Good news from NASA, everyone! Measurements from satellites this past year showed that the hole in Earth's ozone layer that forms over Antarctica each September was the smallest we’ve seen since 1988!
Now small isn’t exactly small. When the hole reached its peak extent on September 11 this year, it still covered 7.6 million square miles – a size over two and a half times that of the United States. But, compared to 2016 and 2015, that’s shrinking in size! (Roughly 1.3 million square miles smaller than 2016’s hole and 3.3 million square miles smaller than 2015’s.)
Climate scientists have long noted that the hole usually reaches its peak around the middle of September and then steadily declines throughout the reach of the fall. What’s interesting about this year’s observations is how climate patterns seem to affect the hole in the ozone.
"The Antarctic ozone hole was exceptionally weak this year," said Paul A. Newman, chief scientist for Earth Sciences at NASA's Goddard Space Flight Center in Greenbelt, Maryland. "This is what we would expect to see given the weather conditions in the Antarctic stratosphere."
What Newman means by that is that the ozone hole’s size is impacted by the Antarctic vortex, the stratospheric low-pressure system that rotates clockwise in the atmosphere above Antarctica. This year the Antarctic vortex was particularly strong and unstable, which reduced polar stratospheric cloud formation in the lower stratosphere. If the clouds don’t form, fewer chlorine- and bromine-catalyzed reactions (that destroy ozone) take place. So in this case, our warming climate is a good thing.
However, the scientists from NASA and NOAA who conduct these measurements stress that the smaller ozone hole extent in 2016 and 2017 is due to natural variability and not a signal of rapid healing. And furthermore, the current ozone hole area is still much larger than it was when we first noticed it back in 1985 due to our spraying of CFCs into the atmosphere. It continues to be so large despite strict regulations on CFC emissions because levels of ozone-depleting substances remain high enough to produce significant ozone loss. I.e. they stay in the atmosphere for a long time.
Which is why it’s so important that NASA and NOAA keep monitoring what’s going on up there! Thanks, science!