Yikes! Why were people destroying the ozone
layer, the natural "sunscreen" we need to survive? The answer
was our reliance on chlorofluorocarbons
(CFCs), which people once thought were ideal chemical compounds.
You could find CFCs in lots of things that helped us live better:
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Click to enlarge image
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Chlorofluorocarbons
(CFCs) contain carbon, chlorine, fluorine, and sometimes
hydrogen.
Source: NASA
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- Refrigerators
- Spray cans
- Air conditioners
- Styrofoam products
- Insulation
- Cleaning solutions
But we discovered that CFCs were "punching"
holes in the ozone layer. Here's how the discovery was made,
and what we did about it. Luckily, it's a story with a happy
ending.
DISCOVERY AND DEBATE
In 1974 three scientists in California said
CFCs were harmless close to Earth, but that they suddenly became
harmful when they reached higher levels in the atmosphere.
The sun's ultraviolet
radiation caused them to become chemically active, breaking
down the ozone
that protects life on Earth. (In 1995, these scientists won
the Nobel
Prize for chemistry.)
It was hard to measure the loss of ozone
because there were no earlier measurements for comparison. Not
using CFCs would have meant finding new ways to cool houses,
insulate schools, and clean things. This would cost billions
of dollars. So people argued whether it would be worth it.
CFCs still could be used in refrigerators,
air conditioners, and cleaning solutions. But the spray can
laws were an important start. Things settled down a bit until
...
THE GREAT OZONE HOLE
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Click
to enlarge image
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The blue shape over Antarctica shows where stratospheric ozone
has been depleted.
Source: NASA:
Ozone Measurements
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In 1985 scientists reported in Nature,
a well-respected British science journal, that there was a hole
in the ozone layer above Antarctica.
The hole over the Antarctic is seasonal, appearing in September
(spring in the Southern Hemisphere) and lasting until early
December. Each year, moreover, the hole grew larger. CFCs were
blamed.
In 1989 world leaders met in Montreal, Canada,
and agreed to reduce CFC production. The treaty is
known as the Montreal
Protocol. It worked! Scientists now are finding fewer CFCs
in the stratosphere,
and they are optimistic that the hole in the ozone layer might
disappear in the next few decades.
There's still more work to be done, but it's
good to know we really can solve problems if we put our
energy into it.
The
source of the animated image in the sidebar is the Cooperative
Program for Operational Meteorology, Education, and Training
(COMET®) website
of the University Corporation for Atmospheric Research (UCAR),
funded by the National Weather Service. ©2002 University
Corporation for Atmospheric Research. All Rights Reserved.
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Close to Earth, 
