From the New York Times News Service by Walter Sullivan, New York Times Science Editor Art
From the New York Times News Service
by Walter Sullivan, New York Times Science Editor
Article appeared in _The Oregonian_, Thursday, July 15, 1993
Ice Analysis Finds Shifts In Climate Fast, Severe
To the astonishment of climate specialists, an analysis of ice
extracted from the full depth of the Greenland ice sheet has shown
that except for the 8,000 to 10,000 years since the last glacial
epoch, the climate over the past 250,000 years has changed
frequently and abruptly.
The findings suggest that the period of stable climate in which
human civilization has flourished might be unusual, and the the
current climate may get either warmer or colder much more quickly
than had been believed -- in spans of decades or even less.
The data are likely to bolster concern that future changes in
climate might not be spread over many centuries, allowing farmers to
adjust to altered growing conditions and coastal cities to deal with
rising sea levels, for example.
Scientists have speculated for years about the effects of climate
warming. Even a rise of a few feet in sea level would flood many
food-producing regions and populous areas.
Commenting on the new research, Dr. Andrew J. Weaver of the
University of Victoria in British Columbia said that if the climate
became colder, Europe would be covered with snow much longer. As
glaciers advanced, he said, they would reflect more of the sun's
energy back into space, chilling the climate even more.
The scientists said their data showed that a significantly colder
period had occurred during the last interval between glacial epochs,
about 115,000 to 135,000 years ago. They said they could not tell
whether that meant similar changes were in store.
Previous studies had shown that there were abrupt changes in climate
during glacial epochs, but the new results, which are being reported
Tuesday in two papers in the journal Nature, unexpectedly showed
that the same was true in the periods when glaciers had retreated.
In one "catastrophic event" at the height of the last interglacial
period, the average temperature plunged 25 degrees Fahrenheit, to
ice-age levels, for about 70 years, the scientists reported.
The authors said they had no explanation for the rapid shifts. They
also said it was a mystery why the climate of the last 8,000 to
10,000 years had been "strangely stable."
In a commentary in the journal, J. W. C. White of the Institute of
Arctic and Alpine Research of the University of Colorado said it was
"difficult to express the importance" of the reports on the ice
"Adaptation -- the peaceful shifting of food-growing areas, coastal
populations and so on -- seemed possible, if difficult, when abrupt
change meant a few degrees in a century," he wrote. "It now seems a
much more formidable task, requiring global cooperation with swift
recognition and response."
The new studies found that the average global temperature can change
as much as 18 degrees Fahrenheit in a couple of decades during
interglacial periods, White said. The current average global
temperature is 59 degrees Fahrenheit.
The Greenland studies are based on ice samples extracted by a
consortium of scientists from eight European nations. They reached
a depth of 9,938 feet, using a drill mounted on the crest of the
Greenland ice cap, 10,624 feet above sea level. Pebbles and silt in
the last 20 feet of ice indicated that bedrock was near.
The article included graphs showing the temperature for the last
250,000 years. Until about 15,000 years ago the plot is
reminiscient of "popcorn noise," then there is a big hiccup where
the temperature abruptly rises, then gradually falls in fits until
about 12,300, then abruptly falls a lot (something to do with the
"Younger Dryas"?) and remains stable for a bit, abruptly rises a
lot at about 11,500, gradually rises some more until 10,000, and
then stabilizes. Unfortunately the temperature axis has no
numerical scale. The caption said that temperatures were determined
from O16 - O18 isotope ratios.
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