A blaze in southern France forced the closure of the Marseille airport, and weather agencies issued warnings for other parts of Europe where temperatures were expected to climb this week.

Scientists at Imperial and the London School of Hygiene and Tropical Medicine used peer-reviewed techniques to calculate that about 2,300 people in 12 cities likely died from the heat in last week’s bout of high temperatures, with nearly two-thirds of them dying because of the extra degrees that climate change added to the natural summer warmth.