Over billions of years, the planet Earth has been going through several climatic changes, which occur slowly and naturally. In recent times, however, Meteorology has identified some phenomena capable of modifying the planet’s climate in a much shorter period of time than normal events, such as El Niño and La Niña .
The El Niño , also called ENSO (El Niño – Southern Oscillation) is a climatic phenomenon that occurs every three to seven years on average, and is characterized by the abnormal rise in temperature of the ocean waters in the tropical Pacific region. Its occurrence changes the climate and changes the landscape of different regions of the planet.
It all starts with a change in the behavior of the trade winds. These winds, under normal conditions, move from east to west at a speed of approximately 15 m / s, raising the level of the Pacific off the Australian coast. Then, a transition zone between hot and cold waters is formed, and the trade winds drive the warmer waters to the west and cause the cooler waters to resurface in the east.
During the occurrence of El Niño, the speed of the trade winds decreases significantly and, as a result, the surface waters travel less and suffer an increase in temperature. With the atypical warming of the waters of the Pacific Ocean, between the coast of Peru and Australia, the entire atmospheric circulation system is affected, from the winds to the air masses. This situation leads to a much more intense evaporation, increasing the rainfall rates in certain places and causing severe droughts in others.
Brazil, for example, suffers many impacts in all regions in El Niño years. The North and Northeast regions are affected by long periods of drought, the average temperatures in the Midwest, South and Southeast regions increase, and there is still excessive rainfall in the latter region.
There is also another natural phenomenon that also occurs in the waters of the Pacific, called La Niña . This event happens less frequently and has characteristics contrary to the El Niño: trade winds blow at a higher speed than under normal conditions and, as a consequence, the surface waters of the Pacific Ocean off the Peruvian coast undergo a cooling, modifying the high and low zones. low pressure and causing changes in the direction of winds and air masses.
Like El Niño, La Niña also changes the climatic conditions of all parts of the planet. In Brazil, the impacts caused by La Niña are contrary to those caused by El Niño: rains are more abundant in the North and Northeast regions, with changes in the flow of rivers, while the South, Southeast and Midwest regions are affected by periods of longer droughts.
To this day, researchers still do not know exactly the causes that lead to the emergence of these climatic phenomena. Some theories link the triggering of El Niño and La Niña with the volcanic eruptions of certain regions of the planet, solar activities, sudden drops in temperature on the Asian continent, however, none of these hypotheses leads to a conclusive explanation.