Last week's record-breaking heatwave in Britain was made at least 10 times more likely by human-caused climate change, a new study by a team of international scientists has found.
The UK’s extreme temperatures were higher than climate models predict — suggesting the consequences of climate change for heatwaves could be even worse than previously thought, the scientists warned.
Researchers from the World Weather Attribution initiative said the 10-fold increase in the chances of extreme heat in the UK due to climate change is a conservative estimate.
And while the searing heat, which led to temperatures peaking above 40ºC for the first time in the UK, 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 UK heatwave.
“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.”
A record temperature for the UK of 40.3ºC was set in Coningsby, Lincolnshire, on July 19 — 1.6°C hotter than the previous record set only three years ago.
The heat caused widespread disruption to transport networks and hundreds of fires, including devastating blazes that destroyed homes and pushed London to the brink of power cuts. Scorching temperatures 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 Meteorological Office’s first red alert warning for extreme heat issued for July 18-19.
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 4ºC.
Researchers used computer modelling to compare the likelihood of the temperatures recorded in the heatwave under the current climate with a world without the 1.2ºC of global warming since the 19th century.
The modelling suggests climate change, driven by more heat-trapping greenhouse gases put into the atmosphere by human activity, had made a heatwave as intense as the UK’s at least 10 times more likely and probably even more. However, the research said this was still likely to happen only once in 100 years.
“Two years ago, scientists at the UK Met Office found the chance of seeing 40ºC in the UK was now one in 100 in any given year, up from one in 1,000 in the natural climate," said Fraser Lott, climate monitoring and attribution scientist at the Met Office Hadley Centre.
“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 heatwave by 2ºC, analysis of historical weather records indicate it would be about 4ºC cooler in pre-industrial times. This is before global warming started to drive up temperatures.
"In Europe and other parts of the world, we are seeing more and more record-breaking heatwaves causing extreme temperatures that have become hotter faster than in most climate models," said Friederike Otto, from the Grantham Institute for Climate Change, Imperial College London.
“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 heatwave, 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. Urban areas such as London have had extra high levels of heat being trapped by the city.
There are also significant inequalities that worsen the situation, with poorer neighbourhoods in cities such as London lacking green space, shade, and water which can help people cope during heatwaves.
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. These in turn exacerbate heatwaves because there is less water in the environment to absorb heat as it evaporates.
