Transcript O3zone Story Terry Deshler, Atmospheric Science • Formation • Importance • Loss – Before 1985 – After 1985 • Recovery • Relationship to global warming • The end.

O3zone Story
Terry Deshler, Atmospheric Science
• Formation
• Importance
• Loss
– Before 1985
– After 1985
• Recovery
• Relationship to global warming
• The end
Relationship to Global Warming
• Peripheral
• Ozone has a slight greenhouse effect, but
• Loss of ozone over Antarctica may
have intensified the polar vortex and
reduced the warming expected in
Antarctica
• CFCs are a significant green house
gas
• Reduction of CFCs largest single
human action mitigating the current
warming
The End?
• No, we have to limit the release of CFCs
into the atmosphere from now on.
• The good news - the atmosphere will
cleanse itself of present atmospheric
chlorine.
• The bad news - it will take another 50
years to see the ozone hole above
Antarctica disappear.
Ozone Formation
• O2 + h  O + O
• Then, O + O + M  O2 + M
• or O + O2 + M  O3 + M (Ozone created)
–
Where will this primarily occur?
• Also, O3 + h ( > 310 nm)  O2 + O
• and O3 + h ( < 310 nm)  O2* + O* (UV absorption)
• O2* + O2  2O2 + thermal energy (Excess energy dumped
• O2*  O2 + h ( = 1.3 m)
in ozone layer)
Importance of ozone
• Absorbs DNA damaging UV radiation
– This UV affects both animals and plants
• SH/NH differences - In summer UV
radiation is 50% more intense in SH than
NH. Australia - world leader in skin cancer
– Reasons
– 10% - Earth is closer to sun in SH summer than
NH summer
– 20% - Antarctic ozone loss/clearer atmosphere
– 20% - Unknown
Food Preservation
• 100 BC - 1700s, Early methods: Drying, Salting, Cool
cellars/Spring houses, Pickling, Fermenting, Canning.
• Cooking -> could eat spoiled food - spices to hide the flavor.
• 1803 Ice Boxes - Thomas Moore invented the insulated box,
with ice was in a separate container above the food storage
area. Relied on stores of natural ice from frozen lakes and
rivers.
• 1850s - Methods to artificially produce ice were developed.
• 1890 - Warm weather/rain lead to a shortage of natural ice.
Spurred the development of mechanical refrigeration.
Refrigeration
• 1918 - Kelvinator, First refrigerator introduced to American
market.
• 1920s - Refrigerators used ammonia (NH4), sulfur dioxide (SO2),
(toxic, odorous), and methyl chloride (CH3Cl), (toxic, no odor) silent killer.
• 1928 - Thomas Midgley, Fridgidaire, dichlorodifluoromethane (CCl2F2)
• 1929 - Fridgidaire and DuPont joined to produce CCl2F2, and
CFCl3 as Freon.
1974 - Molina and Rowland - simple question What happens to CFCs released into the
atmosphere? (awarded Nobel prize Chemistry 1995)
CCl3 F (F-11) + h ( < 240 nm, z > O3 layer)  CCl2F + Cl
CCl2F2 (F-12) + h ( < 240 nm, z > O3 layer)  CClF2 + Cl
• Then
•
Cl + O3
•
ClO + O
• Net: O3 + O


ClO + O2

Cl + O2
O2 + O2
• This would occur above ozone layer
altitudes above 30 km
Reservoir molecules
• 1975 - 1980 – Predicted ozone losses
above 30 km were not observed.
Reservoir molecules discovered.
– Cl + CH4 HCl + CH3
– ClO + NO2
 ClONO2
– HCl and ClONO2 are reservoir species.
1984 – Models predict 10% ozone loss in 100
years for current CFC production rates.
1986
1987
1988
1989
1990
1991
1992
1993
1994
Ozone
Profiles
McMurdo
Station,
Antarctica
1986 - 1994
Late winter
spring
During Winter
Catalytic Cycle Polar Stratosphere
–
PSC particle + HCl + ClONO2  Cl2
–
Cl2 + h
– 2[
Cl + O3
– ClO + ClO + M



Cl + Cl
ClO + O]
ClOOCl + M (M=N2 or O2)
–
–


Cl + ClOO
Cl + O2 + M

3O2
ClOOCl + h
ClOO + M
– h = Sun’s return
• Net
2O3 + h
• A single Cl atom can destroy more than100,000 ozone
molecules.
• This cycle will continue until the NO2 and OH lost in the form of
HNO3 in polar stratospheric clouds is replenished by mid latitude
air, thus converting Cl back to its reservoir species.
Nitric acid/water
Ice
Nitric acid/water
Ice
Antarctic
ozone hole
discovered
Molina &
Rowland,
1974
Montreal
Protocol, and
amendments
Reservoir
Molecules
Discovered
An Industry in Transition
1974
1200 Ozone Depletion
Hypothesis
1986
Base Year for
Montreal Protocol
1996
CFC Phaseout
Complete in
Developed Countries
800
HFCs
HCFCs
CFCs
400
20
15
20
12
20
09
20
06
20
03
20
00
19
97
19
94
19
91
19
88
19
82
19
79
19
76
19
73
19
70
0
19
85
Thousands of tonnes
1600
Refrigerants
Other
Refrigerants
Foam Expansion
Solvents
Propellants
Fire Extinguishants
Effective Equivalent Stratospheric Chlorine (pptv)
4500
Compliments of Paul Newman
and the Goddard automailer
4000
3500
3000
2500
2000
1500
1000
1960
1980
2000
2020
2040
Years
Return
2060
2080
2100