July 24, 2017

expert reaction to Met Office study modelling risk of unprecedented rainfall in the current climate

A new modelling study published in Nature Communications reports that there is a 1 in 3 chance of a new monthly rainfall record in at least one region each winter (Oct-Mar).

Prof. Len Shaffrey, Professor of Climate Science, National Centre for Atmospheric Science, University of Reading, said:

“The new Met Office study provides some really interesting insights into the probability of extreme rainfall events such as the winter of 2013/14 and how risks might be changing due to climate change. Using weather and climate models to better understand the probability of extreme weather is an important method that is becoming more widely used to help inform those dealing with weather impacts about the risks of extreme events.

“Future research needs to evaluate how well weather and climate models are able to accurately simulate other extreme weather events, for example droughts and heat waves, if we want to use models to better understand extreme weather risks and how they might be changing.”

Prof. Richard Allan, Department of Meteorology, University of Reading, said:

“Using serious number crunching power, the new study plays back thousands of possible weather patterns that emerge from detailed computer simulations of recent decades, some of which produce more extreme rainfall events than have actually been experienced to date. Exceptional seasonal rainfall in the UK is brought about by a perfect storm of atmospheric ingredients. The computer simulations can represent quite well the weather systems, fronts and atmospheric rivers of moisture which determine sustained and heavy periods of rainfall so are certainly credible.

“The work compliments evidence that warming of climate is already causing extreme rainfall events to intensify. It estimates a high 1 in 3 chance of record monthly rainfall occurring each winter in at least one of four mainly low-lying English regions considered. As the planet continues to warm due to human-caused greenhouse gas emissions, extra moisture in the air will fuel increasingly intense rainfall causing a continued rise in the risk of damaging events into the future.”

Daniel Johns, Head of Adaptation, Committee on Climate Change, said:

“This is important research, and reinforces our call for the Government to prepare for and expect a significant flood event to take place somewhere in the country almost every year. However, it’s worth pointing out that the ‘current’ UK climate the paper refers to is not stable and will continue to change. As we set out in our evidence report for the 2017 UK Climate Change Risk Assessment, rainfall patterns in some UK regions have already intensified, as long predicted by climate models. A warmer atmosphere can hold more moisture, and evidence is mounting that higher seasonal temperatures, and heavier rainfall, are already affecting the UK.”

Prof. Piers Forster, Director of the Priestley International Centre for Climate, University of Leeds, said:

“Your house has flooded but how unprecedented is this and are inadequate flood defences to blame?  Unfortunately, it is difficult to accurately assess risk with a relatively short record of past events.  With typically less than 100 years of data, how can you really tell if a flood is a 1 in 10 year event or a 1 in 1000 year event?

“This paper relies on new simulations of UK weather with the latest Met Office computer to create an augmented reality version of our current record, adding many hundreds of realistic, but pseudo, UK winters to the observational record.  This enables them to generate an accurate statistical model of UK rainfall.  Their results will help guide planners in knowing how high to build flood defences.

“Although this year has been particularly dry, generally our winters are getting wetter and the rainfall heavier, so we are seeing more flooding and records broken.  We expect the odds to shorten on future rainfall extremes but the first stage to predict this is knowing the current odds – and this is what this new paper gives us.

“The press release accurately represents the work.  The work is original but builds on the event attribution techniques developed by the climateprediction.net team at the University of Oxford.”

Dr John King, Science Leader for Atmosphere, Ice and Climate, British Antarctic Survey, said:

“This study highlights just how large natural year-to-year variations in climate can be, even before the effects of human-induced climate change are taken into account.  Quantifying these variations from the relatively short climate records available to us (around 200 years for the UK) has been challenging.

“By using climate model data as a proxy for observations, the Met Office researchers have significantly improved our understanding of the probability of extreme rainfall events.  This forms a sound basis for understanding how the probability of extreme events will change as human activity modifies our climate.”

* ‘High risk of unprecedented UK rainfall in the current climate’ by Vikki Thompson et al. published in Nature Communications at 10:00am UK time on Monday 24 July 2017. 

Declared interests

Prof. Len Shaffrey: “I don’t have any interests to declare.”

Prof. Richard Allan: “No conflicting interests.”

Daniel Johns: “Daniel is a paid employee of the Committee on Climate Change, and a visiting research fellow at LSE’s Grantham Research Institute (unpaid position).”

Prof. Piers Forster: “I have no conflict of interest.”

Dr John King: “Adam Scaife has co-authored papers with members of my science team.”