Rare ‘triple-dip’ La Niña could mean a wild winter ahead for Western Canada

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Our climate has been steadily changing with a tendency toward warmer average temperatures, especially in recent decades. 

But within that steady climb, of course, we have variations. 

One of the biggest predictable swings in an area’s climate has to do with El Niño and La Niña. In the Spanish language, the words mean little boy and little girl; in weather, they are climate patterns in the Pacific Ocean that can affect weather conditions around the world. 

The climate kind of operates like a pendulum, swinging from El Niño conditions, through neutral ones, then to La Niña conditions. Sometimes the pendulum is faster, sometimes it’s slower.

But what happens when the pendulum gets stuck?

We could find out this winter. Projections point toward the chance of a “triple-dip” — that is, third consecutive —  La Niña winter.

We are in a La Niña situation right now and have had La Niña winters since 2020. 

According to the latest report from the World Meteorological Organization (WMO), there is a 70 per cent chance for La Niña to continue through the summer and a 50-to-60 per cent chance it will continue to the end of the year and into another winter.

But what does that mean for our weather locally? And what about the million-dollar question: What role does climate change play?

What is La Niña?

La Niña means that the ocean waters at the surface in the eastern Pacific Ocean are running colder. It’s the opposite of El Niño, where those water temperatures trend warmer. 

The benchmark for declaring an El Niño or La Niña is half a degree over or under a long-term average but it can, of course, be more significant than that. Nonetheless, that innocent-sounding change can have a big impact on weather along the Pacific coast as well as globally. 

According to the WMO, that ocean cooling can trigger changes in the tropical atmospheric circulation, predominantly with winds, pressure and rainfall.

“When there is a La Niña, it’s normally followed by a kind of drought in East Africa and drought along the coastal area of the Gulf of Mexico. And floods in other parts of the world, for example, in West Africa,” says Wilfran Moufouma Okia, head of the WMO’s regional climate prediction services division in Geneva, Switzerland.

But those cold ocean waters play with our Canadian weather, too.

During La Niña years, the jet stream over North America is often shifted further north, which causes changes in temperatures, storm tracks and precipitation, especially in the winter months.

“It tends to mean cooler-than-normal conditions for a lot of Western Canada and wetter-than-normal in the south of B.C., close to the coast,” says Nathan Gillett, a research scientist with Environment and Climate Change Canada.

Triple-dip La Niñas are rare

Though La Niñas vary in length and in strength, if this one rolls over into another winter, it would be the third triple-dip La Niña since 1950, according to the WMO.

“It’s a rare phenomenon,” Gillett says. 

But it’s not unheard of, adds Moufouma Okia.

“This La Niña episode in terms of length is not unprecedented,” he says.

La Niña’s Canadian impact

In the past, our La Niña winters have meant wild weather for Western Canada. 

In the winter of 2010-11, during a particularly powerful La Niña, heavy snowfall dominated Western Canada, with the Mount Washington Alpine Resort on Vancouver Island seeing over 500 centimetres of snow by late December.

That La Niña also meant cold winter temperatures across the Prairies and heavy snowfall in Alberta, where Edmonton saw close to 160 centimetres of snow between October 2010 and March 2011. Alberta’s capital would usually see about 85 centimetres during that time period.

During a three-year La Niña event in the late ’90s, storms brought record snowfall. 

A record 145 centimetres of snow — that’s about 4.75 feet — fell in a single day at Tahtsa Lake, located in British Columbia’s Coast about 120 kilometres southeast of Terrace, according to Environment and Climate Change Canada The storm on Feb. 11, 1999, was right in the middle of that three-year La Niña.

Climate change and La Niña

The relationship between climate change and our La Niña conditions is a little complicated, Moufouma Okia says.

There is no clear link between more areas being impacted and climate change, he says. But by 2050, there is expected to be a change in precipitation.

“There’d be extremes in precipitation in places where we normally have the impact of La Niña or El Niño,” he says.

Gillett adds that while El Niño and La Niña will continue into the future, our neutral state between the two may start to shift warmer. 

“It’s expected to remain the dominant mode of variability,” he says. “The kind of mainstay is expected to change a bit towards El Niño-like conditions.”

Our planet is changing. So is our journalism. This story is part of a CBC News initiative entitled “Our Changing Planet” to show and explain the effects of climate change. Keep up with the latest news on our Climate and Environment page.