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Climate Switch
Tue Oct 19, 2004
Listen in RealAudio 
We used to think that climate took hundreds, even thousands of years to change. Now
we know it can happen in a mere millennium. Hi, I'm Bryan Yeaton for The Weather
Notebook.
By looking at gasses trapped inside glacial ice cores, we can analyze thousands of
years of climate change. And, these snapshots of climate history show us how quickly
fluctuations can occur.
Maybe the best example of extremely quick climate change came during a period of
time known as the Younger Dryas, which occurred right after the last ice age ended,
about 12,000 years ago. The Younger Dryas itself lasted about 1,000 years, but we
didn't know until recently was just how quickly the Younger Dryas started and stopped.
In a period of less than 50 years, the climate from the eastern U.S. and Canada to
much of Europe went from conditions much like today's, to frigid readings more like the
Ice Age, at least a 10 degree Fahrenheit change. It stayed that way for a thousand
years -- and then the climate flipped back to normal in perhaps as little as 20 years.
As the Ice Age glaciers dissolved across North America, their meltwater poured into
the Atlantic Ocean. Some researchers think this meltwater pinched off the warm Gulf
Stream, allowing the water to cool down dramatically in the northern Atlantic Ocean.
This scenario is one being debated as one of the outcomes of a warming planet.
How? The speculation goes that if global warming causes heavier rain, and more
water is being dumped into the North Atlantic, it could flip that climate switch just as in
the Younger Dryas, and changes hot or cold would occur around the world in a
climatological blink of an eye.
The Weather Notebook is a program of the Mount Washington Observatory, funded by
Subaru of America.
Today's Links
Ice Cores That Tell the Past:
http://www.gisp2.sr.unh.edu/GISP2/MoreInfo/Ice_Cores_Past.html
Ice Core Photos:
http://www.ccrc.sr.unh.edu/images/Photos.html
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