Parameter Tree:

An irregular variation of ocean current that from January to March
flows off the west coast of South America, carrying warm,
low-salinity, nutrient-poor water to the south. It does not usually
extend farther than a few degrees south of the equator, but
occasionally it does penetrate beyond 12 degrees S, displacing the
relatively cold Peru Current. The effects of this phenomenon are
generally short-lived, and fishing is only slightly
disrupted. Occasionally (in 1891, 1925, 1941, 1957 - 58, 1965, 1972 -
73, 1976, and 1982 - 83), the effects are major and prolonged. Under
these conditions, sea surface temperatures rise along the coast of
Peru and in the equatorial eastern Pacific Ocean and may remain high
for more than a year, having disastrous effects on marine life and
fishing. Excessive rainfall and flooding occur in the normally dry
coastal area of western tropical South America during these
events. Some oceanographers and meteorologists consider only the
major, prolonged events as El Nino phenomena rather than the annually
occurring weaker and short-lived ones. The name was originally applied
to the latter events because of their occurrence at Christmas time.

Interacting parts of a single global system of climate
fluctuations. ENSO is the most prominent known source of interannual
variability in weather and climate around the world, though not all
areas are affected. The Southern Oscillation (SO) is a global-scale
seesaw in atmospheric pressure between Indonesia/North Australia, and
the southeast Pacific. In major warm events El Nino warming extends
over much of the tropical Pacific and becomes clearly linked to the SO
pattern. Many of the countries most affected by ENSO events are
developing countries with economies that are largely dependent upon
their agricultural and fishery sectors as a major source of food
supply, employment, and foreign exchange. New capabilities to predict
the onset of ENSO event can have a global impact. While ENSO is a
natural part of the Earth's climate, whether its intensity or
frequency may change as a result of global warming is an important
From: ""

Glossary: Carbon Dioxide and Climate,
1990. ORNL/CDIAC-39, Carbon Dioxide Information Analysis Center, Oak
Ridge National Laboratory, Oak Ridge, Tennessee. Edited by: Fred
O'Hara Jr.