White roofs combat climate change

Making roofs and pavements in the worlds 100 largest cities white would have a significant impact on combating climate change, according to new research.

Data released at the annual Climate Change Research Conference showed that making roofs and pavements more reflective would help offset massive amounts of carbon dioxide.

The effect is based on the fact that the reflective surfaces would reflect rather than absorb heat. For buildings this would mean that they would use less air conditioning, a process which is emissions-heavy. California already requires flat commercial structures to have white roofs.

"White roofs can cut a building’s energy use by 20 percent and save consumers money," California Energy Commissioner Art Rosenfeld. "The potential energy savings in the U.S. is in excess of $1 billion (£569 million) annually. Additionally, by conserving electricity, we are emitting less CO2 from power plants."

Hashem Akbari, a physicist at the Lawrence Berkeley National Laboratory, making a roof with a 1,000 square foot area in a reflective rather than absorbent colour would offset ten tonnes of carbon dioxide emissions. The cumulative effect of making the change on roofs, which account for 25 per cent of the surface of cities, and pavements, which account for 35 per cent of the surface of cities, in 40 of the world's cities would be to cut emissions by 44 gigatons of greenhouse gasses.