From the CO2Science Archive: Stating the purpose of their work in the first sentence of their paper’s abstract, Macdonald and Sangster (2017) write that “the last decade has witnessed severe flooding across much of the globe, but have these floods really been exceptional?” Attempting to answer this question for Britain, which has experienced a series of floods since the turn of the present century, the two United Kingdom researchers present the “first coherent large-scale national analysis undertaken on historical flood chronologies in Britain.”

Paper reviewed: Macdonald, N. and Sangster, H. 2017. High-magnitude flooding across Britain since AD 1750. Hydrology and Earth System Sciences 21: 1631-1650.

To accomplish their objective, Macdonald and Sangster collected and reviewed documented descriptions of historical floods, physical evidence or epigraphic markings providing evidence of river flows, and instrumental river flow data from several catchment systems across the nation, building a reliable database of extreme flood events since AD 1750. And by examining the spatial and temporal variability of that database they were able to determine if the recent floods since the 2000s have indeed been exceptional. So were they?

In a word, no! According to the two researchers, “the apparent increase in flooding witnessed over the last decade appears in consideration to the long-term flood record not to be unprecedented,” and they add that “whilst the period since 2000 has been considered as flood-rich, the period 1970-2000 is ‘flood poor,’ which may partly explain why recent floods are often perceived [by the popular media] as extreme events.”

And so it is that Macdonald and Sangster’s work refutes the oft-repeated, but false, claim that rising atmospheric CO2 concentrations are increasing (or will increase) the frequency of extreme floods. It certainly has not been the case for Britain.