July 30, 2009

White Roofs for a Red Earth? The Geoengineering Debate

Today the New York Times reported on a growing trend in housing construction: the decision to use lighter-hued materials as opposed to darker, traditional counterparts such as slate and asphalt. The article focuses on the economic benefits families and businesses can enjoy if they follow Energy Secretary Steven Chu’s advice and make this switch. In many cases, using light-colored roofing materials or simply painting roofs white can increase building reflectivity, thereby cooling the structure and reducing the residential or corporate investor’s energy costs. The economic basis for the white-roof transition is fairly sound, though results vary by region and depend on other factors such as average exposure to sunlight.
However, when considering approaches to greenhouse gas reduction, it is important to consider just not the aspect of energy savings, but that when aggregated, seas of white-shingled roofs may actually have the potential to alter the Earth’s albedo, a measure of the planet’s overall reflectivity, and, thus, impact the climate in ways that we do not quite understand.

While the article narrows its scope to focus solely on the energy-saving dimension, the omission by author Felicity Barringer of any mention of roof-whitening as a method of geoengineering, the yet disputed term for the process of using technology to cool the climate, ignores an important side of the debate over the best ways to mitigate future climate change.
White roofs are relatively uncontroversial (other suggestions include space mirrors and desert blankets) and even if whole cities adopt the construction technique, the effects of geoengineering-via-roof-whitening would likely only be “regional and patchy.” Here, too, is a problem with Barringer’s account: while failing to address the geoengineering side of the debate, it conveys that whiter roofs have the potential to “help cool the planet.” (She may well be referencing temperature savings due to fewer emissions, but her language is vague a potentially dangerous way.)

The debate about how to cool the planet is, as it were, fast heating up.  Some advocates who call for geoengineering solutions would use it as an excuse for continuing business as usual.  In their view, increasing the planet’s reflectivity could provide a buffer against future temperature increases due to the greenhouse effect.  But before this conversation becomes politicized, much more research should be done.  The science of geoengineering is yet embryonic; it would be unwise to pursue energy efficiency approaches like white roofing without fully understanding the impact on the climate.

As private and government actors work to reduce energy consumption through efficiency, standard operating procedures will have to change, including those related to construction. As progress on green architecture continues, however, it will be increasingly important to understand construction decisions not just as a boon to energy efficiency, but as part of the important debate over climate change solutions—especially about geoengineering and other solutions in need of far more research.