New Technical Report Available:
Arctic Climate Change - Observed and Modeled Temperature and Sea Ice
Variability
By Ola M. Johannessen, Lennart Bengtsson, Martin W. Miles, Svetlana I.
Kuzmina, Vladimir A. Semenov, Genrikh V. Alekseev, Andrei P. Nagurnyi,
Victor F. Zakharov, Leonid Bobylev, Lasse H. Pettersson, Klaus
Hasselmann and Howard P. Cattle
For a PDF copy of the report please see:
http://www.nersc.no/AICSEX/rep218.pdf
NERSC Technical Report No. 218 (2002)
ABSTRACT
Changes apparent in the arctic climate system in recent years require
evaluation in a century-scale perspective in order to assess the Arctics
response to increasing anthropogenic greenhouse-gas forcing. Here, a new
set of century- and multidecadal-scale observational data of surface air
temperature (SAT) and sea ice is used in combination with ECHAM4 and
HadCM3 coupled global atmosphereiceocean model simulations in order to
better determine and understand arctic climate variability. We show that
two pronounced 20th-century warming events, both amplified in the
Arctic, were linked to sea-ice variability. SAT observations and model
simulations indicate that the nature of the arctic warming in the last
two decades is distinct from the early 20th-century warm period. It is
suggested strongly that whereas the earlier warming was natural internal
climate-system variability, the recent SAT changes are a response to
anthropogenic forcing. The area of arctic sea ice is furthermore
observed to have decreased ~ 8 x 105 km2 (7.4%) in the past quarter
century, with record-low summer ice coverage in September 2002. A set of
model predictions is used to quantify changes in the ice cover through
the 21st century, with greater reductions expected in summer than
winter. In summer, a predominantly ice-free Arctic Ocean is predicted
for the end of this century.