New research from the University of Gothenburg, published in August 2025, reveals that thawing permafrost following the last Ice Age was a primary driver of rising atmospheric carbon dioxide. Scientists estimate this terrestrial carbon release accounted for nearly half of the CO2 increase as the planet transitioned from a glacial to an interglacial climate.
Why did atmospheric carbon dioxide rise after the last Ice Age?
For decades, the scientific consensus pointed toward the world’s oceans as the main regulator of carbon dioxide levels. According to University of Gothenburg researchers, while warmer oceans do release stored carbon, land-based emissions from thawing permafrost played an equally critical role. The study indicates that as the Northern Hemisphere warmed, frozen ground north of the Tropic of Cancer (23.5 degrees north) released massive quantities of trapped organic matter.
During the last Ice Age, roughly 21,000 years ago, atmospheric carbon dioxide levels were approximately 180 parts per million. By 11,000 years ago, those levels had climbed to 270 parts per million, a rise now linked significantly to northern permafrost thaw.
How did ancient landscapes store so much carbon?
Carbon was trapped during the Ice Age due to the accumulation of “loess”—wind-borne rock dust that settled over frozen plants and grasses. As Amelie Lindgren, a researcher in ecosystem science at the University of Gothenburg, explains, cold temperatures prevented microbes from decomposing organic matter. This created a massive, frozen reservoir across parts of Europe, Asia, and North America. Over thousands of years, these layers of loess and organic material grew tens of meters thick, locking away carbon that would not be released until the climate began to warm.
What happened when the permafrost began to thaw?
Between 17,000 and 11,000 years ago, significant warming triggered the decomposition of this long-preserved organic matter. The research team estimates that northern land areas released more than 300 petagrams of carbon—equivalent to 300 billion metric tons—into the atmosphere. This release actively amplified the rise in greenhouse gas concentrations. However, the system eventually found a new balance as peatlands expanded during the Holocene epoch, which began about 12,000 years ago. These peatlands acted as a natural sink, absorbing carbon and compensating for the earlier permafrost emissions.
Are there lessons for modern climate change?
The current climate trajectory differs from the post-Ice Age period in one critical way: geography. After the last Ice Age, retreating ice sheets left behind new land areas where carbon-sequestering ecosystems like peatlands could thrive. Today, human-driven warming is occurring at a much faster pace, and rising sea levels are shrinking the available land. According to Lindgren, it is difficult to identify where the carbon released from modern permafrost thaw could be stored, as the current landscape offers fewer opportunities for new carbon sinks to develop compared to the post-glacial era.
Frequently Asked Questions
What is loess?
Loess is a deposit created by wind-borne rock dust that accumulated during glacial periods, often preserving organic material beneath frozen ground.
How much carbon was released after the last Ice Age?
Researchers estimate that northern land areas released over 300 billion metric tons of carbon as the climate warmed between 17,000 and 11,000 years ago.
Why are peatlands important?
Peatlands are highly effective at storing carbon. During the Holocene, their expansion helped stabilize atmospheric carbon dioxide levels by offsetting the carbon released from thawing permafrost.
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