Greenland thaw biggest in 50yrs
2008-01-16 10:43
Oslo - Climate change has caused
the greatest thaw of Greenland's ice in half a century, perhaps
heralding a wider meltdown that would quicken a rise in world
sea levels, scientists said Tuesday.
"We attribute significantly increased Greenland summer
warmth and ice melt since 1990 to global warming," a group of
researchers wrote in the Journal of Climate, adding to recent
evidence of faster Antarctic and Arctic thaws.
"The Greenland ice sheet is likely to be highly susceptible
to ongoing global warming," they said. Greenland contains
enough ice to raise world sea levels by seven metres, a process
that would take centuries if it were to start.
Melt water from Greenland - excluding ice losses from
glaciers slipping into the sea - totalled 453 cubic kms in 1998, the most ahead of 2003, 2006, 1995 and
2002 in detailed records stretching back to the 1950s.
Preliminary data showed that 2007 would rank second or
third highest and confirm the last decade as the biggest melt, said Edward Hanna of England's University of Sheffield who led the study with colleagues in Belgium, the United States and
Denmark.
So far, the water runoff has been largely offset by rising
snowfalls in Greenland that may also be a side-effect of
climate change. Even freezing air can hold more moisture, and so
deliver more snow, if it gets slightly less chilly.
Demise of ice
But continued warming could threaten an irreversible
meltdown. The report noted that typical climate models pointed
to a warming for Greenland of 4-5 degrees Celsius by 2100.
"The ice probably wouldn't grow back under current
conditions," Hanna said.
"If you have an extra 3-5 degrees Celsius warming ... then
you can reach a point of no return ... bringing the eventual
demise of the ice sheet. That could take probably 1,000 or
2 000 years," he said.
On Monday, a climate researcher said that Antarctica lost
billions of tons of ice over the last decade, contributing
more to rising sea levels around the world.
The UN Climate Panel, which blames global warming mainly
on human emissions of greenhouse gases from burning fossil
fuels, projects a rise in sea levels of between 18cms and 59cms by 2100.
The panel assumes that the little-understood rate of ice
flow from Greenland and Antarctica will not change from
1993-2003, when their mass losses accounted for less than half
of annual sea level gains of 3.1mm.
Hanna said that there was also a warm period around 1940 in
Greenland - but that warming was triggered by natural
variations in the Arctic climate, perhaps shifts in ocean
currents. This time, the Greenland warming fits a far broader
trend across the planet.