Permafrost, ground frozen year-round across 20 million square kilometers primarily in Russian Siberia, Canada, Alaska and parts of Europe, contains approximately 1,500 gigatons of carbon—three times the amount stored in all living vegetation globally. This vast carbon reserve represents a major climate concern, as even modest changes to permafrost systems can trigger substantial atmospheric impacts.
As human activities warm the climate through greenhouse gas emissions, permafrost begins to thaw, exposing ancient plant remains to microbial decomposition. This process releases carbon dioxide and methane into the atmosphere, which intensifies warming in a self-reinforcing cycle. The thawing process fundamentally alters the landscape through the melting of subsurface ice, creating thermokarsts—new formations such as lakes, wetlands, and gullies with different hydrological and thermal properties. Once permafrost crosses this threshold, the transformed landscape will continue emitting carbon for decades or centuries on human timescales, making reversal impossible for hundreds of years.
While a complete global permafrost system collapse is unlikely unless warming reaches 6 degrees Celsius, numerous localized tipping points have already occurred in succession across the permafrost region. Scientists project that between 200 and 300 gigatons of CO2 equivalents could be released this century under warming scenarios of 1.8 to 3.6 degrees Celsius—vastly exceeding current European Union emissions and potentially approaching levels comparable to current United States or Chinese emissions.
The type of greenhouse gas released depends on whether thawing creates dry or wet environments. Dry conditions produce carbon dioxide through oxidation, while oxygen-depleted wetlands and lakes generate methane, which is approximately 30 times more potent as a greenhouse gas over short timeframes. A critical research challenge involves determining what proportion of thawing permafrost will become wetter versus drier.
A time lag of decades exists between climate warming and permafrost response due to insulating vegetation and soil layers. This means certain permafrost areas, particularly in northern Sweden and Finland, are already committed to disappearing despite current climate stabilization efforts, while vast Siberian and Canadian permafrost regions could largely remain intact with successful climate mitigation.
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