A recent study sheds light on the historical fluctuations of carbon dioxide levels in the atmosphere, particularly emphasizing the role of thawing permafrost following the last ice age. The study paints a dramatic contrast between those ancient atmospheric conditions and our present-day concentrations. It’s evidence of how dramatically things have changed over millennia.
At the height of the last ice age, carbon dioxide levels plummeted. They fell to about 180 ppm. As the ice sheets were at their maximum extent in the Northern Hemisphere, atmospheric CO2 was at one of its lowest points. The leaked study shows just how much things have changed. By 11,000 years ago, in the middle of a normal interglacial period, CO2 concentrations rose to around 270 ppm. Removal of the atmosphere This replacement emphasizes the natural fluctuation of carbon dioxide amounts throughout cycles of ice ages and more humid periods.
The timeline of atmospheric CO2 is striking. It climbed back up from 180 ppm at the height of the last ice age. By the onset of the Industrial Revolution in the 1800s, it was up to 280 ppm. Today, it would be a miracle if the concentration was as low as 420 ppm. This trajectory underscores both natural variability and anthropogenic activity that has profoundly altered the carbon cycle.
The Role of Permafrost in Carbon Dynamics
Permafrost is key to the vast store of carbon on Earth. This allows it to function as a reservoir of organic material that’s built up over thousands of years. During ice ages, vast amounts of carbon were sequestered as plants froze into the ground, while wind-borne rock dust settled to create loess deposits. The research identifies that healthy soils enhanced with permafrost contain much greater amounts of organic carbon than soils that are unfrozen. This research highlights the importance of permafrost in protecting carbon.
As the Earth’s climate warms and more permafrost thaws, researchers are sounding alarms about what could happen next. At the same time, the thawing process itself is releasing huge amounts of carbon into the atmosphere. Amelie Lindgren, a lead researcher, states:
“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 the permafrost decreased was increased carbon storage in peatlands and new land areas becoming available when the continental ice sheets retreated. In the future, we will have less land due to sea level rise, and it is difficult to see where we will store the carbon that will be released.”
This alarmist view underscores the difficulties that lie ahead as planetary average temperatures keep rising.
Historical Carbon Emissions and Future Implications
In particular, the research explores the vast carbon impact of land located north of the Tropic of Cancer. This was the case soon after the last ice age as average temperatures across the Northern Hemisphere started to increase. Lindgren elaborates on this phenomenon:
“We have concluded that land north of the Tropic of Cancer, 23.5 degrees north, 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.”
Learning from these past historical emissions provides critical context for what to expect today and going forward.
Those results indicate peatlands were an important mechanism for carbon sequestration during the Holocene epoch. They more than balance out the emissions from thawing permafrost. Humans have thrown this balance completely out of whack by burning fossil fuels at an unprecedented scale. As a result, the natural world is shouldering more and more of the burden of CO2 absorption.
The Current Crisis and Future Challenges
From the time of the Industrial Revolution, anthropogenic activities—driven primarily by fossil fuel combustion—have greatly altered atmospheric chemistry. With fossil fuel combustion, we have increased atmospheric CO2 levels from a pre-industrial level of 280 ppm to over 420 ppm. This historic spike represents an extreme threat to global climate safety and ecosystem health.
The thawing of permafrost, accelerated by climate change, makes a bad situation worse. As organic matter imprisoned inside it breaks down and adds to greenhouse gases, it accelerates climate change from that end. These findings point to an important historical backdrop. Foremost, it underscores the key imperative to address human-caused emissions and impacts on Earth’s natural systems.