Posted June 24, 2004 Atlanta
Authored by the University of Bremen's Frank Lamy and colleagues, the paper in the journal Science provides new evidence that Southern Hemisphere climate may not have changed in step with Northern Hemisphere climate. Though these new measurements of ocean surface temperature off Chile are consistent with information from Antarctic ice core samples, they still contradict measurements made on land in the Southern Hemisphere - suggesting additional research will be needed to resolve the issue.
Scientists have found evidence of rapid and dramatic climate change that took place in a matter of decades during cool periods of the last 80,000 years in the North Atlantic. Knowing whether climate changes took place simultaneously in the Northern and Southern Hemispheres is vital to understanding the mechanism involved - and assessing whether similar abrupt climate change could be a threat today.
"People are very interested in these dramatic climate changes because they occur on very human time scales," said Jean Lynch-Stieglitz, associate professor in the School of Earth and Atmospheric Sciences at the Georgia Institute of Technology and author of a "Perspectives" article accompanying the Lamy paper in Science. "It's really important to understand what is causing them and what conditions are necessary for the climate to rapidly transition from cold to warm and back again."
To understand past climate conditions, scientists study ice cores taken from frozen areas such as Greenland and Antarctica, and sediment cores taken from the ocean floor. The Northern Hemisphere has been well studied, but comparatively little data exists about the Southern Hemisphere, which has more open ocean area which provides scant data.
And the information that exists about the Southern Hemisphere is contradictory, with pollen samples and land-based data from southern Chile and New Zealand suggesting climate change synchronized with the Northern Hemisphere - and Antarctic ice cores suggesting the opposite.
Lynch-Stieglitz, who co-authored an earlier paper based on less detailed South Atlantic data, believes the new paper represents progress toward understanding Southern Hemisphere climate change.
"The real significance of this paper is that it gets us closer to understanding the mechanism causing these rapid climate changes," she said. "Earlier sediment core work at lower resolution has suggested that the Southern Hemisphere has been doing its own thing. The record from Antarctica is nicely resolved and shows that the Southern Hemisphere is not participating either in magnitude or timing with the climate changes that have occurred in the North Atlantic."