A vision of a future greenhouse earth if greenhouse gases are not controlled

(ORDO NEWS) — Throughout the history of our planet, the Earth has fluctuated between a hothouse and an icy climate.

Today our home is supposed to be in a period of global cooling, but human emissions of greenhouse gases are reversing this natural trend at a rapid and unprecedented pace.

In one of the last times the Earth went from icehouse to hothouse so quickly and abruptly, about 304 million years ago, our planet experienced a major upheaval.

During the Kasimov-Gzhel Frontier (KGB), atmospheric carbon levels doubled in about 300,000 years, from about 350 ppm to 700 ppm. Now, according to new research, about 23 percent of the seafloor was deprived of oxygen during this period.

The findings are based on a new analysis of trace elements in an ancient black shale slab in South China. The carbon and uranium isotopes in this rock indicate that in addition to global warming, rising sea levels and melting glaciers, we should also be concerned about ocean anoxia.

Anoxia is defined as a lack of oxygen. It can result from climate change because when ice caps melt and add fresh water to the surface of the ocean, it prevents atmospheric oxygen from diluting and circulating in the sea.

Under extreme anoxic conditions, life in the ocean struggles to survive. Even areas of low oxygen, called hypoxia, are known as “dead zones”.

The new findings are supported by previous studies of ancient bottom rocks in South China, which revealed significant loss of biodiversity in the sea during the KGB turnaround.

In modeling these ancient climate changes, the authors of the current study realized the importance of the time factor.

“If you raise CO2 levels in the greenhouse world by the same amount, there won’t be much effect, but ice houses seem to be much more sensitive to changes and marine anoxia,” explains sedimentary geochemist Isabelle MontaƱez of the University of California, Davis.

In other words, if human emissions increased rapidly during a natural period of global warming rather than global cooling, ocean anoxia would not pose such a big threat.

Perhaps the reason lies in the fact that greenhouse gases in the greenhouse world are already at a high level, so emissions do not affect the melting of ice sheets and permafrost as much.

But during a period of global cooling, there are more ice sheets and glaciers, trapping fresh water, ready to penetrate the surface of the ocean and prevent the dissolution of oxygen.

Researchers suspect that the massive release of carbon that caused climate change between 290 and 340 million years ago was likely stimulated by volcanic eruptions.

Extensive wildfires, as well as melting permafrost, would add even more carbon to the atmosphere.

However, these are just ideas. Researchers have not been able to trace the exact cause of carbon emissions during the KGB, but their results show a clear spike in greenhouse gas emissions followed by significant sea level rise and anoxia.

“Massive carbon release with abrupt warming has repeatedly occurred during greenhouse states, and these events have led to episodes of ocean deoxygenation and extinctions,” the authors write.

“Records of these paleo-events, combined with biogeochemical modeling, provide clear evidence that with continued warming, modern oceans will experience significant deoxygenation.”


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