Islands are nice places to visit, especially in the cold months and especially if you are not a skier. But certain islands can cause discomfort. At least that is what NASA is saying. They are called "heat islands."

It turns out that urban, largely concrete landscapes retain heat. For this reason, cities are often warmer than rural areas. This is global warming, but at a more local level.

NASA has studied these human generated heat clusters caused by our city landscapes. We have known for a long time that excessive pavement causes flooding. Now, it turns out that all of this pavement and blacktop can actually alter our urban climate.

The more development, the more surfaces throughout an entire community become hotter. In turn, ambient air temperature increases. It is this phenomenon that is called the "urban heat island," and according to NASA can be responsible for increases in city air temperatures.

Energy demand is affected by this manmade island as well. The resulting higher temperatures increase the demand for cooling energy, which in turn increases demand for energy. As a result, energy costs may rise. Since electricity is often produced using coal, and since many coal plants are large air polluters, increases in energy use directly translate into potential increases in air pollution. All of this because of the colors of our roof tops, paving, and our failure to plant enough shade trees.

NASA has proposed some solutions to this heat island problem. White roofs are now being suggested, and are regarded as a better choice than black roofs. While white roofs may not last as long, energy savings may offset early replacement costs.

While many local governments already have shade tree ordinances, the focus on roof and pavement colors is relatively new. And the NASA studies strongly suggest real benefit to developers, municipalities and the environment if these fixes are put into play.

Thus far, NASA has studied Atlanta, Salt Lake City, Sacramento, Houston, Los Angeles, Chicago and Phoenix. Sacramento already requires new parking lots to include enough trees to shade at least half of a parking lot after 15 years. And in January, Sacramento intends to offer the nation's first incentive for white roofs on both homes and commercial buildings.

Anyone who visits warm climates cannot help but note that people where light colored clothing, and take refuge under tree shading. For developers and municipal governments alike, the news from NASA is clear: they should also encourage the use of light paving and roof tops, as well as the planting of shade trees.

Published: November 24, 2000

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