The Earth could be in 140 years to reach unmatched carbon levels since 56 million years – ScienceDaily

New study finds that humans release 10 to 10 times more carbon dioxide into the atmosphere than greenhouse gas emissions from the Paleocene-Eocene Thermal Maximum (PETM), an event that took place about 56 million years ago.

The results suggest that if carbon emissions continue to increase, the total amount of carbon dioxide injected into the atmosphere since humans began burning fossil fuels could be equal to the amount released during PETM from 2159.

"You and I will not be here in 2159, but there are only four generations left," said Philip Gingerich, paleoclimate researcher at the University of Michigan and author of the new study in the AGU journal Paleoceanography and Paleoclimatology. "When you start thinking about your children and your grandchildren and your great-grandchildren, you're about to do it."

Scientists often use PETM as a reference for comparing modern climate change. But the new study shows that we are on track to reach this benchmark much sooner than expected, as the pace of current warming far exceeds any climatic event since the dinosaurs' extinction.

"Given the assumption that the future will remain unchanged, current carbon emission rates are unprecedented, even in the context of an event like the PETM," said Gabriel. Bowen, geophysicist at the University of Utah. was not connected to the new study. "We do not have many geological examples from which we can understand how the world reacts to this type of disturbance."

According to Larisa DeSantis, a paleontologist at Vanderbilt University who was not related to the phenomenon, the environmental consequences of PETM-type carbon levels are unclear, but higher temperatures will likely lead to the extinction of many species. the new study. In addition, the cooling of the climate system will take thousands of years, she said.

"It's not in about 100 years, it will take a long time for carbon dioxide to reappear in the earth's crust," DeSantis said. "This is not a short – term event – we are really engaging in thousands of years of a warmer world if we do not act quickly.

Study past climate change

The PETM was a global warming event that occurred about 56 million years ago. Scientists do not know what caused it, but during the event, huge amounts of carbon dioxide were released into the Earth's atmosphere, rapidly increasing temperatures by 5 to 8 degrees Celsius ( 9 to 14 degrees Fahrenheit). Average global temperatures during PETM peaked at about 23 degrees Celsius (73 degrees Fahrenheit), about 7 degrees Celsius (13 degrees Fahrenheit) above the current average.

Scientists believe that during this period and the warm period that followed, the poles were ice-free and that the Arctic was home to palms and crocodiles. It's not the hottest Earth ever, but the PETM has been the hottest time since the extinction of the dinosaurs 66 million years ago.

Scientists do not know exactly how much carbon was injected into the atmosphere during PETM nor how long the event lasted. But their best estimates are between 3,000 and 7,000 gigatonnes of carbon accumulated over a period of 3,000 to 20,000 years, based on oceanic sediment cores showing changes in carbonate minerals during this period.

The massive carbon emission and temperature increase have drastically altered the Earth's climate, causing a major extinction of deep ocean organisms that constitute a vital link in the marine food web. Terrestrial animals became smaller and migrated northward in colder climates. Some groups of modern mammals, including primates, appeared for the first time shortly after the PETM, but scientists do not know if this is directly attributable to the rapid change in the environment.

Compare the past to the present

Climatologists use PETM as a case study to understand what environmental changes might occur in the current climate of man-made climate change and when these changes could take effect. But they can only average carbon emissions during the PETM over the entire duration of the event – thousands of years. They do not know what these emission rates look like on an annual basis. It is therefore difficult to compare them with the current rate of carbon emissions.

In the new study, Gingerich found a way to mathematically compare modern carbon emissions with PETM emissions on the same time scale. The results showed that current carbon emission rates are nine to 10 times higher than those of PETM.

"For me, this has really shown how fast the carbon impacts we produce as a people are," said Gingerich.

By projecting current emissions into the future, Gingerich discovered that if emissions continue to increase, we may be faced with another event similar to PETM in less than five generations. The total carbon accumulated in the atmosphere could reach the lowest estimate of the carbon accumulated during the PETM – 3,000 gigatons – by 2159. It would reach the estimated maximum emissions – 7,126 gigatons – in 2278, from After Gingerich's calculations. Humans emitted around 1,500 gigatonnes of carbon in 2016.

"The fact that we can achieve GMT-equivalent warming very quickly in the next hundred years is terrifying," DeSantis said.

The results suggest that scientists may not be able to predict the environmental or biological changes that will occur in the coming years based on what has happened during PETM, as the current warming is occurring much more quickly, according to DeSantis. What makes the predictions more difficult is that the current climate starts with a colder baseline than the PETM and that the species that populate the Earth are different from those of 56 million years ago. # 39; years.

"It's hard to compare biotic effects because the world was very different from PETM," DeSantis said. "We live in a very different world today, with different groups of animals, humans being the dominant species … but we know that dramatic warming has many negative consequences on a large number of species, including ours. "