The impact of the asteroids that killed the dinosaurs also caused abrupt global warming

    Abdulaziz Sobh

    The impact of the asteroids that ended the dinosaur era also released so much carbon dioxide into the atmosphere that the planet warmed by about 5 degrees Celsius, and the spell persisted for approximately 100,000 years. That's according to a new study in the journal Science that offers a warning story about how Earth's climate will react to the carbon dioxide that is being pumped into the atmosphere now by burning fossil fuels. Scientists have long wondered about the long-term environmental effects of the notorious Chicxulub impact that occurred about 65 million years ago when a space rock more than 5 miles wide crashed into the Yucatan Peninsula. The accident must have produced an explosion of intense heat that vaporized the rock and caused massive fires. A large cloud of ash and soot must have blocked the sun for months, years or decades, giving way to a global winter that killed plants and animals (including non-avian dinosaurs) in a mass extinction. After the skies cleared, researchers believe the planet must have warmed because all those fires and zapped minerals put a lot of carbon dioxide into the atmosphere. But the evidence of these environmental effects has been difficult to discern from the geological record. "To date, there really have not been good empirical estimates about what temperature is after the impact, in terms of hundreds of thousands of years," says Page Quinton, a geologist at the State University of New York in Potsdam. She worked with Ken MacLeod, a paleontologist at the University of Missouri, Columbia, to see a possible recorder of temperatures, oxygen isotope signatures, fish fossils that lived long ago. The parts of fish remains are so small that they look like grains of sand or crud. "But under the microscope, they are unmistakably fish fossils, these are small teeth of a millimeter or a half millimeter, and under the microscope they are precious," says MacLeod, adding that they also find tiny fish scales or pieces of bone. The researchers searched carefully for pounds of rock from El Kef, Tunisia, a site that is famous for having well-preserved layers of rock that span time periods both before and after the impact of the asteroid. Julio Sepulveda, a geologist at the University of Colorado, Boulder, worked with M.H. Black from the University of Tunis to collect samples from a deep ditch dug into a hillside. "Basically, we should carefully observe each layer until we find a very characteristic layer of red color, it has a thickness of one centimeter maximum", says Sepúlveda. "That contains all the material that comes from the impact itself, the body that impacted our planet, it is a reddish color, due to the metals that are present." He says his team recovered a rock from several feet below this layer and a couple of feet above it. By analyzing fossil fish inside, the researchers determined that global temperatures remained stable for a long time before the impact of the asteroid, but then, afterwards, temperatures increased rapidly and remained around 5 degrees warmer for about 100,000 degrees Celsius. years. MacLeod says it's remarkable that the impact inflated carbon dioxide in a short period of time that, from a geological point of view, is comparable to what humans have been doing in burning fossil fuels since the beginning of the Revolution Industrial. "The atmosphere was charged for a brief period of time, and the consequences of that change in atmospheric composition lasted 100,000 years," says MacLeod. "So it illustrates, I think, very strongly, even if we went back to the carbon dioxide emission levels of 1850, it will take 100,000 years for the carbon dioxide that we have already put in the atmosphere to circulate through the systems of the Earth". " Brian Huber, a paleobiologist at the Smithsonian's National Museum of Natural History who was not part of the research team, says that this document is a real breakthrough in understanding the temperature changes at the time of this mass extinction event. And he accepts that the results have implications for thinking about the future. "I think the surprising result of this is that this warming of the temperature after the impact persisted for 100,000 years," says Huber. "It is, for me, impressive and a little scary about the course of what happens with the burning of so much coal, so much oil, in just a few decades."

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