



Councillor El-Chantiry isn’t alone in wrestling with this one.




Borrowed from NOAA explainer


All this is true without climate change.


Spring temp increases in Ontario & Quebec








5 Comments on “Explainer: Is climate change the cause of the 2019 Ottawa River flooding?

  1. *What I mean by “certain scenarios” is what’s calculated to be a “worst case” scenario. Also called “high emissions” or “business as usual.” But that worst case simply represents a continuation of the greenhouse gas emission pattern that we’re following now, and have been for the 40 years or more that we’ve known it to be a problem. The 50 to 10 year probability change is calculated to accrue over this century.

  2. I am not disputing your scenarios or findings at all, I do believe them in regards to weather changes and temperature forecasts . What your scenarios do not take into account is the act that the Ottawa River is a completely managed waterway from beginning to end. All of the reservoirs and almost all the water passes through multiple dams and Hydro stations all controlled by Hydro One and Hydro Quebec. Since Hydro One went public in 2015 the Ottawa River has flooded twice. This should be looked into a little more closely.

    • My view on this is that complex events are never things that can all be blamed on one thing. I assume managing a watershed is complex thing to do and the changing variables that come with climate change make that even more challenging. A view from a non-expert in these things.

  3. I think I see your analogy here. Thanks for the nuanced explanation. Something I’m wondering though. You have an example where a 100-year event has a 63.4% chance of occurring over 100 years. Does that same principle apply to 50 and 10 year events over similar time periods? So, for example, would a 50-year event have a 63.4% chance of occurring over 50 years? I would assume that it probably isn’t exactly 1:1 but would it be roughly the same, higher, lower?

    Where I’m going with this is, if under certain scenarios a 50-year event moves to a 10-year event it would mean that that 10-year event may not occur, but is still more likely to occur. So climate change may not cause an event to occur but it is increasing the likelihood/risk of it occurring. Am I correct?

    • I think what you’ve said is generally correct. Think of flipping a coin. 50 50 chance of getting heads. But two tosses isn’t 100% likelihood of getting heads. Using that flood return calculator here https://www.weather.gov/epz/wxcalc_floodperiod I get close but not identical results. A 50 year flood has a 63.6% chance of happening over 50 years; a 10 year flood has a 65.1% chance over 10 years.

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