2026-06-09 中国科学院（CAS）
◆研究では、全球植生動態モデル（LPJ-LMfire）と炭素同位体質量収支モデルを組み合わせ、PETM期の陸域炭素循環を定量評価した。その結果、中程度の温暖化では植生による炭素吸収が増加するものの、土壌からの炭素放出を補えず、約66PgCの純放出が生じた。さらに温暖化が進行すると臨界点を超え、植生・土壌の炭素貯蔵量が急減し、最大約900PgCもの陸域炭素が失われたと推定された。また、PETMの炭素放出は単一要因ではなく複数の炭素源の相互作用による可能性が高いことも示された。
◆研究は、将来の気候変動において陸域生態系へ過度に炭素吸収を期待することの危険性を警告し、気候―炭素循環の正のフィードバックによる温暖化加速リスクを定量的に示している。
＜関連情報＞
- https://english.cas.cn/newsroom/research-news/202606/t20260610_1161467.shtml
- https://www.nature.com/articles/s43247-026-03682-x
暁新世-始新世温暖化極大期における陸上炭素蓄積の脆弱性 Terrestrial carbon stock vulnerability during the Paleocene-Eocene Thermal Maximum
Xiaoqi Fang,Kenji Izumi,Shijun Jiang,Jiang Zhu,Tao Su & Shufeng Li
Communications Earth & Environment Published:29 May 2026
DOI:https://doi.org/10.1038/s43247-026-03682-x Unedited version
Figure 1. Simulated response of global terrestrial carbon stocks to pre-PETM and PETM climates.
Abstract
The Paleocene-Eocene Thermal Maximum is a key analog for future climate change. However, how terrestrial ecosystems responded to this extreme warming remains uncertain. We integrate a dynamic global vegetation model with a carbon-isotope mass-balance framework to quantify terrestrial carbon-cycle feedbacks. Our simulations reveal that ancient high-latitude carbon stocks were vast but highly sensitive to extreme warming. We identify a fundamental non-linearity in the terrestrial response: while moderate warming triggers ecosystem shifts, extreme warming drives an abrupt collapse of land carbon, releasing up to ~900 petagrams. This decline stems from a bipolar ecological shift where massive tropical forest loss and accelerated soil heterotrophic respiration overwhelm high-latitude greening and carbon dioxide fertilization. Furthermore, hybrid scenarios combining terrestrial release of sedimentary methane and volcanic carbon dioxide provide the best fit to the geological record. We identify critical thermal thresholds, warning that future terrestrial carbon-climate feedbacks could be more severe than currently projected.
