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The
greenhouse effect of Venus
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From
geometry, we can calculate the average solar flux
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over the
surface of Venus. It is
approximately 661 W/m2.
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Venus is very
reflective of sunshine. In fact, it
has a
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reflectivity
(or albedo) of 0.8, so the planet absorbs
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approximately
661 X 0.2 = 132 W/m2.
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By assuming
that the incoming radiation equals the
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outgoing
radiation (energy balance), we can convert this
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into an
effective radiating temperature by invoking the
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Stefan-Boltzmann
law (total energy = σ T4).
We find that
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T=220K.
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But Venus’
surface has a temperature of 730K!!!
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The
explanation for this huge discrepancy is the planet’s
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greenhouse
effect.
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