- 10 Jun 2004 06:17
#186773
http://www.nytimes.com/2004/06/09/scien ... ner=GOOGLE
Qui desiderat pacem, praeparet bellum. - Let him who wishes for peace prepare for war. - Wer sich nach Frieden sehnt, bereite den Krieg vor.
By ANDREW C. REVKIN
Published: June 9, 2004
Despite the recent trend toward global warming, scientists have long wondered whether the earth was 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 Earth's three previous temperate intervals lasted only about 10,000 years.
But now, in an eagerly anticipated study, a group of climate and ice experts says it has 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 had already proposed similar hypotheses, basing them on the current configuration of the 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 is by far the strongest corroborating evidence, revealing many similarities between today's atmospheric and temperature patterns and those of a prolonged warm interval that took place 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 the deep-frozen innards of Antarctica, composed of thousands of ice layers formed as each year's snowfall was compressed over time.
The deepest portions retrieved so far came from layers 10,000 feet deep and dating from 740,000 years ago. 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 had reached back beyond 420,000 years, making this core the first to fully capture 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 for a prolonged warm period now was strong, but still circumstantial.
Dr. Gerard C. Bond, an expert on past climates at 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, an expert in oceans and past climates at the Woods Hole Oceanographic Institution on Cape Cod, wrote a commentary for Nature in which he described the new ice core record as "spectacular."
He said it was particularly important because it gave the first full view of conditions during a past warm interval that, both in terms of the planet's orbit and atmospheric conditions, was most like the current one.
He and the paper's authors noted that there was a wild card present 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 greenhouse gases.
Indeed, 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 influence.
"By understanding what has driven the natural changes seen in the ice record, we will create better models to predict how climate might change in the future," Dr. Wolff said.
Climate experts not associated with the project agreed, saying the longer record provided by this ice core provided more chances to test a computer simulation's ability to recreate past conditions.
Outside experts and the European team also agreed that the discoveries had only just begun.
In the next 6 to 12 months, the team is to decipher changes in the atmosphere over the full 740,000-year span. And more ice is still being extracted from the hole, potentially taking the record back another 100,000 years or more.
Dr. Richard B. Alley, an ice-core expert at Penn State 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 research hub.
"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," he 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."
http://www.nytimes.com/2004/06/09/scien ... ner=GOOGLE
Qui desiderat pacem, praeparet bellum. - Let him who wishes for peace prepare for war. - Wer sich nach Frieden sehnt, bereite den Krieg vor.
(Heat will do this to ya in summer!)
. Last year wasn't so bad, the really hot weather didn't set in until the end of June. And this year is very mild! I'm very surprised in the weather pattern we're having this year. It actually gets cool enough to wear a light jacket in the evening. I wonder if this means this year's winter will be more extreme? Not that I would mind, I enjoy winter.
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