PARIS —
Even without any future global warming,
Greenland’s melting ice sheet will
cause major sea level rise with potentially “ominous” implications over this
century as temperatures continue to rise, according to a study published
Monday.
اضافة اعلان
Rising sea levels —
pushed up mainly by melting ice sheets on Greenland and Antarctica — are set to
redraw the map over centuries and could eventually swamp land currently home to
hundreds of millions of people, depending on humanity’s efforts to halt
warming.
The Greenland ice
sheet is currently the main factor in swelling the Earth’s oceans, according to
NASA, with the Arctic region heating at a faster rate than the rest of the
planet.
In the new study,
published in
Nature Climate Change, glaciologists found that regardless of any
future fossil fuel pollution, warming to date will cause the Greenland ice
sheet to shed 3.3 percent of its volume, committing 27.4cm to sea level rise.
While the
researchers were not able to give an exact timeframe, they said most of it
could happen by 2100 — meaning that current modelled projections of sea level
rise could be understating the risks this century.
The “shocking”
results are also a lowest estimate because they do not take future warming into
account, said lead author Jason Box, of the National Geological Survey of
Denmark and Greenland.
“It’s a
conservative lower bound. The climate has only to continue warming around
Greenland for more commitment,” he told AFP.
If the high levels
of melting seen in 2012 became an annual occurrence, the study estimated
sea-level rise could be around 78cm, enough to swamp vast swathes of low-lying
coastlines and supercharge floods and storm surges.
This should serve
“as an ominous prognosis for Greenland’s trajectory through a 21st century of
warming”, the authors said.
In a landmark
report on climate science last year, the
Intergovernmental Panel on Climate Change (IPCC) said the Greenland ice sheet would contribute an estimated
maximum of 18cm to sea level rise by 2100 under the highest emissions scenario.
Box, who was an
author on that report, said his team’s latest research suggests those estimates
are “too low”.
Instead of using
computer models, Box and colleagues used two decades of measurements and
observational data to predict how the Greenland ice sheet will adjust to the
warming already experienced.
Upper areas of the
ice sheet add mass through snowfall every year, but since the 1980s the
territory has been running an ice “budget deficit”, which sees it lose more ice
than it gains through surface melting and other processes.
‘Radical’ method
The theory that researchers
used was initially developed to explain changes in Alpine glaciers, said Box.
This holds that if more snow piles up on top of a
glacier, it causes lower areas to expand. In this case the reduced snow is
driving shrinking in lower parts of the glacier as it rebalances, he said.
Box said the methods his team used were “radically
different” from computer modeling, but could complement this work to predict
the impacts of sea level rise in the coming decades.
He said while climate change was raising more
immediate threats like food security, the accelerating pace of sea level rise
will become a challenge.
“It’s kind of decades in the future when it will
just force its way onto the agenda because it will begin displacing people more
and more and more,” he said.
The world has warmed an average of nearly 1.2°C
since pre-industrial times, unleashing a catalogue of impacts from heat waves
to more intense storms.
Under the Paris climate deal, countries have agreed
to limit warming to 2OC.
But in their report on climate impacts this year,
the IPCC said even if warming is stabilized at 2–2.5°C, “coastlines will
continue to reshape over millennia, affecting at least 25 megacities and
drowning low-lying areas”, which were home to up to 1.3 billion people in 2010.
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