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Rising Seas
Tue Jun 22, 2004
Listen in RealAudio 
Hi, I’m Bryan Yeaton, and this is The Weather Notebook.
It’s well-established that ocean levels have been creeping up as the world warms, with
an average rise of between 1.5 and 2 mm per year during the 20th century. But the
precise cause of this rise remains unresolved.
Common sense points to melting ice – the warmer it gets, the faster glaciers and
continental ice sheets melt and release their water into oceans. But in recent years,
many climatologists have insisted that the prime factor is the increase in volume of
ocean waters as they warm – a process known as "thermal expansion." Now, just to
really mix things up, a new study published in the journal "Nature" claims that common
sense may be right after all.
After examining ocean data going back more than 90 years, researchers Laury Miller
and Bruce C. Douglas conclude that "mass increase" from melting continental ice has
played "a larger role than ocean warming in 20th-century global sea level rise."
Whatever caused sea level to climb in the 20th century, there is a growing consensus
that melting ice poses the gravest risks for the future. Greenland’s ice sheet alone has
the potential to raise sea levels by 7 meters, and according to a new study, irreversible
melting of Greenland is likely to begin in the next century.
Even the most pessimistic researchers acknowledge that it could take 1,000 years for
all of Greenland to melt, but that would be small comfort for the millions of people in
coastal cities like New York and New Orleans and low-lying nations like Bangladesh
whose homes would be destroyed by just a single meter rise in the oceans.
David Laskin brought us today’s story. The Weather Notebook is produced with funding
from the National Science Foundation, and Subaru: Driven by What’s Inside. We are a
program of the Mount Washington Observatory.
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