Tenfold increase in extreme rainfall in East London

A new study from Lloyd’s, the world’s leading specialist insurance market, shows that East London has experienced a tenfold increase in extreme daily rainfall since 1960 and warns that the closing of meteorological stations is resulting in incomplete data, impairing future analysis.

Research by the Lloyd’s Emerging Risks team and the Climate Change Risk Management consultancy found rainy days of 25mm have become more frequent, increasing 33% since 1960. However, the change is most significant for days of extreme rainfall over 40mm, which recorded a 900% increase.

The study examined daily rainfall levels at Crossness Sewerage Station from 1915 to 2006 and found only one day prior to 1960 recorded rainfall exceeding 40mm, compared with ten days between 1960 and 2006. Over the entire period analysed, over half of the days with rainfall over 40mm were in September.

Trevor Maynard, Manager of Emerging Risks at Lloyd’s said:
“Extreme daily rainfall has become more frequent and more severe in the East London location we studied. A day with a 45mm rainfall occurred once every 30 years before 1960 and now occurs once every six years.

“Floods and other natural hazards are expected to become more common as our climate changes and we need to better understand and prepare for the impact on our homes and infrastructure. This climate trend was only evident because we drilled down into the rainfall data at a daily level.

“It’s important that information is collected at such a granular level and made freely available if we are to understand how our climate is changing and plan ahead.”

The report highlights the importance of studying data at a granular level, as the trends would have been hidden in a monthly, seasonal or annual data analysis.

The results are consistent with climate change predictions for an increase in the frequency and severity of extreme rainfall events, but not those climate models that predict a shift towards wetter winters and drier summers.

The report advises against over-reliance on one specific climate model though Lloyd’s still believes they remain a critical way in which we can assess the impact of future climate change.

About Lloyd’s
Lloyd’s is the world’s leading specialist insurance market and occupies fifth place in terms of global reinsurance premium income, and is the second largest surplus lines insurer in the US. In 2010, 78 syndicates are underwriting insurance at Lloyd’s, covering all classes of business from more than 200 countries and territories worldwide. Lloyd’s is regulated by the Financial Services Authority.