Science News reports:

A barrage of intense, wild swings in climate conditions may have fueled the largest mass extinction in Earth’s history. A re-creation of how ancient sea surface temperatures, ocean and atmosphere circulation, and landmasses interacted revealed an Earth plagued by nearly decade-long stints of droughts, wildfires and flooding.

Researchers knew that a spike in global temperatures — triggered by gas emissions from millions of years of enormous volcanic eruptions in what is now Siberia — was the likely culprit behind a mass extinction roughly 252 million years ago. But it was the resulting catastrophic “mega El Niños” that whiplashed ecosystems, ultimately wiping out some 90 percent of all ocean species and 75 percent of those on land, researchers report in the Sept. 13 Science.

“[The findings] really build into an emerging picture that it’s a bit more nuanced of an extinction than we previously had appreciated,” says Erik Gulbranson, a sedimentary geochemist at Gustavus Adolphus College in Saint Peter, Minn., who was not involved with the new study.

Researchers have wondered why the Great Dying that played out at the border of the Permian and Triassic periods was so brutal for life on Earth. “We’ve got this intense global warming, but we have other episodes of global warming in the geological record that don’t do anything nearly as bad to ecosystems as this,” says paleontologist David Bond at the University of Hull in England.

While a sharp increase in sea surface temperature plus the resulting collapse in the warmer ocean’s ability to hold dissolved oxygen would have been abysmal for ocean organisms, it wasn’t clear what drove the extinction of life on land or why these organisms couldn’t just move to the cooler poles.

Part of the answer may lie in much shorter-term oscillations in paleoclimate. [Continue reading…]