Saturday, January 22, 2011

El Nino/La Nina

Indian Policy intends to publish brief backgrounders on topics of current relevance. This is the first in the New Decade. 

Climate Change and Global warming are heavily discussed environmental buzzwords of current interest. An average citizen seems to be more aware of these terms now, than say ten years ago. Melting glaciers, increasing sea level, hotter summers and colder winters – all are in some way or the other related to these.

The recent phenomenon of massive floods in Australia, Srilanka and Brazil have been said to have occurred due to El-Nino. Let’s try and understand some key concepts related to it.

El Nino:

El Nino is the warming of water in the Pacific Ocean. El Niño is Spanish for "the boy" and refers to the Christ child, because periodic warming in the Pacific near South America is usually noticed around Christmas.

The Effects of El Niño:

According to the National Oceanic and Atmospheric Administration (NOAA), the El Niño part of the cycle involves warmer-than-usual sea temperatures, great amounts of rainfall (in the northern hemisphere) and low atmospheric pressure. The most extreme results of an El Niño event have included flooding from Ecuador to the Gulf of Mexico, massive marine life die-offs in the Pacific, hurricanes in Tahiti and Hawaii, and concurrent droughts in many other parts of the world from Southern India to Australia to Central America.

Southern Oscillation:

The Southern Oscillation is the atmospheric component of El Niño. This component is an oscillation in surface air pressure between the tropical eastern and the western Pacific Ocean waters. The strength of the Southern Oscillation is measured by the Southern Oscillation Index (SOI). The SOI is computed from fluctuations in the surface air pressure difference between Tahiti and Darwin, Australia.

El-Nino and Southern Oscillation are together known as ENSO.

El Nino Modoki:

El Niño "Modoki" and Central-Pacific El Niño The traditional Niño, also called Eastern Pacific (EP) El Niño, involves temperature anomalies in the Eastern Pacific. However, in the last two decades non-traditional El Niños were observed, in which the usual place of the temperature anomaly is not affected, but an anomaly arises in the central Pacific. The phenomenon is called Central Pacific (CP) El Niño, "dateline" El Niño (because the anomaly arises near the dateline), or El Niño "Modoki" (Modoki is Japanese for "similar, but different").

The effects of the CP El Niño are different from those of the traditional EP El Niño—e.g.,the new El Niño leads to more hurricanes more frequently making landfall in the Atlantic.

The strongest such Central Pacific El Niño event known occurred in 2009-2010.

La Nina:

La Nina is the cooling of water in the Pacific Ocean. The name La Niña originates from Spanish, meaning "the girl". It has also in the past been called anti-El Niño, and El Viejo (meaning "the old man").

The Effects of La Niña:

In contrast, cooler sea temperatures, high atmospheric pressure and drier air characterize the La Niña phase of the Southern Oscillation. During La Niña, currents bring nutrients up from the deep water, providing feast, rather than famine, for marine organisms. And accompanying strong winds blow moisture away, making for cloudless skies and dry conditions in equatorial countries from the International Date Line east to South America.

You may refer to the following for more research on this topic.

Indira Mukherjee is keenly following issues related to environment at the moment. Share your views and concern on the same with her at 


  1. good information and well googled stuff...
    as a geography student..I always thought...whenever...there is comparision...we compare it with records of early 20th 1913..or etc..well didnt we have such geographic phenomena that time too?...we did have..climate change..even before mankind..its no preventive solution but post calamity actions can reduce the effect...

  2. Please explain the effects of above three phenomena on Indian sub continent.

    Also I am curious to know the basic thing about Global Warming i.e why CO2 is transparent to incoming short waves while it is opaque to outgoing long waves.

    I googled it but could not find the reason.