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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

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

Chapter 16

Class #11 Wednesday, July 21

the earth s changing climate

The earth\'s changing climate

Chapter 16

Class #11 Wednesday, July 21

reconstructing past climates
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

reconstructing past climate
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

slide13

Stepped Art

Class #11 Wednesday, July 21

Fig. 1, p. 444

reconstructing past climate1
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

possible causes of climate change
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

possible causes of climate change1
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

possible causes of climate change2
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

possible causes of climate change3
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

global warming
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

global warming1
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

global warming2
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

global warming3
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

slide42
Class #11 Wednesday, July 21

Fig. 16-21a, p. 461

slide43
Class #11 Wednesday, July 21

Fig. 16-21c, p. 461

global warming4
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

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