By Katie Griffiths, Young People’s Programme Assistant at the British Science Association
Just over a year ago today, on 28th June 2012, the skies of Newcastle darkened and the heavens opened. Within 2 hours, 50 mm of rain had fallen, and the streets of Newcastle had flooded with water, leaving many people stranded on their way home from work. In the aftermath of this and other recent floods, experts have been asking: are sudden extreme floods like this on the rise? Today, at the Joseph Lister Award Lecture at the British Science Festival, Dr Hayley Fowler, Professor of Climate Change Impacts at Newcastle University addressed a packed auditorium to try and answer this question.
It turns out that although extreme flood events seem unusual, they aren’t as rare as we might think. If you look back in time, between 1792 and 1901 there were nine recorded extreme flooding events, and even more recently, the worst ever flooding event in Newcastle’s history occurred in 1941, when 95 mm of rain fell in just 85 minutes. As Dr Fowler says, the 2012 flood event is not unusual in the context of the historical record, but we do need to find out whether these flash floods are on the rise. And for the answer, Dr Fowler suggests, we might need to look at rivers in the sky.
Atmospheric rivers are long, narrow, concentrated bands of moisture in the atmosphere that carry more than 200,000 tonnes of water per second. That’s more water than the Amazon river! The high concentration of water in these rivers means that they have the potential to cause very sudden, very heavy rainfall.
So, are these types of events likely to increase in the future? We know that the effects of global warming mean that the atmosphere is heating up, and as a result it can hold more moisture. This means that there is potentially more water available to form atmospheric rivers, and to fall suddenly out of the sky. Current climate models predict that this will cause a significant increase in winter rainfall by the end of the century.
However, these models cannot predict with any accuracy whether there will be any increase in sudden extreme rainfall in summer, like the Newcastle flood last year. To resolve this, Dr Fowler and her colleagues at Newcastle University have developed new high resolution climate models that can predict for the first time the occurrence of sudden summer flooding. Their results indicate that we will see an increase in these extreme rainfall events in the next century.
So, does this mean it’s time to invest in some serious waterproofs, or is there anything we can do to prevent ourselves getting washed away? Dr Fowler ended her lecture by exploring how we might start to better manage and plan for these types of flood events in the future, including using crowd-sourcing mobile apps to provide instant information on flood events, and using modelling systems, like the CityCat system developed at Newcastle University, to anticipate which areas are more likely to flood. With this information, we may be able to take action to make our cities more flood-friendly in the future.