1.
Ozone depletion
by
Dr. Jeevan Jyoti, PhD
Asst. Professor,

2.
OZONE LAYER DEPLETION
• Why hole in the atmospheric ozone layer above us?
• What has been done about this?
• Why should we worry ourselves about the Ozone
Layer Depletion?
Mr. OZONE Will I be able to continue enjoying this
life without problems?

3.
History of the Ozone Discovery
• Dramatic loss of ozone (in stratosphere) over
Antarctica was first noticed in the 1970s by a
research group from the British Antarctic Survey
(BAS) who were monitoring the atmosphere
above Antarctica.
• When the measurements were taken in 1985, the
drop in ozone levels in the stratosphere was so
dramatic that at first the scientists thought their
instruments were faulty.
• Replacement instruments were built and flown
out, and it confirmed the earlier measurements,
several months later, that the ozone depletion
observed was accepted as genuine.

4.
What is ozone?
• Ozone (O3 : 3 oxygen
atoms) occurs naturally
in the atmosphere.
• Ozone forms a layer in
the stratosphere,
thinnest in the tropics
(around the equator) and
denser towards the poles
• measured in Dobson
units (DU)

5.
What is a Dobson unit?
• 1 Dobson Unit (DU) is
defined to be 0.01 mm
thickness at STP - (0C
and 1 atm press).
• The unit is named after
G.M.B. Dobson, one of
the first scientists to
investigate atmospheric
ozone.
• He designed the 'Dobson
Spectrometer'

6.
How is ozone formed?
UV radiation strikes the O2 molecule and
splits it, atomic oxygen associates itself with
another O2 molecule.
Ozone (O3) is a highly-reactive form of
oxygen.

7.
• Unlike oxygen (O2), ozone has a strong
scent and is blue in color.
• Ozone exists within both the
tropospheric and stratospheric zones
of the Earth’s atmosphere
• In the troposphere, ground level ozone
is a major air pollutant and primary
constituent of photochemical smog.
• In the stratosphere, the ozone layer is
an essential protector of life on earth as
it absorbs harmful UV radiation before it
reaches the earth.

8.
Where is ozone the “good guy”?
trophosphere
stratosphere

9.
Where is ozone the “bad guy”?
trophosphere
stratosphere

10.
CFC’s and ozone depletion
• Chlorofluorocarbons are
used in refrigerators and air
conditioners.
• These chlorofluorocarbons
are not harmful to humans
and have been a benefit to us.
• Once released into the
atmosphere, CFC are
bombarded and destroyed
by ultraviolet rays.
• In the process chlorine is
released to destroy the
ozone molecules.

11.
Destruction of ozone by chlorine
• Molecular oxygen is broken down in the stratosphere
by solar radiation to yield atomic oxygen, which then
combines with molecular oxygen to produce ozone.
• The ozone is then destroyed by chlorine atoms.

12.
The ozone depletion process

13.
Responsibility for ozone damage each
year

14.
Effects of UV rays on Aquatic Ecosystems
Ozone depletion causes increases in UV ray’s
effects on aquatic ecosystems by:
1. decreasing the abundance of
phytoplankton – affects the food stock for
fishes and the absorption of CO2
2. decreasing the diversity of aquatic
organisms – reduces food stock and also
destroys several fish and amphibians.

15.
Effects of UV rays on Terrestrial Ecosystems
• Damage to plant cell DNA molecules -
makes plants more susceptible to pathogens
and pests
• Reductions in photosynthetic capacity in
the plant - results in slower growth and
smaller leaves
• Causes mutations in mammalian cells and
destroys membranes

16.
Harmful effects of UV rays on
people
• Skin cancer
• Premature aging (photoaging) of the
skin.
• Cataracts and eye disorders (corneal
sunburn and blindness)

17.
Global warming
Will Human-Induced Climate Change
Destroy the World?

18.
Introduction
• Is the world getting warmer?
• If so, are the actions of mankind to
blame for earth’s temperature
increases?
• What can/should be done about these
issues?

19.
Sun
Earth’s Temperature
Solar
Energy
Solar
Energy

20.
Sun
Earth’s Temperature
Solar
Energy
Radiative
Cooling

21.
Sun
Earth’s Temperature
Solar
Energy
Radiative
Cooling

22.
Sun
Earth’s Temperature
Solar
Energy
Radiative
Cooling

23.
“Hockey Stick” Controversy
1000 1200 1400 1600 1800 2000
-0.8
Year
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
Temperature
Change
(°C)
Direct temperature measurements
Michael Mann et al. 1999
The graph is basically flat, other than the rapid increase of temp.
during the 20th century. The study received wide acclaim, especially
after publication by the IPCC (Intergovernmental Panel on Climate
Change) and is now referred to as the “Hockey Stick Graph”.

24.
Ice Sheets Melting?
• GRACE (an NGO) found melting of Antarctica
equivalent to sea level rise of 0.4 mm/year (2
in/century)
• 2005 (by satellite radar pictures)
–confirmed Antarctica melting

25.
How Much Temperature Increase?
• Some models propose up to 9°C increase this
century
• Two studies put the minimum at 1.5°C and
maximum at 4.5°C or 6.2°C
• Another study puts the minimum at 2.5°C

26.
Melting Glaciers – Mt. Kilimanjaro

27.
Ganga under threat fromwarming
• Himalayan source of the Ganga is drying up
at a rate of 40 yards a year, nearly twice as
fast as two decades ago, and that some of
these glaciers might disappear by 2030.
• In the dry summer months, the Gangotri glacier
provides up to 70 % of the water of the Ganga.
• According to a UN climate report, the
shrinking glaciers also threaten Asia’s
supply of fresh water.

28.
Source: New Indian Express

29.
Other ecological effects
• The Common Murre has advanced
breeding by 24 days per decade
over the past 50 years in response to
higher temperatures.

30.
• The Baltimore oriole is shifting
northward and may soon disappear
entirely from the Baltimore area.

31.
• Polar bear populations are coming
under threat as food becomes harder to
hunt.
–Require pack ice to live
–Might eventually go extinct.

32.
Sea turtles
–Breed on the same islands as their birth
–Could go extinct on some islands as
beaches are flooded

33.
Drought in Africa
Lake Faguibine Lake Chad

34.
Portage Glacier
1914 2004
• Alaska
Photos: NOAA Photo Collection and Gary Braasch – WorldViewOfGlobalWarming.org

35.
Colorado River
• Arizona
June 2002 Dec 2003

36.
We can stop global warming!

37.
Mitigation of Global Warming
• Conservation
– Reduce energy needs
– Recycling
– Reuse
• Alternate energy sources
– Nuclear
– Wind
– Geothermal
– Hydroelectric
– Solar
– Fusion?