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Evolution of Earth’s Greenhouse Effect

Evolution of Earth’s Greenhouse Effect. Jeffrey T. Kiehl National Center for Atmospheric Research. Outline. What is the Greenhouse Effect? Forcings over Geologic Time Sources to Estimate Greenhouse Effect Evolution of Greenhouse Effect Comparison to Neighboring Planets

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Evolution of Earth’s Greenhouse Effect

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  1. Evolution of Earth’s Greenhouse Effect Jeffrey T. Kiehl National Center for Atmospheric Research

  2. Outline • What is the Greenhouse Effect? • Forcings over Geologic Time • Sources to Estimate Greenhouse Effect • Evolution of Greenhouse Effect • Comparison to Neighboring Planets • Whither the Greenhouse Effect?

  3. Greenhouse Effect FTOA <s Ts4 >

  4. Greenhouse Effect (Energy) G = <s Ts4> - FTOA Wm-2 Greenhouse Efficiency g = <s Ts4>/FTOA

  5. Greenhouse Effect: G or g • Convolves a number of relevant climatic variables: • Temperature • Water Vapor • Clouds • Trace Gases {CO2, CH4, …}

  6. Forcings over Geologic Time • Solar Insolation • Luminosity • Interplanetary Dust? • Milankovitch S(t,) • Atmospheric Composition • Carbon Dioxide & Methane • Volcanic Aerosols • Paleogeography • Orography • Positions of Continents • Ocean Basins • Ocean Bathymetry

  7. Sources of Greenhouse Effect • Neoproterozoic (~600 MYA) • Pavlov and Kiehl, Chandler & Sohl • Cretaceous (~70 MYA) • Otto-Bliesner et al. • Eocene (~55 MYA) • Huber and Sloan • Last Glacial Maximum (~18,000 y b.p.) • Otto-Bliesner et al. • Holocene (~3,500 y b.p.) • Otto-Bliesner et al. • Modern (1870-2000) • Ammann et al.

  8. Obs. Collins(2003)

  9. Venus <s Ts4> = 17,002 Wm-2 S = S0(1-ap)/4 = F= 185 Wm-2 G = 16,817 Wm-2 g = 92

  10. Earth <s Ts4> = 402 Wm-2 F = 239 Wm-2 G = 163 Wm-2 g = 1.7

  11. Mars <s Ts4> = 133 Wm-2 S = S0(1-ap)/4 = F= 123 Wm-2 G = 10 Wm-2 g = 1.1

  12. Whither the Future?

  13. FALL 2003 AGU SESSION on Evolution of Earth’s Greenhouse

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