2 Objectives Students should learn: that increasing levels of carbon dioxide and methane contribute to global warmingthat an increase in the Earth’s temperature may cause changes in the climatethat an increase in temperature may also reduce biodiversity and cause changes in the distribution of species.
3 Outcomes Most students should be able to: explain what is meant by ‘the greenhouse effect’describe how increasing levels of carbon dioxide and methane contribute to global warmingdescribe some of the consequences of global warming.Some students should also be able to:evaluate the impact of the greenhouse effect on conditions on the Earth.
4 SpecificationLevels of carbon dioxide and methane in the atmosphere are increasing and contribute to ‘global warming’. An increase in the Earth’s temperature of only a few degrees Celsius:– may cause big changes in the Earth’s climate– may cause a rise in sea level– may reduce biodiversity– may cause changes in migration patterns, e.g. in birds– may result in changes in the distribution of species.Carbon dioxide can be sequestered in oceans, lakes and ponds and this is an important factor in removing carbon dioxide from the atmosphere.
6 Answers to in-text questions Biology B3 4.5Global warningAnswers to in-text questionsa Deforestation so less removed, burning fossil fuels producescarbon dioxide.b Any two of: carbon dioxide, methane, water vapour.Summary answers1 carbon dioxide/methane, methane/carbon dioxide, atmosphere, global warming, temperature, climate, biodiversity2 a Look for an accurately drawn bar chart from the figures given, correctly labelled axes, neat columns etc.b Levels of carbon dioxide have risen steadily since 1970 as a result of deforestation, burning fossil fuels, etc.c The Sun’s energy heats the Earth. Much of this is reflected back into space but some is absorbed by greenhouse gases which re-radiate it back. Therefore the Earth’s surface is kept warm enough for life. Increased levels of greenhouse gases leads to excess warming. This could result in climate change such as more extreme weather events. Melting of polar ice capsmay also increase sea levels and flood low-lying land.3 Look for accurate information and good examples.
9 increasing levels of carbon dioxide and methane contribute to global warming With increasing levels of carbon dioxide it means that the natural sinks cannot work at a fast enough rate. This leads to a build up of CO2 in the Earth’s atmosphere, causing something we like to call “The Greenhouse Effect”.Natural sinks are Oceans and through photosynthesis.
10 What is The Greenhouse effect I hear you ask? When the Sun’s energy reaches Earth, much of it is radiated back out into space. However, gases such as Carbon Dioxide and Methane absorb this radiation, trapping it on Earth. As a result of this, the Earth is insulated and heats up.
12 that an increase in the Earth’s temperature may cause changes in the climate Changes in climate: Due to Global Warming we are likely to see an increase in severe and unpredictable weather conditions.Changes in Sea Levels: With Earth warming, the polar ice caps in the North and South poles are melting. This increases the capacity of water in the oceans therefore causing sea levels to rise.
13 an increase in temperature may also reduce biodiversity and cause changes in the distribution of speciesAs climate change changes, some organisms will be unable to survive in the new conditions, e.g. the lost of polar bears as the ice melts.Some animals distribution may increase as it makes conditions more favourable or some shrink in distribution as the conditions aren’t as favourable. Some may disappear completely from areas or move to new locations
14 ‘fun’ activity Give out the show me board and pens Ask the form to close their books and draw and label as accurately as they can the diagram to show how global warming occursNow show the slide with the picture on and see who is best
15 More of the heat is trapped, causing the temperature to rise Some of the heat is absorbed by greenhouse gases and reflected back to earthInfrared radiation from the earth escapes out the atmosphereLight Rays from the sun heat the surface of the earth which turns the short waves from the sun into longer waves as infrared.
16 Global warming and greenhouse gases One of the greatest threats caused by air pollution is global warming. Global warming is caused by a build-up of greenhouses gases, which leads to an increase in the Earth’s temperature.A greenhouse gas is an atmospheric gas that absorbs infrared light.Key greenhouses gases include:carbon dioxide (CO2)Teacher notesSee the ‘Climate Change’ chemistry presentation for more information on greenhouse gases, the greenhouse effect and global warming.methane (CH4)water vapour (H2O)nitrous oxide (N2O)
17 The greenhouse effect Teacher notes This four-stage animation can be used to illustrate the principles of the greenhouse effect. Students could be asked to consider the impact of rising greenhouse gases on the natural phenomenon of the greenhouse effect.
18 Atmospheric carbon dioxide Teacher notesThis graph was produced using data sourced from the Mauna Loa Observatory, Hawaii, courtesy of NOAA (the National Oceanic and Atmospheric Administration). More information about atmospheric gases is available at
19 Carbon dioxide levelsCarbon dioxide is one of the most important greenhouse gases because atmospheric concentrations have risen dramatically over the past century. Why do you think this is?Burning fossil fuels, deforestation and flooding land for the construction of hydroelectric dams have all contributed to rising levels of carbon dioxide.How many examples of burning fossil fuels can you think of? Are there any alternatives?