Research press release


Nature Geoscience

Carbon emissions rate unprecedented in the past 66 million years




Richard Zeebeたちは、海洋堆積物に記録されている炭素放出の時期と気候変動の時期とを比較し、両者が基本的には同じ時期に起きていることを見つけた。気候および炭素循環のモデルを用いて、Zeebeたちは、そのようなほぼ同時期に起きた変化から、PETMの炭素放出が現代では毎年約100億トンであることに対し、少なくとも4000年間にわたり毎年6~11億トンの間の速度で起きたことが伺えると示している。

同時掲載のNews & Views記事でPeter Stassenは、「PETM放出がZeebeたちが提案しているような遅い時間スケールで起きたのならば、遠海の海洋生態系は移動や進化によって環境変動に適応するために十分な時間があった可能性がある。従って、現在の変化の速度は、現代の海洋生態系とその構成要素の適応容量を凌駕している可能性は残っている」と述べている。

The rate of carbon emissions during a period of abrupt warming 55.8 million years ago was ten times slower than current anthropogenic emissions, reports a paper published online in Nature Geoscience. The study shows that the current rate at which carbon is being released into the atmosphere is unprecedented in at least the past 66 million years.

During the abrupt warming known as the Palaeocene-Eocene Thermal Maximum (PETM), massive emissions of greenhouse gases caused a global warming of at least 5 °C. The PETM has been considered the closest analogue to current climate change, but the actual magnitude and rate of carbon emissions during the PETM have been difficult to determine.

Richard Zeebe and colleagues compared the timing of climate change with the timing of carbon emissions as recorded by marine sediments, and found that they occurred at essentially the same time. Using a climate and carbon cycle model, they show that such a near-concurrent change suggests the PETM carbon emissions occurred over a period of at least 4,000 years, at a rate of between 0.6 to 1.1 billion tonnes of carbon per year, compared with modern emissions that are on the order of 10 billion tonnes of carbon per year.

In an accompanying News & Views article, Peter Stassen writes: “if PETM emissions occurred over a slower timescale as proposed by Zeebe et al., pelagic marine ecosystems may have had sufficient time to adapt to environmental changes through migration or evolution. It therefore remains possible that the current rates of change might exceed the adaptive capacity of modern marine ecosystems and their constituents.”

doi: 10.1038/ngeo2681


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