January 27, 2023 by Alyssa DiSabatino
As the climate warms, even predictable weather patterns — like El Niño and La Niña, which are affected by rising sea temperatures — are changing alongside the climate, a weather expert warns.
And that could mean more frequent and severe storms facing Canada’s property and casualty insurance industry.
Meteorologists are discovering emerging long-term weather patterns as a result of climate change, said Chris St Clair, former weather presenter and journalist at the Weather Network. And devastating “once-in-ten-year” weather events are increasing in frequency.
That’s cause for concern to the P&C insurance industry, which has seen the third-highest insured losses in Canada at $3.1 billion and fifth globally, at $132 billion in 2022.
El Niño and La Niña cycles drove 2022 global natural disaster losses, Munich Re reports. El Niño and La Niña are climate patterns in the Pacific Ocean that affect the weather globally.
El Niño refers to the above-average sea-surface temperatures that periodically develop across the east-central equatorial Pacific, whereas La Nina refers to the periodic cooling of sea-surface temperatures across the east-central equatorial Pacific.
“[Meteorologists] figured that pattern out about 35 to 40 years ago,” said St Clair. “What’s been interesting is, in the past 12 to 15 years, the actual regularity of El Niño and La Niña has also changed.”
St Clair said this is a result of climate change. He explained that because the atmosphere is warmer, it is capable of holding more moisture in the air—and more moisture means increasingly frequent and severe storms.
El Niño typically lasts nine to 12 months, while La Niña lasts the same length or up to one to three years. Both typically occur irregularly in intervals of two to seven years, various sources report.
Forecasters have predicted La Niña will persist through winter 2022-23 (December through February). El Niño will return later in 2023, and will exacerbate already extreme warm weather around the globe.
However, even these predictable climate patterns will be altered in frequency due to the warming atmosphere, forecasters say.
And while tried-and-true patterns are changing, new weather patterns are also simultaneously emerging.
“It’s a hard thing to get your head around,” said St Clair, who is presenting at CatIQ Connect in Toronto on Feb. 7. “Meteorologists who are involved in studying climate…are finding new patterns that are emerging and finding longer-term patterns that we hadn’t seen before….
“There are so many weather patterns that we haven’t discovered yet, just because some patterns are 20- and 30-year patterns.”
Changing severe weather events include atmospheric rivers, which affect the pacific coast regions like British Columbia, St Clair said.
Atmospheric rivers are relatively long, narrow regions in the atmosphere – like rivers in the sky – that transport water vapour outside of the tropics.
“These atmospheric rivers, well, they’re becoming more frequent,” said St Clair. “They’re not happening once every lifetime, or once every 10 years. What were once one-in-10-year events are now once-in-three-year events.”
An atmospheric river variation (called a pineapple express) was the cause of the 2021 British Columbian floods, the province’s costliest severe weather event in history.
“The atmospheric river is the worst possible scenario of destructive weather that [the west coast] can have, simply because of how their climate behaves in in the dry season (spring and summer) versus the wet season (fall and winter),” St Clair said.
“We get this heat dome, or very strong area of high pressure…over western North America in the summer, which leads to the drought problems, which leads to the forest fire problems, which leads to excessive heat that they get in the valleys. That dries the land out, they have the fires, and then when the [wet season] establishes itself…the topography is unable to cope with the amount of moisture that is being delivered.”
That’s because water often runs off dry soil instead of getting absorbed by it.
“That’s a West Coast pattern in climate change that is in place now and not likely to change until the atmosphere begins to cool again,” St Clair added.
But Canada is warming faster than the world as a whole — at more than twice the global rate — and the Canadian Arctic is warming at about three times the global rate, the government of Canada reports.
Plus, the areas of B.C. that flooded mostly intensely in 2021 are natural floodplains, St Clair observed.
“It traditionally flooded regularly until the [twentieth century]. We built a series of dikes and levees and everything to protect all over farmland, and traditionally that has not flooded to a severe degree until recently. Again, that’s because of the intensity now of the atmospheric rivers, which are stronger than they were 80 years ago.”
Feature image by iStock.com/LynMc42k