We're not ready for the changes we're causing in the Arctic, scientist says
- 28 Apr 2014, 15:30
- Roz Pidcock
Thousands of scientists are convening in Vienna this week for a
major international conference held by the European Geophysical
Union (EGU). The conference is
huge, spanning topics from space weather to sea level rise. This
week, we'll bring you some of the best climate bits.
An abrupt start
The science community is unequivocal that human activity is
changing the climate. Last September's
report from the Intergovernmental Panel on Climate Change
(IPCC) concluded global temperatures have risen by 0.85 degrees
Celsius since 1880 and if emissions stay high, we could be looking
at warming of at least three degrees by the end of the century.
Professor James White from the Institute for Arctic and Alpine
Research at the University of Colorado opened proceedings at the
EGU conference today with a talk on abrupt climate change. Abrupt
climate change refers to the idea that steady changes in
temperature could trigger sudden and rapid shifts in the climate
system, perhaps irreversibly.
White asked if the changes in climate we encounter will be slow
enough to allow time to adapt or whether there will be tipping
Earth has been through abrupt changes in climate before, when
temperatures changed 10 to 15 degrees in less than a decade, White
explained. He and other scientists are interested in whether we
could cause similar abrupt changes to occur through greenhouse gas
White defines "abrupt" climate change as an impact that is
"unfolding faster than expected, planned or budgeted for" - one
which leaves society little time to adapt.
Using these criteria, White argues we're already seeing abrupt
climate change - notably in the loss of sea ice in the
Arctic sea ice is disappearing at a rate of about five per cent
per decade. The biggest losses occur when the sea ice reaches a
seasonal low in September, when the rate of loss is more like 14
per cent per decade.
The graph below from the recent IPCC report shows how summer sea
ice has changed since 1900, and the acceleration in ice loss in
Taken from Figure SPM.3 from the IPCC report (p.8): extent
of Arctic July-August-September (summer) average sea ice.
White classifies the change as "abrupt" because the
disappearance of sea ice is happening much faster than scientists
anticipated, White explains. Climate models
suggest that at the current rate of melting, the Arctic will be
sea ice free in summer by mid century.
Ice loss is causing other changes to occur quicker than
expected, too. New shipping routes being are carved through the
Arctic, geopolitics in the region are changing and mining for
resources is set to scale up. White warned:
"We're not ready for the impacts we're
causing in the Arctic"
In another session at today's conference, Dr Julienne Stroeve
from the National Snow and Ice Data Centre (NSIDC) explained the length of the
Arctic melt season is increasing by five or six days per
Not only is more sea ice in the Arctic disappearing in summer,
it's starting to melt earlier in the year and refreeze late, she
Stroeve's research shows interesting details within that trend,
however. Natural variation in Arctic weather causes big differences
in the length of the melt season from year to year.
In the recent record, 2007 saw the longest melt season - at
around 130 days. Summer Arctic sea ice reached the
second lowest extent on record that year. In 2013, however,
conditions were much more favourable for ice formation and the melt
season was shorter, more like 100 days.
Since ice is reflective, the dark open ocean absorbs more of the
sun's heat as the ice retreats. Stroeve's research suggests the
region's reflectivity - known as the "albedo" - is reducing at a
rate of nine per cent per decade.
Stroeve is cautious about calling these changes in the Arctic
"abrupt", however. She tells us that at the moment, scientists
aren't seeing clues in their models of sudden and complete loss of
summer sea ice.
However, the ice is getting thinner and becoming more vulnerable
to breaking up, Stroeve explained. It's not impossible that we
could see a disappearance of summer sea ice if the same weather
conditions that caused such rapid loss in 2007 were to combine with
the thinner ice we have now, she suggested.
But natural variation mean the picture may look different the
following year, so we should look at long term trends not single
years, she warned.
Some scientists have
raised concerns that a warming Arctic could release methane
from carbon-rich permafrost as it starts to thaw.
White said while this is something the average non-scientist
gets worried about, most scientists agree it's a very slow process
- the release of enough methane to have a significant impact on
global temperature would take centuries, rather than decades.
That doesn't mean we should ignore it, warned White, adding that
permafrost methane is still a concern and continued monitoring is
A more pressing cause for concern is the possibility that the
West Antarctic ice sheet destabilising and disappearing completely.
This would lead to a rise in sea level of about a metre in 30 years
rather than 100 years, which is what we might expect at current
rates of warming, White added.
While this is a high risk scenario, there's considerable
scientific uncertainty about when it could occur. The IPCC report
"Abrupt and irreversible ice loss from a
potential instability of marine-based sectors of the Antarctic ice
sheet in response to climate forcing is possible, but current
evidence and understanding is insufficient to make a quantitative
Time to get serious
There's still uncertainty about what the consequences of passing
climatic thresholds would be - as well as how close they really
are. But abrupt climate change is an economic, social and
environmental prospect that's much better avoided than dealt with,
Research should focus on the development of early warning
systems that combine the physical and social sciences, White said.
"We know how to do this much better than
we used to ... the time is here to be serious about the threat of
tipping points so as to better anticipate and better prepare
ourselves for inevitable surprises."