Is climate change to blame for Montréal’s messy winter?

(Cover photo: Radio-Canada/Simon-Marc Charron ;Ce billet est aussi disponible en français)

This winter has been a difficult one in Montréal, with several rainstorms followed by a rapid freeze leading to sidewalks that resemble glaciers. Many are wondering if this might be the new normal. Back in November, I wrote a post discussing how the start of “wintry” weather (snow, freezing cold) has been getting later and later over the last 50 years or so, with the winter season getting shorter. Here, I’ll examine a range of climate variables to demonstrate how our winters have already changed with global warming, and how this year’s winter fits into these changes.

Weather vs. climate

The first thing we might assume when we hear “global warming” is that winters will just get warmer. That actually sounds nice, doesn’t it? We first need to keep in mind the difference between weather and climate. When I spoke recently to the Montreal Gazette about how winters are changing, I got an email from a reader questioning whether I was living in the same city as him, since we’ve had plenty of snow this winter, and November was one of the coldest on record in Montréal! So what about global warming?

Remember that weather is what we observe in a given month, week, or day. Climate is the average of all of those months/weeks/days over a certain period (typically at least 30 years). We’re always going to have really cold days and really warm days, but as the climate changes, what constitutes “really warm” and “really cold” is changing. One sign of the warming climate is that we’re seeing far more record hot days than record cold ones. And our “extreme” cold is getting less extreme. For example, through the 1980s, -30°C was observed at Montréal at least once every few years. The last time we hit -30°C (at Trudeau Airport) was in 1994!

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