In Antarctica, No Warming Trend
Scientists Find Temperatures Have Gotten Colder in Past Two Decades
By Guy Gugliotta
Washington Post Staff Writer
Monday, January 14, 2002; Page A02
The Earth may be in the midst of a
planet-wide warming cycle, but in a
startling departure from global trends,
scientists have found that temperatures
on the Antarctic continent have fallen
steadily for more than two decades.
Researcher Peter Doran said scientists working in the McMurdo Dry Valleys of east
Antarctica have found temperatures dropping at a rate of 1.2 degrees Fahrenheit per
decade since 1986, and have observed similar downward trends across the continent
since 1978.
Doran stressed that although scientists could not explain the falling temperatures, the
research "does not change the fact that the planet has warmed up on the whole. The
findings simply point out that Antarctica is not responding as expected."
The United Nations' Intergovernmental Panel on Climate Change has concluded that
there has been a net rise in global air temperature of 0.1 degrees Fahrenheit per decade
in the 20th century, a calculation that includes the Antarctic data.
Doran also warned that "you don't want to overstate the effects" of the cooling trend,
because any rise in sea level caused by global warming this century is expected to come
from thermal expansion of existing oceans and not from any theoretical melting of the
southern ice cap.
"I'd be very careful with this," added Michael Oppenheimer, chief scientist for
Environmental Defense. "My general view has been that there's simply not enough data
to make a broad statement about all of Antarctica."
In a paper published yesterday in the online version of the journal Nature, Doran and
other members of the National Science Foundation's Longterm Ecological Research
team presented data gathered during years of research in the Dry Valleys near
McMurdo Sound.
The Dry Valleys are a perpetually snow-free mountainous desert of chill, arid soils,
bleak, bedrock outcroppings and ice-covered lakes. Microscopic invertebrates, mostly
nematodes, make up a fragile ecosystem.
Maintenance of this marginal environment depends on an annual period of four to six
weeks of above-freezing temperatures during the southern summer, Doran said. The
relative warmth causes melt water from hillside glaciers to cascade downward in
seasonal arroyos that feed the lakes.
"A lot of the people [co-authors] in the paper have been working in the valleys since
the mid-'80s, and at first it seemed that lake levels were going up," said Doran, a
hydrometeorologist from the University of Illinois at Chicago.
"But two or three years ago, when we were waiting for the big summers, we noticed that
they didn't come," he added. "We were thinking that warm summers were the norm, and
we were saying, 'It's going to get back to normal,' but it never did."
So the researchers began looking at data collected since the project's inception, and
found that temperatures had been dropping, not rising, since 1986, with the effect most
pronounced in summer and autumn. Glacial ice wasn't melting, streams weren't flowing,
lakes were shrinking and microorganisms were disappearing.
Next, Doran said, the scientists looked at data collected since 1966 from permanent
installations throughout the Antarctic. Previous studies had shown overall warming,
but the researchers found that these calculations relied disproportionately on readings
from the Antarctic Peninsula, the continent's northernmost piece of land and home of
the greatest number of scientific outposts.
The peninsula projects into the south Atlantic and "seems to be part of the regular
climate tendency" toward global warming, Doran said, while the Antarctic continent is
ringed by a cold water current that isolates the landmass in its own ecosystem.
When the researchers corrected for the peninsular distortion, they found that
Antarctica as a whole had gotten considerably colder. "Temperatures were rising
between 1966 and 1978," Doran said, but then they started to fall and have continued
falling ever since.
Doran said the researchers cannot explain why this has happened. They do know that
temperatures in the Dry Valleys get warmer when the wind blows and when there are
clouds in the sky.
He explained that as winds roll downhill off the Antarctic plateau into the Dry Valleys,
the air compresses and heats up as a result, an effect similar to the Chinook winds of the
western United States.
At the same time, relatively warm summer winds gathering speed over the ocean bring
warmer air in from the coast to promote the thaw, he said. Wind generally brings clouds,
he added, which appear to add to the warming effect.
Recently, however, "we're getting a decrease in winds from both directions," Doran
said, and, perhaps as a consequence, temperatures in the Dry Valleys are dropping. "It's
clearly connected to the winds, but what's controlling the decrease in the winds is not
clear."
Also, he noted, still air in the Dry Valleys tells researchers nothing about why
temperatures are dropping on the plateau: "We've sort of hit a point where we're a little
confused," he said.
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