Combating global warming with white paint
I was idly thinking about this, and wondering why this has any global effect. Sure, a white house will stay cooler inside than a dark one. But if the light is reflected into the atmosphere and trapped there by green house gasses, you haven't won anything. Similarly, even if a dark object absorbs heat, it'll radiate that heat back out when the air cools off. Is there a difference (for the planet overall) between reflecting it right away as light and radiating it later as heat?
First off, keeping the house cooler helps simply by reducing the need to spend energy on air conditioning or fans.
Second, it turns out that the atmosphere allows far more visible light through than it does heat radiation. (See e.g. here.) So heat radiated back out tends to stay in the atmosphere, while 70-75% of reflected, visible sunlight will pass back out into space.
The one bit left unaddressed is the cost of producing, transporting, and applying all that paint.