This year is the 40th anniversary of the discovery of ozone hole. On 16 May 1985, British Antarctic Survey scientists published research that revealed a significant drop in ozone levels above Antarctica, referred to as the “ozone hole.” Stratospheric ozone loss has also been observed over the Arctic.

Ozone (O3) is a molecule formed by three oxygen atoms. In the lower troposphere O3 is considered a pollutant, as it can cause respiratory problems when breathed. Ozone in the stratosphere absorbs UV rays from the sun, protecting life on Earth from harmful radiation that can cause skin cancer and other health problems.
Scientists found that chlorofluorocarbons (CFCs), used in aerosol cans and refrigerators at the time, were destroying the stratospheric ozone. This discovery led to the 1987 Montreal Protocol, an international agreement to freeze production and consumption of ozone-depleting substances at 1992 levels.
Thanks to the cooperation of scientists, governments, and industry, the use of CFCs declined drastically. Later amendments tightened restrictions with global CFC production and consumption phased out by 2010.
Satellites are used to routinely monitor the ozone levels in the atmosphere. Antarctic ozone depletion is seasonal, occurring primarily in late winter and early spring (August-November). Peak depletion occurs in early October. The size of the Antarctic ozone hole is gradually decreasing. In 2024, the ozone hole was the seventh smallest since monitoring began in 1992. CFCs can remain in the atmosphere for 50 years or longer, so full recovery may not happen until after 2070.
The global response to the ozone hole crisis demonstrates the effectiveness of integrating science, diplomacy, and policy. The Montreal Protocol is regarded as one of the most successful international environmental agreements in history. It highlights the advantages of addressing issues proactively and underscores the significance of expert knowledge in resolving such matters.
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.