We will have to continue to monitor ozone levels for years to come before we can be confident.

We can't really expect much of an improvement in the UV levels reaching the biosphere until we can detect an increase in total column ozone.

We should expect to be able to detect recovery in most regions of the world within the next 15 to 45 years. That's based on full compliance with the Montreal Protocol and its amendments and no other complicating factors such as major volcanic eruptions or enhanced stratospheric cooling.

The reason why total column ozone is so important is because it's the single significant factor that determines how much UV radiation gets through the atmosphere, meaning it's the most important factor for humans and the environment.

Depletion has occurred mainly over the last two decades.

We will absolutely have to monitor for at least another decade before we can be confident.