ECMWF: Total Ozone Reanallysis - 25 September 2017 - Atmosphere.Copernicus.eu
The ozone hole seems like the quintessential ‘80s issue, but unlike car phones and mullets, it is still relevant in several ways. First of all, it’s still there, chilling over Antartica. However, according to a new study, it's also slowly healing, thanks to sound environmental policy.
It’s been nearly thirty years since the world adopted the Montreal Protocol, the landmark treaty that banned the use of ozone-destroying chlorofluorocarbons (CFCs). Nevertheless, despite a firm scientific understanding of the connection between CFCs and ozone depletion, it has been tough to estimate how much of a success the protocol has been as the ozone hole didn’t begin to show signs of recovery until only a few years back.
Moreover, no one had measured the chemistry of the hole to check if ozone-destroying compounds are declining as we would expect because of the Montreal Protocol.
Earth’s stratosphere, from space. Image: NASA
A study published in Geophysical Research Letters addresses this knowledge gap. The authors of the study, from NASA’s Goddard Spaceflight Center, made use of some data collected by NASA’s Aura satellite, which measures a suite of trace atmospheric gases to understand the changes to the ozone layer, Earth’s climate, and air pollution.
Strahan and her colleague Anne Douglass examined changing ozone levels above Antarctica throughout the austral winter from 2005 to 2016. They discovered that ozone depletion had declined by about 20%. Then, they looked at levels of hydrochloric acid in the stratosphere at the end of winter, which indicated how much ozone had been destroyed by CFCs.
Chlorine levels also declined, at a rate of about 0.8% per year. That is in line with model expectations of how much CFC levels should have declined over the same period thanks to the Montreal Protocol’s ban.
Bill Randall, an atmospheric scientist at the University Corporation for Atmospheric Research who wasn't involved with the study, told Earther that he thought the paper’s analysis was “very well done.”
“They’re seeing net decreases in chlorine that are very consistent with the Montreal Protocol,” he said. “That’s a big take-home message, that the Montreal Protocol is doing what we think it should be doing.”
Indeed, the Montreal Protocol continues to prove that science and policy can work together to solve such environmental problems. In the case of the ozone hole, it has taken decades for the results to become apparent. As Strahan estimates, the hole will not be totally healed until the 2060s to 2080s, assuming we don’t begin to screw it up anew.
However, at a time when it often feels as scientists and politicians are on different sides of a giant ice wall holding on for eternal winter to arrive, the fact that science-based policy can bring results is worth remembering.
As Strahan put it, “It’s nice to have some positive environmental news for a change.”
Reference: Earther
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