What do you think of Dr Chu's idea of painting the roofs white?

[The Hope Mobile]

Should it be mandatory? Could we start with all commercial buildings first? How about all new construction? Government buildings? This would keep houses cooler in the winter . . . but potentially this could offset all global warming from what I read (if ALL buildings complied). What about other countries? Would it also be helpful if even the rest of the exterior of the house was painted white or a light color? Seems like it would. Thoughts? Suggestions? Further information?