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GCC Warming Oceans
Tue Jan 13, 2004
Listen in RealAudio 
Hi, I'm Bryan Yeaton, and this is The Weather Notebook's weekly Climate Change show. Our
atmosphere isn't the only thing on Earth that's warming up, the oceans are too. And scientists
see signs that mankind is largely to blame there, as well.
The greenhouse gases now thought to be responsible for the global warming we see on the
Earth's surface, have their fingerprints on ocean warming as well, according to a new study
that looks back over the last one thousand years of the world's climate.
Down to about 300 meters deep, our oceans have warmed by about half a degree Fahrenheit in
just the last 50 years. And the top 3,000 meters have warmed an average of about a tenth of a
degree Fahrenheit.
Duke University climate scientist Thomas Crowley and his colleagues looked at the changes in
the ocean's heat content over the last thousand years. Using a model that took into account
greenhouse gases, variability in the sun's output, volcanoes, and atmospheric aerosols, they
found a small dip in the ocean's mean temperature around the time of the Little Ice Age,
between about 1600 and 1840 A.D. The temperature drop from the Middle Ages was a couple of a
tenths of a degree, with a drop in sea level of about 10 inches--about what scientists have
uncovered.
As they ran their ocean model forward, they found the oceans began heating in the mid-19th
century, just as the Industrial Revolution had begun to pump greenhouse gases into the air. By
the 20th century, greenhouse gases accounted for 80 percent of the increase in ocean heat
content, a warming which continues today.
Science writer David Appell contributed today's show. The Weather Notebook is funded by Subaru
of America and the National Science Foundation. Special support comes from Davis Weather
Instruments, at www.davisnet.com.
It is hard to know how ice sheets will act in a changing climate:
http://www.nature.com/nsu/020819/020819-9.html
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