Global Warming

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to support life. Examples of greenhouse gases are: • Carbon dioxide • Water vapour • Methane Visible light — Infra-red Absorbed then re-radiated Visible light with a short wavelength is absorbed by the Earth, it is then re-radiated as longer wavelength infra red Infra-red Trapped in atmosphere warming it up The longer wavelength infra red cannot penetrate through the greenhouse gas layer in the atmosphere which contains carbon dioxide and methane. • Based on peer-reviewed evidence, many scientists believe that human activities will cause the temperature of the Earth's atmosphere to increase at the surface and that this will result in global climate change. However it is difficult to model such complex systems as global climate change. This leads to simplified models, speculation and opinions presented in the media that may be based on only parts of the evidence and which may be biased. Human activities Human activities increase the amounts of: ● • Carbon dioxide Methane in the atmosphere. 1. Burning fossil fuels for electricity/running cars e.g. combustion of propane: Write the word and balanced symbol equations in your notes. Propane + oxygen carbon dioxide + water C3H₂ + 50₂ → 3CO₂ + 4H₂O 2. Deforestation. Cutting down trees reduces the amount of CO₂ absorbed from the atmosphere by photosynthesis Human activities Human activities increase the amounts of: ● Carbon dioxide • Methane in the atmosphere. IT WASN'T ME... 1. Cattle producing methane. Cattle reared for humans (to eat as beef or for milk) produce methane 2. Landfill sites. The decay of waste in landfill by microorganisms produces methane. Climate Change Global warming Most scientists believe that human activities will cause the { temperature of the Earth's atmosphere to increase at the surface and that this will cause global climate change. Global warming will cause climate to change (storms, extreme hot/cold weather etc.) Peer-reviewed evidence The peer-review process stops scientists publishing opinions rather than hard evidence. This is based on peer-reviewed evidence. Other scientists (peers) checking the evidence before it is published. Scientists collecting and analysing data (evidence) Peer-reviewed evidence -Temp -CO2 why t AND 1850 1860 1870 1880 1890 1900 1910 1920 1930 1940 1950 1960- 1970 1980 1990 How does this graph show that human activities are causing global warming? tyrrh 2000 2010 A tiny minority of scientists and many non-scientists think that the CO₂ is not causing the increase in temp. Our knowledge of the greenhouse effect suggests that CO₂ does cause global warming. ● ● Modelling Climate Change Scientist has hypothesis Scientist collects data and writes computer program model = Model 'predicts' future Modelling something as complex as climate change is difficult! Scientists have a duty to report any uncertainties in their models. Non-scientists with a vested interest may present a biased opinion based on only part of the evidence in the media. Effects of Global Climate Change 1. Flooding 2. Extreme weather 3. Changes in rainfall 4. Extinction Effects of Global Climate Change 1. Flooding As average global temperature increases: ● Polar ice caps melt Sea level rises Flooding of land results • Flooding causes coastal erosion/habitat loss Effects of Global Climate Change 2. Extreme weather Extreme weather events more common and severe e.g. storms • Causes damage Effects of Global Climate Change 3. Changes in rainfall How much rain When it occurs ● • Where it occurs 1. 2. 3. Heavy rain can damage crops. Lack of rain causes drought. Affects food production. Effects of Global Climate Change 4. Extinction As climate changes rapidly, animals and plants cannot adapt to the environment quick enough and die out. Rodent species on Great Barrier Reef island - first mammal to become extinct due to climate change Global climate change the carbon footprint and its reduction - Summary An increase in average global temperature is a major cause of climate change. There are a number of potential effects of climate change: Rising sea levels causing flooding Desertification Droughts Ice caps melting The carbon footprint is the total amount of carbon dioxide and other greenhouse gases emitted over the full life cycle of the product, service or event. The carbon footprint can be reduced by reducing emissions of carbon dioxide and methane. Carbon Footprints The carbon footprint of a service, event or product is a measure of the amount of greenhouse gases it is responsible for emitting during its lifetime. Calculating carbon footprints is rarely straightforward due to the sheer number of factors that must be taken into consideration. Reducing Carbon Footprints The following are steps that can be taken to reduce carbon footprints: • Maximise efficiency of energy use and minimising waste. • Use renewable energy sources. • Governments could deter companies from choosing high emission strategies by imposing: Emission-based taxes. Caps on emissions. Licenses for emissions up to that cap, which must be purchased. • Use carbon capture and storage (CSS) technology. Carbon, in the form of carbon dioxide produced by burning fossil fuels, is captured prior to its release into the atmosphere. The captured carbon is then stored deep underground. ● ● ● ● Carbon off-setting. This involves planting trees, which will remove carbon dioxide from the atmosphere through photosynthesis, thus compensating for emissions. Encouraging consumers to purchase carbon-neutral products, which, as the name suggests, do not change the atmospheric carbon dioxide concentration. However, in reality, there are many barriers to reducing carbon footprints. These include: Disagreements in the scientific community regarding climate change and its causes and consequences. ● ● Many governments harbour concerns that making the required changes may restrict the economic development of their country, thus jeopardising the health of their population. Understandably, this attitude is particularly prevalent in developing countries. Different countries have different opinions regarding the right course of action. This spreads uncertainty over what each country will do when presented with a potential international agreement, thus increasing the reluctance of countries to commit to signing anything. • Reluctance of people in developed countries to alter their lifestyles. • Insufficient education of the general public on the importance of making proposed lifestyle changes. Questions 1. Greenhouse gases are believed by many scientists to be responsible for global warming. Why might these gases be useful? 2. Methane is a greenhouse gas. Name two other greenhouse gases. 3. Visible light can penetrate the greenhouse gas layer, however infra red cannot. Explain why. 4. Name two human activities that increase the amount of methane in the atmosphere. Questions 1. What is a major cause of climate change? 2. Give three possible effects of climate change. 3. What is the carbon footprint? 4. How can the carbon footprint be reduced?