The ozone hole is a region of exceptionally depleted ozone in the stratosphere over the Antarctic. Each year for the past few decades during the Southern Hemisphere spring (August-October), chemical reactions involving chlorine and bromine cause ozone to be rapidly destroyed. This depleted region is known as the “ozone hole.”
Chlorofluorocarbons, or CFCs, are ozone-depleting chemicals that do not occur naturally. They were invented by chemists in 1928 and used as propellants in spray cans, in Styrofoam puffing agents and as coolants for refrigerators and air conditioners. In 1974, these human-made gases were first linked to ozone destruction. The United States banned the use of CFCs in 1978.
On May 16, 1985, British Antarctic Survey scientists published research that revealed a significant drop in ozone levels above Antarctica. In response to this discovery of an “ozone hole,” representatives from 23 nations met in Montreal, Canada. The resulting 1987 Montreal Protocol called for a 50% reduction in the usage and production of CFCs by the year 1999. This and subsequent international agreements, combined with the introduction of substitute chemicals, largely eliminated the use of CFCs worldwide. Although the global use of these chemicals has declined, they are very stable molecules and will stay in the atmosphere for over 50 years.
Satellite instruments provide routine global monitoring of ozone. The size of the Antarctic ozone hole is gradually decreasing. In 2025, the ozone hole was the fifth smallest since monitoring began in 1992. Because of the long life of CFCs, full recovery of the ozone hole to 1980 levels may not happen until 2070.
As the ozone hole continues to decline in size, we should reflect on the fact that it was only possible because of good science, industry adjustments and collective global cooperation over decades of sustained effort.
Steve Ackerman and Jonathan Martin, professors in the UW-Madison department of atmospheric and oceanic sciences, are guests on WHA radio (970 AM) at noon the last Monday of each month. Send them your questions at stevea@ssec.wisc.edu or jemarti1@wisc.edu.
