A new study as found that painting roofs white could do as much good for the environment as taking all cars off the road for 50 years. The reflective qualities of white materials would, it is said, reflect enough solar energy back into the atmosphere that the carbon savings could be dramatic. Using lighter coloured materials on road surfaces would also contribute to the carbon savings and could help to reduce urban heat islands, when heavily built up areas create an unnaturally warm microclimates.
The effects of albedo changes (an increase in solar reflectance) in urban areas could cut global temperatures by up to 0.07 °C, equivalent to a reduction in carbon-dioxide emissions of around 150 billion tonnes, according to the study by scientists at Concordia University, Canada, published in the journal Environmental Research Letters.
Hashem Akbari, a professor of civil and environmental engineering at Concordia University said, ”Cool roofs save you energy if your building is air-conditioned. If the building needs air conditioning, installing a cool roof may actually solve your problem and you may not need it,” he said. “This all would be done at zero cost because you basically do that at the time you are changing your roof. At that time . . . you just select a white roof or light roof. If you do that then you also improve the ambient air quality within the city and you cool the globe.”
Critics of the proposal argue that the benefits of painting more surfaces would however, only have a localised effect. French climate consultant Jean-Marc Jancovici said, ”If you decrease significantly the temperature in local places with something like painting the roofs in white, it doesn’t ensure that you will have a decrease in the temperature in remote places.”
A 2009 Royal Society study into the various geo-engineering options to that could be employed to reduce global warming, also found that the painting of roofs white would have little benefit on a world-wide scale.
However in terms of a localised way of reducing temperatures in cities changing the albedo of surfaces could be an effective way of reducing CO2 emissions. By changing the reflectiveness of buildings and urban surfaces that usually retain heat there could be a reduction in the use of air-conditioning systems that contribute to Co2 emissions in many urban areas in warmer climates. With 50% of the world’s population currently living in urban areas, which is expected to increase to 70% by 2040, and pavements and roofs making up over 60% of urban surfaces, painting it white to reduce emissions could be one way of minimising our negative impact on the environment.