Three New Papers: Permian Mass Extinction Coincided With Global Cooling—Not Global Warming

In the past, it has been widely reported that high and abruptly changing CO2 concentrations during the Permian led to climate conditions that were “too hot for complex life to survive” on the planet.

Today, scientists have determined that the opposite may be true: the Permian mass extinction event occurred during a period of global cooling, expansive ice sheet growth, relatively low CO2 levels, and a marine-habitat-destroying sea level drop of 100 meters.

Image Source: Kani et al., 2018

A year ago, the press release for a paper published in Scientific Reports argued that during the Permian mass extinction event, “the majority of marine species” were killed off by an “extreme cold” period that coincided with widespread glaciation and a dramatic drop in global sea levels.

“Analysis of the newly dated layers showed a significant reduction of seawater levels during the [Permian] extinction event. The only explanation for such a dramatic decrease in water levels is a sudden increase in ice. The ice age lasted just 80,000 years, but the extreme cold was enough to kill off the majority of marine species.”

Within the last few months, at least two more papers have been published that also affirm that the Permian mass extinction event that annihilated up to 90% of marine species and 70% of land-dwelling species coincided with extreme global cooling, ice sheet expansion over land, and dramatically-falling sea levels — 100 meters lower than they were in previously warmer climates.

The lowering of sea levels alone may have been enough to destroy a substantial percentage of marine habitats, and the expansion of ice sheets may have austerely limited the habitat ranges for land-dwelling fauna.

CO2 Concentrations And Mass Extinctions: A Questionable Link  

Further analysis reveals that, contrary to commonly popularized claims, neither the Ordovician mass extinction event nor the Permian mass extinction event had a clear causal link to atmospheric CO2 concentrations.

Indeed, it has long been documented that CO2 concentrations may have fluctuated between about 280 ppm and 2800 ppm during the Permian, with the low CO2 values coinciding with cool periods and the high values coinciding with warm periods (Saunders and Reichow, 2009).

While both extinction events occurred during global cooling periods accompanied by significantly lowered sea levels, the CO2 concentrations were relatively high (“over 2000 ppm”) during the Ordovician but relatively low (~300 ppm) during the Permian extinction event.

The latter CO2 values would appear to undermine the contention that CO2-driven ocean “acidification” and too-high CO2 concentration levels were causally connected to the extinction of marine species during the Permian.

And the relatively high CO2 values during the Ordovician are not compatible with the accompanying global cooling, glaciation, and plummeting sea levels of that period.

In sum, a growing body of evidence suggests that commonly-held assumptions about a direct causal link between CO2 concentration flux and mass extinction events may not be as clear as previously thought.

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