The major reason for this difference is the Greenhouse Effect in the atmosphere. The calculation for the temperature of Mars, with very little atmosphere, is in very good agreement with the observed temperature . On Europa gravitational tidal forces cause the interior to be warm enough that it appears that there may be liquid water beneath its ice crust. The greenhouse effect is a due to absorption and re-emission of infrared radiation by the earth's atmosphere. As discussed earlier, the earth receives visible light from the sun and emits heat in the form of infrared radiation.
Visible light passes into the greenhouse and is absorbed by material inside.
Human activities are causing changes in the concentrations of these gases, which may lead to increased greenhouse effects. In the steady state, the incoming radiation must balance the outgoing radiation. Calculate T in Centigrade with the addition of the greenhouse effect. Try changing the albedo to 0.31 or 0.33, or changing the multiplier for the solar constant to about 0.99 or 0.95. However, if all of the factors in Equation 2 remained the same, the yearly average temperature would be the same.