A new study suggests that implementing cool roofs in London during the exceptionally hot summer of 2018 could have saved up to 249 lives.
The research, published in Nature Cities, examined how roofs painted white or other reflective colors could have reduced the city’s temperatures from June to August 2018, which was the hottest summer London had experienced. During this time, the average temperature in London reached 19.2 degrees Celsius, roughly 1.6 degrees higher than typical for those months.
Cities tend to trap heat, leading to temperatures that are a few degrees warmer than surrounding areas. This phenomenon is called the ‘urban heat island’ effect. Light-colored, reflective roofs would absorb less heat from sunlight compared to traditional dark roofs, thereby cooling down the urban environment.
The study indicated that if London had widely implemented cool roofs, the city’s average temperature could have decreased by approximately 0.8 degrees Celsius. This change could have potentially prevented about 249 heat-related fatalities, which constitutes around 32% of the 786 heat-related deaths recorded during that summer.
Additonally, the researchers noted that if rooftop solar panels had also been broadly installed, they could have contributed to cooling the city by around 0.3 degrees Celsius, possibly preventing 96 heat-related deaths—about 12% of the total for that season.
Using a sophisticated 3D computer model, the researchers simulated various urban settings to analyze temperature trends during the hot summer of 2018 (validated against actual temperature data). They explored the temperature differences if all roofs in London were coated with reflective paint or covered with solar panels, and compared those scenarios to a theoretical scenario of a non-urbanized London.
The researchers also calculated the economic impact of the increased mortality in both scenarios. The 96 lives saved through solar panel implementation could have alleviated an economic burden of around £237 million, while the 249 lives saved by adopting cool roofs could have reduced burdens by about £615 million.
Furthermore, if solar panels had been widely deployed during the three-month period, the researchers estimated that up to 20 terawatt-hours (TWh) of electricity could have been generated, which exceeds half of London’s total energy consumption for the entire year of 2018.
Dr. Charles Simpson, the study’s lead author from UCL’s Bartlett School for Environment, Energy & Resources, stated, “Widespread adoption of cool roofs can significantly lower ground-level temperatures in urban areas. This decrease would not only save lives but also enhance the quality of life for city residents. Additionally, solar panels represent a sustainable energy source and don’t contribute to overheating the city.”
Addressing urban heat is becoming increasingly urgent as global temperatures continue to rise due to climate change. While summers like 2018 were once relatively rare, they are expected to occur more often in the future. The UK, with approximately 83% of its population living in urban areas, is especially vulnerable to these heat effects.
Dr. Simpson further remarked, “As climate change effects intensify, urban populations will need innovative solutions for adaptation. Our findings show that installing cool roofs offers a viable strategy to counteract the heat retention typical in cities.”
Co-author Professor Tim Taylor from the University of Exeter emphasized, “It is evident that our cities must adapt to climate change. Modifying our roofs is a practical solution that could help lessen the impact of extreme heat on urban dwellers while also harnessing benefits like energy generation.”
Recent preliminary findings from the research team indicated that during the three hottest days of 2018, widespread use of cool roofs could have reduced the city’s average temperature by about 1.2 degrees Celsius, whereas rooftop solar panels could have led to a reduction of about 0.3 degrees Celsius. This study broadens those earlier models to cover the entire summer of 2018, which remains London’s hottest summer recorded.
This research was part of the HEROIC: Health and Economic impacts of Reducing Overheating in Cities project, supported by UCL and Exeter, with funding from Wellcome Trust and NERC.
