The year 2025 marks the 50th anniversary of two milestone events of early El Niño-Southern Oscillation (ENSO) research that involved Klaus Wyrtki of the University of Hawaiʻi at Mānoa, a pioneering oceanographer who made groundbreaking contributions to our understanding of ENSO: The publication of his seminal Journal of Physical Oceanography 1975 paper: “El Niño—The dynamic response of the equatorial Pacific Ocean to atmospheric forcing”, and the launch of the El Niño Watch Expedition to verify the first ever El Niño forecast based on a statistical model using the Sou