Underlying mechanisms leading to El Nino-to-La Nina transition are unchanged under global warming

Abstract

El Nino's transitions play critical roles in modulating severe weather and climate events. Therefore, understanding the dynamic factors leading to El Nino's transitions and its future projection is a great challenge in predicting the diverse socioeconomic influences of El Nino over the globe. This study focuses on two dynamic factors controlling the El Nino-to-La Nina transition from the present climate and to future climate, using the observation, the historical and the RCP8.5 simulations of Coupled Model Intercomparison phase 5 climate models. The first is the inter-basin coupling between the Indian Ocean and the western North Pacific through the subtropical high variability. The second is the enhanced sensitivity between sea surface temperature and a deep tropical convection in the central tropical Pacific during the El Nino's developing phase. We show that the dynamic factors leading to El Nino-to-La Nina transition in the present climate are unchanged in spite of the increase of greenhouse gas concentrations. We argue that the two dynamic factors are strongly constrained by the climatological precipitation distribution over the central tropical Pacific and western North Pacific as little changed from the present climate to future climate. This implies that two dynamical processes leading to El Nino-to-La Nina transitions in the present climate will also play a robust role in global warming.