How do we know that the hole in the ozone layer hasnt always been there?

Question

Technology has only existed in modern times to study the ozone layer. How do we then know that 1. it hasnt always been there, and 2. how do we know it is growing?

Answer 1

We don't.

Answer 2

We have been watching it long enough to see that it is growing.

I think there always was a seasonal thinning of it(personal opinion), but like you say our measurements don't go back to the time when it never existed.

They do however go back to before it became a permanent feature instead of a purely seasonal one.

Answer 3

It comes and goes as the seasons change and at the angle of the solar winds . At the exact same time every year the beta particles are attracted to the north pole and make it negative. The alpha particles are attracted to the south pole and make it positive . The ozone layer is at the very edge of space and about all that can get that high is hydrogen as all the other gases are too heavy.

Answer 4

Well I have given this a little thought.

Warm air rises & the air cools as it rises & as it cools it gets heavier which causes it to fall back down over the cooler areas (The poles.)

Warmer air holds more of what ever, cooler air holds less  

The rising air forms clouds, which cause rain, which causes most of the stuff in the air to fall back down in rain.

So it would seem to me that it is just natural that the air falling down over the poles wouldn't  have as much ozone.