Posted on 03/21/2002 7:06:52 PM PST by aculeus
Washington — An unusually warm period a millennium ago may have been part of a natural planetary cycle, researchers say in a study of tree rings that scrutinizes the link between human activity and climate change.
The study, appearing Friday in the journal Science, analyzed ancient tree rings from 14 sites on three continents in the Northern Hemisphere.
It concluded that temperatures in an era known as the Medieval Warm Period about 800 to 1,000 years ago closely matched the warming trend of the 20th century.
In recent years, many climate scientists have said an unprecedented warming spell that began last century and continues is caused by the Greenhouse effect.
The Greenhouse effect is blamed on an increase in the atmosphere of gases, principally carbon dioxide, from the burning of fossil fuels, which trap heat just as do glass panes in a greenhouse.
The tree-ring study gives another perspective on Earth's natural cycles, said Edward Cook of the Lamont-Doherty Earth Observatory in Palisades, N.Y. Mr. Cook is co-author of the study with Jan Esper and Fritz Schweingruber of the Swiss Federal Research Institute.
Mr. Cook said the study shows the Earth to be "capable of rapid changes and long periods of above average warmth on its own without greenhouse warming.
"We don't use this as a refutation of greenhouse warming," said Mr. Cook. "But it does show that there are processes within the Earth's natural climate system that produce large changes that might be viewed as comparable to what we have seen in the 20th century."
Mr. Cook said the study found that, based on the growth of rings in the trunks of trees that lived hundreds of years ago, the temperatures during the Medieval Warm Period were about equal to the warming trend that started in the 20th century.
"Greenhouse gases were not a factor back in the Medieval Warm Period," said Mr. Cook.
The Intergovernmental Panel on Climate Change, an international group, has predicted that the current warming trend will continue deep into the 21st century, with average temperatures rising by 1.5 and 5.5 degrees Celsius.
Based on this prediction, there have been international proposals for systematic reductions in the burning of fossil fuels. The proposal has been resisted by the United States.
Mr. Cook said data used in the climate change panel's calculation is based on a model that compared the preindustral age climate with the climate of the 20th century. The model did not include a Medieval Warm Period. Including data from that era could change the calculations, Mr. Cook said.
Keith Briffa and Timothy Osborn, climate scientists at the University of East Anglia in Britain, said the study by Mr. Cook and his colleagues "provides evidence for greater climate swings in the last 1,000 years than has yet been generally accepted."
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Don't tell President Gore.
Did you mean to say "resident Gore?"
(I can hear them asking,"Numbers? What's that? ")
Yeah, I'm in NW Indiana and had to slide to work this morning on the ice. Happy first day of Spring!!
Yes, we do, don't we. But the NY Times, Nightline and assorted other 'elite' media have always scoffed at anyone who disagrees with them on this subject.
This will be in Science -- not a right wing publication -- and it shall be interesting to see how our own media handles it.
More scientists' lies. Like we need the non-jihadist muslims to root out their own bad apples, scientists must do the same.
I like to drive my Jeep!
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