The fastest rate of natural CO2 rise over the last 50,000 years

A detailed chemical analysis of ancient Antarctic ice.

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CO2 occurs naturally in the atmosphere. When carbon dioxide enters the atmosphere, the greenhouse effect causes the climate to warm. Although ice age cycles and other natural factors have caused fluctuations in the levels in the past, human emissions are currently increasing.

Previous studies revealed multiple times in the last ice age, which ended around 10,000 years ago when carbon dioxide levels seemed to spike significantly higher than average. However, the lack of specificity in those measurements prevented scientists from fully understanding the nature of the swift alterations.

Through a thorough chemical examination of ancient Antarctic ice, researchers have discovered that the pace at which atmospheric carbon dioxide is increasing today is ten times faster than it has been at any other time in the past 50,000 years.

The study offers significant clues on abrupt climate change periods in Earth’s past and provides new insight into the potential impacts of climate change today.

slice from an Antarctic ice core
A slice from an Antarctic ice core. Researchers study the chemicals trapped in old ice to learn about past climate. Photo by Katie Stelling, Oregon State University. Photo by Katherine Stelling, Oregon State University.

Kathleen Wendt, an assistant professor at Oregon State University‘s College of Earth, Ocean, and Atmospheric Sciences and the study’s lead author, said, “Studying the past teaches us how today is different. The rate of CO2 change today is unprecedented. Our research identified the fastest rates of past natural CO2 rise ever observed, and the rate occurring today, primarily driven by human emissions, is ten times higher.

“You probably wouldn’t expect to see that in the dead of the last ice age. But our interest was piqued, and we wanted to go back to those periods and conduct measurements in greater detail to find out what was happening.”

Scientists used the West Antarctic Ice Sheet Divide ice core samples to investigate what occurred during those periods. They discovered a trend that indicated these spikes in carbon dioxide coincided with cold spells in the North Atlantic known as Heinrich Events, which are linked to sudden changes in the global climate.

Christo Buizert, an associate professor at the College of Earth, Ocean, and Atmospheric Sciences and co-author of the study, said, “These Heinrich Events are truly remarkable. We think a dramatic collapse of the North American ice sheet caused them. 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.”

Carbon dioxide rose by roughly 14 parts per million during the greatest natural rises in 55 years. Furthermore, the jumps happened around once every 7,000 years. At the current rates, it just takes 5 to 6 years to achieve that kind of improvement.

Evidence shows that westerly winds, crucial to the deep ocean’s circulation, intensified during previous periods of natural carbon dioxide growth. This resulted in a quick release of CO2 from the Southern Ocean. According to some studies, the effects of climate change may cause these westerlies to get stronger over the next century. According to the researchers’ latest research, if that happens, the Southern Ocean’s ability to absorb carbon dioxide produced by humans may be diminished.

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

Journal Reference:

  1. Kathleen A. Wendt, Christoph Nehrbass-Ahles, Kyle Niezgoda and Christo Buizert. Southern Ocean drives multidecadal atmospheric CO2 rise during Heinrich Stadials. PNAS. DOI: 10.1073/pnas.2319652121

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