Study identifies 10 fold faster rise in rate of CO2 emission seen during Ice Age

The faster rates could outweigh the rates at which the Southern Ocean can absorb human-released CO2, the study found.

New Delhi: Carbon dioxide (CO2) is being released in the air at rates up to 10 times faster than at any other point in the past 50,000 years, including the Ice Age, according to new research.

These rates could outweigh the rates at which the Southern Ocean can absorb human-released CO2, the study found. The Southern Ocean is a known carbon sink, studied to absorb significant amounts of carbon from the atmosphere every year.

Analysing ice samples from Antarctica, researchers found that the largest increase in CO2 levels occurring naturally was by about 14 parts per million, spread over a duration of 55 years.

The increase was found to have happened during the Heinrich Stadial-4, the fourth of five cold intervals, known as Heinrich Events, associated with abrupt climate shifts around the world. The cold intervals were observed during the Ice Age, a colloquial term referring to the Last Glacial Period spanning 1,15,000 years ago to 11,700 years ago.

In this study, led by Oregon State University, US, the researchers found that while such large jumps in CO2 levels used to occur about once every 7,000 years, such jumps take only 5-6 years at the current rates of CO2 being released, primarily coming from human emissions.

"Studying the past teaches us how today is different. The rate of CO2 change today really is unprecedented," said Kathleen Wendt, an assistant professor in Oregon State University's College of Earth, Ocean, and Atmospheric Sciences.

"Our research identified the fastest rates of past natural CO2 rise ever observed, and the rate occurring today, largely driven by human emissions, is 10 times higher," said Wendt, lead author of the study published in the journal Proceedings of the National Academy of Sciences.

While previous studies have shown several periods during the Ice Age when CO2 levels jumped much higher than the average ones, the researchers said those measurements were not detailed enough to reveal the "full nature of the rapid changes,' thereby limiting scientists" understanding of what was happening.

In this study, the team investigated what was happening in those periods using samples from the West Antarctic Ice Sheet Divide ice core.

They discerned patterns showing that CO2 levels spiked alongside North Atlantic cold intervals, or Heinrich Events.

"These Heinrich Events are truly remarkable," said co-author Christo Buizert, an associate professor in the College of Earth, Ocean, and Atmospheric Sciences.

"We think they are caused by a dramatic collapse of the North American ice sheet. This sets into motion a chain reaction that involves changes to the tropical monsoons, the Southern hemisphere westerly winds and these large burps of CO2 coming out of the oceans," explained Buizert.

There is evidence suggesting that these westerly winds, known to be important to circulation of the deep ocean, were also strengthening, thereby leading to a rapid release of CO2 from the Southern Ocean, according to the researchers.

These westerlies have been predicted to strengthen over the next century, because of climate change, they said.

Should this happen, the latest findings suggested that the Southern Ocean's capacity to absorb human-generated carbon dioxide will be reduced.

"We rely on the Southern Ocean to take up part of the carbon dioxide we emit, but rapidly increasing southerly winds weaken its ability to do so," said Wendt.