Transcript of 1 Ozone depletion module prepared by Eugene C. Cordero Lesson 2: "The Antarctic Ozone Hole"
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- 1 Ozone depletion module prepared by Eugene C. Cordero Lesson
2: "The Antarctic Ozone Hole"
- Slide 2
- 2 Ozone depletion module prepared by Eugene C. Cordero Learning
objectives To develop an understanding for the history of ozone
depletion To develop an understanding for what the ozone hole is.
To understanding how the ozone hole is produced.
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- 3 Ozone depletion module prepared by Eugene C. Cordero Early
concerns about ozone depletion
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- 4 Ozone depletion module prepared by Eugene C. Cordero History
of Ozone Depletion CFCs developed in 40s and 50s Refrigerants,
propellants, fire retardants 1970s CFCs detected in atmosphere.
Many of these have long atmospheric lifetimes (10s to 100s of
years) 1974 Rowland and Molina propose that CFCs can destroy ozone
in the stratosphere. CFCs broken apart by UV radiation forming
chlorine which can destroy ozone quickly: O 3 +Cl ClO+ O 2
(Catalytic Reaction) ClO+O Cl+O 2
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- 5 Ozone depletion module prepared by Eugene C. Cordero History
of ozone depletion 1970s Supersonic Aircraft fleet under review.
1978: CFCs used in aerosols banned. 1985: British Antarctic Survey
reports 40% loss of ozone over Antarctica during spring. (NASA
confirms) 1987: Signing of the Montreal Protocol International
agreement to reduce CFC use Later agreements agreed to completely
phase out CFC and halons. 1996 Complete ban on industrial
production of CFCs goes into effect.
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- 6 Ozone depletion module prepared by Eugene C. Cordero The
Ozone Hole First discovered in 1985: observations from Antarctica
extend back into 1950s. Characterized as a rapid depletion of ozone
over Antarctica during spring. Ozone hole season, Spring (August
October) Ozone hole located over mainly over Antarctica. Ozone hole
recovers by late December Ozone hole caused by human chemicals
(CFCs) Ozone hole not present in early 1970s
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- 7 Ozone depletion module prepared by Eugene C. Cordero Total
Ozone: October 14, 1997
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- 8 Ozone depletion module prepared by Eugene C. Cordero Where is
the ozone hole? Ozone hole largely restricted to areas over
Antarctica Ozone hole may pass over tip of South America Ozone hole
seldom comes near Australia. Northern Hemisphere (NH) has no ozone
hole like the Southern Hemisphere However, recently NH has
experienced the occurrence of ozone mini holes.
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- 9 Ozone depletion module prepared by Eugene C. Cordero
Satellite Total Ozone from 70s and 90s
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- 10 Ozone depletion module prepared by Eugene C. Cordero Ozone
observations over Antarctica
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- 11 Ozone depletion module prepared by Eugene C. Cordero Is the
ozone hole getting worse?
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- 12 Ozone depletion module prepared by Eugene C. Cordero
Animation
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- 13 Ozone depletion module prepared by Eugene C. Cordero Ozone
Hole Recipe Ingredients: Chlorine gas Cold Temperatures (~-80C)
Instructions: Allow cold temperatures to form Polar Stratospheric
Clouds (1-2 weeks). Allow time for polar stratospheric clouds to
convert chlorine gas into ozone destroying chemicals. (1 month)
Bake ingredients with sunlight. Presto, a delicious ozone hole!
Science interpretation Chlorine gas is abundant in atmosphere due
to CFCs Cold Temperatures (~-80C) only occur over Antarctica during
the cold winter. Polar Stratospheric Clouds allow ozone friendly
chlorine to be transformed into ozone destroying chlorine. Ozone
depletion then starts when sun returns to Antarctica in the spring
Ozone hole grows from late August through till October.
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- Chlorine gas Cold Temperatures T~-80C Polar Stratospheric
Clouds Ozone destroying chemicals Everywhere in Atmosphere Sunlight
Ozone Hole produces and produces Ozone Hole Formation
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- 15 Ozone depletion module prepared by Eugene C. Cordero Summary
The Ozone hole develops during spring over Antarctica. The Ozone
hole is produced by unique combination of weather (cold temps) and
chemistry (chlorine). Global ozone trends are negative except in
the tropics.