When was the first thinning of the ozone layer?

Answer 1

There is evidence that large portions of the ozone layer have disappeared a few times in the past, even back before Mankind or the Industrial Revolution. So there is no way to know when was "first".

Thankfully, the Sun rapidly restores some ozone gradually.

The ozone layer has always become thinner during each poles winter months due to a lack of sunlight. No thinning occurs over populated areas. This is reserves to only areas that have long periods of darkness, like out poles during their winters.

Answer 2

Chemicals like chlorine in chlorofluorocarbons (CFCs) and other halons released by aerosols and refrigeration during the 20th Century destroyed ozone in the ozone layer.

An international treaty, the Montreal Protocol, phased out the use of these gases, though they can remain in the atmosphere for up to 70 years. Scientists hope that the ozone layer will have repaired itself by 2060.

Answer 3

Scientists discovered the first thinning of the ozone layer in the late 1970s over Antarctica, which led to the realization of the ozone hole in the early 1980s. This thinning was primarily caused by the release of chlorofluorocarbons (CFCs) and other ozone-depleting substances into the atmosphere.