Planet Earth has experienced at least five mass extinctions over the past 500 million years or so. The largest mass extinction, marking the boundary between the Permian and Triassic periods, resulted in the loss of close to 95% of all species of organisms living at the time.

Until recently it has not been possible to determine exactly when the mass extinction occurred or how long it lasted. But now, using better dating techniques, scientists have pinpointed the Earth’s largest mass extinction more precisely, to between 251.88 and 251.94 million years ago. That’s a duration of just 60,000 years (0.06 million years); much shorter than previously thought. What could have caused such a rapid and devastating die-off? Scientists don’t know for sure, but it’s worth noting that the extinction coincided with a massive rise in atmospheric CO2 levels to over 2,000 parts/million (ppm), perhaps due to a period of increased volcanic activity. That in turn may have caused a substantial global warming, including warming of the oceans.

Some people think that as a result of human activity (the release of CO2 into the atmosphere as the result of the burning of fossil fuels) we may be at the beginning of a new period of mass extinction. Its worth noting that atmospheric CO2 levels are currently around 390 ppm, clearly up from 280 ppm before the industrial revolution but nowhere near the levels seen in the last extinction. Is that good news, or bad? No one knows for sure. In another 60,000 years we might know the answer, but by then it would be too late.

You and I will be long gone by then….

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