The Pacific Walker circulation—the tropical Pacific zonal overturning circulation of the atmosphere—and the associated sea surface temperature distribution in the tropical Pacific significantly impact global climate. However, climate model historical simulations cannot capture the observed Walker circulation enhancement since around 1980. Although a number of mechanisms have been proposed to explain the observed change, quantitative discussion and clues for reconciling the model-observation discrepancy have not yet been settled. Here we show that the Walker circulation strengthening between 1980 and 2020 can be quantitatively explained by the remote influence of subtropical and extratropical sea surface temperature changes. This conclusion is obtained from climate model pacemaker experiments in which sea surface temperature anomalies outside the tropics are restored towards observations. Influence from the southeastern Pacific, which cools the eastern tropical Pacific, is especially crucial for the Walker circulation strengthening. This equatorward influence occurs mostly through the atmosphere and its thermal coupling with the ocean. We further show that current generation climate models have biases in southeastern Pacific surface temperature changes, which may cause the failure in reproducing the Walker circulation trend. Our results suggest that improved representation of air–sea coupling in this region could enable better projections of future climate.

太平洋沃克环流（热带太平洋大气纬向翻转环流）以及热带太平洋相关海面温度分布对全球气候产生重大影响。然而，气候模型的历史模拟无法捕捉自1980年左右以来观测到的沃克环流增强。尽管已经提出了许多机制来解释观测到的变化，但尚未解决定量讨论和协调模型与观测差异的线索。在这里，我们表明，1980年至2020年间沃克环流的加强可以通过副热带和温带海面温度变化的远程影响来定量解释。这一结论是从气候模型起搏器实验中得出的，其中热带地区以外的海面温度异常被恢复到观测中。来自东南太平洋的影响使东热带太平洋变冷，对于沃克环流的加强尤其重要。这种赤道影响主要通过大气及其与海洋的热耦合发生。我们进一步表明，当前一代气候模型对东南太平洋表面温度变化存在偏差，这可能导致无法再现沃克环流趋势。我们的结果表明，改善该地区海气耦合的代表性可以更好地预测未来气候。