Environmental Science
Permafrost Thaw and Its Feedback on Global Warming
Quick fact
Permafrost holds about 1,500 billion metric tons of carbon—roughly twice the amount currently in the atmosphere.
Why this is interesting
Imagine a giant freezer storing organic carbon for thousands of years. Now imagine that the freezer door is slowly opening—and what comes out could turbocharge global warming.
Read the full explanation
Understanding Permafrost Thaw and Its Feedback on Global Warming
Permafrost is ground that has remained frozen for at least two consecutive years, often for millennia. It underlies about 15% of the Northern Hemisphere's land. As global temperatures rise, this frozen ground thaws. Buried within it is dead plant and animal matter, locked away by the cold. Once thawed, microbes begin breaking down this organic material, releasing carbon dioxide (CO₂) in dry conditions and methane (CH₄) in wet, oxygen-poor conditions. Both are potent greenhouse gases. They trap heat, causing further warming, which thaws more permafrost—a classic positive feedback loop. This cycle means that warming triggered by human emissions can be amplified by natural processes, potentially accelerating climate change beyond our ability to control it.
A deeper explanation
The feedback mechanism works because microbial decomposition is temperature-dependent: as permafrost warms, microbial activity increases exponentially, releasing more gases. Methane is especially significant—it is about 25 times more effective at trapping heat than CO₂ over 100 years, and even more powerful over shorter timescales. A particular worry is the release of methane from subsea permafrost and frozen methane hydrates, which could trigger abrupt, large-scale emissions. The permafrost feedback is one of several climate 'tipping elements'—once a threshold is crossed, it may continue even if human emissions stop. Understanding this feedback is crucial because it shifts the carbon budget: we must reduce emissions more rapidly to account for the additional natural release. Studies estimate that by 2100, permafrost thaw could add 50–250 billion tons of CO₂ equivalent to the atmosphere, significantly increasing the challenge of meeting climate targets.