La Nina Event

In News

• Recently, Australia’s Bureau of Meteorology (BOM) predicted that a third consecutive event of La Nina could be underway which could lead to additional rainfall along its east coast this summer.  

El Niño-Southern Oscillation (ENSO)

• ENSO is a global phenomenon, which affects the temperature and precipitation of many regions around the globe, including the Indian subcontinent. The most important factor with the ENSO is the ability of the scientists to predict its occurrence, thereby predicting the amount of rainfall and temperature in the region.  
• ENSO includes three phenomena:
  • El-Nino: The term “El Niño” refers to the Christ Child and was given by fishermen along the coasts of Ecuador and Peru to describe the warming of the central and eastern pacific. 
    • It leads to warming in surface temperature of the eastern Pacific Ocean region. This is associated with an increase in rainfall along the western coast of South America and a decrease in rainfall over the Indian subcontinent. It also leads to westerly winds, instead of the generally occurring easterly winds.
    • El Nino as the warm phase of ENSO.
  • La-Nina: La Niña means Little Girl in Spanish. La Niña is also sometimes called El Viejo, anti-El Niño, or simply “a cold event.”
    • La Niña is a climate pattern that describes the cooling of surface ocean waters along the tropical west coast of South America along with a decrease in rainfall. La Nina is considered to be the counterpart to El Nino. And, the rainfall over the Indian subcontinent increases, along with augmentation of the strength of surface-level easterly winds.
    • La Nina represents the cool phase of the El Nino/Southern Oscillation (ENSO) cycle.
  • Neutral: These years are not associated with any of the above phenomena.
  • Southern Oscillation: This is the interconnection which was established between the El-Nino and the decrease in rainfall over the Indian subcontinent. Although the fishermen and later the scientists knew both the phenomena, the two were thought to be independent of each other. It was quite later that interconnection was established between the two and it was named Southern Oscillation.

What happens during the La Nina event?

• During a La Nina event, cooler-than-average sea surface temperatures prevail over the east and the central Pacific Ocean. 
• Due to the cooler temperature, the trade winds above the sea surface change in character because of a difference in the wind pressures. 
• This change in the character of the trade winds is then carried all around the world affecting different regions in different ways. 
• Many regions become colder and wetter, while many others become hotter and drier. 

Causes

• Human-induced climate change amplifies the impacts of naturally occurring events like La Niña and is increasingly influencing our weather patterns.
• Extreme El Niño and La Niña events may increase in frequency from about one every 20 years to one every 10 years by the end of the 21st century under aggressive greenhouse gas emission scenarios.

Concerns

• No spring season for India:
  • La Nina usually brings wet and cold winter and spring seasons for India, but this time large parts of India did not experience a spring season at all. 
  • This happened as a north-south pressure pattern, which usually forms over India during the winter season and dissipates by spring, continued into March and April this year. 
• Prolonged monsoon and floods in India:
  • India can experience a prolonged monsoon season for the third year in a row, for instance. 
  • The monsoon seasons of 2020 and 2021 were also extended, leading to an increase in extreme rainfall events during the period.
  • It may lead to subsequent floods as seen in many states in the last two years. 
• Drought conditions in the other parts of the world:
  • The ongoing drought conditions in 40 percent of the United States, the years-long drought conditions in the Horn of Africa and southern South America would also likely continue and become more intense due to the continuation of the La Nina.
• Hurricanes:
  • It could also form an above-average hurricane season for the Atlantic Ocean, with a 65 percent probability. 
• Heat waves & wildfires:
  • This condition could lead to devastating and unpredictable consequences for India and many other regions around the world in particular through more intense heat waves and drought and the associated risk of wildfires.

Way Ahead

• Mitigation:
  • The current atmospheric carbon dioxide (CO2) concentrations are higher than at any time in the last two million years. 
  • To align with a 1.5°C target of limiting warming, global CO2 emissions must reach net zero around 2050, with global GHG emissions reaching net-zero 15-20 years later. 
  • A delay of 15-20 years in either net-zero CO2 or net-zero GHGs implies limiting warming to 2°C rather than 1.5°C. 
• Need to shift from the sensational to the strategic: 
  • In order to stabilise the rise in temperatures, two things have to happen:
    • Anthropogenic emissions must become net-zero and, 
    • In the interim, cumulative emissions cannot exceed a global carbon budget.

• Adaptation: 
  • Adaptation can be understood as the process of adjusting to the current and future effects of climate change. 
  • India has a strategy to combat climate change under the National Action Plan on Climate Change formed with the integration of similar missions at the state level. 
  • Apart from that, India has also launched the Coalition for Disaster Resilient Infrastructure (CDRI). 
  • However, climate change would require an international collective action for maximum impact. 
  • This is because safeguarding the climate is a global requirement and any strategy in silos will only have a limited impact.

Source:DTE