UPSC Express

El Niño is a climate cycle in the Pacific Ocean with a global impact on weather patterns. The cycle begins when warm water in the western tropical Pacific Ocean shifts eastward along the equator toward the coast of South America. Normally, this warm water pools near Indonesia and the Philippines. During an El Niño, the Pacific’s warmest surface waters sit offshore of northwestern South America.It appears once every three to seven years, bringing drought, floods and other weather extremes to different parts of the world.

Changes associated with the El Nino are:

• Appearance of warm currents off the coast of Peru in the Eastern Pacific.
• Surface water temperatures off South America warm up because there is less upwelling of the cold water from below to cool the surface.
• The warm waters release excess energy (heat) into the atmosphere leading to weather changes all over the planet.

These changes due to El Nino have following effects:

• Increase in the temperature of water on the Peruvian coast by 10°C
• The distortion of equatorial atmospheric circulation
• Irregularities in the evaporation of sea water
• Causes extreme weather in some areas, like drought in India, Australia etc.
• Reduction in the amount of planktons which further reduces the number of fish in the sea
• Increased risks of diseases like malaria, dengue etc.

El Niño is one extreme in a natural cycle, with the opposite extreme called La Niña. The effect of climate change on the cycle is not yet understood, though some scientists think El Niño will become more common.