Planetark.org, Dec. 17, 2007
Experts working on the UN's Intergovernmental Panel on Climate Change have suggested a maximum 21st century sea level rise -- a key effect of global climate change -- of about 32 inches (0.8 metres).
But researchers said in a study appearing on Sunday in the journal Nature Geoscience that the maximum could be twice that, or 64 inches (1.6 metres).
They made the estimate by looking at the so-called interglacial period, some 124,000 to 119,000 years ago, when Earth's climate was warmer than it is now due to a different configuration of the planet's orbit around the sun.
That was the last time sea levels reached up to 20 feet (6 metres) above where they are now, fueled by the melting of the ice sheets that cover Greenland and Antarctica.
The researchers say their study is the first robust documentation of how quickly sea levels rose to that level.
"Until now, there have been no data that sufficiently constrain the full rate of past sea level rises above the present level," lead author Eelco Rohling of
Rohling and his colleagues found an average sea level rise of 64 inches (1.6 metres) each century during the interglacial period.
Current models of ice sheet activity do not predict rates of change this large, but they do not include many of the dynamic processes already being observed by glaciologists, the statement said.
Sea Rise Seen Outpacing Forecasts Due To
Planetark.org, Aug. 23, 2007
Millions of people, from
Chris Rapley, the outgoing head of the British Antarctic Survey, said there were worrying signs of accelerating flows of ice towards the ocean from both Antarctica and
"The ice is moving faster both in
"I think the realistic view is that we will be nearer a metre than the 40 cm" in sea level rise by 2100. The UN climate panel in February gave a likely range of 18 to 59 cm this century, for an average around 40 cm.
Asked at the seminar what the upper limit for the rise might be at a probability of one percent or less, he said: "At this extremely unlikely level the maximum would be two metres."
Sceptics often dismiss such low probabilities as scaremongering. But many scientists note that people take precautions such as to insure their homes against far lower risks, such as fire.
The UN panel said that rising temperatures due to more and more greenhouse gases from human activities led by use of fossil fuels were melting ice.
All other glaciers on land, from the Norwegian Arctic to the
Glaciers around Ny Alesund, which calls itself the world's most northerly settlement, are also retreating fast.
The UN's Intergovernmental Panel on Climate Change (IPCC) in February hedged its forecasts by saying that "larger values cannot be excluded" but said there was too little understanding of how ice sheets react if water seeps beneath them and lubricates their slide.
Rapley said there were worrying signs of an accelerating thaw both in
"The East Antarctic ice sheet is always dismissed as the big bit which sits on rock above sea level and so is much more stable. But the radar altimeters show significant discharge going on," he said.