Paint Your Roof White to Fight Global Warming

U.S. Department of Energy Secretary Steven Chu has announced that cool-roof technology will be implemented, when cost-effective, on federal buildings across the country.  A new study by scientists at Lawrence Berkley National Laboratory has demonstrated that rooftops painted a lighter color have a higher albedo, therefore reflecting more incoming solar radiation.  Buildings with lighter-colored roof-tops require less energy to cool, conserving energy. Cooler roofs also reduce the urban heat-island effect, lowering the temperature in large cities.

Rooftops and roads comprise the majority of urban landscapes, and have a mean albedo of 0.14, according to the study. By modeling the climatic impact of raising the urban albedo in all temperate and tropical regions of the globe by 0.1 albedo units, the researchers found that localized, cooler temperatures resulting from the higher albedo would reduce the global average temperature by 0.01°C. In terms of emissions reductions, increasing rooftop and road albedos by 0.15 to 0.25 units is equivalent to taking 300 million cars off the road, a carbon offset of 57 gigatons of CO₂.  However, this is a one-time offset, and 57 gigatons of CO₂, although a sizable quantity, is the equivalent of about two years of emissions— relatively small compared to the total amount of human CO₂ emissions since the mid 1800s.