News Archive

Floods set to become more common due to climate change

Release Date 26 November 2012

Following devastating flooding across the UK, experts from the University of Reading offer their comment.

Professor Nigel Arnell, Walker Institute, University of Reading said:

"The floods this week have been caused not only by the heavy rain of the last few days, but also by the large amounts of rain that fell over the summer and autumn. Soils have been saturated now for a few weeks in many areas and any extra rain is likely to trigger flooding.

"There is a clear trend in the UK towards more heavy precipitation events over the last 50 years (in fact this trend is common over many areas of the world). This is consistent with what we would expect in a warming world and is consistent with what climate models predict for the future. Climate models also predict that UK winters may become wetter, leading to more prolonged periods of saturated soils, and increasing still further the risks of flooding. For example, the sort of wet winters we currently see over Northern Europe just once every 20 years could happen almost every other year by the end of the century.

"There's also growing evidence that human induced climate change is already increasing the chances of UK floods and other extreme events. For example, studies have shown that human induced climate change made the devastating floods of autumn 2000, the wettest autumn on record in England and Wales, between two and three times more likely to happen.

"When you look back at seasonal rainfall for the UK over the last 100 years, there is some suggestion of an increase in winter rainfall and a decrease in summer rainfall, but there is also a lot of year to year and decade to decade variability. The last few summers have been wet over the UK. Whether this is an indication of how climate change might affect summer rainfall is too early to say, but it does emphasise the volatility of our climate.

"It is hard to study trends in floods themselves as they are affected by a whole range of factors, not just the amount of rain that falls: for example, changes to flood defences and changes in the amount of impermeable land surface can all affect floods and their impacts.

"The wettest year on record for England and Wales is 1872 with 1284.9 mm of rain; currently 2012 has had 931.4 mm (source: UK Met Office England and Wales rainfall series which began in 1766)."

Dr David Lavers, Walker Institute, University of Reading said:

"Over the last several days the jet stream, a ribbon of fast moving air around 8-10 km up in the atmosphere,  has been located further south than normal and has brought a series of storms to the British Isles. The weekend saw a long-lasting low pressure system over the UK.

"Flood-generating rainfall in the UK has been linked by scientists at the University of Reading to "Atmospheric Rivers", narrow bands of atmospheric moisture, thousands of kilometres long, that are transported by the wind. The recent succession of storms has transported moisture from the subtropical North Atlantic Ocean towards the UK, some in the form of atmospheric rivers, and this has fuelled large rainfall totals and widespread flooding."

ENDS

For all media enquiries please contact Donna Sibley, University of Reading Press Officer on 0118 378 7388 or by email on d.l.sibley@reading.ac.uk

Follow us on Twitter | Like us on Facebook | Read our research blog 'The Forum'

Notes for editors:

The University of Reading's Walker Institute for Climate System Research aims to enhance understanding and improve prediction of the risks and opportunities from our changing climate. The Institute brings together the unrivalled breadth and depth of climate expertise that exists within the University of Reading.

Additional Facts and figures

November 2012 rainfall in Reading, Berkshire  - some facts and figures

• Total rainfall up to 9 a.m. on Monday 26th amounted to 75 mm of rain, which represents only a little more than the November average fall of 66 mm.
• Over the past weekend 15mm fell in the 24 hours ending 9 a.m. on Sunday (25th) and 9 mm in the 24 hours ending 9 a.m. on Monday (26th).
• The rainfall recorded in Reading during 2012 so far totals 700 mm. This is about 10% more than the total rainfall expected each year of 635 mm - and makes it the wettest year since 2008 with about five weeks still to go.
• However, during the past 100 years the wettest calendar years in Reading have been in 1951 (when 896 mm fell), 1927 (858 mm), 2000 (852 mm) and 1924 (811 mm).
• After beginning the year with drought conditions (only 72 mm of rain fell during the first three months of the year), rainfall amounts in Reading during 2012 have varied a lot from month to month.
• October 2012 brought 128 mm of rain - the wettest month of the year so far - and after rather a wet summer the recent rains of November have maintained a saturated near-surface soil layer.
• However, the 198 mm of rain that has fallen in October and November combined is still a little way short of the 256 mm that fell in the same months in 2006 at the University. Even wetter was the same period in 2000 when 267 mm fell.
• Fortunately, East Berkshire seems to have missed the worst of the rains that have fallen not too far to the west and north. See http://www.met.reading.ac.uk/~brugge/sumr.jpg for rainfall totals across the British Isles so far this month; this webpage is updated every 12 hours.
• Observations of rainfall at the University of Reading are made by Mike Stroud and colleagues in the Department of Meteorology.

Figures provided by Dr Roger Brugge, Department of Meteorology, University of Reading.