© 2000 by Leo Poppoff

2909 17-Mile Drive

Pebble Beach, CA 93953

\(831\) 375-3302

February 24, 2000

Basin Watch

by

Leo Poppoff

FROM CLIMATE WARMING TO SNOWFLAKE NOISE

The world is warming, but the U.S. is cooling, rising sea levels cause
serious shoreline erosion, and snowflakes make noise. These are some of
the intriguing bits of news that accumulate in the untidy piles of
clippings and reports that fill the desk and floor of my office. So,
while cleaning up, I thought I'd share some of these gems with you.

Evidence for global warming continues to be confusing -- and
controversial. One of the strange results of monitoring the earth's
temperature over the past couple of decades is that surface temperatures
continue to increase, while atmospheric temperatures remain fairly
constant - or show a slight warming. Recently, National Research Council
(NRC) experts reported their learned opinion: surface temperatures are
definitely rising. Since 1978, global surface temperatures have
increased between 0.25 and 0.4 degrees Centigrade, according to the
report. Comparing that to a rise of 0.4 to 0.8 degrees during the past
century, led NRC panelists to conclude that temperature increases have
accelerated over the past two decades.

Climate models show that the lower atmosphere should heat up faster than
the surface, according to an article in "Transactions of the American
Geophysical Union." Yet, according to NRC experts, lower atmosphere
temperatures have only increased between zero and 0.2 degrees.
Explanations have been made by both fans and critics of global warming
models. Yet, the NRC panel wasn't able to settle the controversy.

To further confuse things, researchers at the National Oceanic and
Atmospheric Administration (NOAA) Climate Prediction Center reported
that the U.S. was cooling -- slightly. They conclude that the cooling is
about one-thirtieth of a degree per decade. Late summers and falls have
been cooler, while winters have been warmer. And nearly the entire
country has been wetter. On the other hand, researchers report, Europe
and the Arctic are warming.

University of Washington scientists measured Arctic ice thickness from a
Naval submarine and found that it's thinning. Satellite measurements
also recorded a decrease in ice cover of about 3 percent per decade.
Reasons for the decrease are being debated.

Antarctic ice is also retreating according to studies reported in
"Science" by other University of Washington researchers. They find that
West Antarctic ice that reaches to the ocean floor has retreated by 1000
kilometers since the peak of the last ice age. By dating ocean floor ice
positions over the past 18,000 years, the scientists determined that the
retreat has been steady since the end of the last ice age, some 10,000
years ago. Any human-induced climatic changes are simply adding to
ongoing processes, they concluded.

Studies by the International Hurricane Center show that sea levels are
rising. Researchers believe that global temperature increases during the
past century could be responsible for about half of the 20-centimeter
rise in sea level during that period. Shorelines are retreating on the
average of 150 times the rise in sea level. For example, a sea level
rise of 10 centimeters results in 15 meters of shoreline erosion. Along
the East Coast, it's been going on for at least 150 years. Implications
are serious for shoreline structures, which become more vulnerable to
storm damage as shorelines retreat.

Better news is found on the stratospheric ozone depletion front. For
years, stratospheric ozone, which shields us from biologically damaging
ultraviolet radiation, has slowly diminished. Depletion is caused by
halogens, like Freon, migrating to the upper atmosphere and reacting
with ozone. Last spring, NOAA researchers reported in "Science" that
concentrations of ozone depleting chemicals in the stratosphere have
decreased. And, in the fall, NOAA reported that the Antarctic ozone hole
has diminished in size -- as theory might predict. Of course, one year's
observation doesn't prove anything, but it's encouraging.

And here's an intriguing report from University of Washington
researchers. Falling snow seems quiet to us. But it's loud to fishes,
according to acoustical scientists.

Snow can add 30 decibels ("the difference between an office conversation
and a jackhammer") to high-frequency sound levels when it falls on
water. They describe it as "almost like thunder, very broadband
rumbling, screeeeeking stuff." Fishery biologists using sonar to count
fish find that in a snowstorm, the noise produces a mess ("like somebody
shook pepper on the screen").

A researcher at John Hopkins University explains it this way. Snowflakes
are full of air. When they fall in water, they release the air. The
water's surface tension holds down the bubbles, which vibrate in their
efforts to escape, producing the screechy sound. The noise is in the
range of 50 to 200 kilohertz. It's too high for us to hear, but it might
be darned annoying to many species of aquatic life. That's something to
think about when it's snowing over Lake Tahoe.

Well, this didn't make much of a dent in the paper piles, but it helped.