Ozone monitoring

In 1985 British Antarctic Survey scientists reported in the journal Nature their discovery of springtime ozone depletion over Antarctica.  It was a discovery that changed the way that we view our world.

September 16 is world ozone day.  All 197 UN Member States have ratified the Montreal Protocol up to and including the Beijing amendments.  

The Antarctic ozone hole is usually largest in early September and deepest in late September to early October.Observations from Halley since 1994 (the year when ozone depleting gasses were at their peak according to one estimate) show a slow increase of about 1 DU per year in the minimum ozone amount recorded each October, however the inter-annual variation is such that this trend is not yet significant (at the 99% level), ie the data is also consistent with no change in the minimum amount.  Although the amount of ozone destroying substances in the atmosphere is going down, the inter-annual variation in the size and depth of the ozone hole is largely controlled by the meteorological conditions in the stratosphere.  It is still too soon to say that we have had the worst ever ozone hole, particularly as there has been no major volcanic eruption in the Southern Hemisphere since 1992.

Prior to the formation of ozone holes, Antarctic ozone values were normally at their lowest in the autumn (ie March).  On occasion atmospheric vertical motions create small areas with ozone substantially below the long term average.  Different satellites give different views of the exact ozone distribution.  The continent covers 14 million sq. km.