CREDITS:
Script and Voiceover: Aishwarya Iyer
Graphics : Sunny Gautam
Video Edit : Aishwarya Iyer
Executive Producer: Arnab Dutta
Based on an article published in Down to Earth by Akshit Sangomla.
ENSO or the El-Nino Southern Oscillation Phenomenon is a periodic variation in winds and sea surface temperatures over the tropical eastern pacific ocean. The warming phase is called El Nino while the cooling phase is called the La Nina phenomenon.
In a La Nina event, cooler than average sea surface temperatures prevail over the east and central Pacific Ocean. During the event, ‘trade winds’ are stronger than usual, pushing warm water toward Asia. These cold waters in the Pacific push a jet stream northward. This can lead to drought-like conditions in the Southern part of the US and cold/dry conditions in parts of the Pacific Northwest. So, the weather consequences of these winds differ.
In general the La Nina has a cooling effect on global temperatures. But, these weather consequences are changing now, which is being seen as evidence of a warming world. If the La Nina phenomenon extends for a long period of time, it leads to adverse effects on the weather.
From 1973-1976, the event was *37 months long. Whereas from 1998-2000, it lasted for **24 months. The current La Nina will also complete 24 months in ***August 2022.
Although we’ve seen long La Ninas in the past, its changing characteristics are the real cause of concern. Large parts of India did not experience a spring season at all this time. This was because a La Nina influenced north-south pressure pattern that normally causes excess rainfall and cold winters interacted with warm waves coming in from the rapidly warming Arctic region to prolong the heat waves.
During March, April and May the temperature anomaly of the eastern and central Pacific Ocean was 1.1 degree Celsius below normal. This is the second time since the 1950’s that the La Nina became stronger (cooler) in March-April-May than February-April. In India, this could extend the monsoon season like the last two years which could be devastating for agriculture. The drought in 40% of the US, drought in the Horn of Africa and southern part of South America could intensify with the continuation of the La Nina.
The NOAA also predicts that there is a 65% probability of an above average hurricane season for the Atlantic Ocean. A low wind shear (difference in wind speed and direction from near surface to the higher parts of the atmosphere) is conducive for the formation and intensification of hurricanes. A strong wind shear would have torn apart a hurricane from the top.
“Human induced climate change amplifies the impacts of naturally occurring events like La Niña and is increasingly influencing our weather patterns, in particular through more intense heat and drought and the associated risk of wildfires - as well as record-breaking deluges of rainfall and flooding,”
Petteri Taalas,
Secretary general of WMO
(During a press release on La Nina on June 10)
The changing consequences of the La Nina implore a more careful examination of the event in an increasingly warming world.
15 июн 2022
