Context

The annually occurring ozone hole over the Antarctic had rapidly grown from mid-August and peaked at around 24 million square kilometres — one of the largest so far — in early October 2020. 

About

What is Ozone hole?

• An ozone hole is the thinning of the ozone layer boosted in size by colder temperatures.
• As the temperature high up in the stratosphere starts to rise, ozone depletion slows, the polar vortex weakens and breaks down.
• By the end of December, ozone levels return to normal. This time around, however, the process took longer. 
• The formation of ozone hole in the Antarctic has been an annual occurrence and has been recorded for the last 40 years.
• Human-made chemicals migrate into the stratosphere and accumulate inside the polar vortex.
• It begins to shrink in size as warmer temperatures dominate

What led to the expansion?

• The expansion of the hole was driven by a strong, stable and cold polar vortex and very cold temperatures in the stratosphere.
• The same meteorological factors also contributed to the record 2020 Arctic ozone hole, which has also closed.