We know how a city is boiled: the saturation of materials that absorb solar radiation—steel, asphalt, and concrete—perpetuates sustained temperature spikes that trigger air conditioning deployment and multiply heat. A more important question is: how does it cool? Three Bloomberg journalists combined public imagery from the European Space Agency with open data from NASA and the United States Geological Survey to create a thermal map of the cities hardest hit by the heatwave. From London to Los Angeles, past Melbourne, Seville and Mumbai, they found everyone’s most passionate spots. Then they looked for the coldest ones to find out where they are and why.
What we already know: The most efficient technology we have against heat is the tree. A local park drops the temperature between two and six degrees; a row of trees can cool the road surface by up to 12°. The great concentrations of water, rivers, canals and lakes have the same effect: the neighborhoods touching the Guadalquivir and Alfonso XIII Canal are the coolest in Seville. Then there are the materials. Los Angeles, one of the hottest cities in the world, is covering roofs and streets in reflective material to cool buildings and reduce air conditioning use. In addition to heat, it triggers energy demand, increases electricity bills, pollution, and emissions.
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The third tool is the neighbors. If Madrid is destined for Morocco’s climate, consider that Arabs have been living with extreme heat for hundreds of years. In Fez’s medina, the most “European” neighborhoods spit fire with cobbled streets and modern buildings, while the streets around Plaza Seffarine remain eight degrees below average despite having the highest population density. Three factors come together here: low-rise brick buildings, narrow, winding streets that offer permanent shade, and unpaved cobblestone or cobblestone streets. “It helps make the soil more permeable and the environment more humid, an advantage in the hot, dry air of the desert.”
Melbourne installs permeable asphalt that can absorb water to nourish tree roots and optimize their growth for more shade. London plans to reforest half of its area by 2050. Seville continues its heat storage project in Qanats [canalizaciones subterráneas para captar agua]. Knowing all this, we have to talk about Madrid.
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