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.