Understanding the causes of variations in global atmospheric methane concentration (GAMC) is an important issue in the study of global climatic changes. Long-term GAMC varied rhythmically on glacial-interglacial timescales, and broadly followed the orbital/suborbital cycles in northern hemisphere solar insolation. Yet the late Holocene has witnessed an increasing GAMC trend since the mid-Holocene, which decouples with the global atmospheric CO2 concentration trend and the northern hemisphere solar insolation trend. The causes of this decoupling have been extensively studied, but remain highly debated. Here we show that the Holocene GAMC trend closely follows the long-term trend in global low latitude wetland extent as inferred from our lake-level reconstruction and from other existing hydroclimate records. We contend that changes in low latitude wetland extent play an important role in shaping the GAMC trend. We propose that reduced low latitude wetland areas during the mid-Holocene, which were likely due to the submersion of tropical wetlands by rising sea levels, and reduced low latitude wetland areas inferred from lower lake levels, could be responsible for the observed mid-Holocene GAMC drop. Increasing global low latitude wetland areas during the late Holocene are likely responsible for the contemporary increasing GAMC trend.

中文翻译：

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低纬度湿地面积变化对全新世全球大气甲烷浓度趋势的可能影响


了解全球大气甲烷浓度 （GAMC） 变化的原因是世界上气候变化研究中的一个重要问题。长期 GAMC 在冰期-间冰期时间尺度上有节奏地变化，并大致遵循北半球日照的轨道/亚轨道周期。然而，自全新世中期以来，全新世晚期见证了 GAMC 趋势的增加，这与全球大气 CO2 浓度趋势和北半球日照趋势脱钩。这种脱钩的原因已经得到了广泛的研究，但仍然存在高度争议。在这里，我们表明全新世 GAMC 趋势与全球低纬度湿地范围的长期趋势密切相关，这从我们的湖位重建和其他现有的水文气候记录中推断出来。我们认为，低纬度湿地范围的变化在塑造 GAMC 趋势中起着重要作用。我们认为，全新世中期低纬度湿地面积的减少可能是由于海平面上升淹没了热带湿地，以及从较低的湖位推断的低纬度湿地面积减少，可能是观察到的全新世中期 GAMC 下降的原因。全新世晚期全球低纬度湿地面积的增加可能是当代 GAMC 增长趋势的原因。