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Class #11: Wednesday July 21 Earth’s changing climate

Class #11: Wednesday July 21 Earth’s changing climate. Chapter 16. The earth's changing climate. Chapter 16. Reconstructing Past Climates. Techniques Glacial landscapes CLIMAP Ice cores Otoliths Dendrochronology Climate Throughout the Ages Earth 8-15ºC warmer than it is today

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Class #11: Wednesday July 21 Earth’s changing climate

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  1. Class #11: Wednesday July 21Earth’s changing climate Chapter 16 Class #11 Wednesday, July 21

  2. The earth's changing climate Chapter 16 Class #11 Wednesday, July 21

  3. Reconstructing Past Climates • Techniques • Glacial landscapes • CLIMAP • Ice cores • Otoliths • Dendrochronology • Climate Throughout the Ages • Earth 8-15ºC warmer than it is today • Ice Age/Interglacials • Younger-Dryas, mid-Holocene maximum Class #11 Wednesday, July 21

  4. Class #11 Wednesday, July 21 Fig. 16-CO, p. 438

  5. Class #11 Wednesday, July 21 Fig. 16-1, p. 440

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  10. Reconstructing Past Climate • Climate During the past 100 years • Little Ice Age • Modern warming • Topic: Ocean Conveyor and Climate Change • Cold, salty water sinks near Greenland driving warm water north . • If the conveyor stops much colder over Europe. Class #11 Wednesday, July 21

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  12. Class #11 Wednesday, July 21 Fig. 1, p. 444

  13. Stepped Art Class #11 Wednesday, July 21 Fig. 1, p. 444

  14. Class #11 Wednesday, July 21 Fig. 16-6, p. 445

  15. Reconstructing Past Climate • Temperature Trend During the Past 100+ Years • Largest increase in temperature of any century during the past 1000 years • 0.6ºC is significant when compared to the last 1000 years • Scientists point to carbon dioxide and greenhouse gases as the cause Class #11 Wednesday, July 21

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  17. Possible Causes of Climate Change • External Causes • Change in incoming radiation • Change in composition of the atmosphere • Change in Earth’s surface • Feedback Mechanisms • Water vapor-greenhouse gas feedback (+) • Snow-albedo feedback (+) • Infrared radiation (-) Class #11 Wednesday, July 21

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  19. Possible Causes of Climate Change • Plate Tectonics and Mountain Building • Theory of plate tectonics • Ridge and subduction • Mountain interaction with airflow and ocean currents • Variation on the Earth’s Orbit • Milankovitch Theory • Eccentricity • Precession • Obliquity Class #11 Wednesday, July 21

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  25. Possible Causes of Climate Change • Atmospheric Particles • Aerosols = natural + anthropogenic • Aerosols in the troposphere (sulfate) may cause cooling die to reflection of radiation • Topic :Nuclear winter • Explosions cause debris to rise and circulate absorbing sunlight creating darkness and cold. • Volcanic Explosions: ash and dust in the stratosphere reflect light and cool Class #11 Wednesday, July 21

  26. Class #11 Wednesday, July 21 Fig. 16-14, p. 451

  27. Class #11 Wednesday, July 21 Fig. 16-15, p. 453

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  30. Possible Causes of Climate Change • Variations in Solar Output • Sunspots cause more radiation to be generated by the sun • Maunder minimum • Topic: Climate Models • General circulation models (GCMs) are not perfect but extremely sophisticated and serves as the most reliable current predictive tool. Class #11 Wednesday, July 21

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  32. Global Warming • Recent Global Warming: Perspective • Since the beginning of the 20th century average global surface temperature has increase 0.8ºC • Radiative Forcing Agents • Carbon dioxide and other greenhouse gases disrupt radiative equilibrium, forming an increase in temperature Class #11 Wednesday, July 21

  33. Global Warming • Advanced Topics: • Radiative Forcing • Any change in average net radiation that occurs at the top of the atmosphere which is due to some change in the climate system is called radiative forcing. • Climate Models and Recent Temperature • It is difficult to unequivocally prove greenhouse forcing due to the noise in the system. • Model well sulfate aerosols, greenhouse gases, change in solar radiation Class #11 Wednesday, July 21

  34. Class #11 Wednesday, July 21 Fig. 16-19, p. 457

  35. Class #11 Wednesday, July 21 Fig. 2, p. 458

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  37. Global Warming • Future Global Warming: Projections • Double carbon dioxide levels will cause a surface warming of 2-4.5ºC • Uncertainties: • The effect of water and land on rising levels of carbon dioxide • Amount or greenhouse gases • Question of Clouds • Clouds reflect radiation and emit infrared radiation, positive and negative feedbacks. Class #11 Wednesday, July 21

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  39. Global Warming • Consequences of Global Warming • Land areas warm faster • Rise in sea level • Fertilize plants • Land Use Change • Desertification • Plagues and climate Class #11 Wednesday, July 21

  40. Class #11 Wednesday, July 21 Table 16-1, p. 460

  41. Class #11 Wednesday, July 21 Fig. 16-21, p. 461

  42. Class #11 Wednesday, July 21 Fig. 16-21a, p. 461

  43. Class #11 Wednesday, July 21 Fig. 16-21c, p. 461

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  48. Global Warming • Topic: The Sahel • Recent studies suggest that the dry periods were due to a cooler North Atlantic Ocean and aerosols from North America may exacerbate desertification • Efforts to Curb • Kyoto Protocol • Target emissions, credits, sinks • US has yet to sign protocol • California implementing protocol Class #11 Wednesday, July 21

  49. Class #11 Wednesday, July 21 Fig. 3, p. 465

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