Hess Or, Chemke Rei
Department of Earth and Planetary Sciences, Weizmann Institute of Science, Rehovot, Israel.
Nat Commun. 2024 May 11;15(1):4001. doi: 10.1038/s41467-024-48316-y.
The Hadley circulation plays a central role in determining the location and intensity of the hydrological cycle in tropical and subtropical latitudes. Thus, the human-induced historical and projected weakening of the Northern Hemisphere Hadley circulation has considerable societal impacts. Yet, it is currently unknown how unparalleled this weakening is relative to the response of the circulation to natural forcings in past centuries. Here, using state-of-the-art climate models, we show that in contrast to the recent and future human-induced Hadley circulation weakening, natural forcings acted to intensify the circulation by cooling the climate over the last millennium. The reversal of a naturally-forced multi-centennial trend by human emissions highlights their unprecedented impacts on the atmospheric circulation. Given the amplifying effect of natural forcings on the Hadley circulation, our analysis stresses the importance of adequately incorporating natural forcings in climate model projections to better constrain future tropical climate changes.
哈德利环流在决定热带和亚热带纬度地区水文循环的位置和强度方面起着核心作用。因此，人为导致的北半球哈德利环流在历史上的减弱以及预计的减弱具有相当大的社会影响。然而，目前尚不清楚这种减弱相对于过去几个世纪环流对自然强迫的响应而言有多么不同寻常。在这里，我们使用最先进的气候模型表明，与近期和未来人为导致的哈德利环流减弱相反，在过去一千年中，自然强迫通过使气候变冷而起到增强环流的作用。人类排放使自然强迫的多世纪趋势发生逆转，凸显了它们对大气环流产生的前所未有的影响。鉴于自然强迫对哈德利环流的放大作用，我们的分析强调了在气候模型预测中充分纳入自然强迫以更好地限制未来热带气候变化的重要性。
