Description

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Context

IMD has predicted an early summer with extreme heatwaves in India as climate change accelerates altering impacts of El Nino & La Nina on global weather patterns.

Key Highlights

Rising Temperatures & Early Summer:

IMD predicts an early summer in 2025 with above normal temperatures & prolonged heatwaves.

February 2025 was India warmest since 1901 with low rainfall affecting cooling mechanisms.

Climate Change & Heatwave Intensification:

Human caused climate change is making winters warmer & springs shorter in India.

2024 saw 536 heatwave days highest in 14 years with northwest region recording its hottest June since 1901.

Role of Jet Streams in Weather Patterns:

Jet streams which influence weather by shifting north-south are linked to heatwave duration & intensity.

A northward shift in pre-monsoon worsens extreme heat conditions.

El Nino & La Nina Impact on India Weather:

El Nino (warming phase) is associated with hotter summers & drier conditions.

La Nina (cooling phase) traditionally brings cooler temperatures but may lose its cooling effect in a warming world.

2023-24 El Nino was one of the strongest on record contributing to extreme weather events globally.

Weak La Nina in 2025 & ENSO Predictions:

WMO noted that La Nina emerging in Dec 2024 is weak & likely short-lived.

Predictions suggest a 60% chance of ENSO-neutral conditions in March-May 2025.

Scientists warn that even in ENSO-neutral years climate change alone can drive severe heatwaves.

Future Projections & Risks:

Studies predict stronger & more frequent El Nino events in a warmer future.

Scientists caution that La Nina may not provide relief from heat extremes as global temperatures continue to rise.

The record-breaking warming trend of 2023 is still continuing into 2025.

El Nino vs La Nina

Feature	El Niño(Warm Phase)	La Niña (Cool Phase)
Definition	A climate phenomenon characterized by the warming of sea surface temperatures (SSTs) in the central and eastern Pacific Ocean.	A climate phenomenon characterized by the cooling of sea surface temperatures (SSTs) in the central and eastern Pacific Ocean.
Cause	Weakening or reversal of trade winds over the Pacific, causing warm water to move eastward.	Strengthening of trade winds, pushing warm water westward, leading to an upwelling of cold water from deep ocean layers.
Temperature Impact	Leads to higher global temperatures and extreme heat events.	Generally associated with cooler global temperatures but may not offset global warming trends.
Effect on Indian Monsoon	Weakens monsoon → Causes droughts and reduced rainfall in India.	Strengthens monsoon → Leads to above-normal rainfall and potential floods in India.
Effect on Global Weather	Warmer temperatures, extreme heat, and drier conditions in Asia, Australia, and Africa. Colder, wetter winters in the southern U.S. and Peru. Increased risk of hurricanes in the Central/Eastern Pacific but fewer hurricanes in the Atlantic.	Cooler temperatures, heavy rainfall, and flooding in parts of Asia and Australia. Drier conditions in the southern U.S. and Peru. More hurricanes in the Atlantic, but fewer in the Central/Eastern Pacific.
Impact on Indian Agriculture	Lower rainfall → Crop failures, drought stress, and food price inflation.	Higher rainfall → Good harvests but potential crop damage due to excessive rainfall and floods.
Impact on Fisheries	Warm waters disrupt marine ecosystems, reducing fish populations off the coast of Peru, Ecuador, and Southeast Asia.	Cold waters boost nutrient-rich upwelling, leading to better fish populations and higher fish catch.
Extreme Events	1997-98 El Niño – One of the strongest recorded, causing global droughts and floods. 2015-16 El Niño – Led to severe heatwaves in India and global coral bleaching. 2023-24 El Niño – One of the strongest five on record, fueling extreme weather.	1988-89 La Niña – Led to stronger monsoons and heavy rainfall in India. 2010-11 La Niña – Severe floods in Australia and Pakistan. 2020-22 La Niña – Triple-dip event, lasted three consecutive years, causing record cold winters in some regions.
Frequency	Occurs every 2-7 years (lasts 9-12 months).	Occurs every 3-5 years (lasts 9-12 months).
Climate Change Impact	El Niño events are becoming stronger and more frequent due to global warming, intensifying heatwaves and extreme weather.	La Niña’s cooling effect may weaken in a warmer world, reducing its ability to counteract heat extremes.

ENSO (El Nino-Southern Oscillation) is climate phenomenon in Pacific Ocean that affects global weather patterns. It consists of three phases: El Niño, La Niña, Neutral. The process is driven by changes in sea surface temperatures (SSTs), trade winds, atmospheric pressure over equatorial Pacific Ocean.

Feature	El Niño (Warm Phase)	La Niña (Cool Phase)	Neutral (Normal Conditions)
Trade Winds	Weak or reverse (eastward)	Stronger than normal (westward)	Normal (east to west)
Sea Surface Temperature (SST)	Warmer than normal in the central & eastern Pacific	Cooler than normal in the central & eastern Pacific	Normal SST in the Pacific
Upwelling (Cold Water Rising)	Decreases, leading to fewer nutrients for marine life	Increases, supporting marine ecosystems	Normal upwelling near South America
Rainfall in South America (Peru, Ecuador, Chile)	Higher (Floods & landslides)	Lower (Drought)	Normal rainfall
Rainfall in Australia & Indonesia	Lower (Droughts & wildfires)	Higher (Floods & heavy storms)	Normal monsoons
Indian Monsoon Impact	Weaker monsoon → Droughts & heatwaves	Stronger monsoon → Heavy rains & floods	Normal monsoon season
Effect on Hurricanes	More hurricanes in Central & Eastern Pacific but fewer in the Atlantic	More hurricanes in the Atlantic but fewer in the Pacific	Normal hurricane activity
Effect on Global Temperatures	Warmer than average (Extreme heatwaves)	Slightly cooler than average	Normal global temperatures
Effect on Agriculture	Crop failures due to droughts (India, Australia)	Excess rainfall, flood damage to crops	Normal agricultural productivity
Effect on Fisheries	Decline in fish population near South America due to lack of nutrients	Increase in fish population due to cold nutrient-rich water	Normal fishing conditions
Occurrence Frequency	Every 2-7 years, lasts 9-12 months	Every 2-7 years, lasts 9-12 months	Occurs between El Niño & La Niña phases
Strongest Recent Event	2015-16 El Niño (India drought, coral bleaching, heatwaves)	2020-22 La Niña (Pakistan floods, strong Indian monsoon)	ENSO neutral phase in 2019