Department of Atmospheric Science, School of Environmental Studies, China University of Geosciences, Wuhan, China.
Max Planck Institute for Meteorology, Hamburg, Germany.
Nat Commun. 2024 Oct 24;15(1):9161. doi: 10.1038/s41467-024-53509-6.
The Walker circulation is projected to slow down in response to greenhouse gas warming. However, detecting the impact of human activities on changes in the Walker circulation is challenging due to the significant influence of internal variability. Here, based on ensembles of multiple climate models from the Coupled Model Intercomparison Project Phase 6 (CMIP6), we show evidence that the emergence of the human-induced weakening of Walker circulation tends to occur earlier in the middle-upper troposphere than at the surface. This earlier emergence is attributed to a more pronounced initial weakening response of the middle-upper tropospheric Walker circulation to atmospheric CO radiative forcing. We further reveal that the emergence time of a weaker Walker circulation varies across models. This intermodel spread is governed by an ocean thermostat that operates by modulating the zonal sea surface temperature gradient over the tropical Indo-Pacific region. Our findings address the key question of whether and how to detect human-induced large-scale atmospheric circulation changes and provide valuable insights for assessing the associated risks.
沃克环流预计将减缓对温室气体变暖的响应。然而，由于内部变率的显著影响，检测人类活动对沃克环流变化的影响具有挑战性。在这里，我们基于来自第六阶段耦合模式比较计划（CMIP6）的多个气候模型的集合，表明有证据表明，与地表相比，人类引起的沃克环流减弱的出现往往更早发生在中高层大气中。这种更早的出现归因于中高层大气沃克环流对大气 CO2 辐射强迫的初始减弱响应更为明显。我们进一步揭示了较弱沃克环流的出现时间在不同模型之间存在差异。这种模型间的差异受海洋恒温器控制，该恒温器通过调节热带印度洋-太平洋地区的纬向海表温度梯度来发挥作用。我们的研究结果解决了是否以及如何检测人为引起的大规模大气环流变化的关键问题，并为评估相关风险提供了有价值的见解。
