The Hadley circulation (HC) is a global-scale atmospheric feature with air descending in the subtropics and ascending in the tropics, which plays a fundamental role in Earth's climate because it transports energy polewards and moisture equatorwards. Theoretically, as a consequence of anthropogenic climate change, the HC is expected to expand polewards, while indications on the HC strength are equivocal, as weakening and strengthening are expected in response to different mechanisms. In fact, there is a general agreement among reanalyses and climate simulations that the HC has significantly widened in the last four decades and it will continue widening in the future, but there is no consensus on past and future changes of the HC strength. Substantial uncertainties are produced by the effects of natural variability, structural deficiencies in climate models and reanalyses, and the influence of other forcing factors, such as anthropogenic aerosols, black carbon, and stratospheric and tropospheric ozone. The global HC can be decomposed into three regional HCs, associated with ascending motion above Equatorial Africa, the Maritime Continent, and Equatorial America, which have evolved differently during the last decades. Climate projections suggest a generalized expansion in the Southern Hemisphere, but a complex regional expansion/contraction pattern in the Northern Hemisphere.

中文翻译：

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气候变化中的哈德利环流


哈德利环流（HC）是一种全球范围的大气特征，空气在亚热带下降，在热带上升，它在地球气候中发挥着重要作用，因为它向极地输送能量，向赤道输送水分。理论上，由于人为气候变化，碳氢化合物预计将向极地扩展，而碳氢化合物强度的迹象是模棱两可的，因为预计会因不同的机制而减弱和加强。事实上，重新分析和气候模拟之间普遍认为，在过去四十年中，碳氢化合物已显着扩大，并且未来还将继续扩大，但对于碳氢化合物强度过去和未来的变化，尚未达成共识。自然变率的影响、气候模型和重新分析的结构性缺陷以及人为气溶胶、黑碳、平流层和对流层臭氧等其他强迫因素的影响产生了很大的不确定性。全球热球可以分解为三个区域热球，与赤道非洲、海洋大陆和赤道美洲上空的上升运动相关，这些区域在过去几十年中发生了不同的演变。气候预测表明南半球出现普遍扩张，但北半球出现复杂的区域扩张/收缩模式。