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No Evidence of an Anthropogenic Influence on Floods

Paper Reviewed
Hodgkins, G.A., Whitfield, P.H., Burn, D.H., Hannaford, J., Renard, B., Stahl, K., Fleig, A.K., Madsen, H., Mediero, L., Korhonen, J., Murphy, C. and Wilson, D. 2017. Climate-driven variability in the occurrence of major floods across North America and Europe. Journal of Hydrology 552: 704-717.

Model projections of future increases in precipitation from anthropogenic global warming have led to concerns that there will be corresponding increases in river flooding. Consequently, many researchers have begun to search for evidence of more frequent and/or severe flooding over the past several decades. The latest team of scientists to conduct such an investigation is Hodgkins et al. (2017), who examined trends in the occurrence of major floods across North America and Europe over the past eight decades.

In preparing for their analysis, the twelve researchers first made sure to build a proper database free of contaminating influences. This was accomplished by their using only those hydrologic stations that were located in minimally altered catchments. Such catchments, for example, had to contain (1) less than 10 percent urban area, (2) have no substantial flow alteration or changes in land cover, (3) less than 10 years of missing data and (4) good quality gauges capable of providing accurate peak-flow data. By sticking to these criteria, the authors were confident that any trends they found in the data would most likely be the result of climate-driven influences (either human-induced or natural in origin). This winnowing process led the authors to select 1204 hydrologic stations, which they utilized to examine for changes in major flood events over the period 1961-2010. They then repeated their analysis on a smaller subset of 322 stations over the longer time period of 1931-2010. And what did their results reveal?

Hodgkins et al. report that "there was no compelling evidence for consistent changes over time in major-flood occurrence during the 80 years through 2010," adding that "the number of significant trends in major-flood occurrence across North America and Europe was approximately [equal to] the number expected due to chance alone." Consequently, they conclude that "compelling evidence for increased flooding at a global scale is lacking." And this lack of evidence, we would add, disproves any and all attempts by climate alarmists to claim that major floods are currently increasing due to anthropogenic-induced climate change -- at least over this large portion of the globe!

Posted 5 February 2018