A climate scientist at Tohoku University in Japan ran the data and doesn’t think today’s mass extinction event will match the previous five. At least not for several centuries to come.
On more than one occasion over the past 540 million years, Earth has lost most of its species in relatively short geologic time periods.
These are known as mass extinction events, and they often follow climate change very closely, whether triggered by extreme warming or extreme cooling, asteroids or volcanic activity.
When Kunio Kaiho tried to estimate the stability of the Earth’s average surface temperature and the biodiversity of the planet, he found a large-scale linear effect.
The greater the change in temperature, the greater the extent of extinction. For global cooling events, mass extinctions occurred when temperatures fell by about 7 °C.
But for global warming events, Kaiho found that the highest mass extinctions occur at temperatures of about 9°C. This is much higher than previous estimates, which suggested that a warming of 5.2°C would cause an ocean mass extinction similar to the previous ‘big five’.
To put this in perspective, by the end of the century, modern global warming is on track to increase surface temperatures by 4.4 degrees Celsius. “9°C global warming will not appear in the worst-case scenario until at least 2500 in the Anthropocene,” Caiho predicts.
Kaiho is not denying that many extinctions are already occurring on land and in the ocean due to climate change. He doesn’t expect similar extent of misfortunes as in the past.
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Yet, it is not just the degree of climate change that threatens species. The speed at which this happens is vital. The largest mass extinction event on Earth killed 95 percent of known species at the time and occurred over 60,000 years ago, about 250 million years ago.
Yet, the present warming is going on a lot more limited time scale thanks to human outflows of petroleum derivatives. Perhaps Earth’s sixth extinction event will kill more species not because the warming is so intense, but because the changes happened so fast that many species could not adapt.
“Anticipating the extent of future anthropogenic annihilations utilizing surface temperature alone is troublesome in light of the fact that the reasons for anthropogenic terminations are not the same as the reasons for mass eliminations in geologic time,” Kaiho concedes.
