加拿大麦吉尔大学Liu Lei团队最新的研究成果认为，在气候变暖的情况下，云层减少了陆地上空的下降流长波辐射。2025年1月15日出版的《自然》发表了这项成果。

据了解，云层极大地影响着地球的能量平衡。观测受限制的云辐射反馈是一种明显不确定的气候反馈机制，对改进气候变化的预测至关重要，但到目前为止，它仍然是一个理想的目标，海洋和陆地的反馈可能馈不同。

研究人员展示了大平原南部地区陆地上的局部负表面长波云反馈，受到光谱分辨下流长波辐射的直接长期观测的限制。大平原南部站点地区的负云反馈值为-1.77±1.15μm，这表明云的变化可能部分地调节，陆地上温室气体浓度的增加和大气温度升高的变暖效应。

具体来说，该结果来源于一种最佳的光谱指纹方法，方法旨在通过在光谱分辨辐射的长期记录中，利用其独特的光谱特征，将表面长波云反馈与其他表面作用力和反馈分离开来。

此外，研究结果还显示，结果并非特定于站点，在再分析和卫星数据集中，通常在陆地上观察到负的地表长波云反馈，主要是由变暖气候下低云覆盖减少引起的。研究结果强调，该发现建立了验证陆地气候模式性能所需的，辐射作用力和反馈的关键观测基准。

附：英文原文

Title: Clouds reduce downwelling longwave radiation over land in a warming climate

Author: Liu, Lei, Huang, Yi, Gyakum, John R.

Issue&Volume: 2025-01-15

Abstract: Clouds greatly influence the Earth’s energy balance. Observationally constraining cloud radiative feedback, a notably uncertain climate feedback mechanism, is crucial for improving predictions of climate change but, so far, remains an elusive objective, and the feedback may be different over the ocean versus over land. Here we show a local negative surface longwave cloud feedback over land at the southern Great Plains site, constrained by direct long-term observation of spectrally resolved downwelling longwave radiance. This negative cloud feedback at the southern Great Plains site causes a 1.77±1.15Wm^-2 per decade change in downwelling longwave radiation and suggests that cloud changes may partially modulate the warming effect of increased greenhouse gas concentrations and atmospheric temperatures over land. Specifically, our results are derived from an optimal spectral fingerprinting method designed to separate surface longwave cloud feedback from other surface forcings and feedbacks, by making use of their unique spectral signatures1 in the long-term record of spectrally resolved radiances. Furthermore, we show that the results are not site specific: negative surface longwave cloud feedbacks, primarily induced by decreasing low cloud cover in warming climates, are commonly observed over land in reanalysis and satellite datasets. Our findings establish a pivotal observational benchmark of radiative forcing and feedback needed for validating climate model performance over land.

DOI: 10.1038/s41586-024-08323-x

Source: https://www.nature.com/articles/s41586-024-08323-x