1. Badlands National Park, SD

2. Chlorofluorocarbons and the Ozone Layer

3. Cast of Characters The stratosphere UV light Stratospheric clouds
~ 15 miles above earth’s surface
UV light
Stratospheric clouds
Gases in the stratosphere
NOx
Ozone
Chlorine
Tropospheric pollutants
CFCs
Halons

4. A Brief History of the Ozone Layer
19th century
Stratospheric ozone identified as block for UV
1920s
Ozone layer identified
Thickness measured
Dobson invents ozone spectrophotometer
1924: measurements of ozone layer begin in Arosa
1930s
1st synthesis of CFCs: T. Midgely
Low boiling point
Nontoxic
Not inflammable
Applications developed
Refrigeration
1950s
CFC uses expand rapidly

5. Ozone Layer: Continued
1960s
SST fleet proposed
NOx catalytic destruction of O3
1970s: fears of O3 destruction
Congress axes funds for SSTs
Cl implicated
CFCs detected in stratosphere
Rowland & Molina warn of CFC role
1977: 1st meeting on O3 depletion
1978: US bans nonessential CFC aerosols
1985: Vienna Convention
1987: Montreal Protocol
1991: Phase out CFCs by 1996
US, Europe
2000: Maximum CFC in stratosphere
2010: End CFC use worldwide

6. 1987: measuring ozone

7. Ozone Levels In troposphere Limit value: In stratosphere:
110 µg/m3 for 8-hour-average concentrations
In stratosphere:
Over US: ~ 300 DU
Over Antarctica: ~ 117 DU
Dobson Unit
27x106 molecules/cm3.
Winnipeg is about 200 miles south of Edmonton (and considerably to the east)

8. Stratospheric Ozone Levels: Temporal and Geographic Variation
Oslo, Norway
New South Wales, Australia
Stratospheric Ozone Levels:
Temporal and Geographic Variation

12. Some Recovery of the Ozone Layer Is (Probably) Occurring

13. The Ozone Layer Without Regulation of CFCs
PREDICTED:
The Ozone Layer Without Regulation of CFCs

14. Chlorofluorocarbons 102 year residence time
Trichlorofluoromethane: CFC-11 --
50 yr residence time
Dichlorodifluoroethane: CFC-12 --
102 year residence time

15. Related Compounds Bromochlorodifluoromethane: Halon-1211 --
Bromotrifluoromethane:
Halon years
Carbon tetrachloride:
Halon years
Dichloromethane
(Methylene chloride)
Methyl bromide:
0.7 years
Methyl chloride

17. Major Uses of CFCs

18. ……. And the Interaction

19. CFCs in the Atmosphere: 1977-1995

20. Remember The Time Line
1930s
1st synthesis of CFCs by T. Midgely
Low boiling point; nontoxic; not inflammable
Application: Refrigeration
1950s
CFC uses expand rapidly
1970s: fears of O3 destruction
Congress axes funds for SSTs
Cl implicated
CFCs detected in stratosphere
Rowland & Molina warn of CFC role
By 2010, CFC production was officially ended worldwide. How did this happen?

21. Repairing the Ozone Layer: International Action
Chemicals Regulated
Halocarbons
CFCs
HCFCs
Temporary replacements for CFCs
HBFCs
To prevent increasing use
HFCs
to be phased out??
Methyl bromide
Carbon tetrachloride
Methyl chloroform
1976: 1st UNEP meeting
1985 Vienna Convention
Intergovernmental
Cooperation
Exchange of information
Systematic observation of O3
Monitoring of CFC production
Framework agreement
No controls or targets
1987 Montreal Protocol adopted
Phase-out schedule for regulated chemicals
Method for modifying agreement
Leeway for developing countries

22. Consumption of chlorofluorocarbons (tonnes of ozone depleting potential) by region and global, 1988–2002

23. Top: CFC Production 1969-2003 Bottom: HFC production 1989-2003
HFCs do not deplete the ozone layer, but they do contribute to climate change.

27. International cooperation seems to have solved the ozone layer problem:
Can we do it again for climate change?
What is the role of the US?

28. Badlands National Park, SD