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.

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.