The greenhouse effect of Earth
From geometry, we
can calculate the average solar flux over the surface of
Earth. It is approximately 343 W/m2.
The earth has a
much lower albedo than Venus (0.3), so the planet absorbs
approximately 343 X 0.7 = 240
W/m2.
By assuming that
the incoming radiation equals the outgoing radiation, we can
convert this into an effective radiating temperature by
invoking the Stefan-Boltzmann law (total energy = sT4).
We find that T=255K.
EarthÕs
surface has a temperature of 288K
While much smaller
than VenusÕ greenhouse effect, earthÕs is crucial for the
planetÕs habitability. Without the
greenhouse effect,
the temperature today in Los Angeles would be about 0
degrees Fahrenheit.