OSLO (Reuters) - Global warming is happening faster than expected and at worst could raise sea levels by up to 2 meters (6-1/2 ft) by 2100, a group of scientists said on Tuesday in a warning to next month's U.N. climate summit in Copenhagen.

In what they called a "Copenhagen Diagnosis," updating findings in a broader 2007 U.N. climate report, 26 experts urged action to cap rising world greenhouse gas emissions by 2015 or 2020 to avoid the worst impacts of climate change.


"Climate change is accelerating beyond expectations," a joint statement said, pointing to factors including a retreat of Arctic sea ice in summer and melting of ice sheets on Greenland and Antarctica.

"Accounting for ice-sheets and glaciers, global sea-level rise may exceed 1 meter by 2100, with a rise of up to 2 meters considered an upper limit," it said. Ocean levels would keep on rising after 2100 and "several meters of sea level rise must be expected over the next few centuries."