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Historical Archaeology

In 1892, Camilo Carillo, a navy captain from Peru, described how a strong current in the port of Paita was named as El Nino or “Christ child” because its effects were felt during Christmastime. Today, the phrase El Nino is employed to pertain to extremely strong and extended warm seasons that were implicated for the cycle of global climate change. The cycle consists of the increase and decrease in temperature of the eastern Pacific bodies of water which influences the changes in the air pressure in the Pacific region.

Another phrase was coined in the 20st century—Southern Oscillation, which refers to the increase in pressure in the eastern Pacific region, which in turn results in the lowering of pressure in the western Pacific region (Murphy et al. , 2007). Employment of statistical tools showed that these weather changes were associated with the Southern Oscillation, such as the Asian monsoon and it provided a means in forecasting seasonal changes in the weather.

During the 1960s, the strong correlation was established between the Southern Oscillation of the atmosphere and the El Nino phenomenon of the ocean, resulting in the compound event now known as the El Nino Southern Oscillation (ENSO). The El Nino Southern Oscillation has been determined to carry two conditions that are described as extreme. The warm event was earlier called El Nino, while the cold event was later coined as La Nina.

The use of terms related to the El Nino Southern Oscillation has been reported to be confusing because the phrase El Nino is often employed to describe issues relating to the phenomenon of El Nino Southern Oscillation. Global changes in the weather linked with the La Nina phenomenon, on the other hand, have been observed to be less prominent and in particular area, are likely to behave in the opposite way with regards to what is experienced with the El Nino phenomenon.

An El Nino episode has been determined to start with the presence of winds blowing in the easterly direction in the Pacific region, which is immediately opposite of the normal flow from east to west. In addition, these easterly winds blow with a weak intensity. The central zone for rain is also modified to the easterly direction, pointing towards to the central Pacific region, resulting in an extended dry season in Indonesia, the Philippines and most of the northern region of Australia.

The Pacific region carries a higher temperature by the west side of South America. The existing coastal upwelling in the South American coast is decreased and the nutrient-rich cold waters from the deep ocean do not appear at the surface of the sea. Due to the insufficiency of nutrients, the production of plankton is limited, influencing the rest of the food levels in the food chain, including the fishes and birds. The level of the sea on either side of the Pacific is also disturbed by this effect.

The behaviour of both the ocean and the atmosphere strengthens each other to an extent that a full-scale El Nino is created. The El Nino Southern Oscillations episodes are a strong factor which determines chances in the annual climate in several regions such as South America. During an El Nino, related changes in the weather are called teleconnections which are experienced even past the Pacific region. These are comprised by the increase in the temperature of both land and sea surfaces, alterations in the routes of storms and modifications in the patterns of precipitation.

A huge part of the effect of the El Nino Southern Oscillation on the human populated in experiences through the changes in rainfall in the form of the extremes of torrential rain or extended periods of drought. The climate changes were comprehensively explained in 1987 by Ropelewski and Halpert (1987; 1989) as earlier proposed by Walker (Walker and Bliss, 1932). The climate changes shown in Figure 1, pertaining to the El Nino, and in Figure 2, showing the La Nina, were generated by researchers of the United States National Oceanic and Atmospheric Administration (NOAA). Figure 1. Climate changes associated with La Nina (Source: NOAA, 1998)

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