|| Mending the Ozone Hole:
A Triumph of Science and International Policy
by Anne C. Paine
Compelling science, good monitoring systems,
and international cooperation led to success in the effort to eliminate
the production of chlorofluorocarbons (CFCs) and stop the depletion
of the stratospheric ozone layer, according to Paul O. Wennberg '85,
professor of atmospheric chemistry and environmental engineering at
the California Institute of Technology.
In a lecture titled "Environmental Science and Policy: Stratospheric
Ozone and the Regulation of CFCs," Wennberg, one of this year's MacArthur
Foundation "genius" grant recipients, gave an overview of the development
and chemistry of CFCs and the movement to eliminate them. His Oct.
5 lecture was part of a symposium celebrating the dedication of the
Oberlin College Science Center.
The trouble began with what, at the time, seemed to be a good solution
to a vexing problem. In the 1920s, when home refrigeration was beginning,
Thomas Midgley, Jr., developed CFCs for use in refrigerants; these
gases were safer than the toxic and flammable gases being tested as
refrigerants at the time. CFCs eventually came to be used in aerosols,
propellants, and foaming agents, and they are still used today in
allergy and asthma inhalers.
(Wennberg noted that Midgley's career as a chemist had other unfortunate
environmental consequences. Midgley was also responsible for the addition
of tetraethyl lead to gasoline as an anti-knocking agent, which significantly
increased levels of poisonous lead in the air during the 20th century.
This too, at the time, was a good solution to a difficult problem,
and no one predicted the adverse consequences that resulted.)
"CFCs are cheap to manufacture, and in the 1980s they were cheaper
than milk," Wennberg said. "Eventually they make their way into the
atmosphere, which is an oxidizing medium-it breaks down compounds
that go into the air. But because CFCs are inert, there's no way for
them to be degraded, except at very high temperatures."
they are so stable, CFCs move from the lower atmosphere into the stratosphere,
where they are eventually broken down by ultraviolet rays from the
sun, releasing chlorine. This chlorine is the agent involved in ozone
destruction. The ozone layer is essential to life on Earth because
it filters out cell-damaging radiation in ultraviolet (UV) light.
By 1974, Sherwood Rowland and Mario Molina predicted from available
laboratory data that CFCs release chlorine into the upper atmosphere.
They won the 1995 Nobel Prize in chemistry for their work.
"The political response to this scientific speculation varied," Wennberg
said. "The United States, Sweden, and Canada immediately banned gratuitous
uses-primarily in propellants and foaming agents. But the CFC rates
still went up because other countries kept producing them. It was
a real problem for U.S. businesses, which were at a disadvantage because
they weren't operating on a level playing field. We were trying to
solve a global problem on a local level."
By 1985, the U.S. was taking the lead in the international arena,
and in March of that year, in Vienna, 21 nations signed on to the
Convention for the Protection of the Ozone Layer, which set a framework
to discuss and research the ozone problem. The Vienna Convention led
in 1987 to the Montreal Protocol, which bound countries to reduce
and eventually eliminate CFCs. Supplemental agreements made in London
in 1990 and in Copenhagen in 1992 strengthened the protocol.
What was still lacking was concrete, visible proof that the ozone
was being depleted. Between international meetings and conventions,
Joe Farman, a British Antarctic Survey scientist who had been plotting
data for about a decade, provided this evidence when he announced
his discovery of the Antarctic ozone hole in a 1985 article in Nature.
NASA had also been collecting data that would prove the existence
of such a hole, but considering it anomalous, administrators had put
the data aside for later evaluation.
"The problem with drinking from a fire hose and putting off anomalies
to study later is that you often don't get around to it," Wennberg
said. Within six months, NASA had confirmed Farman's work, he said.
During the 1990s, "the ozone hole continued to get broader and deeper.
It seems that 2,000 parts of chlorine per trillion is what we have
to get back to if we want to stop depletion of the ozone level. Estimates
show that it will take until 2050 to reach that level," Wennberg said.
Although complete success is far in the future, current evidence shows
movement in the right direction.
"Monitoring is taking place all over the world. We're now down 5 percent
from where we were in 1999. The Montreal conventions are working and
concentrations of chlorine are coming down," Wennberg said.
"Had we not taken action, by 2040 the UV dose would have doubled over
most of the globe. Science and policy worked together to avert a near