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Essay: El Nino and La Nina Phenomenon: Effects on Climate and Weather Worldwide

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Every few years, rumors about an often talked about, but little understood, weather pattern called El Nino begin to take over the news. As soon as signs of the season begin to show, scientists and forecasters begin desperately trying to predict what the next few months will bring.

El Nino was first noticed by Peruvian fisherman who discovered that every three to seven years, it became harder to fish in their usual fishing spots. The period almost always showed up around Christmas time. The Peruvians gave it an ironic name, due to its schedule, and began to call it El Nino, which means ‘the baby boy’ in Spanish.

As El Nino becomes more frequent and more powerful, the implications of this natural front become more serious. But, why are the worlds’ news sources so upset about the possibility of a desperately needed wet winter in California? Is that not a good thing for a state that seems to be in a perpetual drought?

What many people don’t understand is that El Nino is not just a front that brings heavy rains to the western part of the United States. El Nino is a naturally occurring weather pattern that causes disruptions all over the world. From Sydney to Los Angeles and even as far as London, it is not just the areas on the Pacific Rim that see both the positive and devastating effects of El Nino.

El Nino is inevitable, but it can be predicted. In order to best protect yourself, your home and your neighborhood from the damaging effects of this weather, it is best to understand it.



EL Nino is a metrological phenomenon marked by higher water temperature and lower atmospheric pressure. It usually originates in central and eastern pacific oceans and disrupts global climate patterns.

The meaning of El Nino in Spanish “ a naughty boy or boy of Jesus Christ”. The term EL Nino the tropical pacific. EL Nino has a great impact on the wind; see surface temperature and precipitation patterns in the tropical pacific. Adverse changes in these disrupt global climate patterns and wreak havoc worldwide in the form of floods and droughts.

Under normal circumstances the water of the eastern Pacific off Ecuador, Peru and northern Chile are surprisingly cold, as much as 100 C cooler than the water of western pacific. This part of the eastern pacific id teeming with fish, since here cold water, rich in nutrients, well up from the deep ocean. But once every five to ten years from December to March, the waters of the eastern Pacific warm up a little (280 C i.e.,40C higher than normal) which disrupts the upwelling of the rich cold water. This is turn disrupts the anchovy fishery, key to Peruvian economy. This phenomenon is called EL Nino since it starts in December.

EL Nino is not a regular events as it takes palaces once every on the average. But when it occurs, the local environment suffers from enormous disruption. The 1982 flood in Peru which caused losses worth US 2 billion dollars, failure of the Indian monsoon in 1987 and southern Africa drought have been linked to EL Nino.


Scientist argue that Pacific warming leads to increasing evaporation at the sea surface,warming the atmosphere. The warming of the tropical atmosphere triggers signals whose ripples are felt by climates of distant places . But what causes the tropical pacific to warm up is still a mystery. Some suspect the green house effect. Climate models that recon the increase in green house gases also point to warm up tropics.

19thcentury’s wrost drought in South Africa during 1991-92 was a direct consequence of ENSO. Grain production in the region fell from 11 million metric tonnes to less than 5 million metric tonnes.

Australian farmers warned 6 months ago of a possible drought sold of cattle in 1997 and changed planting plans to minimize the losses.

Failing to respond to climatologists’ warning of an EL Nino induced drought proved expensive to the South African government and humanitarian aid organization world wide.

About 37 countries are facing food emergencies and 31 countries had faced food shortage towards the end of 1997. The food shortage are mainly because of the effect of El Nino . Reports suggest that Eastern Africa has suffered serve loss of crops and livestock because of droughts and floods . Somalia experienced a sharp decrease in the production of crops during 1997-98. In Uganada,excessive rains reduced the recently harvested 1997 second season crops . Southern Africa has also experienced a major crop loss due to excessive rains and prolonged dry spells.

North Korea and other countries are already facing a grave food crises and mainly depending on food aid to survive . El Nino related droughts have affected cereal production in Indonesia china and Philippines.

Willie smith head of the Wanariset Samboja primate refuge which currently harbours 150 orang-utang rescued from the fires ,said that the jungle is back and bare . There is no fruit ,no leaves ,no bark . There is nothing for them to eat.

More of Brazil’s forests are now enveloped in fire and smoke than ever before. In a dry EL Nino year the savannas in the state of Roraima, left parched by the worst drought in history now face the wrost ever blaze burning as wide as over 5 kms . Deforestation and industrialization have resulted in the loss of over 12.9% of pristine Amazon rainforests. There was no rain April 1998. Meteorologists blame it on the EL Nino phenomenon. Fire experts believe that until it rain the fires cannot be contained.

The meteorologists monitoring authorities in Singapore say that the situation is grave both in the borneo islands and in many parts of Malaysia. A shift in the direction of wind is also bringing the haze to Singapore which recorded upto 80 on the Pollution Standard Index from an earlier average of about 30 to 40.

During 1997 crises none of these countries were prepared for such environmental disaster. Even in 1998 these countries are not in a position to afford the cost of preventing fires. 1998 environmental crises and the haze in South- East- Asia could overshadow the economic crises in the region .El Nino freak weather has certainly played its parts in causing drought and famine in Sudan. According to World Food Program about 35000 people are facing imminent danger .

Climatologists believe that 1999 will not be as warm as 1998. According to Australia Bureau of Meterology the average temperature in 1998 was 22.540C which was 0.730C higher than the average between 1961 and 1990. In fact each year of the decade has been hotter than the years between 1961 and 1990. This is now on the track to be the warmest decade since reliable records have been available in Australia. The hot weather in 1998was to some extent due to the warmth that typically occurs at the end of an El Nino episode. It is also the culmination of long term warming trend that has been evident since the 1950. Through El Nino reappears regularly it has never caused such damage to the US. Several rain storms recently battered California whereas tornadoes ravaged several countries,killing atleast 38 people and injuring nearly 300 others. Rain storms have also taken a toll on nearly 6500 cows in southern California.

According to a Delhi based International Development Research Center,a rise in temperature by 10C in 1987 corresponded with an increase in the number of malaria cases by 33.7%. the El Nino effect is also stated to be a cause of great ill health. Temperatures in the Indian pacific and Atlantic oceans are reported to have gone up in the last 10-12 years. Even the polar ice caps registered a rise of 10C during last decade.

• El Nino has caused warmer and stronger storms in Canada and Alaska.

• El Nino has caused more winter rain in Mid West in central US.

• El Nino has caused floods in Peru and Bolivia.

• El Nino has caused droughts in Brazils.

• El Nino has caused warmer weather.

• El Nino is responsible for warmer sea in Northwestern Pacific which leads to typhoons.

• El Nino is responsible for weak monsoon in Asia.

• El Nino is responsible for several droughts in Australia causing erosion ,crop failure and forest fires.

• A historical record indicates that El Nino events have coincided with droughts and floods in various parts of India.

• At least 50% of El Nino events in the have been associated with droughts in India. These include droughts years like 1918,1965,1972,1982 and 1997.

• El Nino years followed by droughts in India include 1877,1899,1905,1911,1918,1928,1941,1951,1965,1972,1982,1987 , ,2002 and 2015.

• It has been nearly 4 years since the end of destructive 1997-98 El Nino which was followed by three years of La Nina ,a cooling weather pattern in the eastern tropical Pacific.

• Historically El Nino episodes have occurred every two to seven years. The El Nino event in 1997-98 the most intense in the world history so far, had killed 24000 people across the globe and caused a loss of 34 US million dollars.


El Nino and La Nina are accompanied by swings in atmospheric pressure between the eastern and western Pacific known as Southern Oscillation. These phenomenons are collectively known as ENSO. The general mechanism underlying ENSO involves large scale ocean atmosphere interaction and equatorial ocean dynamics. But each El Nino and La Nina is unique in the combination of its strength, duration and pattern of development.

Drought is among the most commonly recurring natural disaster in the world. In India it upset the country’s food security by seriously affecting agriculture, which is heavily dependent on the monsoon. In order to predict drought or such occasions, some researcher has provided evidence to show link between the drought and El Nino/southern oscillation (ENSO) phenomenon. There is however a growing agreement between International scientific committee that ENSO phenomenon has links with extreme weather events like cyclones, flood, droughts etc.

Although most of the studies suggest some links between ENSO event and deficient summer monsoon rainfall over India, researchers have selected the ENSO years on the basis of different criteria, one among these in Sea Surface Temperature Anomaly (SSTA) over eastern Pacific.

The drought years have also been identified on the basis of long time rain fall data series annual, seasonal and homogenous regions of India. On the basis drought have been as mild drought, if the rainfall deficiency lies between 1.0 to 1.24 SD (standard deviation). For moderate drought the rainfall deficiency lies between 1.25-1.4 SD. For serve drought, it lies between 1.5-2.0 SD. For phenomenal drought, the rainfall deficiency lies about 2.0 SD.

In India there have been 23 occasions when summer monsoon drought has occurred and the rainfall deficiency has been found to be 1.0 SD or more. Of these 17 years witnessed moderate drought , 14 severe drought and only four phenomenal droughts(1877,1899,1951 and 1972) and all these happen in ENSO years. The frequency of drought was more rapid during 1899-1920. It decreased sharply during 1921-1960 and again increased from 1961-1990. Despite three ENSO events in 1925,1941,and 1951,the period 1921-1964 did not witness a single serve or phenomenal drought. there are four years since 1871 till the present day that India as a whole suffered from monsoon rainfall deficiency ranging between 25-49% of the normal. There is no year on record on the all India scale when the deficiency was more than 50%.

During this period atleast 21 ENSO events occurred. The west central and south peninsular regions have far fewer cases of droughts under moderate and above classes than on all India basis. Phenomenal drought in the north west region occurred in 1987 after an interval of 69 years , in the west central region in 1972(after an interval of 31 years), in the central north region in 1966(afteran interval of 89 years), over the north east region in 1992(after an interval of 96 years) and over the south peninsular region in 1952(after an interval of 34 years).

It has been found that of the 23 drought years , 11 years (1873, 1901, 1904, 1920, 1966, 1968, 1974, 1979, 1985,1986and 1991) are not associated with ENSO episodes . This also indicate that ENSO is not the sole cause for drought occurrence in the country the performance of the Indian monsoon may depends on many atmospheric oceans and terrestrial conditions.

The year 1880 , 1891, 1896, 1902, 1925, 1969, 1983, 1992 and 1998 were ENSO years were not associated with droughts in India . During these year monsoon rain were either on the positive sides of the normal or did not show any significant departure from the normal . For example , despite the super ENSO of 1998 , India experienced more than 26% rainfall from the normal and the monsoon was considered excellent. This again raises question about links between in ENSO and monsoon.

Since standard deviation and normal rainfall deficiency over differentregions differ considerably , the probability of occurrence of phenomenal drought (despite ENSO event) on an all India basis is very low about once is 30 years and the phenomenal droughts of 1972 occurred after a gap of 54 years however , there is no uniform cycle trend of occurrence of drought on an all India and religions basis.

Irregularity in the ENSO cycle can be seen in:

• Observation through instruments dating back to the middle of the last century and

• In data collected from late sediment, coral growth rings and ice core studies going back hundreds or even thousands of years.

So in principle, it should not be surprising that an unusually strong El Nino occurs even so often. The two phenomena El Nino/ southern oscillations are atmospheric and oceanic parts of climate fluctuations . Although it involves only one fifth of the circumference of the planet , it transform weather around the globe. It has been estimated that about 60000 people died in just one region of India from the epic drought of the year 1789-1793 El Nino. The evolution of ENSO exhibits irregularities from one cycle to another. El Nino now generally refers to the warming of tropical pacific basin that occurs roughly every two or seven years in association with a weakening of the trade winds. The flip sides of El Nino , La Nina , is characterised by stronger than normal trade winds and usually cold sea surface temperatures in the tropical pacific

1.3.1 On the basis of above discussion, the main conclusion are :

• Drought occurrence may be frequent but has no cycle trend.

• ENSO exhibits irregularities from one cycle to another.

• The existence of an ENSO phenomenon is not sure indication of monsoonal droughts , because it has not performed consistently for the prediction of a monsoonal droughts.

• The various classes of droughts might be associated with other oceanic , atmospheric and terrestrial conditions, but ENSO is one of the factors .

• ENSO is a sure sign of that there will be no excess rainfall. With some expectations almost all ENSO years are associated with deficient rainfall. Moreover , all four phenomenal droughts have links with ENSO events which have a significant modulating effect on Indian monsoon.


Scientists claim to have solved the mystery of links between El Nino and monsoon in India, a development that can lead to more accurate forecasts . El Nino , which means the little boy in Spanish, is an abnormal warming of the pacific ocean.

Normally the temperature of surface water in the western pacific ocean is 6-8°C higher than in the eastern Pacific Ocean. But during El Nino , this reserves ,changing the atmospheric pressure on either side of the ocean.

An analysis of rainfall records of the past 132 years has revealed that severe droughts in  the country have always been accompanied by El Nino events but not all such weather conditions have led to the failure of monsoon. The El Nino events in 1965, 1972, 1982, and 1987 were bad for India but the 1997 El Nino , despite being the strongest in the century , did not affect monsoon. This led many experts to conclude that the link between monsoon and global weather event was wearing off . But the Indian Meteorological Department still takes into account El Nino for forecasts. According to the scientists ,India gets affected when warm Pacific temperature typical of El Nino extend westwards into Central Pacific Ocean. The El Nino events with warmest sea surface temperature anomalies in central equatorial Pacific are more effective in focusing drought producing subsidence over India than events with warmest sea surface temperature in eastern equatorial Pacific, the scientists say. For their research , the authors examined 23 strong El Nino years for atmosphere and ocean conditions, that distinguish 10 Indian monsoon droughts from 13 droughts free years. They found what whenever monsoon failed , the sea surface temperature was high in the central Pacific Ocean . The authors also noticed that the question of whether this connection will change as a consequence of global warming will continue to be investigated.  The results of this study indicates that human induced ocean warming could have material consequences for the monsoon intensity over India.


According to climatologists at the NASA, worst outbreaks of the disease are closely related to the climate event El Nino. These outbreaks occur one to three months after the warming of the tropical eastern Pacific Ocean that is associated with El Nino. If confirmed , the findings could enables health workers to stave off future epidemic before they begin . Scientists have strong evidence that there is a close relationship between climate and Bartonellosis, which causes life threatening anemia . There is a chronic form of the disease that manifests itself in blood filled, wart-like skin lesions. Bartonellosis appears to be spreading from the mountain valleys of Peru into other regions of Andean South America. According to researchers the disease is transmitted to humans by the bite of sand flies, much as malaria is by mosquitoes. Since the acute disease is fatal in 40% of cases, if left untreated,  it is important to identify the factors behinds its spread. The deadliest recent outbreak was during the South American summer and fall months of dec.1997 to May 1998. Since the 1997-98 season was also the strongest El Nino event of the 20th century, the scientist compared sand fly breeding observations with weather data from NASA satellite. They noticed that extremely high numbers  of sand flies were collected during 1997-98 season and that season had double the average numbers of Bartonellosiscases. The disease also spread to the Southern part of the country , where it had not been see before.

The data led scientists to believe that El Nino was the dominant factor of the epidemic. Since indications of El Nino can be seen by satellites months before it affects the sand fly breading season in South America , the scientists believe they can serve as an advance warning of an approaching epidemic year.


According to a recent study conducted by Netherlands based researchers, El Nino can help recover degraded land. It could be harnessed to recover land that has been degraded by overgrazing and desertification.  Arid areas are so badly degraded that they cannot recover by themselves , even when grazing animals are removed . But coinciding this with El Nino’s arrival, which occurs once in every two to seven years and leads to a dramatic increase in rainfall in some normally dry regions, could provide the impetus to make these areas fertile again . Experts , how ever , say that idea is good in theory , but how it would work in practice . One problem is that El Nino is unpredictable and one may only get a few weeks warnings. But according to researchers many ecosystem can be stable under a number of different sets of ecological conditions . Each such state , such as woody ,herbaceous or bare soil ,is relatively stable and can withstand fluctuations in the weather. But a dramatic shift in environmental conditions , such as the amount of grazing or rainfall , can push each system over a threshold into a different state, where it remains even if ecological conditions return to what they were before . El Nino could give the much needed push for the land to jump over this threshold.  Land owners could harness the power of El Nino to shock their lands into recovery.  If farmers stopped grazing for just one season during El Nino the combined effect of increased rainfall and reduced grazing could convert the land into a new ,stable ,recovered state.



Last big El Nino occurred in 1982-83, when there was no forecast for the event . Climatologists did not know what was the happening then and they did not have any idea about the regional and international impact of El Nino. 15 years later, the record breaking 1997-98  El Nino thought climatologists a lesson and new forecasting techniques enabled them to predict at the beginning of the year 1997 that the tropical Pacific was about to heatup  after two years in which the water had been slightly cooler than normal , and then to give three to six month warming to consequent weather changes in the most vulnerable parts of the world.

The forecasters announced that this El Nino will be one of the top three events in US and region such as California would be at particular risk. In fact ,1997-98 El Nino event caught the scientific community by surprise.  Although several computer maodels had predicted that the tropical Pacific would become warmer in 1997, warming in almost every case were too weak and developed too slowly . Once El Nino was underway the forecaster quickly adjusted their computers taking account into consideration its unexpected severity. Then they predicted its impact for different parts of the world over the next few months. But just as they had missed El Nino’s rapid onset, all the computer models failed to predict the abruptness of its Departure in May -June , 1998. If forecasters are to do better next time and provide reliable predictions of global weather patterns year ahead, they need to understand better the extremely complex changes in ocean currents and atmospheric circulation that underline the Southern oscillation (The technical name of the cycle between El Nino and La Nina).

Successful global forecasting requires not only a computer model of the complex interplay between wind and waves , but also an understanding of the manner in which southern oscillations interact with other , less obvious climate cycles in the pacific ocean and elsewhere.

2.1.1Climatologists usually make two kinds of forecasts.

• Statistical forecast , based on historical records

• Dynamic forecast, based on numerical models of the coupled ocean atmospheric system

Statistical forecasts correlate observed weather conditions with indices of the occurrence of El Nino. For this, the sea surface temperature (SST) in key regions of the equatorial Pacific are used to define an El Nino period.

The El Nino and SOI are opposite in phase. A negative SOI indicates low pressure in the Eastern Pacific and high in the Indonesian region.

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