La Nina is suspected to have caused recent floods in Australia. How is La Nina different from El Nino? 1) La Nina is characterized by unusually cold ocean temperature in the equatorial Indian Ocean, whereas El Nino is characterized by unusually warm ocean temperature in the equatorial Pacific Ocean. 2) El Nino has an adverse effect on the southwest monsoon of India, but La Nina has no effect on the monsoon climate. Which of the statements given above is/are correct?

The correct answer is D. Neither statement is correct.

Statement 1 is wrong. La Nina and El Nino are opposite phases of the same ENSO cycle in the central and eastern equatorial Pacific. La Nina means unusually cold surface water there, and El Nino means unusually warm water. The Indian Ocean is not the seat of either phenomenon. Its own air-sea oscillation is the Indian Ocean Dipole.

Statement 2 is wrong. El Nino is generally linked to a weaker southwest monsoon and deficient rain over India. La Nina is generally associated with a stronger monsoon and above-normal rainfall, so it does have a monsoon effect. It also brings heavier rain to eastern Australia and Indonesia, which fits the flooding in the question.

The core concept is ENSO, and it matters for Mains on monsoon variability, food security and disaster preparedness.

Trap: Aspirants often assume that La Nina has no monsoon impact simply because it is the "cool" phase. Confusing the Pacific with the Indian Ocean in statement 1 is the other common error.