Sunday, January 4, 2009

Greening Cityscapes

Way back in 2009, China Greenspace wrote about the utility of a co-benefits approach to simultaneously reduce both greenhouse gas emissions and improve air quality. A great new post on the blog Climate Progress details one such co-benefit strategy: urban heat island mitigation.

The post itself is worth reading in its entirety, but briefly, urban heat islands are local and regional surface temperature anomalies that occur as the result of surfaces and processes associated with urbanization. For example, asphalt, which covers urban roadways, parking lots, etc., has a lower albedo (reflectivity) than grassland, absorbing more heat. Urban areas can thus be on the order of 5 degrees Fahrenheit higher than surrounding rural areas. Given the degree of urbanization on the planet, the urban heat island effect contributes measurably to global warming.

Urban heat island mitigation seeks to minimize this contribution by using high-albedo surfaces (painting roofs white, for example), planting trees, etc. Because higher urban temperatures also aid in ozone and smog formation, urban heat island mitigation also helps to improve air quality.

Perhaps most importantly, urban heat island mitigation is relatively low-cost. As the Climate Progress post notes, residents of some desert cities are still required to paint houses white. And for China, urban afforestation may be particularly appropriate. China's countryside plays host to the world's largest afforestation program (the Sloping Lands Conversion Program, see previous post), which could logically be extended to urban areas as well.

Now there's an idea worth mulling over in the new year. A happy one, by the way!

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