Lisbon: The colour of cars could play a bigger role in urban heat than previously thought, with dark-coloured vehicles shown to intensify local air temperatures and contribute to heat stress in cities, according to new research cited by News Scientist.

Scientists at the University of Lisbon found that black cars parked in the sun can raise the surrounding air temperature by up to 3.8°C compared with nearby asphalt on hot summer days. White cars, by contrast, had a much smaller effect.

“You know when you walk past a parked car on a hot day and feel the heat radiating off it? That’s real, it’s not your imagination,” said lead researcher Márcia Matias to News Scientist.

The difference comes down to reflectivity. White car paint reflects 75 to 85 per cent of incoming sunlight, while black paint reflects only 5 to 10 per cent, absorbing most of the energy instead. Thin car bodies made of steel or aluminium also heat up more quickly than thick asphalt, allowing them to release more heat into the air.

“When you imagine thousands of cars parked across a city, each one becomes a little heat source or shield,” Matias said. “Their colour can actually shift how hot the streets feel.”

The team calculated that repainting dark-coloured cars to lighter shades could help cool urban areas. In Lisbon, where parked cars cover more than 10 per cent of some streets, such a change could raise overall street-level reflectance from about 20 per cent to nearly 40 per cent on clear, still days,reducing the intensity of urban heat islands.