Aveneu Park, Starling, Australia

1. light, therefore acting as a shield protecting us

1.    CFCs (Chlorofluorocarbons) are compounds which are made up of a
group of chemicals which are chlorine, fluorine, and carbon (they’re all in the
name). CFCs used to be popular chemicals because they are an organic compound
that is not only non-toxic, and also non-flammable. They were mostly used in
air conditioners, refrigerators and also aerosol cans. However, they have not
been used since around 1996 as CFCs were identified as the predominant cause of
ozone depletion.

2.    Ozone is a gas that is made up of oxygen molecules (O3). It is located in a small
section of the atmosphere, the stratosphere, which is just above the
troposphere, see figure one. The stratosphere is approx. sixteen to fifty km
above earth. It is called the Ozone layer as occurs because of the  high
concentration of ozone. This absorbs the majority of the sun’s harmful
ultraviolet light, therefore acting as a shield protecting us from the harsh
rays of the sun. The ozone in the stratosphere is created naturally from
chemical reactions including oxygen molecules and UV sun radiation..  One
CFC molecule can destroy 100 000 ozone molecules, which means that (because of
past damage), unfortunately, the ozone layer won’t be repaired until 2050 (although
we have stopped using them) because CFCs have a long lifetime ranging from 20
up to 100 years (just to clarify CFCs do not fall down to earth in the rain, so
they remain damaging the stratosphere). Most stratospheric ozone depletion is
caused when chlorine or bromine reacts with the ozone. 84% of chlorine entering
the stratosphere is manmade and 16% are from natural effects, such as oceans
and volcanoes.

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3.    It was 1970 when scientists began to realize that there could be
an issue of ozone depletion, but it wasn’t until 1984/1985 when three
scientists,   Joe Farman, Jonathan Shanklin and Brian Gardiner,
discovered a large hole in the ozone layer above Antarctica and announced it to
the public. The ozone above Antarctica is the weakest because the cold
temperatures over this land converts the CFCs to chlorine more rapidly therefore
penetrating the ozone layer. See figure two. In the southern spring and
summer while the sun is shining all day, it causes the chlorine and UV rays to
destroy the ozone, damaging approx. 65%. There is a significant difference
between the deterioration of the ozone of Antarctica and most other places
which have a 20% deterioration rate.

4.    The ozone layer being destroyed has many consequences, for example
it results in higher UV reaching earth leading to a higher chance in humans
getting skin damage from the sun, and there is also a higher chance to have
skin cancer (this means that the more ozone layer that is destroyed and
weakened, the more likely these consequences are to happen), keeping in mind
that not only does this affect humans, but unfortunately also harms animals. On
a less threatening note, UV rays are also bad for humans’ eyes.

5.    CFCs chemicals mostly appearing in aerosol spray cans are the main
reason for the hole in the ozone layer. When CFCs rise to the stratosphere, the
UV (ultraviolet) rays break them down. The chlorine that has been released
reacts with the oxygen causing the destruction of the ozone molecules. This was
first reported by Mario Molina in 1974. Although in 1973, was when he began his
work with F. Sherwood at the University of California. Before this, it had been
assumed that CFCs didn’t react with common chemicals, so that means that they
were safe for the environment. However, his research showed that CFCs remained
in the atmosphere for a long time — between 40 and 150 years and would then
drift high enough that solar radiation could split off a chlorine atom from the
CFC molecule. The chlorine atom would then react with ozone, destroying the
ozone molecule and depleting the ozone layer.

6.    In 1996, when CFCs were banned, they came up with a replacement,
which were called HCFCs (Chlorodifluoromethane).
These were better than CFCs because not only are HFCs often broken down in the
troposphere instead of harming the ozone layer in the stratosphere, but also
because they had a shorter lifespan of approx. 12 – 14 years instead of
destroying the ozone layer for anywhere up to 100 years like CFCs. HCFCs were
viewed as only temporary (because they were still damaging the ozone layer). So
that’s when an even better alternative; HFCs (hydrofluorocarbons) was used because unlike the HCFCs, they didn’t have any chlorine
to react with the ozone.

7.    Since CFCs were banned in 1996, the hole in the ozone layer has stopped
expanding for the first time in 35 years. In ten years to come, the hole in
the ozone layer will begin to shrink, and another thirty five years after that
the ozone layer will return to a healthy state which was last seen in 1980. See
figure 3 for an example of The Change in the Ozone Layer From 1979 (to 1989
to 2006) to 2010 over Antarctica. To quote  http://www.clo.nl/en/indicators/en0218-ozone-layer, “the increase in greenhouse gases in the atmosphere causes
cooling of the stratosphere and could affect recovery of the ozone.” Then
leading on to say; that it is unknown whether the effect will be positive or
negative.

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