Tropical Atlantic multidecadal variability is dominated by external forcing
Tropical Atlantic multidecadal variability is dominated by external forcing
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DOI：
10.1038/s41586-023-06489-4
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发表时间：
2023-09
期刊：
影响因子：
64.8
通讯作者：
C. He;A. Clement;Sydney M Kramer;M. Cane;J. Klavans;Tyler M. Fenske;L. Murphy
中科院分区：
文献类型：
--
作者：
C. He;A. Clement;Sydney M Kramer;M. Cane;J. Klavans;Tyler M. Fenske;L. Murphy
热带大西洋气候的特征是大西洋海表温度（SSTs）、萨赫勒地区降雨和飓风活动等显著且相关的多年代际变率。由于模型和观测的不确定性，这些系统之间物理关系的起源仍然存在争议，，，-。研究表明，自1950年以来，热带大西洋海温的跨赤道梯度主要由与人为排放和火山气溶胶相关的辐射扰动驱动，是大西洋飓风形成和萨赫勒降雨的关键决定因素。这种关系在CMIP6地球系统模式的大集合中是模糊的，因为这些模式高估了1950年左右以来北半球相对于南半球的长期变暖趋势，以及大气环流和降雨的相关变化。当高估的趋势被去除后，海温与大西洋飓风形成和萨赫勒地区降雨之间的相关性作为对辐射强迫的响应出现，特别是自1950年以来，人为气溶胶强迫一直很高。我们的研究结果表明，与整个北大西洋的海温相比，热带大西洋海温梯度对热带影响的决定作用更强，因为梯度通过当地大气环流与热带影响的物理联系更紧密。我们的研究结果强调，大西洋飓风活动和萨赫勒地区的降雨变化可以通过人为排放和火山活动驱动的辐射强迫来预测，但更可靠的预测受到信号噪声悖论的限制，以及未来气候强迫的不确定性。
The tropical Atlantic climate is characterized by prominent and correlated multidecadal variability in Atlantic sea surface temperatures (SSTs), Sahel rainfall and hurricane activity, , –. Owing to uncertainties in both the models and the observations, the origin of the physical relationships among these systems has remained controversial, , , –. Here we show that the cross-equatorial gradient in tropical Atlantic SSTs—largely driven by radiative perturbations associated with anthropogenic emissions and volcanic aerosols since 1950,—is a key determinant of Atlantic hurricane formation and Sahel rainfall. The relationship is obscured in a large ensemble of CMIP6 Earth system models, because the models overestimate long-term trends for warming in the Northern Hemisphere relative to the Southern Hemisphere from around 1950 as well as associated changes in atmospheric circulation and rainfall. When the overestimated trends are removed, correlations between SSTs and Atlantic hurricane formation and Sahel rainfall emerge as a response to radiative forcing, especially since 1950 when anthropogenic aerosol forcing has been high. Our findings establish that the tropical Atlantic SST gradient is a stronger determinant of tropical impacts than SSTs across the entire North Atlantic, because the gradient is more physically connected to tropical impacts via local atmospheric circulations. Our findings highlight that Atlantic hurricane activity and Sahel rainfall variations can be predicted from radiative forcing driven by anthropogenic emissions and volcanism, but firmer predictions are limited by the signal-to-noise paradox, –and uncertainty in future climate forcings.