Global warming was the leading cause behind the Permian mass extinction in the oceans about 252 million years ago that left marine animals gasping for breath, according to a new study by scientists from the University of Washington (UW) and Stanford.
Scientists believe that more than two-thirds of the life on earth was wiped out during the Permian mass extinction that happened about 252 million years ago. Also known as "the Great Dying", the event marked the biggest mass extinction in the history of the Earth.
Scientists suspect that massive volcanic eruptions in Siberia likely triggered the event which obliterated majority of plant and animal life on the planet. The eruptions emitted enough carbon dioxide in the atmosphere to warm the planet by about 10 degrees Celsius. As the earth warmed, the oceans became inhospitable to life, resulting in the extinction of up to 96 per cent of the marine species at that time.
In the current study, published in journal Science, scientists created a climate model, in which all continents were reunited as Pangaea. The model was used in combination with the published data and paleoceanographic records from earlier studies.
To match the conditions at the time of the Great Dying the researchers raised the level of greenhouse gases in the climate model up to the point, which increased the tropical ocean temperatures at the surface by about 10 degrees Celsius.
The model exhibited dramatic changes in the oceans, which lost about 80 per cent of their oxygen on average. With increasing ocean temperatures, the metabolism of animals sped up, but there was little oxygen left in the warmer waters to support life.
"This is the first time that we have made a mechanistic prediction about what caused the extinction that can be directly tested with the fossil record, which then allows us to make predictions about the causes of extinction in the future," said Justin Penn, a UW doctoral student in oceanography, and the first author of the study.
The results also showed that the hardest hit organisms were those that were most sensitive to oxygen and lived far from the tropics. High-latitude species were almost completely wiped out.
The team also verified their results against fossil-record patterns from the time of the extinction and found that they correlated closely.
Scientists believe the situation that existed during the late Permian is somewhat similar to conditions found today, with increasing greenhouse gases causing the earth to warm day by day.
"Under a business-as-usual emissions scenarios, by 2100 warming in the upper ocean will have approached 20 per cent of warming in the late Permian, and by the year 2300 it will reach between 35 and 50 per cent," Penn said.
"This study highlights the potential for a mass extinction arising from a similar mechanism under anthropogenic climate change."
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