Polar Ice Shrinking Due to Human Activity
This segment is from NPR’s Morning Edition
Friday, December 03, 1999
http://search1.npr.org/opt/collections/torched/
me/data_me/seg_67389.htm
Bob Edwards. The broad expanse of ice that
covers much of the Arctic ocean is
shrinking, according to recent findings,
and scientists have been trying to
discover why. A study in today’s issue of
the journal Science suggests one likely
cause is human activity. NPR’s David
Baron reports.
David Baron. There is no land at the North
Pole, just ocean; but that ocean is covered
with ice, a floating white pancake that
grows and shrinks with the seasons.
Claire Parkenson. In the winter time the area
of coverage of sea ice in the Arctic is
considerably larger than the area of either
the United States or Canada.
Baron. But that ice pack is getting smaller,
says
NASA
climatologist
Claire
Parkenson. Scientists know this because
of measurements taken by satellites.
Parkenson.
The Arctic ice cover [has
been decreasing] overall. In the course of
the past two decades, it’s been retreating
at about a rate of 2.8% per decade.
Baron. That’s like losing an area the size of
Maryland every year. Measurements
from ships and airplanes suggest the pack
ice has been shrinking for the past 46
years. But how unusual is this trend?
The ice constantly fluctuates in its extent,
and it’s possible the Arctic Ocean is
going through a natural less icy period.
NASA’s Claire Parkenson and colleagues
at American, British, and Russian
institutes and universities wanted to
answer that question. They used a
computer program that simulates the
earth’s climate, and they looked at what
this model shows should naturally
happen to the Arctic ice over a 5000-year
period.
Parkenson says they then
examined how often natural variations in
climate produce reductions in Arctic ice
of the magnitude and duration seen in
recent decades.
Parkenson. And the probability of getting
that trend lasting for 46 years as the
observations show… that probability is
less than a tenth of one percent. So the
model is suggesting that it is highly
unlikely that this was exclusively due to
natural climate variability.
Baron. In other words, the study suggests,
it’s highly likely that something unnatural
is going on. That, many researchers say,
could be a warming of the earth due to
the emission of carbon dioxide and other
heat-trapping gasses by cars, power
plants, and factories. But does this study
really show with greater than 99%
certainty that human beings are
[responsible for the] melting of the
Arctic?
Dick Mort. In my opinion, that’s too strong.
Baron. Dick Mort of the University of
Washington recently headed a year-long
multi-million-dollar study of the Arctic
Ocean. He says the big weakness in the
new report is that it uses a computer to
simulate how the Arctic sea ice fluctuates
naturally.
Mort. We’re relying on these imperfect
models to tell us how much variability
there is, and we’re not all that confident
that that variability is realistic.
Baron. But the study adds to an increasingly
convincing picture that something
dramatic is happening in the Arctic. Just
a few years ago, researchers reported that
in high northern latitudes, plants have
begun greening up earlier in the Spring.
And in a paper to be published later this
month, scientists from the University of
Washington report that the Arctic pack
ice is not only shrinking in area, it’s
getting thinner, too. David Baron, NPR
News, Boston.