The UK’s extreme heatwave would have been ‘virtually impossible’ without climate change

Climate change made the record-smashing heatwave in the UK last week at least 10 times more likely, new research has found. The analysis was published yesterday by the World Weather Attribution initiative, a collaboration of scientists from universities and research institutes around the globe.

“In a climate unaffected by human-induced climate change, it would be virtually impossible for temperatures in the UK to reach 40°C but climate change is already making UK heatwaves more frequent, intense and long-lasting,” Mark McCarthy, science manager of the National Climate Information Centre, said in a Met Office press release.

The Met Office declared, for the first time, a “Red” heat warning for “exceptional heat” in parts of England for July 18th and 19th. And the Health Security Agency issued its highest alert for heat health, saying “illness and death may occur among the fit and healthy, and not just in high-risk groups.”

Temperatures reached a scorching 40.3 degrees Celsius on July 19th in Coningsby, Lincolnshire, about 225km (140 miles) north of London, setting a new record. The UK’s previous temperature record of 38.7 degrees Celsius was set in 2019 — and that was either met or broken at 46 different weather stations throughout the UK last week.

The heat was devastating for communities accustomed to much milder temperatures. Last week’s oppressive heat mangled infrastructure — buckling train tracks, roads, and an airport runway. The fire service in London responded to more fires in a day than it had since World War II as hot, dry conditions set the stage for blazes. Authorities are still taking stock of heat-related deaths, but one early analysis estimates that 948 people may have died as a result of the heat in England and Wales from July 17th to 19th.

Temperatures reaching 40 degrees Celsius in the UK would have been “extremely unlikely,” the World Weather Attribution initiative says, “without human-caused climate change.” Normally, London’s average high temperature is around 23 degrees Celsius (74 degrees Fahrenheit) this time of year. Even with global warming, last week’s ridiculous temperatures are an outlier for those regions under red alert: they are only likely to occur once every 1,000 years, according to the researchers. That figure can vary from locale to locale — but it still shows how extreme the heat was.

To conduct their analysis, the scientists looked at both historical observations and climate models, focusing on the regions under the red heat warning. Both methods came to the same conclusion: the climate crisis made the UK’s extreme heatwave at least 10 times more likely.

They did notice, however, that the effects of climate change looked more severe in the real-world data than in the climate models. The researchers’ observational data analysis found that last week’s heatwave would have been 4 degrees Celsius cooler in preindustrial times — without the greenhouse gas emissions giving the planet a fever. Climate models, in contrast, found that temperatures would have been 2 degrees Celsius lower without global warming. That raises the question of whether the future could be even more disastrously hot than we’re already anticipating.