Why Is the Ozone Hole Over Antarctica Shrinking?

The ozone layer is smaller than it has been in 30 years. This is thanks in part to human actions like eliminating CFCs, but NASA says it isn’t a sign of rapid healing.

It’s hard to go a day without reading about climate change. As unprecedented heat waves and extreme weather events become regular occurrences, it can be easy to forget about the massive stratospheric event that brought all this to our attention: the hole in the ozone layer.

As it turns out, there’s a good reason we don’t hear much about the ozone layer these days: the hole is smaller than it’s been in 30 years. NASA and NOAA announced earlier this month that the hole, created in part by the use of synthetic substances called chlorofluorocarbons (CFCs) in refrigerators and aerosols, reached its largest size for the year on September 11. On that day it covered about 7.6 million square miles, or an area about 2.5 times the size of the U.S. That’s about 1.3 million square miles smaller than it was a year ago, and it appears that it’s still shrinking.

The ozone layer protects the earth from most of the sun’s UV light. After the hole was detected in 1985, many countries minimized the use of CFCs, which break down when they come into contact with UV rays and release chlorine and bromine that damages ozone. It seems like, for once, humans did something for the environment, and it worked.

While this feels like something to celebrate in what is otherwise a pretty dark time for the climate, however, NASA has some words of caution: “The smaller ozone hole extent in 2016 and 2017 is due to natural variability and not a signal of rapid healing,” the organization said in a statement.

At least some of the hole’s shrinkage over the past three decades can be attributed to human changes, but this year’s record low is actually due more to warmer air in the Antarctic.

“The Antarctic ozone hole was exceptionally weak this year,” Paul A. Newman, chief scientist for Earth Sciences at NASA’s Goddard Space Flight Center, said in the statement. “This is what we would expect to see given the weather conditions in the Antarctic stratosphere.”

As the low-pressure system in the Antarctic stratosphere becomes warmer and more unstable, NASA explains, there is less cloud formation in the lower stratosphere, which means less chlorine- and bromine-catalyzed reactions to destroy ozone. Essentially, this phenomenon is making conditions in the Antarctic stratosphere look more like those in the Arctic, which doesn’t have as much of an ozone problem.

But experts are still excited about the progress that’s been made, thanks at least in part to humans’ willingness to give up CFCs. The scientists who helped discover the hole in the first place are excited that their recommendations have actually been followed.

We shouldn’t rest on our laurels, however. NASA refers to a 2013 study showing that the ozone hole won’t fully close until 2070.

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