Global warming already existed ... and ended almost all life |
Posted: March 21, 2019 |
252 million years ago, it was not long before the Earth died . In the oceans, 96 percent of all species were extinct. It is more difficult to determine how many terrestrial species disappeared, but the loss was similar. This massive extinction at the end of the Permian was the worst in the history of this planet and happened, at best, over a few thousand years, in the blink of an eye in geological terms. On December 6, a group of scientists provided a detailed account of the way marine life was eliminated during the massive Permian-Triassic extinction . Scientists say that global warming took oxygen away from the oceans and put many species under so much pressure that they began to die. In addition, scientists warn that maybe we are repeating the process. If so, then climate change is "firmly in the category of catastrophic extinction events," said Curtis Deutsch, a scientist specializing in Earth Sciences at the University of Washington and co-author of this new study, published in the journal Science Researchers have known for a long time the general events of the Permian-Triassic cataclysm. Just before extinctions, the volcanoes of what is now Siberia erupted on a large scale. The magma and lava they threw produced huge amounts of carbon dioxide. Since it was in the atmosphere, the gas retained heat. The researchers calculate that the surface of the ocean warmed up to at least 8 degrees Celsius. Some researchers argue that heat alone killed off many species. Others believe that the warming reduced the ocean's oxygen and suffocated the species that lived there. Apparently rocks were formed during the mass extinction when oxygen was missing at least part of the ocean. In previous research, Deutsch has analyzed the way in which living animals adapt to sea temperature and oxygen levels. For example, animals that have a fast metabolism need a lot of oxygen, so they can not live in parts of the ocean where oxygen falls below a certain limit. Warm water makes this challenge even more difficult. When the water is warmer, it can not hold as much dissolved oxygen as cold water. And even worse: warm water can also increase the metabolism of animals, which means they need more oxygen to stay alive. For example, cod is not below a latitude that goes more or less from New England to Spain. To the south of that line, the heat and the low level of oxygen generate too much pressure for that species. Deutsch and Justin Penn, a graduate student, made a re-creation of the world at the end of the Permian with a large-scale computer simulation, which they completed with an atmosphere that retains heat and an ocean that flows. When the volcanoes of Siberia filled the virtual atmosphere with carbon dioxide, the atmosphere warmed up. The ocean also warmed up and, according to the model, began to lose oxygen. Some parts lost more oxygen than others. For example, on the surface, photosynthetic algae produced fresh oxygen. This model showed that as the ocean warmed up, its circulation currents were also slower. The water that had little oxygen went to the bottom of the oceans and, shortly after, the depths were suffocated. Surely the increase of the temperatures and the descent of the oxygen made uninhabitable enormous fringes of the oceans. Some species survived here and there, but most disappeared completely. "Everyone was losing a large part of their habitat, which generated the risk of extinction," Deutsch said. "But the risk was actually greater in the cold places; that was a bit surprising. " One could expect that animals near the equator were at higher risk because the water was warm from the start. However, Deutsch's model proposed a very different type of apocalypse. Animals that lived in cold water with lots of oxygen could not withstand the sudden drop in oxygen, while those living in tropical waters were already adapted to little oxygen. And cold water species found no refuge anywhere else. To test their simulation, the researchers collaborated with Jonathan Payne and Erik Sperling, paleontologists at Stanford University. They reviewed a huge fossil database on the internet to graph the extinction risks in different latitudes during the catastrophe. When they finished their analysis, they sent their chart to Seattle. Deutsch and Penn compared it to the prediction of their computer model.
Michael Benton, a paleontologist at the University of Bristol, England, who was not involved in the study, said this clarified the role of heat and oxygen as causes of mass extinction. "This is a clear example that obviously have a relationship," he said. The new study poses an important warning for humans in the centuries to come. In the long run, Siberian volcanoes released much more carbon dioxide into the atmosphere than we will ever emit when burning fossil fuels. However, our annual carbon emission rate is, in fact, higher. The carbon we have emitted during the last two centuries has already warmed the atmosphere, and the ocean has absorbed much of that heat. In addition, now, as during the Permian-Triassic extinction, the ocean is losing oxygen. During the last fifty years, oxygen levels have decreased by two percent . "The way in which the Earth system is now responding to the accumulation of CO2 is exactly the same as we have seen before," said Lee Kump, a geoscientist at Pennsylvania State University. It depends on us how much more the planet will heat up. It will take a huge international effort for this increase to remain below minus 15 degrees Celsius, approximately. If we continue to use all fossil fuels on Earth, it could heat up to 8 degrees Celsius by the year 2300 . As the ocean warms, your oxygen levels will continue to drop. If history can teach us something ancient, it is that the consequences for life - especially marine life in the coldest parts of the ocean - will be disastrous. "If we do not control it, global warming will put our future in the same dimension as some of the worst events in geological history," Deutsch said.
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