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Section III
Polar Ozone Depletion
Prof. James G. Anderson
Departments of Chemistry 
and 
Earth and Planetary Science
Harvard University
[[picture]]
Perspective of the antarctic vortex showing Perseus superimposed on the wind field defining the polar jet, which provides containment of the amplified CIO concentrations. 

[[bolded]]I.Introduction[[bolded]]
The sudden onset of the ozone depletion in the antarctic vortex set a precedent for both the potential severity of global change and the time scale for the onset of such events. While we now know beyond any doubt that CFC's and halons are the source of halogen radicals that in turn control the rate of ozone destruction, we do not have answers to the following first-order questions: 

• Will significant ozone erosion occur with the arctic vortex in the next ten years, as chlorine loading in the atmosphere approaches 5ppbv? That is, will an "ozone hole" appear in the Northern Hemisphere by decade's end?
• To what extent will the antarctic ozone hole expand and deepen with this increasing chlorine loading?
• Which mechanisms are responsible for the observed ozone erosion poleward of 30°N in the winter/spring northern hemisphere reported in satellite observations summarized in the figure on the following page?
• How will these large distortions in the global distribution of ozone affect UV penetration to the surface, heating rates in the upper troposphere and stratosphere, and lapsed rate, surface temperatures, and general circulation?

The emphasis in our approach is to achieve a level of understanding adequate for prediction, and thus we focus on the processes that establish [[bold]]cause and effect.

I-13[[/bold]]