Summary of topic 6


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Summary of topic 6

  1. 1. Topic 6 The Issue of Global Warming
  2. 2. The Role of Greenhouse Gases • The average temperature on the Earth is 15oC • Incoming radiation is low wavelength/ high energy • The average temperature is maintained by atmospheric gases trapping or reflecting a fraction of the outgoing (long wavelength/ low energy) heat radiation • These (greenhouse) gases include: – Water vapour (H2O) – Carbon dioxide (CO2) – Methane (CH4) – Ozone (O3) – Nitrous oxide (N2O)
  3. 3. The Role of Greenhouse Gases Without these naturally occurring greenhouse gases, the average temperature of the Earth would be approximately -15oC
  4. 4. Change in Global Temperature Over Time This data is taken from measurements of the concentration of the oxygen isotope 18O in air bubbles trapped in rock and ice. This concentration is temperature dependent but can only be used to give an indication of temperature change rather than a measurement of temperature itself
  5. 5. Change in Global Temperature Over Time
  6. 6. Change in Global Temperature Over Time
  7. 7. The Role of Carbon Dioxide • Earth’s atmosphere today ≈ 380 ppm CO2 (0.038%) • Early Carboniferous Period ≈ 1500 ppm CO2 • Middle Carboniferous Period ≈ 350 ppm CO2 • Earth’s atmosphic temperature today 15oC • Early Carboniferous Period 20oC • Middle Carboniferous Period 12oC Over the last 600 million years, only the later Carboniferous Period and the present age (the Quaternary Period) have had CO2 levels less than 400 ppm. This means that the temperature of the Earth today is considerably cooler than for most of geological history. 359 mya 300 mya
  8. 8. The Role of Carbon Dioxide • Levels of CO2 are currently increasing • CO2 levels have risen from 280 ppm in 1850 to 380 ppm today • It is widely accepted that this is due to anthropogenic activity although natural factors may also influence it
  9. 9. The Role of Carbon Dioxide • Factors affecting CO2 concentration: – Industrialisation and burning of fossil fuels – Deforestation (particularly rainforest) – Volcanic activity – Sunspot activity Anthropogenic factors Non-anthropogenic factors Do you think there is a correlation between the increasing output of carbon dioxide due to anthropogenic activity and increasing global temperatures? Can we be certain that the first is responsible for the second?
  10. 10. Anthropogenic Factors • Burning of fossil fuels – Coal, oil and natural gas • Deforestation – Breakdown of organic matter in biomass and soil – Burning of biomass – Reduction in photosynthesis • Cattle ranching – Cow farts • Rice farming in padi fields – Anoxic conditions allow growth of methanogens • Use of fertilisers – Breakdown of nitrogen-rich compounds CO2 CH4 N2O
  11. 11. Global Greenhouse Gas Emissions in 2000 other gases carbon dioxide methane nitrous oxide 9% 1% Anthropogenic Factors 74% 16%
  12. 12. Sources of Carbon Dioxide Emissions oil and petroleum coal deforestation natural gas other sources 25% 3% Anthropogenic Factors 26% 31% 15% The proportions vary from country to country depending on its economy and energy demands
  13. 13. The Effects of Global Warming Feature Effect Environmental Effects Ice and snow Retreat of polar icecaps and glaciers Coastline Increase in sea level and coastal flooding Water cycle Increased flooding Ecosystems Change in biome and species distribution Societal Effects Water resources Severe water shortages (conflict) Agriculture Shifts from drought affected areas Coastal settlements Shifts due to storms and flooding Human health Increased outbreaks of disease The Effects of Global Warming
  14. 14. The Effects of Global Warming • Biome shifts – Models suggest biomes will shift north/south from the equator and vertically to higher ground. – Low-lying biomes such as mangroves may be lost completely • Species changes – Climate change in the past has been slow and allowed animals and plants to adapt – There may be migrations, but many obstacles (some anthropogenic) and lack of suitable habitats may lead to mass extinctions – Increased temperature may lead to spread of pests and tropical disease vectors
  15. 15. The Effects of Global Warming • Weather – Effects on weather patterns and rainfall are unpredictable – Storms are expected to increase in intensity • Agriculture – Increasing drought events would reduce crop yield and affect farmers’ ability to irrigate (especially in LEDCs) – Suitable areas for crop growth would be expected to move north/south from the equator – Farmers may be forced to change the crops they cultivate
  16. 16. The Effects of Global Warming • Tourism – Summer seasons may be extended – New coastal resorts may develop – Lack of water resources may be a problem in some – Winter sports may be curtailed and resorts closed • Social Issues – Conflicts over resources (especially water) may be expected to increase – Economic changes may occur – LEDCs will be less able to cope than MEDCs – Low lying areas (especially in LEDCs – with poor infrastructure) will be prone to coastal flooding
  17. 17. Possible Positive Feedback Mechanisms 1. Melting of polar ice may result in less white areas on the Earth’s surface – This may lower the Earth’s albedo, the amount of incoming radiation reflected into space – This may lead to further temperature rises
  18. 18. Possible Positive Feedback Mechanisms 2. The melting of permafrost in taiga and tundra biomes may release methane from rotting vegetation which is currently trapped
  19. 19. Possible Positive Feedback Mechanisms 3. Increased temperature may increase decomposition rates therefore releasing more CO2 into the atmosphere 4. Deforestation may lead to warming and drying of the climate, leading to further loss of rainforest 5. Increased forestation in higher latitudes may further decrease albedo
  20. 20. Possible Negative Feedback Mechanisms 1. Increased evaporation in equatorial latitudes may lead to more water being carried through the Ferrel and Polar Cells, leading to increased snowfall at the poles and restore the Earth’s albedo 2. Increased levels of CO2 may lead to increased rates of photosynthesis, which in turn would lower the concentration of atmospheric carbon
  21. 21. Possible Negative Feedback Mechanisms 1. Increased evaporation in equatorial latitudes may lead to more water being carried through the Ferrel and Polar Cells, leading to increased snowfall at the poles and restore the Earth’s albedo 2. Increased levels of CO2 may lead to increased rates of photosynthesis, which in turn would lower the concentration of atmospheric carbon
  22. 22. Pollution Management Strategies to Reduce Global Warming (Policy) • Control the release of greenhouse gases • Reduce the rate of deforestation • Increase tree planting programmes • Develop renewable energy resources • Reduce car use and improve public transport • Set national limits on carbon emissions • Use carbon credits and carbon trading to offset CO2 emissions • Develop methods to sequester carbon from the atmosphere (biological and chemical)
  23. 23. Pollution Management Strategies to Reduce Global Warming (Individuals) • Grow your own food • Buy locally grown produce • Use energy efficient products (e.g. light bulbs) • Reduce heating your house/ improve insulation • Use less electricity and unplug appliances • Turn off lights when not in use • Reduce use of air conditioning and refrigerants • Don’t waste water (take showers instead of baths) • Walk and use a bike/ use cars less/ use public transport • Use biofuels • Eat less meat • Get involved in public education/ activism
  24. 24. The Kyoto Protocol • In 1997, 183 countries signed this agreement to try to keep global greenhouse gases at a stable level • It came into force in 2005 • Each country’s emissions were divided into credits and they were allowed to buy and sell them • Countries are also able to offset their emissions by planting trees (an alternative to buying carbon credits) • The US and Australia signed but refused to ratify the Kyoto Protocol • Canada signed and ratified it, but has since withdrawn from its obligations
  25. 25. The Future of the Kyoto Protocol • The original agreement was due to end in 2012 • Representatives of the signatories met in December 2012 to discuss its future • It was extended until 2020. Richer nations agreed in principle to compensate poorer nations
  26. 26. The Problems of Debating the Issue • It is a problem on a global scale • It includes natural and anthropogenic factors • The mechanisms (including feedback) are not well understood • The processes are occurring over the long term and the impacts may not have occurred yet • Many people involved on both sides are affected by vested interests (consciously and unconsciously) • Much of the evidence and forward-planning is based on climate models which have considerable inherent uncertainty • Actions are likely to have huge cost implications for a large proportion of the human population • A huge amount on information is now available to everybody (scientists and non-scientists) and much of it is misleading
  27. 27. The Main Players • Al Gore – Former US vice president and presidential candidate – Winner of the 2007 Nobel Peace Prize – Writer of the book and film An Inconvenient Truth h?v=splKGWuErnM
  28. 28. The Main Players • Bjorn Lomborg – Danish economist – Writer of the book and film The Sceptical Environmentalist: Measuring the Real State of the World – Accepts that human activity may be affecting climate but refutes suggestions that this should be something that affects the global economy – Opposes the Kyoto Protocol and the idea of carbon tax watch?v=Dtbn9zBfJSs
  29. 29. The Main Players • Martin Durkin – UK film-maker – Maker of the documentary The Global Warming Swindle – Vehemently opposes the idea that climate change is anthropogenic – States a belief that temperature affects CO2 concentrations rather than the reverse watch?v=lIjGynF4qkE 2014/05/the-great-global- warming-swindle.html
  30. 30. The Main Players • Sir Nicholas Stern – Former vice-president of the World Bank and current president of the British Academy – Author of The Stern Review on the Economics of Climate Change for the British government – Believes that anthropogenic climate change poses a series threat to global economic stability and that the precautionary principle is warranted – Believes that carbon taxation and international agreements are a sensible way to approach the problem watch?v=pqLROIKWM2s
  31. 31. Questions 1. What are the main greenhouse gases? 2. What role do they play in maintaining global temperature? 3. Describe 4 different ways in which human activities affect the concentration of greenhouse gases in the atmosphere 4. Describe and evaluate strategies to reduce global warming 5. Evaluate 4 different perceptions of the issue of global warming