A hypothesis is advanced that natural dynamical processes might explain much of the observed late winter ozone decreases over Antarctica. For this to be the case, sometime after 1979 there must have been a substantial reduction of the wintertime planetary-scale disturbance activity in the Southern Hemisphere troposphere. The expected stratospheric response to such a natural process is to reduce wintertime polar ozone, prolong the life of the polar vortex, reduce the transport of ozone out of the middle stratosphere, and to increase the possibility of polar rising motion shortly after the return of the sun to high latitudes. All of these effects are in qualitative agreement with the observed ozone changes.