A new study has for the first time comprehensively accounted for permafrost carbon release when estimating emission budgets for climate targets.
The results show that the world might be closer to exceeding the budget for the long-term target of the Paris climate agreement than previously thought.
Emissions budgets represent the upper limit of total carbon dioxide (CO2) emissions associated with remaining below a specific global average temperature. The simplicity of the concept has made it an attractive tool for policymakers to use in efforts to remain below dangerous levels of warming, even though it is strongly dependent on the assumption of a linear relationship between global temperature rise and cumulative CO2 emissions due to human activity. In their study, the researchers investigated how current emission budgets are impacted by the non-linear feedback phenomenon of CO2 and methane emissions caused by permafrost thaw.
Permafrost is soil that has been frozen year round for at least two years. Due to the long periods that it remains frozen, the soil stores large amounts of carbon and other nutrients from organic matter, and thus represents a large carbon reservoir, which is seldom considered in projections of potential future global warming. The upper layer of permafrost (the active layer) periodically thaws in the summer, but in recent years, the active layer of permafrost has gradually been expanding due to increasing temperatures. This means that more permafrost is thawing and thus releasing the previously trapped carbon into the atmosphere.
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