the ozone layer deplation in the atmosphere

8/14/2019 The Ozone Layer Deplation in the Atmosphere

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The ozone layer deplationin the atmosphere -

- man made, or due to shiftin suns radiation ?


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Ozone layer and its depletion

Introduction

The Montreal Protocol on Substances That Deplete the Ozone Layer(a protocol to the Vienna Convention for the Protection of the Ozone Layer) is aninternational treaty designed to protect the ozone layer by phasing out theproduction of a number of substances believed to be responsible for ozonedepletion. The treaty was opened for signature on September 16, 1987, andentered into force on January 1, 1989, followed by a first meeting in Helsinki,May 1989.Since then, it has undergone seven revisions, in 1990 (London), 1991 (Nairobi),

1992 (Copenhagen), 1993 (Bangkok), 1995 (Vienna), 1997 (Montreal), and 1999(Beijing). It is believed that if the international agreement is adhered to, theozone layer is expected to recover by 2050 to its widespread adoption andimplementation it has been hailed as an example of exceptional international co-operation with Kofi Annan quoted as saying that "perhaps the single mostsuccessful international agreement to date has been the Montreal Protocol" (1)

The main purpose with The Montreal Protocolhas been to stop all addition ofsubstances in the atmosphere that could be suspected to deplete the protectinglayer of ozone in our atmosphere. (1)This ozone layer protects us against the dangerous, ultraviolet radiation in the

sunlight. The work with this project goes continuously on, and a long list ofsuspected chemicals, such as hydrochloro- fluorocarbons, refrigerants, foammanufactures, spray boxes, Freon chemicals and others has been stopped fortheir intended use.

What is ozone layer depletion ? (4)

The ozone layer, situated in the stratosphere about15 to 30 km above the earths surface, plays theimportant role of space suit that protects us living

beings by absorbing harmful ultraviolet radiationfrom the sun. The ozone layer is currently beingdestroyed by CFCs and other substances. Itsdepletion progress globally except in the tropicalzones.Destruction of the ozone layer increases theamount of harmful ultraviolet radiation (UVR) whichin turn can result in increased cases of skin cancer,and visual impediments such as cataract. It canalso hinder the growth of plants and negativelyimpact small living organisms, such as zooplankton,

phytoplankton, shrimp larvae and young fish.
http://en.wikipedia.org/wiki/Vienna_Convention_for_the_Protection_of_the_Ozone_Layerhttp://en.wikipedia.org/wiki/Treatyhttp://en.wikipedia.org/wiki/Ozone_layerhttp://en.wikipedia.org/wiki/Ozone_depletionhttp://en.wikipedia.org/wiki/Ozone_depletionhttp://en.wikipedia.org/wiki/Helsinkihttp://en.wikipedia.org/wiki/Londonhttp://en.wikipedia.org/wiki/Nairobihttp://en.wikipedia.org/wiki/Copenhagenhttp://en.wikipedia.org/wiki/Bangkokhttp://en.wikipedia.org/wiki/Viennahttp://en.wikipedia.org/wiki/Montrealhttp://en.wikipedia.org/wiki/Beijinghttp://en.wikipedia.org/wiki/Kofi_Annanhttp://en.wikipedia.org/wiki/Vienna_Convention_for_the_Protection_of_the_Ozone_Layerhttp://en.wikipedia.org/wiki/Treatyhttp://en.wikipedia.org/wiki/Ozone_layerhttp://en.wikipedia.org/wiki/Ozone_depletionhttp://en.wikipedia.org/wiki/Ozone_depletionhttp://en.wikipedia.org/wiki/Helsinkihttp://en.wikipedia.org/wiki/Londonhttp://en.wikipedia.org/wiki/Nairobihttp://en.wikipedia.org/wiki/Copenhagenhttp://en.wikipedia.org/wiki/Bangkokhttp://en.wikipedia.org/wiki/Viennahttp://en.wikipedia.org/wiki/Montrealhttp://en.wikipedia.org/wiki/Beijinghttp://en.wikipedia.org/wiki/Kofi_Annan


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The ozone layer is disappearing at particular high rate in high-latitude areas. Theozone layer resides in the stratosphere and surrounds the entire Earth. UV_Bradiation 280-315 nanometer (nm) wavelength from the Sun is particullaryabsorbed in this layer. As a result, the amount of UV-B reaching earths surface

is greatly reduced. UV-A

(315 400 nm) and othersolar radiation are notstrongly absorbed by theozone layer. Humanexposure to UV-B increasesthe risk of skin cancer,caracts, and a suppressedimmune systems. UV-B canalso damage terrestrialplant life, single cellorganism and aquatic

ecosystems. (5)

Ozone layer destruction by CFCs

Since CFC (chloro fluoro carbon) are chemically stable, when released into theatmosphere they pass through the troposphere at about 20 km altitude withoutdecomposing, reaching the stratosphere, where they are chemically decomposed

by short-wavelength ultraviolet rays, releasing chlorine atoms . In a chainreaction, the chlorine atoms destroy the ozone layer in the stratosphere. (4)


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The dynamic in the stratosphere

The process in the stratosphere goes very slowly, compared with what happensin the troposphere. The stratosphere is extremely stable, and air exchange withthe troposphere is very small. Immediately, this exchange is of great importance

for the climate.Exchanges of air between stratosphere and troposphere take mostly place overthe tropic areas, and are weakest over the Arctic and Antarctic zones. Thevertical exchange of air in the troposphere takes from hours to days, while ittakes months to years in the stratosphere to stabilize the conditions.The small exchange between stratosphere and troposphere is an importantreason for the movement of ozone from stratosphere to troposphere. This ozonestarts the formation of hydroxyl-radicals (OH), leading to the cycle starting thedecomposing and depletion of ozone in the troposphere.

The Ozone Hole (5)

For nearly a billipon years, ozonemolecules in the atmosphere

have protected life on Earth fromthe effects of ultraviolet rays.Only 10 or less of every millionmolecules of air are ozone.

In the Antarctic, a large ozonehole has been observed for eightconsecutive years from 1989 to1996.Each spring in the stratospheres

over Antarctica (spring in the southern hemisphereis from September throughNovember), atmospheric ozone is rapidly destroyed by chemical processes.As winter arrives, a vortex of winds develops around the pole and isolates thepolar surface. When temperatures drop below 78 C , thin clouds form of ice.nitric acid and sulphuric acid mixtures. Chmical reactions on the surface of icecrystals in the clouds release avtive forms of CFCs (Chloro Fluoro Carbons). Ozonedepletion begins, and the ozone hole apperars.


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Decrease of global ozone (5)

Spesific observations show a decrease in global values over more than twodecades. The graph above compares global ozone values with the averages fromthe period 1964 to 1980. The decrease worsened during the few years whenvolcanic aerosol from the Mt.Pinatubo eruption in 1991.

Does it really help?

The effect of reduced amount of dangerous chemicals to the atmosphere hasgiven some different effect, but in general the level of ozone-depleting gases hascome down.

In a NASA report from 2001 they declared that the ozone thinning over Antarctichad remained at the same thickness for the previous three years, but in 2003 theozone hole grew to its second largest size.

A more recent (2006) scientific evaluation animated the Montreal Protocol toannounce: there is a clear evidence of a decrease in the atmospheric burden ofozone-depleting substances, and some early signs of stratospheric ozonerecovery

What about the sun?

Creation of short-term ozone molecules in earths upper stratosphere takesplace, due to a photochemical process powered by the ultraviolet radiation fromthe sun.


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Ozone is created when ultraviolet light of wavelength less than 240 nm strikesatmospheric oxygen molecules, splitting them in two oxygen atoms. Theprocess is known as photodissociation or photolysis. Creation of stable ozonegoes over a three steps reaction.

The output of solar ultraviolet radiation is influenced by magnetically activeregions on the sun. These occur sporadically in sunspots, which are coolerregions on the sun and follows the well known 11-years cycle. These variationshave a direct effect on ozone photochemistry in our atmosphere, and thewavelength of ultraviolet radiation.

The amount of UV radiation increases with increasing sunspot activity, reaching amaximum at solar maximum. The increase occurs principally in the shorterwavelength UV radiation, less than 240 nm. This means that the ozoneproduction increases when solar activity is at maximum. (2)

The magnitude of the sunspot number during solar maximum is also variable. A90 year variation has been observed, called the Gleissberg cycle. There arethree of these cycles with peaks in 1780, 1870 and 1960. Previous to this, ,during the 1600s, virtually no sunspots were observed in a period that wasreferred as the Maunder minimum: (3)

Two years ago, solar prognosticators generally fell into two distinct camps (blueline) about the timing and intensity of cycle 24. The red line denotes a newprediction based on the lack of recent activity. (3)


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This color-enhanced image from the Precision Solar Photometric Telescope, takenin 2001 near the solar maximum, shows the bright light from faculae beating outthe darkening from the sunspots. (3)

Discussion The main purpose for The Montreal Protocolhas been to stop all addition

of substances in the atmosphere being suspected to deplete the protectinglayer of ozone in our atmosphere. Particularly, unlike forms of CFC-chemicals has been forbidden to bring out in our atmosphere.

The intentions in this attempt to reduce ozone-depleting gases in theatmosphere was announced in the Montreal Protocol (2006) like this :

There is a clear evidence of a decrease in the atmospheric burden ofozone depleting substances , and some early signs of stratosphericozone recovery.

In a NASA report from 2001 they declared that the ozone thinning overAntarctic had remained the same thickness for the previous years, but in2003 the ozone hole grew to its second largest size.

The formation of ozone in our atmosphere comes due to the ultra-violetradiation in the sunlight. The created ozone is unstable, and willdecompose after a certain time. Only a stable UVR-radiation can maintainan appropriate ozone concentration in our atmosphere.

The sun has instability in its radiations, connected to its sunspot activity.There has been long periods with extreme low activity ( Mander Minimum)1650-1700, and a shorter one in 1800-1820, Dalton Minimum).

The number of sunspots showed an increasing rate with a maximum about1999-2003, and a prediction for 2009 to 2020 gives a similar tendency.Whether increased or decreased number of sunspots should create achange in production of ozone and affect its depletion, no reports confirmthis.


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Skien, 24.november 2009

Kjell W. Tveten

References

(1) Montreal Protocol on Substances That Deplete the Ozone Layer.http://en.wikipedia.org/wiki/MONTREAL_Protocol

(2) Ozone variability in the upper stratospherehttp://www.ccpo.odu.edu/SEES/ozone/class/Chap_8/8_4.htm

(3) Sky&Telescope, August 2009: Whats wrong with the Sun ?

(4) What is ozone layer destruction ? The APEC Virtual Center for ...http://www.epcc.pref.osaka.jp/apec/eng/earth/ozone_layer_depletion/sus umu.html

(5) The Ozone Hole , United Nations Environmental Programme http://www.theozonehole.com/
http://en.wikipedia.org/wiki/MONTREAL_Protocolhttp://www.ccpo.odu.edu/SEES/ozone/class/Chap_8/8_4.htmhttp://www.epcc.pref.osaka.jp/apec/eng/earth/ozone_layer_depletion/susumu.htmlhttp://www.epcc.pref.osaka.jp/apec/eng/earth/ozone_layer_depletion/susumu.htmlhttp://www.epcc.pref.osaka.jp/apec/eng/earth/ozone_layer_depletion/susumu.htmlhttp://www.epcc.pref.osaka.jp/apec/eng/earth/ozone_layer_depletion/susumu.htmlhttp://www.theozonehole.com/http://en.wikipedia.org/wiki/MONTREAL_Protocolhttp://www.ccpo.odu.edu/SEES/ozone/class/Chap_8/8_4.htmhttp://www.epcc.pref.osaka.jp/apec/eng/earth/ozone_layer_depletion/susumu.htmlhttp://www.epcc.pref.osaka.jp/apec/eng/earth/ozone_layer_depletion/susumu.htmlhttp://www.theozonehole.com/


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the ozone layer deplation in the atmosphere

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