There are a lot of smart people out there busy devising clever ways to help combat global warming -- Bill Gates' and his recent support of algae fuel research, for instance, not to mention yesterday's announcement of the long-range electric Chevy Volt -- but there are some very simple, low-tech steps that can be taken, as well.

It's obvious why most roofs and roads are black: that's the color of asphalt. But black absorbs heat while white reflects it, and according to a new study if the 100 largest cities in the world were to paint all their roofs white and switched to lighter-colored road materials, it would reflect enough light and heat back into space to offset all the global warming we've experienced in the last few decades. (Sounds crazy, I know -- but consider this: a white roof in a warm climate can decrease air conditioning bills about 20%.)

Of course, people living in cold climates have a different set of challenges -- and a black roof can be advantageous during chilly winters, when retaining heat is what's important. Regardless of that distinction, however, it seems we should all be paying more attention to what color our roofs are.

Via Ecogeek.