of the sea and ice caps long reaction time. So it would be 2-400 years before we returned to the 20th century level of a 2 mm rise per year," he added.

The researcher explained that even though long-term calculations are subject to uncertainties, the sea will continue to rise in the coming centuries and it will most likely rise by 75 cm by the year 2100 and by the year 2500 the sea will have risen by 2 meters.