|Are Ontario Rainfall Trends a Nothing-Burger?|
Read This Post and Find Out !
|Southern Ontario IDF Trends - Decreasing Frequent Storm Intensity, Mixed Infrequent Storm Intensity, Overall Decrease in Average Rainfall Intensity Values for Engineering Design. 5-Minute to 24-Hour Durations.|
i) small frequent storms (2-year, 5-year, 10-year return periods) used to design storm sewers, for example, are consistently smaller now than in the 1990 dataset,
ii) large infrequent storms (25-year, 50-year, 100-year return periods) used to design major drainage systems and infrastructure networks are mixed with some increases and some decreases since 1990 but no appreciable change that would affect design (any changes are less than 1%, which is negligible in engineering design),
ii) there is an overall average decrease in IDF values of 0.2 % across all return periods and durations.
Percentage IDF change values shown in the detailed chart are summarized in the following table for 5-minute, 10-minute, 15-minute, 30-minute, 1-hour, 2-hour, 6-hour, 12-hour and 24-hour durations, and for 2-year, 5-year, 10-year, 25-year, 50-year, and 100-year return periods.
So what are we to make of this? The media, the insurance industry, and those who are exercising their 'availability' bias instead of looking at storm statistics, have regularly reported that storms are bigger, or more frequent, or both, but the local Ontario data shows the opposite (Northern Ontario will be a different story as AMS trends were up in the north, unlike the south). The Ontario government website is even out of step with the data.
The new Progressive Conservative government in Ontario has just renamed the Ministry of Environment and Climate Change the Ministry of the Environment, Conservation and Parks, taking out 'climate change', but the content under it has not been updated.
|Ontario Ministry of the Environment, Conservation and Parks replaces former Ministry of the Environment and Climate Change. New name but content still reflects climate change effects on storms that is inconsistent with data.|
|Ministry of the Environment and Climate Change website links extreme weather with climate change.|
- the severe ice storm in December 2013 resulted in $200 million of property damage in OntarioToronto lost an estimated 20% of its tree canopy during the storm
- Intact Financial, one of Canada's largest property insurers, is raising premiums by as much as 15-20% to deal with the added costs of weather-related property damage
- Thunder Bay declared a state of emergency in May 2012 after being hit by a series of thunderstorms, flooding basements of homes and businesses due to overwhelmed sewer and storm water system"