Global ChangeIntersection of Nature and Culture

Can we alter climate by installing white roofs?

Monday, January 11th, 2010

When reviewing the most popular words of 2009, I was surprised to see that “albedo” didn’t crack the top 5—Tweet, Obama, H1N1, Stimulus, and Vampire.  I bet you were equally shocked.

Albedo is a simple concept—the reflectivity of a landscape—but it’s hugely important in understanding how the surface of the Earth impacts climate.  As we saw in a recent post, things like thawing sea ice, northward advancing treeline, and asphalt paving all darken landscapes, causing more solar radiation to be absorbed and temperatures to climb—one of the reasons for the so-called urban heat island effect.

So what would happen if we were to install white roofs?  In a forthcoming article¹ in Geophysical Research Letters (subscription required), Keith Oleson and colleagues use biophysical models to address this.

Their answer:  White roofs reflect more sunlight and cool buildings.  Averaged over all urban areas in the world, the urban heat island effect declines by 33%, causing maximum and minimum daily temperatures to decrease by 0.6 and 0.3 degrees C, respectively.

At face value, this sounds great.  But, there’s a potential hidden cost of cool buildings—heating.  Interestingly, they found that white roofs caused space heating to increase more than air conditioner use declined, suggesting that energy use might actually increase with white roofs!

¹Oleson, K. et al. (in press) The effects of white roofs on urban temperature in a global climate model. Geophysical Research Letters.

Related post:   New ideas about how changing vegetation at high latitudes can cause climate warming to accelerate

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Photo credit:  http://www.flickr.com/photos/calliope/ / CC BY 2.0

Tags: albedo
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