Global warming

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Global warming

  1. 1. Protons for Breakfast Global Warming Week 4 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 1800 1850 1900 1950 2000
  2. 2. In the event of…In the event of an attack of mutant bananas…
  3. 3. Global Warming Can we collect your facts please…
  4. 4. What do we mean by Climate? What is the Climate? It’s the average weather in a particular area What is the Climate? It’s the average weather Over a period a time (30 years usually) Averages of temperatures and rain occurrence Calculated scientifically Things like that determine what we call the Climate Determine what the climate of a place will be.
  5. 5. One problem… Do you have any personal evidence that the global climate is changing?
  6. 6. This Evening… 1. Why is the Earth’s surface the temperature it is? 2. The Earth’s Atmosphere 3. Increasing Carbon Dioxide 4. Should we be concerned? 5. What’s going to happen? 6. What should we do?
  7. 7. Energy Balance
  8. 8. How hot does an object get when placed in front of a fire?
  9. 9. Light from the Sun heats the Earth… The Sun Earth 5400 °C
  10. 10. Light from the Sun heats the Earth… Drawn to Scale… The Sun Earth (drawn 100 times too big) (drawn to scale)
  11. 11. Light from the Sun heats the Earth… The Earth then radiates heat away… Light from the Sun Earth
  12. 12. Energy Balance heat input from the Sun heat lost from the Earth by radiation When there is balance, the Earth’s average temperature will be stable Earth Warms Earth Cools
  13. 13. The Energy Balance of the Earth
  14. 14. Earth Warms Earth Cools Energy Balance: to scale World Energy Production heat input from the Sun heat lost from the Earth
  15. 15. Some more details…
  16. 16. How much light reaches the Earth? Earth •At the top of the atmosphere •Above the Equator •At midday •About 1360 W/m2
  17. 17. How much light reaches the Earth? Earth North Pole South Pole Equator 1360 W/m2 680 Whole Earth Average 340 W/m2
  18. 18. How much light reaches the Earth’s Surface Light reflected from Earth Average Value 100 watts per square metre Light from the Sun Average Value 340 watts per square metre
  19. 19. Hold on a moment! What about all the heat rising up from the Earth’s hot centre?
  20. 20. Earth 6400 km radius 5500 °C Heat flow is less than 0.1 Watt per square metre Temperature increases by ~20 °C for each kilometre below the Earth’s surface Heat flow to and from surface from the Sun 240 Watt per Square metre
  21. 21. A remarkable fact… Heat flow from the centre of the Earth can be completely ignored when considering what determines the surface temperature of the Earth!
  22. 22. What determines the surface temperature of the Earth? Infra Red Radiation cools the Earth… Light from the Sun heats the Earth…
  23. 23. Radiation Balance Light from the Sun heats the Earth… Average Value 240 watts per square metre Average Value 240 watts per square metre
  24. 24. Radiation Balance How hot must the Earth be to radiate 240 W/m2 ? Average Value 240 watts per square metre -18 °C
  25. 25. A Question What is the average temperature of the Earth? 1 metre above the surface and averaged over: • day and night, • all latitudes and longitudes. • all seasons (a) – 15 ° C (b) – 5 ° C (c) + 5 ° C (d) + 15 °C
  26. 26. Summary -18 °C Average Surface Temperature 33 °CTemperature for radiation balance +15 °C Greenhouse Effect
  27. 27. The Earth’s surface is 33 °C warmer than it would be if had no atmosphere
  28. 28. This Evening… 1. Why is the Earth’s surface the temperature it is? 2. The Earth’s Atmosphere 3. Increasing Carbon Dioxide 4. Should we be concerned? 5. What’s going to happen? 6. What should we do?
  29. 29. The composition of the atmosphere? Gas % Nitrogen (N2) 78.1 Oxygen (O2) 20.1 Argon (Ar) 0.93 Water (H2O) 0.1 to 1 Carbon Dioxide (CO2) 0.035
  30. 30. Illustration of atmospheric composition About 100 molecules O2 Ar N2
  31. 31. Illustration of atmospheric composition About 1200 molecules Water(H2O)
  32. 32. Illustration of atmospheric composition About 10000 molecules Carbon dioxide (CO2)
  33. 33. Nitrogen (N2), Oxygen (O2) & Argon (Ar) Suppose the atmosphere contained no carbon dioxide or water • N2, O2 and Ar is more than 99% of the atmosphere • Molecules have one or two atoms • Natural frequency of vibration in the ultra-violet • Make atmosphere opaque to ultra-violet light • Transparent to infra-red and visible radiation
  34. 34. Nitrogen (N2), Oxygen (O2) & Argon (Ar) With an atmosphere of only Nitrogen Oxygen & Argon, what would be the surface temperature? Average Value 240 watts per square metre Average Value 240 watts per square metre -18 °C
  35. 35. Greenhouse warming is caused by Water (H2O) Carbon Dioxide (CO2)
  36. 36. What is special about H2O and CO2 • Molecules have three atoms • Natural frequencies of vibration in the infra-red • They make the atmosphere opaque to certain infra- red frequencies
  37. 37. Vibrations of CO2 and H20 • Different types of molecular jiggling occur at different frequencies Water H20 Carbon dioxide C02
  38. 38. Absorption demo Frequency
  39. 39. The Transparency of the Atmosphere
  40. 40. Warning! Complicated diagram !
  41. 41. Infra RedUltra Violet Visible Absorption bands
  42. 42. Infra Red Radiation cools the Earth…
  43. 43. Radiation Balance in the 20th Century… On Average 240 W/m2 On Average 390 W/m2 150 W/m2 sent back to Earth Average Value 240 W/m2 On Average + 15 ºC
  44. 44. Greenhouse Warming 33 °C Others <1 °C CO2 2 °C H2O 31 °C If H2O is a more important greenhouse gas than CO2, why aren’t we worried about water vapour emissions?
  45. 45. Residence time Because excess H2O in the atmosphere • causes rain within a few days Excess CO2 in the atmosphere • takes a few hundred years to remove Photo Credit http://www.cepolina.com If H2O is a more important greenhouse gas than CO2, why aren’t we worried about water vapour emissions?
  46. 46. How the parts fit together Atmospheric Water Global Temperature Greenhouse Effect Evaporation Small slowly changing contribution to Greenhouse Effect Clouds Carbon Dioxide
  47. 47. Experiment Does water block infrared light?
  48. 48. A Children’s song What does the glass of a Greenhouse do? It lets the short solar rays pass through The objects in the house absorb these rays And re-radiate them as long heat rays What does the glass of a Greenhouse do? It doesn’t let the long heat rays pass through Trapped by the glass they bounce back and forth, Re-radiated and re-absorbed Stay Stay, you long heat rays, Warm up the house on cold cold days Stay Stay, you long heat rays, Warm up the house on coooooold cold days The atmosphere is like a greenhouse too It lets most of the solar rays through The surface of the Earth absorbs these rays And re-radiates them as long heat rays There’s vapour in the air, What does it do? It doesn’t let the long heat rays pass through Trapped by the vapour they bounce back and forth, Re-radiated and re-absorbed Stay Stay, you long heat rays, Warm up the house on cold cold days Stay Stay, you long heat rays, Warm up the Earth on cooooooold cold days
  49. 49. Greenhouse Effect • Earth’s surface is warmed by the Greenhouse Effect • Caused by: Water (mainly) and carbon dioxide • Turns the Earth from a ‘snowball’ with a hot Equator into the relatively temperate place So what’s the problem?
  50. 50. This Evening… 1. Why is the Earth’s surface the temperature it is? 2. The Earth’s Atmosphere 3. Increasing Carbon Dioxide 4. Should we be concerned? 5. What’s going to happen? 6. What should we do?
  51. 51. 0 50 100 150 200 250 300 350 400 1700 1750 1800 1850 1900 1950 2000 CO 2 Concentration(PPM) Year Atmospheric CO2 Concentration versus year Historical Value 280 ppm Current value ~390 ppm parts per million Click for latest value
  52. 52. Carbon dioxide Why is the amount of carbon dioxide in the Earth’s atmosphere is increasing? • We are digging up carbon as: Coal & Oil & Gas • We are burning them! C + O2 →CO2
  53. 53. Michael’s family CO2 emissions 0.2 kg per mile 4000 miles per year 800 kg CO2/year 0.3 kg per mile per person 1000 miles per year 600 kg CO2/year 0.5 kg per kWh 7300 kWh per year 3650 kg CO2/year Holiday in California! 56000 person miles! 8,000 kg CO2/year 0.2 kg per kWh 17000 kWh per year 3400 kg CO2/year
  54. 54. My family’s CO2 emissions 8500 kg of CO2 per year at home 8000 kg For our holiday in California! 16.5 tonnes!! There are many families like Michael’s…
  55. 55. Carbon? Or Carbon dioxide? CO2 1 tonne of CO2 0.27 tonne of C 0.73 tonne of O2
  56. 56. Global CO2 Emissions 0.0 2.0 4.0 6.0 8.0 10.0 1750 1800 1850 1900 1950 2000 0 5 10 15 20 25 30 35 BillionsofTonnesof Carbon Year BillionsofTonnesof CarbonDioxide 30 billion tonnes CO2 8 billion tonnes C EVERY YEAR
  57. 57. Question Is 8 billion tonnes of carbon per year (emitted as CO2) a lot or a little?
  58. 58. Carbon Cycle (Amounts of carbon in billions of tons) 760 908 2,000 39,000 500 1,000 3,000 (Coal) 300 (Oil &Gas) 2 2 760 increasing at 4 per year 60
  59. 59. Cause for Concern? What is the effect of increased levels of carbon dioxide in the Earth’s atmosphere? Nobody knows
  60. 60. Radiation ‘Balance’ in 2012… On Average <240 W/m2 On Average 390 W/m2 150 W/m2 sent back to Earth Average Value 240 W/m2 On Average + 15 ºC +2 W/m2 +?? ºC
  61. 61. Earth Warms Earth Cools Energy Balance: to scale heat input from the Sun heat lost from the Earth
  62. 62. This Evening… 1. Why is the Earth’s surface the temperature it is? 2. The Earth’s Atmosphere 3. Increasing Carbon Dioxide 4. Should we be concerned? 5. What’s going to happen? 6. What should we do?
  63. 63. 4. Why are scientists are concerned 1. Pre-historic studies show a strong correlation between atmospheric CO2 levels and global climate. 2. There are observed changes in climate
  64. 64. Prehistoric Studies 1 year of snow From approximately 16,250 years ago
  65. 65. 0 100 200 300 400 0200400600800 CarbonDioxide Concentration(PPM) Thousands of years before present day Bubbles in Arctic and Antarctic Ice 300 ppm Maximum 180 ppm Minimum Ice Ages 395 ppm
  66. 66. Cause for Concern? Observed Changes in Climate
  67. 67. A Question?One estimate of the Land Surface Temperature?
  68. 68. A Question? Berkeley NASA GISS Hadley CRU NOAA NCDC What has happened? What did Global Warming Theory predict in 1981? http://berkeleyearth.org But its not just average temperature that matters
  69. 69. Glaciers Muir Glacier, Alaska Photo credit: Global Warming Art Glaciers are retreating: worldwide
  70. 70. Arctic Sea Ice http://nsidc.org/arcticseaicenews/
  71. 71. Arctic Sea Ice Minima 2012 2013
  72. 72. A Question Can we be completely sure that the climate changes we observe are caused by anthropogenic emissions of carbon dioxide? Man-made and Woman-made 2001: It is likely 2007: It is very likely 2013: It is very very likely
  73. 73. This Evening… 1. Why is the Earth’s surface the temperature it is? 2. The Earth’s Atmosphere 3. Increasing Carbon Dioxide 4. Should we be concerned? 5. What’s going to happen? 6. What should we do?
  74. 74. Climate Models ‘What’s going to happen?” • Climate Models ‘add up’ the many factors Nobody knows
  75. 75. The best ‘realistic’ possibility… If we make a 50% cut in global emissions: 80% cut in the UK CO2 concentraions will rise to twice historical levels and stabilise
  76. 76. IPCC Predictions… Global Mean Temperature We stop all emissions NOW We BEGIN to stop all emissions EVENTUALLY We BEGIN to stop all emissions NOW We do nothing
  77. 77. This Evening… 1. Why is the Earth’s surface the temperature it is? 2. The Earth’s Atmosphere 3. Increasing Carbon Dioxide 4. Should we be concerned? 5. What’s going to happen? 6. What should we do?
  78. 78. What should we do… Nothing EverythingSomething
  79. 79. What could we do? What should we do? In smaller groups • Please come up with some questions, and suggestions • We will gather these together and then discuss them! You decide!
  80. 80. Despair? You may never know what results come of your action, but if you do nothing, there will be no result. Mahatma Ghandi

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