Guest blogger Seth Shostak proposed painting our roads white a few days ago, creating somewhat of a hubbub. The idea of painting roofs white is a less controversial idea (perhaps you've seen photos of the Greek islands?), but one which is really starting to take off.What's interesting is that the anti-climate change benefits come only slightly from the albedo effect of the roof-that is, that the sun's rays hitting the white surface bounce off and go back into space, thus not warming the planet. Rather, what's important is that your house is a lot cooler, because it doesn't have a black roof that is sitting there, boiling (roofs in New York City have been measure at temperatures of 180 degrees Fahrenheit). When your house is cooler, you turn the air conditioner on less. Less air conditioner means less electricity, which means fewer emissions from coal plants. If 80 percent of U.S. houses had white roofs, it would be the equivalent of taking 1.2 million cars off the road, annually.Here is, from the Times, a chart of where we would see the biggest improvements by converting standard roofs to white roofs (click to enlarge):As you can see above, another interesting fact is that this solution is not as catch-all as we might potentially like. There are some places where having a white roof is actually going to make matters worse. In places with cold winters, there is a good amount of the year when you want your house to be as warm as possible, and having a heated black slab on the top of that helps immensely. In colder climates, a white roof, while cooling in the summer months, actually results in higher emissions due to extra heating in the winter. Just another reminder that we're not going to find a panacea to this problem; it's going to be a mix-and-match of thousands of smaller innovations that eventually combine into one solution.