URBAN HEAT ISLANDS
The process of urban development profoundly changes the landscape. Natural and permeable surfaces are replaced by impermeable structures like buildings and roads. This creates what climatologists call “urban heat islands”, areas within cities that experience significantly higher temperatures compared to nearby rural regions.
These are also areas with high concentrations of people. In Europe, nearly half of schools and hospitals in cities are located in urban heat islands, exposing vulnerable populations to health-threatening temperatures as climate change impacts worsen, according to the European Union’s environment agency.
According to the US Environmental Protection Agency, the annual mean air temperature of a city with 1 million or more people can be 1 to 3 degrees Celsius warmer than its surrounding areas. On a clear, calm night, this temperature difference can even reach as high as 12 degrees Celsius compared to rural areas.
Urban heat islands are created through a combination of factors. Green spaces and vegetation play a vital role in reducing surface temperatures through evapotranspiration, where plants release water to the surrounding air, dissipating ambient heat. Meanwhile, urban geometry, with its obstructive structures, traps heat at night. Additionally, urban surfaces absorb and store more heat compared to natural ground cover, raising temperatures further. Understanding these factors helps us create cooler and more sustainable cities.
Thermal satellite images reveal cities’ thermal profiles, areas that experience warmer and cooler temperatures based on the local landscape. The difference parks make in cities’ temperature shows the critical balance between urban development and green spaces, which help mitigate high temperatures. Even small green spaces can make a difference. In Greece, city planners in Athens have created “pocket parks”, transforming small plots once ridden with garbage and weeds.
“It’s about creating green spaces, lowering the temperatures, giving quality of life and creating new reference points inside the city,” Athens Mayor Kostas Bakoyannis said.
Source: CNA
