Antarctic ozone hole shows signs of healing

[Source: Science Recorder] Researchers from the Massachusetts Institute of Technology and the University of Leeds have discovered that the ozone layer above Antarctica has been slowly healing, a recent study published in the journal Science reports.

The ozone layer is a section of the Earth’s atmosphere that shields the planet from harmful ultraviolet rays. However, greenhouse gas emissions, pollution, and climate change have damaged it over time, opening a hole in the zone. Now, that hole is beginning to close.

Though the gap grows each August when the sun returns to the South Polar cap, the rate at which it opens in September has begun to slow down. The team found that the void in the zone first began to shrink in 2000 and has been declining ever since. It has shrunk nearly 1.7 million square miles in the past 16 years.

They also discovered that the reduction of chlorofluorocarbons — organic compounds that contains only carbon, chlorine, and fluorine — has played a big role in the healing process. These harmful chemicals were once used in refrigerants and aerosol propellants, but most of the world stopped using them in 1987 with the passing of the Montreal Protocol, UPI reports.

The hole in the ozone changes in size throughout the year because chlorine, the main threat to the layer, eats ozone molecules when the climate is both sunny and cold. As a result, the gap is biggest during October. Though most researchers study it during that peak month, the team analyzed it in September before it started to grow.

“I think people, myself included, had been too focused on October, because that’s when the ozone hole is enormous, in its full glory,” said lead author Susan Solomon, a professor at the Massachusetts Institute of Technology, according to UPI. “But October is also subject to the slings and arrows of other things that vary, like slight changes in meteorology. 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 year. That point hasn’t really been made strongly in the past.”

Using a combination of balloons and satellites, the researchers measured the size of the hole as well as its various chemical conditions. They also created models — based on declining chlorine levels in the atmosphere — that predicted the way it would shift over time. Such predictions have proven to be very close to real life measurements, suggesting most of the ozone’s healing is directly tied to implementation of the Montreal Protocol.

“Observations and computer models agree; healing of the Antarctic ozone has begun,” said study co-author Dr. Ryan R.Neely III, a lecturer in Observational Atmospheric Science at the University of Leeds, in a statement.

Source: Science Recorder
July 1, 2016