近日，北京大学彭书时团队研究了大气甲烷季节振幅的变化趋势。相关论文于2025年5月7日发表在《自然》杂志上。

甲烷是一种重要的温室气体，其大气浓度自工业化前以来几乎增加了两倍。大气甲烷混合比随季节变化，自20世纪80年代以来，季节循环幅度（SCA）在北部高纬度地区有所下降，在亚热带和热带地区有所增加。这些相反的SCA趋势可以帮助理解全球甲烷预算的长期变化，因为甲烷排放和汇对SCA有相反的影响。然而，甲烷SCA的趋势尚未得到详细探讨。

研究组使用了一套大气传输模型模拟，并将甲烷季节性振幅的观测趋势归因于排放的变化和与羟基自由基（OH）反应的大气汇。结果发现，北部高纬度地区的幅度减小主要是由于气候变暖导致的自然排放量（如湿地）增加，这为之前的研究提供了证据，表明气候反馈是积极的。  

相比之下，亚热带和热带甲烷振幅的增加主要归因于OH氧化的加强。该研究结果为自1984年以来对流层OH浓度增加10 ± 1%提供了独立证据，随着大气甲烷浓度的增加，这表明大气中甲烷汇增加21 ± 1%。

附：英文原文

Title: Trends in the seasonal amplitude of atmospheric methane

Author: Liu, Gang, Shen, Lu, Ciais, Philippe, Lin, Xin, Hauglustaine, Didier, Lan, Xin, Turner, Alexander J., Xi, Yi, Zhu, Yu, Peng, Shushi

Issue&Volume: 2025-05-07

Abstract: Methane is an important greenhouse gas1 and its atmospheric concentration has almost tripled since pre-industrial times2,3,4. Atmospheric methane mixing ratios vary seasonally, with the seasonal cycle amplitude (SCA) having decreased in northern high latitudes and increased in the subtropics and tropics since the 1980s5,6. These opposing SCA trends can help understanding of long-term changes in the global methane budget, as methane emissions and sinks have opposing effects on the SCA5. However, trends in the methane SCA have not yet been explored in detail5,6. Here we use a suite of atmospheric transport model simulations and attribute the observed trends in the seasonal amplitude of methane to changes in emissions and the atmospheric sink from reaction with the hydroxyl radical (OH). We find that the decreasing amplitude in the northern high latitudes is mainly caused by an increase in natural emissions (such as wetlands) owing to a warmer climate, adding evidence to previous studies suggesting a positive climate feedback7,8,9. In contrast, the enhanced methane amplitude in the subtropics and tropics is mainly attributed to strengthened OH oxidation. Our results provide independent evidence for an increase in tropospheric OH concentration10,11 of 10±1% since 1984, which together with an increasing atmospheric methane concentration suggests a 21±1% increase in the atmospheric methane sink.

DOI: 10.1038/s41586-025-08900-8

Source: https://www.nature.com/articles/s41586-025-08900-8