Oceanic Niño Index corresponding to El Niño period is

Correct option is C

✅ (c) greater or equal to 0.5°C
· El Niño is identified when the Oceanic Niño Index (ONI) exceeds +0.5°C for at least five consecutive overlapping 3-month periods.
· Represents the sea surface temperature anomalies in the central Pacific Ocean.
· Used globally as a standard for declaring El Niño events.
❌ (a) greater or equal to 5°C
· A 5°C anomaly is an extreme and unrealistic threshold for El Niño.
· Not used in ONI classification.
❌ (b) greater or equal to -5°C
· A -5°C anomaly would indicate extreme La Niña, not El Niño.
· Incorrect threshold and sign.
❌ (d) greater or equal to -0.5°C
· Negative anomalies (below -0.5°C) are indicators of La Niña conditions, not El Niño.
· Incorrect option.