Over the last few years, record-breaking temperatures across Canada have been accompanied by unprecedented wildfire seasons and floods. The 2017 and 2018 wildfire seasons were the worst two on record in British Columbia. Ottawa has experienced two one-in-100 year floods in only three years. While these events are indeed linked to climate change, direct attribution is often approached by media with hesitation.
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 given attribution science generally occurs after the fact, 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.
- 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.
- Heatwaves: Heatwaves will become longer and more intense because of climate change:
- 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 this June, which saw temperatures of more than 45C in parts of France, found it was made five times more likely because of climate change.
- 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.