“Painting London White: How Rooftops Could Cool the City by 3.6 Degrees Fahrenheit”

A new study has found that painting London’s rooftops white could potentially reduce the outdoor temperature of the city by up to 3.6 degrees Fahrenheit (2 degrees Celsius). The research, conducted by scientists at University College London, aimed to identify effective ways to cool the U.K. capital in response to the expected hotter and drier summers due to climate change.

Lead author Oscar Brousse, a lecturer specializing in urban meteorology and environmental modeling, stated that after testing multiple methods, they found that cool roofs were the most effective way to combat extreme heat during hot summer days. The study, published in the journal Geophysical Research Letters, examined various strategies such as adding rooftop solar panels, covering roofs with reflective coatings, planting vegetation, and deploying air conditioning on a large scale.

The researchers created a 3D computer model of London and ran simulations using different cooling techniques on the two hottest days of summer in 2018 when temperatures reached 95 degrees F (35 C). The results showed that cool roofs, when widely adopted, reduced outdoor temperatures by an average of 2 F (1.2 C) and up to 3.6 F in certain areas. Street vegetation and solar panels had a smaller impact, while green roofs had negligible effects. Surprisingly, air conditioning, while effective in cooling dwellings, actually warmed the outdoor temperature by up to 1.8 F (1 C) in central London.

Despite the promising results, the study had limitations, such as focusing solely on outdoor temperatures and not considering the costs and benefits of other interventions like increased biodiversity and lower indoor temperatures. However, the researchers believe their findings provide valuable insights into which interventions can have the greatest cooling effect in London during hot summer days.

As cities like London face the challenges of urban heat islands, where built environments absorb and retain heat, innovative solutions like painting rooftops white could play a crucial role in mitigating the impacts of climate change and creating more sustainable urban environments.