2025-09-01T14:38:07Z

Imagine a world where the air we breathe has a history that spans millions of years. It turns out, the carbon dioxide we’re so familiar with isn’t just a byproduct of modern industry; it’s been fluctuating due to natural cycles for eons. But a groundbreaking new study from the University of Gothenburg reveals that the impacts of climate change may be far deeper—and more alarming—than we’ve ever realized.

This study uncovers a startling twist: rather than oceans being solely responsible for the rise in carbon dioxide after the last ice age, thawing permafrost played a monumental role. Yes, you heard that right! The very soil beneath our feet, once locked away in ice, is now significantly contributing to the gas that’s warming our planet.

Ancient Climate Patterns Unveiled

For centuries, scientists believed that carbon dioxide changes were primarily due to the oceans. As Earth entered its warm interglacial periods, CO2 levels surged by nearly 100 parts per million, a process attributed to warmer seas losing their carbon stores. But this new research indicates that the lands north of the Tropic of Cancer—an area rich with permafrost—were also major contributors when the northern hemisphere began warming.

Study lead author Amelie Lindgren spells it out: “We have concluded that land north of the Tropic of Cancer emitted a lot of carbon when the average temperature rose in the northern hemisphere after our last ice age. We estimate that this carbon exchange may have accounted for almost half of the rising carbon dioxide levels in the atmosphere.” This revelation is not just significant; it’s a game changer.

Permafrost: The Climate’s Hidden Reservoir

Imagine vast landscapes that once served as natural vaults of carbon, with grasses and plants preserved in ice for thousands of years. The thick layers of windblown dust known as loess, which spread across Europe, Asia, and North America, entrapped this organic matter, slowing its decomposition and allowing it to store carbon far beyond the capacity of typical unfrozen soils.

The researchers combined 21,000 years of pollen records with climate model data to reconstruct vegetation patterns and estimate carbon storage over time. Lindgren explains, “We have chosen to take a snapshot every thousand years. Once we know what type of vegetation prevailed, we can estimate how much carbon was stored in the soil.” This meticulous work shows how the balance of carbon between the atmosphere and soil has shifted since the last Ice Age.

The Impact of Thawing Permafrost

As the ice sheets retreated between 17,000 and 11,000 years ago, northern soils began to thaw, releasing significant amounts of carbon dioxide into the atmosphere and dramatically altering Earth’s climate balance. The figures are staggering: loess deposits stored around 363 petagrams of carbon at the peak of the last glaciation, but today, only about 57 petagrams remain.

Most of this loss occurred over 10,000 years ago, representing one of the largest carbon shifts in history. While peatlands emerged as effective carbon sinks, absorbing about 450 petagrams of carbon during the Holocene, they cannot entirely offset the emissions from thawing permafrost.

A Shift in Perspective

The retreat of massive ice sheets not only reshaped landscapes but also created new opportunities for vegetation to flourish, establishing fresh carbon stores. However, as rising seas swallowed vast continental shelves, the story of carbon cycling became increasingly complex. The study suggests that while some carbon resurfaced into the atmosphere, much of it may have been buried under marine sediments.

Ice cores tell a sobering tale: CO2 levels stood at a mere 180 ppm about 21,000 years ago, but by 11,000 years ago, they had jumped to 270 ppm. Although peatlands did their part by absorbing significant carbon, this natural balance is now disrupted.

The Human Factor

Over the past 250 years, humanity has drastically altered this natural cycle, with the combustion of fossil fuels pushing atmospheric carbon levels from 280 ppm to a staggering 420 ppm today. “There are extremely high levels of carbon dioxide in the atmosphere right now, and the permafrost is thawing as temperatures rise. What helped us the last time was increased carbon storage in peatlands,” explains Lindgren. But with rising sea levels threatening to reduce land space, the future looks uncertain.

Lessons for Tomorrow

This study is a wake-up call, highlighting how delicate Earth’s carbon balance really is. While natural systems once offset permafrost losses, today’s climate crisis presents unprecedented challenges. The carbon locked in frozen soils could reshape our climate yet again, but this time, it’s against a backdrop of human-induced warming.

As we grapple with these revelations, one thing is clear: understanding our past is crucial, but it’s our actions today that will determine the future of our planet.

The study is published in the journal Science Advances.