Climate crisis to bring more intense rain and thunderstorms to the UK, experts warn

As the planet heats up due to increasing levels of human-made emissions, one aspect of the worsening climate crisis could be to intensify rain and thunderstorms, experts have said.

New research by scientists at Newcastle University suggests rising temperatures in some parts of the UK are the main drivers of increases in “extreme short-duration rainfall intensities”.

These storms tend to happen during the summer months and can cause dangerous flash flooding.

The intensity of summer storms is growing at a “significantly” faster rate than for winter storms, the research team said.

Professor Hayley Fowler, of Newcastle University’s School of Engineering, said there is an urgent need to put in place “climate change adaptation measures” as heavier short-term rainfall increases the risk of flash flooding and extreme rainfall.

The international team of researchers analysed data from observational, theoretical and modelling studies to examine the intensification of rainfall extremes, as well as looking at what drives these extremes and their impact on flash flooding.

The scientists found that maximum rainfall levels go up as the environment warms, generally at a rate consistent with increasing atmospheric moisture - this was a trend the team expected to see.

What was more puzzling was that the study also indicated that temperature increases in some regions affect short-duration heavy rainfall extremes more than the increase in atmospheric moisture alone.

The team said local feedback loops due to convective cloud systems - in which warm moist air rises to form clouds, which then rain, form part of the answer to this puzzle.

Professor Fowler said: “We know that climate change is bringing us hotter, drier summers and warmer, wetter winters. But, in the past, we have struggled to capture the detail in extreme rainfall events as these can be highly localised and occur in a matter of hours or even minutes.

“Thanks to our new research, we now know more about how really heavy rainfall might be affected by climate change. Because warmer air holds more moisture, rainfall intensity increases as temperatures rise.

"This new work shows that the increase in intensity is even greater for short and heavy events, meaning localised flash flooding is likely to be a more prominent feature of our future climate."

It is unclear whether storm size will increase or decrease with warming, but the researchers warn that increases in rainfall intensity and the footprint of a storm can combine to substantially increase the total rainfall during an event, posing unique hazards.

In recent years, short but significantly heavy rainfall events have caused much disruption across the UK. Recent examples include severe flooding and landslides in August 2020 and damage to the Toddbrook Reservoir, in the Peak District, in August 2019.

The scientists said having detailed data on current and future rainfall intensity is critical for the management of surface water flooding, as well as our guidance for surface water management on new developments and sewer design.

The research is published in the journal Nature Reviews Earth & Environment.