1. 19-4 How Have We Depleted O3 in the Stratosphere and What Can We Do?
Concept 19-4A Our widespread use of certain chemicals has reduced ozone levels in the stratosphere, which has allowed more harmful ultraviolet radiation to reach the earth’s surface.
Concept 19-4B To reverse ozone depletion, we must stop producing ozone-depleting chemicals and adhere to the international treaties that ban such chemicals.

2. Our Use of Certain Chemicals Threatens the Ozone Layer
A layer of ozone in the __________________ keeps about ______ of the sun’s harmful UV radiation from reaching earth’s surface
Measurements show…
A seasonal depletion (___________________) above Antarctica during October and November
Commonly called the ___________________
Ozone depleted air also flows over Australia, New Zealand, South America, South Africa for a few __________
Raises UV levels by _________ and in some years up ________
stratosphere
95%
ozone thinning
ozone hole
weeks
3-10%
20%

3. Natural Capital Degradation: Massive Ozone Thinning over Antarctica in 2009
Figure 19.21: Natural capital degradation.
This colorized satellite image shows massive ozone thinning over Antarctica during several months in The center of this image shows a large area where the concentration of ozone has decreased by 50% or more. (Data from NASA)
Fig , p. 521

4. Lower Stratosphere (ozone layer)
NOT
Ozone depletion and the greenhouse effect are ________ the same thing!
Solar radiation
Reflected by atmosphere
Radiated by atmosphere
as heat
UV radiation
Lower Stratosphere (ozone layer)
Most UV absorbed
by ozone
Heat radiated by the earth
Visible light
Troposphere
Heat added to troposphere
Greenhouse effect
Figure 3.4: High-quality solar energy flows from the sun to the earth. As it interacts with the earth’s air, water, soil, and life, it is degraded into lower-quality energy (heat) that flows back into space.
Absorbed
by the earth
The ozone layer absorbs _______ rays while the greenhouse effect involves __________________ rays UV
infrared
Fig. 3-4, p. 57

5. Student Misconceptions
What is wrong with this example of a student answer?
“As the ozone layer is depleted, more UV rays reach the earth and heat up the atmosphere, causing global warming.”
Global warming is caused by the interaction of infrared
rays with greenhouse gases…not UV

6. Our Use of Certain Chemicals Threatens the Ozone Layer
In 1974: _____________ and _______________ demonstrated that chlorofluorocarbons (_________) were destroying the protective ozone in the stratosphere
Inexpensive to manufacture…popular as ___________ in air conditioners and refrigerators; _______________ in aerosol spray cans; __________ used to make insulation and packaging
Rowland
Molina
CFCs
coolants
propellants
gases

7. Our Use of Certain Chemicals Threatens the Ozone Layer
Other ozone-depleting chemicals
Halons and hydrobromofluorocarbons (___________) used in fire extinguishers
______________________...a widely used fumigant
_____________________...emitted by space shuttles
And many _________________ solvents
HBFCs
Methyl bromide
Hydrogen chloride
cleaning

8. Individuals Matter: Rowland and Molina—A Scientific Story of Courage and Persistence
Research
CFCs are ______________ in the atmosphere
After humans release them they _________ into the stratosphere over __________ years
________________ under high-energy UV radiation
Halogens produced accelerate the breakdown of O3 to O2
Each CFC molecule can last _____________years
After _________ of delay tactics.... ___________ stopped producing CFCs
1995: ______________ in chemistry
persistent
rise
11-20
Breakdown
65-385
14 years
DuPont
Nobel Prize

9. Why Should We Worry about Ozone Depletion?
Damaging UV-A and UV-B radiation
Increase eye _______________ and ______________
Decreased crop and forest productivity for UV __________ plants
Impair or destroy ___________________
CO2 absorbers and base of aquatic food chains
While in the troposphere, CFCs also act as _______________ gases
Increased acid __________________ and photochemical ______________
cataracts
skin cancer
sensitive
phytoplankton
greenhouse
deposition
smog

10. Natural Capital Degradation: Effects of Ozone Depletion
Figure 19.22: Decreased levels of ozone in the stratosphere can have a number of harmful effects. (Concept 19-4a). Questions: Which three of these effects do you think are the most threatening? Why?
Fig , p. 522

11. What Can You Do? Reducing Exposure to UV Radiation
Figure 19.23: Individuals matter.
You can reduce your exposure to harmful UV radiation. Question: Which of these precautions do you already take?
Fig , p. 523

12. We Can Reverse Stratospheric Ozone Depletion (1)
_________ producing all ozone-depleting chemicals
60–100 years for complete recovery of the O3 layer
1987: _____________________....goal was to cut emissions of CFCs by about ______ between 1989 and 2000
1992: ____________________...agreed upon __________________ phase out
Ozone protocols: ________________ is the key
Stop
Montreal Protocol
35%
Copenhagen Protocol
accelerated
prevention

13. We Can Reverse Stratospheric Ozone Depletion (2)
Substitutes for most CFCs are available…unfortunately the most widely used substitutes, ____________________, (HFCs) act as a greenhouse gas
More are being developed
hydrofluorocarbons

14. Three Big Ideas
Considerable scientific evidence indicates that the earth’s atmosphere is warming, mostly because of _______________ activities, and that this is likely to lead to significant climate disruption during this century that could have severe and long-lasting harmful consequences.
human

15. Three Big Ideas
Reducing the projected harmful effects of rapid climate disruption during this century requires ______________ action to…
increase energy efficiency
sharply reduce greenhouse gas emissions
rely more on renewable energy resources
slow population growth.
We need to continue _________________ the use of chemicals that have reduced ozone levels in the stratosphere and allowed more harmful ultraviolet radiation to reach earth’s surface.
emergency
phasing out

16. Review Questions
What is the main class of chemicals responsible for ozone thinning?
What are some detrimental effects caused by ozone depletion?
CFCs
Skin cancer / cataracts
More acid deposition
Damage to crops/forests
Photochemical smog
Damage to phytoplankton

17. Review Questions
What different electromagnetic rays are associated with atmospheric warming and the ozone layer?
How are the problems of atmospheric warming and ozone depletion linked?
infrared vs. ultraviolet
Ozone depletion – less phytoplankton – less CO2 absorption
CFCs and some subtitutes act as greenhouse gases