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It's Getting Hot Out Here By Arden Miller, CZM If you were to overhear someone talking about "urban heat island," you might assume they were discussing a t.v. show. Unfortunately, they're not. While the phrase is evocative of a "Survivor" type reality show, urban heat island refers to the unique phenomenon whereby many cities, lacking in greenery and covered in concrete, are 2 to 10 degrees hotter than surrounding lesser developed areas. Cause and Effect When you have an area where there is a large collection of tall, dark buildings and parking lots made of asphalt, two things happen: first, the black asphalt rooftops and parking lots absorb the heat (much like a person who is wearing black on a hot summer day); second, the tall buildings trap heat. Adding to the sticky, icky heat felt when temperatures reach high levels are the additional air pollutants—pollutants form faster in hotter weather, and vehicle emissions in urban areas create extra ozone that, without adequate amounts of greenery to give off energizing oxygen, stick in the air and can make it difficult to breath. Combined, this effect is known as urban heat island. Hotlanta: A Case Study Atlanta is often referred to as "Hotlanta" for good reason. Between 1970 and 1980, the population grew by 27 percent—it was a "hot" place to move to. By 1990, the population increased by an additional 33 percent. Suburbs doubled in size, nearly 350,000 acres of forest were cleared to make way for housing and roads, and dark roofs and pavement took over. And then things got really hot. Meteorologists regularly noted that temperatures inside the city were 10 degrees higher than in the outlying areas.1 Ten degrees is a lot, especially in a southern city. And, while difficult to prove the exact numbers of oxygen-giving greenery that would need to be planted to completely ameliorate this situation, the more vegetation on the 'island,' the better. When it comes to putting their money where their heat island is, Atlanta's City Hall is leading by example: they've had a 3,000 square foot green roof since 2003. With this roof's high visibility (it's open to the public during business hours and visitors and employees can eat in a cafeteria that overlooks the roof garden), the message that green roofs are functional and beautiful is spreading. Hotter than Hell's Kitchen But it's not just the south that has a heat problem: in New York City, more than Hell's Kitchen can get very, very warm in the summer. And, like Atlanta, the higher city temperatures are attributed to urban sprawl. To address their island's heat island effect, Manhattan's Greening Gotham Organization has formed an alliance with the national environmental organization, Earth Pledge, and together they have created the Green Roof Initiative. One offshoot of this collaboration (which includes city, state, and private citizens) is the green roof demonstration project at Pace University. The U.S. Environmental Protection Agency and Pace University will monitor the effects that the 30,000 square foot green roof—one of the largest in the city—will have on the climate. On a smaller scale, Greening Gotham encourages private citizens to add green to their rooftops by offering the consulting services of experienced pro-green roof professional engineers and architects, often for free. And such grass roots initiatives and collaborations are forming in other cities. As of early 2006, Boston, Chicago, New York, Portland, Seattle, Washington, D.C., and Toronto are watching more and more green spring up. Someday, with proper planning and planting, "urban heat island" will be nothing more than a reality show and we can choose to watch it, or to change the channel. 1 Dr. Keith Heidorn, The Weather Doctor, July 1, 2002 | |||||||||||||||||||||||||||
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