Right now, temperatures are breaking records in the Western United States. Highs are expected to hit 113 Fahrenheit in Las Vegas and 117 in Phoenix, with a drought making matters worse.
This urban extreme heating is caused by climate change combined with what the U.S. Environmental Protection Agency calls the urban heat island effect. Buildings and roads absorb heat, especially if they have black surfaces. Tarred surfaces can be as much as 60 degrees higher than the air temperature—maybe not hot enough to fry an egg, but close. This effect creates what are known as surface heat islands. Other conditions in urban areas create what are called atmospheric heat islands. For example, there are fewer trees or other plants in cities to offer cooling shade. Buildings reduce wind flow, and venting indoor heat through air conditioning can make outside temperatures even higher. These factors intensify the effects of hot weather.
The result is that urban areas have daytime temperatures that are one to seven degrees higher than in outlying areas. The heat makes many cities downright unpleasant in the summer, and side effects don’t help. Air conditioning expenses raise the cost of living and increase the amount of pollutants in the air. Stormwater runoff has a higher temperature which reduces the quality of the water supply. As temperatures spike nationwide, cities are hit even harder.
The good news is that there are many ways to mitigate the problem. An easy one is planting more trees and plants. Native species can handle local soil and water. Greenery can make a city prettier while also making it cooler. Placing plants on roofs is a double whammy, using the power of plants to reduce the amount of heat absorbed. On roofs that cannot accommodate plants, cooler and light-colored materials can reduce heat absorption. These changes also reduce the need for air conditioning, further reducing pollutants and costs.
Smart growth strategies for new developments can further reduce heat island effects while making buildings better for living and working. The orientation and architecture of a building can make a huge difference in shade and cooling. Allowing for green spaces lets plants work their magic, while choosing colors and materials that reduce heat can shave air conditioning bills.
Cities should be hot because of their culture and energy, not because of their air temperature. Finding ways to reduce the effects of extreme heat will continue to make them desirable places to live and work.
