Searing temperatures of 32C this week have been made 100 times more likely because of human-caused climate change, scientists said.
A rapid study by the World Weather Attribution (WWA) research group also found the current heatwave in the south-east of England was around 10 times more likely than without human activity warming the planet.
Dr Fredi Otto, from Imperial College London, warned heatwaves are “silent killers”, with the impacts of heat “severely underestimated” and the UK unprepared for the kind of conditions hitting the country into the weekend.
Older people are at the highest risk of death, as well as those with heart issues, respiratory illnesses and conditions such as diabetes, while this kind of heatwave earlier in the summer is more deadly as people are less acclimatised to coping with the warmer conditions, the experts warned.
And wildfires are an “emerging risk” in the summer in the UK, with conditions becoming more like southern Europe, the researchers said as they urged people to be very careful about barbecues, cigarettes and glass which can all ignite fires in the hot, dry weather.
The study by WWA, which seeks to provide rapid assessments of the role of climate change in specific extreme weather events such as heatwaves or rainstorms that lead to flooding, is only the second time it has analysed an event as forecasted rather than one that has just happened.
The analysis, which drew on observations for early summer heat in the south east of the UK, found that a heatwave – defined as three days of temperatures above 28C for the region – in June would be expected once every five years today.
But without humans warming the atmosphere by around 1.3C since pre-industrial times, such a heatwave would only have occurred about once every 50 years, the study shows.
The heatwave was made approximately 2-4C more intense as a result of the overall warming of the planet, meaning the current weather “just wouldn’t have been a heatwave without human-induced warming”, Dr Ben Clarke, from Imperial College London, said.
Temperatures had been forecast to hit 32C across the south east on Saturday and had already reached that level on Thursday in London.
Heat of that level could be expected in June once in 25 years in the current climate, but only once in 2,500 years in June before industrialisation, the researchers said.
While the impacts of temperatures rising above 30C are not as severe as the record-breaking heat topping 40C in some places in July 2022, the researchers warned people were still at risk.
They urged people to ensure they were drinking enough water, and to encourage elderly relatives to do the same, avoid areas with high air pollution, keep windows and curtains shut during the day, and consider going to cooler public buildings such as museums to protect against the heat.
Dr Clarke, researcher at the Centre for Environmental Policy at Imperial College London, said: “This heatwave is another reminder that our planet has already heated to a dangerous level.
“We’re at 1.3C today, but heading for around 3C this century.
“With every fraction of a degree of warming, the UK will experience hotter, more dangerous heatwaves.
“That means more heat deaths, more pressure on the NHS, more transport disruptions, tougher work conditions and poorer air quality.”
Dr Otto, associate professor in climate science at the Centre for Environmental Policy, said: “We know exactly what has intensified this heatwave – burning oil, gas and coal, which has loaded the atmosphere with planet-heating greenhouse gases.
“It is totally insane we have political leaders in the UK trying to drag us back to the past with calls for more fossil fuels.
“The climate will continue to drive increasingly dangerous heatwaves, fires and floods in the UK until emissions are reduced to net zero globally.”
She added that while people working in air conditioned offices would “probably be OK” this week, poorer people working outdoors, in kitchens or other hot environments and then returning home to poorly insulated flats would be enduring hot conditions throughout.
“Making our societies more equal is essential to reduce the impacts of climate change,” Dr Otto said.
