Please explain the phenomenon called El Nino. What is its impact?
In 1500s fishermen along Peru’s coastline were shocked to see millions of dead seabirds washed up on the beach. The birds had died because of a decline in the fish population which was their main food source.
About the same time sailors noted changes in ocean currents and wind patterns. Since these abnormal conditions reached a peak around December the Peruvians called it El Nino meaning ‘little boy’ in honour of the infant Jesus.
An El Nino starts every three to seven years when a vast pool of warm water moves eastward in the tropical Pacific Ocean affecting air circulation and rainfall patterns over the world.
Under normal conditions there is a high-pressure condition over eastern Pacific Ocean and a low-pressure condition exists over western Pacific. This makes Trade Winds blow westwards from the high-pressure area to the low pressure one. The winds also push seawater west towards Australia and Indonesia. Sea surface is actually two feet higher around Indonesia than it is near the South American coast.
The water that blows westward is replaced by cold water from deeper levels and a vibrant ecosystem thrives on this cold, nutrientladen seawater that rises to the surface along the South American coastline. So the cool sea surface feeds a vibrant fishery in Peru and Ecuador. In contrast the sea surface near Indonesia (western Pacific) is hot and as water evaporates from the ocean, it creates clouds and brings normal rains to surrounding regions.
El Nino year
During an El Nino, the high and low-pressure conditions weaken and Trade Winds weaken too. This allows warm seawater around Indonesia to surge towards South America as the ocean sloshes eastwards, seeking to level itself out. The upward movement of cold water along South America stops and the fish die in huge numbers because they don’t get the supply of nutritious, cold water. This is often the most visible sign of El Nino.
Once the warm waters move eastward, the winds and currents change. This causes weather upheavals around the world bringing rains to the normally dry American coast and droughts to other parts. The El Nino in 1982-83, for instance, caused droughts in southern Africa, India, Indonesia and southern Peru. On the other hand heavy rains flooded Ecuador, Northern Peru and Cuba while hurricanes lashed Tahiti and Hawaii.
Global warming El Nino years tend to be warmer than usual and may lead to a global heat wave. But the reverse can happen too. Scientists explain that global warming could intensify El Nino if warm temperatures increased evaporation from land. The extra moisture in the air could strengthen storms and floods associated with El Nino. So while global warming could be driving El Nino, it in turn, could be raising global temperatures.
Serious concerns have been expressed about flooding in Bangalore and some reasons for this are encroachment of tanks and lakes by land sharks, lack of drainage and excessive rain. I have lived here a long time and I recall seeing heavy rains earlier.
But I have not seen such heavy flooding. I think that a major reason for flooding now is that buildings completely pave surrounding areas and there isn’t enough uncovered earth that can soak up rainwater.
The rainwater that cannot seep in through the ground collects on roads. In my own house, an old one in an old locality, there is some unpaved area and a short while after rains the water drains off. I think GT should discuss old building styles and traditions and ones that are followed today.
Many feel that 2005 is the date for Peak Oil and per capita availability will continue to fall. So there is an urgent need for a change in the style of living. We should be slowly moving towards a world that will be bicycle-powered, solar and wind-powered instead of one powered with combustion fuel. Where agriculture will be more oriented to natural fertiliser rather than petro-based. I think this topic will make an interesting read if GT decides to explore it.
Prof J G Krishnayya, Director
Systems Research Institute,
On October 23, 2005, I asked you about ways to decrease hardness of ground water. My question was answered in the November 30, 2005 issue of GT. Now based on your recommendations I’m trying to design a simple ion-exchanger, which can be used domestically. Thank you so much.
Indians need to know about the importance of sustainable development and a sound ecosystem. GT has been making positive and consistent efforts in this direction.
But your effort to sensitise reaches limited English-literate people. What about the masses who live in the rural and semi urban areas? As far as I know neither GT nor DTE is published in Indian regional languages and I think that they should be, so that more people can read these magazines.
Ambuja Cement Foundation
While I was working on the conservation of Indian wolf and the ecology of migratory birds I realised that there needs to be a change the mindset of people.
So I decided to work in a school. Since Environment Studies has been introduced recently we would welcome interaction from CSE to gear up our young environment messengers who will make a difference in their social environment.
Reema Pant, Academician
Welham Boys’ School