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.

Researchers said they believe that human-driven climate change probably intensified the recent European heat wave and increased the number of heat-related deaths.

The rapid analysis by World Weather Attribution calculated that climate change might have tripled the death toll from the event.