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 = σ T4).  We find that T=255K.
Earth’s surface has a temperature of 288K
While much smaller than Venus’ greenhouse effect, earth’s is crucial for the planet’s habitability.  Without the greenhouse effect, the temperature today in Los Angeles would be about 0 degrees Fahrenheit.