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
<σ Ts4 >

4. Greenhouse Effect (Energy)
4 -2
G = <σ Ts > - FTOA Wm
Greenhouse Efficiency
4
g = <σ Ts >/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,φ)
 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. G re e nho us e E ffe ct
2.0
1.8
1.6
1.4
1.2
1.0
Neop rot C retaceous Eocene LGM Holocene Present
Time Period

12. Obs. Collins(2003)

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

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

15. Mars
<σ Ts4> = 133 Wm-2
S = S0(1-αp)/4 = F= 123 Wm-2
G = 10 Wm-2
g = 1.1

16. Whither the Future?

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