Understanding the recent increase in multiyear La Niñas

Five out of six La Nina events since 1998 have lasted two to three years. Why so many long-lasting multiyear La Nina events have emerged recently and whether they will become more common remains unknown. Here we show that ten multiyear La Nina events over the past century had an accelerated trend, with eight of these occurring after 1970. The two types of multiyear La Nina events over this time period followed either a super El Nino or a central Pacific El Nino. We find that multiyear La Nina events differ from single-year La Ninas by a prominent onset rate, which is rooted in the western Pacific warming-enhanced zonal advective feedback for the central Pacific multiyear La Nina events type and thermocline feedback for the super El Nino multiyear La Nina events type. The results from large ensemble climate simulations support the observed multiyear La Nina events-western Pacific warming link. More multiyear La Nina events will exacerbate adverse socioeconomic impacts if the western Pacific continues to warm relative to the central Pacific.