Introduction to ENSO events
As you know from the Tropical Circulation lesson, climate in the equatorial tropics is dominated
by the ITCZ and is characterized by somewhat monotonous weather. You also learned that the
tropical regions immediately poleward of the equator are more dramatically affected by
migrations of the ITCZ, as well as the transient oceanic and atmospheric disturbances we will
discuss in this lesson. Not only will we talk about these disturbances and their connections
) to weather and hazard anomalies worldwide, we will also take a look at
how people have learned to live with them.
How is it that El Niño is a phenomenon of the tropical Pacific Ocean, yet it frequently makes the
news as having an impact on local weather all over the globe? Why did we only begin to really
hear about El Niño in the early 1980s when South-American fisherman have recognized it since
at least the 1800s and the Inca recognized it well before that?
How in the world can some researchers blame El Niño for coastal erosion in California, bushfires
in Australia, malaria outbreaks in Africa, drought in India, death of over 10% of the world's coral
in one year, an increase in hurricane activity, a decrease of activity in "Tornado Alley," and
fluctuations in natural gas prices? Where does La Niña come into play?
How have people adapted to these oceanic and atmospheric phenomena? Is forecasting Los
Niños possible or even worthwhile? What were the most costly El Niño and La Niña events in
ENSO events: El Niño and "relatives"
El Niño, La Niña, El Viejo, Southern Oscillation, North Atlantic Oscillation, Atlantic ITCZ
Oscillation, Warm Pool Oscillation, Pacific Decadal Oscillation.
...and that's just the beginning.
What do they all mean? Are they related?
The bottom line
They are all
massive, cyclical, climatic anomalies
that affect the global environment. Learning
more about these anomalies may help scientists explain abnormal/drastic changes in our weather
and other related phenomena (e.g., catastrophic floods, mass wasting, droughts, global warming,
wildfires, biotic fluctuations, wine production in western Europe, early springs in Washington
In this section of the lesson, we are going to explore
(LN) and the way they impact us. These three anomalous phenomena are featured
in this lesson because they are examples of transient oceanic/atmospheric disturbances that take
place in the tropics, yet affect global environmental conditions. These phenomena have a
significant impact on our lives whether we realize it or not.
What are El Niño, Southern Oscillation, and La Niña?