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20th Century Not Hottest on Record

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20th Century Not Hottest on Record

By Larry O’Hanlon, Discovery News

April 8, 2003 — A study of more than 240 climate studies covering the last thousand years has found that the 20th century may be just another bump in the climate road.

Over the past several years there has been a surge in research trying to tease out climate history using ice cores, tree rings, lake, river and seafloor sediments, historical records, corals, stalagmites, fossils, dust, pollen, and lots of other ways.

The new study by researchers from the Smithsonian-Harvard Center for Astrophysics, Center for the Study of Carbon Dioxide and Global Change, and the University of Delaware’s Center for Climatic Research, brings together all the others.

“There are, indeed some very exciting developments,” said Smithsonian astronomer Willie Soon, the lead author of the lengthy study coming

out in the next issue of the journal Energy and Environment. “I was thinking that it was the right time to look at the bigger picture.”

What the team found was that the 20th century was not the hottest in the last millennium. They also found that nature’s climate records back up historical records of a “Little Ice Age” from 1300 to 1900, and a Medieval Warm Period from 800 A.D. to 1300.

The Medieval Warm Period is recorded in high latitudes in tree rings from about 950 to 1100 A.D. Another tree ring database from 14 widespread locations from 30 to 70 degrees north latitude also show the trend. Some indicate that it was even warmer then than the 20th century. Historical evidence of the same period includes records of fig trees in Germany and vineyards in England, Soon said.

“This paper took my breath away,” said archeologist Brian Fagan, who is a professor of anthropology at the University of California at Santa Barbara and author of the historical book “Little Ice Age.”

The paper goes a long way in making sense of an awful lot of different data, he said. What it does not do, he said, is refute the fact that humans are contributing to climate change. “They obviously accept the notion that there is human-caused global climate change.”

But fitting human-caused heating into the bigger climate picture is not easy because climate science lacks any central theory to make sense of what’s happening, said Soon.

It’s hoped that this new “big picture” study will help climatologists simulate specific, long-term global climate changes and perhaps point the way to such a theory.

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