Weakening Atlantic Niño-Pacific connection under greenhouse warming.

Sea surface temperature variability in the equatorial eastern Atlantic, which is referred to as an Atlantic Nino (Nina) at its warm (cold) phase and peaks in boreal summer, dominates the interannual variability in the equatorial Atlantic. By strengthening of the Walker circulation, an Atlantic Nino favors a Pacific La Nina, which matures in boreal winter, providing a precursory memory for El Nino-Southern Oscillation (ENSO) predictability. How this Atlantic impact responds to greenhouse warming is unclear. Here, we show that greenhouse warming leads to a weakened influence from the Atlantic Nino/Nina on the Pacific ENSO. In response to anomalous equatorial Atlantic heating, ascending over the equatorial Atlantic is weaker due to an increased tropospheric stability in the mean climate, resulting in a weaker impact on the Pacific Ocean. Thus, as greenhouse warming continues, Pacific ENSO is projected to be less affected by the Atlantic Nino/Nina and more challenging to predict.