I ask this question because I do not think that in Temperature behavior over time of black or white cars in hot, sunny regions it was properly resolved. One answer is about doing calculations with spectra to determine which car gets hotter, but doesn't clarify anything, another one says that color is not important and the primary mechanism is greenhouse effect. But there is a big difference between a black and a white car: someone did an experiment and experienced a $\Delta T$ of near 10 degrees! So I think that the question still hasn't been answered and that's why I have posted it.
Black cars in parking get hotter than white cars during summer. What is the major effect in this phenomenon? Is it black body radiation or the greenhouse effect?
Solar radiation has a peak in the visible (550 nm) as given by Wien's law. So a white car will reflect almost totally the radiation in the visible, while the black one will absorb all the radiation in the visible and then re-irradiate it. The black paint is at a temperature near 300K, so it will emit mostly in the infrared. Because the emission is isotropic, some infrared radiation will be emitted outside the car, while some other will be emitted inside the car. Glass is opaque with respect to infrared radiation, so the infrared radiation emitted by the black paint will continue to bounce back and forth in the car without exiting. As more infrared radiation is emitted by the black paint, the car starts to get hotter until it reaches equilibrium. Next, until now we do not have considered another form of greenhouse effect which occurs both for white and black cars. Solar radiation comes into the car (glass is transparent in the visible), but the absorbed intensity cannot exit because it is re-irradiated as infrared. So both cars get hotter by this mechanism.
My partial solution to the problem would be the following: A WHITE CAR and A BLACK CAR are both irradiated with intensity I. In both cars, a fraction $aI$ passes through glasses, and a fraction $(1-a)I$ irradiates the other parts of the car. WHITE CAR: reflects totally the intensity $(1-a)I$, and the intensity $aI$ does the greenhouse effect. BLACK CAR: absorbs totally the intensity $(1-a)I$, and the intensity $aI$ does the greenhouse effect. The intensity absorbed by black paint is both re-irradiated outside the car and inside, contributing to increase the greenhouse effect. This should prove that the equilibrium temperature of the BLACK CAR is higher.
Is my reasoning correct?
