ENSO response depending on the state of the North Atlantic under a net-zero carbon emission scenario

Abstract

Understanding the response of the El Niño-Southern Oscillation (ENSO) in a net-zero carbon emission scenario is critical for correctly projecting future climate variability after the Paris Agreement. This study examines the behavior of ENSO using the Community Earth System Model version 2, in which a 400 year simulation was performed, following the SSP5-8.5 pathway, then gradually reducing CO2 emissions to net-zero with stabilization period. After reaching net-zero CO2 emissions, the state of the North Atlantic sea surface temperature (SST) is characterized by two different pathways, either fast warming or slow warming. We found that both El Niño and La Niña events have intensified during the North Atlantic fast warming period compared to that during the North Atlantic slow warming period. This is due to the strengthening of the La Niña-like mean state in the tropical Pacific under the rapid warming of the North Atlantic, which enhances the Ekman pumping feedback and zonal advective feedback. Therefore, this study suggests that in a net-zero CO2 emission environment, ENSO amplitude can either increase or decrease, but it is regulated by the North Atlantic SST state, implying that the inter-basin interactions should be considered to understand ENSO variability even after reaching net-zero emissions. © 2025 The Author(s). Published by IOP Publishing Ltd.