How increased CO2 emission led to greatest mass extinction

In a warning of how lethal increased carbon dioxide emission could be, researchers found the greatest extinction of all time that happened 252 million years ago was due to the huge amount of carbon dioxide the Earth's oceans absorbed from volcanic eruptions.

Acidity in the oceans, caused by extreme volcanic activity, triggered the greatest extinction of all time that wiped out more than 90 percent of marine species and more than two-thirds of the animals living on land, the findings showed.

"Scientists have long suspected that an ocean acidification event occurred during the greatest mass extinction of all time, but direct evidence has been lacking until now," said University of Edinburgh's Matthew Clarkson, who coordinated the study.

The findings could help scientists understand the threat posed to marine life by modern-day ocean acidification.

The amount of carbon added to the atmosphere that triggered the mass extinction was probably greater than today's fossil fuel reserves, the team said.

However, the carbon was released at a rate similar to modern emissions. This fast rate of release was a critical factor driving ocean acidification, researchers said.

The Permian-Triassic Boundary extinction took place over a 60,000 year period, researchers say.

Ocean acidification was the driving force behind the deadliest phase of the extinction, which dealt a final blow to an already unstable ecosystem, the researchers said.

The team analysed rocks unearthed in the United Arab Emirates - which were on the ocean floor at the time - to develop a climate model to work out what drove the extinction.

The rocks preserve a detailed record of changing oceanic conditions at the time.

The study was published in the journal Science.