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TODAY Thursday 25 September 1997 Each weekday. Conn Nugent on what's new in the world, on the site.

 

TODAY IN THE WORLD: The Cooling of Los Angeles

Central Los Angeles on a hot day is generally five degrees warmer than its far suburbs. According to an article in MIT's Technology Review (passed on to us by the Energy Foundation), almost all of that temperature differential can be ascribed to "dark horizontal surfaces" that absorb sunlight. Roofs and pavements, mostly.

The authors of the article -- Arthur Rosenfeld, Joseph Romm, Hashem Akbari and Alan Lloyd -- describe two important consequences of such urban "heat islands." One is that demand for air-conditioning goes up. "One sixth of the electricity consumed in the United States goes to cool buildings, at an annual power cost of $40 billion," they write. The second consequence is foul air. "A five degree heat island greatly raises the rate at which pollutants -- nitrogen oxides and volatile organic compounds emanating from cars and smokestacks -- 'cook' into ozone, a highly oxidizing and irritating gas that is the main ingredient of smog. In Los Angeles, ozone rises from an acceptable concentration at 70 degrees to unacceptable at 90 degrees."

The authors support the standard strategies for reducing pollution and greenhouse emissions -- efficient vehicles and appliances, mass transit, reformulated gasoline -- but they say that the best and cheapest approach would be to change the color of those dark horizontal surfaces and to plant lots of green. "With white roofs, concrete-colored pavements, and about 10 million new shade trees, Los Angeles could be cooler than the semidesert that surrounds it, instead of hotter." Or so say the authors' computer simulations, which also predict an 18 percent decline in the need for air conditioning and a 12 percent decrease in the amount of ozone above the state's health standards. Even if those simulations are wrong by half, the savings in money, energy, and medical expenses would still be enormous.

Relatively easy technical fixes are at hand. Roof tiles and shingles coated with titanium dioxide provide the light color required without any increase in maintenance or cleaning costs. Simple adjustments in the color of paving aggregates and their "topping off" materials (carbon black bad, cement good) would make an enormous impact. And then there are the trees. While all trees are wonderful as carbon sequesterers (and thus global warming modifiers), and almost all act as efficient air coolers through the process of evapotranspiration (think of an extra-fine water sprinkler), some are much better than others in the matter of pollution fighting. Weeping willows and eucalyptus trees, for example, emit high levels of volatile organic hydrocarbons (VOCs) which can combine with nitrogen oxides to form smog. Better to stick "VOC-free trees" like the maple and the ash.

Imagine a bird's view of a hardwood forest of ten million trees, shading and veining an urban landscape of whites and pastels, all set in one of the world's most equable climates, bounded by mountains and a vast blue ocean. It's got nothing on Broadway, of course, but you can see why people might want to live there.

 

TODAY ON THE SITE:

There's no reason not to subscribe to "The Grove," Lib Tree's bi-weekly electronic newsletter. It's free, it's useful, and it carries Donella Meadows as a regular and exclusive contributor. Donella's feature is called "Community Conversations." With Donella, the word community can denote both her cooperative housing group in New England and her far-flung Balaton Group of green thinkers from around the world. In the most recent issue of The Grove, Balaton colleague Haruki Tsuchiya test-drives the infant members of Toyota's new generation of energy-efficient vehicles. Mr. Tscuchiya gets behind the wheel of an all-electric RAV-4, a new gas/electric hybrid Corolla-type, and a special prototype fuel-cell car. Eat your heart out, Auto Week.

 

Recent "Today" columns:

9/24: The Boy Who Stalks California
9/23: Fire!
9/22: More Logging and Fishing
9/19: "Here, Sir, the People Rule"
9/18: Dr. Pangloss and the Land Mine Treaty
9/17: Outsourcing Pollution
9/16: In the Preservation of the Funky
9/15: The Problem With Health
9/12: The Automobile Crisis of 2020
9/11: Gratifyingly Inept Adversary

To access more "Today" columns, click "Archives" below.