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on september 20th the antarctic ozone

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hole reached an extent of 24.8 million

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square kilometers

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2020 was the 12th largest hole on record

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in 2019 the peak extent was the second

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smallest hole on record but this dark

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contrast doesn't mean the hole is

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worsening

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that's where weather patterns come in

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colder temperatures are one of the

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factors that activate ozone depletion

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which means that weather patterns play a

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vital role in determining the ozone

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hole's extent each year

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the antarctic ozone hole peaks during

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the southern hemisphere's late winter

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when temperatures are at a low and the

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sun's rays return

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the 2020 ozone hole was exceptionally

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large due to a stable and cold antarctic

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vortex the stratospheric low pressure

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system that flows clockwise in the

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atmosphere above antarctica

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it's there that the colder conditions

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help support formation of polar

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stratosphere clouds whose cloud

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particles activate ozone layer

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destroying forms of chlorine and bromine

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compounds

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production and used to be found in

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things like aerosol sprays and

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refrigerants

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unfortunately it took years to realize

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if chemically active forms of chlorine

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and bromine are present and there are

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both cold enough temperatures and sun

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rays a reaction occurs on the surfaces

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of cloud particles that form in cold

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stratospheric layers leading ultimately

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to runaway reactions that destroy ozone

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molecules

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the antarctic ozone hole was first

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discovered by researchers at the british

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antarctic survey in 1985.

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just a few years later in 1987 the

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international community signed the

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montreal protocol on substances that

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deplete the ozone layer

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countries as small as the vatican and as

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far as north korea signed the deal

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regulating the consumption and

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production of ozone-depleting compounds

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since 2000 human-made ozone-depleting

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substances have slowly declined but

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remain high enough to produce

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significant ozone loss

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these compounds have lifetimes of more

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than 50 years which is why we're still

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seeing their effects on the environment

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today

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the ozone hole over antarctica is

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expected to gradually become less severe

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as chlorofluorocarbons continue to

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decline

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and because of scientifically supported

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international action scientists expect

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the antarctic ozone to recover back to