What is La Niña?

Year 2021 is that of La Niña. To understand La Niña we have to understand El Niño first. What is El Niño?

The El Niño effect is caused by the increase in surface temperature of the ocean on the Peru coast. During normal years, cold currents move from the Peru coast towards Australia. This cold water upwelling brings a lot of nutrients and planktons (food for fishes) from deep below, thereby increasing fish resources in Peru. These cold winds move from Peru to the warm western pacific pool in Australia, where it causes heavy rainfall.

Due to an unusual increase in temperature on the Peru coast, the normal condition is reversed, resulting in what we call the El Niño effect. What happens is that warm water does not allow the upwelling of cold water from deep below. It causes low pressure, and winds start to move away from Australia towards Peru. The phenomenon causes drought-like conditions near Australia and also affects the rainfall patterns. El Niño causes arid conditions both in India and Australia. But the effect will be seen across the globe.

La Niña is opposite of El Niño. In other words, La Niña years exaggerate the normal pattern, strengthening the normal situation, i.e., the appearance of the colder waters than average off the west coast of South America. A very strong La Niña can bring devastating news to regions.

For some farmers in Australia, La Niña’s plenty of rainfall boost the production of certain crops, while for others, too much of it damages their crops and fruits. The risk of flooding is also witnessed.

Overall, La Niña temporarily could lower down the global average temperature. 2021 would have been warmer without the cooling effect of two back-to-back La Niña events. But the increasing global temperature can make La Niñas and El Niños effects even more severe.