White roofs save the world?

Dr. Hashem Akbari of Lawrence Berkeley National Laboratory in California calculates that a 1,000 square foot area of rooftop painted white has about the same one-time impact on global warming as cutting 10 tons of carbon dioxide emissions.  So…if millions of homes in the U.S. simply painted the roof white, this could save tens of millions of CO2 emissions….and it wouldn’t cost much, compared to other strategies.

Someone apparently calculated that if all the roofs in the world were white, global temperature would likely drop 1 degree centigrade.  This sounds good, but SciGuy blog is skeptical: he says this zero-dimensional model doesn’t take into account cloud cover. He also notes we would have to paint every roof in the world white to approach even a 1-degree Celsius differential. Is there even enough white paint in the world to do that in the next decade?

Okay, perhaps it’s not global salvation.  But research does support the idea of painting a roof white to cool a building.  If it saves a few bucks off the electric bill and maybe helps CO2, seems like it might be worth a try.

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One thought on “White roofs save the world?

  1. We have indeed done that calculations. Cities make about 2% of dry land area. Increasing the reflectivity of half of them (1% of 2%) by about 0.1 (that is increasing roof reflectivity by an average of 0.25 and pavements by an average of 0.15) will cool the world about 0.05 degree C. This is equivalent to not emitting (or offsetting) 44-80GT of CO2. For comparison, there are about 600 M cars in the world, each emitting on average about 3 tons of CO2 per year. The CO2 offset of cool cities is equivalent to 20-40 years of emissions from all cars.
    Hashem Akbari

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