Global warming devastate glaciers
Global warming may wipe out three-quarters of Europe's alpine
glaciers by 2100 and hike sea levels by four metres (13 feet) by the
year 3000 through melting the West Antarctic icesheet, two studies
published on Sunday said.
The research places the spotlight on two of the least understood
aspects of climate change: how, when and where warming will affect
glaciers on which many millions depend for their water, and the problems
faced by generations in the far distant future.
The glacier study predicts that mountain glaciers and icecaps will
shrink by 15-27 percent in volume terms on average by 2100.
Global warming may wipe out three-quarters of Europe’s alpine
glaciers by 2100 and hike sea levels by four metres (13 feet) by
the year 3000 through melting the West Antarctic icesheet, two
studies published on Janaury 9 said. AFP |
"Ice loss on such a scale may have substantial impacts on regional
hydrology and water availability," it warns.
Some regions will be far worse hit than others because of the
altitude of their glaciers, the nature of the terrain and their
susceptibility to localised warming.
New Zealand could lose 72 percent (between 65 and 79 percent) of its
glaciers, and Europe's Alps 75 percent, meaning a range of between 60
and 90 percent. At the other end of the scale, glacial loss in Greenland
is predicted at around eight percent and at some 10 percent in
high-mountain Asia.
Meltwater will drive up world sea levels by an average of 12
centimetres (five inches) by 2100, says the study.
This figure - which does not include expansion by the oceans as they
warm - largely tallies with an estimate in the landmark Fourth
Assessment Report by the UN's Intergovernmental Panel on Climate Change
(IPCC) in 2007.
Geophysicists Valentina Radic and Regine Hock of the University of
Alaska base these calculations on a computer model derived from records
for more than 300 glaciers between 1961 and 2004.
The model factors in the middle-of-the-road "A1B" scenario for
greenhouse-gas emissions, by which Earth's mean surface temperature
would rise by 2.8 degrees Celsius (5.04 degrees Fahrenheit) during the
21st century.
The tool was then applied to 19 regions that contain all the world's
glaciers and icecaps.
But - importantly - it does not include the icesheets of Antarctica
and Greenland, where 99 percent of Earth's fresh water is locked up. If
either of these icesheets were to melt significantly, sea levels could
rise by an order of metres (many feet), drowning coastal cities.
That very scenario emerges in the second study, which focuses on the
inertial effect of greenhouse gases. Carbon molecules emitted by fossil
fuels and deforestation linger for many centuries in the atmosphere
before breaking apart.
Even if all these emissions were stopped by 2100, the warming machine
would continue to function for centuries to come, says the
investigation.
It largely bases its forecast on the "A2" emissions scenario, which
sees greater carbon pollution by 2100, stoking Earth's temperature by an
average 3.4 C (6.1 F) by century's end.
Warming of the middle depths of the Southern Ocean could unleash the
"widespread collapse" of the West Antarctic icesheet by the year 3000,
it says.
"The inertia in intermediate and deep ocean currents driving into the
southern Atlantic means those oceans are only now beginning to warm as a
result of CO2 (carbon dioxide) emissions from the last century," said
Shawn Marshall, a professor the University of Calgary in Canada.
"The simulation showed that warming will continue, rather than stop
or reverse, on the thousand-year timescale."
The two studies are published online by the journal Nature Geoscience.
AFP |