Different places on Earth experience frequent extreme weather events such as very high winds, high rainfall in a short space of time, or long spells of extreme heat with no rainfall. With little or no warning, people can have their homes destroyed or their own lives threatened. Scientists predict that as the Earth’s climate warms, there will be more of these events and they will get more extreme. In this chapter we look at a natural cycle, the carbon cycle, and how it has been affected by human activities, and consider some of the effects of climate change. i You will learn about: * The carbon cycle, including the natural parts of the cycle and the parts affected by human activities The measured and predicted effects of climate change You will build your skills in: Planning investigations Making risk assessments Deciding what equipment to use for investigations Describing the use of science in society, industry and research Evaluating issues using scientific understanding Discussing the global environmental impacts of some uses of scienceYou will learn: * To describe how photosynthesis, respiration, The carbon cycle Maeding, decompostion 4 combustion make up the carbon cycle Starting point You should know that. The Earth's climate can change due to a change in the mixture of gases in the atmosphere ; Carbohydrates including glucose are stores of You should be able to... " plan an investigation while considering trol variabl | independent, dependent and ¢ Make risk assessments for practical work energy for animals and plants — bo ele eeteeC CE te BCs Fanaks a conclusion from results 13.1 Photosynthesis ace aneere toned 232 Climate changein photosynthesis, plants use energy from sunlight to create food in the form of sugars from carbon dioxide taken from | the air and water. 13.2 Photosynthesis. The overall reaction involved is carbon dioxide + water > glucose + oxygen Note two very important aspects of this chemical reaction: 1 Plants make their own food in this way in parts of cells (organelles) called chloroplasts. Other organisms including animals and bacteria lack chloroplasts and so do not make their own food. They have to find food from other sources to provide the energy they need to live. This is why so many animals eat plants. Some animals eat other animals, but those other animals will have eaten plants, so the energy all animals need comes mainly from plants. One way or another, plants and animals get the energy they need to live from nutrition. 2 Photosynthesis is a very important reaction when considering climate change. In photosynthesis, carbon dioxide is taken out of the atmosphere and replaced by ‘oxygen. Plants therefore act as a natural way of storing carbon dioxide, also called a sink. Making links In Stage 9 Biology, you learnt that photosynthesis occurs in plant cells called chloroplasts. a) Name the substance present in chloroplasts that has to be present for photosynthesis to occur. b) Describe the source of energy needed for photosynthesis. Key terms nutrition: life process by which plants and animals take in and break down substances and use them to get the nutrients needed for other life processes. sink: something that takes in and stores significant quantities of a particular substance (for example, plants act as a sink for carbon dioxide).Respiration is a general name given to the process by which Key terms living organisms release energy through the conversion os ' of glucose and oxygen to carbon dioxide and water. In decomposition: process eukaryotic organisms respiration takes place in parts of cells in which bacteria and called mitochondria. fungi feed on dead en a ae animals and plants. In plants, the respiration is usually aerobic respiration, meaning that oxygen and sugars are the reactants. The mitochondria’ overall chemical reaction involved is organelles (parts) in cells sea where respiration occurs. glucose + oxygen > carbon dioxide + water respiration: process by which organisms release energy through the conversion of glucose and oxygen to carbon Animals also respire at all times, and mostly use aerobic dioxide and water. respiration, just like plants: Plants respire at all times, as they need the energy from sugars to stay alive. No sunlight is needed for respiration, so Plants respire at night as well as during the day. This process releases carbon dioxide into the air. source: something that glucose + oxygen > carbon dioxide + water produces significant * i ew . quantities of a particular This reaction releases carbon dioxide into the air. eeaaea turer In most bacteria, aerobic respiration also occurs, producing animals and plants act as a carbon dioxide and water just as in plants and animals. source for carbon dioxide) Many forms of bacteria and other organisms use dead plants and animals as sources of energy for respiration. The plant or animal's body is decomposed by bacteria and other organisms, releasing carbon dioxide to the atmosphere. Note how aerobic respiration by all types of organisms results in carbon dioxide being added to the air. We say that respiration is a source of carbon dioxide, just as photosynthesis is a sink of carbon dioxide. We can build up our knowledge of photosynthesis and respiration to create a core part of the carbon cycle: 234 Climate change13.3 Photosynthesis and respiration together form the most important natural parts of the carbon cycle. Each arrow represents a movement or transfer of carbon. Photosynthesis takes in carbon dioxide and acts as a sink. The different organisms that use respiration produce carbon dioxide and act as sources. When considering climate change, we also need to understand the effects of human activities on the atmosphere. The history of human effects on the atmosphere goes back to the discovery of combustion, when early humans burned wood Making links In Stage 8 Biology you may have learned that aerobic respiration is an essential reaction for living things. a) In which organelles (parts) of cells does aerobic respiration take place? b) Are these organelles present in plant cells, animal cells or both plant and animal cells?and other materials from plants to produce energy for heat and for cooking food. Wood burning is a source of carbon dioxide, because wood is made of molecules containing carbon ‘that react with oxygen: wood + oxygen -> carbon dioxide + water Over time, humans discovered that coal, oil and natural gas (methane) produced much more energy than wood when they were combusted. Alll three of these materials are called fossil fuels, because they were formed over millions of years when layers of sedimentary rock squeezed the bodies of dead plants and animals. All of these fuels are made from molecules containing only atoms of carbon and hydrogen, so they are part of a family of molecules called hydrocarbons. Some skeletons or structures of organisms were preserved in this process, and these preserved organisms are what we call fossils. The combustion of these fossil fuels produces significant amounts of carbon dioxide. For example, methane reacts as follows: methane + oxygen -> carbon dioxide + water Coal and oil contain hydrocarbon molecules with more carbon atoms than methane, so burning coal and oil produces more carbon dioxide. This process gives rise to another part of the carbon cycle. fenergy ‘carbon dioxide CO, ‘atmosphere ‘emissions. from vehicles 434 Human activities also contribute to the carbon cycle, Key terms fossil fuels: compresseq remains of dead organisms that can be burned to release energy, including methane (natural gas), coal and oi hydrocarbon: substance containing molecules made only of carbon and hydrogen. Making links In Stage 8 and 9 Chemistry you may have learned that combustion is a chemical reaction that involves the transfer of energy. a) Write a word equation that describes the combustion of coal (assume that coal is pure carbon) b) Does this reaction take in or give out energy? Explain your answer. 236 Climate change_ Which reaction, photosynthesis or respiration, is combustion most similar to? Explain the similarities and differences. 0 If an experiment catches fire in a school laboratory, there are different ways of stopping the fire. A class of students suggests the following methods. Analyse each suggested method, say whether it is a useful mete and, if it is useful, explain how it would work. a) Spray water on the fire. b) Spray carbon dioxide gas on the fire. ©) Spray oxygen on the fire. d) Place a thick blanket over the fire. Rk ckeriee tty Figure 13.5 brings together the natural parts of the carbon cle and the parts more recently created by human activities. Note that the substances involved in the cycle are mostly compounds containing carbon, not carbon as an element. This diagram does not show a complete carbon cycle. There are other processes that you will study in the years ahead which also affect the amounts of carbon-containing substances. For example, some carbon dioxide in the atmosphere dissolves into the oceans. This means that the ©ceans are an important sink of carbon dioxide. Climate scientists make predictions about how the Earth's climate will change by estimating the amounts of carbon dioxide produced or taken in by each of the processes shown in the carbon cycle. They can check these predictions Measuring the amount of carbon dioxide in the atmosphere at locations all around the world, and by using Weather satellites to monitor temperatures in the different Tegions of Earth.Over 97% of scientists agree that: The amount of carbon dioxide in the atmosphere is increasing. * Much of this increase is due to human activities. © This has already caused the average temperature to rise, and it will continue to rise until more carbon dioxide is taken out of the atmosphere than is put in. 13.5 The carbon cycle. Neen eee 238 Climate changev ocho iid i a carbon dioxide, water and sunlight produces oxygen and energy-storing _ sugars such as glucose. 7 v Respiration is the process by which 4 pone eas pany through the -conversi glucose and oxygento | carbon dioxide and water. ra i v Bacteria and fungi feed ondead a and plants in the process called Check your skills progress: | * I can plan investigations to test reactions in the carbon cycle including photosynthesis and respiration. I.can decide what equipment is required to carry out an investigation and use it appropriately. * can carry out practical work safely and identify risks.| | I You will learn: | ora dau «To describe the impacts of climate change, including Impacts of climate sealevel change, loedia, | drought and extreme change weather events To predict and test the outcome of a scientific enquiry To plan investigations To decide what equipment is needed for an investigation and use it correctly To evaluate the reliability of secondary information Starting point Ruy Ruel Be Brel hades Earth's climate is changing due to changes in __ Use a range of secondary information sources to the mixture of gases in the atmosphere | research and select relevant evidence to answer questions cae Make predictions based on scientific knowledge Climate describes averages in atmospheric conditions over large areas and long periods of time, but weather describes atmospheric | conditions in local areas over short periods of time | The Earth's climate goes through a cycle, from warm periods to ice ages and back again, over_| many thousands of years | ‘A drought occurs when there is very low rainfall in an area for a long period of time. This can affect plant and animal life in the area. It can also affect humans if the water that is stored in reservoirs or wells runs out. Key terms drought: unusually long period with low or no ‘As the Earth’s average temperature rises due to increasing rainfall, causing water levels of greenhouse gases, particularly carbon dioxide, shortages, long-term patterns in weather are changing. This means : thot sone areas of the Earth Have greatly reduced levels vlld fires: large fires of rainfall in the hottest months of the year, leading to in natural areas, which spread quickly due to dry droughts that are longer and more severe. ede Tee cio In some areas these droughts lead to large areas of dead or made worse in a drought dry vegetation, which may catch fire. You may have seen coverage of these wild fires in places such as California, in the US, and Australia. These fires appear to be growing in intensity and are occurring more often. 240 Climate changescience in context: Droughts in Malawi Malawi is an African country that is affected regularly by drought. The land in Malawi varies greatly in height (between 0 m and 3000 m) and about one-fifth of the area of the country contains lakes. Lake Malawi extends for two- thirds of the length of the country. These factors together affect how much rainfall Malawi receives. About 75% of the population in Malawi work on farms, so a year of very low rainfall that results in drought causes severe problems ~ there is less work for workers to do (so less income), and less food produced. A scientific study found that over a period of 55 years, there were four serious droughts and two severe droughts. A severe drought is where the government has to ask for help from other countries. Science has an important role in analysing the effects of droughts and determining the causes, By analysing data from previous years, scientists can predict when changes in weather patterns may lead to drought before its effects take hold. This can help governments and people prepare so that the worst effects of drought can be reduced. For example, the United Nations Food and Agriculture Organization has developed a project that aims to help 22.000 people in at-risk areas of Malawi. The project reacts to scientific forecasts of drought to distribute fast-growing and drought-tolerant crop seeds, and to vaccinate farm animals to prevent outbreaks of disease. The project also sets up small-scale irrigation (watering) systems and education to help reduce water wastage. 13.8 Lack of rain stunts the growth of maize plants in Malawi. ve some years where there is less rage. Explain why experiencing bhwaiats 13.6 In periods of drought, rivers run dry and the ground dries out. 13.7 Long, hot periods of drought lead to wild fires. Making links You may have learned that plants and animals can be affected severely by drought. a) In areas affected by drought, some wild plants continue to grow but crops are usually quite badly affected, Suggest why drought affects some plants and not others. b) Suggest two ways in which animals living in areas affected by droughts can cope with the extreme conditions.ee Your teacher will give you four plastic or waxed paper cups containing soil and a packet of bean seeds, ; 1 Your task is to demonstrate the effects of drought on plants by comparing the growth of bean seedlings that are given different amounts of water. Decide how you will set up the four pots to show the differences in growth. Think about how much water each pot should get and how often. 2 One of the cups should be regularly watered with normal amounts of water, so that you can compare the other pots to this one. 3 Decide what you will measure each day to show the differences in plant growth, if any are found. 4 Predict how each cup of seedlings will develop. 5 Observe the seedlings for up to 10 days. Record your measurements and observations each day. Include diagrams or photos in your observations. 6 Write a conclusion that describes the effects on seedling growth of different amounts of water. A1 Which variables were controlled to make it a fair test? How were they controlled? A2 What did you decide to measure and observe? A3 Did any seedlings show very little or no growth? Suggest why this happened. 4 Explain what effects drought can have on the growth of crops. It is easy to see how a warmer average temperature can lead to hotter, drier spells of weather. What is not so obvious is that rising temperatures can also lead to more periods of heavier rainfall in some places. Longer spells of higher temperatures over oceans cause more water to be evaporated to form clouds. When these clouds pass over land, there is more water to fall as rain. Many countries around the world are finding that intense periods of ; heavy rainfall causes rivers to overflow and break through 122, Tens near rivers can flood defences, causing flooding in built-up areas more often: Pineal tt Pétlods of extrame De eat eins cis eaten tg 242 Climate change| | | | guilding flood defences such as higher river banks and using pumps to channel water away from built-up areas are expensive activities. Governments across the world will have to set aside more money to defend asa, i wpe mide more gainst floods as climate SG CUSee Tt Penn teres Soni eels You should remember from Stages 7 and 8 that increasing levels of carbon dioxide and other greenhouse ake gases in the atmosphere causes ice at the poles and in glaciers to melt faster. In turn this leads to rising sea levels. Countries with long coastlines and island countries are already experiencing these rising sea levels. Examples where governments are already planning for rising sea levels: * City of Osaka in Japan, where it is estimated that 5.2 million people may have to move to other places to live, because where they currently live will be under water as sea levels rise : * Shanghai, China, which is one of the cities '*10 “e%2nd”2 in Eaypr and the Nile Delta, most vulnerable to flooding due to a rising sea level * Alexandria in Egypt, where 3 million people could be affected, as well as large areas of farming land in the Nile river delta Figure 13.10 shows a map of the area around Alexandria. The city stands at the edge of the Nile Delta, a very large area of low-lying land. The Nile is Africa's longest river and it carries large amounts of soil, sand and organic matter along its length. As it approaches the Mediterranean Sea, the river spreads out and flows more slowly. The soil, sand and organic matter are deposited over a wide area, creating land that is rich in nutrients and ideal for farming.Because the land is low-lying, even small rises in $63 ee Making links will flood large areas. The shaded areas in figure 1 bs a cs the land that will be permanently flooded by 2070 if n in Stage 8 Chapter 11 flood defences are developed. you may hase learned Because it takes time for the climate to change after the about at s es ot ; amount of carbon dioxide in the atmosphere changes, eet climate 4 Ing ac t land if all countries now stopped producing more carbon dioxide, nations. ng levels it would still take many years before the sea level reached a are of ort concern to peak. This is because the effect of increased carbon dioxide countries that contain on temperature takes time, often several years. goes et See uch a: Governments of major coastal cities can prepare for sea level He Seychelles. changes in a number of ways, including: a) Suggest why these * building flood defences such as sea walls, moveable Rr ralcngee barriers, major new drainage channels and areas of particularly worried jane oe the city that flood water can be diverted about the effects of climate change. b) Explain the difference between changing sea levels due to ice age ae cycles and the present * only developing buildings in areas that are sufficiently changing sea levels. far from or above the likely water levels * developing warning systems that alert people at times the city is at increased risk (such as during spring tides or when major storms are approaching), so that people are ready to evacuate from at-risk areas + recruiting and training emergency services ready to respond to major flooding events Activity 13.2: Investigating the effects of climate change on Shanghai Shanghai in China is one of the world’s largest cities, with a population of over 24 million. The main part of the city is built on land next to the sea and the land rises only a few metres above sea level. This access to the sea has allowed Shanghai to become ‘the world’s busiest container port. It is also a global financial hub for major banks and investors. A1 International teams of scientists have rated Shanghai as the world’s most vulnerable city to the effects of climate change. Suggest how Shanghai could be affected by climate change. A2 If the Earth’s average temperature rises by 3°C then three of Shanghai would need to move to avoid beil could be done to prevent this happening. A3 Explain why governments need to respond to climate change. AA Find a map of Shanghai and investigate flooded if no defences were being built, 13.11 City skyline of Shanghai. ‘quarters of the population ing flooded. Suggest three things that plan many years ahead when working out how to online how much of the city could be 244 ~~ Climate changeet esse a acd The general effect of a rising average temperature is that the Earth’s atmosphere acts as a store of more energy. Although the detail of what types and times of events are very difficult to predict, scientists are confident that the raised energy will mean there will be more extreme weather events. What is an extreme weather event? This is something where ‘one or more weather conditions are significantly different to the average or expected peak values. Examples we have already described include: + drought * floods Other examples include: * hurricanes, where wind speeds are over 33 m/s and can go as high as 70 m/s, accompanied by intense rainfall * heat waves, where temperatures might be so high they threaten life * cold spells, where temperatures are so low they threaten life Some of these events can occur in most places around the world, such as flooding, but hurricanes tend to occur only in certain parts of the world due to the patterns of air circulation in the atmosphere and because of local Conditions.Making links i Remember the difference between climate and weather. Classify the following events or patterns as changes in clim or as weather events. ate a) hurricanes b) a rise in average temperature ©) a heat wave d) a rise in sea level ) one day of flooding due to recent heavy rainfall mee eect) i long the south In August 2005, a powerful hurricane moved from the sea onto land al : coast of the United States. Although many areas along the coast had walls designed to broken by the power of Hurricane protect against sea flooding, these defences were Katrina, Many people were evacuated from their homes before the storm reached the shore, but despite this, over 1800 people were killed. The cost of repairing the damage caused made it the costliest natural disaster in the history of the US. 13.12 Thousands of homes were damaged by high winds, heavy rain and sea flooding. A1 Use internet research to find out facts about Hurricane Katrina. Make sure to record which websites you used for each fact and comment on whether you think each website is a reliable source of information. Include in your findings: a) the estimated maximum strength of the winds produced by Katrina b) why New Orleans was flooded when it had flood defences ©) the meaning of the term ‘storm surge’ and how it is connected with hurricanes d) the estimated total cost of damage caused by the hurricane ‘A2. Some people have suggested that the power of Hurricane Katrina was worse because of global warming. Do you agree? Explain your answer. ‘A3 Decide whether you think there will be more or fewer storms like Katrina i 50 years. Explain your answer. etna in che new 246 Climate changev Extreme weather events include hurricanes, long spells of very he: rainfall leading to Check your skills progress: + Ican make and test predictions about the effects of lack of water on plants. * can choose and use equipment for a scientific investigation. * I can evaluate the reliability of secondary sources of information. Impacts of climate change 247End of chapter review Quick questions 1, What diagram shows the connections between photosynthesis, respiration, decomposition and combustion? a the nitrogen cycle b an energy level diagram ¢ the carbon cycle d apie chart showing the percentages of gases in the atmosphere 2, Name the process that involves cells in living organisms taking in oxygen and producing carbon dioxide. a photosynthesis b respiration © combustion d decomposition 3. Name the process that takes in carbon dioxide and produces oxygen. a photosynthesis b respiration combustion d decomposition 4. Name the process that contributes significant amounts of carbon dioxide to the atmosphere due to human activities. a photosynthesis b respiration ¢ combustion d decomposition 5. (a) Describe two effects that drought can have on plants. (b) Explain why droughts have a much greater effect on countries that raise most of their income from farming. 6. A local council is planning to build flood defences. To estimate the height of wall they need to build, they look at the local records and plan a wall that wild just have prevented the highest flood on record in that area. (2) Explain why this height may not be enough. (b) Prepare an argument to present to the council t. i 5 means they may need to build higher defences, re” WHY climate changeConnect your understanding 7. (a) Suggest two reasons why people often build cities near to coastlines. (b) Describe two effe it cts of climate change that will most affect cities near to coastlines. (©) Suggest three Ways in which people in cities can Prepare for these effects. 8. (a) Look at the carbon cycle in figure 13.5. The parts of the cycle that have downwards-pointing arrows show carbon dioxide sinks. Explain what the term ‘carbon dioxide sinks’ means (b) What do the upwards-pointing arrows represent? (©) Describe the trend in the arrows that represent human activities. (d) Explain why this trend is important for the Earth’s climate. 9. The table shows the average rainfall for a year for four different locations, taken ‘over a 50-year time span. The second row shows the total rainfall for each region in 2018. Location 1 zZ 3 4 Average rainfall per year (mm) __1200 600 200 2100 L Total rainfall in 2018 (mm) 120 400 160 1900 (a) Suggest which region or regions is/are most likely to have suffered a drought in 2018. Give a reason for your answer, (b) Give two effects of drought that affect people. (©) Explain why continuing climate change means people should expect more frequent and more severe droughts, 10. A student says that respiration is the reverse of photosynthesis. (a) Write the word equation for photosynthesis. (b) Write the word equation for respiration that the student is referring to, (0) Explain why the student is wrong, (Hint: think about other substances involved in the reactions.) (a) Which reaction helps to reduce the amount of carbon dioxide in the atmosphere? (e) Explain why the reaction described in part d may be important for our survival.11. Figure 13.13 shows an incomplete carbon cycle. 13.13 The carbon cycle. (a) Three labels are missing from arrows or ovals. Complete these labels. (b) Three arrows and their labels are missing. Draw in these arrows and label them with the name of the process involved. (©) Use this diagram to explain why human activities are contributing to climate change. Challenge question 12. Some scientists are working on methods of capturing the gases produced by human activities and reacting the carbon dioxide with substances so that it can be stored underground. (a) Suggest where this would appear on the carbon cycle diagram. (b) Predict the effect of this process on the rate of climate change.