El Niño and the ENSO weather situation in the Pacific
What is El Niño and how does it work?
ENSO can be best viewed as an irregular oscillation between El Niño (the warm phase), La Niña (the cold phase) with periods of Neutral (non El Niño or La Niña) conditions in between.
In Australia for instance, it is the El Niño phase that receives the most attention due to its association with drier than normal conditions for eastern and northern parts of Australia. 3 out of 4 droughts in Australia occur during El Niño years.
The term El Niño translates from Spanish as “the boy-child”, a reference to the Christ child, that was first used by Peruvian anchovy fishermen. This term was traditionally used to describe the appearance, around Christmas, of a warm ocean current off the South American coast, adjacent to Ecuador and extending into Peruvian waters.
In Asia, El Niño can result in less monsoon rain and in seasonal changes.
Today, an El Niño event is defined as a change in atmospheric pressure between the equatorial Pacific Ocean and Indonesia. The result is that the atmospheric circulation weakens, seas around Australia cool, and slackening trade winds feed less moisture into the Australian/Asian region.
Each El Niño event is unique in terms of its strength and occurs about every 4 to 7 years and typically last for around 12 to 18 months.
El Niño events have in recent years increased in frequency and are often not interrupted by La Niña events (the opposite of this particular climatic seesaw).
A number of scientists say that these changes cannot be explained by natural causes. While scientific consensus is still out, Climate Witnesses in Fiji or in the Sunderbans are already reporting changes in their daily lives.
Source: WWF Factsheet on El Niño (unpublished)