Highest alert level for the Great Barrier Reef | FAZ climate blog

Fighting the heat with cooling roofs: Even in our latitudes, the urban climate can become unbearable during the summer months, when heat waves drive up temperatures in densely built-up inner cities. Researchers from University College London have now discovered an easy way to lower temperatures in cities: paint roofs white.

For their analysis, the researchers led by skin author Oscar Brousse used a three-dimensional model of the Greater London area to model hourly temperature profiles during the two hottest days of the July 2018 heatwave. At that time, the United Kingdom experienced the warmest summer since 1910. In London, temperatures rose to over 32 degrees on July 26.

In a total of eleven simulation runs, the scientists compared how the widespread use of various measures to mitigate heat stress affected the urban climate. More street greenery, for example, reduced temperatures in the models by an average of about 0.3 degreesHowever, more deciduous trees on the streets or bushes on the roofs would further increase the humidity, as plants only cool their surroundings by evaporating water.

However, if every roof in London was equipped with solar cells in the simulations, the temperature would drop by around 0.5 degrees. According to the calculations, the solar cells could then generate enough electricity to run air conditioning systems across the greater London area. However, air conditioning systems contribute to an increase in the outside temperature because the systems transport the heat from the interior to the outside. With widespread use of air conditioning, outside temperatures rose by an average of 0.2 degrees, and in densely built-up central London by as much as 1 degree.

So-called cooling roofs, on the other hand, which reflect solar radiation instead of absorbing it, have the double advantage of not only cooling the surroundings but also the interior of the buildings. “We have tested several methods that cities like London could use to adapt to and mitigate warming,” says Brousse. “Cooling roofs are the best way to reduce temperatures on hot summer days.”