[Marxism] The Planet Has Seen Sudden Warming Before. It Wiped Out Almost Everything.

Louis Proyect lnp3 at panix.com
Tue Dec 11 08:45:09 MST 2018


NY Times, Dec. 11, 2018
The Planet Has Seen Sudden Warming Before. It Wiped Out Almost Everything.
By Carl Zimmer

Some 252 million years ago, Earth almost died.

In the oceans, 96 percent of all species became extinct. It’s harder to 
determine how many terrestrial species vanished, but the loss was 
comparable.

This mass extinction, at the end of the Permian Period, was the worst in 
the planet’s history, and it happened over a few thousand years at most 
— the blink of a geological eye.

On Thursday, a team of scientists offered a detailed accounting of how 
marine life was wiped out during the Permian-Triassic mass extinction. 
Global warming robbed the oceans of oxygen, they say, putting many 
species under so much stress that they died off.

And we may be repeating the process, the scientists warn. If so, then 
climate change is “solidly in the category of a catastrophic extinction 
event,” said Curtis Deutsch, an earth scientist at the University of 
Washington and co-author of the new study, published in the journal Science.

Researchers have long known the general outlines of Permian-Triassic 
cataclysm. Just before the extinctions, volcanoes in what is now Siberia 
erupted on a tremendous scale. The magma and lava that they belched 
forth produced huge amounts of carbon dioxide.

Once in the atmosphere, the gas trapped heat. Researchers estimate that 
the surface of the ocean warmed by about 18 degrees Fahrenheit. Some 
researchers argue that the heat alone killed off many species.

Others believe that the warmth reduced oxygen in the ocean, asphyxiating 
the species living there. Rocks from the mass extinction appear to have 
formed when at least some of the ocean was lacking oxygen.

In previous research, Dr. Deutsch has explored how living animals adapt 
to temperature and oxygen levels in the seas. Animals with a fast 
metabolism need a lot of oxygen, for example, and so they can’t live in 
parts of the ocean where oxygen falls below a certain threshold.

Warm water makes the challenge even more difficult. Warmer water can’t 
hold as much dissolved oxygen as cold water. Even worse, warm water can 
also increase an animal’s metabolism, meaning it requires more oxygen 
just to stay alive.

Cod, for example, are not found below a latitude running roughly from 
New England to Spain. South of that line, warmth and low oxygen are just 
too great for the species.

Dr. Deutsch and Justin Penn, a graduate student, recreated the world at 
the end of the Permian Period with a large-scale computer simulation, 
complete with a heat-trapping atmosphere and a circulating ocean.

As the Siberian volcanoes flooded the virtual atmosphere with carbon 
dioxide, the atmosphere warmed. The ocean warmed, too — and according to 
the model, it began losing oxygen.

Some parts lost more than others. On the surface, for example, fresh 
oxygen was produced by photosynthetic algae. But as the ocean warmed, 
its circulatory currents also slowed, the model demonstrated.

Oxygen-poor water settled to the bottom of the oceans, and before long, 
the deep was gasping.

Rising temperatures and plunging oxygen must have made huge swaths of 
the oceans uninhabitable. Some species survived here and there. But most 
disappeared completely.

“Everything was losing a lot of habitat, creating the risk of 
extinction,” said Dr. Deutsch. “But the risk was actually higher in 
places that were cold. That was a bit surprising.”

You might expect that animals near the Equator would be at a greater 
risk, because the water was warm to begin with. But Dr. Deutsch’s model 
suggested a very different kind of apocalypse.

Animals in oxygen-rich cold water could not handle the sudden drop, 
while those in tropical waters were already adapted to poor oxygen. And 
the cold-water species could not find refuge elsewhere.

To test their simulation, the researchers teamed up with Jonathan Payne 
and Erik Sperling, paleontologists at Stanford University. They dug into 
a huge online database of fossils to chart the risks of extinction at 
different latitudes during the catastrophe.

When they were done with their analysis, they sent their graph to 
Seattle. Dr. Deutsch and Mr. Penn compared it to the prediction from 
their computer model.

They matched. “This was the most exciting moment of my scientific life,” 
said Dr. Deutsch.

Michael Benton, a paleontologist at the University of Bristol in 
England, who was not involved in the study, said that it resolved the 
roles of heat and oxygen as causes of the mass extinction. “This makes a 
clear case that, of course, the two are linked,” he said.

The new study offers an important warning to humans over the next few 
centuries.

The Siberian volcanoes ultimately delivered much more carbon dioxide 
into the atmosphere than we will ever emit by burning fossil fuels. But 
our annual rate of carbon emissions is actually higher.

The carbon we released over the past two centuries already has made the 
atmosphere warmer, and the ocean has absorbed much of that heat. And 
now, just as during the Permian-Triassic extinction, the ocean is losing 
oxygen. Over the past fifty years, oxygen levels have declined by 2 percent.

“The way the Earth system is responding now to the buildup of CO2 is in 
the exact same way that we’ve seen it respond in the past,” said Lee 
Kump, a geoscientist at Penn State University.

Just how much warmer the planet will get is up to us. It will take a 
tremendous international effort to keep the increase below about 4 
degrees Fahrenheit.

If we proceed to use up all the fossil fuels on Earth, it could warm by 
as much as 17 degrees Fahrenheit by 2300.

As the ocean warms, its oxygen levels will continue to drop. If ancient 
history is any guide, the consequences for life — especially marine life 
in the cooler parts of the ocean — will be disastrous.

“Left unchecked, climate warming is putting our future on the same scale 
as some of the worst events in geological history,” Dr. Deutsch said.



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