ENSO Teleconnections to North America in CMIP5 Models: Fidelity to Observed Relationships and Projected Changes

The El Niño-Southern Oscillation (ENSO) is the dominant mode of tropical atmosphere-ocean interaction on interannual timescales, with significant impacts on North American seasonal temperature and precipitation. Here we first examine the ability of CMIP5 models to reproduce the North American seasonal temperature and precipitation patterns associated with ENSO in the 20th century. Overall, we find a wide range in model performance, with approximately half the models performing reasonably well in capturing the temperature patterns, and even fewer with the precipitation patterns. Next we examine the projected changes in ENSO teleconnections to North American temperature and precipitation in the 21st century under the RCP4.5 and 8.5 emissions pathways. In the entire ensemble, we generally do not find statistically significant changes in the temperature and precipitation patterns, which owes in part to the large ensemble spread in ENSO teleconnections. However, when we isolate a subset of models that perform best in capturing the observed ENSO teleconnections, we do detect changes in the temperature and precipitation patterns under the RCP8.5 pathway. Preliminary results suggest a weakening of the temperature patterns over northwest North America but a strengthening to the southeast. The precipitation changes suggest a strengthening for El Niño but a weakening for the La Niña patterns, particularly in western North America. These results suggest that there may be changes to ENSO teleconnections under global warming, but the wide range in ability of CMIP5 models to capture these teleconnections makes it challenging to diagnose these changes.