It has been a snowy, windy and bone-chilling winter for many Canadians. British Columbians dug out of abnormal snow in early March. The prairies have seen a good dose of good old fashioned winter, and extremely cold warnings were also issued in Ontario, Quebec and the Atlantic provinces. Then there was the Christmas travel period which was thrown into chaos by winter storms – a huge mess from coast to coast.
One thing that points to all that cold weather is La Niña. It is a climate pattern that results in colder ocean water building up off the coast of Ecuador and Peru. It initiates a change in atmospheric conditions farther north, resulting in cooler air over the North American west coast and drier air in the southern United States.
Now that cooldown period is weakened, which can usher in a longer period of extreme heat – Possibly even push the global average temperature past the all-important 1.5C threshold, beyond which, scientists fear, the planet will pass irreversible tipping points.
What is La Niña?
La Niña is a climate phenomenon that results in cooler than normal water appearing off the coast of South America, near Ecuador and Peru.
La Niña occurs when stronger trade winds push warm water away from South America and toward Australia and Indonesia across the equatorial Pacific Ocean, leaving an accumulation (or upwelling) of cold water.
The cooler air inhibits cloud formation and rain in the eastern Pacific near South America. It also generates a lot of rain in the western Pacific over Indonesia. These anomalies drive the jet stream—high-altitude bands of fast-flowing air that control weather— further north. Changes in atmospheric conditions have a ripple effect on weather patterns across North America that can last for months.
La Niña is typically associated with a period of cooler temperatures, particularly in western Canada, said Bill Merryfield, a scientist with Environment Canada’s climate modeling office. He says La Niña’s cooling effect may have dampened the wildfires in BC last year.
But the effects can be felt even months after La Niña begins to fade, which has already begun. Because of these lingering effects, Merryfield says Environment Canada is predicting a cooler spring on Canada’s west coast. But that doesn’t mean we don’t expect much more warmth in the not-so-distant future.
How long do La Niñas usually last?
La Niña’s “opposite” is El Niño. It is a period of warmer sea water in the equatorial Pacific. The earliest recorded El Niño was in 1578. The warming phenomenon was first noticed by Ecuadorian and Peruvian fishermen around Christmas, hence the Spanish reference to the “Christ Child” or “little boy”. Decades later, when a cooling trend was routinely observed after El Niño, it was named La Niña, or “the little girl.”
These two weather anomalies do not occur regularly, but appear every two to seven years. The last strong El Niño peaked in late 2015-early 2016, and before that in 1997-98. The last strong La Niña was in 2010-11.
Typically, El Niño and La Niña conditions begin to occur around June and last for about nine months. They reach their peak in December and continue right into the following spring.
But what makes the current cycle unusual is that La Niña conditions have persisted for three consecutive years, starts in 2020, a pattern not seen since the 1970s.
Tom Di Liberto, a climatologist at the US National Oceanographic and Atmospheric Administration (NOAA), says “we are currently in the midst of our third La Niña winter in a row.”
In his view, that pattern is highly unusual. “This is only the third time it’s happened” since official weather records began to be kept.
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There are clear indications that the current pattern of La Niña cooling is weakening. That means a return to neutral conditions and, very likely, the formation of La Niña’s opposite—El Niño, a period of warming—in late summer or fall.
In fact, climatologists are already starting to see it happening.
“You’re actually seeing just a hint of El Niño starting to develop offshore (of South America),” Merryfield says. “And our forecast points to that developing over the coming seasons.”
If La Niña disappears, how warm will it be?
In the near future we can expect a prolonged period of global warming. The growing El Niño could push temperatures up next winter and into 2024.
“Global temperatures tend to be higher in years with an El Niño, and especially the year after El Niño peaks,” says Merryfield. That’s what happened in 2016, the hottest year on record for the planet, which also came after a very strong El Niño the year before.
That means, according to Merryfield, there is a very good chance that 2024 will also be a record, especially as global warming continues to become more and more pronounced with increased emissions of greenhouse gases accumulating in the atmosphere.
NOAA’s Di Liberto suggests El Niño will give global warming a “boost up.”
“If someone tries to lower a ten-foot basket and they get about nine feet, El Niño helps push that extra foot up.”
What do these weather phenomena tell us about global warming?
It may seem that the presence of La Niña, associated with cooler temperatures, is a good thing in terms of global warming, especially if there have been back-to-back La Niña cycles in a row, as has been the case for the past three years.
That is until you consider another stark reality, says Di Liberto: the past decade has seen some of the warmest temperature averages on record, even with the more pronounced presence of La Niña, which is associated with cooler temperatures.
In other words, the Earth has broken these temperature records, even with the planetary equivalent of a cold compress – La Niña – present.
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Even the year 1998, which featured a very strong El Niño warming trend, does not come close to matching some of the temperature records set in later La Niña years, despite its cooling effect. “The fact that (2022, a La Niña year) crushed (1998, an El Niño year) in terms of global temperature anomalies … just indicates that our planet is warming.”
Now take away the cooling effect of this year’s La Niña, add the warming effect of the upcoming El Niño, and all of a sudden you have the recipe for what could be a record heat year in 2024, says Merryfield.
“I think there’s a very good bet that that record will be broken.”