Monday, July 8, 2013

Heat Islands: Not a Vacation Destination

Where do you go to beat the heat when the weather warms up? A recent bout of unusually hot 90-degree weather here in the Seattle area reminded me why I generally retreat to natural outdoor spaces to find relief from the stifling heat.  This heat wave revealed the stark contrast in temperatures experienced in wooded, natural areas and green space versus paved, developed areas. During this hot weather, a half-hour drive from the developed, paved, tree-bereft neighborhood where I currently live and the wooded, more-or-less natural landscape of the neighborhood where my family lives revealed a whopping 12-degree F temperature difference!  Even without a thermometer, this variation in degrees of discomfort was easily felt.  

Walking across the 95-degree parking lot to get in my car at the beginning of the journey, I felt every bit of heat absorbed by the pavement throughout the day radiating up around me.  Even standing in the meager shade of one of the few trees on the property offered little relief and no protection whatsoever from the flow of hot, dry air rising from the baked pavement.  Waves of heat shimmered in the still air.  It was hot.  I started sweating instantly and could feel the penetrating sunlight already warming my skin, threatening to burn me from the inside out, and blinding me as it reflected unabated off the bare surfaces of pavement and buildings.

Contrast this with that I felt after the half-hour drive, stepping out of the car onto the driveway at my family’s house, shaded by the tall trees and abundant foliage that dominates their mostly-wooded neighborhood.  The temperature had cooled to a comfortable 83 degrees.  Even standing in the direct sunlight was still comfortable, with a light breeze cooling my skin.  Cool air rose up from the earth below, hovering refreshingly around my ankles.  The air moving in and out of my lungs was cooler, damper, and felt cleaner.  A gentle wind stirred the branches of the towering Douglas Firs, maples, and cedars that shaded the yard from the sun’s sweltering heat, illuminating the outdoor space with a soft green glow—no sunglasses required.  

Having spent most of my life living in homes surrounded by a more natural, forested setting, I am still trying to adapt to the surprisingly different climate created by an impermeable landscape of paved parking lots, freeways, and buildings unsheltered by trees.  Upon noticing these different “microclimates,” I couldn’t help but wonder—how much warmer would our planet be if there were fewer trees and more developed space?  After doing a little research, I discovered that (shockingly) I was not the first person to notice this phenomenon, and that in fact it has a name: the Heat Island Effect.  According to the EPA, the Heat Island Effect is a real problem that can create temperatures within cities that are 1.8 - 5.4 degrees F warmer than their surroundings during the daytime, and as much as 22 degrees F warmer at night.  In addition to uncomfortably warmer temperatures, Heat Islands also result in increased energy consumption (due to the need for air conditioners) which in turn leads to increased air pollution and emissions of greenhouse gases.  Human health is also threatened due to the high levels of air pollution and dangerously hot temperatures.  

Temperature Variations: the Heat Island Effect

With the realization that more and more rural land is being paved over and developed into subdivisions, it may be useful to keep in mind the important benefits of green space and forested land in relation to providing a livable local climate.  After discovering the Heat Island Effect and experiencing it firsthand, I know for sure that I do not want to go there on a permanent vacation!

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