Oceans Swell from Greenhouse Effect?
by Thomas H. Maugh II
New measurements reveal that the oceans are warming and rising
about twice as rapidly as scientists had thought, strongly
suggesting that greenhouse warming caused by the burning of
fossil fuels has already begun, researchers said yesterday.
Satellite data indicate that the temperature of the Earth's
oceans has been rising at a rate of nearly 0.2 degrees Fahrenheit
through most of the 1980s, according to a report scheduled for
publication today in the journal Nature.
"We may be just beginning to witness the onset of (greenhouse)
warming" produced by the accumulation of carbon dioxide in the
atmosphere, according to oceanographer Alan E. Strong of the
National Oceanographic and Atmospheric Administration in
Suitland, MD.
Coincidentally, Richard Peltier of the University of Toronto
reported yesterday at an American Geophysical Union meeting in
Snowbird, UT, that the level of the oceans is rising about one-
twelfth of an inch per year -- an outcome of greenhouse warming
that researchers have long predicted.
Combined with recently reported data that five of the hottest
years in recorded history have occurred during the 1980s --
perhaps as a result of the greenhouse effect -- the new reports
offer evidence that the Earth may already have entered a period
of unprecedented heat.
"This is very important work," said glaciologist Richard Williams
of the U.S. Geological Survey. "It has taken a long time to get
people's attention, but it is happening now. I think you are
going to see a lot more things beginning to surface as the
recognition comes that we've got severe problems."
Monitoring ocean temperatures has been particularly difficult in
the past because of the vastness of the oceans. Such
measurements typically are provided by instruments on floating
buoys and by ships traversing cargo routes, leaving large areas
of the ocean unmonitored.
In contrast, satellite measurements, which are rapidly becoming
the foremost way to monitor global change, cover virtually all
areas of the globe and provide as many as 3 million observations
per month. The satellite measurements are compared closely with
measurements from buoys and ships to ensure accuracy of the data,
Strong said.
Peltier told the geophysical meeting yesterday that his
measurements yield an average increase in ocean level of about
one-twelfth of an inch each year during the 1980s, about twice
the rate scientists had previously estimated. He noted, however,
that the measurements must be interpreted cautiously because
there are very few tidal measurements in the southern hemisphere.
Most oceanographers agree that the level of the oceans has risen
as much as 2 inches over the last century. Various projections
of the increase that will result from greenhouse warming range
from 10 feet to 25 feet by the end of the next century.
Some of that increase, perhaps as much as a third, is due to
expansion of the oceans as they have warmed. Beyond that
expansion, however, "the only obvious explanation" is melting of
glaciers, particularly in Antarctica, Williams said.
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