What Is
El Niño, Really?
Can't play sound? The illustrated version is right below.
Read the transcript
The full narration of the video.
This August, a huge patch of the middle Pacific ran more than two and a half degrees warmer than usual. The highest for that time of year since 1951. Forecasters call this El Niño. How can one warm patch of sea change the weather across half the planet? Try a little experiment in your head. Picture a long tub of bathwater in the sun: warm on top, cool underneath.
Now take a fan, and blow across the surface from right to left, nonstop. The warm water piles up on the left, thicker and thicker. On the right, with the warm layer blown away, cool water rises from below to fill the gap. The Pacific is that tub. South America is on the right, Asia and Australia on the left. The fan is the wind that blows west along the equator all year round.
With the warm water piled up near Asia, the air there is hot and damp, so that's where the rain falls. Off South America, the cold water rising up carries food from the deep and feeds huge schools of small fish. So what happens if the fan runs out of steam? When the wind weakens, the warm water piled on the left is like something let go. It sloshes back, all the way to South America.
The cold water can't rise anymore. The small fish lose their food. And the rain moves with the warm water: downpours hit the South American coast, while Indonesia and Australia tend to dry out. That's El Niño. Peruvian fishermen named it: the warm water often showed up around Christmas, so they called it "the child" — the baby Jesus born at Christmas. So it isn't a storm. It's a whole ocean's worth of warm water moving house. It comes back every two to seven years on average, and often stays for nine months to a year.
Even from half a world away, it nudges our weather too. China's National Climate Center expects: a warmer winter overall, but with big swings. Next summer, more rain along the middle and lower Yangtze. Watch out for floods. It's not the only cause, but this time, it's unusually strong. It's expected to peak around November. The strongest one before this came around 2015, at 2.8 degrees above normal. This one is expected to pass 3.
Will it really be the strongest on record? Even scientists have to wait for winter to find out. So take a guess first: record broken, or not?
A patch of sea, 2.5° too warm
A huge patch of the Pacific along the equator is more than 2.5°C warmer than usual.
This August’s reading was the highest for that time of year since 1951. Forecasters call this El Niño. But how can one warm patch of sea change the weather across half the planet?
A bathtub and a fan
Try a little experiment: a long tub of bathwater sits in the sun. Warm on top, cool underneath.
Now blow a fan across the surface, right to left, nonstop. The warm water piles up on the left, thicker and thicker. On the right, with the warm layer blown away, cool water rises from below to fill the gap.
The Pacific is that tub
South America is on the right, Asia and Australia on the left. The fan is the wind that blows west along the equator all year round.
With the warm water piled up near Asia, the air there is hot and damp, so that’s where the clouds and rain are. Off South America, the cold water rising up carries food from the deep and feeds huge schools of small fish.
The fan runs out of steam
When the wind weakens, the warm water piled on the left is like something let go: it sloshes back, all the way to South America.
“The Child”
That’s El Niño. Peruvian fishermen gave it the name.
The warm water often showed up around Christmas, so they called it “the child” — the baby Jesus, born at Christmas.
This one is unusually strong
China’s National Climate Center expects it to peak around November, passing the event around 2015 and quite possibly becoming the strongest on record.
Even from half a world away, it nudges the weather in China too:
El Niño isn’t the only thing driving the weather, and these are forecasts, not things that have already happened.
Quick check
What actually happens in the Pacific during El Niño?
Like the fan over the bathtub running out of steam: the warm water it pushed aside sloshes back, and the rain moves with it.
