Most recent analysis of the Southern Hemisphere total ozone from the an instrument on board the NOAA polar orbiting satellite. In austral spring the analysis shows the “ozone hole” (values below 220 Dobson Units) over Antarctica and the Antarctic Ocean.
Credit: NOAA

NOAA, NSF OBSERVE 20TH ANNIVERSARY OF OZONE HOLE ‘SUCCESS STORY’

August 22, 2006 — Twenty years ago this month, four teams of scientists from NOAA, NASA and two universities arrived in Antarctica seeking to determine the cause of a “hole” in the Antarctic ozone layer. Their efforts helped determine the chemical basis for the ozone loss and formed the scientific basis for the resulting international treaty phasing out the production of chlorofluorocarbons, or CFCs, which has led to a decline in ozone-depleting gases. …

The ozone layer is a thin, invisible layer of the Earth’s atmosphere about 15 miles thick. A British Antarctic Team first looked at results that showed a decline in stratospheric ozone over Antarctica in 1985, and doubted their findings. After rechecking their data and their instruments, they determined that there was a hole in the ozone. …

Theories about the cause included solar activity that affected the magnetic field, atmospheric motions and chemical reactions involving chlorofluorocarbons (CFCs), which had been used since the 1930s as refrigerants and propellants, such as aerosol sprays. … The work conducted by the Antarctic team in the 1986 field study was the first to show that a chemical reaction triggered by the CFCs was indeed the cause. Scientific papers have been published recently showing early signs of a leveling off of ozone loss, linked to the success of international agreements to control CFC emissions worldwide.