El Nio is back. Here's what it means for Canada

It was long anticipated, and now it's here.

The global weather pattern El Nio has returned for the first time in seven years, according to the World Meteorological Organization, setting the stage for further extreme weather and soaring temperatures.

The United Nationsagency made the declaration on Tuesday, after months of forecastingthat suggestedthe weather pattern was likely to return.

"The onset of El Nio will greatly increase the likelihood of breaking temperature records and triggering more extreme heat in many parts of the world and in the ocean," WMO Secretary General Prof. Petteri Taalas said in a statement on Tuesday.

While it's a natural phenomenon, this is the first time El Nio has happened on top of a baseline of so much human-caused warming, leadingthe WMOto say it is "playing out in uncharted waters."

Here's a breakdown of how El Nioworks, and what its return could mean for Canada.

Wait, what is El Nio again?

El Nio is a naturally occurring climate pattern associated with warming of the ocean surface temperatures in the central and eastern tropical Pacific Ocean.

(The opposite isLa Nia, where the surface of the Pacific Ocean cools.)

Together, the El Nio/La Nia cycle is referred to as theEl Nio-Southern Oscillation (ENSO).

El Nio occurs on average every two to seven yearsand typically lasts nine to 12 months.

It has been linked toextreme weather conditions, from heavy rainfall in South America to drought in Australia and parts of Asia.

The WMO said there is a 90 per cent probability this latest El Nio event will continue through the second half of 2023 and is expected to be at least of "moderate strength."

The world's hottest year on record, 2016, coincided with a strong El Nio the last one before this year.

It appears the effects are already being felt.

Monday and Tuesday were the two unofficial hottest days in human record-keeping, according to University of Maine scientists at theClimate Reanalyzer project.

On Tuesday, the Earth's average temperature spiked at 17.18C. The previous record was inAugust 2016, with arecord of 16.92 C.

WATCH | El Nio could make 2023 the hottest year on record:

El Nio and climate change could make 2023 hottest year on record

1 year ago

Duration 2:06

The World Meteorological Organization says El Nio is upon us. The naturally occurring phenomenon is colliding with an already warming planet and could help make 2023 the hottest year on record, meteorologists say.

How does this relate to climate change?

Regardless of where it is in the El Nio/La Nia cycle, the Earth is warming due to increased CO2 in the atmosphere.

The past three years of La Nia still saw some of the warmest global temperatures on record.

Experts say the warming could have been even more pronounced without that cooling phenomenon.

A WMO report published in May predicted there is a 98 per cent chance that at least one of the next five years will be the warmest on record, beating the record set in 2016.

"I think it's fair to say that with an El Nio that is occurring in a background state of global warming, that extreme weather will become more extreme," said John Gyakum,a professor in McGill University's atmospheric and oceanic sciences department.

Hansi Singh, an assistant professor in the school of earth and ocean sciences at the University ofVictoria, describedEl Nioas being "superimposed on global warming."

"That's what we're experiencing right now globally," Singh said.

"You can see that in the global sea surface temperatures. You can see that ... in the global surface air temperatures we're breaking records left and right this year."

What can we expect in Canada?

Historically, Canada is mostly affected by El Nio during winter and spring.Milder-than-normal winters and springs occur in Western and Central Canada.

"I would bet a few loonies on the fact that with El Nio, especially if it's strong and it's large, we're in for a warmer-than-normal winter coming up," said Dave Phillips, senior climatologist with Environment and Climate Change Canada.

It could also mean fewer hurricanes in Atlantic Canada, he said.

During the last El Nio, in the winter of 2015-16, winter in Canada was 1 C to 5 Cwarmer than normal across all provinces, with especially unseasonal warmth in Quebec, the central Prairiesand Yukon.

Warmer temperatures won't necessarily lead to an easier winter, Gyakum said.

"It doesn't mean that you're going to have balmy weather. On the contrary, we can have very inclement weather," he said, pointing to Quebec's devastating 1998 ice storm, which also occurred during anEl Nioyear.

What about thissummer?

Canada doesn't tend to see a direct impact from El Niountil later in the year, Gyakumsaid.

"Most of the impacts of El Nio occur during the wintertime when the jet streams are more active," he said.

Phillips said it's unclear to what extent the global weather pattern has affected the summer so far and Canada'srecord wildfire season.

But he said certain extreme weather events could potentially be linked to El Nio, including heat waves in the U.S. south and Mexico, the U.K and China.

"I wish I had more of a connection with summer weather and El Nio, but science hasn't really gotten there yet," he said. "It takes a lot of working and modelling and statistical analysis to determine that."