The record-shattering human-caused heat wave that scorched the United Kingdom last week was made 10 times more likely, according to a study by a team of international scientists who also warned that the U.K.'s extreme temperatures were higher than climate models predict – suggesting the consequences of climate change for heat waves could be even worse than previously thought.

The 10-fold increase in the chances of such extreme heat in the U.K. due to climate change is a conservative estimate, the researchers from the World Weather Attribution initiative said.

And while the searing heat, which saw temperatures peak above 40 degrees Celsius (104 degrees Fahrenheit) for the first time in the U.K., is still a very rare occurrence in today's climate, it would be "almost impossible" without global warming.

Mariam Zachariah, from the Grantham Institute for Climate Change, Imperial College London, said: "Even with a conservative estimate, we see a large role of climate change in the U.K. heat wave.

"Under our current climate that has been altered by greenhouse gas emissions, many people are experiencing events during their lifetime that would have been almost impossible otherwise."

Much of the U.K. sweltered in the heat wave, with a new record temperature for the country of 40.3 degrees Celsius set at Coningsby, Lincolnshire, 1.6 degrees Celsius hotter than the previous record set just three years ago.

The heat caused widespread disruption to transport networks and hundreds of fires, including devastating blazes that destroyed homes, pushed London to the brink of blackouts and are expected to have caused hundreds of deaths.

The study looked at the annual maximum temperatures over two days across the region of England and east Wales, which had the Met Office's first-ever red alert warning for extreme heat issued for July 18 and 19.

It also examined the change in frequency and intensity of the maximum daily temperature seen at three locations: London's St James's Park, Cranwell in Lincolnshire, which is close to Coningsby, and Durham, where temperatures broke their previous record high by 4 degrees Celsius.

Researchers used computer modeling to compare the likelihood of the temperatures seen in the 2022 heat wave under the current climate and in a world without the 1.2 degrees Celsius of global warming seen since the 19th century.

The modeling suggests climate change, driven by more heat-trapping greenhouse gases put into the atmosphere by human activity, had made a heat wave as intense as the U.K.'s at least 10 times more likely and probably even more – though still only likely to happen once in 100 years.

Fraser Lott, climate monitoring and attribution scientist at the Met Office Hadley Centre, said: "Two years ago, scientists at the U.K. Met Office found the chance of seeing 40 degrees Celsius in the U.K. was now one in 100 in any given year, up from one in 1,000 in the natural climate.

"It's been sobering to see such an event happen so soon after that study, to see the raw data coming back from our weather stations." But the researchers also warned extreme heat in western Europe is rising faster than climate models predict.

While the models suggest climate change had increased temperatures in the heat wave by 2 degrees Celsius, analysis of historical weather records indicates it would be around 4 degrees Celsius cooler in pre-industrial times, before global warming started to drive up temperatures.

Friederike Otto, from the Grantham Institute for Climate Change, Imperial College London, said: "In Europe and other parts of the world, we are seeing more and more record-breaking heat waves causing extreme temperatures that have become hotter faster than in most climate models.

"It's a worrying finding that suggests that if carbon emissions are not rapidly cut, the consequences of climate change on extreme heat in Europe, which already is extremely deadly, could be even worse than we previously thought."

While it will take weeks for figures for the number of extra deaths seen during the heat wave, there have been estimates of more than 840 more people dying in England and Wales on July 18 and 19.

The researchers warn older people, those with chronic health conditions and children are particularly vulnerable to extreme heat, with urban areas such as London seeing extra high levels of heat being trapped by the city.

Significant inequalities also worsen the situation, with poorer neighborhoods in cities such as London lacking green space, shade, and water which can help people cope during heat waves.

Climate change has increased average global and regional temperatures, which means natural spikes in heat are driven higher and occur more frequently.

It can also contribute to drier conditions and soils, which have been seen in much of Europe this year, exacerbating heat waves because there is less water in the environment to absorb heat as it evaporates.