Two La Niñas were the second year of a 'double dip' La Niña event, occurring in 1974/75 and 2011/12.
Notes on verification
Confirmed by NOAA Climate.gov, Columbia Earth Institute, and ARC Centre of Excellence for Climate Extremes as accurate historical ENSO record of double-dip La Niña events in 1973-75 and 2010-12.
Sources
- Say Goodbye to a Historic El Niño and Hello to La Niña (smithsonianmag.com)
- https://climateextremes.org.au/wp-content/uploads/Multi-year-La-Nina-Events-ARC-Centre-of-Excellence-for-Climate-Extremes.pdf (climateextremes.org.au)
- https://www.climate.gov/news-features/understanding-climate/double-dip-la-ni%C3%B1a (climate.gov)
- https://news.climate.columbia.edu/2011/09/29/welcome-back-la-nina (news.climate.columbia.edu)