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Floods of Switzerland Over the Past Five Centuries
Schmocker-Fackel, P. and Naef, F. 2010. Changes in flood frequencies in Switzerland since 1500. Hydrology and Earth System Sciences 14: 1581-1594.

One of the potential negative consequences of global warming about which climate alarmists are very concerned is an increased frequency of flooding; and one way to assess the validity of this concern is to see how flooding around the world has responded to the historical warming of the globe that has occurred since the end of the Little Ice Age, which is the approach that was taken by Schmocker-Fackel and Naef in their recent study of the subject.

What was done
The authors collected and analyzed historical flood time-series of fourteen catchments located in northern Switzerland, which data sets stretched back in time a full five centuries.

What was learned
The two Swiss scientists were able to identify four periods of frequent flooding in northern Switzerland, lasting between 30 and 100 years each (1560-1590, 1740-1790, 1820-1940 and since 1970); and they report that the first three periods of intervening low flood frequency (1500-1560, 1590-1740 and 1790-1810) were found to correspond to periods of low solar activity. However, they report that "after 1810 no relationship between solar activity and flood frequency was found, nor could a relationship be established between reconstructed North Atlantic Oscillation indices or reconstructed Swiss temperatures." In addition, they determined that "the current period of increased flood frequencies has not yet exceeded those observed in the past." And they write that "a comparison with the flood patterns of other European rivers suggests that flood frequencies are not in phase over Europe."

What it means
In light of their several diverse findings, Schmocker-Fackel and Naef conclude that "the current period with more floods in northern Switzerland, which started in the mid 1970s, might continue for some decades," even under conditions of "natural climatic variation." Therefore, one cannot validly claim that the most recent period of frequent flooding in northern Switzerland has been in anyway related to the global warming that has occurred there over the last several decades, which climate alarmists are fond of describing as having experienced "unprecedented global warming."

Reviewed 29 December 2010