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The
greenhouse effect of Earth
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From
geometry, we can calculate the average solar flux over
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the surface
of Earth. It is approximately 343 W/m2.
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The earth
has a much lower albedo than Venus (0.3), so the
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planet
absorbs approximately 343 X 0.7 = 240 W/m2.
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By assuming
that the incoming radiation equals the outgoing
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radiation, we
can convert this into an effective radiating
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temperature
by invoking the Stefan-Boltzmann law (total
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energy = σ T4). We find that T=255K.
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Earth’s
surface has a temperature of 288K
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While much
smaller than Venus’ greenhouse effect, earth’s
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is crucial
for the planet’s habitability.
Without the
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greenhouse
effect, the temperature today in Los Angeles
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would be
about 0 degrees Fahrenheit.
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