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have you ever heard that something

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called the ozone layer is thinning or

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that your aerosol hairspray is what's

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causing it or that it leads to more

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severe sunburns and uv rays this is

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referring to the ozone hole but what

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exactly does it all mean

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the ozone hull's proper name is actually

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the antarctic ozone hole because when it

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forms it forms over antarctica

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but before we get into what that is

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let's first talk about what ozone itself

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is

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atoms about 90 of the earth's ozone

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exists in the stratosphere the layer of

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the atmosphere that extends from 8 to

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about 30 miles above the earth's surface

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in fact the stratosphere is often

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referred to as the ozone layer ozone

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acts as a sunscreen around the earth

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filtering out harmful ultraviolet

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radiation or uv rays which are mainly

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absorbed in the stratosphere

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without an ozone layer uv radiation

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would sterilize the earth with a damaged

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but still present ozone layer there

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would be more sunburns more skin cancer

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cases increased cases of eye damage the

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wilting and loss of trees and plants and

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significantly lessened crop yields

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suffice it to say ozone is pretty

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important for the planet so what causes

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the ozone hole

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there are several major factors that

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together lead to the destruction of

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ozone thus creating the ozone hole those

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factors are

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one very strong winds around the south

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pole or the polar vortex

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two the sun's rays three chlorine and

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bromine compounds from ozone-depleting

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substances

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and four

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cold temperatures below negative 109

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degrees fahrenheit in the stratosphere

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which form a specific kind of cloud

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polar stratospheric clouds

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the polar vortex forms in the southern

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hemisphere stratosphere during the

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winter as temperatures drop and when

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sunlight returns to antarctica in late

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winter and early spring temperatures are

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still cold enough to form polar

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stratospheric clouds and now there's

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also sunlight

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chemical reactions take place on the

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cloud particle surfaces converting

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unreactive forms of chlorine and bromine

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into reactive chemicals

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the vortex acts as a sort of container

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confining the contents of the antarctic

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stratosphere within its bounds allowing

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the reactive chlorine and bromine

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compounds to destroy ozone molecules

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that's when depletion can occur on a

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large scale

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with the presence of sunlight the

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reactive chlorine and bromine compounds

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produced during winter begin to deplete

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ozone molecules by stealing one of their

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oxygen atoms leaving just oxygen gas or

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o2 in its wake

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as long as the polar stratosphere clouds

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are present these reactions will occur

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over and over again until the ozone is

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nearly gone this forms what we call the

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ozone hole but that's really a misnomer

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it's actually more of a thinned layer

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in mid to late spring the vortex begins

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to break up and the polar air depleted

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of ozone is mixed back into the rest of

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the southern hemisphere

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the ozone hole is gone

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ozone depletion has still occurred it's

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just no longer all concentrated in one

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small area it's spread around the

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atmosphere

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so why is the ozone hole bigger and

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longer lasting in certain years

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well it all comes down to weather just

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like some winters are colder and longer

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than others on the earth's surface the

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same goes for weather in the

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stratosphere

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the polar vortex and the ozone hole

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within it will persist

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and in years with cold springtime

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temperatures the polar vortex and the

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ozone hole are large

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make no mistake ozone depletion is not a

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natural thing it stems from human

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emissions of chemicals called

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chlorofluorocarbons

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or cfcs

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in the early 1900s refrigerators used

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toxic gases like ammonia and methyl

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chloride as refrigerants unfortunately

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this led to fatalities as the toxic

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gases leaked out of the appliances

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so the search began for a non-toxic and

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non-flammable chemical that could be

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used as a refrigerant thus the cfc was

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born there are many types of cfcs but

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the two most common are cfc11 and cfc12

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in the 1930s the production and

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consumption of cfcs began to skyrocket

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by the early 1980s over 300 million

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pounds of cfc-11 alone were being

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released into the atmosphere each year

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then in 1985 british researcher joe

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farman and his colleagues published

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their research on large seasonal ozone

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losses over antarctica

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thanks to the combined efforts of the

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quick acting science community industry

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and policy makers the montreal protocol

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was signed in 1987 restricting the

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production and consumption of cfcs every

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nation on earth has now signed the

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montreal protocol

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so for the record your hairspray and

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aerosol deodorant hasn't been harming

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ozone since these laws went into effect

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in the 80s

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but why do we still see an ozone hole

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today

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first cfcs have lifetimes of 50 to 100

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plus years and it will take some time

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for the concentration of cfcs in the

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atmosphere to drastically decline

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second there are still cfcs being

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released into the atmosphere today

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for example as an old refrigerator or

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air conditioning unit deteriorates in a

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landfill the cfcs within are slowly

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released

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air it takes about five years for its

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impact to be felt over antarctica where

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depletion will occur

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the cfc's emitted at the surface

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eventually rise into the tropical

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stratosphere

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most of the sun's uv radiation

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so the cfcs have to rise above most of

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the ozone layer before sunlight can then

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break them down

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once they get high enough solar

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radiation releases the chlorine most of

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which eventually goes into ozone safe

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forms like hydrochloric acid and

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chlorine nitrate

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when these compounds make their way to

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antarctica those chemical reactions

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start up

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and if you're wondering why antarctica

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these reactions are unique to the polar

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regions because of their extreme low

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temperatures and presence of polar

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stratospheric clouds

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one chlorine atom can destroy thousands

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of ozone molecules and millions of tons

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of cfcs were pumped into the atmosphere

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from the 1920s through the early 1990s

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as cfc concentrations in the atmosphere

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continue to decline the ozone hole is

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expected to gradually become less severe

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and scientists expect the antarctic

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ozone to recover back to healthy levels