Future changes in the global teleconnections of extreme El Nio events

Model simulations show a robust increase in El Nio-Southern Oscillation (ENSO)-related precipitation variability in a warmer climate, but there remains uncertainty in whether the characteristics of ENSO events themselves may change in the future. Our study aims to disentangle these effects by addressing how the global impacts of observed large El Nio events would change in under present and future background climate conditions.Pacemaker simulations with the EC-Earth3-CC model were performed replaying the 3 strongest observed El Nio events from the historical record (1982/83, 1997/98, 2015/16). Model tropical Pacific sea surface temperature (SST) anomalies were restored towards observations, while imposing different background states, mimicking present and future climate conditions (following the SSP2-4.5). All variables outside the restoring region evolve freely in a coupled-atmosphere ocean transient simulation. For each start date, 30 ensemble members with different initial conditions were run for 2 years. Using this approach we ask what impacts would arise if the observed El Nio occurred in the past or future?In response to the same imposed El Nio SST anomalies, precipitation anomalies are shifted towards the Eastern equatorial Pacific in the future compared to the present day, leading to changes in the extratropical response to El Nio. Some examples are an amplification of the surface temperature response over north-eastern North America, northern South America and Australia in boreal winter. We link the changes of El Nio related tropical Pacific precipitation to a decrease in the climatological zonal SST gradient in the equatorial Pacific, as we move from past to future climatologies, which potentially leads to a higher convection sensitivity to SST anomalies over the Central and Eastern equatorial Pacific in the future. Changes in the future climate response to extreme El Nio events are not homogeneous among regions. For example, cold and hot anomalies driven by extreme El Nio over North America and Australia in the future are amplified, whereas the response over southern Africa gets muted due to shifts in atmospheric circulation. Our study aims to attribute the absolute future climate response to extreme El Nio events to either changes in El Nio teleconnections or climate change.