Diesel cars emit more air pollution on hot days, study says

Emissions rose 20-30% in Paris when temperatures topped 30C, raising urgent questions as the climate gets hotter

Emissions from diesel cars - even newer and supposedly cleaner models - increase on hot days, a new study has found, raising questions over how cities suffering from air pollution can deal with urban heat islands and the climate crisis.

Research in Paris by The Real Urban Emissions (True) initiative found that diesel car emissions of nitrogen oxides (NOx) rose by 20% to 30% when temperatures topped 30C - a common event this summer.