1. University of Salahaddin
Faculty of science
Department of Chemistry

2. THE OZONE LAYER
What is it?
Where is it?
Why is it important to life on Earth?
How are we as humans affecting it?

3. What is the ozone layer?What is the ozone layer?
The ozone layer is aThe ozone layer is a
layer of gas consistinglayer of gas consisting
of Oof O33 molecules, calledmolecules, called
ozone, that formsozone, that forms
when free Oxygenwhen free Oxygen
molecules bond to Omolecules bond to O22
molecules.molecules.

4. OzoneOzone
Ozone is a moleculeOzone is a molecule
consisting of oxygenconsisting of oxygen
atoms.atoms.
Ozone gas can beOzone gas can be
created or destroyedcreated or destroyed
by the sun’sby the sun’s
UltraViolet rays asUltraViolet rays as
shown in the pictureshown in the picture
to the right.to the right.

5. Where is the ozone layer?Where is the ozone layer?
The ozone layer is aThe ozone layer is a
protective layer of gasprotective layer of gas
molecules locatedmolecules located
within the stratosphere.within the stratosphere.
Ozone gas also existsOzone gas also exists
in the troposphere andin the troposphere and
at ground level, butat ground level, but
most is located withinmost is located within
the stratospheric layerthe stratospheric layer
shown to the right.shown to the right.

6. Earth’s AtmosphereEarth’s Atmosphere

7. Why is it important to life onWhy is it important to life on
Earth?Earth?
On a daily basis, the sun radiates its energy towardOn a daily basis, the sun radiates its energy toward
Earth. One form of this energy is UltraViolet radiation,Earth. One form of this energy is UltraViolet radiation,
also known as UV rays.also known as UV rays.
UV rays are relatively high energy waves that provideUV rays are relatively high energy waves that provide
Earth with the warmth it needs to support life as weEarth with the warmth it needs to support life as we
know it.know it.

8. Ultra-Violet RadiationUltra-Violet Radiation
UV rays penetrateUV rays penetrate
the Earth’sthe Earth’s
atmosphere at 3atmosphere at 3
slightly differentslightly different
wavelengths calledwavelengths called
UV-A, UV-B, andUV-A, UV-B, and
UV-C rays.UV-C rays.

9. So, why is the ozone layerSo, why is the ozone layer
important to life on Earth?important to life on Earth?
The stratospheric ozoneThe stratospheric ozone
layer completely stopslayer completely stops
the penetration of UV-Cthe penetration of UV-C
rays and eliminatesrays and eliminates
most of the UV-B rays.most of the UV-B rays.
Therefore, the ozoneTherefore, the ozone
layer protects life onlayer protects life on
Earth from the harmfulEarth from the harmful
effects of solar radiationeffects of solar radiation
on a daily basis.on a daily basis.

10. So what might life be like withoutSo what might life be like without
the ozone layer?the ozone layer?

11. How are we as humans affectingHow are we as humans affecting
the ozone layer?the ozone layer?
Since 1928, Chlorofluorocarbons have beenSince 1928, Chlorofluorocarbons have been
produced, originally as nonflammableproduced, originally as nonflammable
refrigerants for use in refrigerators, andrefrigerants for use in refrigerators, and
eventually for use in fire extinguishers, dryeventually for use in fire extinguishers, dry
cleaning agents, pesticides, degreasers,cleaning agents, pesticides, degreasers,
adhesives, and as propellants for aerosoladhesives, and as propellants for aerosol
products.products.
As these CFCs have been released into theAs these CFCs have been released into the
atmosphere, the level of ozone in theatmosphere, the level of ozone in the
stratosphere has decreased.stratosphere has decreased.
CFCs have an estimated lifespan of moreCFCs have an estimated lifespan of more
than 100 years.than 100 years.

12. CFCs and OzoneCFCs and Ozone

13. And the effects of all those CFCs...And the effects of all those CFCs...

14. So what about the hole in theSo what about the hole in the
ozone layer?ozone layer?
October 1979 October 2007

15. The Ozone HoleThe Ozone Hole
Since the 1970’s the ozone hole hasSince the 1970’s the ozone hole has
been increasing in size over thebeen increasing in size over the
Antarctic.Antarctic.
For the first time, in September of 2000,For the first time, in September of 2000,
the ozone hole became so large itthe ozone hole became so large it
actually left populated areas of southernactually left populated areas of southern
Chile fully exposed to the effects of theChile fully exposed to the effects of the
Sun’s UV rays.Sun’s UV rays.

16. Chile’s Ozone HoleChile’s Ozone Hole

17. How does ozone depletion affectHow does ozone depletion affect
global warming and ultimatelyglobal warming and ultimately
climate change?climate change?
As ozone levels in the stratosphere areAs ozone levels in the stratosphere are
depleted, more solar radiation penetrates thedepleted, more solar radiation penetrates the
Earth’s atmosphere.Earth’s atmosphere.
This affect results in an increase in solarThis affect results in an increase in solar
radiation reaching the Earth’s surface addingradiation reaching the Earth’s surface adding
to an increase in surface temperature.to an increase in surface temperature.
In turn, global warming actually results in aIn turn, global warming actually results in a
warming of the troposphere, but a cooling ofwarming of the troposphere, but a cooling of
the stratosphere, hindering the ozone layer’sthe stratosphere, hindering the ozone layer’s
natural chemistry for repairs.natural chemistry for repairs.

18. So what are we doing about it?So what are we doing about it?
After the discovery of ozone depletion in the late 1970’s, manyAfter the discovery of ozone depletion in the late 1970’s, many
countries agreed that something must be done worldwide tocountries agreed that something must be done worldwide to
stop the production of man-made, ozone harmful products.stop the production of man-made, ozone harmful products.
The international community adopted the Vienna Convention inThe international community adopted the Vienna Convention in
1985 followed by the Montreal Protocol in 1987.1985 followed by the Montreal Protocol in 1987.
The latest reports confirm that it has led to the phasing out ofThe latest reports confirm that it has led to the phasing out of
about 95% of the consumption of ozone-depleting substancesabout 95% of the consumption of ozone-depleting substances
(ODS) listed in the agreement. In turn, this has led to the(ODS) listed in the agreement. In turn, this has led to the
prospect of the ozone layer recovering by 2050 to 2075.prospect of the ozone layer recovering by 2050 to 2075.
Furthermore, the phasing out of ozone-depleting substancesFurthermore, the phasing out of ozone-depleting substances
has helped to fight climate change since many of thesehas helped to fight climate change since many of these
chemicals are also powerful greenhouse gases. According to achemicals are also powerful greenhouse gases. According to a
recent study, the phasing out of substances under the Protocolrecent study, the phasing out of substances under the Protocol
led to more reductions in greenhouse gases than what isled to more reductions in greenhouse gases than what is
foreseen under the Kyoto Protocol.foreseen under the Kyoto Protocol.

19. What can we do, as concernedWhat can we do, as concerned
citizens, to ensure that ourcitizens, to ensure that our
children have a viable planet tochildren have a viable planet to
inhabit?inhabit?