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The quiet work of cooler streets

Cities are often several degrees warmer than the surrounding countryside. Researchers call this the urban heat island effect, and its causes are ordinary: dark surfaces absorb sunlight, buildings slow the movement of air, and a shortage of trees removes shade and evaporation.

Recent projects have focused on small, repeatable interventions rather than a single grand redesign. A row of trees beside a footpath can make a route more comfortable. Reflective roofs can reduce the heat stored by a building. These changes seem modest, but their value grows when they are joined across a neighbourhood.