Sunday, June 14, 2009

Doubts Raised about Effectiveness of White Roofs for Combating Global Warming

The US Secretary of Energy Steven Chu has advocated painting roofs white as a way to limit global warming. The advantage of white roofs over dark roofs is that white roofs reflect most of the sunlight hitting the roof back out into space whereas dark roof absorb most of the sunlight as heat. An article in the Washington Post says that according to Chu recent research shows that by painting about 63% of the roofs white in 100 large cities in temperate and tropical regions around the world that would equate to removing all of the cars in the world from the road for 10 years. However, the Post article notes that climate scientist Ken Caldiera from the Carnegie Institution in Stamford, California is less than enthralled with idea. Says Caldiera “It’s hard enough, in many of the cities in the world, to keep the streets swept, much less to keep the city reflective.” If painting roofs white includes slanted roofs such as those on houses, that raises the problem of aesthetics as the Post article points out. Of course, there are other things that can be done with roofs to help the cause besides painting them white. They can be covered with solar panels. Also, instead of white roofs they can be turned into green roofs by covering them with soil and adding plants. In any case, for flat roofs at least, white roofs, green roofs, and solar roofs all seem preferable to dark roofs.