Only during the last decade of the twentieth century did the Arctic began to experience an ozone hole and formation of polar stratospheric clouds, and the hole expanded in a regular way after it appeared

Question

What does this indicate about Arctic stratospheric temperatures during this period? Explain.

Answer 1

As a result of detailed study of the mechanisms of ozone depletion, we know that
the temperature has a lot to do with what happens. The temperature near the poles is very
low. That is really all that we can know based on this particular observation. We can know
that because we know that low temperatures are essential for the ozone-depleting reactions
to occur. But other conditions must be met as well.
Does the expanded ozone hole mean that the temperature must have gotten lower? Not
necessarily. The concentration of ozone-depleting gases may have changed.
Is the temperature on this basis then known not to be lower than in previous times? This is
not knowable on the basis of this observation alone; it may or may not have happened (see
the preceding paragraph).
Can we be sure the concentration of ozone-depleting gases has changed? Certainly not on
the basis of this observation alone; the temperature or some other condition could have
changed. This is the reason that we can conclude only that the temperature must have been
low enough for the requisite chemical reactions to occur.