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Within our lifetimes, the most dramatic phenomenon linked to climate change is the anomalies in the Pacific Ocean known as the El Nino Southern Oscillation, dubbed as ENSO (Cane 2004). This phenomenon has been taking place even as far back as 10,000 years ago, during the Holocene period (Outavas et al. 2006). However, the El Nino didn’t receive much public attention until 1997-98 when Peru and Ecuador experienced heavy floods, Indonesia and Australia faced ghastly droughts and Southeast Asia had to shut down some of their airports due to the thick clouds of smoke arising from forest fires in the region.

In Spanish, ‘El Nino’ directly translates to ‘Christ Child’. The seasonal arrival of warm water in the Pacific Ocean during the month of December prompted the South American fishermen to call it El Nino. El Nino and La Nina (‘Little Girl’) are opposite phases of the ENSO cycle which describes the variations in temperature between the ocean and atmosphere in the Equatorial Pacific. El Nino is the warm phase while La Nina is the cold phase of the ENSO.

An upwelling or upward movement of ocean water can mix upper levels of seawater with lower levels bringing cool and nutrient rich water from the bottom of the ocean to the warmer surface where it supports large populations of phytoplankton, zooplankton, fish and fish eating seabirds. Every few years normal upwelling in the Pacific Ocean is affected by ENSO. During an ENSO prevailing winds called trade winds blowing east to west weaken (reverse direction). This allows warmer waters of the western Pacific to move towards the Western coast of South America which suppresses the normal upwellings of cold nutrient rich water.

This leads to a disruption of the marine food chain. Warm waters send fish to cold deep water. Seals are left to suffer as they’re deprived of their food source. Similarly fishing economies of countries like Peru and Ecuador also dwindle as a result of this.

Image Source: Inter Press Service News Agency. Woman stands in front of drought-affected rice paddy in Sri Lanka.

Now let us have a look at how climate change relates to the above mentioned phenomenon. Climate change refers to any significant change in the measures of climate lasting for an extended period of time. It includes changes in the atmospheric temperature, precipitation and wind patterns. One of the contributing factors to climate change is global warming. This ongoing increase in the average global temperature at the earth’s surface is caused by an increase in the amount of greenhouse gases, such as carbon dioxide (CO2), in the atmosphere.

A rise in global temperatures leads to an increase in sea surface temperatures thereby facilitating the El Nino phenomenon. The relationship between El Nino and climate change is somewhat cyclic. Oceans act as carbon sinks; that is, they capture and store carbon as dissolved CO2. CO2 dissolves more readily in colder waters. During El Nino there is an increase in sea surface temperatures. This causes less CO2 to be dissolved in the oceans. As a result there’s more CO2 in the atmosphere which causes global warming and this inevitably leads to climate change. Bush fires which occur as a result of the El Nino effect release large amounts of CO2 which again leads to global warming.

A man teaches his son how to prepare rice fields using a tractor, near the Sri Lankan capital Colombo, in this April 2010 file photo. REUTERS/Andrew Caballero-Reynolds

ENSO is one of the most important phenomena related to the global climate. This is because of its impact on the atmospheric circulation which ultimately leads to variations in temperature and precipitation. The equatorial Pacific climate behaves as a ‘coupled system’. This is because the state of the ocean and the state of the atmosphere depend on each other.

El Nino events are increasing in both intensity and frequency, resulting in increased extreme weather events. In the recent past, Sri Lanka has experienced very hot weather, with certain regions reaching record temperatures, and we have also had very high precipitation.

These extreme events would cause severe damage to agricultural crops thereby depriving farmers of a stable income. Fishermen would also face a grave situation when heavy precipitation prevents them from going to sea. Natural disasters such as floods and landslides would become more frequent leading to loss of lives and property, as we saw very recently. Other consequences include spread of diseases, road obstructions, hike in food prices and damage to infrastructure.

Climate change cannot be prevented, but its impacts can be reduced. It’s high time we became more environmentally conscious because there may come a day when the climate may change so drastically that this planet would no longer be inhabitable.

Charuni Pathmeswaran

About Charuni Pathmeswaran

Charuni has just completed her degree in Environmental Science at the University of Colombo, Sri Lanka. She contributes to the Students’ Blog which gives her a platform to write about local and global environmental issues. For her undergraduate research she studied the impact of extreme weather events on coconut productivity in selected locations of Sri Lanka. She believes that education is the most important tool in adapting to climate change.