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By Andy Soloman
MCMURDO STATION, Antarctica (Reuters) - Global warming could raise sea levels by as much as six meters (20 feet) in the next generation and the earth could be heading for a mini ice-age, Antarctic scientists said Wednesday.
Global warming due to increasing discharges into the upper atmosphere of greenhouse gases such as carbon dioxide could soon begin to threaten the massive western Antarctic ice shelf, they warned.
If that melted, massive volumes of cold water would enter the world's oceans and disrupt global sea currents known as the global Oceanic Conveyor Belt, causing temperatures in some areas to plunge.
Tim Naish from New Zealand's Geological and Nuclear Science Institute said the Antarctic ice -- which averages a depth of 2,200 meters (2,400 yards) -- contained 90 percent of the earth's fresh water and if that melted sea levels would rise by 70 meters (76 yards).
``Even a five meter rise has major implications for most nations on this planet,'' he told a government level conference of 24 out of 43 Antarctica Treaty nations.
``At the moment we are heating the earth and if the ice sheets melt it could damage the global conveyer belt and drive us into a small ice age,'' he said.
Peter Barrett from New Zealand's Victoria University of Wellington said average global temperatures through the next century could rise at over four times the rate of the last 100 years, or by as much as three degrees Celcius.
``Once the conditions are set in train to melt, the process cannot be stopped,'' Barrett, an Antarctic scientist with 30 years experience, said.
``Some people would say it's getting too late... we need awareness and political will to address the problem.''
Barrett said that as humans developed over the last 6,000 years the globe's climate and sea levels had remained stable.
``I think we're looking at significant problems in the decades ahead and incredibly depressing problems in the next century or two,'' said Barrett.
He added that the effects will vary from region to region, and that while some places would get warmer others would suffer lower temperatures.
Antarctic ice, which is on average 2,200 meters thick, accounts for around 90 percent of all fresh water on the earth's surface.
Barrett compared Antarctica, the coldest and most inhospitable place on earth, to a person with deteriorating health.
``It's like someone who's declining in health and until the problem is well advanced it's not terminal,'' he said. ``This is a wake-up call.''
``The western world features a desire toward growth and innovation... but this is not sustainable,'' he added, saying Antarctica was the key in world climate changes.
``If models are going to be believed the rates of change are going to be very quick,'' Naish said.
``We're playing Russian roulette with the climate and no one knows what lies in the chamber of the gun.''
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