Stratospheric Ozone Depletion - The Changing Arctic Environment: The Arctic Messenger - page 99

James Lovelock is a British scientist whom most people recall as the founder of the
Gaia hypothesis. Early in his career in the mid-1950s, he designed an instrument called the
electron capture detector that could be used to detect very small amounts of an organic gas
in the atmosphere. In papers published in 1970 and 1973, he showed that concentrations of
chlorofluorocarbon (CFC) gases were very high and ubiquitous in the atmosphere. For ex-
ample, CFC-11 was present at concentrations of 60 parts per million over Ireland and they
were even found in Antarctica.
CFCs were first produced commercially in the 1930s. By the 1950s, they were widely
used around the world as a propellant in spray bottles; as a coolant in refrigerators, freezers
and air-conditioning units; and in the production of plastic foams and polystyrene. One of
the reasons for their popularity was they were chemically inert and therefore resisted de-
gradation. This is why they gradually accumulated in the atmosphere to the concentrations
observed by Lovelock.
The next significant steps came in 1974. First, Richard Stolarski and Ralph Cicerone
outlinedhowchlorineatomscouldattackozonecatalytically iftheyeverreachedthestrato-
sphere. Then, in a paper published in Nature , Mario Molina and Frank Rowland described
how this could and almost certainly was taking place. Their laboratory study showed that
CFCs could spill over from the troposphere into the stratosphere, where, in the presence
of UV radiation, they would be broken apart and their chlorine released into the strato-
sphere. Stratospheric ozone would then be attacked by the free chlorine atoms, resulting in
the release of oxygen gas (O 2 ) and chlorine monoxide (ClO). As chlorine monoxide is very
unstable, its chlorine would be quickly released and be available to attack another ozone
molecule. Today, it is believed that a single chlorine atom released in this way could react
with about 100,000 ozone molecules in something like a runaway chain reaction.
Molina and Rowland estimated that the continued use of CFCs would substantially
thin the ozone layer, which would remain depleted for many decades due to the huge in-
ventory of CFCs in the troposphere reported by Lovelock. Two decades later, in 1995,
Mario Molina, Frank Sherwood Rowland and Paul Crutzen shared the Nobel Prize for
chemistry “for their work in atmospheric chemistry, particularly concerning the formation