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Infection and response
Organisation
Cell biology
Biological molecules
Homeostasis and response
Responding to change (a2 only)
Energy transfers (a2 only)
The control of gene expression (a-level only)
Substance exchange
Bioenergetics
Genetic information & variation
Inheritance, variation and evolution
Genetics & ecosystems (a2 only)
Ecology
Cells
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1f industrialisation and the people: britain, c1783-1885
1c the tudors: england, 1485-1603
Britain & the wider world: 1745 -1901
Inter-war germany
World war one
2n revolution and dictatorship: russia, 1917-1953
World war two & the holocaust
1l the quest for political stability: germany, 1871-1991
The cold war
2j america: a nation divided, c1845-1877
Medieval period: 1066 -1509
The fight for female suffrage
2m wars and welfare: britain in transition, 1906-1957
2d religious conflict and the church in england, c1529-c1570
Britain: 1509 -1745
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16/04/2023
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Greenhouse gases Greenhouse gases in the atmosphere maintain temperatures on Earth high enough to support life. Water vapour (H₂O), carbon dioxide (CO₂) and methane (CH₂) are greenhouse gases Greenhouses • Greenhouses allow short- wavelength radiation from the Sun through But the glass absorbs the long-wavelength radiation emitted from inside the greenhouse • This keeps the plants inside the greenhouse warm. ● Short wavelength heat radiation from the Sun Sun العالم Re-radiated long wavelength heat radiation The greenhouse effect 1. The Sun emits short- wavelength radiation e.g. ultraviolet light, which warms the Earth 2. The Earth loses heat by emitting long- wavelength radiation e.g. thermal infrared. TautatioIT The greenhouse effect 3. Greenhouse gases absorb some of the long-wavelength radiation 4. They re-radiate this thermal radiation in all directions, including back to Earth. This warms the atmosphere. Infrared Radiation SUN Atmosphere 1. Solar Radiation passes through the atmosphere GREENHOUSE GASES & Earth warms and @mits infrared EARTH 0:00 3, Infrared radiation is absorbed by greenhouse gases and re-radiated in all directions The Greenhouse Effect Some solar radiation is reflected by the Earth and the atmosphere. Most radiation is absorbed by the Earth's surface and warms it. Some of the infrared radiation passes through the atmosphere. Some is absorbed and re-emitted in all directions by greenhouse gas molecules. The effect of this is to warm the Earth's surface and the lower atmosphere. Atmosphere Earth's surface Infrared radiation is emitted by the Earth's surface. The greenhouse effect Without the greenhouse effect, Earth would be too cold to support life. But humans are increasing the levels of greenhouse gases in the atmosphere, which is warming the Earth too much. Greenhouse gases Summary Greenhouse gases in the atmosphere maintain temperatures on Earth high enough...
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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?