Human carbon release rate is unprecedented in the past 66 million years of Earth's history

https://www.sciencedaily.com/releases/2016/03/160321123656.htm

Date:March 21, 2016

Source:University of Hawaii at Manoa

Summary:
Researchers look at changes of Earth's temperature and atmospheric carbon dioxide (CO2) since the end of the age of the dinosaurs. Their findings suggest humans are releasing carbon about 10 times faster than during any event in the past 66 million years.

•••••

New research published today in Nature Geoscience by Richard Zeebe, professor at the University of Hawai'i -- Mānoa School of Ocean and Earth Science and Technology (SOEST), and colleagues looks at changes of Earth's temperature and atmospheric carbon dioxide (CO2) since the end of the age of the dinosaurs. Their findings suggest humans are releasing carbon about 10 times faster than during any event in the past 66 million years.

The research team developed a new approach and was able to determine the duration of the onset of an important past climate event, the Paleocene-Eocene Thermal Maximum, PETM for short, 56 million years ago.

"As far as we know, the PETM has the largest carbon release during the past 66 million years," said Zeebe.

•••••

The rate of carbon release during the PETM was determined to be much smaller than the current input of carbon to the atmosphere from human activities. Carbon release rates from human sources reached a record high in 2014 of about 37 billion metric tons of CO2. The researchers estimated the maximum sustained carbon release rate during the PETM had to be less than 4 billion metric tons of CO2 per year -- about one-tenth the current rate.

"Because our carbon release rate is unprecedented over such a long time period in Earth's history, it also means that we have effectively entered a 'no-analogue' state. This represents a big challenge for projecting future climate changes because we have no good comparison from the past," said Zeebe.

•••••

"If you kick a system very fast, it usually responds differently than if you nudge it slowly but steadily," said Zeebe. "Also, it is rather likely that future disruptions of ecosystems will exceed the relatively limited extinctions observed at the PETM," Zeebe added.

•••••