A year later, when the device again recorded very low ozone numbers, Farman reasoned that some solar or geophysical disturbance, neither of which was uncommon in ANTARCTICA, was interfering with the mechanism, so he moved the machine 1,000 miles across the continent to another observation post. Here too, however, he recorded extremely low ozone levels. Farman then contacted NASA, whose Nimbus satellite was supposedly tracking Antarctic ozone levels, to see if their readings correlated to his. They did not. Later, it was discovered that NASA's computers had been programmed to ignore low readings as erroneous-- so certain were NASA's scientists of ozone's stability.

At last, in 1985, having exhausted all other explanations, Farman reported his findings in international scientific journals: a hole the size of North America had opened in the ozone layer above Antarctica. The cause, Farman speculated, was that chlorine freed from CFC's was becoming frozen into clouds in the stratosphere and then released all at once in the spring. The news came as a stunning revelation to those engaged in the CFC debate, many of whom had assumed it would be decades before the real-life consequences of ozone depletion would be observed. Finally, in September 1987, NASA flights into the stratosphere above Antarctica began carrying a new device which measured chlorine monoxide, a by-product of ozone depletion. When correlated with data showing a dramatic decrease in ozone levels, the machine's findings showed conclusively that CFCs were depleting ozone in the stratosphere. "The Smoking Gun," as the data were called, led to the capitulation of DuPont and other CFC makers. The chemical giant finally conceded that CFCs caused ozone depletion and agreed to lead the search for alternatives. That same month, representatives from 57 industrial nations met in Montreal and signed the Montreal Protocol, the world's first-ever environmental treaty, calling for a CFC phase-out.

Protocol signatories agreed to an accelerated phase-out schedule in further meetings during the late 80s and early 90s--and traded stories of deepening Antarctic ozone holes, rabbits blinded by UV-light in the Southern Hemisphere, afternoon soccer games cacelled on sunny days in Chile, and increased skin cancer in Australia and New Zealand. The latest agreement provides for a total halt in the worldwide production of CFCs to take effect January 1, 1996. Given CFC's durability in the atmosphere, this phase-out does not come in time to spare the world many more years of ozone holes and increased levels of skin cancer. What it does offer, however, is the chance that at some point, perhaps late in the 21st century, CFC levels will begin to subside, and with them the risk of CFC-caused ozone depletion.