[GalenErso]

What causes El Niño to happen every few years? What mechanism drives the phenomenon? I was thinking maybe sun spots, but sun spots have 11 year cycles on average, so I don't think it's the cause. Why doesn't El Niño happen every year, like hurricanes?

[triska]

Quoting from https://earthobservatory.nasa.gov/world-of-change/ENSO:

"El Niño and La Niña reflect the two end points of an oscillation in the Pacific Ocean. The cycle is not fully understood, but the times series illustrates that the cycle swings back and forth every 3-7 years. Often, El Niño is followed immediately by La Niña, as if the warm water is sloshing back and forth across the Pacific. The development of El Niño events is linked to the trade winds. El Niño occurs when the trade winds are weaker than normal, and La Niña occurs when they are stronger than normal. Both cycles typically peak in December.

El Niño and La Niña aren’t the only cycles evident in this image series. The Pacific Ocean is moody: It turns slightly hot or slightly cold every couple of years. This bi-annual pattern isn’t the distinctive, well-defined stripe of warm ocean waters near the equator typical of El Niño, but rather, a general warming of the ocean.

On top of the two-year warm/cold cycle and the El Niño/La Niña pattern is a broader decadal cycle in which the Pacific has a warm and a cool phase. In the 1990s, the Pacific was in a warm phase. The strong El Niño of 1997 marked the end of the warm phase."

[roter]

Coriolis. There are timescales set up by two big mechanisms: one is westward-propagating oceanic Rossby [0] waves just to the north and south of the equator and the other is eastward-propagating Kelvin [1] waves along the equator which hit the Peruvian coast, split in two and flow north and south bouncing along the coast. Sloshing back and forth.

[0] https://en.m.wikipedia.org/wiki/Rossby_wave

[1] https://en.m.wikipedia.org/wiki/Kelvin_wave

[Rury]

It's ultimately because of the sun and the rotation of the Earth, which causes wind, which causes movement in oceans surface temperatures...

[dzhiurgis]

Was wondering the same. Perhaps there’s natural oscillation just because how continents are laid out.

[aschearer]

Putting my money on the moon.

[danielheath]

There’s nothing we could do to this planet (including climate change, ocean acidification , or even “launch all the nukes”) that would make it less hospitable to humanity than the moon/mars.

[kornhole]

The most of the heat created by all the CO2 we dump into the atmosphere is absorbed by the ocean.

[nomel]

No, it's a pattern that doesn't require man. The earliest record of El Niño was 13k years ago. [1]

[1] https://en.wikipedia.org/wiki/El_Niño