The unprecedented 40 degrees Celsius heatwave that hit the UK last week was at least 10 times more likely because of climate change, according to a new study. The team of researchers from the World Weather Attribution (WWA) also found that the extreme weather event would have been 2 degrees Celsius cooler without global warming.

The study wasn’t published in a peer-reviewed scientific journal yet but follows scientifically accepted techniques. The researchers regularly keep track of extreme weather events, from droughts to heatwaves, and publish reports on the climate connection, as they recently did with a recent typhoon in Japan and a heatwave in India.

The team at WWA found that the heatwave that set a new national record high of 40.3 degrees Celsius (104.5 degrees Fahrenheit) was made stronger and more likely because of the accumulation of warming gases in the atmosphere. The record, set in Lincolnshire, should only happen in that area every 1500 years in normal conditions the researchers said.

“We know it’s still a rare event today. It would have been an extremely unlikely event without climate change,” Friederike Otto, part of the WWA team, told The Guardian. “In Europe and other parts of the world, we are seeing more record-breaking heatwaves causing extreme temperatures that have become hotter faster than in most climate models.”

An extreme weather event

The researchers focused on the two hottest days, July 18th and 19th, over an area stretching across east Wales and parts of England, including London. Then they modeled a world without and with climate change since the industrial revolution, looking at maximum temperature for one day and average temperature across two days.

The analysis showed that the two-day heat that happened across the entire studied area would occur about once every 100 years in today’s warmer world. But the temperature would have been “extremely unlikely” without the 1.1°C of global warming, triggered by the burning of fossil fuels and other human activities. The more the temperature continues to rise, the likelier such events become.

The heatwave disrupted rail transportation, caused schools to close, and triggered destructive wildfires, with 948 people estimated to have died over three days in the UK because of the heat. A total of 46 weather stations across the country met or broke the previous temperature record of 38.7°C, set in 2019. The heat came amid the driest January-June period in England since 1976.

“Heatwaves during the height of summer pose a substantial risk to human health and are potentially lethal. This risk is aggravated by climate change, but also by other factors such as an ageing population,” the researchers wrote in their paper. “Effective heat emergency plans are becoming even more important in light of the rising risks.”

The paper can be accessed here.