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Abstract:
Model simulations show a robust increase in ENSO-related precipitation variability in a warmer climate, however whether the characteristics of ENSO events themselves may change in the future remains uncertain.Pacemaker simulations with the EC-Earth3-CC model were performed replaying the El Niño events of 1982/83, 1997/98 and 2015/16. Tropical Pacific sea surface temperature (SST) anomalies were restored towards observations, while imposing different background states (past, present and future conditions). All variables outside the restoring region evolve freely in a coupled-atmosphere ocean transient simulation run for 2 years with 30 ensemble members. Using this approach, we ask ‘what impacts would arise if the observed El Niño occurred in the past or future’?In response to the same imposed El Niño SST anomalies, precipitation anomalies are shifted towards the Eastern equatorial Pacific in the future compared to the present day. This leads to changes in the extratropical response to El Niño such as an amplification of the surface temperature response over north-eastern North America, northern South America and Australia in boreal winter. Changes of tropical Pacific El Niño-related precipitation are linked to a decrease in the climatological zonal SST gradient in the equatorial Pacific, as we move from past to future, potentially leading to a higher convection sensitivity to SST anomalies in the future. We also show that El Niño impacts have already intensified between present day and preindustrial. Ongoing work is exploring changes in atmospheric circulation that lead to the overall intensification of El Niño impacts that we show in our study.
