South Pole July-December ozone monitoring data from 2011 (left) and 2012. Image: KNMI
Wonderful news from the European Space Agency's atmospheric monitors: the hole the ozone layer above Antarctica has hit a ten-year low, and it's still shrinking. That means the environmental worry that caused your mom to slather you with sunblock as a kid is now showing positive effects from bans on ozone-killing chlorofluorocarbons in the late 80s.
As you've surely heard at some point in your life, CFCs were once prevalent as propellants for hair spray and such, and they (along with halons) also have an affinity for breaking up the 03 ozone molecules that absorb and reflect UV rays in our atmosphere. Aside from their ozone-killing nature, the big problem with CFCs is that they persist in the atmosphere for a really long time. So despite being fairly solidly banned across the world, chlorine content in the atmosphere isn't expect to return to pre-CFC levels until the middle of this century.
That also explains why it's taking so long for the ozone layer to heal. The ESA's ozone climate change initiative (CCI) released its newest report (PDF) this month, which shows the results of its satellite monitoring of the Antarctic atmosphere. The atmosphere is fluid, which means there are changes to the ozone hole from year to year. But on top of showing a ten-year low, the results also suggest that the ozone hole is indeed shrinking.
As you can see in the above illustration of data from a trio of ESA satellites, the hole (in blue) has neared the size it hit in 2002. But as you might fairly assume by looking at 2003, a low year doesn't mean that the ozone layer is static at that point. So while 2012 was a banner year, data at the end of 2013 might not be so positive.
That's where the ESA's ozone trends come in to play. The graph at left shows that total ozone over Antarctica has climbed steadily upward after hitting a low in the late 90s. Considering the lag time between the end of CFC use and its dissipation from the atmosphere, this is positive data that suggests the ozone will indeed be able to heal itself.
We'll see what happens in the coming years–weather conditions helped 2007 show a record loss of ozone over the Arctic, for example–but for now it's good to see that environmental policies have actually worked.
Of course, as compared to something like climate change, fixing the ozone layer was a relatively easy fix; no one wants more sunburns, and the cause was fairly easy to pinpoint and eliminate. Still, it's heartening to see that, if we stop messing with it, the atmosphere can start to return to equilibrium. That's important to keep in mind as we continue to struggle to deal with climate change.