Fig. 1: Historical change of La Niña (1921–2022).

a, Temporal evolution of the Niño 3.4 SST anomaly. A La Niña year is defined by the below-normal (<−0.5 °C) Niño 3.4 Index, the SST anomaly averaged over the index region (5° S–5° N, 120–170° W), during its mature phase from ONDJF. A multiyear La Niña lasts at least two consecutive La Niña years. The grey bars represent neutral years. Blue shading indicates the period of 1970–2022. b,c, Comparisons of the composite accumulative climate anomalies averaged for ten single-year La Niña events (b) and ten multiyear La Niña events (c) during the period of 1920–2022. The accumulative anomalies are the sum of the ONDJF mean anomalies during each year of the entire event, including the land precipitation (mm month⁻¹), SST (°C) and 850 hPa wind (m s⁻¹) anomalies. The stippled areas denote a significance level of 0.05 by a two-tailed Student’s t-test. Data used are described in Methods.