Why we are still monitoring the ozone hole

Almost 40 years on from the first reports of the Antarctic ozone hole, and 35 years since the Montreal Protocol to ban CFCs came into effect, what’s going on with the ozone hole? How does it form? How do we measure it? And having solved the CFC problem, why are we still monitoring ozone so closely? Claire Concannon heads to NIWA's Atmospheric Research Station in Lauder, Central Otago, to find out.