Now that we've stopped using ozone-depleting chemicals, has the ozone layer improved?
First, let's explain that although ozone is bad stuff to breathe here at or near sea level, it provides a very important protective role in the upper atmosphere, typically between six and thirty miles above the earth. It blocks much of the incoming ultraviolet radiation from the sun, which has many harmful effects; those include causing skin cancer and cataracts.
A class of chemicals (typically refrigerants and propellants) that contain the element Chlorine doesn't tend to react, but when it reaches the upper atmosphere and is exposed to sunlight, it destroys ozone. That creates a thinning or "hole" of sorts in the protective ozone layer. The development of the "hole" was dramatic...enough that the developed nations of the world (and some others) agreed to stop using this class of chemicals, known as CFC's, or Chloro-fluorocarbons, with the final agreement signed in the 1990's. Of course, these CFC's didn't just vanish overnight from the upper atmosphere. But first the rate of increase slowed, and now scientists actually report signs the ozone layer is recovering. At the rate we're observing, it's likely to be back to its normal state fifty years from now.
