Cooling Towns Down: Green Areas around Cities

Already in 1960’s Lovin’ Spoonful sang “…hot town, summer in the city.” Indeed, towns are much hotter than the countryside around. Asphalt and concrete, streets and buildings without trees and green areas form heat domes where temperatures increase whenever sun shines. Since an increasing percentage of people live in cities, increasing temperatures have become a major health issue with climate change.

A within town solution to decrease temperatures in the cities is to plant trees to line streets and include a lot of parks in the areas. The effects of trees on the street temperatures has been estimated, and the difference between “bare” and tree-lined streets can be 5-10 degrees centigrade. Another way of decreasing city temperature is to use reflective materials/paints on rooftops. Any colours used should be light to reflect as much solar radiation as possible.

Although the above ways can decrease city temperatures to some degree, the presence of many streets and buildings necessarily increases city temperatures above those of woodlands. However, if a city is surrounded by woodlands, the following occurs:

1. Since the city temperature increases, the warm air tends to rise upwards generating a low-pressure zone in the city.
2. The cooler air flows from the surrounding woodlands to the city, whereby the measured temperature decreases and, further, the moving air, i.e. wind, makes the temperature feel more tolerable than without wind.

The influence of green areas surrounding towns on their temperatures has been reported by Yang et al in Nature Cities (2024; https://doi.org/10.1038/s44284-024-00091-z).