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Earth May Have Cooled 10 Degrees Over Past 3 Million Years

File Photo: Antarctica's Salty Valleys Credit: Peter West, National Science Foundation.
Newcastle - Jan. 23 2001
Researchers examining deep-sea sediments off the coast of Namibia, West Africa, have found evidence that global cooling of 10 degrees Celsius has occurred since 3.2 million years ago -- five times greater than was previously believed.

The discovery, announced in the American journal, Science, adds weight to the theory that climate change played a significant part in the evolution of early humans.

Jeremy Marlow, of Newcastle University's Department of Fossil Fuels and Environmental Geochemistry, who led the team of English, American and German scientists, said: "There have been arguments for many years about whether the emergence of our ancestors was linked to climate change.

"By looking at the molecular fossils of microscopic marine algae we began to discover evidence of a 10 degree fall in temperature in the region of Africa where much of the early human fossil evidence has been discovered.

"We didn't believe it at first but further tests kept producing similar results until we had to conclude that temperatures really had decreased so dramatically."

The scientists, from the Universities of Newcastle, Durham, California and Bremen, found that cooling was particularly rapid about 2 million years ago, at the time when the first ancestors of modern humans emerged in sub-tropical southern Africa.

The research also sheds new light on the mechanisms that may cause climate change. By examining the rate of sediment deposition and the levels of organic carbon within the sediments, the researchers obtained evidence of a well-defined cycle in which a cooling atmosphere causes increased upwelling of nutrient-rich deep waters in specific parts of the oceans leading to increased biological uptake of carbon dioxide from the atmosphere, which then cools further, causing more upwelling and uptake of carbon dioxide.

This mechanism took 100,000s to millions of years to have an effect on climate but could be reversed far more rapidly through the burning of this type of locked-up carbon as fossil fuels.

This press release is based on an article, "Upwelling Intensification As Part of the Pliocene-Pleistocene Climate Transition", published in the American journal, Science (ref 290: 2288-2291.) However, the article in Science concerns itself with factual findings and does not discuss the implications for human evolution. No press release has been issued by Science.

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Computer Models Generate Extreme Climate Events
Washington - Jan. 16, 2001
When scientists run computer models to simulate climate events, they often add elements, such as effect of volcanic eruptions, adding ice sheets, or altering the concentrations of greenhouse gases in the model's atmosphere. One NOAA scientist and his colleague discovered a large, abrupt climate event without the additions.


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