法国索邦大学McKim Brett研究团队近日取得一项新成果。他们的最新研究揭示了由物理和观测限制提出的弱砧云区域反馈。2024年4月1日出版的《自然—地球科学》杂志发表了这项成果。

据悉，在估计地球气候敏感性时，砧状云随变暖的变化仍然是不确定性的主要来源。

研究人员开发了一种分解砧状云的变化反馈分析，并创建了可测试的假设，以利用观测和理论完善其提出的不确定性范围。为了实现这种故事线方法，研究推导了一个简单而定量的砧面积反馈表达式，该表达式依赖于当前可测量的云辐射效应和砧面积随变暖的分数变化。卫星观测显示，砧状云的辐射效应约为±1W m^-2，要求砧面积的分数变化幅度约为50%K^-1，以产生等于其下限的当前最佳估计的反馈。

研究通过定量理论和观察表明，砧面积的变化接近于约-4%K^-1。这限制了面积反馈，并导致他们的修正估计为0.02±0.07W m^-2K^-1，它比整体砧云反馈弱很多倍且更受限制。相比之下，该研究发现砧状云反照率反馈在理论上和观测上受到的限制要小得多，这给限制地球的气候敏感性造成了障碍。

附：英文原文

Title: Weak anvil cloud area feedback suggested by physical and observational constraints

Author: McKim, Brett, Bony, Sandrine, Dufresne, Jean-Louis

Issue&Volume: 2024-04-01

Abstract: Changes in anvil clouds with warming remain a leading source of uncertainty in estimating Earth’s climate sensitivity. Here we develop a feedback analysis that decomposes changes in anvil clouds and creates testable hypotheses for refining their proposed uncertainty ranges with observations and theory. To carry out this storyline approach, we derive a simple but quantitative expression for the anvil area feedback, which is shown to depend on the present-day measurable cloud radiative effects and the fractional change in anvil area with warming. Satellite observations suggest an anvil cloud radiative effect of about ±1Wm^-2, which requires the fractional change in anvil area to be about 50%K^-1 in magnitude to produce a feedback equal to the current best estimate of its lower bound. We use quantitative theory and observations to show that the change in anvil area is closer to about -4%K^-1. This constrains the area feedback and leads to our revised estimate of 0.02±0.07Wm^-2K^-1, which is many times weaker and more constrained than the overall anvil cloud feedback. In comparison, we show the anvil cloud albedo feedback to be much less constrained, both theoretically and observationally, which poses an obstacle for bounding Earth’s climate sensitivity.

DOI: 10.1038/s41561-024-01414-4

Source: https://www.nature.com/articles/s41561-024-01414-4