Learning Objectives
The students who I teach are living in an urban heat island, along with 80% of other Americans. The term urban heat island simply describes built up urban areas that are hotter than nearby rural areas.5 The annual mean air temperature of a city with one million or more people can be 1.8 to 5.4°F (1 to 3°C) warmer than its surroundings during the day, and on a clear, calm night, this temperature difference can be as much as 22°F (12°C).6 Cities smaller than one million people total, such as Richmond (220,000), are still considered urban heat islands, however in smaller cities it is likely that the effects are not as severe. So, why does this happen?
As cities are built with impervious materials, such as brick, steel, and asphalt “we change the balance that natural unaltered landscapes have with the sun.” In addition, paving green spaces into water-resistant surfaces, such as roads and parking lots, eliminates cooling effect of evaporating water after a rainstorm.. Instead, that water is directly diverted into local bodies of water, such as streams, lakes, and rivers. In addition, buildings that are made out of impervious materials can “absorb and hold onto the sun’s energy during the day, and then turn around and emit that heat back into the air at night.7 When compared with natural vegetative areas, built up areas with more buildings containing materials such as concrete and asphalt contribute to the urban heat island effect because the darker materials absorb more light and have a higher heat capacity, thus holding a lot of heat from hotter days.
Why should we care about this? There is a major strain on our energy resources, leading to rising energy bill costs. There is also a disproportionate effect on people who can’t afford to cool their homes, such as the massive 1995 heatwave in Chicago. After teaching my unit, my goal for my students is to be exposed to ways that they can positively affect change in their own communities as it relates to the improving the environment. My students will design their own response to mitigate excessive heat in their own communities. To summarize what they have learned, my students will document their findings by writing to their city council representatives to encourage and advocate for change.
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