Carbon Caused Global Warming in Ancient Past

A new study has shed light on the possible impact of rising carbon dioxide levels on the planets global temperatures. Looking back 40 million years into Earth’s history, scientists from Utrecht University, working with colleagues at the NIOZ Royal Netherlands Institute for Sea Research and the University of Southampton, have theorized that a massive increase in carbon resulted in an increase of 4 and 6 degrees Celsius.

“Understanding the relationship between the Earth’s climate and atmospheric carbon dioxide in the geological past can provide insight into the extent of future global warming expected to result from carbon dioxide emission caused by the activities of humans,” said Dr Steven Bohaty of the University of Southampton’s School of Ocean and Earth Science (SOES) based at the National Oceanography Centre in Southampton.

Algae as a History Book

The authors of the new study published in the latest edition of the journal Science focused their attention on the MiddleEocene Climatic Optimum (MECO), a period in Earth’s history which took place 40 million years ago during the Eocene (~56 to 34 million years ago) and one of the hottest periods of the time.

Using fossilised algae taken from the seafloor near Tasmania, Australia, using the Ocean Drilling program the researchers were able to reconstruct variations in CO2 across the MECO warming event.

Algae works as a very reliable indicator of environmental conditions of the past.

According to their findings the carbon dioxide levels during the MECO period must have at least doubled over a period of 400,000 years which resulted in a warming between 4 and 6 degrees Celsius over the same period.

The two findings – carbon and temperature – were reached using independent samples.

Temperature Levels Rise

“We found a close correspondence between carbon dioxide levels and sea surface temperature over the whole period, suggesting that increased amounts of carbon dioxide in the atmosphere played a major role in global warming during the MECO,” said Bohaty.

The researchers are certain that the process of events started with a rise in carbon dioxide and then saw a temperature increase, rather than vice versa. “The change in carbon dioxide 40 million years ago was too large to have been the result of temperature change and associated feedbacks,” said co-lead author Peter Bijl of Utrecht University. “Such a large change in carbon dioxide certainly provides a plausible explanation for the changes in Earth’s temperature.”

Source: National Oceanography Centre

Image Source: IODP

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