El Niño and La Niña

What is the "El Niño" event?

Full name: El Niño-Southern Oscillation (ENSO). The warm phase of ENSO.
(Source for this inof and that which follows): http://en.wikipedia.org/wiki/ENSO

It is a global coupled ocean-atmosphere phenomenon. El Niño and La Niña are important temperature fluctuations in surface waters of the tropical Eastern Pacific Ocean. The name El Niño, from Spanish for "the little boy", refers to the Christ child, because the phenomenon is usually noticed around Christmas time in the Pacific Ocean off the west coast of South America. La Niña, means "the little girl".

ENSO is associated with floods, droughts, and other disturbances in a range of locations around the world.

Because El Niño's warm pool feeds thunderstorms above, it creates increased rainfall across the east-central and eastern Pacific Ocean.

The effects of El Niño in South America are direct and stronger than in North America. An El Niño is associated with warm and very wet summers (December-February) along the coasts of northern Peru and Ecuador, causing major flooding whenever the event is strong or extreme. The effects during the months of February, March and April may become critical. Southern Brazil and northern Argentina also experience wetter than normal conditions but mainly during the spring and early summer. ... Drier and hotter weather occurs in parts of the Amazon River Basin, Colombia and Central America.

What is the "La Niña" event?

La Niña is the name for the cold phase of ENSO, during which the cold pool in the eastern Pacific intensifies and the trade winds strengthen.

Financial implications:

Economic: Flooding: danger of loss to life and property.

Global warming and ENSO:

ENSO is a natural part of the Earth's climate, an important concern is whether its intensity or frequency may change as a result of global warming.

ANOTHER TAKE ON THIS: Source extracted: http://environment.about.com/od/globalwarming/a/elninolanina.htm

How is Global Warming Related to El Niño and La Niña?

Some scientists believe that the increased intensity and frequency—now every two to three years—of El Niño and La Niña events in recent decades is due to warmer ocean temperatures resulting from global warming. In a 1998 report, scientists from NOAA explained that higher global temperatures might be increasing evaporation from land and adding moisture to the air, thus intensifying the storms and floods associated with El Niño.


Another take on what’s happening is from Kevin Trenberth, a climatologist at the Colorado-based US National Center for Atmospheric Research. Trenberth believes that the Southern Oscillation may be functioning like a pressure release valve for the tropics. With global warming driving temperatures higher, ocean currents and weather systems might not be able to release all the extra heat getting pumped into the tropical seas; as such, an El Niño occurs to help expel the excess heat.

My thoughts on this: I can't see global warming, whatever the cause, not playing a role in the ENSO phenomenon. The climate systems now are all so "globalised" that an imbalance in one aspect may certainly cause a shift in another.

ENSO and Human Security - Here's a "fact sheet" from an event:

Guyana and La Niña in 2005

http://www.usaid.gov/our_work/humanitarian_assistance/disaster_assistance/countries/guyana/fy2005/guyana_fl_fs02_02-08-2005.pdf