Webinar Details

Title: Overview and history of ENSO theory

Speaker: Jérôme Vialard  (IRD, France)

Date: January 22, 2026
Time: 07:00 UTC

- Save the link -

You can Sign up here or by QR code for reminders

Abstract
The El Niño–Southern Oscillation (ENSO) arises from the tight coupling between the tropical Pacific Ocean and atmosphere, with far-reaching impacts on climate, weather, ecosystems, and societies worldwide. Since “El Niño” first appeared in the scientific literature in 1891, our understanding has progressed through a series of major conceptual breakthroughs. In this talk, I will briefly revisit these key milestones before focusing on the Recharge Oscillator (RO) framework — one of the most successful and insightful conceptual models of ENSO. The RO provides a minimal yet physically grounded description that combines the Bjerknes feedback, delayed ocean adjustment, stochastic wind forcing, and weak nonlinearities. Despite its simplicity, it captures ENSO’s core properties — amplitude, spectrum, seasonality, and asymmetry — and even informs prediction. I will conclude by highlighting current frontiers in ENSO research: improving our understanding of extreme El Niño events and of ENSO’s interactions with other modes of variability, and ultimately establishing a quantitative theory for how ENSO responds to changes in the tropical Pacific mean state under anthropogenic warming.

Biography
Jérôme Vialard is a senior climate scientist with the Institut de Recherche pour le Développement (IRD), based at LOCEAN–IPSL in Paris. His research focuses on the role of tropical oceans in climate variability and change, including their biogeochemical impacts. He recently led a comprehensive review of ENSO theory. Jérôme has contributed extensively to international coordination efforts through CLIVAR, including serving on the Pacific Research Panel, co-chairing the Indian Ocean Research Panel, and co-leading the review of the Indian Ocean Observing System. He was principal investigator of the CIRENE research cruises on air–sea interactions in the Indian Ocean. He has co-authored more than 160 peer-reviewed publications and received the Christian Le Provost, Océanographe award in 2010.