El Niño vs. La Niña

Next to the seasons, El Niño is the biggest factor affecting human activity.

The Ultimate Conflict for Global Domination

Have we met before?
You've probably dealt with her before, but without realizing it. La Niña is best known as the little sister of the famous weather phenomenon El Niño.

You remember El Niño, right? Or least all of the hype a few years ago: excessive droughts and floods? Blame it on El Niño! Plane crashes and shipwrecks? It was El Niño! The Spice Girls and La Macarena? El Niño!

During the El Niño of 1997-98 we saw record-breaking temperatures, turning many into global warming believers. We also had relatively few hurricanes in the Atlantic, droughts in India, Indonesia, and Australia, floods in California, and a mild winter here in Wisconsin- all of which could legitimately be related to El Niño.

Between June 1998 and early 2001 we experienced the latest major La Niña event. During the fall of 1999, hurricanes Gert, Floyd, and Lenny blasted the Caribbean and thousands of people were drowned by an enormous cyclone in India in the Spring of 2000. The figure below shows that now in 2009, just like in 2000, we are either at the end of (or in the mddle of a big) La Niña which may have contributed to the nasty winter we have just had here the last 2 years in Wisconsin. Before we start blaming La Niña for Pokeman and the Teletubbies (and the collapse of the world's economy), let's take a look at the facts.

Sibling Rivalry
El Niño and La Niña are the two counterparts in what's called the Southern Oscillation. Sometimes shortened to just ENSO (El Niño Southern Oscillation), this phenomenon refers to the cyclic warming and cooling of the eastern and central Pacific Ocean. El Niño is the name for warm episodes, and La Niña is the name for cold episodes. These shifts in the ENSO have huge impacts on weather patterns around the globe.

A quick and simple way of looking the ENSO cycle is by using the ENSO Index. This index is a number generated by combining sea level air pressure, air and water temperature, wind direction and speed and cloudiness measured over the tropical Pacific. La Niña and El Niño events are indicated by distinctive changes in this index when compared to a seasonally adjusted average.

From looking at the graph above, we can see that conditions in the tropical Pacific usually cycle between cool (La Niña) and warm (El Niño). What's "normal" is a change between these two extremes. And one has to wonder whether global warming is the reason that the above graph is a lot more red than blue for the past 30 years.
So, now that El Niño has been away for awhile, what sorts of floods, fires and bad late-night comedy have resulted? Before we get carried away and start to blame every last mud puddle or dry spell on El Niño or La Niña, let's explain the phenomenon in more detail. Then, armed with enough information to be dangerous, we can explore how -- for better or worse -- it affects our climates and our lives.