El Nino: Introduction

El Nino

Global warming, raising temperatures are the things that pop up in our head whenever we have to talk about climate change. Do you know that 2015 is the hottest year in the recorded history? And the predictions tell that 2016 is cruising to beat it. NASA’s website says that earth’s average surface temperature has risen by an 1.0 Celsius since 19th century. The reason for which is carbon dioxide emitted from the human intervention. Apart from green house effect, another phenomenon that can affect global surface temperatures is El Niño. Let’s discuss what El Niño is and its repercussions in this article.

El Niño (pronounced as El neenyo) and is caused by a disruption to regular oscillatory behaviour of ocean currents and water movement cycles in pacific ocean. So, El Niño is a disruption to existing cycle of events. Before getting into how the disruption occurs, let’s discuss what exactly happens in a regular undisturbed case. As we have learnt during our Physics tuition classes, the density of water decreases as the temperature rises (above 4oC). So in an ocean the cold water sinks down due to high density and warm water floats on the surface. This is the same phenomena that results in the upward movement of fire or a hot-air balloon.

In the tropical region of the pacific ocean, movement of air from east to west direction is seen. This movement of air is in the form of winds and is termed as ‘trade winds’. The top layer on the water in the ocean is in contact with atmosphere and the motion of atmospheric air in the form winds pushes this layer from west to east. This motion of of warm water from west to east leads to collection of warm water on the west side of pacific ocean (near Australia). On the other hand at the eastern part of the pacific ocean, the warm water on the surface, that is drifted away by trade winds, is replaced with cold water arising from the lower layers. This replacement keeps the eastern side of pacific ocean cooler than that in the western side. Due to the accumulation of warm water at one region, and the resultant surface temperature difference across the ocean, the rate of evaporation at the west side of pacific ocean is higher compared with that in the east side. Due to this there is higher rainfall in the regions towards the west like Indonesia, India and other surrounding countries. A disruption to this is termed as El Niño and we shall discuss it in the next article.