The ‘triple dip’ La Niña and its likely impact on India

The ‘triple dip’ La Niña, and its likely impact on India

Subject : Geography

Context:

Introduction–

• La Niña refers to the ENSO phase in which sea-surface temperatures are cooler than normal. The warmer phase is known as El Niño.
• A result of interactions between ocean and wind systems, El Niño and La Niña have almost opposite impacts on weather events.
• The ongoing La Niña phase of the equatorial Pacific Ocean has just been predicted to persist for at least another six months, making it one of the longest-ever La Niña episodes in recorded history.
• It is also only the third episode since 1950 to stretch into the third year.

‘Triple dip’ La Niña–

• El Niño and La Niña episodes typically last for about nine months to a year.
• They usually develop in the March-June period, and are the strongest during winter (November-January in the northern hemisphere), before weakening or dissipating by March or April of next year.
• Occasionally, however, they continue for much longer periods. In recent years, the El Niño of 2015-16, spread over 19 months, was one of the longest on record and was dubbed ‘Godzilla’ due to its sustained high intensity.
• The current La Niña episode has already surpassed that in length. Having started in September 2020, it has prevailed for the last 24 months, looks set to continue for another six months, and has thus been classified as a ‘triple dip’ La Niña.

Why the current prolonged La Niña event is different from the previous events?

• Both the earlier events — one between 1973 and 1976, and the other between 1998 and 2001 — were preceded by a strong El Niño.
• Prolonged La Niña events in those instances could be explained by the fact that the amount of accumulated heat in the oceans was higher, and therefore took a longer time to dissipate.
• In the absence of a strong El Niño preceding it, the reason for the current La Niña episode is not very clear at the moment.

Duration of ENSO (El- Nino La-Nina Southern Oscillation) cycle-

• El Niño and La Niña events are not mirror images of each other. They differ in length and strength.
• El Niño episodes occur more frequently and are usually associated with more impactful weather events.
• La Niña, on the other hand, has a longer run.
• That is why multi-year La Niña events, those that continue for more than 12 months, are quite common.
• An El Niño is more likely to be a single-year event.
• According to a recent paper published by Chinese researchers, almost half (six out of 13) of all La Niña events since 1950 have stretched for two years, while three, including the current one, have continued for three years.
• In contrast, over 75% of El Niño events (15 out of 20) ended within a year.
• No El Niño has ever stretched into the third year.

Evaluating the likely impact on India–

• In the Indian context, La Niña is associated with good rainfall during the monsoon season.
• This is the opposite of El Niño which is known to suppress monsoon rainfall.
• Thus, a continued spell of La Niña could lead to an expectation of another year of good, or normal, rainfall during the monsoon.
• Until now, the monsoon season this year has produced 7% more rain compared to normal. Last year, the seasonal rainfall was almost 100%.
• But, even though powerful, the ENSO condition is only one of the several factors affecting monsoon rainfall in India.
• There is no one-on-one correlation between the ENSO condition and the amount of rainfall.

Facts for prelims–

• The ongoing (year 2022) La Niña phase is one of the longest-ever La Niña episodes in recorded history.
• It is also only the third episode since 1950 to stretch into the third year.
• This is called “Triple-Dip” La-Nina event because it has surpassed 24 months and predicted to be continue for another 6 months. Thus Expected to be continue for 3rd year in a row (Thats why the term- Triple-Dip).
• The triple dip hanned two times in the past i.e.1973-1976 and 1998-2001.
• This La-Nina episode differs from the previous two, because the earlier two were preceded by a strong El-Nino events which is not the case with this La-Nina event.
• In the Indian context, La Niña is associated with good rainfall during the monsoon season.
• This event is causing drought conditions to the USA and Horn of Africa, while causing excess rainfall to South Asia (India, Pakistan, Indonasiaetc)  and Australia.

La Niña’s cooling influence is temporarily slowing the rise in global temperatures but it will not halt or reverse the long-term warming trend.