Future changes in ENSO teleconnections over the North Pacific and North America in CMIP6 simulations

El Niño–Southern Oscillation (ENSO) has major impacts on the weather and climate across many regions of the world. Understanding how these teleconnections may change in the future is therefore an important area of research. Here, we use simulations from the Coupled Model Intercomparison Project Phase 6 (CMIP6) to investigate future changes in ENSO teleconnections in the North Pacific/North America sector.

Precipitation over the equatorial Pacific associated with ENSO is projected to shift eastwards under global warming as a result of greater warming in the east Pacific, which reduces the barrier to convection as the warm pool expands eastwards. As a result, there is medium confidence (IPCC AR5 report) that ENSO teleconnections will shift eastwards in the North Pacific/North America sector. In the CMIP6 models, the present day teleconnection is relatively well simulated, with most models showing an anomalously deep Aleutian low and associated positive temperature anomalies over Alaska and northern North America in El Niño years. In the future warming simulations (we use abrupt-4xCO2, in which CO2 concentrations are immediately quadrupled from the global annual mean 1850 value), in agreement with the IPCC AR5 report, the North America teleconnection and associated circulation change is shifted eastwards in most models. However, it is also significantly weaker, with the result that the positive temperature anomalies in El Niño years over North America are much reduced. This weakening is seen both in models with a projected increase and projected decrease in the amplitude of future El Niño events. The mechanisms related to these projected changes, along with potential implications for future long range predictability over North America, will be discussed.