Strong El Niño and La Niña precipitation—sea surface temperature sensitivity under a carbon removal scenario

Abstract

El Niño-Southern Oscillation-induced tropical Pacific precipitation anomalies have global impacts and will intensify under greenhouse warming, but the potential for mitigating these changes is less understood. Here, we identify distinct hysteresis features in the precipitation-sea surface temperature sensitivity between strong El Niño and La Niña phases using a large ensemble carbon removal numerical simulation. The strong El Niño precipitation sensitivity exhibits a century-scale hysteretic enhancement and eastward shift, mainly due to modulated deep convection anomalies by the Intertropical Convergence Zone via cloud-longwave feedback. Instead, the strong La Niña counterpart is concentrated toward the equator, mostly in the central-western Pacific, with a shorter hysteresis period of a few decades. This primarily involves changes in shallow convection and surface thermal structures during La Niña, shaped by global warming-induced upper-ocean circulation changes. The distinct climate change regimes of strong El Niño and La Niña precipitation sensitivity hold important implications for assessing mitigation consequences. The hysteresis in precipitation-sea surface temperature sensitivity differs between strong El Niño and La Niña phases, with El Niño intensifying and shifting eastward due to deep convection, while La Niña is more equator-centered with a shorter hysteresis period, according to a large ensemble simulation of symmetric CO2 ramp-up and ramp-down pathways.