the film forum library tutorial contact

Study: White Rooftops Could Curb Climate Change by Eoin O'Carroll Christian Science Monitor, September 10, 2008

If the world's 100 biggest cities were to whiten the roofs of all of their buildings and use more reflective pavement, the global cooling effect would be huge, a new study has concluded.

Speaking at the Fifth Annual California Climate Change Research Conference in Sacramento, Hashem Akbari, a physicist with the Lawrence Berkeley National Laboratory, said that he has created a formula to determine how much heat-trapping carbon dioxide would be offset by reflecting the solar radiation back into space. In his presentation [PDF], he said that replacing the dark shingles on a 1,000-square-foot roof - the average size of an American home - with white material would offset 10 metric tons of greenhouse gases.

His paper, "Global Cooling: Increasing Worldwide Urban Albedos to Offset CO2," will be published in the journal Climatic Change.

While this may sound like greenwashing (but with whitewash), the potential savings here are huge. The LA Times walks us through the numbers:

Globally, roofs account for 25% of the surface of most cities, and pavement accounts for about 35%. If all were switched to reflective material in 100 major urban areas, it would offset 44 metric gigatons of greenhouse gases, which have been trapping heat in the atmosphere and altering the climate on a potentially dangerous scale.

That is more than all the countries on Earth emit in a single year. And, with global climate negotiators focused on limiting a rapid increase in emissions, installing cool roofs and pavements would offset more than 10 years of emissions growth, even without slashing industrial pollution.

It sounds like a foolproof plan, but Keith Johnson, the Wall Street Journal's eco-blogger, is skeptical that we could pull it off:

Like with most grand plans, the devil is in the details. In many places, local zoning regulations strictly dictate architectural styles, including roof colors. Where white roofs are allowed or even required, progress comes piecemeal. Since 2005, California's had a building code that mandated white roofs for commercial buildings, and is currently beefing that code up to include other kind of roofs.

But even the Golden State's environmental enthusiasm has limits-it can't make black-topped roads white overnight. The scale and cost of any program that would re-top all the roofs and paved surfaces in cities the size of Los Angeles, Mexico City, New Delhi, and Tokyo simultaneously makes Al Gore's plan to power America with 100% renewable energy in ten years seem cheap and doable by comparison.

That said, I'm not thrilled about the prospect of driving - or crossing a busy street - on a reflective surface. And not all of us get to live in sunny California. Sure, a white rooftop may cut my air-conditioning costs in the summer, but when winter comes, what will it do to my heating bill?