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

The science behind ozone depletion Ozone depletion occurs when chlorofluorocarbons (CFCs) and halons (gases formerly found in aerosol spray cans and refrigerants) are released into the atmosphere. Ozone sits in the upper atmosphere and absorbs ultraviolet radiaton, another type of solar energy that's harmful to humans, animals and plants. CFCs and halons cause chemical reactions that break down ozone molecules, reducing ozone's ultraviolet radiation-absorbing capacity.

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.