Making roofs white “changes the reflectivity . . . of the Earth, so the sunlight comes in, it’s reflected back into space,” [Energy Secretary Steven] Chu said. “This is something very simple that we can do immediately,” he said later.
The article continues:
White roofs work because of the physics of sunlight. Dark roofs absorb and hold more than 80 percent of solar energy, while white ones can reflect 75 percent of it away. That makes a white-roofed building cooler and cheaper to air-condition.
In his talk, Chu cited new research from his former laboratory, the Lawrence Berkeley National Laboratory in California, which imagined the result of painting about 63 percent of the roofs white in 100 large cities in tropical and temperate areas worldwide.
It estimated that would provide about the same climate benefits as taking all the world’s cars off the road for 10 years.
Now would you be able to do that? Probably not. But it wouldn’t be a bad idea going forward to have roof’s of flat buildings be a reflective. In fact California has had this in effect since 2005. DC will follow suit next year but will also allow buildings' roofs to be covered in vegetation.
The article quoted the usual skeptics that said you would never be able to change enough roofs to make that much of a difference as described above.
But they are missing the point. There’s won’t be one silver bullet to solve the problem of global warming. It will be many many little things that make an impact. This is just one more way to make that impact. And after all, if the buildings are going to be built anyway, why not make the effort to have the roofs reflect as much sunlight as possible back into the sky.