Acid rain and ozone depletion probably contributed to the greatest extinction Earth has ever seen.

Massive volcanic eruptions occurred in Siberia at around the same time as the extinction event that ended the Permian era some 252 million years ago, but it is not clear how the two are linked. Benjamin Black of the Massachusetts Institute of Technology in Cambridge and his colleagues analysed the amounts of gases trapped in the Siberian lava. They put the data into a global climate model describing the ancient atmosphere.

The levels of some gases emitted by the magma, such as carbon dioxide and sulphur dioxide, would have turned rainfall to acid. Others, such as methyl chloride, may have chewed away at the planet's protective ozone layer.

Geology (2013)