Warming of the ocean
RAMESH SETH
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The El Nino effect can be detrimental to agriculture and marine life.
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THE EL NINO EFFECT: Can cause drought conditions.
At an executive meeting of The Solvent Extractors' Association in 1972, we discussed at length the effect of El Niño upon Europe's demand for Indian oilcakes. At that time we were informed about the El Niño effect in different parts of the world, on agricultural production and marine life. El Niño in Spanish means "the little boy". Actually, it used to refer to "Little Christ". But today it denotes a natural phenomenon. It is the abnormal warming of the Pacific Ocean in certain years. As this normally occurs around Christmas time, it has been named El Niño.
Normally, the temperature of the surface water in the western Pacific Ocean is six to eight degrees Celsius higher than in the eastern Pacific Ocean. But during El Niño years the temperature of the Eastern Pacific becomes six to eight degrees warmer than the western Pacific. This leads to a change of the atmospheric pressure on either side of the ocean.
The effect
Analysing rainfall records of the past 132 years has revealed that severe droughts in the country have always been accompanied by El Niño. The El Niño in 1965, 1972, 1982 and 1987 were bad for India.
According to scientists, India gets affected when warm Pacific temperatures typical of El Niño extend westwards into the central Pacific Ocean. "We show that El Niño 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 the eastern equatorial Pacific," says K Krishna Kumar, Indian Institute of Tropical Meteorology, Pune.
The study notes that the world's warming is greatest at high latitudes of the Northern Hemisphere and it is larger over land than over oceans. The enhanced warming at high latitudes is attributed to effects of ice and snow. As the earth warms, snow and ice melt, uncovering darker surfaces that absorb more sunlight and increase warming, a process called a positive feedback. Warming is less over oceans than land because of the great heat capacity of the deep-mixing ocean, which causes warming to occur more slowly there.
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