Potsdam Institute for Climate Impact Research, Leibniz Association, D-14473 Potsdam, Germany
Proc Natl Acad Sci U S A. 2017 Oct 24;114(43):11333-11337. doi: 10.1073/pnas.1712062114. Epub 2017 Oct 9.
The bulk of Earth's coal deposits used as fossil fuel today was formed from plant debris during the late Carboniferous and early Permian periods. The high burial rate of organic carbon correlates with a significant drawdown of atmospheric carbon dioxide (CO) at that time. A recent analysis of a high-resolution record reveals large orbitally driven variations in atmospheric CO concentration between [Formula: see text]150 and 700 ppm for the latest Carboniferous and very low values of 100 [Formula: see text] 80 ppm for the earliest Permian. Here, I explore the sensitivity of the climate around the Carboniferous/Permian boundary to changes in Earth's orbital parameters and in atmospheric CO using a coupled climate model. The coldest orbital configurations are characterized by large axial tilt and small eccentricities of Earth's elliptical orbit, whereas the warmest configuration occurs at minimum tilt, maximum eccentricity, and a perihelion passage during Northern hemisphere spring. Global glaciation occurs at CO concentrations <40 ppm, suggesting a rather narrow escape from a fully glaciated Snowball Earth state given the low levels and large fluctuations of atmospheric CO These findings highlight the importance of orbital cycles for the climate and carbon cycle during the late Paleozoic ice age and the climatic significance of the fossil carbon stored in Earth's coal deposits.
今天用作化石燃料的大部分地球煤炭矿床是在石炭纪晚期和二叠纪早期由植物残骸形成的。有机碳的高埋藏率与当时大气二氧化碳（CO）的大量减少有关。最近对高分辨率记录的分析表明，在石炭纪晚期，大气 CO 浓度在[Formula: see text]150 到 700 ppm 之间存在大的轨道驱动变化，而在早二叠世，其浓度非常低，为 100 [Formula: see text] 80 ppm。在这里，我使用耦合气候模型探索了地球轨道参数和大气 CO 变化对石炭纪/二叠纪边界周围气候的敏感性。最冷的轨道配置的特点是地球椭圆轨道的大倾斜和小偏心率，而最温暖的配置发生在最小倾斜、最大偏心率和北半球春季的近日点通过时。全球冰川作用发生在 CO 浓度<40 ppm 时，这表明在大气 CO 水平低且波动大的情况下，从完全冰川覆盖的雪球地球状态中逃脱的可能性相当小。这些发现强调了轨道周期对晚古生代冰期气候和碳循环的重要性，以及储存在地球煤炭矿床中的化石碳的气候意义。
