Follow el Niño with SLA: Inverse sea level anomaly averaged over a region (3-13N, 125E-145E) north of New Guinea, and sea surface temperature anomaly in the equatorial mid-Pacific NINO3.4 (https://www.psl.noaa.gov/gcos_wgsp/Timeseries). Positive NINO3.4 and negative SLA north of New Guinea indicate el Niño events while negative NINO3.4 and positive SLA north of New Guinea indicate la Niña events. SLA north of New Guinea was extremely low early in 2015 and remained low throughout the year marking a significant el Niño event globally.