Ozone hole explanation

By the late 1980s, the chemical foundation of the ozone hole in heterogeneous chlorine chemistry was firmly established (WMO, 1989, and references therein). However, the suite of proposals initially advanced to explain its origins prior to that time is of interest both historically and as an illustration of how differing proposals constructively add to and refine scientific debate. Here we briefly summarize the primary explanations advanced to explain the ozone hole following its surprising discovery. 

It was initially suggested that the Antarctic ozone hole could be explained on the basis of solar cycles or purely atmospheric dynamics. Neither explanation was consistent with observed features of the ozone hole. Chemical explanations based on the gas-phase catalytic cycles described above were advanced. As noted, little ozone is produced in the polar stratosphere as the low Sun elevation (large solar zenith angle) results in essentially no photodissociation of 02. Thus catalytic cycles that require oxygen atoms were not able to explain the massive ozone depletion. Moreover, CFCs and halons would be most effective in ozone depletion in the Antarctic stratosphere at an altitude of about 40 km, whereas the ozone hole is sharply defined between 12 and 24 km altitude. Also, existing levels of CFCs and halons could lead at most to an 03 depletion at 40 km of 5-10%, far below that observed. 

It was initially suggested that the Antarctic ozone hole could be explained on the basis of solar cycles or purely atmospheric dynamics. Neither explanation was consistent with observed features of the ozone hole. Chemical explanations were advanced based on the... 

In 1986, the National Aeronautics and Space Administration (NASA) chose Solomon (then 30 years old) to lead a team to Antarctica to sort out the right explanation for the ozone hole. Experiments during that visit to Antarctica showed that her cloud theory was correct, and a second... 

In 1985, a British team at Halley Bay Station, Antarctica, discovered the existence of a hole in the ozone layer above that continent. This totally unexpected phenomenon needed an explanation, and Susan Solomon—a young National Oceanic and Atmospheric Administration (NOAA) scientist—first proposed a good theory for it. While attending a lecture on polar stratospheric clouds, she realized that ice crystals in the clouds might do more than just scatter light over the Antarctic. Her chemist s intuition told her that the ice crystals could provide a surface on which chemical reactions of CFG compounds could take place. 

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