Researchers at Oregon State University have determined that today's atmospheric carbon dioxide increase is occurring 10 times faster than at any point in the last 50,000 years. This finding comes from a detailed chemical analysis of ancient Antarctic ice and has been published in the Proceedings of the National Academy of Sciences.
The study offers new insights into abrupt climate change periods in Earth's history and highlights the potential impacts of current climate change. Kathleen Wendt, an assistant professor in Oregon State University's College of Earth, Ocean, and Atmospheric Sciences and the study's lead author, stated, "Studying the past teaches us how today is different. The rate of CO2 change today really is unprecedented."
The research identified the fastest rates of past natural CO2 rise, with the current rate driven largely by human emissions being 10 times higher. Carbon dioxide is a greenhouse gas that occurs naturally in the atmosphere and contributes to climate warming through the greenhouse effect. Historically, CO2 levels have fluctuated due to natural causes like ice age cycles, but today they are rising because of human activities.
Scientists analyze ancient atmospheric gases trapped in air bubbles within Antarctic ice, collected by drilling cores up to 2 miles (3.2 kilometers) deep. This research, supported by the U.S. National Science Foundation, used these ice samples to study past climate conditions.
Previous studies indicated several periods during the last ice age, which ended about 10,000 years ago, where CO2 levels appeared to rise sharply. However, those studies lacked the detail needed to fully understand these rapid changes, said Wendt. "You probably wouldn't expect to see that in the dead of the last ice age," she said. "But our interest was piqued, and we wanted to go back to those periods and conduct measurements at greater detail to find out what was happening."
Using samples from the West Antarctic Ice Sheet Divide ice core, the researchers found that these CO2 jumps coincided with North Atlantic cold intervals known as Heinrich Events, associated with abrupt climate shifts globally. "These Heinrich Events are truly remarkable," said Christo Buizert, an associate professor in the College of Earth, Ocean, and Atmospheric Sciences and co-author of the study. "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."
During the largest of these natural rises, CO2 increased by about 14 parts per million in 55 years. These jumps occurred approximately once every 7,000 years. Today, such an increase occurs in just 5 to 6 years.
Evidence suggests that during past periods of natural CO2 rise, strengthening westerly winds led to a rapid release of CO2 from the Southern Ocean. Other studies have suggested that these westerlies will strengthen over the next century due to climate change, which would reduce the Southern Ocean's capacity to absorb human-generated CO2.
"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," Wendt said.
Research Report:Southern Ocean drives multidecadal atmospheric CO2 rise during Heinrich Stadials
