Vecchi Gabriel A, Soden Brian J, Wittenberg Andrew T, Held Isaac M, Leetmaa Ants, Harrison Matthew J
NOAA/Geophysical Fluid Dynamics Laboratory, Princeton, New Jersey 08540-6649, USA.
Nature. 2006 May 4;441(7089):73-6. doi: 10.1038/nature04744.
Since the mid-nineteenth century the Earth's surface has warmed, and models indicate that human activities have caused part of the warming by altering the radiative balance of the atmosphere. Simple theories suggest that global warming will reduce the strength of the mean tropical atmospheric circulation. An important aspect of this tropical circulation is a large-scale zonal (east-west) overturning of air across the equatorial Pacific Ocean--driven by convection to the west and subsidence to the east--known as the Walker circulation. Here we explore changes in tropical Pacific circulation since the mid-nineteenth century using observations and a suite of global climate model experiments. Observed Indo-Pacific sea level pressure reveals a weakening of the Walker circulation. The size of this trend is consistent with theoretical predictions, is accurately reproduced by climate model simulations and, within the climate models, is largely due to anthropogenic forcing. The climate model indicates that the weakened surface winds have altered the thermal structure and circulation of the tropical Pacific Ocean. These results support model projections of further weakening of tropical atmospheric circulation during the twenty-first century.
自19世纪中叶以来，地球表面已经变暖，模型表明人类活动通过改变大气辐射平衡导致了部分变暖。简单理论认为全球变暖将降低平均热带大气环流的强度。这种热带环流的一个重要方面是赤道太平洋上空空气的大规模纬向（东西向）翻转——由向西的对流和向东的下沉驱动——称为沃克环流。在这里，我们利用观测数据和一系列全球气候模型实验，探讨自19世纪中叶以来热带太平洋环流的变化。观测到的印度洋-太平洋海平面气压显示沃克环流减弱。这一趋势的规模与理论预测一致，在气候模型模拟中得到了准确再现，并且在气候模型中，主要是由于人为强迫。气候模型表明，减弱的地表风改变了热带太平洋的热结构和环流。这些结果支持了21世纪热带大气环流进一步减弱的模型预测。
