Science

New study offers surprising timeline for sixth Earth mass extinction

New study offers surprising timeline for sixth Earth mass extinction
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A climate scientist at Tohoku University in Japan has compiled the numbers and doesn’t think today’s mass extinction event will match those of the previous five. At least not for many more centuries.

More than once in the past 540 million years, the earth has lost most of its species in a relatively short geological time span.

These are known as mass extinctions and often follow close behind climate changebe it extreme warming or extreme cooling triggered by asteroids or volcanic activity.

When Kunio Kaiho tried to quantify the stability of the Earth’s average surface temperature and the planet’s biodiversity, he found a largely linear effect. The greater the temperature change, the greater the extent of quenching.

In global cooling events, the largest mass extinctions occurred when temperatures fell by about 7°C. But for global warming events, Kaiho found that the largest mass extinctions occurred at about 9°C of warming.

That’s a lot higher than previous estimatessuggesting that a temperature of 5.2°C would lead to a large marine mass extinction comparable to the previous “Big Five”.

In this way, by the end of the century, modern global warming is in perspective on track to raise surface temperatures by as much as 4.4°C.

“Global warming of 9°C will not be reflected in the anthropocene at least up to 2500 in the worst case scenario”, Kaiho forecast.

Kaiho does not deny that there are many extinctions on land and in the sea already due to climate change; he just doesn’t expect the same proportion of losses as before.

However, it is not just the magnitude of climate change that is endangering species. The speed at which it occurs is critical.

The largest mass extinction event on Earth then killed 95 percent of known species and happened over 60,000 years about 250 million years ago. But today’s warming is happening in a much shorter time, thanks to human emissions of fossil fuels.

Perhaps the sixth extinction event on Earth will see more species go extinct, not because the warming is so great, but because the changes have been so rapid that many species have been unable to adapt.

“Predicting the future magnitude of anthropogenic extinctions using only surface temperature is difficult because the causes of anthropogenic extinctions are different from the causes of mass extinctions in geologic time,” Kaihu said admits.

However scientists split the data, it’s clear that many species are doomed if we can’t stop climate change.

The exact percentage of losses and the timing of those losses remain up for debate.

The study was published in Biogeosciences.

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