Permafrost regions covering 20 million square kilometers across Russian Siberia, Canada, Alaska and parts of Europe store approximately 1,500 gigatons of carbon—three times the amount held in all living vegetation on Earth. As global temperatures rise from fossil fuel emissions, this permanently frozen ground begins to thaw, exposing ancient plant remains to microbial decomposition that releases carbon dioxide and methane into the atmosphere, creating a self-reinforcing warming cycle.
The thawing process creates irreversible landscape changes that prevent refreezing on human timescales. When subsurface ice melts, water drainage causes surface collapse, forming thermokarsts—new landforms including lakes, wetlands, and river gullies that alter soil thermal properties and hydrology. Once these threshold changes occur, affected areas will continue emitting carbon for decades or centuries, according to Gustaf Hugelius, a climate professor at Stockholm University’s Bolin Centre.
While a complete global permafrost system collapse is unlikely unless warming reaches 6 degrees Celsius, multiple local tipping points are already occurring in succession. Some regions have passed irreversible thresholds, and projections indicate between 200 and 300 gigatons of carbon dioxide equivalents could be released if global temperatures rise 1.8 to 3.6 degrees by century’s end—exceeding the current emissions of the European Union.
The type of greenhouse gas released depends on whether thawed areas become dry or wet environments. Dry landscapes produce carbon dioxide through microbial oxidation, while oxygen-depleted wetlands and lakes generate methane, which is approximately 30 times more potent though shorter-lived. A significant research challenge involves determining which thawing permafrost regions will become wetter or drier. Some permafrost areas, particularly along the southern fringes in northern Sweden and Finland, are already committed to disappearance due to warming thresholds exceeded over the past decade, while larger Siberian and Canadian regions could remain largely intact with successful climate action.
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