El Nino Types from 1901 to 2017 (IMAGE) University of Hawaii at Manoa Caption El Niño types (color-coded by onset location and strength) from 1901 to 2017. Ocean Niño Index (ONI) is a measure of sea-surface temperature anomalies, and thus El Niño strength, with the dashed line showing the lower limit considered as El Niño conditions. Note the shift from eastern Pacific (blue) to western/central Pacific (red) types in the late 1970's, and the prevalence of extreme events (black) since 1970. Credit Wang et al. 2019 Usage Restrictions Image may be used with appropriate caption and credit. License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.