Understanding projected future changes in multi-year La Niña events

Multi-year La Niña events have been linked to numerous important impacts, including long-lasting climate conditions that can favor droughts, fire weather, tornado outbreaks, and hurricanes in various parts of the world. Thus accurately simulating and predicting these events are crucial to inform society. To better understand these events, we examine the background climatology and ENSO characteristics in observations and model simulations.. We analyze sea surface temperature (SST) from the NOAA ERSSTv5 observational reconstruction, as well as historical (1851–2014) and future (SSP 5.85 for 2015–2100) ensemble simulations from the GFDL SPEAR_LO global coupled GCM at 1° resolution. After first evaluating the SPEAR simulations against historical observations, we next investigate projected changes in ENSO as simulated by SPEAR between 1920–2010 and 2011-2100. SPEAR projects a more El Niño-like mean state in the future, characterized by slightly enhanced warming in the eastern equatorial Pacific. It also shows an intensified ENSO with a reduced frequency of multi-year La Niña events in the future. We compare these results to previous studies, propose avenues to further understand and reconcile these results, and discuss possible causes and implications of these projected changes.