A new study conducted by an MIT-led team of researchers has suggested that the Antarctic ozone layer is now healing, and the hole has shrunk by more than 4 million square kilometers in the past 15 years. The study also reveals that this ozone recovery gets slow sometimes due to volcanic eruptions that take place from year to year.
The ozone hole occurs each September-October in the Antarctic spring. It was first pinpointed in 1980s when scientists found that chlorofluorocarbons (CFCs), the chemicals seeping out of aerosols, refrigerators, spray cans, foams, and cleaning products are damaging the ozone layer, which plays a significant role in protecting life on Earth from harmful ultraviolet solar radiations. Harmful CFCs were banned in 1987 after most countries around the world signed the Montreal Protocol.
The so-called “ozone hole” actually refers to a region of the stratosphere over Antarctica, where “the ozone gets destroyed completely.” This ozone hole lies about 10 and 25 kilometers in altitude, and attains its maximum size by the beginning of October. In the new study, Susan Solomon, the Ellen Swallow Richards Professor of Atmospheric Chemistry and Climate Science at MIT, and other team members decided to start collecting ozone levels in the month of September, when the hole starts to open up. From 2000 to 2015, the team collected Antarctic ozone hole data for the month of September. They used weather balloons as well as satellite data to examine ozone levels. Satellite measurements of sulfur dioxide from volcanic emissions were also studied. Computer simulations were then applied to compare September ozone measurements year-to-year.
The researchers found that the hole expansion rate slowed down considerably in the month of September with decline in chlorine levels in the past 15 years. The ozone hole was at its largest in 2000, but has shrunk by more than 4 million square kilometers since then.
“If you use the medical analogy, first the patient was getting worse and worse, and then the patient is stabilized, and now, the really encouraging thing, is that the patient is really starting to get better,” said Susan Solomon, who is also the former co-chair of the United Nations’ Intergovernmental Panel on Climate Change.
“We can now be confident that the things we’ve done have put the planet on a path to heal.”
“Which is pretty good for us, isn’t it? Aren’t we amazing humans, that we did something that created a situation that we decided collectively, as a world, ‘Let’s get rid of these molecules’? We got rid of them, and now we’re seeing the planet respond.”
“What’s exciting for me personally is, this brings so much of my own work over 30 years full circle,” Solomon added. “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.”
“The September size of the ozone hole shows this very systematic trend of getting smaller, and the September [measurements] also show that the ozone has begun to recover just exactly in the height range where the polar stratospheric clouds are,” she said.
Solomon believes the ozone hole could even close completely by the mid-21st century provided there are no major volcanic eruptions in the region.
“It’s been interesting to think about this in a different month, and looking in September was a novel way,” co-author Diane Ivy, a researcher at MIT’s Department of Earth, Atmospheric and Planetary Sciences, said in the release.
“It showed we can actually see a chemical fingerprint, which is sensitive to the levels of chlorine, finally emerging as a sign of recovery.”
The detailed findings of the study have been published in the journal Science.
