Opinion: Claims that rising frequency and intensity of storms is causing rise in payouts not based on science

Robert J. Muir

Flooding and the damage it can cause are of concern for good reason, and we all share the desire to mitigate the losses caused by flooding. However, the contention of Craig Stewart of the Insurance Bureau of Canada (IBC) in a recent op-ed in these pages, that increases in the frequency and intensity of severe weather are the cause of rising insurance claims, is iill-founded

First, the IBC has promoted its “Telling the Weather Story” report claiming that weather events that once occurred every 40 years now occur every six years in parts of the country, citing the source for that claim as Environment Canada data. This claim was based on nothing more than a hypothesized shift in a probability distribution, with no foundation in fact. Environment Canada corrected this IBC claim in Canadian Underwriter, and Canada’s largest insurers no longer repeated the IBC claim after they were made aware of the data.

IBC does not help its members by ignoring the real causes of flooding or hyping unfounded storm intensity and flood loss correlations at the expense of sound science and engineering

Second, the CBC Ombudsman concluded that CBC reports on the topic were incorrect in reporting insurance-industry claims that increases in the frequency and intensity of severe weather are the source of these rising insurance claims costs. In his op-ed, Mr. Stewart argued that the ombudsman used only one source to reach his conclusion. But that source, Environment Canada, compiles many other papers that have the same finding that there has been no change in severe weather events.

Furthermore, 10 studies in southern Ontario alone, by leading universities, municipalities and engineering consultants, have shown no change in storm design intensities that drive flood damages. When rainfall trends are extended to incorporate more recent data, including 2013 extremes, it is seen that there is no increasing trend in observed maximum rainfall amounts to support IBC’s repeated hypothesis that storms are on the rise.

The accompanying chart shows the trend from Toronto’s Pearson Airport meteorological station. Despite the 2013 extreme, the overall trend is still downward when recent data are considered.

The observance of correlation is too often used to declare causation, such as IBC claiming rain intensity as the cause of greater flood losses. While IBC may be confident in its loss numbers (even though 1990s values are not as robust as values compiled since 2008), it cites absolutely no rain data to correlate with those losses. Thus, IBC skipped right over correlation and claimed causation.

This is not science.

If losses have doubled since the 1990s, we must also look to the science of hydrology for an explanation. Unlike storm trends, urbanization and intensification have increased by significant factors for many decades and logically explain greater urban runoff and flood risk. We must accurately characterize the true causes of flooding to focus on the most effective solutions. If engineers ignore the facts and design flood mitigation infrastructure according to IBC’s falsely claimed frequency shift of 40 to six years, or the new unfounded claim that storms are more intense since 2009, scarce public resources would be diverted to over-designed, unnecessary works, delaying or even preventing implementation of reasonably sized infrastructure that is greatly needed.

Should governments focus on mitigation due to a “weather story” about bigger storms, they may do so at the expense of timely and effective adaptation strategies focused on the real problems.

IBC does not help its members by ignoring the real causes of flooding or hyping unfounded storm intensity and flood loss correlations at the expense of sound science and engineering.

Robert J. Muir, P. Eng is an Ontario municipal engineer and member of the Ontario Society of Professional Engineers

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