Would painting roofs white worldwide help stop polar ice caps melting?

Let's try to make a very conservative estimate and see. There are about 7 billion people on Earth.  Let's say that each person is responsible for 1000 square meters of surface area.  That seems quite high, but as I said we're trying to make a conservative estimate. So that's about 7 trillion square meters we have to play with. The total area of Earth is 500 trillion square meters, so that's about one percent. The biggest possible change would be going from a completely black to a completely white roof, but that is extreme, the real change would be much less than that. That would put the change to the Earth's albedo at much less than one percent. It would make a very small difference and is something that could only be done one time, while CO2 just keeps on rising.

You'd still have to weigh in the heating/cooling costs and see what effect that has, but my guess is that that would still be insignificant.

no to both........................

There is nothing Man can do to prevent Nature doing its thing. A global cooling cycle is coming and we can't stop it.

Lowering the population would certainly help. Congratulations on that, President Trump. 

Roof color is a mixed bag. At least in the temperate zone, white roofs would help in the summer but would hurt in the winter, when the reflected heat would have to be made up for by heating, usually by burning fossil fuels.

Dirac is a paid troll.

no. calculate what the surface area of all houses to the surface of the earth...

just try it and see and then you'll know