[MUSIC]
El Niño is everywhere in the news right now, but the way people talk about it, you’d
think it’s something Michael Bay cooked up:
The Season of Death and Destruction!
El Niño May Eat The Blob!
The Bruce Lee of El Niños!
No, The Godzilla of El Niños!
Wow, that escalated quickly. Okay, let’s take a chill pill and see what this El Niño
thing is really all about.
[MUSIC]
El Niño is, of course, Spanish for
"The Niño"
A few centuries ago, fishermen in Peru noticed every so often the water in the Eastern Pacific
would get warmer. It didn’t happen every year, but when it did, it always happened
close to Christmas, so they named this phenomenon for the “Christ Child”, or El Niño.
To understand how El Niño works, think of the Pacific Ocean like a giant bathtub.
Thanks to Earth’s rotation and the Coriolis effect, winds near the equator usually blow
east to west, and just like when you blow across a cup of tea, that wind actually pushes
the water, so much so that sea level in Indonesia is usually a half meter higher than in Peru.
As that water near the surface, warmed by the sun, is forced west, it causes deep, cold
water to rise in the east to replace it. That means warm over here, and cold over here.
If those east-west winds blow harder, warm water is pushed way west and the eastern
Pacific gets even colder. We call this La Niña.
But if those east-west winds weaken, there’s less cold upwelling, and that huge mass of
warm water ends up sitting just off the coast of South America. That’s El Niño.
El Niño can hold a ton of energy.
The 1997 El Niño moved 35 million million billion Joules of energy into the eastern
Pacific, as much as 160,000 Tsar Bombas, 100 times the energy used by everyone on Earth
in a year, 1/14th as much as the meteor impact that killed the dinosaurs!
That’s a lot, and when that energy gets transferred to the atmosphere, where weather
happens, it can have effects that reach around the world.
The El Niño during the Northern Hemisphere winter of 1997 and 1998 was the strongest
ever on record. Rain and mudslides in California and Peru killed dozens and left thousands
homeless, Kenya’s annual rainfall was 40 inches above normal. And on the other side
of the Pacific, Indonesia had massive droughts, temperatures in Mongolia hit 108˚ F.
And while El Niño usually means a quieter Atlantic hurricane season, it can mean more
and stronger storms in the Pacific. In 1997, Hurricane Pauline dumped 27 inches of rain
on western Mexico in a single day.
With so much money and life at stake, it would be nice to be able to predict El Niños.
or is it Los Niños… and their effects far in advance. WIll California finally get some rain?
Will the Northeast get less snow? We just don’t know.
For one thing, an El Niño event can show up anywhere from every 2 to 7 years, or sometimes
not at all. It’s less of a cycle and more of a… periodic-sometimes-quasicycle.
Yes, that's a technical term.
Now, I know it’s easy to joke that weatherman don’t always know what they’re talking
about.
Truth is, for systems like El Niño, prediction isn’t just hard, it might be impossible.
One day 1961, meteorologist Edward Lorenz was running some mathematical weather simulations
on his computer. He needed to repeat one he’d done earlier, so he re-entered his variables
by hand and pressed start. Only when he looked at the results, they were completely different
than the first time.
Lorenz was baffled. He checked his work, and realized that he had accidentally rounded
one of his variables. Instead of .506127, he had left off the last three decimal places.
This tiny, tiny difference, just a few ten-thousandths of a unit, had completely changed the result.
This accident gave birth to chaos theory.
"I'm still not clear on Chaos"
"Oh, it simply deals with predicability in complex systems"
Lorenz had stumbled across the answer for
why no matter how advanced our computers or models may get, we can never accurately predict
the weather more than a few days out. In any system, the tiniest change in initial conditions
could lead to completely different outcomes, and the farther out you try to look, the more
those tiny uncertainties are amplified.
It was this realization that led Lorenz to ask his now-famous famous question: “Does
the flap of a butterfly’s wings in Brazil set off a tornado in Texas?”
That so-called “Butterfly Effect” doesn’t mean that butterflies are literally causing
tornadoes… or El Niño, only that the tiniest change can have a huge impact down the line.
This simulation tracks the movements of a particle according to three simple equations.
The equations–the rules–never change, but we can see that if we alter the initial
condition just the tiniest bit, over time we end up with two very different paths.
Our atmosphere is just about as complex a thing as you can imagine, an enormous fluid
made up of countless individual particles, each of them depending on variables like sunshine,
temperature, atmospheric pressure, wind, humidity… All of those particles obey the laws of physics though,
and we have equations to describe those laws, and huge powerful computers to put it
all together.
The thing is, even if we were able to measure what every particle in the atmosphere was
doing at any moment, for every measurement there is that tiniest built-in uncertainty,
and Lorenz’s chaos theory tells us that this uncertainty, once we go out a few days,
even a week, is amplified into no more than a lucky guess.
So don’t blame the weatherman. Uncertainty is simply built in to our world, our universe,
and that’s okay.
We may be able to predict what the weather’s gonna be like tomorrow, but as for El Niño?