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Heavier Summer downpours with climate change?

Heavier, more intense summer rainfall may become more frequent Photo: Warrington TONY MARSH

The Met Office released findings this weekend, as part of a joint project with Newcastle University, that extreme summer rainfall may become more frequent in the UK due to climate change - with hourly downpours becoming five times more 'eventful' than the current climate.

The project was so computer intensive that it took the Met Office supercomputer – one of the most powerful in the world – about nine months to run the simulations.

Overall our Summers are expected to become drier by the year 2100, but it's the intense downpours that are associated with Summer (and indicative with flash flooding) that are expected to become much more frequent over the coming years.

As the atmosphere warms it will be able to hold more moisture, and therefore we'd expect more rain - but it's the type of rainfall that this new model can forecast which makes it different.

Current computer models are well practiced in forecasting larger rainfall areas associated with Winter months but, until now, climate models have lacked the resolution to accurately simulate the smaller-scale convective storms which cause heavier (short and intense) rain which occurs in Summer.

With heavier more intense rainfall comes the increased risk of flooding - and therefore a greater impact on society. The results from the study are the first step towards building a more complete picture of how UK rainfall may change as our climate warms. According to the lead author of the research at the Met Office, Dr Lizzie Kendon, the project findings will now allow the Met Office to "make future predictions with much greater confidence".

We have to remember that this is just one project using one computer model. Greater and more wider research is needed to get a fuller picture of the global implications. Prof Hayley Fowler, from the School of Civil Engineering and Geosciences a Newcastle University, who lead the project suggests..

“The next steps are to see if these changes are consistent with observed trends in summer rainfall extremes and changes projected by climate models in other parts of the world. We will be looking at this over the next five years”.

– Prof Hayley Fowler

(The study is from the joint Met Office and NERC funded CONVEX project.)

(Results from the study have been published in Nature Climate Change.)