Statkraft Climate Roundtable - Chasing New Ideas - page 7

Recent devastating storm events such as Hurricane Sandy and
Typhoon Haiyan epitomize two fundamental characteristics of
human-made climate change: On the one hand, those storms
are related to strongly nonlinear systems, where small changes
of certain components may generate complex, powerful effects
throughout. On the other hand, with regard to the consequences
for the affected populations, they reveal strong inequalities that
characterize contemporary societies worldwide and that may
be aggravated by climate change. Albeit the storm damages
in developed New York and developing Tacloban City on the
Philippines cannot easily be compared, in both locations the
poorest part of the respective population suffered most after all.
If climate change continues unabated, many nonlinearities and
inequalities of similar nature – but also lurking in the realm of
the unexpected and unseen – may unfold in the future.
Among the nonlinearities that climate change scientists deal
with on a daily basis, I am personally most worried about
the so-called tipping elements in the Earth system. These
are large-scale features of our planet, which may undergo
major, irreversible transitions if pushed beyond a threshold by
continued global warming. Examples include the grand polar
ice sheets in Antarctica and Greenland, the Amazon rainforest,
and the tropical coral reefs belt. A 'novel' tipping element,
which has only recently been inspected more carefully, is the
so-called ‘jet stream’, a high-speed wind ribbon that separates
cold Arctic air from milder mid-latitude air masses. The jet
stream occasionally forms giant waves that, if they last for
several weeks, bring about severe weather extremes such
as regional heat waves and floods. New research indicates
that human-made global warming will increase the persistence
of those waves.
Regarding the likelihood of destabilizing some of these tipping
elements by anthropogenic interference, recent scientific findings
from the Potsdam Institute for Climate Impact Research show,
for example, that the slow, but irreversible loss of the Greenland
ice sheet may start already if global mean temperature is
increased by roughly two degrees centigrade. The complete
loss of that ice sheet would imply that sea levels worldwide
rose by about seven meters on average and – due to the
effects of continental gravity and ocean currents – even much
higher regionally.
Climate Change:
Nonlinearities and Inequalities
By Hans Joachim Schellnhuber
Founder and Director, Potsdam Institute
for Climate Impact Research (PIK)
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