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Global Cooling
Tue Mar 16, 2004
Listen in RealAudio 
People around the world are concerned with a potential for a warming climate, but could it
actually lead to a drastic global cooling? Hi, I'm Bryan Yeaton for The Weather Notebook's
weekly segment on global climate change.
Some scientists, who take stock in this theory, based their belief in what they found in the
world's ocean currents, in particular, the cool North Atlantic. In "The Atlantic" magazine,
the University of Washington's William Calvin says that the theory is based on plain old
salt.
WC: The North Atlantic current has an unusual path in that it dives to the bottom of the
ocean while it's up in the Greenland Sea or the Labrador Sea. And the reason it dives to the
bottom basically is because it becomes salt heavy on the surface. All the evaporation from the
cold air from Canada blowing across it. And this leaves the surface of the ocean so salt heavy
that it actually sinks to the bottom.
This brings cold water to the bottom of the ocean, says Calvin, but global warming could alter
these currents.
WC: Basically what happens in global warming is you get more evaporation from the
tropical oceans, and this falls as rain in the northern and southern oceans. And in the North
Atlantic because of this unusual current mechanism, it may stop the current from falling to
the bottom of the ocean the way it usually does, and shift the whole ocean circulation into a
different mode of operation.
If the surface water doesn't sink, the cooler water remains on top, which cools the overlying
air. If this process continues for long enough, global cooling could result.
The Weather Notebook is produced by the Mount Washington Observatory with support from the
National Science Foundation, and Subaru - Driven By What's Inside.
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