Heading into the weekend, I wanted to share this nugget of truth with you, courtesy of Mark Kleiman:
There are, however, at least two conservation measures that have, as far as I can tell, modest costs (and in one case huge side-benefits) and potentially substantial energy-saving potential. Both have to do with reducing the “heat island” effect that makes cities much hotter than the surrounding countryside, causing discomfort (if not worse) and pushing up air-conditioning usage.
Today’s Washington Posthas a story about tree-planting in urban areas. The numbers are spectacular. In Los Angeles, tree-planting could reduce temperatures by as much as 5 degrees F., in addition to reducing air pollution and improving visibility. Yet apparently the urban, and especially suburban, tree cover ratios have been shrinking severely.
It also turns out that much of the “heat island” effect stems, not from the concentration of heat-producing activities, but from the fact that urban surfaces, especially walls, roofs, roadways, and parking lots, are a lot darker, on average, than rural landscapes. Lower albedo means more retained radiant energy. Replacing a black roof with a white one, or lightening up roadway and parking-lot asphalt by mixing in some chalk dust, could make a substantial difference at a trivial cost.
The problem is organizing to get the trees planted and the surfaces lightened. Giving away seedlings is one way to get homeowners to grow trees; an alternative would be to provide a small reduction in property tax for each tree on a lot. The roof-and-parking-lot problem could be handled with either incentives or building-code modifications; the roadway problem is just a matter of changing the specifications when road-building and repair contracts are let. But of course all that is much easier to write than it is to do in practice. (Not all trees, for example, are created equal.)
Still, compared to other ways of reducing energy use and cleaning urban air, trees and high-albedo surfaces seem ridiculously cheap.
There’s a big political problem here. A candidate who says he’s going to deal with our energy problem by drilling in ANWR will have his opinion taken seriously by reporters and pundits, even though the actual contribution of such drilling to reducing imports is trivial. But a national-level politician who proposed tree-planting or chalk dust would wind up the butt of jokes on late-night TV.
When I was in Chicago last month, I visited the Nature Museum there. They combined the two ideas listed above: they planted a garden on their roof. It traps less heat than traditional roofing surfaces, collects rainfall for the plants growing there, and is a good insulator. There’s nothing but benefits, so why we don’t see more “green” roofs out there?