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February
15, 2007 A new report on
climate over the
world's southernmost continent shows that temperatures during the late
20th
century did not climb as had been predicted by many global climate
models. This comes soon
after the latest
report by the Intergovernmental Panel on Climate Change that strongly
supports
the conclusion that the Earth's climate as a whole is warming, largely
due to
human activity. It also follows a
similar finding
from last summer by the same research group that showed no increase in
precipitation over David Bromwich,
professor of
professor of atmospheric sciences in the Department of Geography, and
researcher with the "It's hard to see a
global
warming signal from the mainland of Bromwich says that
the problem
rises from several complications. The continent is vast, as large as
the "The best we can say
right
now is that the climate models are somewhat inconsistent with the
evidence that
we have for the last 50 years from continental "We're looking for a
small
signal that represents the impact of human activity and it is hard to
find it
at the moment," he said. Last year,
Bromwich's research
group reported in the journal Science that Antarctic snowfall hadn't
increased
in the last 50 years. "What we see now is that the temperature regime
is
broadly similar to what we saw before with snowfall. In the last decade
or so,
both have gone down," he said. In addition to the
new
temperature records and earlier precipitation records, Bromwich's team
also looked
at the behavior of the circumpolar westerlies, the broad system of
winds that
surround the Antarctic continent. "The westerlies have
intensified over the last four decades of so, increasing in strength by
as much
as perhaps 10 to 20 percent," he said. "This is a huge amount of
ocean north of Some researchers are
suggesting
that the strengthening of the westerlies may be playing a role in the
collapse
of ice shelves along the "The peninsula is
the most
northern point of "Farther south, the
impact
would be modest, or even non-existent." Bromwich said that
the increase
in the ozone hole above the central Antarctic continent may also be
affecting
temperatures on the mainland. "If you have less ozone, there's less
absorption of the ultraviolet light and the stratosphere doesn't warm
as
much." That would mean that
winter-like
conditions would remain later in the spring than normal, lowering
temperatures.
"In some sense, we
might
have competing effects going on in Bromwich said the
disagreement
between climate model predictions and the snowfall and temperature
records
doesn't necessarily mean that the models are wrong. "It isn't surprising
that
these models are not doing as well in these remote parts of the world.
These
are global models and shouldn't be expected to be equally exact for all
locations," he said.
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