過去6000万年の大気中の二酸化炭素濃度
1Department of Earth Sciences, University of Bristol, UK. Paul.Pearson@Bristol.ac.uk
Nature
|August 30, 2000
まとめ
大気中の二酸化炭素 (CO2) レベルは,地球の初期のケノゾイク時代に高かったが,ミオセーンまで不規則に減少した. 現代のCO2レベルは,百万分500 (p.p.m.) 未満にとどまっている. それ以来. それ以来.
科学分野:
- 古代気候学 (paleoclimatology) とは,古代気候学 (paleoclimatology) とは,古代気候学 (paleoclimatology) とは,古代気候学 (paleoclimatology) とは,古代気候学 (paleoclimatology) とは
- 地質化学 地質化学
- 海洋学 海洋学 海洋学
背景:
- 過去の大気中の二酸化炭素 (CO2) 濃度を理解することは,地球の気候と温度を再構築するために極めて重要です.
- 初期ケノゾイク期のCO2レベル,その減少のタイミング,および長期的な規制メカニズムに関する不一致が存在します.
- 以前の推定では,現在と比較して,ケノゾイク初期 (約6000万年前) のCO2濃度が高いことが示唆されている.
研究 の 目的:
- 過去6000万年の大気中のCO2濃度を再構築する.
- 二酸化炭素濃度の低下を調査し,潜在的な制御要因を特定する.
- CO2の変動と気候との関係について,より正確なタイムラインを提供するためです.
主な方法:
- 古代プランクトンのフォラミニファー殻から採取したボロン同位体比を用いた.
- 大気中のCO2濃度を再構築するために,表面層の海水の推定pH.
- パレオセンの終わりから現在までの地質学的時間スケールを分析した.
主要な成果:
- 推定CO2濃度は,百万分2000個 (p.p.m.) を超えていた. パレオセンの末期とエオセンの初期 (60~5200万年前) の間でした.
- 55~4千万年前の二酸化炭素の不規則な減少が観察され,地質的な排出ガスの減少と炭素埋葬の増加と関連している可能性がある.
- 検出されたCO2濃度は500 p.p.m.以下でした. そして,ミオセンの初期 (2400万年前) 以降より安定しており,冷却期には一時的に減少した.
結論:
- この研究は,ケノゾイク期の大気中のCO2濃度の詳細な再構築を提供します.
- 火山によるガス排出の減少や炭素埋蔵の強化などのメカニズムが,CO2の長期的減少を促した可能性が高い.
- ミオセンの後のCO2レベルは著しく低下し,より安定しており,地球の炭素循環規制のシフトを示しています.
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