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

2. The earth's changing climate Chapter 16 2Class #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 3Class #11 Wednesday, July 21

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

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

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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. 10Class #11 Wednesday, July 21

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

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

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

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 15Class #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 (-) 17Class #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 19Class #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 25Class #11 Wednesday, July 21

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

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

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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. 30Class #11 Wednesday, July 21

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32. Global Warming Recent Global Warming: Perspective – Since the beginning of the 20 th 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 32Class #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 33Class #11 Wednesday, July 21

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

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

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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. 37Class #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 39Class #11 Wednesday, July 21

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

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

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

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

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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 48Class #11 Wednesday, July 21

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