Top climate scientists warned Tuesday that sea levels could rise twice as much as previously projected when they presented the latest research on global warming.

A 2007 report by the Intergovernmental Panel on Climate Change predicted a sea level rise of seven to 23 inches (18 to 59 centimetres) by the end of the century.

But scientists meeting in Copenhagen dismissed those estimates as too conservative, saying new data suggests that sea level rise could exceed 39 inches (one metre) and is unlikely to be less than 20 inches (50 centimetres).

"This means that if the emissions of greenhouse gases is not reduced quickly and substantially even the best-case scenario will hit low-lying coastal areas housing one-tenth of humans on the planet hard," organizers said in a statement at the three-day congress hosted by the University of Copenhagen.

The melting of polar ice sheets and glaciers are two big factors that will affect sea levels, they added.

"Unless we undertake urgent and significant mitigation actions, the climate could cross a threshold during the 21st century committing the world to a sea level rise of metres," said John Church of the Centre for Australian Weather and Climate Research.

The conclusions of the conference will be presented to politicians meeting in Copenhagen in December to discuss a new global agreement on greenhouse gas emissions to replace the Kyoto Protocol, which expires in 2012.

Some 1,600 abstracts from nearly 80 countries have been submitted to the conference.