Hello I am presenting before you a presentation on ozone layer depletion which includes the mechanism of it and even the detailed information about how they occur.Hope it will be helpful to the students in understanding the ozone layer depletion. Thank You, Tirthankar Majumder MTech Dept. of earth and environmental science NIT- Durgapur

1. OZONE LAYER DEPLETION
BY :
TIRTHANKAR MAJUMDER
17ES4113
DEPARTMENT OF EARTH & ENVIRONMENTAL STUDIES,
NIT DURGAPUR

11. OBSERVATION
• Scientists did predict that ozone depletion should
peak around year 2010.
• As world-wide controls reduce the release of CFCs
and other ozone-eating substances, nature will repair
the ozone layer.
• By year 2065 stratospheric ozone should return to the
amount present in 1980.
• Until then, we can expect higher levels of UV
radiation at the Earth's surface.
• We need to take care to avoid the bad health effects
that could result from too much UV radiation.

15. `
The National Ozone Expedition was the first of these, occurring
just one year after the 1985 publication of the discovery of the
ozone hole by the British Antarctic Survey. First-time
measurements of key chlorine-containing and nitrogen
containing gases were made by members of the CSD's
Chemistry and Climate Processes program (formerly Middle
Atmosphere and Atmospheric Chemical Kinetics). NOZE I
Research Team Arrives in Antarctica. Researchers arrive in
Antarctica at noon, 23 August 1986, as part of the first National
Ozone Expedition (NOZE I) to study the phenomenon known as
the ozone hole
C A S E S T U D Y

16. . CSD scientist Dr. Susan Solomon led a
team of 16 scientists who made
measurements of trace gases and
physical properties of the atmosphere.
The data, along with additional findings
from the NOZE II mission the next year,
showed conclusively that human-
produced trace gases that contain
chlorine and bromine were causing the
ozone hole. Scientists from the National
Aeronautics and Space Administration
(NASA), NOAA, and other organizations
made the key measurements and
analyses that showed the
CFC/ozone/polar stratospheric cloud
theories of the ozone hole, and not
other theories, were consistent with the
observations.

17. 17
The Antarctic Ozone Hole
• The ozone hole is
defined as the area
having less than 220
dobson units (DU) of
ozone in the overhead
column (i.e., between
the ground and
space).

18. 18
http://www.cpc.ncep.noaa.gov/products/stratosphere/sbuv2to/ozone_hole_plot.gif

20. OZONE HOLE
• When was the ozone hole discovered?
The discovery of the annual depletion of ozone above the Antarctic was first announced in a paper
by Joe Farman, Brian Gardiner and Jonathan Shanklin which appeared in Nature in May 1985. Later,
NASA scientists re-analyzed their satellite data and found that the whole of the Antarctic was
affected.
• Why does the ozone hole form over Antarctica ?
• The answer is essentially 'because of the weather in the ozone layer'. In order for rapid ozone
destruction to happen, clouds (known as PSCs, Stratospheric Clouds Mother of Pearl or Nacreous
Clouds) have to form in the ozone layer. In these clouds surface chemistry takes place. This converts
chlorine or bromine (from CFCs and other ozone depleting chemicals) into an active form, so that
when there is sunlight, ozone is rapidly destroyed. Without the clouds, there is little or no ozone
destruction. Only during the Antarctic winter does the atmosphere get cold enough for these
clouds to form widely through the centre of the ozone layer. Elsewhere the atmosphere is just too
warm and no clouds form. The northern and southern hemispheres have different 'weather' in the
ozone layer, and the net result is that the temperature of the Arctic ozone layer during winter is
normally some ten degrees warmer than that of the Antarctic. This means that such clouds are rare,
but sometimes the 'weather' is colder than normal and they do form. Under these circumstances
significant ozone depletion can take place over the Arctic, but it is usually for a much shorter period
of time and covers a smaller area than in the Antarctic.

21. • Does the ozone hole affect the rest of the world?
At the moment, catastrophic ozone depletion is only seen in the
Antarctic during the spring, but surrounding areas experience
lowered ozone levels as the ozone hole decays at the end of the
spring. As the ozone hole rotates, it may extend over populated
areas for a short while when it is very elongated. For example it
covered the tip of South America and the Falkland Islands for over a
week in October 1994 (Fig. 12).
• Limited ozone depletion can occur above the Arctic, but at present
it is confined to parts of the region and only lasts for a few days at a
time. If CFC releases had continued at the high rates of the mid
1980s, a continental sized ozone hole might have appeared over the
Arctic. Elsewhere in the northern hemisphere, stratospheric ozone
amounts over temperate latitudes have fallen by 5 to 10% during
the winter.

23. Major Collaborative Efforts:
Some Examples Like the expeditions mentioned above, the stratospheric work of
CSD is often carried out in close collaboration with colleagues from other
institutions in the U.S. and abroad. As examples we describe two major
collaborative efforts:
• The STRAT program (Stratospheric Tracers of Atmospheric Transport) investigated
how gases and particles are transported in the stratosphere. This major field
campaign especially clarifies how gases and particles from the exhaust of potential
future fleets of supersonic airplanes would be distributed around the globe. The
findings are expected to increase the scientific understanding of how exhaust
products might influence the stratospheric ozone layer. During 1996, the NASA ER-
2 research plane carried several instruments for measuring gases, winds, and
temperature into the upper troposphere and lower stratosphere. Flights began in
1995 and were repeated on a regular basis through 1997 in a broad region from
the tropics to the middle latitudes of the Northern Hemisphere, allowing scientists
to study both the latitudinal and seasonal characteristics of the stratosphere.
Additional measurements were obtained from satellite instruments and from
instruments that were carried aloft by balloons in the summer of 1996. The project
involved an international team of researchers from NASA, NOAA ESRL, and several
universities and other organizations. STRAT is co-sponsored by NASA and NOAA.

24. • Fieldwork of the Photochemistry of Ozone Loss in the
Arctic Region in Summer (POLARIS) mission was
completed in 1997. This experiment was designed to
study ozone photochemistry in the summertime lower
stratosphere at middle and high latitudes, with the aim
of understanding the processes that cause ozone
column amounts to decline during the summer/early
fall period at northern high latitudes. Chemical and
meteorological data were obtained from instruments
aboard the NASA ER-2 high-altitude aircraft, other
aircraft, balloons, and satellites. The project involved
an international team of researchers from NASA, NOAA
ESRL, and several universities and other organizations.

25. Montreal Protocol
• The Montreal Protocol is an international agreement which was drawn up
in September 1987. It originally aimed to half the use of CFCs by 1999.
However, reviews of the protocol held in 1990 in London and 1992 in
Copenhagen imposed more stringent controls, so that all production of
CFCs, CCl4 and halons should cease by the year 2000. Many countries have
even agreed to stop using CFCs before this deadline. Production of other
ozone depleting gases is to stop in the early years of the 21st century.
Unfortunately the ozone hole will not immediately disappear as CFCs are
such stable gases that they will remain in the atmosphere for decades
after release.
• Independent reviews by panels of scientist (eg the UK Stratospheric Ozone
Review Group reports) present conclusive evidence that CFCs are still
increasing in the atmosphere and that chlorine from them is also
increasing and is responsible for ozone depletion. Thanks to the provisions
of the Montreal Protocol and its subsequent amendments the level of
ozone depleting gases in the atmosphere will start dropping by the end of
the 1990s.

26. Is the ozone hole recovering ?
• Some reports in the media suggest that the ozone layer over Antarctica is
now recovering. This message is a little confused. Recent measurements
at surface monitoring stations show that the loading of ozone destroying
chemicals at the surface has been dropping since about 1994 and is now
about 6% down on that peak. The stratosphere lags behind the surface by
several years and the loading of ozone depleting chemicals in the ozone
layer is at or near the peak. Satellite measurements show that the rate of
decline in ozone amount in the upper stratosphere is slowing, however
the total ozone amount is still declining. The small size of the 2002 ozone
hole was nothing to do with any reduction in ozone depleting chemicals
and it will be a decade or more before we can unambiguously say that the
ozone hole is recovering. This assumes that the decline in ozone depleting
chemicals continues and that there are no other perturbations to the
ozone layer, such as might be caused by a massive volcanic eruption or
Tunguska like event. It will be the middle of this century or beyond before
the ozone hole ceases to appear over Antarctica. What we saw in 2002 is
just one extreme in the natural range of variation in the polar stratosphere
and is the equivalent of an extreme in 'stratospheric weather'. By contrast
the 'weather' in 2003 moved to the opposite extreme and we saw one of
the largest ozone holes on record.

27. The effect of ozone depletion is
• the increased UV-B radiation reaching Earth’s surface.
• Effects on Humans
• Sunburn
•Sun-damaged skin
•Cataracts
•Snow blindness
•Skin cancer

28. • Reduced effectiveness of immune system
• Respiratory illness and heart problems
• Effects on the Environment
• Global warming
• Climate change
• Crop and forest damage
• Infections and skin diseases on animals
• Less ocean plankton
• Less fish harvest

30. 30
BIBLIOGRAPHY
• http://www.epa.gov/ozone/title6/phaseout/22phaseout.ht
ml
• http://epa.gov/sunwise1/kids/kids_ozone.html
• http://www.epa.gov/sunwise/doc/uvradiation.html
• http://en.wikipedia.org/wiki/Ozone_depletion
• http://www.windows2universe.org/earth/Atmosphere/laye
rs.htmlhttp://www.theozonehole.com/ozoneholehistory.ht
m