No Evidence the 2014 Flooding in Southeast Saskatchewan is Due to Climate Change

As southeast Saskatchewan begins the recovery from flooding in late June after intense rains over the span of a couple days, the inevitable questions get asked -- is anthropogenic climate change to blame?

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While the amount of rain some communities received over a short time frame was substantial, there appears to be no evidence in the recent climate record that these types of events are becoming more common or severe. In fact, the southeastern region of the province is notable for its lack of climate change over the past quarter-century, despite the corresponding rapid rise in greenhouse gas concentrations. Indeed, the increase in atmospheric carbon dioxide concentrations since 1990 is about 40 percent of the total increase since pre-industrial times. Since 1990, there have been no significant trends in mean, mean maximum, or mean minimum temperatures for the month of June at any of the seven long-term Environment Canada Adjusted And Homogenized Canadian Climate Data stations (Cote, Estevan, Indian Head, Kelliher, Regina, Yellow Grass, and Yorkton) in and around the flood-affected area of southeastern Saskatchewan. Nor have there been any trends in June precipitation at these sites during the past quarter-century. At neither Regina -- which was particularly hard hit by torrential rains during the 2014 floods -- nor Estevan, in the extreme southeast corner of the province, have there been any trends in maximum one-, two-, or three-day rainfall accumulation totals during the month of June since 1990. The 2014 rainfall event in Estevan wasn't even particularly unusual over the past 25-years, and while the event in Regina was the largest over the last quarter-century, when we step back at look at the complete climate record for Regina dating back to the late 1800s, it is abundantly clear that the 2014 event (shown as red dots in the figure below) was not a record, nor is there any evidence of a trend over the past 130 years towards more extreme single- or multi-day rainfall events in this area. In fact, the correlations since the late 1800s are negative (i.e., towards less extreme precipitation), not positive. Thus, when the Calgary Herald quotes a "prominent hydrologist" at the University of Saskatchewan as saying "heavy precipitation inundating southeastern Saskatchewan fits with a century-long trend that threatens the entire Prairies with more frequent flooding," I'm not seeing the clear evidence to support this claim in the historical data. And when journalists claim that Saskatchewan and Manitoba "are facing an expensive cleanup -- and fears that infrastructure may not hold up if weather continues to be as wicked and variable as it was in the distant past. It could prove a challenge for cities and building codes created during the weather lulls of the '50s, '60s and '70s," one must question the claim of "weather lulls of the '50s, '60s and '70s" when building codes were created. During these decades, Regina saw even more intense 1-, 2-, and 3-day precipitation events than it experienced this year. So where is the weather lull of the 1950s through 1970s in Regina and southeastern Saskatchewan? The answer is that it simply doesn't exist. The fantasy that the climate decades ago was less extreme than at present gets widely repeated in the media, but a critical examination of our historical data reveals this myth for what it is. Others write opinion pieces in local newspapers asking if anthropogenic climate change is to blame. Yet, even a cursory examination of the local and regional climate data would show that it is not.

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