Which of the following statements is NOT correct?
- (a)El Nino is an ocean current, which appears off the Peru coast.
- (b)El Nino weakens the Indian Monsoon.
- (c)El Nino occurs every year.
- (d)La Nina strengthens the Indian Monsoon.
Correct — C. 'El Nino occurs every year' is the NOT-correct statement — El Nino is an irregular, quasi-periodic event, recurring on average every 2 to 7 years as part of the El Nino-Southern Oscillation (ENSO) cycle, not annually. The other three statements are accurate: El Nino is marked by anomalous warming of surface waters off the Peru coast (statement a), it typically weakens/suppresses the Indian south-west monsoon (statement b), and La Nina — the cold-phase counterpart — typically strengthens the Indian monsoon (statement d).
- (a)El Nino is an ocean current, which appears off the Peru coast. — This statement IS correct (El Nino is the anomalous warm-water event off the Peru coast), so it is not the answer to a 'NOT correct' question.
- (b)El Nino weakens the Indian Monsoon. — This statement IS correct — El Nino years are typically associated with below-normal south-west monsoon rainfall in India — so it is not the answer.
- (d)La Nina strengthens the Indian Monsoon. — This statement IS correct — La Nina years are typically associated with above-normal south-west monsoon rainfall in India — so it is not the answer.
El Nino and La Nina are the warm and cold phases of ENSO (El Nino-Southern Oscillation), an irregular ocean-atmosphere cycle in the tropical Pacific. El Nino recurs roughly every 2-7 years, not annually, and typically weakens the Indian south-west monsoon by disrupting the Walker Circulation; La Nina has broadly the opposite effect.
This is a classic 'find the false statement' trap — three true statements are mixed with one plausible-sounding but factually wrong claim ('every year'). ENSO's defining feature is its irregularity, so any statement claiming a fixed annual cycle is a red flag.
- El Nino and La Nina are phases of ENSO — an irregular cycle recurring roughly every 2-7 years, not annually.
- El Nino = anomalous warming of the eastern/central tropical Pacific (including off the Peru coast) — typically weakens the Indian monsoon.
- La Nina = anomalous cooling of the same tropical Pacific belt — typically strengthens the Indian monsoon.
- ENSO's irregularity is its defining trait — it does not follow a fixed yearly schedule.
Three true statements (a, b, d) vs. the one false claim (c) — ENSO's defining trait is its irregularity, not an annual cycle.
- Assuming El Nino/La Nina follow a fixed annual cycle — they are irregular, occurring roughly every 2-7 years.
- Mixing up which phase strengthens vs weakens the Indian monsoon (El Nino weakens it; La Nina strengthens it).
UPSC/MPPSC frequently test ENSO via 'which statement is NOT correct' or 'match the effect to the phase' formats — anchor on El Nino = weak monsoon, La Nina = strong monsoon, and remember ENSO is irregular, not annual.
La Nina is suspected to have caused recent floods in Australia. How is La Nina different from El Nino? 1. La Nina is characterised by unusually cold ocean temperature in equatorial Indian Ocean whereas El Nino is characterised by unusually warm ocean temperature in the equatorial Pacific Ocean. 2. El Nino has adverse effect on south-west monsoon of India, but La Nina has no effect on monsoon climate. Which of the statements given above is/are correct?
- (a) 1 only
- (b) 2 only
- (c) Both 1 and 2
- (d) Neither 1 nor 2
Answer(d) Neither 1 nor 2
Same core ENSO-monsoon relationship — this UPSC 2011 question also tests whether El Nino/La Nina affect the Indian monsoon, confirming El Nino weakens it (not simply 'adverse' left unqualified) and that La Nina does have an effect (it strengthens it) — the same facts anchoring statements (b) and (d) here.
- practice — not a real PYQ
El Nino-Southern Oscillation (ENSO) events recur, on average, once every:
- (a)1 year
- (b)2-7 years
- (c)10-15 years
- (d)20-25 years
Answer(b) 2-7 years — ENSO is an irregular, not an annual, cycle.
- practice — not a real PYQ
Which of the following statements about La Nina is correct?
- (a)It is characterised by anomalous warming of the eastern Pacific
- (b)It typically weakens the Indian south-west monsoon
- (c)It typically strengthens the Indian south-west monsoon
- (d)It occurs every year without fail
Answer(c) It typically strengthens the Indian south-west monsoon — La Nina, the cold ENSO phase, is generally associated with above-normal Indian monsoon rainfall.