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Chapter 19 Climate Change and Ozone Depletion (we can get along!)

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1 Chapter 19 Climate Change and Ozone Depletion (we can get along!)

2 Figure … …the Phillipines… Mount Pinatubo erupts!

3 “The effects of the eruption were felt worldwide. It ejected roughly 10 billion metric tonnes (10 cubic kilometres) of magma, and 20 million tons of SO 2, bringing vast quantities of minerals and metals to the surface environment. It injected large amounts of aerosols into the stratosphere—more than any eruption since that of Krakatoa in Over the following months, the aerosols formed a global layer of sulfuric acid haze. Global temperatures dropped by about 0.5 °C (0.9 °F), and ozone depletion temporarily increased substantially.” -WikipediaSO 2aerosols stratosphereKrakatoasulfuric acid°C°Fozone

4 Core Case Study: Studying a Volcano to Understand Climate Change  A NASA scientist predicted that the 1991 Philippines explosion would cool the average temperature of the earth by 0.5C o over a 15 month period and then return to normal by  His predictions were correct. Figure 20-1

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

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

7 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?

8 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.

9 PAST CLIMATE AND THE GREENHOUSE EFFECT Figure 20-2

10 Fig. 20-2a, p. 465 Thousands of years ago Average temperature over past 900,000 years Average surface temperature (°C)

11 Fig. 20-2c, p. 465 Average temperature over past 10,000 years = 15°C (59°F) Temperature change (C°) Temperature change over past 22,000 years Agriculture established End of last ice age Years ago

12 Fig. 20-2d, p. 465 Temperature change (C°) Temperature change over past 1,000 years Year

13 Fig. 20-2b, p. 465 Average surface temperature (°C) Year Average temperature over past 130 years

14 From website “Logicalscience. com”

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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. troposphere composition. temperature trends. temperature trends. greenhouse gas concentrations. greenhouse gas concentrations. solar, snowfall, and forest fire activity. solar, snowfall, and forest fire activity. Figure 20-3

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18 Ice Core Analysis

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20 National Ice Core Laboratory

21 Ice Core Analysis A “thin cut” slice of an ice core.

22 How Do We Know What Temperatures Were in the Past?  In 2005, an ice core showed that CO 2 levels in the troposphere are the highest they have been in 650,000 years. Figure 20-4

23 Fig. 20-4, p. 466 Concentration of carbon dioxide in the atmosphere (ppm) Variation of temperature (C°) from current level Thousands of years before present End of last ice age Temperature change Carbon dioxide 280 ppm in ppm in ppm in 2011

24 The Natural Greenhouse Effect  Four major factors shape the earth’s climate: The sun. The sun. Greenhouse effect warms the earth’s lower troposphere and surface because of the presence of greenhouse gases. Greenhouse effect warms the earth’s lower troposphere and surface because of the presence of greenhouse gases. Oceans store CO 2 and heat, evaporate and receive water, move stored heat to other parts of the world. Oceans store CO 2 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). Natural cooling process through water vapor in the troposphere (heat rises). Evaporation cools the Earth’s surfaceEvaporation cools the Earth’s surface Condensation in clouds releases heat in upper troposphereCondensation in clouds releases heat in upper troposphere

25 Major Greenhouse Gases  The major greenhouse gases in the lower atmosphere are, IN ORDER: 1. water vapor- most important greenhouse gas 2. carbon dioxide- greatest effect from human activities 3. methane- CH 4 -more powerful greenhouse gas per molecule than CO 2, but less of it than CO 2 4. nitrous oxide- N 2 O -comes from fertilizers and planting rice

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

27 Major Greenhouse Gases Increases in average concentrations of three greenhouse gases in the troposphere between 1860 and 2004, mostly due to  Fossil fuel burning (CO 2 & CH 4 )  Deforestation (CO 2 & N 2 O)  Agriculture (N 2 O) Figure 20-5

28 Fig. 20-5a, p ppm in ppm in ppm in 2011

29 Fig. 20-5b, p. 467

30 Fig. 20-5c, p. 467

31 CLIMATE CHANGE AND HUMAN ACTIVITIES  Evidence that the earth’s troposphere is warming: The 20 th century was the hottest century in the past 1000 years. The 20 th century was the hottest century in the past 1000 years. The 14 hottest years since 1861 have been since 1990 The 14 hottest years since 1861 have been since 1990

32 CLIMATE CHANGE Since 1900, the earth’s average tropospheric temperature has risen 0.6 C°. 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. Over the past 50 years, Arctic temperatures have risen almost twice as fast as those in the rest of the world.

33 CLIMATE CHANGE Glaciers and floating sea ice are melting and shrinking at increasing rates. Glaciers and floating sea ice are melting and shrinking at increasing rates. The range of specific species is moving to higher altitudes (up mountains) and higher latitudes. The range of specific species is moving to higher altitudes (up mountains) and higher latitudes. What happenes to the size of a species’ habitat as it moves up a mountain?What happenes to the size of a species’ habitat as it moves up a mountain?

34 Fig. 19-5a, p. 501

35 Fig. 19-5b, p. 501

36 Fig. 19-6, p. 501 Sept. 1979Sept Russia North pole Greenland North pole Greenland Alaska (U.S.) Canada

37 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. Next

38 Fig , p. 478 Present range Overlap Future range Beech

39 CLIMATE CHANGE AND HUMAN ACTIVITIES Warmer temperatures in Alaska, Russia, and the Arctic are melting permafrost, releasing more CO 2 and CH 4 into the troposphere (feedback loop…which kind, positive or negative?) Warmer temperatures in Alaska, Russia, and the Arctic are melting permafrost, releasing more CO 2 and CH 4 into the troposphere (feedback loop…which kind, positive or negative?) During the last century, the world’s sea level rose by cm, mostly due to runoff from melting of land-based ice and the expansion of ocean water as temperatures rise. During the last century, the world’s sea level rose by cm, mostly due to runoff from melting of land-based ice and the expansion of ocean water as temperatures rise.

40 Melting Permafrost- “Drunken Forests”

41

42 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. Coupled General Circulation Models (CGCMs) couple, or combine, the effects of the atmosphere and the oceans on climate.

43 C oupled G eneral C irculation M odel 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

44 Sun Stepped Art Aerosols Greenhouse gases Warming from decrease Cooling from increase CO 2 removal by plants and soil organisms CO 2 emissions from land cleaning, fires, and decay Heat and CO 2 removal Heat and CO 2 emissions Ice and snow cover Natural and human emissions Land and soil biota Long-term storage Deep ocean Shallow ocean Troposphere Fig. 20-6, p. 469 Factors that cool Factors that warm

45 Measured and projected changes in the average temperature of the atmosphere (2005).  ↑ 0.6 °C since 1900  Consensus projection is 5 °C ↑ by 2100 if we “do nothing”  Consensus is 4 °C ↑ could threaten civilization as we know it Figure 20-7

46 Fig. 20-7, p. 470 Most recent data suggests that temperatures are increasing even faster than the worst-case 2007 IPCC estimates

47 Why Should We Be Concerned about a Warmer Earth?  A rapid increase (non-linear response pattern) 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 CO 2 emissions 50% over the next 50 years…. “50/50” This could prevent changes in the earth’s climate system that might last for tens of thousands of years (due to many positive feedback loops) This could prevent changes in the earth’s climate system that might last for tens of thousands of years (due to many positive feedback loops)

48 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 CO 2 and heat the oceans can remove from the troposphere and how long the heat and CO 2 might remain there.  Warmer temperatures create more clouds that could warm or cool the troposphere.

49 Human Effects on the Carbon Cycle  Burning fossil fuels for energy Residential Residential Commercial Commercial Industrial Industrial Transportation Transportation  Clearing forests for agriculture & forest products  Covering land with pavement  Exponential population growth

50 Effects of Higher CO 2 Levels on Photosynthesis  Increased CO 2 in the troposphere can increase plant photosynthesis (PS) but: The increase in PS would slow as the plants reach maturity. The increase in PS would slow as the plants reach maturity. Carbon stored by the plants would be returned to the atmosphere as CO 2 when the plants die & decay Carbon stored by the plants would be returned to the atmosphere as CO 2 when the plants die & decay Increased PS decreases the amount of carbon stored in the soil. Increased PS decreases the amount of carbon stored in the soil.

51 FACTORS AFFECTING THE EARTH’S TEMPERATURE  Aerosol and soot pollutants produced by human activities can warm (SO 4 aerosols) or cool (soot particulates) 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 melting tundra soils and accelerate global warming (feedback?).

52 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 (“albedo”) back into space (feedback?).

53 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 (effects?) Next

54 Fig , p. 475 High Projection New Orleans, Shanghai, and other low-lying cities largely underwater Year Low Projection Medium Projection More than a third of U.S. wetlands underwater Mean Sea-Level Rises (centimeters) 4 inches 35 inches IPCC (2000) Projections “very likely” (90-99% confidence level)

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

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

57 Fig , p. 476 Warm, shallow current Cold, salty, deep current

58 Changing Ocean Currents  Global warming could alter ocean currents and cause both excessive warming and severe cooling. Next It has recently been shown that the potential shifting of ocean currents is less of a threat than we thought before.

59 EFFECTS OF GLOBAL WARMING  Oceans remove 25-30% of tropospheric CO 2  A warmer troposphere can decrease the ability of the ocean to remove and store CO 2 by decreasing the nutrient supply for calcareous phytoplankton that store CO 2 in their calcium carbonate (CaCO 3 ) shells, by potentially disrupting wind and ocean currents that provide nutrients via upwelling (feedback?) decreasing the nutrient supply for calcareous phytoplankton that store CO 2 in their calcium carbonate (CaCO 3 ) shells, by potentially disrupting wind and ocean currents that provide nutrients via upwelling (feedback?)

60 EFFECTS OF GLOBAL WARMING  Increasing the acidity of ocean water: CO 2 is dissolved in the ocean as carbonic acid, H 2 CO 3CO 2 is dissolved in the ocean as carbonic acid, H 2 CO 3 increased acidity interferes with calcareous phytoplankton shell formationincreased acidity interferes with calcareous phytoplankton shell formation Increased acidity dissolves existing deposits of CaCO 3 (feedback?)Increased acidity dissolves existing deposits of CaCO 3 (feedback?)  CO 2 is less soluble in warmer water (feedback?)

61 EFFECTS OF GLOBAL WARMING  Global warming will lead to prolonged heat waves and droughts in some areas (Africa, Asia, & Western USA) and prolonged heavy rains and increased flooding in other areas (Europe; more intense hurricanes and typhoons).  Between 1979 & 2002, the area of Earth’s land experiencing severe drought increased between 15% and 30%

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

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

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

65 Fig , p. 485 Move hazardous material storage tanks away from coast Connect wildlife reserves with corridors Develop crops that need less water Waste less water Move people away from low-lying coastal areas Stockpile 1- to 5-year supply of key foods Expand existing wildlife reserves toward poles (why?) Prohibit new construction on low-lying coastal areas or build houses on stilts Adaptation Strategies

66 Fig , p. 481 Cut fossil fuel use (especially coal) Shift from coal to natural gas Improve energy efficiency Shift to renewable energy resources Transfer energy efficiency and renewable energy technologies to developing countries Reduce deforestation Use more sustainable agriculture and forestry Limit urban sprawl Reduce poverty Slow population growth Remove CO 2 from smoke stack and vehicle emissions Store (sequester) CO 2 by planting trees Sequester CO 2 deep underground Sequester CO 2 in soil by using no-till cultivation and taking cropland out of production Sequester CO 2 in the deep ocean Repair leaky natural gas pipelines and facilities Use animal feeds that reduce CH 4 emissions by belching cows Solutions Global Warming PreventionCleanup

67 Solutions: Reducing the Threat  We can improve energy efficiency improve energy efficiency rely more on carbon-free renewable energy resources rely more on carbon-free renewable energy resources find ways to keep much of the CO 2 we produce out of the troposphere (Carbon Capture & Sequestration a.k.a. CCS) find ways to keep much of the CO 2 we produce out of the troposphere (Carbon Capture & Sequestration a.k.a. CCS)

68 Removing and Storing CO 2  Methods for removing CO 2 from the atmosphere or from smokestacks and storing (sequestering) it. Figure 20-15

69 Fig , p. 482 Tree plantation Coal power plant Tanker delivers CO 2 from plant to rig Oil rig CO 2 is pumped down from rig for deep ocean disposal Spent oil reservoir is used for CO 2 deposit Abandoned oil field Crop field Spent oil reservoir is used for Crop field Switchgrass = CO 2 deposit = CO 2 pumping CO 2 deposit CO 2 is pumped down to reservoir through abandoned oil field

70 Problems with CCS  Unproven technology  Promotes continued use of fossil fuels  Requires huge government subsidies that draw funds from other solutions  There can be no leaks for any reason

71 DEALING WITH GLOBAL WARMING  Governments can tax greenhouse gas emissions and/or carbon- based energy use tax greenhouse gas emissions and/or carbon- based energy use increase subsidies and tax breaks for saving energy increase subsidies and tax breaks for saving energy decrease subsidies and tax breaks for fossil fuels. decrease subsidies and tax breaks for fossil fuels.

72 DEALING WITH GLOBAL WARMING  A crash program to slow and adapt to climate change now is very likely to cost less than waiting and having to deal with its harmful effects later.  As usual, “An ounce of prevention is worth a pound of cure”

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

74 International Climate Negotiations: The Kyoto Protocol (1997) Treaty on global warming which first phase went into effect January, 2005 with 189 countries participating. 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 CO 2, CH 4, and N 2 O to 5.2% below their 1990 levels by It requires 38 participating developed countries to cut their emissions of CO 2, CH 4, and N 2 O to 5.2% below their 1990 levels by Developing countries were excluded. Developing countries were excluded. The U.S. and Australia did not sign, but California (world’s 6 th largest economy) and Maine are participating. The U.S. and Australia did not sign, but California (world’s 6 th largest economy) and Maine are participating. U.S. did not sign because developing countries such as China, India and Brazil were excluded.U.S. did not sign because developing countries such as China, India and Brazil were excluded.

75 Moving Beyond the Kyoto Protocol  Countries could work together to develop a new international approach to slowing global warming (much has changed since 1997) The Kyoto Protocol will have little effect on future global warming without support and action by the U.S., China, and India. The Kyoto Protocol will have little effect on future global warming without support and action by the U.S., China, and India.  November 29- December 9, 2011: Durban, South Africa Climate Change Conference See Forbes article /climate-treaty-would-actually-be-good-for- business/ See Forbes article /climate-treaty-would-actually-be-good-for- business/

76 Actions by Some Countries, States, and Businesses  In 2005, the EU proposed a plan to reduce CO 2 levels by 1/3 rd by  Global companies (BP, IBM, Toyota) have established targets to reduce their greenhouse emissions to 10-65% below 1990 levels by 2010.

77 Actions by Some Countries, States, and Businesses  California has adopted a goal of reducing its greenhouse gas emission to 1990 levels by 2020, and 80% below by  The US EPA refused California’s request to set tough new standards(!)

78 Actions by Some Countries, States, and Businesses  BP spent $20 million to lower it’s greenhouse gas emissions to 10% below 1990 levels. Took 3 years, from 1998 to 2001 Took 3 years, from 1998 to 2001 Saved $250 million Saved $250 million

79 Fig , p. 485 Reducing CO 2 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 (why?) Insulate your hot water heater Use compact fluorescent bulbs Plant trees to shade your house during summer 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 What Can You Do?

80 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 Arctic is depleted. Figure 20-19

81 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. The ozone layer keeps about 95% of the sun’s harmful UV radiation from reaching the earth’s surface. Chlorofluorocarbons (CFCs) have lowered the average concentrations of ozone in the stratosphere. Chlorofluorocarbons (CFCs) have lowered the average concentrations of ozone in the stratosphere. In 1988 CFCs were no longer manufactured, due to the Montreal Protocol In 1988 CFCs were no longer manufactured, due to the Montreal Protocol

82 Sun Once free, the chlorine atom is off to attack another ozone molecule and begin the cycle again. A free oxygen atom pulls the oxygen atom off the chlorine monoxide molecule to form O 2. The chlorine atom and the oxygen atom join to form a chlorine monoxide molecule (ClO). UV radiation Cl C F The chlorine atom attacks an ozone (O 3 ) molecule, pulling an oxygen atom off it and leaving an oxygen molecule (O 2 ). Cl O O O O O O O O O Ultraviolet light hits a chlorofluorocarbon (CFC) molecule, such as CFCl 3, breaking off a chlorine atom and leaving CFCl 2. O Fig , p. 486 Stepped Art

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

84 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. 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.

85 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 Disrupted aquatic food webs from reduced phytoplankton Air Pollution and Materials Increased acid deposition Increased photochemical smog Degradation of outdoor paints and plastics Global Warming Accelerated warming because of decreased ocean uptake of CO 2 from atmosphere by phytoplankton and CFCs acting as greenhouse gases Effects of Ozone Depletion Natural Capital Degradation Fig , p. 488

86 Fig , p. 489 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. Epidermis Squamous Cell Carcinoma Basal Cell Carcinoma Melanoma Sweat gland Dermis Squamous cells Thin layer of dead cells Basal layer Melanocyte cells Blood vessels Ultraviolet B Ultraviolet A Hair Basal cell

87 PROTECTING THE OZONE LAYER  To reduce ozone depletion, we must stop producing all ozone-depleting chemicals. Next

88 Fig , p. 490 What Can You Do? 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. 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. Reducing Exposure to UV Radiation


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