BAESI – Climate Literacy
Ozone – Climate Change Connections
Eugene Cordero
San Jose State University
Summer 2013
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Why is the ozone layer important
Ozone acts as the Earth’s protective shied
against the Sun’s harmful Ultraviolet radiation (UV
radiation).
The natural development of the ozone layer
permitted life to evolve above water.
Without an ozone layer,
life would not exist on Earth!
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Ozone, the good and the bad
Ozone is often
confused:
Stratosphere
Altitude (km)
Good ozone:
Stratospheric ozone
The ozone layer
Bad ozone:
Tropospheric ozone
Smog
Troposphere
Note: ozone is also
greenhouse gas
ozone amount
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Ozone Depletion
Topics
§  History of Ozone Depletion
§  The Ozone Hole: what, where, why?
§  Ozone into the future
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Early concerns of ozone depletion
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History of Ozone Depletion
§  Chlorofluorocarbons (CFCs) developed in 1940’s
and 50’s as:
–  Refrigerants, propellants, fire retardants
§  1970’s CFCs detected in upper atmosphere.
–  Many of these have long atmospheric lifetimes:
(10’s to 100’s of years)
–  1974 Rowland and Molina propose that CFC’s
can destroy ozone in the stratosphere.
–  CFC contain chlorine (Cl)
–  Chlorine can destroy ozone rapidly
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Cl + O3 è ClO + O2
ClO + O è Cl + O2
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What is being done about ozone
depletion?
§  Montreal Protocol ~ (1988) international agreement
to reduce ozone depleting chemicals
§  Further amendments accelerated the phase out..
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Is the Montreal Protocol working?
Seems to be!!!
Recent observations indicate that chlorine is
declining in the upper atmosphere.
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What are predictions for the future?
§  Model simulations suggest:
–  Atmospheric chlorine will return to pre-80’s level in the
next 50 years or so
A slow ozone recovery should follow
decreasing chlorine concentrations!
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What is the connection between ozone
depletion and global warming?
§  No direct connection between these environmental
issues.
§  However: Global warming may enhance
ozone depletion
§  Global warming produces:
–  Tropospheric warming &
–  Stratospheric cooling
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What is the connection between ozone
depletion and global warming?
§  An increase in greenhouse gases traps more heat
and thus
–  The stratosphere tends to cool (stratospheric
cooling)
§  Therefore, if the stratosphere cools, then
–  slightly more ozone depletion
§  Global warming will delay recovery of ozone layer
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What is there was no
Montreal Protocol?
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350
Future
Ozone Thickness
300
250
200
150
Future world avoided
100
1960
1980
2000
2020
2040
2060
Newman et al. 2009
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By 2050:
Sunburn < 5 minutes
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Sunburn in
less than 5 minutes
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Sunburn in
less than 5 minutes
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Conclusions
§  Ozone depletion and climate change can be
viewed as distinct environmental issues
§  Ozone recovery expected
§  At deeper level, some connections
–  Ozone is greenhouse gas
–  CFCs are greenhouse gas
–  Climate change will delay ozone recovery.
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http://ozonewatch.gsfc.nasa.gov/
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Ozone Hole Recipe
Ingredients:
Science interpretation
§  Chlorine gas
§  Cold Temperatures (~-80C)
§  Chlorine gas is abundant in atmosphere
due to CFC’s
§  Cold Temperatures (~-80C) only occur
over Antarctica during the cold winter.
Instructions:
§  Allow cold temperatures to form Polar
Stratospheric Clouds (1-2 weeks).
§  Polar Stratospheric Clouds allow ozone
friendly chlorine to be transformed into
§  Allow time for polar stratospheric clouds
ozone destroying chlorine.
to convert chlorine gas into ozone
destroying chemicals. (1 month)
§  Ozone depletion then starts when sun
returns to Antarctica in the spring
§  Bake ingredients with sunlight.
§  Ozone hole grows from late August
§  Presto, a delicious ozone hole!
through till October.
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Spring
Sun
produces
Atmosphere
present in
Skin
Cancer
is a
causes
Gas
UV
Radiation
Ozone
Hole
Automobiles
is present in the
is a
is depletion of
cause
Good
Ozone
protects the
earth from
produce
Bad
Ozone
Ozone
CFC’s
contain
may cause
has
destroy
has
Stratosphere
Chlorine
Global
Warming
Troposphere
is the column
Dobson
Unit
is measurement of
Total
Ozone
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