Urban heat islands

In the woods, the native rhododendron are in bloom with their intense white flowers. Already gone are the pink and white mountain laurel and the hybrid colorful rhododendron of early may. In a few weeks, the summer wildflowers will grace our meadows and open land areas. Even urban open spaces will be sporting some color as many of our wildflowers are capable of growing just about anywhere.
I am sure you have noticed how often it is warmer in our urban areas than the surrounding countryside. Even in places like Uniontown, Brownsville and Charleroi, temperatures tend to be a few degrees warmer than outside our towns. In the winter season, evidence of this clearly shows in how much less snow accumulates in towns than in the country. Urban areas are made of materials that hold heat — asphalt, concrete, dark roof tops, air conditioning units and of course trucks, cars, power plants and industrial sites.
In the summer, this trapped heat can make you feel miserable. Just think of Phoenix, Arizona. On the first day of summer, the temperature soared to 122 degrees and also saw temperatures above 115 for five consequences days. Twelve people died from this early heat wave. Simply put, just about all urban areas large and small trap a lot of heat and create these heat islands. Summer nights in some of the big cities are especially prone to form heat islands as these areas cannot radiate the heat away due to all the concrete, asphalt and buildings.
Another big contributor is the fact that many urban areas have lost their tree canopy. Trees provide vital shade, give off carbon dioxide and help keep areas cooler. Coming off the shaded bike trail onto the asphalt parking lot in Ohiopyle State park today was proof of how small an area of concrete and asphalt is needed to create a heat island. Downtown Pittsburgh is always a few degrees warmer than its surrounding neighborhoods and usually 4 or 5 degrees warmer than the suburbs of the city.
A recent article in USA Today discussed the urban heat island in Louisville, Kentucky. Broadway Street in downtown area which has no trees averaged 6 degrees warmer than nearby Ruby Lane, a tree lined street just east of town. Many cities are losing what tree canopies they have. Disease, accidents, age, stress and pollution are the culprit. According to the article, the city of Louisville received a matching grant of $1,000,000 for planting trees. This was part of a national trend to bring nature back to our cities and reduce these heat islands. Out of a 60 city study, 57 of them had significant heat island problems. On a summer day with the right conditions, heat islands can produce temperatures 10 to 20 degrees higher than out-lying areas. The average temperature difference is more like 4-6 degrees and this is significant, the study said.
The National Weather Service warns that all of this excess heat is dangerous and it may surprise some to know that heat is this biggest weather related killer in the United States. Some 12,000 deaths are attributed to heat waves each year. Many of these are elderly people in large urban cities. They are especially vulnerable when summer storms knock out power in our urban areas. A heat wave in Europe during the summer of 2003 killed 20,000 people in France and an estimated 70,000 in Western Europe.
Cities are realizing the value of their trees and are beginning to try and reverse the trend. Last year, Pittsburgh had a tree planting program and planted thousands of trees, many along the new bike trails in the city. With the climate warming, urban and city planners are looking at trees as a possible answer to the growing heat island problem. You can help by planting a few trees in your yard or perhaps the vacant lot down the street.