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Clean Energy Canada | Media brief: The link between extreme weather and climate change
June 28, 2021

Over the last few years, record-breaking temperatures across Canada have been accompanied by unprecedented wildfire seasons and floods. And yesterday saw parts of B.C. hit over 46C, looking set to break all-time Canadian temperature records, with even hotter temperatures expected today. Meanwhile, B.C.’s 2017 and 2018 wildfire seasons were the worst two on record. Ottawa has experienced two one-in-100 year floods in only three years. While these events are indeed linked to climate change, media coverage of the events does not always make the connection.

Extreme weather attribution is a growing field of climate science, with an increasing number of studies dedicated to establishing the role that climate change plays in our changing weather patterns. It is now possible to attribute certain weather events to climate change with a reasonable degree of confidence, with one analysis suggesting 68% of all studied extreme weather events were made more likely by climate change. 

While directly attributing extreme weather events to climate change is rarely possible, coverage of extreme weather events presents an important opportunity to educate the public about the relationship between extreme weather events and climate change, the field of attribution science, and conclusions that have been drawn regarding similar past weather events.

KEY FACTS

According to the Intergovernmental Panel on Climate Change, “it is very likely that heat waves will occur more often and last longer, and that extreme precipitation events will become more intense and frequent in many regions.” 

Wildfires: Several Canadian institutions have investigated the link between specific wildfire events and climate change and have established the following:  

  • The Fort McMurray fire was 1.5 to 6 times more likely because of climate change. Another study found that pressure vapour defects, which increased the fire risk, were made worse by climate change. 
  • The 2017 record-breaking B.C. wildfires were made 2 to 4 times more likely, while the area burned was 7 to 11 times bigger.
  • The conditions that caused the devastating wildfires in southeastern Australia in late 2019 and early 2020 were made at least 30% more likely due to the effects of climate change.

Heatwaves: Heatwaves will become longer and more intense because of climate change:  

  • The Intergovernmental Panel on Climate Change indicates “it is virtually certain that there will be more frequent hot and fewer cold temperature extremes over most land areas on daily and seasonal timescales” and that “it is very likely that heat waves will occur with a higher frequency and longer duration.”
  • A new study found the 2018 northern hemisphere heatwave, which killed 74 people in Quebec, would have been “impossible” without climate change.
  • Other studies say it’s “very likely” that climate change contributed to temperature extremes observed since the mid-20th century. 
  • Another study found that extremely hot days occur five times more often when compared to pre-industrial times as a result of climate change (where an extremely hot day is a one-in-a-thousand day event under pre-industrial conditions).
  • A rapid attribution analysis of the heatwave in Europe in June 2019, which saw temperatures of more than 45C in parts of France, found it was made five times more likely because of climate change.

Floods: 

  • 1-in-100-year flood events in Toronto and Montreal are expected to become 1-in-15 year events by the end of the century as a consequence of climate change, according to a study by scientists from Western University and the National Research Council of Canada.
  • Research investigating the 2013 Alberta floods found that climate change may have led to an increased likelihood of extreme rainfall. 
  • Another Canadian study, looking at the extreme flooding in Saskatchewan and Manitoba in 2014, found that climate change may have played a role in the significant increase in rainfall.
  • Another study found that extremely rainy days are 18% more likely now than they were in pre-industrial times as a result of climate change (where an extremely rainy day is a one-in-a-thousand day event under pre-industrial conditions). This is expected to climb to 65% if global warming reaches 2C.

For additional Canadian attribution studies, see page 175 of the Canada’s Changing Climate Report.