Flash flooding similar to that which devastated Boscastle a decade ago could become the norm as climate change takes place according to experts.
The new study, conducted by the Met Office and Newcastle University, reveals that the UK could experience a fivefold increase in bouts of intense rainfall if global temperatures continue to rise.
Researchers said this could in turn increase the country’s risks of flash floods, citing the Boscastle flood of 2004 and the flooding in Newcastle in 2012 as examples.
Dr Elizabeth Kendon, lead author of the study, said: “Until now, climate models haven't been able to simulate how extreme hourly rainfall might change in future. The very high resolution model used in this study allows us to examine these changes for the first time.
“It shows heavier summer downpours in the future, with almost five times more events exceeding 28mm in one hour in the future than in the current climate - changes we might expect theoretically as the world warms.”
The findings, published in the Nature and Climate Change journal, are based on weather simulations run for current climate conditions and the expected climate for 2100.
In Boscastle almost 8 ins (200mm) of rain fell in four hours in August 2004 causing a massive wall of water to sweep through the village and washing cars away.
Climate models have already been used to predict future changes to rainfall in Britain but the new report is the first to use hourly rainfall rates and has achieved greater clarity through smaller grid spacing in its simulations - 1.5km grid spacings instead of the normal 12km.
Researchers have said this “higher resolution” study could be the first step towards building a more complete picture of how UK weather may change as our climate warms.
Dr Kendon said the predicted increase means significantly more events would exceed the high thresholds indicative of serious flash flooding.
“This implies that previous interpretations of future regional climate change scenarios should be revisited, as changes in rain events could have been underestimated,” she said.
The Met Office study only focussed on the southern half of the country because the calculations were so computer intensive. It took the organisations’s supercomputer - one of the most powerful in the world - around nine months to complete the simulations.
Dr Kendon warned of the need to be careful when looking at the result.
“It is only based on one model,” she said. “We need to wait for other centres to run similarly detailed simulations to see whether their results support these findings.”
Professor Hayley Fowler, a co-author on the project from Newcastle University, said the team will be continuing their research over the next five years.
“We need to understand about possible changes to summer and winter rainfall so we can make informed decisions about how to manage these very different flooding risks in the future.”