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Comment by caf | Hacker News Reader

CFCs don't concentrate at the poles.

The reason they have the strongest effect there, and not locally where they're produced or globally in the stratosphere, is because the stratosphere is very dry and only in the extreme cold of a polar winter can stratospheric clouds form. The particles in these clouds catalyse the reactions that allow a each free chlorine molecule to destroy many ozone molecules.

That's also why the hole is worse in the Antarctic. It is colder and has more polar stratospheric clouds.

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(thanks for posting)

... which anyone could have easily read up on, but some people are interested in stirring up trouble not about learning.

I'm glad RobertRoberts asked those questions here. Some people have answered in useful educational ways and I've learned. Taken to its logical conclusion "just Google it" more or less means comment threads and places like HN may as well not exist.

Also personally I don't see strong evidence that the questions were asked to stir up trouble and not to learn. People have quite a wide range of ways of using language and expressing themselves, and I know myself that when I'm talking to someone who probably knows more about me than a certain subject, and that my assumptions are probably on shaky ground, I'll still voice my arguments against what they're saying because they will be able to quash them. Otherwise those same arguments will probably drift back into my head later on and make me start doubting again. I've tended to find that the minds I enjoy interacting with the most have been ok with this as they want to share and test their knowledge.

He didn't ask to learn but to stirr up like in "commenting on every comment here with my contrary views"

That seems like a valid explanation for the "start" of a hole if there was a continuous stream of _only_ CFCs and chlorine.

Doesn't the ozone gas itself get blown around in the wind also? Wouldn't this mean that ozone would eventually fill the hole back up unless there was a steady stream of CFCs/chlorine to that one spot?

CFCs effectively function as a catalyzer and aren't consumed by the process, hence the hole is more of a Ozone sink. Wikipedia explains the effect of large-scale transport in the stratosphere well: https://en.wikipedia.org/wiki/Ozone_layer

During the polar winter, when the necessary polar stratospheric clouds can form for ozone depletion to occur, the polar vortex also strengthens which tends to isolate the polar stratosphere. During the summer, the vortex weakens, mixing occurs and the ozone depletion over the pole is reduced (the "ozone hole" is seasonal). In fact, as this occurs in the southern spring, areas of ozone-depleted stratosphere drift over inhabited lands to the north.

More CFCs also enter the polar stratosphere through this mixing, though, ready to start the cycle again next polar winter.

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