Chapter 8 Global Systems PDF

8 Global systems How are modern humans affecting global systems? The Arctic island of Greenland has been covered in ice for more than 18 million years. Up to 3 kilometres thick in some places,...

8 Global systems How are modern humans affecting global systems? The Arctic island of Greenland has been covered in ice for more than 18 million years. Up to 3 kilometres thick in some places, the entire ice sheet stretches to 1.7 million square kilometres and holds enough fresh water to potentially raise sea levels by 6 metres if released. Scientists are recording longer and more extensive summer ice melts in Greenland. What has brought about this change? NASA/Jesse Allen, Earth Observatory nelson Earth and space – Stage 5 Key knowledge Scientific knowledge is used to evaluate claims, explanations or predictions about interactions with Earth’s spheres. Global systems, such as the carbon cycle, rely on interactions between the biosphere, lithosphere, hydrosphere and atmosphere. Natural events, such as cyclones, volcanic eruptions and earthquakes, affect Earth’s spheres in many ways; for example, flooding in the hydrosphere and destruction of organisms in the biosphere. Scientific evidence suggests that human activity has enhanced the natural greenhouse effect, depleted portions of the ozone layer and contributed to the loss of biodiversity. Different groups in society may evaluate claims, explanations or predictions about current issues that involve Earth’s spheres according to their own criteria, to protect their own interests; for example, economic interests. Deep ocean currents help cycle water in the atmosphere and stir up nutrients for marine life. ACTIVITY SHEET CULMINATING ASSESSMENT TASK CAT with rubric: Debating the issue Debating the issue Argue either for the affirmative or negative side in one of the following class debates: Hybrid cars should be compulsory in Australia by 2020. Carbon emissions trading is not the answer. Global systems require global strategies. Australia should stop burning coal. Jobs are more important than biodiversity. 318 ISBN 9780170231510  Chapter 8 Global systems What do you already know about evaluating issues involving global systems? A system is a group of objects that are interconnected or that work together. Climate change involves connections between global systems. How responsible are humans for the recent increase in the world’s temperatures? Complete these questions. (Hint: A value is something that a person believes is important.) Describe five values you think the media have in mind when they report 1  on climate change. Describe five values you think scientists have in mind when they report on 2  climate change. Describe five values you have when you think about climate change. 3  ICT 4 Create a bubble chart to represent the similarities and differences in the main values that different groups hold on the one issue. You could create 5 Write a short paragraph explaining your bubble chart. Upload this to the your bubble chart class wiki. using Google Docs. 8.1 Global systems rely on lithosphere the outer part of Earth, consisting of the crust and upper mantle, interactions approximately 100  km thick biosphere Earth is a system linking four different spheres of the planet together: the lithosphere, the part of Earth and its biosphere, hydrosphere and the atmosphere. Each sphere contributes to the way the atmosphere in which living planet works. organisms exist or that is capable of supporting life The lithosphere includes Earth’s crust (Figure 8.1, page 320). The lithosphere includes all the rocks and solid structures on which all life is found. hydrosphere The biosphere contains all the planet’s living organisms (Figure 8.2, page 320). From algae the waters of Earth’s surface in living on the bottom of icebergs to the mountain ash forests of Australia, from plankton to the solid, liquid and gaseous forms blue whale in the oceans of the planet – life is found in many environments. atmosphere Life can exist in many hostile environments. Bacteria have been found deep in Earth’s the gaseous mass or ‘envelope’ crust, slowly eating away at minerals in rocks, while the nuclear reactor destroyed in the surrounding Earth and retained by Chernobyl disaster of 1986 has fungi growing on it, feeding on the radiation being released. Earth’s gravitational field nuclear reactor any of several devices in which a chain reaction is initiated and controlled, with the resulting heat typically used for power generation ISBN 9780170231510 319  nelson Outer and inner core Shutterstock.com/Lukiyanova Natalia/frenta Lower mantle Lithosphere Figure 8.1 Cross-section through Earth, with lithosphere as the outer layer (including the upper mantle and crust) and the lower mantle and core beneath Shutterstock.com/mycola Figure 8.2 The biosphere includes agricultural areas, with surrounding atmosphere. 320 ISBN 9780170231510  Chapter 8 Global systems The hydrosphere contains all forms of water: solid ice on the polar caps; liquid water in oceans, streams, rivers and lakes; and gaseous vapour in clouds and spewing from geysers into the atmosphere (Figure 8.3). Shutterstock.com/David Xu Figure 8.3 The hydrosphere includes features such as Niagara Falls, USA. The atmosphere holds all the gases that make up Earth’s air, which is used to maintain life. The biosphere overlaps into parts of both the hydrosphere and the atmosphere. Anything that happens in one of these spheres will affect the others. Natural disasters are earthquake an obvious example of this, such as the earthquake and tsunami that hit the east coast of Japan on 11 March 2011 (Figure 8.4). a sudden movement of Earth’s crust caused by the release of stress accumulated along geologic faults or by volcanic activity tsunami a very large ocean wave caused by an underwater earthquake or volcanic eruption Figure 8.4 Getty Images The tsunami inundating coastal Japan in March 2011 A shifting of the tectonic plates in the lithosphere created a tsunami (hydrosphere) that devastated coastal regions and wiped out many human and natural habitats (biosphere). The location of the nuclear reactor near the coast at Fukushima led to the release of radioactive material into the atmosphere. Radioactive materials reached the upper layers of the atmosphere and circulated via the air movement; any material that entered waterways was spread into the hydrosphere, eventually reaching the oceans. ISBN 9780170231510 321  nelson Shutterstock.com/Nate A Figure 8.5 A bird caught in an oil spill – an industrial accident in the hydrosphere has impacted negatively on the biosphere The Fukushima disaster was a case of a natural disaster causing an industrial disaster; that meteorological bureau is, one caused by a breakdown in technology. The death toll was high; however, it could have a government agency responsible been much higher. Meteorological bureaus and seismologists advised governments across for providing weather information many nations to evacuate residents in coastal towns and cities. to the community An industrial disaster that affected the natural world was the wreck of the Exxon Valdez in seismologist 1989 off the coast of Alaska. Millions of tonnes of oil spilled into the ocean (hydrosphere) and a scientist who studies washed up on local beaches (lithosphere), ultimately affecting local wildlife (biosphere) such as earthquakes is shown in Figure 8.5. WORKSPACE ACTIVITY 8.1 Advanced warnings Advanced warnings In what ways are advanced warnings of disaster communicated to the public? What do you think is the best way to communicate advanced warnings quickly? Explain why. Consider all the relevant factors when thinking about how you would communicate; for example, the purpose of the warning and what effect this might have on your warning system. 322 ISBN 9780170231510  Chapter 8 Global systems ACTIVITY 8.2 Think, pair, share Three major natural events are cyclones, volcanoes and earthquakes. 1 On your own, design a worksheet to compare the effect of cyclones, volcanoes and earthquakes on Earth’s biosphere, lithosphere, hydrosphere and atmosphere. Possible activities include a crossword, word search or cloze passage. 2 Pair up with another student and swap worksheets. Complete these sheets, return them and then mark them. 3 Share with another pair and compare your results. Evaluate the effectiveness of each sheet. Storing carbon The world’s forests store 283  billion  tonnes of carbon dioxide. Twenty per cent of all carbon dioxide emissions generated by humans are VIDEO Threat to Southern Ocean caused by deforestation. The current rate of global deforestation is about 13  million hectares a year, which is an area equal to the size of England. How long would it take to clear an area the size of Australia? Shutterstock.com/think4photop ISBN 9780170231510 323  nelson water cycle the cycle of evaporation, condensation The carbon cycle and precipitation that determines the In Chapter 9 of iScience 8 for NSW you learnt about the water cycle. It is one example of distribution of Earth’s water how materials move through the different spheres of Earth. The carbon cycle also involves carbon cycle movement of materials through all the spheres (Figure 8.6). the combined processes of The largest source of carbon on Earth is carbon dioxide (CO2) in the atmosphere. photosynthesis, decomposition, It enters the biosphere through plants in the process of photosynthesis. Photosynthesis combustion and respiration produces a simple sugar called glucose (C6H12O6). Plants are the primary producers in by which carbon in various most food chains and they produce many of the major chemicals needed for life such as compounds cycles between the atmosphere, oceans and living carbohydrates, proteins, lipids and nucleic acids. organisms carbon dioxide a colourless, odourless, incombustible gas (CO2) formed during respiration, combustion and the breaking down of Industrial CO2 in dead organic material processes the air Photosynthesis photosynthesis Cellular respiration and the process in green plants and Industry fermentation certain other organisms by which carbohydrates are synthesised Plants (made) from carbon dioxide and water using light as an energy source; Cellular most forms of photosynthesis respiration release oxygen as a by-product carbohydrate Animals an organic compound containing only carbon, hydrogen and oxygen; Decay in the includes sugars, starches, celluloses absence of oxygen Decay in the and gums and is the major energy (very slow) absence of oxygen source in the diet of animals (very slow) Fossil fuels (such as coal, oil, Combustion (of part of the natural gas) supplies of the fossil fuels Shells and stored underground) coral ANIMATION The carbon cycle Detritus Figure 8.6 Decomposers The carbon cycle protein In some situations, carbon stays within the organism briefly and is released back into the a complex organic molecule that environment by respiration. During respiration glucose is broken down to produce energy in contains carbon, hydrogen, oxygen, cells, releasing carbon dioxide. At other times, the carbon is added to a cell’s structure. This nitrogen and usually sulfur; is amount of carbon will stay within the organism throughout its life. For example, the carbon composed of one or more chains of amino acids; and is the fundamental in a tree is kept out of the environment for the life of the tree and is not released back into component of all living cells the atmosphere until the wood is used to light a fire or the tree dies and decomposes. If the tree becomes fossilised, the carbon is taken out of the environment for millions of years. It is eventually released into the atmosphere when fossil fuels are burnt. When you breathe, you release carbon dioxide into the atmosphere, and the digestive waste of cows releases methane (CH4). As we burn fuel, whether in our bodies or in machines, we contribute to the release of carbon dioxide into the atmosphere. 324 ISBN 9780170231510  Chapter 8 Global systems lipid an organic compound – including fats, oils, waxes, sterols and triglycerides – that is insoluble in water, oily to the touch and constitutes the principal structural material of living cells nucleic acid a complex compound found in all living cells and viruses that, when in the form of DNA and RNA, controls cellular function and heredity Shutterstock.com/Mary Terriberry Figure 8.7 Defoliation (loss of leaves) caused by acid rain leads to the death of trees because they are no longer able to photosynthesise. Before the large increase in the human population following the Industrial Revolution, the amount of carbon in the atmosphere was kept constant by plants absorbing carbon dioxide and releasing oxygen back into the atmosphere. As the world’s population expanded, land that was covered by trees, forests and swamps was cleared for people to live and grow more food. So the amount of plant life that recycles carbon dioxide back into the biosphere from the atmosphere was reduced. In the 1980s damage to the Black Forest in Germany was caused by the effect of acid rain (Figures 8.7 and 8.8, page 326). It was also reported that many tree species were not growing as expected across the United States and Europe. The release of pollutants into the atmosphere gives rise to acid rain, which then damages living organisms. Acid gases (sulfur dioxide and nitrogen oxides) are released into the atmosphere. Once these acidic gases are in the atmosphere, they can be carried far away from the original source, enter the hydrosphere, and then come down in rain in a new location. ISBN 9780170231510 325  nelson Acidic gases (sulfur dioxide Gases are carried and nitrogen oxides) are by the wind. released into the atmosphere. Gases dissolve in rainwater to form acid rain. Getty Images/DEA Picture Library Acid rain kills plant life, pollutes rivers and streams, and erodes stonework. Figure 8.8 The release of pollutants into the atmosphere gives Generating electricity rise to acid rain, which The start of the Industrial Revolution in the 1790s led to the use of machinery in industry and then damages living agriculture. Fossil fuels were used to run the machinery and generate electricity (Figure 8.9). organisms. Acid gases This increased the amount of carbon dioxide entering the atmosphere. While the generation (sulfur dioxide and nitrogen of electricity has been refined over the decades, modern life has meant that people are using oxides) are released into the atmosphere. more of it than ever. Little attention was given to the waste products and the effect on the carbon cycle. Shutterstock.com/Mark William Richardson Figure 8.9 A coal-fired power station emitting carbon dioxide into the environment 326 ISBN 9780170231510  Chapter 8 Global systems Carbon pollutants are released at various stages during electricity generation at a coal- pollutant fired power station. When coal is burnt to produce steam, carbon dioxide, soot and ash are any contaminant introduced released into the atmosphere. Cooling water releases heat into the atmosphere that cannot into a natural environment that causes instability, disorder, escape as the carbon dioxide builds up. As we clear land, the number of carbon-cycling trees harm or discomfort to the is reduced. So as more carbon dioxide is released, less can be recycled through the natural ecosystem – that is, to physical process of photosynthesis. systems or living organisms Carbon capture Figure 8.10 shows the concentrations of carbon dioxide in ice cores from 400  000  years ago to the present. There is a relationship between increasing temperatures and carbon-dioxide concentrations – when one increases, so does the other. Therefore, the ice cores and their carbon dioxide concentrations represent a snapshot of conditions throughout geological time. Antarctic ice core data Temperature variation CO2 concentration 380 4 CO2 (parts per million by volume) 2 340 0 Temperature (°C) 300 –2 260 –4 –6 220 –8 180 –10 400 000 350 000 300 000 250 000 200 000 150 000 100 000 50 000 Present Years (before present) Figure 8.10 Carbon dioxide in ice cores from 400  000  years ago to the present ACTIVITY 8.3 WORKSPACE Think, pair, share Think, pair, share 1 On your own, describe as many ways as possible that electricity generation contributes to the imbalance in the carbon cycle. Consider at least three different ways of generating electricity. 2 Pair up with a classmate, compare your lists and add new ideas. 3 Share with another pair and combine your lists. Upload the combined list to the class wiki. ISBN 9780170231510 327  nelson carbon capture the process of capturing carbon Burning ban dioxide from large point sources, such as fossil fuel power plants, King Edward I of England banned the burning of sea coal by and storing it to prevent it entering the atmosphere proclamation in London in 1272 after its smoke had become a problem. pre-combustion carbon capture Many methods have been suggested to reduce the impact of the burning of these fuels. One such method is carbon capture. This involves trapping the carbon when it is produced, the process in which carbon dioxide is trapped before the containing it and transporting it to a storage facility underground. Most carbon-capture fossil fuel is burned technology is focused on fossil fuel power stations that burn fuel, such as coal or gas, to provide the energy to convert water into steam. The steam turns a turbine that is connected to a generator to produce electricity. These power stations are one of the largest sources of carbon released into the atmosphere. Essentially, the process involves the removal of carbon Figure 8.11 dioxide from the waste before it is released into the atmosphere. The carbon needs to be Pre-combustion carbon captured either before the fossil fuel is burned or after. capture – the removal of In pre-combustion carbon capture, carbon dioxide is trapped before the fossil fuel is carbon (as carbon dioxide) burned (Figure 8.11). There are three stages. from fuel prior to combustion 1 The fuel (methane or coal) is converted into hydrogen and carbon monoxide to form a gas. in the power plant 2 The carbon monoxide reacts with water to produce carbon dioxide. 3 T  he carbon dioxide is separated from the hydrogen (which is combusted cleanly), compressed into a liquid and transported to a storage site. Carbon dioxide Exhaust gases Separation Hydrogen Fuel Power Combustion/oxidation Air/oxygen 328 ISBN 9780170231510  Chapter 8 Global systems ACTIVITY 8.4 WORKSPACE Catalytic converters Catalytic converters 1 Find out what a catalytic converter is. ANIMATION Carbon capture 2 Describe why they were introduced into the automotive industry. 3 Outline when they first appeared in cars, the pollutants normally produced by an engine and how the catalytic converter reduces these post-combustion carbon capture pollutants. the process in which carbon dioxide is separated from other waste products of the combustion Pre-combustion capture has an 80–90% success rate. This procedure is currently process before they are released employed to remove carbon dioxide from natural gas. into the environment In post-combustion carbon capture, the carbon dioxide is separated by a filter from Figure 8.12 other waste products as it travels up the smoke stack (Figure 8.12). The filter is a material that Post-combustion carbon absorbs the carbon dioxide. The process can also prevent 80–90% of the emissions reaching capture – the combustion the atmosphere. However, it is costly to then compact and prepare the carbon dioxide for of fuel produces waste storage. The advantage of this process is that the filter can be fitted to older power plants with products, including carbon. a very good success rate. The carbon is removed from the waste. Other Carbon gases dioxide Fuel Separation Air Combustion Power ISBN 9780170231510 329  nelson ACTIVITY 8.5 Student investigation: What is your carbon footprint? Use the Internet to complete the following. carbon footprint 1 Define ‘carbon footprint’. the amount of carbon dioxide 2 Calculate your own and your family’s carbon footprint using a carbon emitted by a person, organisation or event calculator on the Internet. 3 Critically analyse ways to reduce your footprint over one week and compare them with those of your classmates. 4 Summarise your findings as a digital poster using Glogster. Alternatively, create a voki that could be run as an advertisement to raise awareness of six things that every household could do to reduce their carbon footprint. Share this with the rest of the class on the class wiki. WORKSPACE QUESTIONS 8.1 What have you learnt? 8.1 What have you learnt? Understanding 1 Describe the four spheres that make up Earth. Applying 2 Into which of the spheres do the following belong? a Clouds over the Pacific Ocean b Rabbit burrows in Victorian farmland c Ord River Dam in Western Australia d Blue Lake, Mount Gambier 3 Explain how the carbon cycle influences each of the four spheres listed in Question 1. 4 a Describe how photosynthesis fits into the carbon cycle. b Explain why this is so important to the living organisms of the planet. 5 Compare and contrast each carbon-capture technique. Investigate possible storage solutions for captured carbon and outline one of them. Analysing 6 Complete a five whys analysis with the starting question: ‘Why would a butterfly flapping its wings on one side of the planet influence a catastrophic event on the other side?’ 330 ISBN 9780170231510  Chapter 8 Global systems QUESTIONS 8.1 Creating 7 Use a graphic organiser to organise the content that you have learnt so far. Revisit this organiser throughout the chapter to add, edit and connect information as you gain more knowledge. Reflecting 8 Describe things that you do each year that would have an effect on the spheres. Record this on your blog or other organiser. 9 Evaluate the effectiveness and environmental impact of the carbon-capture strategies described in the chapter. 8.2 Global issues A change in one global sphere will affect another. However, many of these changes are very subtle, and not easily measured. The main issues are the greenhouse effect, ozone depletion, climate change and rising sea levels, waste management and the loss of biodiversity. What is the greenhouse effect? ACTIVITY 8.6 INTERACTIVE Greenhouse effect self-check quiz The greenhouse effect Work in a group to brainstorm all your thoughts about what the greenhouse effect is. Use SmartDraw to create a cluster diagram. Store this on the class wiki and add or remove from it as you read on. The natural greenhouse effect is vital for life on Earth. Radiation from the Sun passes through the atmosphere. About half of this radiation hits Earth’s surface and heats it, while the rest is reflected back into space, mainly off clouds (Figure 8.13, page 332). The radiation absorbed by Earth eventually radiates back into the atmosphere as heat (thermal energy). Greenhouse gases in the atmosphere do not allow all of this energy to radiate back into space. If there was no carbon dioxide, Earth’s surface temperature would be around –30°C, which is too cold for most life. The greenhouse gas natural greenhouse effect is required to make the biosphere habitable for life. an atmospheric gas that contributes to the greenhouse Gases that absorb heat in the atmosphere are known as greenhouse gases. effect by absorbing infrared Water vapour is one of the most important. Other greenhouse gases are carbon dioxide, radiation produced by solar methane, nitrous oxide and fluorinated gases. warming of Earth’s surface ISBN 9780170231510 331  nelson Thermal low-energy High-energy solar radiation radiation into space Directly radiated absorbed by Earth from surface Greenhouse gas absorption Heat and energy in the atmosphere Figure 8.13 How the greenhouse effect is generated: high-energy solar radiation reaches Earth’s The surface and is absorbed and greenhouse re-radiated as low-energy effect radiation. Some is able to go back into space, but some is absorbed by greenhouse Earth’s land and ocean surface gases in the atmosphere. warmed to an average of 14°C This absorbed energy can heat up Earth. Three of the four gases are directly made from the burning of fossil fuels, but there are INTERACTIVE also other sources. For example, livestock and the decay of organic matter generate methane. Greenhouse effect Nitrous oxide is emitted as a result of agricultural practices. Fluorinated gases are produced by industrial processes. When human activities add more greenhouse gases to the atmosphere, more heat and energy remains trapped on Earth by these atmospheric gases. We call this the enhanced greenhouse effect, or human-induced greenhouse effect. This extra heat energy causes global warming and changes in the hydrosphere and atmosphere that lead to changes in climate. WORKSPACE EXPERIMENT 8.1 Student investigation: Greenhouse effect in a jar Student investigation: Greenhouse effect in a jar Work with a partner. Present your findings as a formal scientific report (see Appendix – How to write a scientific report, page 350). Read through this activity and then: predict what you think the results will be write an aim and hypothesis identify the dependent and independent variables and control. 332 ISBN 9780170231510  Chapter 8 Global systems EXPERIMENT 8.1 Materials 2 thermometers, or data logger and probes stopwatch 2  L plastic drink bottle with the bottom cut out so that it sits flat Method 1 Go outside and place the two thermometers in direct sunlight for 5  minutes. Let the temperatures stabilise. 2 Cover the first thermometer with the plastic bottle and start recording the temperatures from both thermometers every minute for 15  minutes. Results 1 Graph the results on the one set of axes. 2 Compare your results with your prediction. Discussion 3 Explain your results. You may need to convert your results into percentage increases in temperature so that they can be compared more easily. 4 Evaluate how this model compares with the greenhouse effect in our atmosphere. 5 Outline any sources of error in your data or data collection techniques. Discuss ozone how you could improve on your method. an unstable form of oxygen (O3 ) Conclusion that is formed naturally in the ozone layer from atmospheric 6 Discuss whether your hypothesis was supported or disproved. oxygen by electrical discharge or exposure to ultraviolet radiation; Extension it is also produced in the lower atmosphere by the photochemical 7 Research and describe the role of high– and low–energy radiation in the reaction of certain pollutants greenhouse effect. smog fog that has become mixed and What is the ozone layer? polluted with smoke UVB radiation Ozone is a gas found in Earth’s atmosphere at 15–30  km above Earth’s surface (Figure 8.14, page 334). It is also found at ground level, where it is a component of smog pollution. The role ultraviolet light, or the ultraviolet part of the electromagnetic of ozone in the atmosphere is to absorb UVB radiation before it enters Earth’s atmosphere. spectrum UVB radiation has many harmful effects, especially to mammals; for example, it is a major cause of skin cancer. Even though the ozone layer is about 50  km thick, it is changing. chlorofluorocarbon (CFC) Chlorofluorocarbons (CFCs) are compounds that contain chlorine, fluorine and carbon. a compound containing carbon, They were once mainly used as refrigerants and aerosol propellants. Scientists Paul Crutzen fluorine and chlorine, formerly used as a refrigerant and as a (Netherlands), Mario Molina (Mexico) and Sherwood Rowland (USA) discovered that the chlorine propellant in aerosol cans; the in CFCs reacts with ozone, destroying the ozone layer. The scientists were awarded the Nobel chlorine in CFCs causes depletion Prize in Chemistry in 1995, and the use of CFCs was banned worldwide. of atmospheric ozone ISBN 9780170231510 333 nelson That’s not very thick! If the ozone layer was compressed by sea-level pressures, it would only be about 3  mm thick. Ozone is a highly reactive chemical. It reacts with synthetic substances Figure 8.14 that contain chlorine, fluorine, bromine, carbon and hydrogen. As substances The upper atmosphere (the containing these elements are released into the atmosphere, they break stratosphere) is separated down atmospheric ozone, depleting the layer. from the lower atmosphere (the troposphere) by the ozone layer. Stratosphere Air temperature increases with height. Ozone layer Ultraviolet radiation is absorbed, creating the ozone layer in the stratosphere. Troposphere Air temperature decreases with height. The ozone layer over Antarctica has changed size and has a significant hole. Figure 8.15 shows ACTIVITY SHEET the increasing size of the ozone hole from 1981 to 1999. Scientists at CSIRO and the Bureau of Nobel Prize Meteorology in Melbourne began measuring the ozone layer in 1956. Some of the largest measurements were recorded in the late 1980s and early 1990s. The size of the hole changes throughout the year. The largest measured hole was on 6 September 2000, when it was 29.9  million square kilometres. The largest hole in 2012 was recorded in September at 21.2  million square kilometres. This decrease in the size of the hole from 2000 to 2012 is partly due to the reduction in CFC use. This partial recovery of the ozone layer will help protect the biosphere from the effects of UVB radiation. 334 ISBN 9780170231510  Chapter 8 Global systems Figure 8.15 These computer-simulated images show the increasing size of the ozone hole over Antarctica from 1981 to 1999. NASA ACTIVITY 8.7 WEBLINK Ozone depletion Student research task: Where to live in Australia WEBLINK 1 Use a variety of sources to create a list of places in Australia where you Bureau of Meteorology would be exposed to high levels of UVB radiation due to ozone depletion during the months of March, June, September and December. Show these locations using Google Earth. WEBLINK Ozone layer on the mend 2 Using this information, select three or four safer places to live. 3 Explain your choices, and present your findings as a digital presentation of your choice. WEBLINK An Olympic-sized ozone hole ISBN 9780170231510 335  nelson WORKSPACE QUESTIONS 8.2 What have you learnt? 8.2 What have you learnt? Understanding 1 Explain ‘greenhouse effect’. In your explanation, use the terms ‘natural greenhouse effect’ and ‘enhanced greenhouse effect’. 2 Outline the most common greenhouse gases and their sources. 3 Explain how the hole in the ozone layer occurred. 4 Some people confuse the greenhouse effect with the ozone hole. Summarise what you would say to these people to clear up this confusion. Applying 5 Use diagrams to explain why the greenhouse effect occurs. Evaluate its importance to life on Earth. 6 Describe whether the following are greenhouse gases or not. Justify each answer. a Steam from a shower b Exhaust fumes from a car c Steam and odour from a compost heap d Smoke out of a chimney from an open fireplace Creating 7 Create a pamphlet to alert people to the activities in which they participate that increase greenhouse gases in the atmosphere. Explain the consequences of their actions and propose alternative activities that they could undertake. 8 Revisit your organiser to add, edit and connect information. Reflecting 9 Justify or refute this statement: ‘Australians need to be concerned about ozone depletion’. global warming 8.3 What is climate change? an increase in the average temperature of the atmosphere climate As you have learnt, the enhanced greenhouse effect causes more heat to be trapped within Earth’s the meteorological conditions, including temperature, spheres. Global warming is the term used to describe an increase in the average temperature of precipitation and wind, that Earth’s atmosphere, especially a sustained increase that is able to cause climate change. characteristically prevail in Climate is the season-to-season or year-to-year variability in temperature and rainfall over a particular region over an extended period of time a region for a period of 30  years. Day-to-day changes are described as weather. According to the Australian Government Bureau of Meteorology: weather Australia and the globe are experiencing rapid climate change. Since the middle of the 20th the state of the atmosphere at a century, Australian temperatures have, on average, risen by about 1°C with an increase in given time and place, with respect to variables such as temperature, the frequency of heatwaves and a decrease in the numbers of frosts and cold days. Rainfall moisture, wind velocity and patterns have also changed – the north-west has seen an increase in rainfall over the last barometric pressure 50  years while much of eastern Australia and the far southwest have experienced a decline. © Copyright Commonwealth of Australia 2012, Bureau of Meteorology 336 ISBN 9780170231510  Chapter 8 Global systems No issue has caused more debate and argument between scientists, politicians and the media than the idea of climate change. Although these debates continue, there is plenty of data to support the idea that some sort of change is occurring. The year 2012 was the 20th consecutive year that Sydney had above average temperatures. In February there was massive flooding in New South Wales and Queensland, while across the globe there were extreme conditions, including Hurricane Sandy, which affected the Caribbean and the United States of America. An international committee, the Intergovernmental Panel on Climate Change (IPCC), was established in 1988. It gathered information from many scientific bodies and drew conclusions about the state of Earth’s warming. In 2007, these conclusions were: warming of the climate is occurring  most of the observed increases in temperatures since the mid-20th century result from human activities increasing the emission of greenhouse gases human-related warming and sea-level rises will continue for centuries the chances of this warming occurring as a result of natural processes are less than 5%  there is a greater chance that there will be an increase in heat waves, warm spells and heavy rainfall, as well as drought, cyclones and extreme high tides. These conclusions have encouraged many nations to adopt programs to reduce greenhouse-gas emissions and sign the Kyoto Protocol, which was intended to reduce emissions by 2012. A small number of scientists dispute that this current global warming is any different from what has occurred previously in Earth’s history. They argue that Earth undergoes such cycles naturally. However, these scientists are in the minority. For example, Ian Plimer, currently professor of mining geology at the University of Adelaide, stated in 2002: Natural climate changes occur unrelated to carbon dioxide contents. We’ve had many, many times in the recent past where we’ve rapidly gone into a greenhouse and the carbon dioxide content has been far, far lower than the current carbon dioxide content. It was only 1100  years ago where Greenland was populated. It was called Greenland because it was green. There were crops, there were cattle there... we’ve only got to have one burp from a volcano and we’ve totally changed the atmospheric composition... It looks as if carbon dioxide actually follows climate change rather than drives it. © 2003 Lateline. Australian Broadcasting Group (www.abc.net.au/lateline/stories/s650126.htm) Tackling climate change The Kyoto Protocol was agreed to in 1997 as a means of reducing potential effects of climate change due to the emission of greenhouse gases. It came into effect in 2005. While Australia is a small country in terms of population, per capita it has been one of the world’s worst greenhouse gas emitters. In the past, more than 80% of electricity in Australia has been generated through the burning of coal. To help reduce Australia’s emissions, the Australian Government implemented an Emissions Trading Scheme in 2012. Under the scheme, companies emitting large amounts of greenhouse gases are required to pay for each tonne of gas they emit. It is intended that these companies might change processes so that they emit less gas, or find alternative energy sources. As government changes, so do policies. There is still much debate about the structure of strategies to combat climate change. The change of government in Australia after the 2013 WEBLINK Tackling climate change federal election has ensured that debate will continue. For more information see the weblink in Australia ‘Tackling climate change in Australia’. ISBN 9780170231510 337 nelson ACTIVITY 8.8 WORKSPACE Climate opinions Climate opinions 1 Describe the intent of the Kyoto Protocol. 2 Investigate the commitment Australia has made for the second period set by the Kyoto Protocol (2013–20). Research the current Federal Government scheme to tackle climate change. 3 Outline the arguments for and against an Emissions Trading Scheme. Do you think this will be beneficial to the climate? Justify your opinion. WORKSPACE ACTIVITY 8.9 Looking at the evidence Looking at the evidence View the video ‘Big melt 3: viewing the evidence’ and read the quotes on VIDEO page 337. Then complete the following questions. Big melt 3: viewing the evidence 1 Outline your opinion about global warming. Explain the evidence you have to back up your opinion. 2 Pair up with someone in your class who holds the opposite viewpoint to ACTIVITY SHEET you. What evidence do they use? How to write a persuasive essay 3 Use both sets of evidence to write a persuasive text on the following topic: ‘Global warming is a natural occurrence’. Use a blabber to present your text. Upload the link to the class wiki. Climate change and biodiversity Any potential climate change is expected to have a large impact on biodiversity, which is the variety of all living organisms – plants, animals and micro-organisms – and all their genetic variations and connections within an ecosystem. A large amount of biodiversity is usually an indicator of a healthy environment. The organisms we see probably only make up about 1% of the planet’s biodiversity. Biodiversity also includes the many microscopic fauna and flora, such as algae, fungi, bacteria and viruses. Most of Earth’s biodiversity consists of invertebrates, fungi, bacteria and non-flowering plants. The complexity of relationships between organisms can be seen when we look at what happens when a part of the environment is removed or altered. Since all of Earth’s spheres interact, including the biosphere, global biodiversity is declining as climate change, floods, fires and habitat loss continue to increase. 338 ISBN 9780170231510  Chapter 8 Global systems Seagrass meadows Seagrasses are a group of marine plants that grow along the shallow coasts of most continents. seagrasses They get their energy through the process of photosynthesis and are the start of many coastal food the only flowering plants that can webs. They also provide sheltered habitats and breeding areas for many sea creatures. live underwater; seagrasses live Generally seagrasses are found in waters less than 10  metres deep. At depths greater in the coastal waters of most of the world’s continents than this, there is not enough sunlight getting through the water for photosynthesis to occur. An increase in sea levels may have dramatic effects on these coastal regions. As the ocean rises, the seagrasses in the deeper parts will not receive enough light and they will be unable to generate nutrients through photosynthesis. Those grasses will die, potentially affecting the other sea life that depends on them. WEBLINK Seagrasses These seagrasses also affect how clear the waters are as their roots hold the seabed together. The waters around seagrasses are generally very clear. WEBLINK Seagrass meadows Auscape/Mark Spencer Figure 8.16 Seagrass species can grow into dense patches that provide food and shelter for many other species. Many drastic weather events, including torrential rains and cyclones such as those experienced along the northeastern coast of Australia over the summer periods of 2010–11 and 2011–12, have affected the growth of seagrasses. Extreme rainfall over land led to the runoff of huge volumes of water into the estuarine and coastal meadows. With these rains come large volumes of silt and sediment, caused by inland erosion, which create dirty (turbid) water conditions when they reach the coast. The turbidity reduces the light reaching the plants and turbidity therefore impacts on photosynthesis. If these events continue for extended periods of time, the a measure of water clarity or seagrass will perish, as will the many organisms reliant on it for food and shelter. murkiness ACTIVITY 8.10 WORKSPACE Endangered dugongs Endangered dugongs Read the article in the weblink ‘Protecting the dugong’ and then complete the questions that follow. WEBLINK Protecting the dugong 1 Recall the climatic event that prompted this article to be written. ISBN 9780170231510 339 nelson ACTIVITY 8.10 2 Outline the environmental problems that resulted from this event. 3 Evaluate the decision that resulted from these environmental problems. 4 Outline the actions that occurred as a result of the choice identified in Question 3. 5 Assess the reliability of the number of dugong deaths identified in the article. 6 Describe your reaction to this article. Rising sea levels Since the collection of data on sea levels across Australia began in 1880, an overall increase in sea levels of 200  mm has been measured. Information was initially based on high tide recordings but is now based on satellite data. The effects of rising sea levels are of most concern for smaller islands, especially coral atolls, such as the Maldives. These islands also provide valuable nesting sites and habitats for many organisms. Living things that may only nest in these tiny specks in the vast waters of the Pacific Ocean may soon be looking for other places to breed or else they may perish. Seabirds such as boobies and frigate birds return to the same islands where they were born to breed. The loss of shelter and food at these Pacific islands will cause bird numbers to decline. The major threat to the world’s biodiversity is the loss of habitat. In the past, we have worried about the loss of this habitat as a direct consequence of human activity, such as the clearing of rainforests and the reclaiming of wetlands and swamps for building. Now, global warming is affecting the habitats along the edges of the major continents. Wetland and estuarine ecosystems include some of the most diverse communities, such as the nesting sites for many species of sea turtle (Figure 8.17), including leatherback, hawksbill and green sea turtles. All these turtles require sandy beaches on which to lay their eggs. Rising sea levels erode coastlines and remove these nesting sites. Shutterstock.com/Mana Photo Figure 8.17 Sea turtles lay their eggs on sandy beaches. Rising sea levels threaten to destroy these nesting sites. 340 ISBN 9780170231510  Chapter 8 Global systems Melting Greenland The volume of the Greenland icesheet was last measured as 2.85  million cubic kilometres. If the icesheet were to melt, global sea levels are predicted to rise by more than 6  metres. This would flood most coastal cities and submerge several small island countries, such as Tuvalu and the Maldives. In July 2012, NASA data showed that 97% of the icesheet had experienced some melting. Alamy/© imagebroker Global warming and sea ice sea ice ice that forms at the ocean Evidence shows that over the last 30–40  years the amount of sea ice has decreased, surface once the surface particularly in the Arctic Circle. Unlike the Antarctic ice cap, which is frozen water over a land temperature drops to freezing point (about –2°C for sea water) mass, the Arctic polar cap has no land under it. Also, the age and thickness of the ice are during autumn and winter decreasing (Figure 8.18). Less ice means less surface area to reflect light and heat. This leads to more rapid melting. ice cap Scientists have become increasingly concerned over the last 15  years about the reduced extensive sheets of ice; size of the polar ice caps and their ability to sustain the organisms that rely on them. For technically, they cover an area that is smaller than 50  000  km² example, under threat are the algae that survive on the underside of the ice, which support other species through food webs, including invertebrates, birds, fish and marine mammals. North American caribou travel 5000  km through Alaska and Canada into the Arctic Circle on their annual migrations; currently, they take nearly one-third of each year to complete their journey. Without the icesheets this journey would take much longer. Polar bears who lived on the Arctic ice shelf have had to move further south as the ice has melted, to search for food. This has resulted in more interactions between polar bears and humans as the bears venture into populated areas. ISBN 9780170231510 341  nelson Science Photo Library/European Space Agency/CPOM/UCL Figure 8.18 Sea-ice thickness in the Arctic Ocean during January and February 2011 However, one of the largest concerns is the impact of the retreating icesheet on the permafrost permafrost. Permafrost is soil or rock that remains frozen – at or below 0°C – throughout the permanently frozen ground; soil, year. It is found in polar and alpine regions, where the mean average temperature is below the sediment or rock that remains at freezing point of water. In some areas, the top layers of the soil may thaw, allowing for the growth or below 0°C for at least of some plants in summer months, while the depths remain frozen. The frozen layer acts as a two years barrier to the movement of water into deeper layers. The unfrozen soil becomes quite soggy with poor drainage. Cool soils in permafrost areas allow for slow plant growth and decomposition. As the area, thickness and age of the Arctic sea ice decrease, air temperature over the oceans begins to rise. These warmer air masses move inland, increasing the land temperatures. Therefore, rapid sea-ice loss leads to warmer inland temperatures, particularly in autumn. In turn, there is increased loss of permafrost. The frozen ground of the Arctic also stores up to 30% of carbon stored in soils worldwide. As the permafrost thaws, the release of the greenhouse gas carbon dioxide into the atmosphere adds to the global warming. The global carbon balance is disturbed and results in increased carbon levels in the atmosphere. Scientists from University Corporation for Atmospheric Research – a consortium of research universities in Colorado, in the United States – have developed computer simulations that show that when Arctic sea ice is in decline, land temperatures can increase to triple the predicted rate of other global-warming models (Figure 8.19). Though most of the warming occurs over the oceans, this temperature increase is known to penetrate at least 1500  km inland. 342 ISBN 9780170231510  Chapter 8 Global systems Figure 8.19 Simulated future temperature trends This computer simulation shows that when Arctic sea ice is in decline (left), land °C decade–1 Periods of rapid 3.0 Periods of moderate temperatures can increase sea-ice loss 2.0 or no sea-ice loss compared with times of no 1.0 sea-ice loss (right). 0.5 0.0 –0.5 –1.0 –2.0 –3.0 2008 ©UCAR, illustration by Steve Dayo Global warming and deep ocean currents VIDEO Disappearing villages Oceans and surface water make up 70% of Earth’s surface. Ocean currents are the vertical and horizontal movement of both surface and deep water throughout the world’s oceans. The currents move in a specific direction, and influence Earth’s atmospheric moisture content and surface current climatic conditions. the water movement found in the Surface currents refer to water movement found in the upper 400  metres of the ocean; upper 400  m of the ocean they make up 10% of the water in the oceans. deep ocean current Deep ocean currents are caused by changes in both water temperature and salinity and the water movement caused occur below a depth of 400  metres; they make up 90% of the oceans. As water warms, it expands by changes in both water and becomes less dense than colder water. The saltier the water, the more dense it is. The less temperature and salinity; deep dense water rises towards the surface and the denser water sinks to the lower depths of the ocean currents occur below a depth of 400 m oceans. The rising of less dense water is called an upwelling. It brings nutrients and other matter to the surface, allowing for more feeding for the top-dwelling marine organisms (Figure 8.20). upwelling the movement of deeper colder waters to shallower depths WEBLINK Amazing feeding frenzy Shutterstock.com/melissaf84 Figure 8.20 Shark feeding frenzies are most common where there is a deep-sea upwelling of nutrients. ISBN 9780170231510 343  nelson EXPERIMENT 8.2 Simulating deep ocean currents Ocean currents are affected by many conditions, such as temperature and salinity. These currents influence the weather and climate in the areas around them. Design an experiment to test one of the following. Temperature affects the density of water. Salinity affects the density of water. Use the following headings in your experiment: hypothesis, aim, materials, method, results, discussion, conclusion. You may need kitchen spoon salt food colouring large drinking glasses thermometer or data logger digital camera ICT This might help 1 Remember to devise a fair test. Identify your independent and dependent If you have made variable, as well as your control. a movie of your 2 How are you going to record your results? discovery, upload this to the class wiki. 3 How does your prediction compare with the results? 4 What can you conclude from your investigation? Gulf Stream a relatively warm ocean current flowing north-eastwards off the Atlantic coast of the United States The global ocean circulation between deep colder waters and warmer surface waters strongly from the Gulf of Mexico influences world climates. Scientists think that melting Arctic sea ice and increased precipitation Humboldt Current will bring enough fresh water into the North Atlantic to change the ocean currents. As this fresh water hits the currents, the water becomes more buoyant and travels across the surface. a cold ocean current of the South Pacific, flowing north along the Currents move water worldwide, so they have a significant impact on the weather. For western coast of South America example, the Gulf Stream originates in the warm waters of the Gulf of Mexico and moves northwards, warming Europe more than other places at similar latitudes. The Humboldt El Niño Current, a cold current off the coast of Chile and Peru, creates an area suitable for many a period of extensive warming of organisms, but also keeps the coast of Chile quite cool and arid. the central and eastern Pacific Ocean that leads to a major shift in When the current is warmed, the resulting climatic changes are known as El Niño. It is seen weather patterns across the Pacific as an extended period of warmer oceanic waters in the central and eastern tropical Pacific Ocean, 344 ISBN 9780170231510  Chapter 8 Global systems La Niña which leads to drier terrestrial conditions on the western edge of the Pacific, including Australia. The cycle lasts 3–5  years and explains the drought experienced by Australia during the 2000s. a period of cooler-than-average sea surface temperatures in the central La Niña is a period of cooler-than-average sea surface temperatures in the same part of the Pacific. and eastern tropical Pacific Ocean El Niño affected marine plants in the Galapagos Islands because the water temperature increase did not suit their growing habits. This led to the decimation of the marine iguana population on the East Australian Current islands’ fringes as the iguanas relied on the marine vegetation for food (Figure 8.21). As the iguanas an oceanic current that carries a died off, the other wildlife associated with them moved on or died out. Numbers of seabirds nesting on stream of warm water from the Coral Sea into the cool waters of the islands declined significantly but land birds thrived and lived exclusively on seeds and nuts. the Tasman Sea; it is the largest Closer to home, the East Australian Current brings warm surface waters to the east ocean current around Australia coast as far south as Tasmania. The surface waters are warmed in the tropical waters of the Coral Sea and then travel south along the east coast of Australia, bringing with them many species such as tuna and sea turtles as far as Bass Strait. Shutterstock.com/Ryan M. Bolton Figure 8.21 The number of Galapagos marine iguanas has decreased as marine vegetation has died out due to El Niño. ACTIVITY 8.11 WORKSPACE What do the media say? What do the media say? In groups of three or four, collect two days’ worth of newspaper articles on the environment, or collect a series of online articles. 1 Categorise the articles under the following headings. Greenhouse effect Ozone layer depletion Rising sea levels Loss of biodiversity Other categories 2 Use the articles to describe the opinions of: a scientists b politicians c the general public. 3 Choose one article and identify information that you think is incorrect. Outline the scientifically correct information. ISBN 9780170231510 345 nelson ACTIVITY 8.11 4 Describe why you think information from the media is not always accurate. 5 Define ‘sustainability’. 6 Evaluate how the problems in Question 1 may affect the ongoing sustainability of life on the planet. 7 Propose a solution to the problem you evaluated in Question 6. WOR