Why is Earth habitable and Venus an oven? Balance the sunlight a planet absorbs against the heat it radiates and the greenhouse effect falls out of the numbers.
Planetary Energy BalanceLive
greenhouse effect · equilibrium temperature
Equilibrium surface temperature
13.7°C
286.9 K
Controls
Presets
A planet warms until it radiates away exactly the sunlight it absorbs. Balancing absorbed power S(1−α)/4 against εσT⁴ gives the equilibrium temperature. An emissivity below 1 represents greenhouse gases trapping outgoing infrared, raising the surface temperature.
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How it works
A planet reaches equilibrium when absorbed solar power, S(1−α)/4, equals its thermal emission εσT⁴. Solving for T gives the equilibrium temperature. Lowering the effective emissivity models greenhouse gases trapping outgoing infrared — the difference between Earth's −18 °C bare-rock value and its habitable surface.
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