MET 112 Global Climate Change: Lecture 19

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MET 112 Global Climate Change Lecture 19

• Ozone Depletion
• Eugene Cordero

• Outline
• History of Ozone Depletion
• The Ozone Hole what, where, why?
• Ozone into the future

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Learning objectives

• To develop an understanding for ozone depletion
  and how it influences midlatitudes.
• To develop an understanding for how ozone values
  are going to change in the future.

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Early concerns of ozone depletion
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History of Ozone Depletion

• Chlorofluorocarbons (CFCs) developed in 1940s
  and 50s as
• 1970s CFCs detected in upper atmosphere.
• Many of these have long atmospheric lifetimes
• 1974 Rowland and Molina propose that CFCs can
  destroy ozone in the stratosphere.
• CFC contain chlorine (Cl)

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History of Ozone Depletion

• Chlorofluorocarbons (CFCs) developed in 1940s
  and 50s as
• 1970s CFCs detected in upper atmosphere.
• Many of these have long atmospheric lifetimes
• 1974 Rowland and Molina propose that CFCs can
  destroy ozone in the stratosphere.
• CFC contain chlorine (Cl)

Refrigerants, propellants, fire retardants

• (10s to 100s of years)

Chlorine can destroy ozone rapidly
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Ozone Depletion History

• 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.
• 2002 Developing countries to phase out CFCs

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Ozone Hole

• First discovered in 1985 observations from
  Antarctica extend back into 1950s.
• Mechanisms well understood by early 1990s.

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Ozone Hole

• First discovered in 1985 observations from
  Antarctica extend back into 1950s.
• Characterized as a rapid depletion of ozone over
  Antarctica during spring.
• Mechanisms well understood by early 1990s.

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Ozone observations over Antarctica
What year did the ozone hole first appear?
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Ozone observations over Antarctica
What year did the ozone hole first appear?
early 1980s
Ozone hole definition
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What causes the ozone hole?

• Ozone Hole Recipe (make your own!)
• 1. _____________________
• 2. _____________________
• Formation of Polar Stratospheric Clouds (PSCs)
• 3. ______________________
• Winter Polar Vortex is region of strong winds
  forming an isolated container from the middle
  latitudes.
• This produces cold temperatures.
• Allows chemistry to develop undisturbed.

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What causes the ozone hole?

• Ozone Hole Recipe (make your own!)
• 1. _____________________
• 2. _____________________
• Formation of Polar Stratospheric Clouds (PSCs)
• 3. ______________________
• Winter Polar Vortex is region of strong winds
  forming an isolated container from the middle
  latitudes.
• This produces cold temperatures.
• Allows chemistry to develop undisturbed.

Abundant chlorine
Cold temperatures
Sunlight to activate chemistry
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Where is the ozone hole?

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Where is the ozone hole?

• Ozone hole largely restricted to areas over
  Antarctica
• Ozone hole may pass over tip of South America

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Ozone levels from 70s and 90s
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Question Why does the ozone hole only appear in
the spring?
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Ozone Hole Recipe
Ozone Hole Formation
Only during winter
Cold Temperatures
Only during spring
produces
Ozone destroying chemicals


and
produces
produces
and


Everywhere in Atmosphere
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Ozone Hole Recipe
Ozone Hole Formation
Only during winter
Cold Temperatures T-80C
Only during spring
produces
Ozone destroying chemicals
Sunlight
Polar Stratospheric Clouds
and
produces
produces
and
Chlorine gas
Ozone Hole
Everywhere in Atmosphere
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What about the northern hemisphere? Is there
an ozone hole in the Arctic?
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Northern Hemisphere Total Ozone
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Question

• What about the northern hemisphere? Is there an
  ozone hole in the Arctic?
• Why is that?

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Question

• What about the northern hemisphere? Is there an
  ozone hole in the Arctic?
• No, although recently mini ozone holes have
  appeared occasionally.
• Why is that?
• I have no idea!!!

• Temperatures dont get cold enough

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High Latitudes temperatures at 20km
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High Latitudes temperatures at 20km
N. Hem temperatures
Temperature required for ozone hole
S. Hem temperatures
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Why is there no ozone hole in the Northern
Hemisphere?

• Stronger weather systems warm polar region more
  efficiently.

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Why is there no ozone hole in the Northern
Hemisphere?

• Larger land mass in N. Hem produces stronger
  weather systems.
• Stronger weather systems warm polar region more
  efficiently.
• Warmer temperatures restrict the formation of
  polar stratospheric clouds, essential for ozone
  hole formation

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Is the ozone hole getting much bigger?
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Is the ozone hole getting much bigger?
No, not over the last few years
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How is ozone layer changing globally?

• Ozone levels are declining globally
• ozone trends
• San Francisco (37N) _____________
• Juneau, Alaska (58N) _____________
• Ushuaia, Argentina (55S) _____________
• Quito, Ecuador (1S) _____________

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Ozone levels have changed over the last two
decades Largest declines in the high latitude
southern hemisphere
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How is ozone layer changing globally?

• Ozone levels are declining globally
• ozone trends
• San Francisco (37N) _____________
• Juneau, Alaska (58N) _____________
• Ushuaia, Argentina (55S) _____________
• Quito, Ecuador (1S) _____________

-4 ? 1
-5 ? 1
-8 ? 1
-0 ? 1
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What is being done about ozone depletion?

• Montreal Protocol (1988) international
  agreement to phase out ozone depleting chemicals
• Further amendments accelerated the phase out.
• Developed countries have switched to HCFCs (more
  ozone friendly!)

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What is being done about ozone depletion?

• Montreal Protocol (1988) international
  agreement to phase out ozone depleting chemicals
• Further amendments accelerated the phase out.
• Developed countries have switched to HCFCs (more
  ozone friendly!)
• Developing countries have until 2004 to phase out
  CFCs.

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Is the Montreal Protocol working?

• Seems to be
• Recent observations indicate that chlorine is
  beginning to decline in the atmosphere.

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What are predictions for the future?

• Model simulations suggest
• atmospheric chlorine will return to pre-80s
  level __________________ .
• Uncertainties still remain
• ____________________
• ____________________

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What are predictions for the future?

• Model simulations suggest
• atmospheric chlorine will return to pre-80s
  level __________________ .
• Uncertainties still remain
• ____________________
• ____________________

In next 50 years or so
A slow ozone recovery should follow decreasing
chlorine concentrations!!!
Phase out of CFCs
Influence of global warming
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What is the connection between ozone depletion
and global warming?

• No direct connection between these environmental
  issues.
• Global warming produces

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What is the connection between ozone depletion
and global warming?

• No direct connection between these environmental
  issues.
• Global warming produces
• Tropospheric warming
• Stratospheric cooling

• However Global warming may enhance ozone
  depletion

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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
• Ozone hole chemistry

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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
• Ozone hole chemistry
• PSCs will likely increase
• So slightly more ozone depletion
• Global warming will delay recovery of ozone layer

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Lecture Summary

• Ozone depletion is good example of science and
  policy working together to manage a global
  environmental concern.
• The Ozone hole is produced by unique combination
  of weather ___________ and chemistry
  (___________).
• The Ozone hole develops during _______ over
  Antarctica.
• Global ozone trends are ___________ except in the
  tropics,
• Global ozone trends are expected to recover in
  next ___ or more years.

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Lecture Summary

• Ozone depletion is good example of science and
  policy working together to manage a global
  environmental concern.
• The Ozone hole is produced by unique combination
  of weather ___________ and chemistry
  (___________).
• The Ozone hole develops during _______ over
  Antarctica.
• Global ozone trends are ___________ except in the
  tropics,
• Global ozone trends are expected to recover in
  next ___ or more years.

cold temps
chlorine
spring
negative
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Stratospheric ozone increasing, tropospheric
ozone decreasing
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Concept Map Terms

•  Dobson Unit
•  Total Ozone
•  Tropospheric ozone
•  Good ozone
•  Stratospheric ozone
•  Bad ozone
• Recovery
•  TOMS
• Gas
• 2050
• Cold temperatures
• Northern Hemisphere
• Global warming
• PSCs
• Montreal Protocol

• Ozone
•  UV radiation
•  Sun
•  Gas
•  Skin Cancer
•  Summer
•  Winter
•  Spring
•  Atmosphere
•  CFCs
•  South Pole
•  Trends
•  Ozone hole
•  Chlorine

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Example of ozone concept map Concept Map
Terms     Ozone   UV radiation   Sun   Gas   Skin
Cancer   Summer   Winter   Spring   Atmosphere   C
FCs   South Pole   Trends   Ozone
hole   Chlorine   Dobson Unit   Total
Ozone   Tropospheric ozone   Good
ozone   Stratospheric ozone   Bad ozone   TOMS
Example of ozone concept map Concept Map
Terms     Ozone   UV radiation   Sun   Gas   Skin
Cancer   Summer   Winter   Spring   Atmosphere   C
FCs   South Pole   Trends   Ozone
hole   Chlorine   Dobson Unit   Total
Ozone   Tropospheric ozone   Good
ozone   Stratospheric ozone   Bad ozone   TOMS