Urban Heat Island

The Urban Heat Island effect shows higher temperatures in cities compared to rural areas.

The urban heat island effect (UHI) describes a phenomenon where urbanized or metropolitan areas exhibit significantly higher temperatures than the surrounding rural regions. These temperature differences arise primarily from human activities and the specific characteristics of the built environment. During the day, temperature differences can occur between 1 and 7 °F (0.5 to 3.9 °C), and at night between 2 and 5 °F (1.1 to 2.8 °C), with heavily urbanized areas potentially exhibiting even larger variations.

The causes of urban heat island formation are diverse. On one hand, urbanization often leads to a loss of green spaces, which contribute to natural air cooling through shading and evapotranspiration. On the other hand, materials like asphalt and concrete absorb more heat and release it more slowly, especially at night. Urban geometry, particularly the presence of tall buildings and narrow streets, can trap heat and hinder air circulation. Furthermore, waste heat sources such as vehicles and air conditioning units contribute to the increase in ambient temperatures.

The impacts of the heat island effect are extensive. It raises health risks, particularly during heatwaves, increases energy consumption due to higher cooling demands, and can deteriorate air quality by promoting ozone formation. This poses not only a challenge for public health but also has economic repercussions. To mitigate the UHI effect, strategies such as the creation of green spaces, the use of reflective materials, and a thoughtful urban planning approach are crucial, especially in the context of climate change, which can intensify extreme temperature occurrences.