Reflective roofing has long seemed one of the best geoengineering options to help turn the rising tides of Global Warming. An opportunity to reduce energy use through reduced cooling demand and longer lasting roofs, to improve urban life (and cut energy requirements) by reducing urban heat island impacts, and to contribute to fighting global warming by reflecting solar radiation back into space.
It seems, however, that this opportunity might be even greater than previously believed. Global Cooling: Increasing World-wide Urban Albedos to Offset CO2 (pdf) suggests that white roofing of just 100 cities could handle Global Warming temperature increases.
This study comes from some of the nation’s top experts in roofing, from Heat Island Group at Lawrence Berkeley National Laboratory which focuses on this serious urban challenge:
“Heat Island research is conducted to find, analyze, and implement solutions to the summer warming trends occurring in urban areas, the so-called ‘heat island’ effect. We currently concentrate on the study and development of more reflective surfaces for roadways and buildings.”
a 1,000-square-foot roof — the average size on an American home — offsets 10 metric tons of planet-heating carbon dioxide emissions in the atmosphere if dark-colored shingles or coatings are replaced with white material.
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.
This is quite impressive and a path that almost certainly is worth pursuing … even aggressive. To be clear, simply addressing temperature will not deal with all of the challenges related to CO2 emissions. For example, reflective roofing would do nothing relative to the acidification of the oceans and this threat to ocean (and human) life. But, the temperature impact in terms of cooling could be quite important in helping to create breathing space as humanity lowers its carbon footprint through reduced energy use combined with ever-more low/no-carbon energy sources.
The core geoengineering principle should be:
win-win-win. A proposal that, in a systems of systems effort, provides multiple wins and does not solely address temperature. Thus, a proposal that offers real potential for improving economy, reducing carbon, and contributing to reduced temperature (both directly, somehow, and indirectly through reduced carbon loads or carbon capture) would seem to merit greater prioritization than high-cost efforts that would solely impact “temperature” but not impact (or worsen) the carbon load equation.
And, this is the case with reflective roofing on a large scale,
“I call it win-win-win,” Akbari said. “First, a cooler environment not only saves energy but improves comfort. Second, cooling a city by a few degrees dramatically reduces smog. And the third win is offsetting global warming.”