New evidence supports theory of global climate mechanism

Orono, Maine -- Climate changes at the end of the last Ice Age appear to have been operating in unison in parts of the northern and southern hemispheres, according to an article published in this week's edition of the journal Nature. The findings will be useful in other research aimed at determining the causes of abrupt climate changes that occurred in the past.

Patricio Moreno of the University of Chile is the lead author of a team of scientists including George Jacobson and George Denton of the University of Maine's Institute for Quaternary and Climate Studies and Thomas Lowell of the Department of Geology at the University of Cincinnati. Their article, "Interhemispheric climate links revealed from a late-glacial cooling episode in Southern Chile," also suggests a possible link in time between human activity and evidence for fire found in lake sediments near Monte Verde. Archeologists have suggested that Monte Verde is the earliest known site of human habitation in the Americas, although that theory has been challenged. The sedimentary evidence for fire dates to approximately 1,500 years after the earliest time claimed for nearby human occupation.

Pollen evidence presented in the paper suggests that climate reached "near-modern conditions" between 15,400 and 14,100 years ago and was followed by cooling events between 14,100 and 13,400 years ago. The end of this cool episode occurred 11,200 years ago. Those results are similar to the timing and direction of changes recorded in Europe and Greenland.

The authors note that evidence from higher southern latitudes suggests that changes in climate were not uniformly distributed across the Southern Hemisphere. Sediment cores from the South Atlantic, ice cores from interior Antarctica and pollen remains from further south in Chile point to changes that were out of step with the Northern Hemisphere.

"Our results, along with other studies in the southern Alps of New Zealand, constitute the southernmost records that show a pattern of climate change similar to some, not all paleoclimate records from the Northern Hemisphere. South of that region, paleoclimate records seem to show an �Antarctic signature,�" says Moreno.