A New Ice Age? None Soon, Snow 2 Miles Deep Implies
June 10, 2004
By ANDREW C. REVKIN
Despite the recent trend toward global warming, scientists
have long wondered whether the earth is nearing another ice
age, an end to the 12,000-year temperate spell in which
modern civilizations arose. Some have said such a
transition is overdue, given that each of the three
temperate intervals that immediately preceded the current
one lasted only about 10,000 years.
But now, in an eagerly awaited study, a group of climate
and ice experts say they have new evidence that earth is
not even halfway through the current warm era. The evidence
comes from the oldest layers of Antarctic ice ever sampled.
Some scientists earlier proposed similar hypotheses, basing
them on the current configuration of earth's orbit, which
seems to set the metronome that ice ages dance to.
Temperature patterns deciphered in sea-bottom sediments in
recent years supported the theory.
But experts say the new ice data are by far the strongest
corroborating evidence, revealing many similarities between
today's atmospheric and temperature patterns and those of a
prolonged warm interval, with a duration of 28,000 years,
that reached its peak 430,000 years ago.
The findings are described today in the journal Nature by
the European Project for Ice Coring in Antarctica.
The evidence comes from a shaft of ice extracted over five
grueling years from Antarctica's deep-frozen innards,
composed of thousands of ice layers that were formed as
each year's snowfall was compressed over time.
The deepest ice retrieved so far comes from layers 10,000
feet deep and dates back 740,000 years. The relative
abundance of certain forms of hydrogen in the ice reflects
past air temperatures.
Many ice cores have been cut from various glaciers and ice
sheets around the world, but until now none have reached
back beyond 420,000 years, making this core the first to
capture fully the conditions during that long-lasting warm
period, called Termination V.
"It's very exciting to see ice that fell as snow
three-quarters of a million years ago," said Dr. Eric W.
Wolff, an author of the paper who is an ice core expert
with the British Antarctic Survey.
Several independent researchers familiar with the project
said the case that the current warm period would be
prolonged was now strong. Yet even with this new evidence,
they said, it is based on a sketchy view of the climatic
One expert, Dr. Gerard C. Bond of the Lamont-Doherty Earth
Observatory of Columbia University, said that even though
earth's orbital characteristics were similar to those of
400,000 years ago, and even though sea and ice records
showed similar temperatures, one match did not necessarily
make a pattern.
Still, Dr. Jerry F. McManus of the the Woods Hole
Oceanographic Institution, an expert on oceans and past
climates, wrote a commentary for Nature in which he
described the new ice core record as "spectacular."
Dr. McManus said it was particularly important because it
gave the first full view of conditions during a past warm
interval that, in terms of both the planet's orbit and its
atmospheric conditions, was most like the current one.
He and the paper's authors also noted that there was a wild
card now that could cause the current era to stray from
past patterns: the intensification of earth's natural
insulating "greenhouse effect" by smokestack and tailpipe
emissions of carbon dioxide and other gases.
Many experts said the most important data from the new ice
core were yet to come, because the researchers had only
just begun to analyze air bubbles trapped when the various
layers formed. The bubbles are an archive of past
atmospheric conditions that can show how greenhouse gases
and temperatures varied long before humans were an
Dr. Richard B. Alley, an ice core expert at Pennsylvania
State University not affiliated with the project, called it
"a triumph of brilliant persistence" in the face of broken
drills and temperatures of 60 below zero at the drilling
site, which is hundreds of miles from the nearest permanent
"The current publication is something akin to the first run
on a new accelerator or the first look at a galaxy through
the latest mega-telescope," Dr. Alley wrote in an e-mail
message. "The results are clearly of value in and of
themselves, but are even more exciting for what they
promise in the future."