The Weather Guys

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.

With the exception of a freaky 12.1 inches of slushy snow that fell on Madison on March 25, 2023, the most recent 10-inch snowfall in the city was Dec. 20, 2012 — nearly 13 years ago!

So, it’s been a very long time since we have been visited by the kind of snowfall we saw on Nov. 29-30 — the total over the two days was 11.7 inches. More than that, the 9.3-inch accumulation officially registered at Dane County Regional Airport on Nov. 29 was the largest single-day November snowfall total ever, eclipsing the former record of 8.5 inches that fell on Nov. 30, 1940. So, not only did we finally see a hefty snowfall event after more than a decade of waiting, but we also set an early-season record as well.

Of course, none of this really bears on the complexion of the rest of the winter season. In fact, the month of December 2000 was both unusually cold and snowy, with an average temperature that was 14.1 degrees below normal accompanied by 35 inches of snowfall that was 23 inches above normal for the month. It appeared we were off to a great start for a cold, snowy winter. However, January and February followed with 12.1 inches and 5 inches below normal snowfall, respectively, and a middling 2 degrees above and 3.3 degrees below average in temperature.

So, only time will tell if this early wintry start will translate into a prolonged, robust winter season.

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.