The variability of atmospheric ozone over the southern hemisphere is d
escribed, being important in understanding the health effects of ozone
depletion, A brief summary is provided of the main features and cause
s of the observed global mean ozone distribution and its seasonal cycl
e, Next follows a more detailed discussion of ozone fluctuations occur
ring across the range of timescales from a day to many Sears, their va
riation with latitude and season, and their primary causes, Then the l
ong-term trends are considered; their spatial and seasonal structure,
and current understanding of the mechanisms responsible, The paper con
cludes with a brief discussion of a few of the more pressing scientifi
c issues faced by ozone researchers, and some speculation on the prosp
ects for ozone-layer depletion into the next century.