Pollution, Sustainability, & Climate Change PDF

Section III Pollution, Sustainability, & Climate Change Human actions have a tremendous impact on Earth’s of global climate change: the large-scale physical and biosphere and the global climate, and their effects are biogeochemical changes...

Section III Pollution, Sustainability, & Climate Change Human actions have a tremendous impact on Earth’s of global climate change: the large-scale physical and biosphere and the global climate, and their effects are biogeochemical changes that have been taking place becoming more apparent by the year. In this first part on Earth at an accelerating rate over the past several of Section III, we will focus on air and water pollution, decades. particularly pollution that results from conventional energy production (e.g., emissions from power plants). WATER POLLUTION We will then examine human energy consumption: Throughout the world, many people routinely consume the types of renewable and non-renewable energy water from surface water such as rivers and streams sources, as well as their advantages and disadvantages. and from dug wells. Sometimes the same body of water Finally, we will discuss the nature, causes, and effects serves as the supply for drinking, bathing, washing, FIGURE 32 Texas Pentathlon - TX, TX Point-source and non-point source water pollution. Source: Mississippi Department of Environmental Quality 2024–2025 Science Pentathlon Resource Guide 51 cooking, and the disposal of human and other waste. Such a body of water can easily become polluted and a source of infectious diseases. Between 1 billion and 2 billion people on Earth, most of them in the developing world, do not have access to safe drinking water. In addition, bodies of water have been degraded in ways that cause significant damage to the environment. The two main categories of water pollution are: 6 Point-source pollution is released from distinct, confined locations, such as a particular factory or the pipe leading from a sewage treatment plant. 6 Non-point source pollution is contamination If too much nitrogen and phosphorus are present, they can that collects from large areas, such as an overfeed a body of water, leading to eutrophication, the entire farm or a farming region, a suburban excessive growth of algae due to an oversupply of nutrients. community with many lawns and septic By Felix Andrews (Floybix) - Own work, CC BY-SA 3.0, https://commons. systems, or runoff from parking lots. wikimedia.org/w/index.php?curid=1092921 It is important to differentiate the type of source material will decompose, and bacteria will grow on because it can help in controlling pollutant inputs it, using oxygen to survive and thereby depleting to waterways. For example, if a municipality can available oxygen. Food scraps, human waste, and Texas Pentathlon - TX, TX determine that the bulk of waterway pollution is animal waste are all oxygen-demanding waste that can coming from one or two point sources, it can target the enter the water supply. owners of those specific point sources. It is much more difficult to control pollution from non-point sources. Inorganic Compounds Inorganic compounds are chemical compounds that Types of Water Pollutants don’t come from animals or plants. Perhaps the most Pathogens important are the two elements most likely to limit Pathogens—parasites, bacteria, viruses—are growth in the receiving lake or stream are nitrogen and responsible for a number of diseases that can be phosphorus. If too much nitrogen and phosphorus are contracted by humans or other organisms who come in present, they can overfeed the body of water, leading to contact with or ingest the water containing them. Large- eutrophication, the excessive growth of algae due to scale disease outbreaks from municipal water systems an oversupply of nutrients. Eventually the algae die and are relatively rare in the United States, but they do decompose, oxygen is depleted from the water, and the occur occasionally. Disease outbreaks from municipal fish population declines. The major terrestrial sources water systems are, however, relatively common in many of nitrogen are farm runoff, sewage treatment plants, parts of the developing world. Pathogens can enter the and acid precipitation; and the sources of phosphorus water supply from both point and non-point sources. A are naturally occurring rocks and minerals, fertilizer malfunctioning sewage treatment plant or septic system runoff, and, in the past, detergents. can be point sources of pathogens entering into rivers or lakes. Wildlife can also contaminate reservoirs with Other inorganic pollutants can come from non-point disease-causing organisms. Worldwide, the major water- sources such as acid precipitation (nitrate and sulfate) borne diseases are cholera and hepatitis. or point sources such as by-products of sewage treatment (chloride) or industrial plants (metals). Oxygen-demanding Waste Metals such as lead, copper, arsenic, and mercury are Oxygen-demanding waste is material that contains among the most toxic water pollutants. In the early organic matter, such as leaves and twigs that get 2000s, mercury received a great deal of attention as an washed into a body of water during a rainstorm. The inorganic water contaminant of global proportions. 2024–2025 Science Pentathlon Resource Guide 52 Organic Pollutants Persistent Organic Pollutants (POP) are toxic chemicals created by humans for industrial purposes that persist in the environment for decades or longer and can accumulate in organisms, including humans, through food webs. One group of organic compounds that is causing many problems is polychlorinated biphenyls, or PCBs, which are highly toxic and carcinogenic. PCBs were used in manufacturing plastics and insulating electrical transformers until 1979. Although they are no longer manufactured or used in the United States, because of their persistence, they are still present in the environment. A pelican is coated in oil following the Deepwater Horizon oil spill in 2010 Sediments By Louisiana GOHSEP - Flickr: Oiled Pelicans, CC BY-SA 2.0, https:// Sediments include nonchemical pollutants such as commons.wikimedia.org/w/index.php?curid=30525946 sand, silt, and clay that become mobilized when soil is disturbed. Housing and shopping center development Perhaps the greatest culprits are crude oil and other and road construction, along with agriculture, are petroleum products, which are highly toxic to many major sources of sediment. When a dam is constructed, marine organisms, including birds, mammals, and sediments settle out of the unmoving water. If the fish, as well as the algae and microorganisms that form water is later remobilized, a great deal of sediment will the base of the aquatic food chain. Oil is a persistent Texas Pentathlon - TX, TX end up in downstream water. Sediment can clog fish substance that can spread across the water for gills and otherwise hinder fish from obtaining oxygen, hundreds of miles and leave a thick, viscous covering particularly bottom dwellers such as oysters or clams. on land that is extremely difficult to remove. In addition, increased sediment in the water column reduces the infiltration of sunlight, which can reduce Oil and other petroleum products enter the oceans the productivity of aquatic plants. through multiple sources, most notably from spills from off-shore drilling and oil tankers. Perhaps the Thermal Pollution most notorious recent spill was the Deepwater Horizon Any time human beings alter water flow so that the oil spill of 2010 in the Gulf of Mexico. In that case, water moves more slowly, receives more sunlight, 210 million gallons of oil covered miles of ocean and or enters a shallower waterway, the temperature of coastline and dramatically impacted one of the most the water is likely to increase. Water is also heated productive marine ecosystems on Earth. Cleanup when it is used for cooling in industrial processes efforts continue to the present day. Cleanup includes and electricity generation (e.g., fossil fuel-fired and physical methods such as floating booms to keep a nuclear power plants). The result is thermal pollution. spill from spreading, followed by skimming oil from Increasing water temperature reduces the amount of the water’s surface. It also includes the use of chemical oxygen that can be dissolved in the water. At the same dispersants that break down the oil into particles small time, in warmer waters organisms normally increase enough to be broken down by sunlight and bacteria. their respiration rate, which means they will use more oxygen and further reduce the dissolved oxygen in the Solid Waste Pollution water. Increased respiration rate is a stress that can Though the dumping of solid waste in open waters make organisms more susceptible to disease. Increased has been reduced since the early 1980s, it is hard to water temperature may also affect reproduction. walk along a beach without finding at least a few bottles, cigarette butts, or food packages. Various Ocean and Shoreline Pollution forms of solid waste can be dropped on beaches by Although our major focus in this section has been on negligent people or washed into the ocean from open fresh water, pollution of Earth’s oceans and shorelines landfills and travel long distances before they are is an environmental problem of major proportions. washed up on another beach far from where they 2024–2025 Science Pentathlon Resource Guide 53 started. Not only is such beach garbage unsightly, oxygen-demanding food components or inorganic it can be dangerous to both marine organisms and contaminants from soaps and detergents, is much less people. Toxic medical waste poses a threat to people on harmful to the environment. Wastewater from sources the beach, particularly children, and plastic holders for other than toilets, called gray water, is sometimes beverage six-packs and plastic bags, for instance, are reintroduced into the environment without treatment known to strangle many animals. And the extent and for purposes such as watering lawns. dangers of plastic pollution goes far beyond just this. Plastic debris in landfills or waterbodies can degrade Human sewage is an oxygen-demanding material that over time into microplastics, particles smaller than may contain pathogenic organisms and high levels of 5 mm, or nanoplastics, particles smaller than 0.0001 phosphate, nitrate, and other compounds. Whether raw mm. Microplastics have been found to be a potential sewage is dumped into a free-flowing river or stream health risk in both animals and humans, which can and “treated” naturally or passed through a human- intake them via eating contaminated seafood, as well made system, such as a sewage treatment plant, septic as from multiple other sources.12 system, or solar aquatic system, the basic processes are the same: bacteria break down the organic matter into Wastewater Treatment carbon dioxide and inorganic compounds like nitrate The term wastewater refers to all water from houses and phosphate; dissolved oxygen levels in the water are and buildings that is destined for a sewage treatment reduced; and eventually BOD goes down; and oxygen plant or septic system. In fact, wastewater is highly levels recover. Wastewater treatment facilities replicate varied. Obviously, wastewater from toilets contains this natural process to varying degrees, usually more material that is harmful and must be treated before quickly. In addition, decomposing the sewage in a it can be returned to the environment. But water treatment plant prevents polluting a natural body of water. Texas Pentathlon - TX, TX from sinks and showers, while possibly containing FIGURE 33 Wastewater treatment process. Source: Encyclopedia Britannica 2024–2025 Science Pentathlon Resource Guide 54 In a traditional sewage treatment plant, which might can be produced by natural sources, such as volcanoes be used in most municipalities in developed countries, and fires, or by human sources such as automobiles, wastewater treatment is accomplished in two phases, power plants, and factories. Air pollution usually refers primary and secondary treatment. Primary treatment to pollution in the troposphere, roughly the first ten removes 40 to 50 percent of the solid waste material. kilometers (six miles) of the atmosphere above Earth’s Solid material that settles out during the process is surface. Tropospheric pollution is sometimes called eventually dried and classified as sludge. Sludge usually ground-level pollution. Other layers of the Earth’s contains significant amounts of metals, particularly if atmosphere also contain pollution, but for now we will the effluent comes from a municipality that includes focus on the troposphere. industrial businesses. After removal of the sludge, the water undergoes secondary treatment, which effectively Major Air Pollutants accelerates the breakdown of organic matter that would The atmosphere, like most of the oceans, is considered occur if the sewage were left to decompose naturally. a global commons that is protected by governments At the end of secondary treatment, roughly 85 to 90 that regulate the activities producing air pollutants. percent of the original pollutants in the water have been Environmental science was used in the development removed. The water is disinfected to kill pathogens and of these regulations, including the U.S. Clean Air then returned to the river or lake it originally came from Act (CAA) of 1970. As part of the development of the and is once more part of the water cycle. CAA, scientists identified the six most common and widely harmful air pollutants, and these pollutants Improvements in U.S. Water Quality remain a primary focus of air pollution regulation and Water quality in the United States has improved in are the criteria by which the air in cities, regions, and most categories over the past few decades. Forty to states is judged to be significantly polluted. These six Texas Pentathlon - TX, TX fifty years ago, many harbors and waterways were criteria pollutants are sulfur dioxide, nitrogen oxides, badly polluted. The Clean Water Act, passed in 1972 carbon monoxide, lead, particulate matter, and ground- and amended a number of times since then, the Safe level ozone. Drinking Water Act of 1986, and the Water Resources Development Acts (1986−92) have worked in concert Sulfur Dioxide to protect surface water by managing the water supply, Sulfur dioxide (SO2) is a gas released in nature by wastewater, flood control, navigation on waterways, volcanic eruptions and by humans, primarily through and hydroelectric power. The Clean Water Act also the burning of fossil fuels such as coal and oil. All requires the establishment of Water Quality Standards living things contain various amounts of sulfur, and that place an upper limit on the concentration of thus fossil fuels formed from long-ago plants and specific pollutants in major water bodies. To achieve animals. This sulfur is released when fossil fuels are these standards, the Clean Water Act also requires the burned. SO2 harms mammalian respiratory systems, establishment of a Total Maximum Daily Load for including reducing lung function. While this is each pollutant—the maximum amount of a pollutant particularly harmful for people with asthma or other that is allowed to enter a waterbody—that is based on respiratory illnesses, it can irritate the lungs of anyone. the total amount of the pollutant discharged from point Sulfur dioxide can also harm plants, as SO2 in the sources (factories, wastewater treatment facilities, etc.) atmosphere can undergo a chemical reaction to form and non-point sources (atmospheric deposition, farms, sulfuric acid, one of the main components of acid rain. and other runoff from the land). Nitrogen Oxides The atmosphere is 78 percent nitrogen gas (N2), and all AIR POLLUTION AND THE combustion in the atmosphere leads to the formation of ATMOSPHERE a wide variety of nitrogen oxides (NOX). Atmospheric Air pollution is the emission of compounds into the NOX gases can be harmful themselves, but they also atmosphere at levels high enough to harm plants, play a role in forming ozone and other common animals (including humans), and buildings (and/or components of urban air pollution. Like SO2, NOX can other nonliving materials) as well as adversely impact undergo chemical reactions in the atmosphere to form the structure and function of ecosystems. Air pollution nitric acid, which also is harmful to ecosystems. 2024–2025 Science Pentathlon Resource Guide 55 Carbon Monoxide Carbon monoxide (CO) is a colorless, odorless gas that is formed during incomplete combustion of most organic matter, such as gasoline, which makes it a major part of automobile emissions. Carbon monoxide binds with hemoglobin (an oxygen transporting protein in the mammalian body) and interferes with the transport of oxygen, which—if exposure is high enough—can lead to health impacts such as dizziness, headaches, confusion, loss of consciousness, and even death. Lead Lead (Pb) is a naturally occurring element that is part of the Earth’s crust and can be found in air, water, and soil. Airborne lead, such as when lead was used as an Air pollution has a significant impact on human health. additive in gasoline and emitted from tailpipes, is only Particulate matter is suspected of causing lung cancer and one of the ways that lead may impact humans. The other lung ailments. use of leaded gasoline ended in the U.S. in the 1970s and globally in 2021 when the final stocks of leaded Ground-Level Ozone gas were used up in Algeria. Lead can also be found Photochemical air pollutants (e.g., ozone) are a in lead-based paint and lead plumbing, both of which class of air pollutants that are formed as a result of can still be found in some homes and communities. action by the Sun on compounds that are oxides, such Texas Pentathlon - TX, TX Lead, regardless of the source, can adversely impact an as nitrogen oxide and sulfur oxide. Photochemical animal’s blood production, producing anemia but, even pollutants are among the compounds that comprise more critically, it has been found to have a wide range photochemical smog, a comprehensive term that of adverse neurological impacts, particularly on young refers to the haze that appears over cities, particularly children. cities like Los Angeles where surrounding mountains will trap the smog. There are many photochemical Particulate Matter pollutants, but ozone (O3)—three oxygen molecules Particulate matter refers to solid or liquid particles bound together—is the most important for its suspended in air. Particulates come from most positive and negative impacts. Ozone forms in the combustion products, including wood, coal, oil, and stratosphere, where it absorbs ultraviolet light and gasoline. They are most commonly known as a class of thereby removes harmful ultraviolet radiation, keeping pollutants resulting from “dirty burning” fuels such as it from reaching the Earth. In the troposphere (closer coal and oil or low-efficiency wood stoves (which are to the Earth’s surface), ozone is an oxidant harmful to a major source of air pollution in many northern states plants and animals. and countries). Forest fires and volcanoes are two natural sources of particulates. While criteria pollutants are common air pollutants with known adverse health impacts and are regulated Particulates range in size from 0.01 microns to 100 under their own part of the Clean Air Act—the microns in diameter, which is approximately the National Ambient Air Quality Standards—there are thickness of the average human hair. Particulates of many other air pollutants, such as mercury (primarily various sizes are suspected of causing lung cancer produced through the burning of coal for energy), and other lung ailments in humans. Particulates also that adversely impact human health and ecosystems. block sunlight. If the atmospheric concentration Many of these pollutants are regulated under different of particulates is high enough, as it is immediately parts of the Clean Air Act, such as the Hazardous Air following a large forest fire or a volcanic eruption, Pollutant section. Regardless of the regulatory method, photosynthesis in the region can even be reduced. the initial step is for scientists to set standards for how much of a certain pollutant should be allowed in the 2024–2025 Science Pentathlon Resource Guide 56 atmosphere (e.g., the ambient air) or can be emitted by human activity—and most of it usually is—a from a source (e.g., a car or a power plant). significant percentage of air pollution comes from natural sources. Volcanoes, forest and grassland fires, Secondary Pollutants living plants, and dead plants all release compounds Most of the criteria pollutants are classified as primary that can be classified as pollutants. Volcanoes release pollutants because they remain in the form that they SO2, particulates, CO, and NOX. Forest fires release are emitted from the power plant, factory, car, or particulates, CO, and NOX. The summer of 2023 other source. However, some pollutants, such as smog provided a critical example of how wildfires can and acid rain, result from chemical reactions in the impact air quality as wildfires in the Pacific Northwest atmosphere in which primary pollutants are transformed and, in particular, northern Canada produced high into secondary pollutants. Solar energy powers some levels of particulate matter and other pollutants, of these reactions, such as the formation of smog, causing extremely unhealthy air quality in much and they rely on atmospheric water and the higher of North America and even impacting Europe. In temperatures found near the Earth’s surface. Smog is addition, the 2023 Canadian wildfires more than a secondary pollutant—smog is not emitted from a doubled the previous annual high for Canada’s level of smokestack or tailpipe. Instead, like sulfuric acid and carbon dioxide emissions. While we can classify the nitric acid, it is created by chemical reactions in the pollutants produced from these wildfires as “naturally atmosphere. produced,” a 2023 study concluded that climate change—mainly due to human-caused greenhouse gas Natural Sources of Air Pollution emissions—more than doubled the likelihood of the Though we tend to think of air pollution as caused extreme weather conditions in eastern Canada.13 Texas Pentathlon - TX, TX FIGURE 34 The formation of smog. Source: University of Calgary: Energy Education 2024–2025 Science Pentathlon Resource Guide 57  FIGURE 35 Texas Pentathlon - TX, TX Causes of air pollution. Source: NPS Atmospheric (Thermal) Inversion later—are primary energy sources. However, the Atmospheric temperature contributes to the formation electricity that we use to power our lights, electric of smog. Normally, temperature decreases with vehicles, electronics, and much of our modern society increasing altitude. But when a warm layer of air is a secondary energy source that is converted from at mid-altitude blankets a cooler layer below it, a primary source. Electricity-generating powerplants an atmospheric inversion occurs, and pollutants convert the chemical potential energy of a number of released at ground level—whether natural or fuels into electrical potential energy (electricity). The anthropogenic—accumulate in the troposphere, basic process is the same, regardless of the fuel. Non- often causing a severe pollution event. Atmospheric renewable energy source-powered plants use coal, oil, inversions are particularly common in cities where natural gas, or radioactive fuel rods to produce steam, high concentrations of vehicle exhaust and industrial which turns a turbine, which turns a generator. The emissions are easily trapped by an inversion layer. electricity generated is then transported along power lines and converted to heat energy for cooking, kinetic ENERGY USE AND SOURCES energy for running motors, and radiant energy for powering lights. As we will see later, renewable energy Generating Electricity sources—such as wind and the flow of water in a The non-renewable energy sources discussed above— hydroelectric dam—can also be used to drive a turbine. and the renewable energy sources we will discuss 2024–2025 Science Pentathlon Resource Guide 58  FIGURE 36 Electricity generation from an electric turbine Source: EIA Nonrenewable Energy Sources pressure and temperature and eons of time compacted Coal the organic matter into the dense, energy-rich carbon Between 160 million and 400 million years ago, material that we know as coal. Because of this origin, Texas Pentathlon - TX, TX tropical plants growing in swamps and marshes coal is called a fossil fuel. There are several different were covered by sediments. Because the rich organic kinds of coal, representing the different amounts of matter was buried, decomposition was limited. High time and pressure needed for formation; classified FIGURE 37 Environmental impacts of coal mining. 2024–2025 Science Pentathlon Resource Guide 59 from lesser to greater energy content, they are peat, carbon into the atmosphere when burned, although lignite, bituminous coal, and anthracite. only 85 percent as much as coal when producing the equivalent amount of energy. Oil spills of all sizes are Because coal is very energy dense and plentiful, it is also a significant source of water pollution. ideal for the generation of electricity and for industrial processes such as making steel. Coal is mined in Natural Gas two general ways: deep shaft mining and surface Natural gas, which is 80 to 95 percent methane mining. In deep-shaft mining, tunnels are dug into (CH4), occurs with oil in the ground. Because it is the Earth, perhaps as deep as 2,000 feet, and people less dense than oil, it lies above it in the rock strata. descend into the shafts, dislodge the coal, and bring it Relative to coal and oil, natural gas contains fewer to the surface. Surface mining comes in many forms, impurities and therefore gives rise to virtually no SO2 from digging a pit to removing a mountaintop. Coal and particulates during combustion. However, CH4 extraction can result in major adverse environmental is a potent greenhouse gas (twenty-five times more impacts, including the emissions of several harmful efficient at trapping heat from the Earth than CO2). air pollutants, including sulfur dioxides, particulate The leaking of natural gas during extraction is a major matter, and mercury, and mining degrades water cause of CH4 pollution. However, natural gas only quality of nearby streams, creating an environmental produces 60 percent as much CO2 as coal for the same problem called acid mine drainage. amount of energy produced, making it, overall, a lower contributor to greenhouse gas emissions. Petroleum Petroleum—the mixture of hydrocarbons, water and, Hydraulic Fracturing usually, sulfur that occurs in underground deposits—is Hydraulic fracturing extracts previously untapped also a fossil fuel. In contrast to coal, petroleum formed oil and natural gas reserves. Hydraulic fracturing (or Texas Pentathlon - TX, TX from the remains of ocean-dwelling plankton that fracking) involves injecting high-pressure streams were preserved roughly 65 to 250 million years ago. of water, sand, and chemicals into bedrock to create It occurs in certain locations with porous rocks, such fractures in the rock formation to extract trapped oil and as sandstone, that are capped by nonporous rock. The gas. This technique, coupled with horizontal drilling, petroleum filled the pore spaces in the rock, geologic has allowed previously unreachable reservoirs of oil and events deformed the rock layers so that they formed natural gas to be tapped. Fracking has been the major a trap, and after millions of years, the petroleum reason that natural gas has overtaken coal as the second migrated upward toward the highest point in the rock. most used energy source in the U.S., behind petroleum. Petroleum must be extracted with wells, drilled on There are several environmental and human health land and under water, and pumped from the ground, concerns related to fracking. The fluid used to “frack” except in specific locations where it flows out under the bedrock contains chemicals such as methanol, pressure from drilling. Petroleum contains natural ethylene glycol, and propargyl alcohol that are gas as well as oil; when the gas is separated out, the hazardous to human health.14 The extent to which these remaining product is known as liquid petroleum or chemicals are impacting water resources is uncertain. crude oil. Crude oil is further refined into a variety of However, it is known that large-scale fracking compounds that are separated by weight, including, operations use a tremendous amount of water—about among others, gasoline, diesel fuel, and kerosene. 1.5 trillion gallons of water since 2011—and fracking a single well can use 40 million gallons of water or more.15 Oil Large-scale fracking projects can dramatically lower Petroleum is currently the greatest energy source in key aquifers. And much of this large-scale fracking, and the United States, although natural gas has closed the massive use of water, is taking place in areas like Texas, gap. It is extremely convenient, relatively energy dense, where droughts are becoming more common. and clean burning compared to coal. Sulfur and other impurities can be removed from oil before combustion, Nuclear Power although the lower-sulfur-content oils are generally Nuclear power is a relatively clean means of more expensive to manufacture and thus more expensive electricity generation but produces radioactive waste. to purchase. Since it is a fossil fuel, oil will release 2024–2025 Science Pentathlon Resource Guide 60  FIGURE 38 Texas Pentathlon - TX, TX The fracking process. Source: NRDC Nuclear power does not directly provide energy for extremely rapid radioactive decay, or the splitting of consumers but is used to generate electricity. The the uranium atoms into more atoms. fuel itself is uranium, a natural element that occurs in relatively small concentrations in a wide variety Each time an atom splits (a fission reaction), a small of rocks, including shale and sandstone. As much as amount of heat is given off. When a number of pellets two thousand pounds of uranium must be mined to representing trillions of uranium atoms are bundled produce seven pounds of uranium oxide for nuclear together into fuel rods, a great deal of heat is released. fuel. Surface mining removes large amounts of the In the reactor, the heat warms water, which eventually host rock. The uranium is extracted from the rock and becomes steam, which turns a turbine just as in any concentrated, and the remaining material is left in slag other electricity generating station. piles. The western U.S. and parts of Canada are two Uranium is the most concentrated of all the energy locations where commercial operations mine uranium sources we have considered. A pound of enriched for nuclear fuel. uranium, which is smaller than a baseball, has the After extraction, the uranium ore is enriched, a energy content of a million gallons of gasoline. Ten tons process that includes, among other things, the removal of enriched uranium oxide contain roughly the same of naturally occurring impurities so that the ore might energy as 260,000 tons of coal. We can say that there is contain 2−3 percent uranium oxide. The enriched 26,000 times more energy in uranium than in coal. uranium is processed into pellets, which are then put Nuclear power plants do not produce any air pollution into hollow fuel rods approximately six feet high. A when they are operating, so proponents of nuclear typical nuclear reactor might contain 75 to 100 bundles power consider it “clean” energy. However, fossil of fuel rods. A pellet of uranium oxide undergoes fuels are used during other parts of nuclear power 2024–2025 Science Pentathlon Resource Guide 61  FIGURE 39 Texas Pentathlon - TX, TX Diagram of a nuclear reactor. Source: World Nuclear Association generation, which does produce air pollution— have contributed to the extensive protests against for example when the power plant is constructed, nuclear power in the United States: when uranium ore is mined and processed, when used fuel rods are transported from the plant to 6 On March 28, 1979, at the Three Mile Island their ultimate storage location, and when the plant plant in Pennsylvania, human error caused a is decommissioned. (Nuclear power plants have a cooling water valve to be closed, which led life of approximately fifty years before the level of to a loss of coolant around the nuclear core. radioactivity in the plant and obsolescence of the The core overheated and suffered damage, structure require them to be shut down.) Nevertheless, and a small amount of radiation was released even with all these releases taken into account, from the plant. This event, compounded by emissions of carbon dioxide per kilowatt-hour of the coincidental release of the film The China electricity generated are at most 60 grams for a nuclear Syndrome, in which a nuclear plant suffered a power plant, compared to 800 to 1,100 grams for a major “meltdown,” led to widespread public modern coal-burning power plant. fear and anger. One result was a huge amount of scrutiny given to the safety of nuclear power Three accidents in widely separated parts of the world plants and some of the early assumptions 2024–2025 Science Pentathlon Resource Guide 62  that had been made about the relative risks of operating them. 6 An even more serious accident occurred on April 26, 1986, at the nuclear power plant in Chernobyl, Ukraine. An explosion and fire exposed the core of one of the reactors, and at least thirty-one plant workers and firefighters died immediately of acute radiation exposure— with many hundreds, and perhaps thousands, dying over a longer period of time from the radiation exposure. The Chernobyl accident has been intensively studied and has been characterized as a “runaway” reactor incident. The accident occurred during a special test of the plant when, in violation of safety regulations, operators deliberately disconnected emergency cooling systems and removed the control rods. With no control rods and no coolant, the nuclear reactions went out of control, and the plant overheated. Shortly afterward, the plant exploded, and fires began to burn. Because the A clean-up crew works to remove radioactive contamination control rods were made of flammable graphite, at Three Mile Island after the accident there in 1979. Texas Pentathlon - TX, TX the fire was worse than it would have been in a plant with water control rods. In 1978, the U.S. Department of Energy began In March 2011, a major earthquake occurred examining a site at Yucca Mountain, Nevada, about a 6 off the coast of Japan that resulted in a tsunami hundred miles northwest of Las Vegas, as a possible hitting the main island of Honshu, killing over long-term repository for the country’s spent nuclear 18,000 people and flooding the reactors of the fuel and other high-level radioactive waste. In the early Fukushima nuclear power plant. This caused 2000s, it seemed almost certain that the repository radioactive leakage that forced more than would be constructed; however, that has not happened. 150,000 people to evacuate. The area around Political pressure from Nevada, protests from the the nuclear plant remains off limits, and it is Western Shoshone people living in the area (who estimated that it will take up to forty years to also identify Yucca Mountain as a sacred site), and finish the decontamination work.16 some scientific uncertainty over whether the site was geologically stable enough to house the waste for While nuclear power does not produce fossil-fuel thousands of years has, as of 2023, seemingly put an emissions, it does produce extremely dangerous end to that plan. If and where radioactive waste will radioactive waste that requires special and secure be consolidated into a few or one single storage site is storage. After a period of time, nuclear fuel rods become currently uncertain. “spent,” meaning they do not have enough fuel left to produce enough heat to effectively generate electricity. Renewable Energy The rods still contain highly radioactive fission From the system analysis perspective introduced in fragments and will remain a threat to humans and other Section I, fossil fuels are a resource pool with many organisms for tens of thousands of years. At present, outputs (human energy use), but no real inputs (any nuclear power plants are required to store spent fuel “new” coal, oil, or natural gas will not be available rods at the plant itself, in pools of water at least twenty to use for many millions of years). So, like a lake that feet deep that act as a shield from the radiation. From is being drained, but not being replenished, the use the spent fuel pools, rods are moved to onsite cement of fossil fuels is not sustainable. Instead, sustainable storage canisters (called dry cask storage), which can fit energy use is based on the use of renewable energy two to six dozen spent fuel rod assemblies each. sources—sources like the Sun and the wind—that 2024–2025 Science Pentathlon Resource Guide 63 cannot be depleted (at least as long as our Sun and Earth power. And because the Sun heats the Earth unevenly, survive). Other energy sources, such as biofuels like causing air to move from one location to another, it wood, are potentially renewable if they are managed is responsible for generating wind. Water- and wind- so that their use is balanced by the creation of new based energy sources can therefore be considered resources, e.g., balancing the logging and regrowth forms of indirect solar energy. of a forest. And the sustainability of energy use, in general, can be improved by using less energy through The only significant sources of energy that are not improving energy efficiency and energy conservation. solar based are nuclear, geothermal, and tidal. Energy from the Sun also comes to us directly. Every day, Direct and Indirect Solar Energy the Earth is bathed with solar energy. The amount Almost all energy on Earth, both conventional and reaching the top of the Earth’s atmosphere—roughly alternative, derives from the Sun. Fossil fuels are 1,370 watts per square meter each day—is called the the product of plants and animals that were buried solar constant. Because the atmosphere reflects and millions of years ago. The energy stored in these absorbs a good fraction of this energy, only about 200 organisms was gained either directly or indirectly watts arrive at the Earth’s surface near the equator, through photosynthesis. The Sun is also responsible though this amount may vary between 50 and 300 for evaporating water, which is an essential aspect of watts, depending on the location and the time of year. the hydrologic cycle. In the hydrologic cycle, water This is the energy that is potentially available for use moves from the oceans to the land, where it falls to the by people; it is known as the solar potential. Of course, ground as precipitation. This precipitation is the source solar energy is not available in every location every of all rivers and streams, which provide hydrologic day. On cloudy days, there is much less solar input to Texas Pentathlon - TX, TX FIGURE 40 Average annual solar radiation in the U.S. (kilowatt-hours per square meter per day). Source: NREL 2024–2025 Science Pentathlon Resource Guide 64  where it circulates in copper tubing. Painted black and sometimes put behind glass, the tubing absorbs energy from the Sun and transfers it to the water. The water then returns to the building, where it enters the hot water heater tank and is heated further or, if it is already hot enough, is available for use. Energy from the Sun can be converted directly to electrical energy with a photovoltaic solar cell. A photovoltaic solar cell makes use of the fact that very thin, ultra-clean layers of silicon dioxide (SiO2) generate an electrical current when they are exposed The Andasol solar power station in Spain. to direct sunlight. Contemporary photovoltaic cells are made of SiO2 combined with a very small amount the surface of the Earth than on sunny days; at night of a metal, such as arsenic or antimony, to increase solar input is zero. And different regions of the world the voltage of the output. An individual photovoltaic have different solar potential. In the United States, the cell will produce about one or two watts. Normally Southwest has the greatest solar potential, with solar twenty-four or more cells are joined together and often energy available at least 90 percent of the time. mounted on the rooftops of buildings. Passive Solar Energy The electricity from photovoltaic cells can run directly Passive solar refers to the collection of solar to an appliance through wires from the roof or can be energy directly from the rays of the Sun without an stored in batteries that are then used for power. The Texas Pentathlon - TX, TX intermediate technology such as a pump or blower. electricity can also be converted to the voltage of the Passive solar energy has been harnessed for thousands power grid and exported to the grid. of years for purposes ranging from home heating to Wind Energy cooking. Positioning a house so that it absorbs the most A wind turbine is a device that converts the kinetic energy and using dark materials on the roof or walls of energy of wind to the potential energy of electricity. a building so that more solar energy is absorbed than A contemporary wind turbine may be as tall as ~100 reflected are passive solar techniques. In the Northern meters, with blades 40 to 75 meters long. The average Hemisphere, constructing a house with windows along a turbine will generate over 843,000 kWh per month, south-facing wall will allow the Sun’s rays that are close which is enough energy for over 940 average U.S. to the horizon for much of the day during the winter homes.17 The most rapidly growing sites for wind- months to penetrate and warm the house. Sometimes it generated electricity are offshore wind parks that are is advantageous to install construction material with a clusters of windmills within a few miles of the coastline. great deal of thermal inertia—in other words, material that once heated, remains hot, and once cooled, remains cool. Stone and concrete have thermal inertia; wood and glass do not. A southern exposure room with stone walls and a stone floor will heat up on sunny winter days and retain that heat long after the Sun has set. Active Solar Energy Systems that utilize energy from the Sun with the assistance of fans, blowers, and pumps are active solar systems. Active solar energy is used primarily for two main applications: heating hot water and generating electricity. In a house with an active solar A windfarm near Palm Springs, California. water heater, before cold water enters the water heater, By Conn, Kit at the English-language Wikipedia, CC BY-SA 3.0, https:// a small electric pump pushes water onto the roof, commons.wikimedia.org/w/index.php?curid=5395739 2024–2025 Science Pentathlon Resource Guide 65  FIGURE 41 Texas Pentathlon - TX, TX Average annual solar radiation in the U.S. (kilowatt-hours per square meter per day). Source: NREL There are at least forty offshore wind farms in operation at the time the energy is harnessed. Solar and wind in Northern Europe, with over two thousand total wind energy can also provide electricity in remote locations turbines. However, there are only two offshore wind where there are no transmission lines. A correctly farms in the U.S. although more have been proposed or constructed and positioned house can take advantage are in the permitting or construction process. of passive solar energy to produce energy savings and offset pollution and carbon dioxide for decades Advantages and Disadvantages of Solar without any additional energy input. And large wind and Wind Energy turbines—especially in agricultural areas—have been The use of solar and wind energy has the potential found to be compatible with other land uses, such as to provide heat and/or electricity without producing farming and animal grazing. any air or water pollution or fossil carbon dioxide 2024–2025 Science Pentathlon Resource Guide 66  FIGURE 42 Texas Pentathlon - TX, TX Environmental impacts of solar and wind energy. Nevertheless, there are disadvantages to both. The Sun disadvantage—many people do not like living in a doesn’t shine, and the wind doesn’t blow all the time. place where they can see or hear the turbines. That means that some of the energy that is produced when conditions are good will need to be stored for One environmental objection to wind power has when conditions are not ideal. Storage requires large- come from the fact that an estimated 10,000 to 40,000 scale battery production, which remains difficult and birds die each year in collisions with windmills in the expensive. Also, as we have discussed previously, United States. New designs and the purposeful location energy is lost with each new step added to an energy of towers away from migration paths have reduced system—including the storage of energy in a battery bird deaths, but some bird deaths are an inevitable and use of the energy from a battery. The batteries by-product of wind power. For comparison, many used to store the energy are similar to the batteries millions of birds die in collisions with communication in smart phones, computers, and electric cars—they towers, buildings, and windows in both commercial require lithium, cobalt, and other minerals that buildings and residences. The number of bird deaths require mining, which leads to environmental harm from collisions with wind towers is relatively small. and environmental health and justice issues for those That said, newer objections have been raised about the workers mining the materials. possibility of off-shore wind farms harming migratory and endangered whales off the New England coast. Once wind turbines are manufactured and installed, the only energy input to them comes from the wind, Hydroelectric Power a sustainable, renewable, and free resource. Some The kinetic energy of water can be used to generate energy is required to maintain the windmill (travel to electricity. Hydroelectric power, or hydropower, the wind park and service of the moving parts), but the use of river water to generate electricity, is one of relative to the energy generated, these energy costs two renewable energy sources that are widely used in are minimal. However, wind farms have an aesthetic the United States today. (The other is the combustion of biomass.) Hydropower currently accounts for 2024–2025 Science Pentathlon Resource Guide 67 approximately 28.7 percent of the total renewable river hydro plants are mostly small scale, generating electricity, and 6.2 percent of the total electricity around one megawatt at peak capacity, enough to generated in the U.S. supply electricity to about a thousand homes. Because the water is not stored in a reservoir, run-of-the-river As water falls over a vertical distance, the potential electricity generation is dependent on natural water energy stored is released as kinetic energy. A flow, which means that supply is variable during the hydroelectric power plant captures this kinetic energy year, limiting its usefulness during the dry summer and uses it to turn a turbine, just as the kinetic energy months, when electricity demands are at their highest. of steam turns a turbine in a coal-fired electricity generating plant. The turbine transforms the kinetic Although run-of-the river hydro has much less impact energy into electrical energy. The amount of electricity on aquatic plants and animals than water impoundment that can be generated at a particular power plant because natural high- and low-flow periods continue, depends on both the vertical distance through which species that swim upstream will find at least part of the water falls and the flow rate, or amount of water their path impeded by the presence of even a run-of- that flows past a certain point per unit of time. There the-river electricity generation facility. Fish ladders, are two main types of hydroelectric generation: run-of- a series of pools and pipes designed like ascending the-river and water impoundment. steps that allow fish to travel upstream around a hydro dam are sometimes installed, but some species find it In run-of-the-river hydro generation, water is diverted difficult to utilize them, and some predatory species from a river, passed through a narrow channel, and have learned to watch the fish ladders for prey. In directed toward a turbine. After the water goes through addition, the water intake for any dam, run-of-the- the turbine, it is returned to the river. Run-of-the- Texas Pentathlon - TX, TX FIGURE 43 Water impoundment hydroelectric dam. Source: U.S. Department of Energy 2024–2025 Science Pentathlon Resource Guide 68 river, or water impoundment is a potentially dangerous place for any number of species, including humans. A more reliable source of water for hydropower is water impoundment, or storing water in a reservoir behind a dam. The basic principle of dammed hydropower is similar to that of run-of-the-river, but the flow of water is controlled. Water impoundment is more common than run-of-the-river hydro because it allows for electricity generation on demand, rather than only during periods of heavy rainfall and water flow. In addition, it can produce more power than run-of-the-river generation; the large series of Hydro Quebec dams near James Bay, Canada, for example, can generate 7,300 MW at peak, far more than any Roughly two-thirds of the biomass energy used in the U.S. run-of-the-river station could produce. comes from wood and wood products. Nevertheless, water impoundment has many negative plants, animals, and other organisms, and their environmental effects. First, when water that was waste products—contains a great deal of energy that formerly free flowing in a river is stored, an area of originally derived from the Sun and was concentrated land is flooded. This may entail the loss of hundreds in what we know as biomass. The potential energy of square miles of forest, rich bottom land ideal for remaining when these organisms die and decompose, agriculture, canyons that have great aesthetic or or in their waste products, is available to do useful Texas Pentathlon - TX, TX archeological value, or wild river recreation. Ecological work. Wood—including charcoal—animal dung, plant communities are lost, and people are often displaced remains, and any decomposition products from plants, from their homes, communities, and livelihoods. such as ethanol, are all sources of biomass energy. Hydro dams can also create the conditions for the Municipal solid waste (MSW) incineration—burned mercury to be converted from elemental mercury, in waste-to-energy facilities—is also a source of which is relatively harmless in ecosystems, to energy. Together, the variety of biomass products methyl mercury, which concentrates in fatty tissue accounts for roughly 37 percent of all renewable and bioaccumulates in fish and ultimately humans, energy consumed in the U.S. potentially causing serious health problems. Biomass is burned as wood, charcoal, or dung to heat Even without the problems noted above, large-scale homes or water or to cook food; combusted in wood- hydro dam projects alter the ecology of the water fired power plants to produce electricity; and, after and land areas both upstream from the dam, where being fermented to ethanol (from corn) and mixed with large areas of a former river have been flooded, and gasoline, used to power vehicles. Roughly two-thirds downstream. For example, certain species, such as of the biomass energy used in the U.S. comes from salmon, steelhead trout, and freshwater clams and wood and wood products. Almost one-quarter comes mussels, have life cycles that depend on seasonal from MSW. Agricultural wastes and methane collected variations in water flow. Some plant species, such as the from MSW landfills each comprise 5 percent of cottonwood tree, depend on sand bars created by natural biomass energy. In many parts of the world, especially flooding to carry out the reproductive phases of their developing countries, animal dung is the most common life cycles. Researchers have documented changes in source of biomass energy. the abundance of such species that have resulted from interrupted flow, lack of flooding downstream, and other Modern Carbon vs Fossil Carbon conditions stemming from the creation of a dam. Biomass is organic matter, and thus it contains a great deal of carbon. You might think, therefore, that burning Biomass Around the World it would contribute to pollution and global warming in Biomass energy is the potential energy contained the same way that burning fossil fuel does. However, the in organic matter. The Earth’s organic matter— age of the carbon in biomass makes its effects different. 2024–2025 Science Pentathlon Resource Guide 69 The carbon in biomass was in the atmosphere until fairly recently (months ago for products like corn, a few hundred years ago for a large tree). This carbon is called modern carbon, in contrast to the carbon in fossil fuels, which is called fossil carbon. Although all carbon is chemically the same and can combine with oxygen to form carbon dioxide, the use of fossil carbon is more deleterious to the environment because its use adds to the amount of carbon in the atmosphere. Modern carbon, on the other hand, was already in the atmosphere until it was removed by plants relatively recently. Moreover, if new vegetation regrows A geothermal power plant in Iceland. Twenty-seven percent of where crops or trees were cut down, the new vegetation Iceland’s energy comes from geothermal sources. will take up a good deal of the carbon dioxide during photosynthesis. (Some older forests actually remove importance. Geothermal energy is the heat produced very little carbon from the atmosphere because their from the radioactive decay of elements deep in the primary productivity is not much greater than their Earth. Geothermal energy will not deplete for as long respiration.) As long as the amount of biomass removed as there is an Earth, and it is relatively inexpensive is replaced by new growth, there is no net effect on the to tap. The energy can also be used directly to heat carbon cycle or global CO2 concentrations from burning water, or it can be used as the primary energy source to biomass. In contrast, any time fossil carbon is burned, produce electricity by creating steam to power turbines, there is a net increase in global CO2 concentrations. without the greenhouse gases or other pollutants that are Texas Pentathlon - TX, TX produced by burning fossil fuels. However, it can emit Ethanol other localized dangerous gases, and most importantly, Ethanol is the most common biomass fuel, or biofuel. it is geographically limited to those areas that are It is made by fermentation, the decomposition of the geologically active. Iceland, a country known for its sugars and starches in biomass by yeasts, bacteria, and active volcanoes, gets 100 percent of its electricity from molds that results in the production of alcohol. More renewable energy sources: 73 percent hydroelectric and than 1.8 billion gallons of ethanol are made and used 27 percent geothermal.18 in the U.S. each year. Of that, 92 percent is derived from corn and corn by-products. Ethanol is mixed Tidal generation plants are operating in areas of Maine with gasoline, usually at a ratio of 1:10. It boosts the and Washington state; Brittany, France; Nova Scotia, octane of the gasoline and helps oxygenate it, which Canada; and other locations. However, tidal energy reduces certain air pollutants. In addition, it has other is not currently a major energy source. One reason beneficial effects, such as absorbing moisture in the is that, in most areas, the difference in water level gasoline to prevent freezing. Finally, it reduces the between high and low tides is not great enough to amount of gasoline used and replaces fossil carbon provide enough kinetic energy to generate a sufficient with modern carbon that was removed from the amount of electricity. In addition, to harness tidal atmosphere the year the corn was harvested. Some energy and convert it to electricity, power stations opponents of using ethanol in automobile fuel point must be built directly on the coastline, for example, out that a 90 percent gasoline/10 percent ethanol mix in an estuary, which has a disruptive effect on the is two to three percent less efficient than 100 percent ecology of coastal, shoreline, and ocean organisms. gasoline fuel. Furthermore, growing corn specifically Areas used for tidal generating stations are unavailable for fuel and converting it to ethanol uses fossil fuel for recreational and commercial use and contribute to energy and reduces the amount of agricultural land for the aesthetic deterioration of the coastline, all of which producing food crops. tend to generate opposition among nearby residents. Geothermal and Tidal Energy Conservation and Efficiency Besides the major renewable energy sources discussed Energy efficiency is a measure of how effective we are above, other types are of regional and potential at getting usable work from a given input of energy 2024–2025 Science Pentathlon Resource Guide 70  FIGURE 44 Texas Pentathlon - TX, TX Sources of U.S. electricity generation, 2022. Source: EIA (i.e., the amount of energy or work output—in the for coal-fired systems but are not commercially desired form—divided by the total energy input). feasible at present. An improvement in gas-combustion No energy source is ever 100 percent efficient; some technology has led to the combined cycle natural gas- energy is always lost at each conversion, usually as fired power plant, which can achieve efficiencies of 60 heat leaving the system. At each step in the process, percent, making this system highly desirable. Overall, some energy is lost. And the more steps there are in the United Nations Development Program World the process of turning an energy source into work, the Energy Assessment (2015) estimates that global energy more opportunities there are for a loss of energy and efficiency is about 37 percent. the more inefficient the system is. The goals for energy use in a sustainable society are to Most older, conventional electricity-generating plants increase efficiency while reducing costs and pollutants. have an efficiency of about 36 percent. Newer coal- Because we use energy in a variety of ways and for burning plants may have efficiencies of up to 42 a variety of purposes, it’s a challenge to evaluate percent. Efficiencies of over 50 percent are possible how well we achieve different tasks. By quantifying 2024–2025 Science Pentathlon Resource Guide 71 energy conversions from one form to another, and by quantifying how efficiently we use the converted energy, we can get an appreciation for how effectively we use energy, including the efficiency, financial cost, and the amount of pollution produced for a given task. So far, we have talked about sustainable energy in terms of particular sources or technologies. It may be years before many of these are available or affordable, and often they have disadvantages of their own. Therefore, energy sustainability relies as much on reducing the amount of energy that individuals or nations use as Uniti, a two-seater micro electric vehicle. Smaller, lighter cars on new sources or technologies for providing energy. are more energy efficient. Conservation and increased efficiency are necessary Photo: Uniti aspects of energy sustainability. Reducing Peak Demand Conservation is a consumer-based approach that There are certain times when demand for electricity focuses on reducing energy use by changing users’ is greatest—in the middle of a hot summer day, when habits and actions. Conservation measures can be people are using more air conditioning than normal; everyday actions as simple as turning off lights when or in the middle of a cold winter night in a region they’re not needed, choosing to drive less, combining where homes have electric heat. In order to meet peak trips so that overall mileage driven is reduced, wearing demand—the greatest quantity of electricity that will warmer clothes rather than turning up a thermostat in Texas Pentathlon - TX, TX be needed at any one time—utilities usually build new winter, taking a shorter shower, and many, many more. power plants. However, some utilities have come up This approach is available to anyone; its only drawback with creative ways to reduce peak demand. is the need to change long-standing habits. One way is to encourage consumers and businesses More complex is increasing energy efficiency, or using to conduct optional activities that demand electricity less energy to do the same work. We have previously at non-peak times. Usage is monitored by having two discussed the concept of energy efficiency and how it electric meters at each location, one recording the is derived; here, let’s consider it from the perspective electricity used during the peak demand period— of sustainability. Energy is the ability to do work—say, usually 8 am through 8 pm and the other recording getting from Point A to Point B, one hundred miles the usage during non-peak periods. Peak-demand down the road. The quantity of usable work (getting electricity is billed at a higher rate, so a business or you there) is the same, regardless of the weight of consumer might choose to wait until after 8 pm to the vehicle in which you travel. In terms of physics, conduct certain high-electricity-demand activities. however, traveling in a two-ton car takes more work For example, a homeowner might choose to run than traveling in a one-ton car, and therefore uses more the dishwasher and electric clothes dryer at 9 pm; a energy. If you can get there in a smaller, lighter car, business might use a timer to run energy intensive you consume less gasoline in the process and therefore applications at night or create a second shift for certain increase energy efficiency. activities. If this is done throughout a utility district, Creating more energy-efficient machines is within the it can greatly decrease the peak electrical demand and ability of—and some would say is the responsibility thereby reduce the need for new power plants. of—the manufacturers of vehicles and appliances. The Environmental Protection Agency’s Energy Star However, we can increase energy efficiency individually Program designates as Energy Star compliant certain through the choices we make. Buying a small car rather appliances that do their job at a specified level of than a large car or an SUV, insulating a home so that efficiency. For example, an air conditioner that removes less fuel is required to heat it, using compact fluorescent 10,000 Btus of heat per hour while using less than light bulbs, purchasing EnergyStar appliances, and 1,000 watts will receive an Energy Star designation. traveling less all contribute to energy sustainability. A non-Energy Star compliant air conditioner might 2024–2025 Science Pentathlon Resource Guide 72 use 1,200 watts to do the same job. The difference of of years. Global change incorporates all the previous 200 watts for an hour in one household doesn’t seem topics that we have dealt with—the interconnectedness like much; it might be 2 cents worth of electricity. But of Earth’s systems, the current and future status of if 100,000 households in a large city had Energy Star Earth and the environmental indicators that enable us to compliant air conditioners, the peak demand during a evaluate it, and the interaction of environmental science mid-afternoon summer heat wave could be reduced by and policy. 20 megawatts, or 4 percent of a typical power plant’s output. If both residential and business customers used The terms global change, climate change, and a variety of Energy Star appliances regularly, it could global warming are often used synonymously, make a significant difference in the number of new particularly in the popular press, but they should power plants needed. not be. Climate change is variation in the average weather—temperature, precipitation, storm frequency GLOBAL CLIMATE CHANGE and strength, etc.—over years and decades. Global The Intergovernmental Panel on Climate Change warming deals with the fact that the Earth’s global (IPCC) was established by the United Nations surface temperature has been increasing relative to Environment Programme and the World Meteorological pre-industrial temperatures. Global change includes Organization in 1988 for the purpose of preparing those issues, as well as the other environmental changes reviews of the state of knowledge on climate change, that have been largely caused by human activity. including climate change science and climate change This includes large-scale deforestation and other land impacts today and in the future. From 2021 to 2023, the conversions and the correlated loss of biodiversity, IPCC published its sixth multi-volume assessment of the non-greenhouse gas pollution and its impact on human changing knowledge regarding climate change. During health, and other large-scale changes. Texas Pentathlon - TX, TX each assessment, the IPCC has improved and increased The Greenhouse Effect the amount of global climate change data it analyzes If you have entered an automobile that has been parked and the models it uses to make projections. This has in the sun with its windows closed on a relatively enabled the IPCC to decrease the amount of scientific cool day, you have experienced the greenhouse effect. uncertainty in its estimates to the point that, in the latest Though the outside temperature may be 10°C (50°F), assessment, it could state that, “It is unequivocal that the inside of the car might be 30°C (86°F). On a day human influence has warmed the atmosphere, ocean and when the outside temperature is 30°C, the inside of land. Widespread and rapid changes in the atmosphere, the car might be 38°C (100°F) or even higher. These ocean, cryosphere and biosphere have occurred.”19 striking temperature differentials can be explained by The melting of Arctic and Antarctic ice that shows the greenhouse effect, a natural process that leads to up in the news with increasing frequency is only one the warming of an area that is underneath something example of physical and biogeochemical change taking that traps heat—in the case of a greenhouse or the car, place on Earth. Increasing atmospheric concentrations the glass of the windows. Most incoming solar energy of CO2 and other atmospheric chemicals, such as passes through the windows without being absorbed compounds of nitrogen and sulfur, and the increase in by the glass, which is transparent to solar radiation mercury in fish and mammals are some other significant in the visible range. The solar energy is absorbed biogeochemical changes that have occurred over the by the upholstery, the dashboard, and the steering past fifty years and more. Change that occurs in the wheel, which experience an increase in temperature chemistry, biology, and physical properties of worldwide and then begin to radiate energy outward. Though systems is referred to as global change. Many of these the windows of the car allowed solar radiation to pass types of changes have occurred over geologic time; for through, they do not allow passage of very much of example, concentrations of CO2 in the atmosphere have the outgoing “car” radiation, which is in the infrared ranged from 180 parts per million (ppm) to almost 280 range. This energy is absorbed and reradiated back ppm over the last 800,000 years. However, not only has into the car. The inflow of energy into the car is greater the pace of change increased dramatically because of than the outflow of energy, so there is a positive net recent human activity, but the CO2 concentrations we flux of energy into the car, causing the car to become see today are the highest they have been for millions increasingly warmer, even on a relatively cool day. 2024–2025 Science Pentathlon Resource Guide 73 A very similar process takes place at the surface of major outputs—reflection of solar energy from the Earth. As energy from the Sun travels toward Earth, atmosphere or from the surface of the Earth and it is absorbed by the atmosphere or is reflected and infrared radiation of Earth energy. Over the long scattered back into space. Almost half of this solar term, the net flux of heat is zero; inputs of heat to energy passes through Earth’s atmosphere, much like Earth equal outputs from Earth, and the system is in the solar energy passed through the car windows, and a steady state. However, the input can be greater than is absorbed by objects at the surface of Earth, such the outputs because of an increase in incoming solar as water, land, vegetation, rocks, and human-made radiation (from sunspots, for example) or because of structures, and radiated back out. Since objects at a decrease in outgoing reflected solar radiation either the surface of Earth are roughly the temperature of from a change in materials covering the surface of the Earth (15°C), they emit infrared radiation. Like the car Earth or from an increase in heat-trapping greenhouse windows, heat-trapping gases make the atmosphere gases. If solar radiation is greater than the sum of almost opaque to outgoing infrared radiation. reflected solar energy and radiating infrared Earth energy, Earth becomes warmer in response to the input In the Sun–Earth heating system, there is one of additional heat energy. If solar radiation is less than major energy input—solar radiation—and two the other two fluxes, Earth becomes cooler. This is FIGURE 45 Texas Pentathlon - TX, TX The Sun–Earth heating system. Source: NASA 2024–2025 Science Pentathlon Resource Guide 74 where the greenhouse effect becomes important. GHGs, making for a hotter greenhouse. Greenhouse Gases While the temperature of Earth has fluctuated over The relatively hospitable temperatures on Earth are geologic time, most of the temperature changes have largely a function of the heat-trapping gases that been very slow, and in any given decade, century, are present in the atmosphere, commonly called and sometimes millennium, the Earth’s temperature greenhouse gases (GHGs). We discussed the generation has been relatively constant. Our system analysis of GHGs when discussing pollution and energy makes clear that in order for Earth to stay at a constant production. Nevertheless, you may be surprised to temperature, the energy inputs must equal the energy learn that the most common GHG is water: water vapor outputs. However, a variety of natural processes (H2O gas) absorbs infrared energy radiating from and human activities may increase or decrease the the Earth. The major, but not the only, heat-trapping concentration of GHGs, and the extent of absorption gases added to the atmosphere by human activities, and radiation of energy will increase or decrease such as the combustion of fossil fuels and clearing of accordingly, resulting in variations in the greenhouse land, are carbon dioxide (CO2), methane (CH4), nitrous effect. oxide (N2O), and chlorofluorocarbons (CFCs). In the absence of GHGs, the temperature on Earth would be Evidence of Temperature Change over approximately negative 18°C (0°F). Thus, although we Time commonly think of GHGs—and the global greenhouse Global warming refers to the increased warming of effect—as a negative, it is actually necessary for human Earth’s atmosphere and surface due to an increase in life on Earth. The problem arises when the natural gases that trap heat and, in particular, warming caused greenhouse effect is increased by the human addition of by human activity. As previously mentioned, global Texas Pentathlon - TX, TX FIGURE 46 Global surface temperature measurements. Lowess smoothing is a method of fitting a smooth curve (the black line in the figure) to data points, such as the yearly temperature variation in the figure. Source: NASA 2024–2025 Science Pentathlon Resource Guide 75 warming is one component of the broader phenomenon of global change. One of the greatest difficulties in determining if global warming is occurring is the difficulty of establishing what, if any, temperature change has occurred in recent decades. Though indirect measurements have made it clear that global temperatures have fluctuated over geologic time, what is needed is precise, widespread measures of temperature from locations around the globe for hundreds and thousands of years. Earth surface and ocean temperatures have been measured directly only since about 1880, with varying, though increasing, degrees of confidence. There is a high degree of confidence in at least one global temperature data set maintained by Corals can serve as an indicator of climate change, as they can record temperatures for tens and sometimes hundreds of James Hansen at the NASA Institute for Space Studies years. in New York City. Hansen and his colleagues have By Holobionics - Own work, CC BY-SA 4.0, https://commons.wikimedia. generated a graph of global temperature change that is org/w/index.php?curid=49070224 updated monthly and posted on NASA’s website (Figure 46). This graph, which is comprised of thousands of temperatures for tens and sometimes hundreds of years. measurements from around the world, clearly shows a steady increase in global temperatures from 1880 Effects of Global Warming through 2020 (although there are yearly variations). Global warming is already contributing to overall Texas Pentathlon - TX, TX Measurements for 2023 are not yet complete; however, global change. Atmospheric CO2 has increased 50 we can note that June, July, August, and September percent since 175020, and global average temperature of 2023 were the hottest for those months on record. has increased by about 2°F since 1880. Although a Historical evidence and scientific models suggest that temperature increase of 2 degrees may seem small, Earth is becoming warmer. it is enough to affect global processes significantly, as suggested by many environmental indicators, Indicators of Climate Change including the amount of arctic ice. Snow cover has Indirect measurements that can be obtained through decreased by at least 10 percent since observations biological and physical parameters suggest that current were first conducted in the 1960s. Permafrost has global temperatures are higher than at any time in at thawed, warmed, and degraded in polar, sub-polar, and least the last 150,000 years. Trees can provide indirect some mountainous regions. The growing season has records of temperatures for decades and centuries lengthened by one to four days per decade since the and on rare occasions for more than a thousand 1960s in the Northern Hemisphere. years. Each year, most trees add layers of wood from millimeters to centimeters thick. In middle and high The geographic range for many plants, insects, latitudes, these annual rings are quite distinct and allow and birds has shifted northward in the Northern careful measurement of tree growth and a subsequent Hemisphere and on some occasions has moved up estimate of temperature. Wider rings correspond in altitude on mountains. In some cases, species that with better temperatures for growth (if there is also have increased the northern extent of their range in the enough moisture), which usually means warmer and/ Northern Hemisphere have constricted their southern or wetter conditions in the year when—or the year range because conditions are less favorable for them before—the rings were added to the tree. Corals are further south. Flowering plants have been blooming another surrogate indicator. In relatively clean ocean earlier, birds arrive earlier at their spring nesting waters in and near the tropics, marine corals add annual grounds, and insects are emerging earlier in the bands of calcium carbonate. A number of geochemical Northern Hemisphere. signals in the calcium carbonate allow researchers to “The tip of the iceberg” is an almost literal reconstruct the approximate temperature of the water in description of the changes that have already occurred. which the corals have been growing. Corals can record Environmental scientists foresee extensive changes 2024–2025 Science Pentathlon Resource Guide 76 throughout all of Earth’s systems in the future. human development, will change. Anticipated changes in ecosystems in the northeastern Predicted Future Effects of Global and north-central U.S., for instance, suggest Warming that spruce-fir, aspen-birch, and maple-beech- A number of global changes have been predicted to birch stands of forest will move significantly occur by the end of the twenty-first century as a result northward, greatly decreasing their abundance of global warming, a few of which we have already in existing locations. This change in the makeup mentioned. Here we outline some other projections of vegetation will have profound impacts on the based on available data and the models we described wildlife that depends on these particular types earlier. Though these occurrences represent moderate of trees. Many other species may be threatened to worst-case scenarios, many of them are nevertheless by extinction, as rapid temperature change does considered likely. not allow every population of organisms time to adapt. 6 Continental glaciers and the Greenland ice sheet are expected to continue to retreat. 6 Global warming and the resulting changes Global mean sea level, in part as a result of the will dramatically affect human populations. melting of glaciers, is expected to rise by 0.1 to As sea levels rise, coastal communities 0.9 meters by 2100. and certain open ocean islands will be threatened by inundation and, even before 6 Maximum temperatures will be higher, and that, contamination of their drinking water more heat waves will occur across virtually and erosion of their coastal areas. In the South all land areas. There will be a potential for Pacific, a number of islands and island nations heat and drought damage to crops or greater have already been threatened with flooding Texas Pentathlon - TX, TX irrigation requirements for crops. Demand for from rising sea levels. energy for cooling of living spaces and food will increase.