About 252 million years ago, the earth almost died.
In the oceans 96 percent of all species were killed. It is harder to determine how many earths disappeared, but the loss was comparable.
This mass extinction, at the end of the month of the Permit, was the worst in the history of the world, and it happened in a few thousand years – the glare of a geological eye.
On Thursday, a team of researchers offered a detailed account of how sea life was wiped out during the mass extinction of Permian-Triass. Global warming robbed the oceans of oxygen, they say, putting many species under so much stress that they died of.
Researchers have long known the general outlines of Permian-Triassic cataclysm. Just before the extinction, volcanoes in what now spread Siberia on a huge scale. The magma and lava they pushed forward produced large amounts of carbon dioxide.
Once in the atmosphere, the gas was in the heat. Researchers estimate that the surface of the ocean is heated by about 18 degrees Fahrenheit. Some scientists claim that this heat alone killed by animals.
Others believe that the heat reduces oxygen in the ocean and stifles the species that live there. Stones from mass death seem to have formed when at least part of the ocean lacked oxygen.
In previous research, Dr. Deutsch explored how living animals adapt to temperature and oxygen levels in the garden. For example, animals with rapid metabolism need a lot of oxygen, so that they can not live in parts of the ocean where oxygen falls below a certain threshold.
Hot water makes the challenge even more difficult. Heater water can not hold as much dissolved oxygen as cold water. Even worse, hot water can also increase the metabolism of an animal, which requires more oxygen just to keep alive.
Cod does not exist, for example, below a latitude that goes roughly from New England to Spain. South of that line is heat and low oxygen just too good for the species.
Dr. Deutsch and Justin Penn, a graduate student, recruited the world at the end of the month with a large-scale computer simulation, complete with a heat exchange and a circulating sea.
When the Siberian volcanoes flooded the virtual atmosphere with carbon dioxide, the atmosphere was warmed. The sea was also warmed – and according to the model, it began to lose oxygen.
Some parts lost more than others. On the surface, for example, fresh acid was prepared from photosynthetic algae. But as the sea warmed, its circulation currents also slowed, the model showed.
Oxygen-low water struck down to the bottom of the ocean, and the depth was too deep.
Rising temperatures and immersion of oxygen must have made enormous oscillations of the oceans unprofitable. Some species survived here and there. But most completely disappeared.
“Everything lost a lot of habitat and created the risk of eradication,” says Dr. Deutsch. “But the risk was actually higher in places that were cold. It was a little surprising.”
You could expect that animals near the equator would be at greater risk of the water being hot at first. But Dr. Deutsch’s model suggested a completely different type of apocalypse.
Animals in acidic cold water could not handle the sudden drop, while in tropical waters they were already adapted to poor acidity. And the cold water species could not find refuge elsewhere.
To test their simulation, the researchers collaborated with Jonathan Payne and Erik Sperling, palaeontologists at Stanford University. They dug into a large online database of fossils to map out the risks of eradication at different latitudes during the disaster.
When they finished their analysis, they sent their grave to Seattle. Dr. Deutsch and Mr. Penn compared it to the prediction of their computer model.
They matched. “This was the most exciting moment in my scientific life,” says Dr. Deutsch.
Michael Paleontologist at the University of Bristol in England, who was not involved in the study, said that it solved the role of heat and oxygen as the cause of mass extinction. “This is a clear case that the two are of course linked,” he said.
The new study offers an important warning to people in the coming centuries.
The Siberian volcano finally gave much more carbon dioxide to the atmosphere than we will ever let out by burning fossil fuels. But our annual carbon dioxide emissions are actually higher.
The coal we released in the past two centuries has already made the atmosphere warmer and the ocean has absorbed much of that heat. And now, just as during Permian-Triass extinction, the sea loses oxygen. Over the last fifty years, oxygen levels have fallen by 2 percent.
“The way the Earth system is now responding to carbon dioxide build up is exactly the same as we have seen it responded earlier,” says Dr. Kump.
How much warmer the planet will get is up to us. It will take a huge international effort to keep the increase below about 4 degrees Fahrenheit.
If we continue to use all fossil fuels on Earth, it can heat as much as 17 degrees Fahrenheit before 2300.
When the ocean is heated, oxygen levels will continue to fall. If ancient history is a guide, consequences for life – especially marine life in the colder parts of the ocean – will be disastrous.
“Left unclear, climate warming sets our future on the same scale as some of the worst events in geological history,” said Doctor Deutsch.