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One study warned that global temperatures by the end of the century will reach levels not seen in 50 million years if greenhouse gas emissions are not significantly reduced.
German and American experts analyzed small fossils in samples taken from the bottom of the sea to reconstruct the climatic history of the Earth until the time of the dinosaurs.
During this 66 million year period, the planet has witnessed four different climatic states, which scientists have called “greenhouse”, “warm habitat”, “refrigerant” and “ice habitat”.
For most of the last three million years, the Earth has been in an “icy” state characterized by alternations between ice ages and ice periods.
However, experts warn that greenhouse gas emissions and other human activities are pushing the climate towards a “greenhouse effect.”
Warm habitat conditions were last seen during the Eocene, which ended about 34 million years ago, when there were no ice caps.
During this time, global mean temperatures were 16.2-25.2 degrees Fahrenheit (9-14 degrees Celsius), higher than today.
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The article’s author, James Zakus, said that the IPCC forecast for 2300 in the “business as usual” scenario [الانبعاثات]She says global temperature is likely to rise to a level not seen on the planet in 50 million years.
In their study, Professor Zakos and his colleagues created a “climate reference curve” called CENOGRID, which maps past and present global temperature changes, and includes different forecasts for the future based on emission levels. .
CENOGRID revealed that natural climate variability, which occurs as a result of changes in the Earth’s orbit around the sun, is much less than the expected future warming due to greenhouse gas emissions.
Marine geologist Thomas Westerhold said: “We now know more precisely when the atmosphere is warmer or colder, and we have a better understanding of the basic dynamics and the processes that drive it.”
He added: “The time from 66 to 34 million years, when the planet was significantly warmer than it is today, is of particular importance, because in the past it represents what human change could lead to in the future.”
Professor Zakos, who is conducting research at the University of California, Santa Cruz, said: “We have known for a long time that interglacial cycles keep pace with changes in Earth’s orbit.” These cycles change the amount of solar energy that reaches the Earth’s surface, and astronomers have been calculating these orbital changes over time, he said. And when we rebuild past climates, we can see extreme long-term changes well. We also knew that there had to be a variation. Rhythmic accuracy due to orbital changes, but for a long time it was impossible to recover that signal. Now that we have managed to recognize natural climate variability, we can see that the expected anthropogenic warming will be much greater than that. “
Most of the major climate changes of the last 66 million years, when dinosaurs were killed by a giant asteroid, have been linked to changes in greenhouse gas levels.
Previous research by Professor Zakos found that the period of rapid global warming about 50 million years ago, which pushed the climate into a greenhouse, was the result of a massive release of carbon into the atmosphere.
Also, in the late Eocene period, as levels of carbon dioxide in the atmosphere decreased, ice sheets began to form in Antarctica and the climate changed to a cooling state.
“The weather can become unstable as it approaches one of these changes, and we see less predictable responses to orbital forcing, so we would like to understand it better,” Zakos added.
The full results of the study are published in the journal Sciences.
Source: Daily Mail
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