Revisiting Unstable ENSO Teleconnections From a Global Perspective

The impacts of El Niño‐Southern Oscillation (ENSO) on regional climate may vary from decade to decade. Here, we quantify these unstable ENSO impacts on a global scale by calculating the range of possible correlation coefficients (CCs) between the Niño‐3.4 index and climate anomalies in boreal winter at each ∼1° grid point of the globe over any 31‐year running time windows during 1880–2014. In observations, the CCs between the Niño‐3.4 index and surface air temperature (SAT)/precipitation are significantly unstable at a 95% confidence level over 74.7%/73.6% of the globe, respectively, mainly over tropical Indian and Atlantic Oceans, Africa, Australia, North America, and Eurasia. Further Analyses on Community Earth System Model version 2 pacemaker simulations suggest that after the non‐ENSO‐related internal variability is largely removed, the simulated CCs are always significant over most of the tropics and North America. This suggests that internal variability is essential for driving unstable ENSO teleconnections over these regions mainly by modulating the Southern Oscillation and Pacific‐North American teleconnections. Our findings on the nonstationary impacts of ENSO have important implications for understanding and enhancing global seasonal forecast skill.