2. Protons for Breakfast Week 4: Global Warming

3. In the event of an alarm sounding…

4. What we know so far… Atoms Electricity Week 1 Electromagnetic waves Week 2 Heat Week 3

5. Global Warming Can we collect your facts please…

6. Global Warming The problem with this problem…

7. This evening… Do you have any personal evidence that the climate is changing?

8. Powers of Ten (time) Time scale in seconds Very Very short Very Very Long 10 0 10 3 10 6 10 9 10 12 10 15 10 -3 10 -6 10 18 10 24 10 21 10 -15 10 -9 10 -18 10 -12 Time for a molecule to jiggle once Light wave wiggles once Earth moves once around the Sun Age of the Earth End of last ice age Lifetime of a Civilisation A human lifetime 1 second

9. This evening… Why is the Earth the temperature it is? The Earth’s Atmosphere Carbon dioxide Why are scientists concerned? What’s going to happen? What should we do? –We’d like you to do this!

10. The Simple Story What determines the surface temperature of the Earth? Energy Balance

11. A Question? How hot does an object get hot when placed in front of a fire?

12. What determines the surface temperature of the Earth? Simple Story (1) Light from the Sun heats the Earth… The Sun Earth 6400 °C

13. What determines the surface temperature of the Earth? Simple Story (2) Drawn to Scale… The Sun Earth (drawn 100 times too big) (drawn to scale)

14. What determines the surface temperature of the Earth? Simple Story (3) Light from the Sun heats the Earth… The Earth then radiates heat away… Light from the Sun Earth

15. What determines the surface temperature of the Earth? Simple Story (4) 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

16. What determines the surface temperature of the Earth? The Energy Balance of the Earth

17. Earth Warms Earth Cools What determines the surface temperature of the Earth? The Numbers World Energy Production heat input from the Sun heat lost from the Earth CO2 emissions

18. What determines the surface temperature of the Earth? Some more details…

19. What determines the surface temperature of the Earth? More detail (1) We need to know: How much light reaches the Earth? How much light reaches the Earth’s Surface? How much energy is radiated from the Earth’s Surface?

20. What determines the surface temperature of the Earth? How much light reaches the Earth? Light from the Sun heats the Earth… Earth At the top of the atmosphere Above the Equator At midday About 1360 W/m 2

21. What determines the surface temperature of the Earth? How much light reaches the Earth? Light from the Sun heats the Earth… Earth North Pole South Pole Equator 1360 W/m 2 680 Whole Earth Average 340 W/m 2

22. What determines the surface temperature of the Earth? More detail (1) Light reflected from Earth Average Value 100 watts per square metre Light from the Sun Average Value 340 watts per square metre

23. What determines the surface temperature of the Earth? Hold on a moment! What about all the heat rising up from the Earth’s hot centre?

24. 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

25. What determines the surface temperature of the Earth? 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!

26. 1. What determines the surface temperature of the Earth? More detail (2) Infra Red Radiation cools the Earth… Light from the Sun heats the Earth…

27. 1. What determines the surface temperature of the Earth? More detail (2) Light from the Sun heats the Earth… Average Value 240 watts per square metre Average Value 240 watts per square metre

28. 1. What determines the surface temperature of the Earth? More detail (2) How hot must the Earth be to radiate 240 W/m 2 ? Average Value 240 watts per square metre -18 °C

29. 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

30. A Question and an Answer 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

31. 1. What determines the surface temperature of the Earth? More detail (4) -18 °C Average Surface Temperature 33 °C Temperature for radiation balance +15 °C Greenhouse Effect

32. What determines the surface temperature of the Earth? The Earth’s surface is 33 °C warmer than it would be if had no atmosphere

33. The Atmosphere Earth’s Atmosphere the Greenhouse Effect

34. The Atmosphere More detail (5) What is the composition of the atmosphere? Gas% Nitrogen (N 2 )78.1 Oxygen (O 2 )20.1 Argon (Ar)0.93 Water (H 2 O)0.1 to 1 Carbon Dioxide (CO 2 )0.035

35. Illustration of atmospheric composition More detail (6) About 100 molecules O2O2 Ar N2N2

36. Illustration of atmospheric composition More detail (7) About 1200 molecules Water(H 2 O)

37. Illustration of atmospheric composition More detail (8) About 10000 molecules Carbon dioxide (CO 2 )

38. The Atmosphere More detail (9) Nitrogen (N 2 ), Oxygen (O 2 ) & Argon (Ar) > 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

39. The Atmosphere More detail (10) 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

40. The Atmosphere More detail (10) Greenhouse warming is caused by Water (H 2 O) Carbon Dioxide (CO 2 )

41. The Atmosphere More detail (11) What is special about H 2 O and CO 2 ? Molecules have three atoms Natural frequencies of vibration in the infra-red They make the atmosphere opaque to certain infra-red frequencies

42. The Atmosphere More detail (12) Absorbtion frequencies determined by exact frequencies of molecular jiggling

43. The Atmosphere and the Greenhouse Effect The Transparency of the Atmosphere

44. Warning! Complicated diagram !

45. Infra RedUltra VioletVisible Absorption bands

46. 1. What determines the surface temperature of the Earth? More detail (2) Infra Red Radiation cools the Earth…

47. What determines the surface temperature of the Earth? More detail (16) In balance at + 15 °C… On Average 240 W/m 2 On Average 390 W/m 2 150 W/m 2 sent back to Earth Average Value 240 W/m 2

48. What determines the surface temperature of the Earth? More detail (4) Greenhouse Warming 33 °C Others <1 °C CO 2 2 °C H 2 O 31 °C Nothing so far is the subject of any dispute –Although not all the numbers are exact

49. Greenhouse Effect So the Earth’s surface is warmed by the Greenhouse Effect Caused by water and carbon dioxide Turns the Earth from a ‘snowball’ with a hot Equator into the relatively temperate place So what’s the problem?

50. Carbon dioxide & the carbon cycle The amount of carbon dioxide in the Earth’s atmosphere is increasing…

51. Atmospheric CO 2 Concentration versus year Historical Value 280 ppm Current value 370 ppm parts per million

52. Atmospheric CO 2 Concentration versus year (Detail 2)

53. Atmospheric CO 2 Concentration (Detail 3) Concentration in 19 th century Carbon dioxide (CO 2 ) Added in 20 th Century

54. Carbon dioxide The amount of carbon dioxide in the Earth’s atmosphere is increasing… Historically280 ppm 1950310 ppm 2000365 ppm 2025about 425 ppm 2050450-550 ppm

55. Carbon dioxide Why is the amount of carbon dioxide in the Earth’s atmosphere is increasing? We are digging up geological deposits of carbon –Coal & Oil & Gas We are burning them! C+ O 2 →CO 2

56. Michael’s family CO 2 emissions 0.2 kg per mile 4000 miles per year 800 kg CO 2 /year 0.3 kg per mile per person 1000 miles per year 600 kg CO 2 /year 0.5 kg per kWh 7300 kWh per year 3650 kg CO 2 /year Holiday in California! 56000 person miles! 16,000 kg CO 2 /year 0.2 kg per kWh 17000 kWh per year 3400 kg CO 2 /year

57. My family’s CO 2 emissions 8500 kg of CO 2 per year at home 16000 kg For our holiday in California! 24.5 tonnes!! There are many families like Michael’s…

58. Global CO 2 Emissions 30 billion tonnes CO 2 8 billion tonnes C EVERY YEAR

59. Question Is 8 billion tonnes of carbon per year (emitted as CO 2 ) a lot or a little?

60. Carbon Cycle (Amounts of carbon in billions of tons) 760 90 6.4 2,000 39,000 500 1,000 3,000 300 1.4 1.7 760 increasing at 3.2/year 60

61. Remember this picture? Greenhouse Warming 33 °C Others <1 °C CO 2 2 °C H 2 O 31 °C If H 2 O is a more important greenhouse gas than CO 2, why aren’t we worried about water vapour emissions? A Question

62. Answer Residence time Excess H 2 O in the atmosphere causes rain within a few days Excess CO 2 in the atmosphere takes a few hundred years to remove Photo Credit http://www.cepolina.com

63. Cause for Concern? What is the effect of increased levels of carbon dioxide in the Earth’s atmosphere? Nobody knows

64. Climate Models What is the current effect of CO 2 A net extra ‘forcing’ of around 2 watts per square metre… Average 240 W/m 2 On Average 390 W/m 2 150 W/m 2 Average 240 W/m 2 + 2 W/m 2

65. An additional 2 watts per square metre of ‘radiative forcing’ Scientific American March 2004

66. Cause for Concern? Should we be concerned?

67. Cause for Concern? Scientists are concerned for several reasons: 1.Pre-historic studies show a correlation between atmospheric CO 2 levels and global climate 2.There are observed changes in climate

68. Cause for Concern? Prehistoric Studies 1 year of snow From approximately 16,250 years ago

69. Pre-Historic studies Bubbles in Arctic and Antarctic Ice Minimum Value 180 ppm Maximum Value 300 ppm Ice Ages

70. Milankovitch Cycles What caused the ice ages? Small changes in the orbit of Earth around the Sun Milankovitch Cycles

71. Daily Rotation Northern Hemisphere Summer Northern Hemisphere Spring Equinox Northern Hemisphere Winter Northern Hemisphere Autumn Equinox Angle varies from 22.5º to 24.5º And back again every 40,000 years 23.5º tilt Earth Spins 365.25 times on its journey around the Sun

72. Atmospheric CO 2 Concentration versus year variation in the last 400,000 years Current value 380 ppm

73. Cause for Concern? Observed Changes in Climate

74. Observed Changes Average surface temperature is difficult to measure

75. Observed changes It is difficult to detect small changes in a long series of data?

76. My Weight 2008-2009

77. Observed changes Best estimates http://www.cru.uea.ac.uk/cru/climon/data/themi/g17.dat But its not just average temperature that matters

78. Other observations Germany

79. Other observations Muir Glacier, Alaska Photo credit: Global Warming Art

80. Other observations Argentina

81. Causes for concern Pre-historic climate studies Observed changes

82. 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 likely2007: It is very likely

83. Climate Models Predictions Try to ‘add up’ the many factors affecting climate? Climate Models help us estimate… ‘What’s going to happen?”

84. Cause for Concern? Climate models What do we mean by Climate?

85. Climate Models What is a computer model of the climate? © Australian Bureau of Meteorology

86. Climate Models What is the output of a climate model?

87. The Future… CO 2 levels will continue to rise. If we make a 50% cut in global emissions –Requires a much greater cut (80% ?) by the UK Then CO 2 will stabilise at twice historical levels

88. IPCC Predictions… Human CO 2 emissions

89. IPCC Predictions… Atmospheric CO 2 concentration

90. 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

91. IPCC Predictions… Climate Research Unit East Anglia University 2008 0.5 metres in 100 years ? 1 metre

92. IPCC Predictions… 1 metre in 100 years http://en.wikipedia.org/wiki/Sea_level_rise

93. What could we do? What should we do? Nothing –Spend money on coping with consequences We could reduce the amount of CO 2 we emit –Even though this involves saving energy, this still costs money –Things we do now will cost us money now Is global warming our top priority? –Global poverty? AIDS? –Hospitals? Education? Would you vote to increase the price of all fuels?

94. So… What do YOU think we should do?

95. Despair? You may never know what results come of your action, but if you do nothing, there will be no result. Mahatma Ghandi

96. See you next week to discuss… Mobile Phone Safety! Goodnight

97. Unused Slides

98. Contributions to Climate Forcing Greenhouse gases Carbon Dioxide Methane Chlorofluorocarbons Nitrous Oxide Ozone Aerosols Black Carbon Reflective aerosols Cloud droplet changes Land cover changes Sun Climate Forcing (W/m 2 ) 0+1

99. Feedback Global Temperature More Evaporation Climate Forcing Increased Climate Forcing Increased Water Vapour Increased Cloud Cover Decreased Climate Forcing Negative Positive

100. Powers of Ten (Global Warming) Length scale in metres Very Very Small Very Very Large 10 0 10 3 10 6 10 9 10 12 10 15 10 -3 10 -6 10 18 10 24 10 30 10 36 10 21 10 27 10 33 10 -15 10 -9 10 -18 10 -12 Human Relationships Diameter of the Earth Distance to the Sun Tallest Mountain Deepest Trench Atoms & Molecules Microbes The phenomenon of global warming involves physical processes with length scales spanning 20 powers of 10!

101. The spectrum of sunlight

102. Pre-Historic studies Milankovitch Cycles

103. Greenhouse gases (2.5 Wm -2 ) Emitted IR radiation Natural greenhouse heating Input solar radiation (100 %) Reflected by clouds, atmosphere (~23%) Reflected from surface (~8%) Absorbed by ground (~49%) Measured absorption (25%) ~80 Wm -2 ?? Absorbed by atmosphere (20%) ~60 Wm -2 Climate Models

104. Global CO 2 Emissions ?

105. UK CO 2 Emissions