Strong El Niños primed Earth for mass extinction
By Paul Voosen, Science.
Excerpt: Some 250 million years ago, more than 80% of marine species and two-thirds of those on land died off in the end-Permian mass extinction—the closest life ever came to annihilation. Most scientists think massive volcanic eruptions in what is now Siberia triggered the event by spewing carbon dioxide (CO2) and warming the planet. But according to a modeling study published this week in Science, the Great Dying was primed by a mega–El Niño pattern in the global ocean of the time, leading to weather extremes that killed off forests and kicked off the extinctions. ...Geological evidence suggests that before the eruptions, atmospheric CO2 levels were likely about 400 parts per million (ppm), similar to the present day. As they began to tick up, the model showed profound El Niño events began to occur, says Alexander Farnsworth, a study co-author and paleoclimate modeler at the University of Bristol. ...Chaotic weather would have been unleashed worldwide, as happens during today’s El Niños. As CO2 levels rose to 800 ppm and beyond, the El Niños grew more fearsome than any in history, lasting up to 7 years. “You’re seeing this incredible heat buildup, which just persists,” Farnsworth says. ...The study raises the disturbing prospect that today’s rising greenhouse gas levels could trigger Permian-like mega–El Niños....