Before you paint your roof white in an effort to reduce global warming, you should read this.
A new study published in the Journal of Climate claims that painting rooftops white—a method championed by energy secretary Steven Chu and others to combat climate change—only minimally reduces local cooling, and actually causes a slight increase in overall global warming.
How the Heck:
- The researchers used a global climate model called GATOR-GCMOM [PDF], which incorporates a host of data from satellites and weather stations worldwide. It models how relationships between various environmental conditions, like the presence of clouds or pollutants, will affect local and global climate.
- The model found that more white roofs means less surface heat in cities (which is obvious enough to anyone who’s sat in a car with a black interior in the sun). Lower local temperature means less water evaporates and rises up to eventually form clouds, says lead author and Stanford University researcher Mark Jacobson. The decrease in clouds allows more sunlight to reach the Earth’s surface, leading to higher temperatures overall.
- The model also predicts that much of the light reflected by rooftops will eventually be absorbed by dark carbon soot and particulates that are especially prevalent in the air above urban areas. This could limit local cooling and cause warming elsewhere as the particles drift away.