美国华盛顿大学Sokol, Adam B.研究团队取得一项新突破。他们的最新研究揭示砧状云变薄意味着气候敏感性更强。2024年4月17日，国际知名学术期刊《自然—地球科学》发表了这一成果。

据介绍，随着气候变暖，热带对流产生的高云面积预计会缩小，而与这一变化相关的辐射反馈长期以来一直是备受争议的话题。世界气候研究计划在最近对气候敏感性的评估中发现，尽管存在很大的不确定性，但这种反馈基本上是负面的。

研究人员使用一种将高空云作为光学连续体的一部分，而不是具有固定不透明度的实体的方法来检查云的响应。结果表明，高分辨率大气模型的集合不支持实质性的负反馈。相反，模型表明云面积和不透明度的变化共同起着微弱的正反馈作用。正的不透明度分量来自于，较厚的气候变冷的云相对于较薄的气候变暖的云的面积不成比例的减少。

这表明，厚云区与对流翻转的速率紧密相关，而对流翻转的速率将会随着变暖而放缓，而薄云区则受到其他不太确定的过程的影响。正反馈与以前的估计明显不同，并导致平衡气候敏感性的中位数估计值相对于以前的社区评估值正偏移0.3°C。

附：英文原文

Title: Greater climate sensitivity implied by anvil cloud thinning

Author: Sokol, Adam B., Wall, Casey J., Hartmann, Dennis L.

Issue&Volume: 2024-04-17

Abstract: High clouds produced by tropical convection are expected to shrink in area as the climate warms, and the radiative feedback associated with this change has long been the subject of controversy. In a recent assessment of climate sensitivity, the World Climate Research Programme estimated that this feedback is substantially negative, albeit with substantial uncertainty. Here we examine the cloud response using an approach that treats high clouds as part of an optical continuum rather than entities with fixed opacity. We show that a substantial negative feedback is not supported by an ensemble of high-resolution atmospheric models. Rather, the models suggest that changes in cloud area and opacity together act as a weakly positive feedback. The positive opacity component arises from the disproportionate reduction in the area of thick, climate-cooling clouds relative to thin, climate-warming clouds. This suggests that thick cloud area is tightly coupled to the rate of convective overturning—which is expected to slow with warming—whereas thin cloud area is influenced by other, less certain processes. The positive feedback differs markedly from previous estimates and leads to a +0.3 °C shift in the median estimate of equilibrium climate sensitivity relative to a previous community assessment.

DOI: 10.1038/s41561-024-01420-6

Source: https://www.nature.com/articles/s41561-024-01420-6