1. Climate Change and Ozone Depletion
Chapter 20
Climate Change and Ozone Depletion

2. Chapter Overview Questions
How have the earth’s temperature and climate changed in the past?
How might the earth’s temperature change in the future?
What factors influence the earth’s average temperature?
What are some possible beneficial and harmful effects of a warmer earth?

3. Chapter Overview Questions (cont’d)
How can we slow projected increases in the earth’s temperature or adapt to such changes?
How have human activities depleted ozone in the stratosphere, and why should we care?

4. Updates Online
The latest references for topics covered in this section can be found at the book companion website. Log in to the book’s e-resources page at to access InfoTrac articles.
InfoTrac: Upset about offsets; Emissions offsets. The Economist (US), August 5, 2006 v380 i8489 p53US.
InfoTrac: Geologist seeks answers in Valley's house-sized rocks. Anchorage Daily News, August 2, 2006.
InfoTrac: Capital Pollution Solution? Jeff Goodell. The New York Times Magazine, July 30, 2006 p34(L).
Union of Concerned Scientists: Human Fingerprints
Science Daily: Deep-sea Sediments Could Safely Store Man-made Carbon Dioxide
Discovery Channel: Global Warming

5. Video: Kyoto Protocol
This video clip is available in CNN Today Videos for Environmental Science, 2004, Volume VII. Instructors, contact your local sales representative to order this volume, while supplies last.

6. Video: Melting Glaciers
This video clip is available in CNN Today Videos for Environmental Science, 2004, Volume VII. Instructors, contact your local sales representative to order this volume, while supplies last.

7. Video: Global Warming
This video clip is available in CNN Today Videos for Environmental Science, 2004, Volume VII. Instructors, contact your local sales representative to order this volume, while supplies last.

8. Core Case Study: Studying a Volcano to Understand Climate Change
NASA scientist correctly predicted that the 1991 Philippines explosion would cool the average temperature of the earth by 0.5Co over a 15 month period and then return to normal by 1995.
Figure 20-1

9. Core Case Study: Studying a Volcano to Understand Climate Change
The NASA model was correct.
The success convince scientists and policy makers that climate model projections should be taken seriously.
Other climate models have shown that global temperatures are likely to rise several degrees during this century.

10. PAST CLIMATE AND THE GREENHOUSE EFFECT
Over the past 900,000 years, the troposphere has experienced prolonged periods of global cooling and global warming.
For the past 1,000 years, temperatures have remained fairly stable but began to rise during the last century.

11. PAST CLIMATE AND THE GREENHOUSE EFFECT
Figure 20-2

12. Average temperature over past 900,000 years
Average surface temperature (°C)
Figure 20.2
Science: estimated changes in the average global temperature of the atmosphere near the earth’s surface over different periods of time. Although a particular place might have much lower or much higher readings than the troposphere’s average temperature, such averages provide a valuable way to measure long-term trends. QUESTION: What two conclusions can you draw from these diagrams? (Data from Goddard Institute for Space Studies, Intergovernmental Panel on Climate Change, National Academy of Sciences, National Aeronautics and Space Agency, National Center for Atmospheric Research, National Oceanic and Atmospheric Administration)
Thousands of years ago
Fig. 20-2a, p. 465

13. Average temperature over past 130 years
Average surface temperature (°C)
Figure 20.2
Science: estimated changes in the average global temperature of the atmosphere near the earth’s surface over different periods of time. Although a particular place might have much lower or much higher readings than the troposphere’s average temperature, such averages provide a valuable way to measure long-term trends. QUESTION: What two conclusions can you draw from these diagrams? (Data from Goddard Institute for Space Studies, Intergovernmental Panel on Climate Change, National Academy of Sciences, National Aeronautics and Space Agency, National Center for Atmospheric Research, National Oceanic and Atmospheric Administration)
Year
Fig. 20-2b, p. 465

14. Temperature change over past 22,000 years
Agriculture established
Temperature change (C°)
End of
last ice
age
Average temperature over past
10,000 years = 15°C (59°F)
Figure 20.2
Science: estimated changes in the average global temperature of the atmosphere near the earth’s surface over different periods of time. Although a particular place might have much lower or much higher readings than the troposphere’s average temperature, such averages provide a valuable way to measure long-term trends. QUESTION: What two conclusions can you draw from these diagrams? (Data from Goddard Institute for Space Studies, Intergovernmental Panel on Climate Change, National Academy of Sciences, National Aeronautics and Space Agency, National Center for Atmospheric Research, National Oceanic and Atmospheric Administration)
Years ago
Fig. 20-2c, p. 465

15. Temperature change over past 1,000 years
Temperature change (C°)
Figure 20.2
Science: estimated changes in the average global temperature of the atmosphere near the earth’s surface over different periods of time. Although a particular place might have much lower or much higher readings than the troposphere’s average temperature, such averages provide a valuable way to measure long-term trends. QUESTION: What two conclusions can you draw from these diagrams? (Data from Goddard Institute for Space Studies, Intergovernmental Panel on Climate Change, National Academy of Sciences, National Aeronautics and Space Agency, National Center for Atmospheric Research, National Oceanic and Atmospheric Administration)
Year
Fig. 20-2d, p. 465

16. How Do We Know What Temperatures Were in the Past?
Scientists analyze tiny air bubbles trapped in ice cores learn about past:
troposphere composition.
temperature trends.
greenhouse gas concentrations.
solar, snowfall, and forest fire activity.
Figure 20-3

17. How Do We Know What Temperatures Were in the Past?
In 2005, an ice core showed that CO2 levels in the troposphere are the highest they have been in 650,000 years.
Figure 20-4

18. Concentration of carbon dioxide
in the atmosphere (ppm)
Carbon dioxide
Variation of temperature (C°)
from current level
Figure 20.4
Science: atmospheric carbon dioxide levels and global temperature. Estimated long-term variations in average global temperature of the atmosphere near the earth’s surface are graphed along with average troposphere CO2 levels over the past 160,000 years. The rough correlation between CO2 levels in the troposphere and temperature shown in these estimates based on ice core data suggests a connection between the two variables. In 2005, an ice core showed that CO2 levels in the troposphere are the highest they have been in 650,000 years. QUESTION: What are the implications of these data on your lifestyle now and in the future? (Data from Intergovernmental Panel on Climate Change, National Center for Atmospheric Research, and Physics Institute at the University of Bern, Switzerland)
Temperature change
End of last ice age
Thousands of years before present
Fig. 20-4, p. 466

19. The Natural Greenhouse Effect
Three major factors shape the earth’s climate:
The sun.
Greenhouse effect that warms the earth’s lower troposphere and surface because of the presence of greenhouse gases.
Oceans store CO2 and heat, evaporate and receive water, move stored heat to other parts of the world.
Natural cooling process through water vapor in the troposphere (heat rises).

20. Major Greenhouse Gases
The major greenhouse gases in the lower atmosphere are water vapor, carbon dioxide, methane, and nitrous oxide.
These gases have always been present in the earth’s troposphere in varying concentrations.
Fluctuations in these gases, plus changes in solar output are the major factors causing the changes in tropospheric temperature over the past 400,000 years.

21. Major Greenhouse Gases
Increases in average concentrations of three greenhouse gases in the troposphere between 1860 and 2004, mostly due to fossil fuel burning, deforestation, and agriculture.
Figure 20-5

22. Figure 20.5
Science: increases in average concentrations of three greenhouse gases—carbon dioxide, methane, and nitrous oxide—in the troposphere between 1860 and 2005, mostly because of fossil fuel burning, deforestation, and agriculture. The fluctuations in the CO2 curve (top) reflect seasonal changes in photosynthetic activity, which cause small differences between summer and winter concentrations of CO2. (Data from Intergovernmental Panel on Climate Change, National Center for Atmospheric Research, and World Resources Institute)
Fig. 20-5a, p. 467

23. Figure 20.5
Science: increases in average concentrations of three greenhouse gases—carbon dioxide, methane, and nitrous oxide—in the troposphere between 1860 and 2005, mostly because of fossil fuel burning, deforestation, and agriculture. The fluctuations in the CO2 curve (top) reflect seasonal changes in photosynthetic activity, which cause small differences between summer and winter concentrations of CO2. (Data from Intergovernmental Panel on Climate Change, National Center for Atmospheric Research, and World Resources Institute)
Fig. 20-5b, p. 467

24. Figure 20.5
Science: increases in average concentrations of three greenhouse gases—carbon dioxide, methane, and nitrous oxide—in the troposphere between 1860 and 2005, mostly because of fossil fuel burning, deforestation, and agriculture. The fluctuations in the CO2 curve (top) reflect seasonal changes in photosynthetic activity, which cause small differences between summer and winter concentrations of CO2. (Data from Intergovernmental Panel on Climate Change, National Center for Atmospheric Research, and World Resources Institute)
Fig. 20-5c, p. 467

25. CLIMATE CHANGE AND HUMAN ACTIVITIES
Evidence that the earth’s troposphere is warming, mostly because of human actions:
The 20th century was the hottest century in the past 1000 years.
Since 1900, the earth’s average tropospheric temperature has risen 0.6 C°.
Over the past 50 years, Arctic temperatures have risen almost twice as fast as those in the rest of the world.
Glaciers and floating sea ice are melting and shrinking at increasing rates.

26. CLIMATE CHANGE AND HUMAN ACTIVITIES
Warmer temperatures in Alaska, Russia, and the Arctic are melting permafrost releasing more CO2 and CH4 into the troposphere.
During the last century, the world’s sea level rose by cm, mostly due to runoff from melting and land-based ice and the expansion of ocean water as temperatures rise.

27. The Scientific Consensus about Future Climate Change
There is strong evidence that human activities will play an important role in changing the earth’s climate during this century.
Coupled General Circulation Models (CGCMs) couple, or combine, the effects of the atmosphere and the oceans on climate.

28. CGCM of the Earth’s Climate
Simplified model of major processes that interact to determine the average temperature and greenhouse gas content of the troposphere.
Figure 20-6

29. Green- house gases Land and soil biotoa Long-term storage
Sun
Troposphere
Cooling
from
increase
Green-
house
gases
Heat and
CO2 emissions
Aerosols
CO2 removal
by plants and
soil organisms
CO2 emissions from land clearing,
fires, and decay
Heat and
CO2 removal
Warming
from
decrease
Ice and snow cover
Shallow ocean
Land and soil biotoa
Figure 20.6
Natural capital: simplified model of some major processes that interact to determine the average temperature and greenhouse gas content of the troposphere and thus the earth’s climate.
Long-term
storage
Natural and human emissions
Deep ocean
Fig. 20-6, p. 469

30. Sun Stepped Art Troposphere Fig. 20-6, p. 469
Warming
from
decrease
CO2 removal by plants and soil organisms
Heat and
CO2 removal
Aerosols
Greenhouse
gases
Cooling from increase
CO2 emissions from land cleaning, fires, and decay
Heat and
CO2 emissions
Ice and snow cover
Shallow ocean
Land and soil biotoa
Long-term
storage
Natural and human emissions
Deep ocean
Stepped Art
Fig. 20-6, p. 469

31. The Scientific Consensus about Future Climate Change
Measured and projected changes in the average temperature of the atmosphere.
Figure 20-7

32. Figure 20.7
Natural capital degradation: comparison of measured changes in the average temperature of the atmosphere at the earth’s surface between 1875 and 2005 and the projected range of temperature increase during the rest of this century. QUESTION: If these projections are valid, list three ways this will affect your lifestyle. (Data from U.S. National Academy of Sciences, National Center for Atmospheric Research, and Intergovernmental Panel on Climate Change, Hadley Center for Climate Prediction and Research)
Fig. 20-7, p. 470

33. How Would You Vote?
To conduct an instant in-class survey using a classroom response system, access “JoinIn Clicker Content” from the PowerLecture main menu for Living in the Environment.
Do you believe that we will experience significant global warming during this century?
a. No. Claims for significant global warming during this century are based on unreliable climate models.
b. Yes. Even with the uncertainties, the models still indicate significant global warming during this century.

34. Why Should We Be Concerned about a Warmer Earth?
A rapid increase in the temperature of the troposphere during this century would give us little time to deal with its harmful effects.
As a prevention strategy scientists urge to cut global CO2 emissions in half over the next 50 years.
This could prevent changes in the earth’s climate system that would last for tens of thousands of years.

35. FACTORS AFFECTING THE EARTH’S TEMPERATURE
Some factors can amplify (positive feedback) and some can dampen (negative feedback) projected global warming.
There is uncertainty about how much CO2 and heat the oceans can remove from the troposphere and how long the heat and CO2 might remain there.
Warmer temperatures create more clouds that could warm or cool the troposphere.

36. Effects of Higher CO2 Levels on Photosynthesis
Increased CO2 in the troposphere can increase plant photosynthesis (PS) but:
The increase in PS would slow as the plants reach maturity.
Carbon stored by the plants would be returned to the atmosphere as CO2 when the plants die.
Increased PS decreases the amount of carbon stored in the soil.
Tree growth may temporarily slow CO2 emissions in the S. Hemisphere but is likely to increase CO2 emissions in the N. Hemisphere.

37. FACTORS AFFECTING THE EARTH’S TEMPERATURE
Aerosol and soot pollutants produced by human activities can warm or cool the atmosphere, but such effects will decrease with any decline in outdoor air pollution.
Warmer air can release methane gas stored in bogs, wetlands, and tundra soils and accelerate global warming.

38. EFFECTS OF GLOBAL WARMING
A warmer climate would have beneficial and harmful effects but poor nations in the tropics would suffer the most.
Some of the world’s floating ice and land-based glaciers are slowly melting and are helping warm the troposphere by reflecting less sunlight back into space.

39. EFFECTS OF GLOBAL WARMING
Between 1979 and 2005, average Arctic sea ice dropped 20% (as shown in blue hues above).
Figure 20-8

40. * Russia North Greenland pole Alaska (U.S.) Canada Fig. 20-8, p. 474
Figure 20.8
Science: satellite data showing Arctic sea ice between 1979 and The white area shows a moving average of Arctic sea ice between 2003 and The darker blue surrounding the white area is the moving average for the sea ice between 1979 and Between 1979 and 2005, average Arctic sea ice dropped 20%—a loss in area about the size of the U.S. state of Texas. The decrease in light-colored ice reflects less incoming solar energy back into space and can heat the troposphere. This in turn can cause more ice to melt and raise temperatures more in a runaway positive feedback cycle. QUESTION: List three impacts that this and continued melting of Arctic sea ice might have on your lifestyle. (Goddard Space Flight Center, NASA)
Alaska (U.S.)
Canada
Fig. 20-8, p. 474

41. Rising Sea Levels
During this century rising seas levels are projected to flood low-lying urban areas, coastal estuaries, wetlands, coral reefs, and barrier islands and beaches.
Figure 20-10

42. Mean Sea-Level Rises (centimeters)
High Projection
New Orleans,
Shanghai, and
other low-lying
cities largely
underwater
Mean Sea-Level Rises (centimeters)
Medium
Projection
More than a third of
U.S. wetlands underwater
Figure 20.10
Natural capital degradation: projected rise in global sea levels during this century. With such a rise, flooding and coastal erosion would be especially severe in heavily populated coastal areas of the tropics and warm temperate regions. Thirteen of the world’s largest 20 cities are located at sea level. QUESTION: List three ways that this projected rise in sea level could affect your lifestyle. (Data from Intergovernmental Panel on Climate Change, 2000)
Low Projection
Year
Fig , p. 475

43. Rising Sea Levels
Changes in average sea level over the past 250,000 years based on data from ocean cores.
Figure 20-9

44. present sea level (meters) Height above or below
Today’s sea level
present sea level (meters)
Height above or below
Height above or below present sea level (feet)
Figure 20.9
Changes in average sea level over the past 250,000 years based on data from cores removed from the ocean bottom. The coming and going of glacial periods (ice ages) largely determine the rise and fall of sea level. As glaciers melted and retreated since the peak of the last glacial period about 18,000 years ago (Figure 4-6, p. 89), the earth’s average sea level has risen about 125 meters (410 feet). (Adapted from Tom Garrison, Oceanography: An Invitation to Marine Science, 3/E, © Brooks/Cole)
Years before present
Present
Fig. 20-9, p. 475

45. Rising Sea Levels
If seas levels rise by 9-88cm during this century, most of the Maldives islands and their coral reefs will be flooded.
Figure 20-11

46. Changing Ocean Currents
Global warming could alter ocean currents and cause both excessive warming and severe cooling.
Figure 20-12

47. Warm, shallow current Cold, salty, deep current Fig. 20-12, p. 476
Figure 20.12
Natural capital: a connected loop of shallow and deep ocean currents stores CO2 in the deep sea and transports warm and cool water to various parts of the earth. This loop results when ocean water in the North Atlantic near Iceland is dense enough (because of its salt content and cold temperature) to sink to the ocean bottom, flow southward, and then move eastward to well up in the warmer Pacific. A shallower return current aided by winds then brings warmer and less salty—and thus less dense—water to the Atlantic. This water can cool and sink to begin the cycle again. A warmer planet would be a rainier one, which, coupled with melting glaciers, would increase the amount of freshwater flowing into the North Atlantic. This could slow or even jam this loop by diluting the saltwater and making it more buoyant (less dense) and less prone to sinking. Historical evidence suggests that such shifts in ocean currents have sometimes taken place in a matter of years or decades. QUESTION: How might your lifestyle be affected if this loop slows down in your lifetime?
Cold, salty,
deep current
Fig , p. 476

48. EFFECTS OF GLOBAL WARMING
A warmer troposphere can decrease the ability of the ocean to remove and store CO2 by decreasing the nutrient supply for phytoplankton and increasing the acidity of ocean water.
Global warming will lead to prolonged heat waves and droughts in some areas and prolonged heavy rains and increased flooding in other areas.

49. Effects on Biodiversity: Winners and Losers
Possible effects of global warming on the geographic range of beech trees based on ecological evidence and computer models.
Figure 20-13

50. Beech Future range Overlap Present range Fig. 20-13, p. 478
Figure 20.13
Natural capital degradation: possible effects of global warming on the geographic range of beech trees based on ecological evidence and computer models. According to one projection, if CO2 emissions doubled between 1990 and 2050, beech trees (now common throughout the eastern United States) would survive only in a greatly reduced range in northern Maine and southeastern Canada. Similarly, native sugar maples would likely disappear in the northeastern United States. QUESTION: What difference does it make if the range of beech trees changes? (Data from Margaret B. Davis and Catherine Zabinski, University of Minnesota)
Overlap
Present
range
Fig , p. 478

51. EFFECTS OF GLOBAL WARMING
In a warmer world, agricultural productivity may increase in some areas and decrease in others.
Crop and fish production in some areas could be reduced by rising sea levels that would flood river deltas.
Global warming will increase deaths from:
Heat and disruption of food supply.
Spread of tropical diseases to temperate regions.
Increase the number of environmental refugees.

52. DEALING WITH GLOBAL WARMING
Climate change is such a difficult problem to deal with because:
The problem is global.
The effects will last a long time.
The problem is a long-term political issue.
The harmful and beneficial impacts of climate change are not spread evenly.
Many actions that might reduce the threat are controversial because they can impact economies and lifestyles.

53. DEALING WITH GLOBAL WARMING
Two ways to deal with global warming:
Mitigation that reduces greenhouse gas emissions.
Adaptation, where we recognize that some warming is unavoidable and devise strategies to reduce its harmful effects.

54. How Would You Vote?
To conduct an instant in-class survey using a classroom response system, access “JoinIn Clicker Content” from the PowerLecture main menu for Living in the Environment.
Should we take serious action now to help slow global warming?
a. No. We should not waste money until we can develop strategies based on sound data.
b. Yes. The situation is serious and calls for a no-regrets strategy.

55. Cut fossil fuel use (especially coal)
Solutions
Global Warming
Prevention
Cleanup
Cut fossil fuel use (especially coal)
Remove CO2 from smoke stack and vehicle emissions
Shift from coal to natural gas
Store (sequester)
CO2 by planting trees
Improve energy efficiency
Sequester CO2 deep underground
Shift to renewable energy resources
Sequester CO2 in soil by using no-till cultivation
and taking cropland out
of production
Transfer energy efficiency and renewable energy technologies
to developing countries
Figure 20.14
Solutions: methods for slowing atmospheric warming during this century. QUESTION: Which five of these mitigation solutions do you think are the most important?
Reduce deforestation
Sequester CO2 in the deep ocean
Use more sustainable
agriculture and forestry
Repair leaky natural gas pipelines and facilities
Limit urban sprawl
Use animal feeds that reduce CH4 emissions by belching cows
Reduce poverty
Slow population growth
Fig , p. 481

56. Solutions: Reducing the Threat
We can improve energy efficiency, rely more on carbon-free renewable energy resources, and find ways to keep much of the CO2 we produce out of the troposphere.

57. How Would You Vote?
To conduct an instant in-class survey using a classroom response system, access “JoinIn Clicker Content” from the PowerLecture main menu for Living in the Environment.
Should we phase out the use of fossil fuels over the next fifty years?
a. No. Fossil fuels are too valuable to our society.
b. Yes. Fossil fuels release too much air pollution, including greenhouse gases.

58. Removing and Storing CO2
Methods for removing CO2 from the atmosphere or from smokestacks and storing (sequestering) it.
Figure 20-15

59. down from rig for deep ocean disposal Abandoned oil field Crop field
Spent oil reservoir is
used for Crop field
Tanker delivers
CO2 from plant
to rig
Coal
power
plant
Oil rig
Tree plantation
CO2 is pumped
down from rig for deep ocean disposal
Abandoned
oil field
Crop field
Switchgrass
CO2 deposit CO2 is pumped down to reservoir through abandoned oil field
Figure 20.15
Solutions: methods for removing carbon dioxide from the atmosphere or from smokestacks and storing (sequestering) it in plants, soil, deep underground reservoirs, and the deep ocean. QUESTION: Which two of these mitigation solutions do you think are the most important?
Spent oil reservoir is
used for CO2 deposit
= CO2 pumping
= CO2 deposit
Fig , p. 482

60. DEALING WITH GLOBAL WARMING
Governments can tax greenhouse gas emissions and energy use, increase subsidies and tax breaks for saving energy, and decrease subsidies and tax breaks for fossil fuels.
A crash program to slow and adapt to global warming now is very likely to cost less than waiting and having to deal with its harmful effects later.

61. WHAT IS BEING DONE TO REDUCE GREENHOUSE GAS EMISSIONS?
Getting countries to agree on reducing their greenhouse emissions is difficult.
A 2006 poll showed that 83% of Americans want more leadership from federal government on dealing with global warming.

62. International Climate Negotiations: The Kyoto Protocol
Treaty on global warming which first phase went into effect January, 2005 with 189 countries participating.
It requires 38 participating developed countries to cut their emissions of CO2, CH4, and N2O to 5.2% below their 1990 levels by 2012.
Developing countries were excluded.
The U.S. did not sign, but California and Maine are participating.
U.S. did not sign because developing countries such as China, India and Brazil were excluded.

63. How Would You Vote?
To conduct an instant in-class survey using a classroom response system, access “JoinIn Clicker Content” from the PowerLecture main menu for Living in the Environment.
Should the United States participate in the Kyoto Protocol?
a. No. Americans spend enough on environmental cleanup and should not take on the burden of this treaty.
b. Yes. We should participate, but only if India, China, and all other nations fairly participate.
c. Yes. As the leading emitter of greenhouse gases, the U.S. should set an example for other nations.

64. Moving Beyond the Kyoto Protocol
Countries could work together to develop a new international approach to slowing global warming.
The Kyoto Protocol will have little effect on future global warming without support and action by the U.S., China, and India.

65. Actions by Some Countries, States, and Businesses
In 2005, the EU proposed a plan to reduce CO2 levels by 1/3rd by 2020.
California has adopted a goal of reducing its greenhouse gas emission to 1990 levels by 2020, and 80% below by 2050.
Global companies (BP, IBM, Toyota) have established targets to reduce their greenhouse emissions 10-65% to 1990 levels by 2010.

66. • Drive a fuel-efficient car, walk, bike, carpool,
What Can You Do?
Reducing CO2 Emissions
• Drive a fuel-efficient car, walk, bike, carpool,
and use mass transit
• Use energy-efficient windows
• Use energy-efficient appliances and lights
• Heavily insulate your house and seal all drafts
• Reduce garbage by recycling and reuse
• Insulate your hot water heater
• Use compact fluorescent bulbs
• Plant trees to shade your house during summer
Figure 20.16
Individuals matter: ways to reduce your annual emissions of CO2. QUESTION: Which three of these actions do you think are the most important? What ones do you do?
• Set water heater no higher than 49°C (120°F)
• Wash laundry in warm or cold water
• Use low-flow shower head
• Buy products from companies that are trying to reduce their impact on climate
• Demand that the government make climate
change an urgent priority
Fig , p. 485

67. reserves with corridors Move people away from low-lying coastal areas
Develop crops that
need less water
Waste less water
Connect wildlife
reserves with corridors
Move people away
from low-lying
coastal areas
Stockpile 1- to 5-year
supply of key foods
Move hazardous material
storage tanks away
from coast
Prohibit new construction
on low-lying coastal areas
or build houses on stilts
Figure 20.17
Solutions: ways to prepare for the possible long-term effects of climate change. QUESTIONS: Which three of these adaptation solutions do you think are the most important?
Expand existing
wildlife reserves
toward poles
Fig , p. 485

68. OZONE DEPLETION IN THE STRATOSPHERE
Less ozone in the stratosphere allows for more harmful UV radiation to reach the earth’s surface.
The ozone layer keeps about 95% of the sun’s harmful UV radiation from reaching the earth’s surface.
Chlorofluorocarbon (CFCs) have lowered the average concentrations of ozone in the stratosphere.
In 1988 CFCs were no longer manufactured.

69. Ultraviolet light hits a chlorofluorocarbon
(CFC) molecule, such as CFCl3, breaking
off a chlorine atom and
leaving CFCl2.
Sun Cl
Once free, the chlorine atom is off
to attack another ozone molecule
and begin the cycle again.
UV radiation
A free oxygen atom pulls
the oxygen atom off
the chlorine monoxide
molecule to form O2.
The chlorine atom attacks
an ozone (O3) molecule,
pulling an oxygen atom off
it and leaving an oxygen
molecule (O2).
Figure 20.18
Natural capital degradation: simplified summary of how chlorofluorocarbons (CFCs) and other chlorine-containing compounds can destroy ozone in the stratosphere faster than it is formed. Note that chlorine atoms are continuously regenerated as they react with ozone. Thus, they act as catalysts, chemicals that speed up chemical reactions without being used up by the reaction. Bromine atoms released from bromine-containing compounds that reach the stratosphere also destroy ozone by a similar mechanism.
The chlorine atom
and the oxygen atom
join to form a chlorine monoxide molecule (ClO).
Summary of Reactions
CCl3F + UV Cl + CCl2F
Cl + O3 ClO + O2
Cl + O Cl + O2
Repeated
many times
Fig , p. 486

70. Sun UV radiation Cl C F Cl Cl O Cl Cl O O O Cl O O Stepped Art
Ultraviolet light hits a chlorofluorocarbon (CFC) molecule, such as CFCl3, breaking off a chlorine atom and leaving CFCl2.
Once free, the chlorine atom is off to attack another ozone molecule
and begin the cycle again.
UV radiation Cl C F Cl Cl O Cl
A free oxygen atom pulls
the oxygen atom off
the chlorine monoxide
molecule to form O2.
The chlorine atom attacks an ozone (O3) molecule, pulling an oxygen atom off it and leaving an oxygen
molecule (O2). Cl O O O Cl O
The chlorine atom and
the oxygen atom join to
form a chlorine monoxide
molecule (ClO). O
Stepped Art
Fig , p. 486

71. OZONE DEPLETION IN THE STRATOSPHERE
During four months of each year up to half of the ozone in the stratosphere over Antarctica and a smaller amount over the Artic is depleted.
Figure 20-19

72. OZONE DEPLETION IN THE STRATOSPHERE
Since 1976, in Antarctica, ozone levels have markedly decreased during October and November.
Figure 20-20

73. OZONE DEPLETION IN THE STRATOSPHERE
Ozone thinning: caused by CFCs and other ozone depleting chemicals (ODCs).
Increased UV radiation reaching the earth’s surface from ozone depletion in the stratosphere is harmful to human health, crops, forests, animals, and materials such as plastic and paints.

74. • Immune system suppression
Natural Capital Degradation
Effects of Ozone Depletion
Human Health
• Worse sunburn
• More eye cataracts
• More skin cancers
• Immune system suppression
Food and Forests
• Reduced yields for some crops
• Reduced seafood supplies from reduced phytoplankton
• Decreased forest productivity for UV-sensitive tree species
Wildlife
• Increased eye cataracts in some species
• Decreased population of aquatic species sensitive to UV radiation
• Reduced population of surface phytoplankton
Figure 20.21
Natural capital degradation: expected effects of decreased levels of ozone in the stratosphere. QUESTION: Which five of these effects do you think are the most important?
• Disrupted aquatic food webs from reduced phytoplankton
Air Pollution and Materials
• Increased acid deposition
• Increased photochemical smog
• Degradation of outdoor paints and plastics
Fig , p. 488
Global Warming
• Accelerated warming because of decreased ocean uptake of CO2 from atmosphere by phytoplankton and CFCs acting as greenhouse gases

75. Case Study: Skin Cancer
Structure of the human skin and relationship between radiation and skin cancer.
Figure 20-22

76. Squamous Cell Carcinoma
This long-wavelength
(low-energy) form of UV radiation causes aging of the skin, tanning, and sometimes sunburn. It penetrates deeply and may contribute to skin cancer.
This shorter-wavelength (high-energy) form
of UV radiation causes sunburn, premature
aging, and wrinkling. It is largely responsible
for basal and squamous cell carcinomas
and plays a role in malignant melanoma.
Ultraviolet A
Ultraviolet B
Thin layer of
dead cells
Hair
Squamous cells
Epidermis
Basal layer
Sweat
gland
Melanocyte cells
Dermis
Basalcell
Blood
vessels
Figure 20.22
Science: structure of the human skin and the relationships between ultraviolet (UV-A and UV-B) radiation and the three types of skin cancer. (Data and photos from the Skin Cancer Foundation)
Squamous Cell Carcinoma
Basal Cell Carcinoma
Melanoma
Fig , p. 489

77. PROTECTING THE OZONE LAYER
To reduce ozone depletion, we must stop producing all ozone-depleting chemicals.
Figure 20-23

78. Reducing Exposure to UV Radiation
What Can You Do?
Reducing Exposure to UV Radiation
• Stay out of the sun, especially between 10 A.M. and 3 P.M.
• Do not use tanning parlors or sunlamps.
• When in the sun, wear protective clothing and sun–
glasses that protect against UV-A and UV-B radiation.
• Be aware that overcast skies do not protect you.
• Do not expose yourself to the sun if you are taking
antibiotics or birth control pills.
Figure 20.23
Individuals matter: ways to reduce your exposure to harmful UV radiation. QUESTION: Which three of these actions do you think are the most important? Which ones do you do?
• Use a sunscreen with a protection factor of 15 or 30
anytime you are in the sun if you have light skin.
• Examine your skin and scalp at least once a month for
moles or warts that change in size, shape, or color or
sores that keep oozing, bleeding, and crusting over. If
you observe any of these signs, consult a doctor
immediately.
Fig , p. 490