August 2, 2008

Scientists Worry Global Warming Could Cause Global Chill

Scientists warn the climate can abruptly change, based on data that shows 12,679 years ago a dramatic cooling of the climate happened in Western Europe due to a shift of icy winds over the Atlantic.

Researchers looked at annual layers at the bottom of Lake Meerfelder Maar in Germany that showed an abrupt change in sediments consistent with a sudden chill over just one year. They studied pollens, minerals and other matter.

"Our data indicate an abrupt increase in storminess during the autumn to spring seasons, occurring from one year to the next at 12,679 years before the present, broadly coincident with other changes in this region," researchers wrote in the journal Nature Geoscience.

Scientists have studied the sharp chill towards the end of the last Ice Age, known as the Younger Dryas cooling.  However, this study by researchers in Germany, Switzerland and the United States may help clear up the causes and exact duration.

They wrote, "We suggest that this shift in wind strength represents an abrupt change in the North Atlantic westerlies towards a stronger and more zonal jet".

They believe the wind shift may have triggered factors like a slight southwards shift of sea ice in the North Atlantic caused by some other natural factors.

In the past, scientists have hypothesized a meteorite that kicked up dust and dimmed sunlight, may have been to blame for the sudden cooling.

Other theories have included a weakening of the warm Gulf Stream current, perhaps caused by a vast inflow to the Atlantic of fresh water from melting glaciers over North America or Europe.

The research findings back up evidence about conditions needed for abrupt climate shifts. Some modern scientists worry wrenching changes may be caused by global warming that is widely blamed on human emissions of greenhouse gases from fossil fuels.

Some believe if ice in Greenland melts, that could lead to a flow of fresh water into the Atlantic. They estimate that could also slow down the Gulf Stream current and bring a drastic chill despite an overall warming trend.


On the Net: