The La Niñas of 1974/75 and 2011/12 were each the second year of a 'double dip' La Niña event.
Notes on verification
Confirmed by NOAA ONI index records and climate.gov ENSO blog archives showing both events as second-year 'double-dip' La Niña episodes. [tier=silver indep_score=0.925 clusters=2 claim_tier=notable]
Sources
- Say Goodbye to a Historic El Niño and Hello to La Niña (seed:science_and_space)
- https://www.climate.gov/news-features/blogs/enso/happy-new-year-La-nina (corroboration)
- https://ggweather.com/enso/oni.htm (corroboration)