This reading discusses the most crucial turning point in the ozone-CFC story. Mario Molina and other scientists had long predicted decreases in ozone levels would eventually be observed, but most predicted slow decreases happening over decades. In the early 1980s when the ozone hole first appeared, it shocked the world. Many computer models had been designed to predict the rates of ozone depletion, but none had predicted anything this fast, or so localized over one part of the globe. It was the ozone hole that finally convinced the world to take ozone depletion seiously, though many were still not convinced that CFCs were to blame. But it did motivated the Antarctic expeditions of Susan Solomon which eventually persuaded governments and CFC manufacturers to begin addressing the problem seriously.

There are important points that students should learn from this reading. First, our models are often inaccurate, illustrated by the failure of anyone to predict the Antarctic ozone hole. The inaccuracy of models has been used as a reason to ignore other threats of environmental disaster predicted by the use of copmuter modeling. But the experience with ozone depletion models has shown that the predictions can be inaccurate by not being dire enough. In this case we would have done well to heed the warnings of the inaccurate models because the real situation was even more dangerous. This has lessons for us as we deal with other environmental threats. For example, those who resist reducing emissions in greenhouse gases claim that the models predicting disaster from the greenhouse effect are inaccurate. They may well be, but the lesson of the ozone-CFC issue is that the inaccuracy of computer models doesn't mean the threats they predict aren't real. It can just as easily mean the threats can be much bigger than anyone can imagine.

Relevant National Science Education Standards

Unifying Concepts and Processes — The reading discusses the evidence which would be needed to prove the Molina model for the destruction of stratospheric ozone.

Physical Science — The reading deals measurement of ozone levels and with the interaction of energy (UV radiation) with ozone in the earth's atmosphere.

Earth and Space Science — The reading introduces a human-induced geochemical cycle, that of the seasonal thinning of the ozone layer over Antarctica.

Science in Personal and Social Perspectives — The reading involves an environmental quality issue which is also a human-induced health hazard, plus the use of science in overcoming this global challenge.

Next: Why Is Ozone Disappearing?