MODERN TIMES
by Art Hobson
ahobson@uark.edu
NWA Times 11 June 2005
THE OZONE STORY
Amid recent bad news
about global warming and other environmental catastrophes, I offer here an
encouraging example of a problem that humans have solved.
The story begins in 1930
when General Motors first synthesized chlorofluorocarbon (CFC)
molecules made from atoms of chlorine, fluorine, and carbon, for their
Frigidaire refrigerators. Since
CFCs are chemically inert, meaning that they do
not readily react with other substances, they are non-toxic, non-corrosive, and
non-flammable. Such a chemical can
have many uses, one of which is as the coolant in refrigerators and air
conditioners.
Marketed as Freon, CFC
production soared. In the 1940s, CFCs were employed as pressurized gases to
propel aerosol sprays, and as blowing agents to form styrofoam and foam rubber.
They created the 1950s air-conditioning revolution that facilitated
America’s shopping malls and population shifts to southwestern cities.
It was not until 1974 that
anybody bothered to ask about environmental side-effects, such as where all
these CFC molecules might be drifting.
After all, being inert they were nearly indestructible, so essentially
all the CFCs manufactured since 1930 should still be in the atmosphere. But where? Academic scientists Sherwood Roland and Mario Molina
hypothesized that CFC molecules drift into the stratosphere, 50 kilometers
overhead, where they may remain intact for decades. Eventually, high-energy solar radiation splits CFC molecules
apart, releasing chlorine, which then destroys ozone. This was alarming, because
stratospheric ozone absorbs and shields us from much of the sun’s harmful
radiation.
In 1974, most people
couldn't believe that mere coolants and spray cans could cause a global
catastrophe. A debate, of a now-familiar type, ensued. The chemical industry
argued that the theory was speculative and that there should be no CFC
restrictions without more evidence.
Environmentalists countered that it was better to be safe than sorry. A
consumer boycott caused the U.S. market for CFC-powered sprays to drop by
two-thirds, pressuring manufacturers to support CFC restrictions. In 1978, the
USA and a few other governments initiated a ban on spray propellants, the
least-essential CFC technology. It was the first time that a substance
suspected of causing global harm had been regulated before the effects were
fully demonstrated. This ban on CFC sprays ended the debate, temporarily. But
other CFC production continued to increase.
Now the scene shifts to
Antarctica. It was fortunate that
a British atmospheric survey team had been performing routine operations there
since 1956. Beginning in 1977, the team observed a new trend: ozone concentrations dropped every
spring and returned to normal in a few months. The decline was greater each
year, plummeting 40% by 1984 over an area larger than the USA. These
measurements were so unbelievable that the team delayed publication for several
years while rechecking their work. Their 1985 report was greeted with
suggestions that the effect was part of a natural cycle and would soon vanish.
But U.S. chemist Susan
Solomon thought the question warranted further investigation, and she organized
an expedition to Antarctica. She found greatly reduced atmospheric ozone
coupled with high levels of chlorine. There was indeed a growing “ozone
hole,” and it seemed related to chlorine. This was entirely unpredicted.
Rowland and Molina had thought that the effects of CFCs would occur only
gradually. Although their predictions had been greeted with disbelief, reality
was proving to be even more extreme.
Solomon offered a
hypothesis involving the ice clouds that form high above Antarctica during the
long polar winter. It was a complex process that scientists could not have
predicted. A second expedition in 1987 confirmed Solomon’s hypothesis.
In 1987, nations forged
a unique international treaty calling for ozone-destroying chemicals to be
essentially phased out by the year 2000. The Ozone Treaty,
developed mostly before Solomon's expedition, was preventive action based on
scientific theories about what might occur but had not yet been actually
observed. The USA played a leading role in the treaty. Its wisdom has been amply confirmed. We
now know that if CFC production had continued unabated for another decade,
human health effects would have been far more enormous. Despite the treaty, the known effects
include 12 million additional U.S. skin cancer cases, 200,000 U.S. deaths, eye
cataracts, suppression of immune systems, premature aging of the skin, and
decreased crop production.
Measurements show a 25% decline in the populations of microscopic plants
around Antarctica, and collapse of
the entire Antarctic ecosystem is possible.
The treaty was
extraordinarily effective. The
chemical industry, sensing a new market for ozone-friendly products, moved
rapidly to develop replacements.
CFC production plummeted, and is now nearly stopped. Rowland and Molina (but not Solomon,
unfortunately) received the 1994 Nobel Prize in Chemistry for having
“contributed to our salvation from a global environmental problem that
could have catastrophic consequences.” The treaty offers an inspiring example that radical global
environmental action is possible.
The verdict is now up to nature. Chlorine concentrations finally leveled
off in 1998 but might not fall to a safe level until 2050.
By taking sensible
action, we have managed to avoid far worse problems. But there's a zinger in this happy ending. An entirely independent problem, global
warming, has created excess moisture in the atmosphere, and this moisture has
increased the number of stratospheric clouds in the winter--precisely the sort
of clouds that support the chemical reactions leading to ozone destruction. Thus, despite declining CFC
concentrations, the CFCs that remain are more effective destroyers of ozone,
and we might be in for more decades of dangerously low ozone levels.
Humankind can solve its huge environmental problems. But we'd better get busy.