El Niño, the climate system characterised by dry and warm temperatures, and La Niña, influencing rainfall and associated with cooler temperatures, are widely mentioned in conversations about the environment.
But there are two occurrences interacting with them that Dr Ben Henley, a research fellow at the University of Melbourne, says have "important impacts" on our global temperature - and this week .
Alongside El Niño and La Niña are their "cranky uncle" El Tío and "kind aunty" La Tía, Dr Henley told SBS News.
"It's a new way" to think about changes to our climate, he said.
El Tío and La Tía form the , a term used in a late 1990s study that looked at how Australia’s climate changed in periods of decades.
They are similar to El Niño and La Nina, which shift between each other every two and seven years, known as the El Niño Southern Oscillation.
El Tío is like the "slow-moving uncle" of El Niño, Dr Henley explained.
It's prevalent for periods of between 10 and 30 years, and is associated with warmer temperatures in the tropical Pacific and accelerating the rate of global warming.
La Tía, prevalent for the same length of time, and the phase scientists believe we're in now, is "the kind aunty", Dr Henley said.
"She is kind of cushioning the blow of global warming and like the long-term version of La Niña," he explained.
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He used the analogy of climbing a mountain to explain where they fit in general direction of the world's climate.
While you're climbing up (global warming) there are hills (El Tío) - such as the period from the late 1970s until the late 1990s - and dips (La Tía) - the cooler period that we are in now - along the way.
"We understand the phases of El Tío and La Tia oscillate back and forth, [but] there's a long-term trend across both phases of warming that is unequivocal across the earth," Dr Henley said.
"There are times when it's accelerating and times when it's slowing down a little bit."
When El Tío takes precedence again we will experience a jump in temperatures, he warned.
Overall, however, "it's critical that we work at home and with international organisations and other countries around the world to reduce greenhouse gas emissions because that is the primary cause, as we know, of global warming," he said.
Dr Henley pointed out there was still much scientists could learn about the two little-known phases – they still don't know exactly what they're the result of, and how long they last.
Scientists have begun looking at new data coming from the ocean, which measures the atmosphere and ocean circulation, particularly the deep ocean, that may provide some clues, he said.
