Acid rain and ozone depletion helped make the Great Dying great

The Putorana Plateau, capped basalt released in the Siberian Traps eruptions.

Wikimedia Commons

Climate models usually end up in the news because of projections of future climate, but many researchers use the models to study other planets or the Earth's past. They can help test hypotheses about past climate events by comparing model simulations to estimates of past climates obtained from things like ice and sediment cores.

One climatic event that looms large in Earth's history is the end-Permian mass extinction about 252 million years ago—the worst mass extinction event on record. A volcanic event seems to have been at least partly to blame. Tremendously vast eruptions in Siberia coughed up lava flows and ash that may have covered an area nearly as large as Australia—a feature known as the Siberian Traps. During this event, some 90 percent of marine species disappeared, and species on land didn’t fare well, either.

Apart from the warming caused by all the carbon dioxide emitted by the eruptions, many researchers have explored the problems that volcanic gases might have caused for land-dwelling organisms. Currently, the pH of the ocean is dropping as we increase atmospheric CO₂, but at high enough levels of carbon dioxide, acidification of rain can become a problem as well. Add in volcanic emissions of sulfur dioxide—the same compound that we control in coal emissions to prevent acid rain—and the atmosphere would get even worse.