近日，美国俄勒冈州立大学Julia Marks-Peterson团队报道了在过去的300万年里，大气中二氧化碳和甲烷的含量大致稳定。相关论文发表在2026年3月18日出版的《自然》杂志上。

南极冰芯记录揭示了过去80万年来大气温室气体的连续变化，清晰描绘了晚更新世典型的冰期-间冰期旋回特征。对蓝冰区的研究已将这一记录延伸至200万年前，但此前大气温室气体的演变规律仍属未知。

研究组通过分析覆盖31万至50万年前的离散冰芯快照，发现距今290万至120万年间甲烷（CH₄）平均浓度无显著变化，二氧化碳（CO₂）仅呈现约20ppm的小幅下降，随后在中更新世转型期保持稳定（±10ppm）。这些发现基于南极艾伦山蓝冰区（BIA）钻探的浅层冰芯。由于受到沉积后过程的扰动，这些记录较为复杂，可能代表了冰期旋回的平均状态，其权重受气候依赖的累积速率差异影响（该研究假定累积速率恒定）。

通过利用CO₂中稳定碳同位素（δ¹³C）校正受呼吸作用影响的280万至310万年前样本，获得的大气CO₂平均浓度与早更新世（250±10ppm）相比无显著差异。尽管南极蓝冰区的古气候档案具有复杂性，但该研究表明冰芯温室气体测量可追溯至上新世晚期，为全球降温与海平面下降时期的地球气候系统提供了快照。

附：英文原文

Title: Broadly stable atmospheric CO2 and CH4 levels over the past 3 million years

Author: Marks-Peterson, Julia, Shackleton, Sarah, Higgins, John, Severinghaus, Jeffrey, Yan, Yuzhen, Buizert, Christo, Kalk, Michael, Beaudette, Ross, Hishamunda, Valens, Eves, Demetria, Carter, Austin, Kurbatov, Andrei, Epifanio, Jenna, Morgan, Jacob, Nesbitt, Ian, Bender, Michael, Brook, Edward

Issue&Volume: 2026-03-18

Abstract: Ice core records from Antarctica document continuous variations in atmospheric greenhouse gases over the past 800,000years, delineating the glacial–interglacial cycles that characterize the late Pleistocene epoch1,2,3. Studies of blue ice areas4 have extended these records back to 2 million years (Myr)5,6. The evolution of atmospheric greenhouse gases before this time thus remains uncertain. Here we use discontinuous ice core snapshots spanning 3.1–0.5Myr ago (Ma) to show no marked change in mean methane (CH4) and a small decline of about 20ppm in carbon dioxide (CO2) between 2.9Ma and 1.2Ma, followed by stable concentrations (±10ppm) across the mid-Pleistocene Transition. Our findings are based on the shallow ice cores drilled in the Allan Hills Blue Ice Area (BIA), Antarctica7. The records are complicated by postdepositional processes and probably represent averages over glacial cycles weighted by climate-dependent differences in accumulation rates (which we assume to be constant). Samples aged 2.8–3.1Myr, affected by respiration and corrected using stable carbon isotopes in CO2 (δ13C), yield mean atmospheric CO2 levels indistinguishable from the early Pleistocene (250±10ppm). Although palaeoclimate archives from Antarctic blue ice areas are complex, our records show that measurements of greenhouse gases in ice cores can be extended to the late Pliocene epoch, providing snapshots of Earth’s climate system over a time of global cooling7,8 and falling sea level9.

DOI: 10.1038/s41586-025-10032-y

Source: https://www.nature.com/articles/s41586-025-10032-y