Nearly 30 years ago, almost every country in the world signed the Montreal Protocol to ban chlorofluorocarbons (CFCs) used in refrigerators, aerosols, and dry cleaning. The chlorine in CFCs was said to interact with ozone in the atmosphere to deplete the ozone layer. MIT scientist Susan Solomon’s work helped provide the impetus for the Montreal Protocol, and now she’s the lead author on a study recently published in Science revealing the Antarctic ozone layer may be healing at last.
Each year around August, the ozone hole begins to open, and is typically fully formed in October. In the past, scientists have usually scrutinized the ozone hole in October, but Solomon and her team – which includes five other scientists from the National Center for Atmospheric Research in Colorado and the University of Leeds in the UK – decided to switch their focus to September. According to Solomon, “September is a better time to look because chlorine chemistry is firmly in control of the rate at which the hole forms at that time of the year.” The team tracked September ozone hole data between 2000 and 2015. They looked at satellite measurements of ozone and at meteorological changes.
Their findings provide a lot of hope. Chlorine levels in the atmosphere are dissipating, and the ozone hole is shrinking. September’s ozone hole has diminished by over 4 million square kilometers, which is almost “half the area of the contiguous United States.” The scientist team did see an ozone depletion spike in 2015, but were able to link it to a volcano eruption in Chile. Solomon thinks the ozone hole might even close up in the middle of this century.
Solomon said, “We can now be confident that the things we’ve done have put the planet on a path to heal…Science was helpful in showing the path, diplomats and countries and industry were incredibly able in charting a pathway out of these molecules, and now we’ve actually seen the planet starting to get better. It’s a wonderful thing.”