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Climate Change and Ozone Depletion 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? 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? The topic of climate change is like a puzzle with many different pieces—oceans, the atmosphere, ecosystems, polar ice, natural and human influences. Scientists have been working on this puzzle for more than a century, and while there are still gaps in our knowledge, most experts feel we have the puzzle is complete enough to show that human activities are having an adverse effect on our planet. We will look at many of those puzzle pieces, the evidence behind them, and the conclusions we can draw from them. 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 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. Scientists have a good understanding of what has changed earth’s climate in the past: • Incoming solar radiation is the main climate driver. Its energy output increased about 0.1% from 1750 to 1950, increasing temperatures by 0.2°F (0.1°C) in the first part of the 20th century. But since 1979, when we began taking measurements from space, the data show no long-term change in total solar energy, even though Earth has been warming. • Repetitive cycles in Earth’s orbit that occur over tens of thousands of years can influence the angle and timing of sunlight. •In the distant past, drifting continents make a big difference in climate over millions of years by changing ice caps at the poles and by altering ocean currents, which transport heat and cold throughout the ocean depths. •Huge volcanic eruptions can cool Earth by injecting ash and tiny particles into the stratosphere. •Changes in the concentration of greenhouse gases, which occur both naturally and as a result of human activities, also influence Earth’s climate 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. PAST CLIMATE AND THE GREENHOUSE EFFECT Figure 20-2 Average surface temperature (°C) Average temperature over past 900,000 years Thousands of years ago Fig. 20-2a, p. 465 Average surface temperature (°C) Average temperature over past 130 years Year Fig. 20-2b, p. 465 Temperature change (C°) Temperature change over past 22,000 years Agriculture established End of last ice age Average temperature over past 10,000 years = 15°C (59°F) Years ago Fig. 20-2c, p. 465 Temperature change (C°) Temperature change over past 1,000 years Year Fig. 20-2d, p. 465 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 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 Temperature End of change last ice age Thousands of years before present Variation of temperature (C°) from current level Concentration of carbon dioxide in the atmosphere (ppm) Carbon dioxide Fig. 20-4, p. 466 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). 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. Increasing greenhouse gases trap more “Greenhouse effect” heat 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 CO2 comes from a variety of sources. For example, plants take up carbon dioxide in the air to make wood, stems, and leaves, and then release it back into the air when the leaves fall or the plants die. The concern today is that fossil fuel use is putting huge amounts of CO2 in the atmosphere at a rate faster than the climate system can adapt to. Could the warming be natural? Fig. 20-5a, p. 467 Fig. 20-5b, p. 467 Fig. 20-5c, p. 467 Earth is getting warmer by virtually every measure we know, and the temperature has been well above normal for more than 25 years. Although increases of 1.0-1.6°F (0.6-0.9°C) over the last century or so may not sound very threatening, remember that’s a global average. The warming is stronger over land than over oceans and in the higher latitudes than in the tropics. 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. 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 10-20 cm, mostly due to runoff from melting and land-based ice and the expansion of ocean water as temperatures rise. 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. 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 Sun Troposphere Aerosols Greenhouse gases Cooling from increase Warming from decrease CO2 removal by plants and soil organisms CO2 emissions from land clearing, fires, and decay Heat and CO2 removal Heat and CO2 emissions Ice and snow cover Shallow ocean Land and soil biotoa Natural and human emissions Long-term storage Deep ocean Fig. 20-6, p. 469 Sun Troposphere Greenhouse gases Aerosols Warming from decrease Cooling from increase CO2 removal by plants and soil organisms CO2 emissions from land cleaning, fires, and decay Heat and CO2 removal 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 The Scientific Consensus about Future Climate Change Measured and projected changes in the average temperature of the atmosphere. Figure 20-7 Fig. 20-7, p. 470 How Would You Vote? 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. 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. 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. 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. 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. 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 landbased glaciers are slowly melting and are helping warm the troposphere by reflecting less sunlight back into space. EFFECTS OF GLOBAL WARMING Between 1979 and 2005, average Arctic sea ice dropped 20% (as shown in blue hues above). Figure 20-8 Russia * North pole Greenland Alaska (U.S.) Canada Fig. 20-8, p. 474 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 Sea-level rise projections : a few inches to a few feet •2 ft: U.S. would lose 10,000 square miles •3 ft: Would inundate Miami •Affects erosion, loss of wetlands, freshwater supplies •Half of the world’s population lives along coasts •Big question: Ice sheets The oceans will continue their rise in the coming century. The IPCC’s best estimates range from a few inches to a few feet by 2100. If the rise is 2 feet, the US could lose 10,000 square miles, If they rise three, they will inundate Miami and most of coastal Florida. Sea-level rise also increases coastal erosion and the loss of coastal wetlands, and saltwater spoils freshwater drinking supplies. Coastal populations become even more vulnerable to storm surge and flooding. Considering that half of the world’s population lives near coasts, sea-level rise is a serious concern. Mean Sea-Level Rises (centimeters) High Projection New Orleans, Shanghai, and other low-lying cities largely underwater Medium Projection More than a third of U.S. wetlands underwater Low Projection Year Fig. 20-10, p. 475 Rising Sea Levels Changes in average sea level over the past 250,000 years based on data from ocean cores. Figure 20-9 Height above or below present sea level (meters) Years before present Height above or below present sea level (feet) Today’s sea level Present Fig. 20-9, p. 475 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 Changing Ocean Currents Global warming could alter ocean currents and cause both excessive warming and severe cooling. Figure 20-12 Warm, shallow current Cold, salty, deep current Fig. 20-12, p. 476 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. 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 Beech Future range Overlap Present range Fig. 20-13, p. 478 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. Snow and ice reflect the sun’s energy back to space. Without this white cover, more water can evaporate into the atmosphere where it acts as a greenhouse gas, and the ground absorbs more heat. Snow and ice are melting at rates unseen for thousands of years. In Glacier National Park, for example, there were 150 glaciers in 1850. Today, there are 26. Effects on precipitation Increased warmth has also affected living things. For example, the Japanese keep very detailed records on the blossoming of their Tokyo cherry trees, so they know they are blooming 5 days earlier on average than they were 50 years ago. Computer models Aspen, CO Forecast: Partly cloudy today High : 28°F Low: 13°F Increasing clouds over night. Colder tomorrow. Climate models are not only used to look at how climate might change, they’re also used to figure out WHY it’s changing. When models are run with only natural influences from the sun and volcanic eruptions, they say that during the latter half of the 20th century, we would have expected little change from normal conditions (the blue line). Only the addition of human emissions (greenhouse gases, sulfates, and ozone) produce the model results in red that most closely reproduce the black line of actual observations. Why should we care? Global average temperatures are expected to increase by about 2-13°F (1-7°C) by the end of the century. That may not sound like a lot, so what’s the big deal? The problem is that small changes in global average temperature can lead to really large changes in the environment. Let’s look at some of the expected changes. 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. 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. How Would You Vote? 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 noregrets strategy. Solutions Global Warming Prevention Cut fossil fuel use (especially coal) Shift from coal to natural gas Cleanup Remove CO2 from smoke stack and vehicle emissions Store (sequester) CO2 by planting trees 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 Sequester CO2 deep underground Sequester CO2 in soil by using no-till cultivation and taking cropland out of production Sequester CO2 in the deep ocean Repair leaky natural gas pipelines and facilities Use animal feeds that reduce CH4 emissions by belching cows Slow population growth Fig. 20-14, p. 481 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. How Would You Vote? 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. Removing and Storing CO2 Methods for removing CO2 from the atmosphere or from smokestacks and storing (sequestering) it. Figure 20-15 Spent oil reservoir is used for Crop field Oil rig Tanker delivers CO2 from plant to rig CO2 is pumped down from rig for deep ocean disposal Coal power plant Abandoned oil field Tree plantation Switchgrass Crop field CO2 deposit CO2 is pumped down to reservoir through abandoned oil field Spent oil reservoir is used for CO2 deposit = CO2 pumping = CO2 deposit Fig. 20-15, p. 482 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. 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. 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. 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. 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. 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 • 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. 20-16, p. 485 Develop crops that need less water Waste less water Connect wildlife reserves with corridors Move hazardous material storage tanks away from coast Move people away from low-lying coastal areas Stockpile 1- to 5-year supply of key foods Prohibit new construction on low-lying coastal areas or build houses on stilts Expand existing wildlife reserves toward poles Fig. 20-17, p. 485 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. Ultraviolet light hits a chlorofluorocarbon (CFC) molecule, such as CFCl3, breaking off a chlorine atom and leaving CFCl2. Sun Cl UV radiation The chlorine atom attacks an ozone (O3) molecule, pulling an oxygen atom off it and leaving an oxygen molecule (O2). Summary of Reactions CCl3F + UV Cl + CCl2F Cl + O3 ClO + O2 Repeated Cl + O Cl + O2 many times 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 O2. The chlorine atom and the oxygen atom join to form a chlorine monoxide molecule (ClO). Fig. 20-18, p. 486 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. Sun Cl Cl C Cl F UV radiation Cl Cl O O The chlorine atom attacks an ozone (O3) molecule, pulling an oxygen atom off it and O O O leaving an oxygen molecule (O2). Cl A free oxygen atom pulls the oxygen atom off the chlorine monoxide Cl molecule to form O2. O O The chlorine atom and the oxygen atom join to form a chlorine monoxide molecule (ClO). Cl O O Stepped Art O Fig. 20-18, p. 486 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 OZONE DEPLETION IN THE STRATOSPHERE Since 1976, in Antarctica, ozone levels have markedly decreased during October and November. Figure 20-20 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. 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 • Disrupted aquatic food webs from reduced phytoplankton Air Pollution and Materials • Increased acid deposition • Increased photochemical smog • Degradation of outdoor paints and plastics Fig. 20-21, p. 488 Global Warming • Accelerated warming because of decreased ocean uptake of CO2 from atmosphere by phytoplankton and CFCs acting as greenhouse gases Case Study: Skin Cancer Structure of the human skin and relationship between radiation and skin cancer. Figure 20-22 This long-wavelength This shorter-wavelength (high-energy) form (low-energy) form of UV of UV radiation causes sunburn, premature radiation causes aging of Ultraviolet Ultraviolet aging, and wrinkling. It is largely responsible A the skin, tanning, and for basal and squamous cell carcinomas B sometimes sunburn. It and plays a role in malignant melanoma. penetrates deeply and may contribute to skin cancer. Thin layer of dead cells Squamous cells Basal layer Hair Epidermis Sweat gland Melanocyte cells Dermis Basal cell Blood vessels Squamous Cell Carcinoma Basal Cell Carcinoma Melanoma Fig. 20-22, p. 489 PROTECTING THE OZONE LAYER To reduce ozone depletion, we must stop producing all ozone-depleting chemicals. Figure 20-23 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. • 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. 20-23, p. 490