Abstract
Degrading permafrost can alter ecosystems, damage infrastructure, and release enough carbon dioxide (CO2) and methane (CH4) to influence global climate. The permafrost carbon feedback (PCF) is the amplification of surface warming due to CO2 and CH4 emissions from thawing permafrost. An analysis of available estimates PCF strength and timing indicate 120 ± 85 Gt of carbon emissions from thawing permafrost by 2100. This is equivalent to 5.7 ± 4.0% of total anthropogenic emissions for the Intergovernmental Panel on Climate Change (IPCC) representative concentration pathway (RCP) 8.5 scenario and would increase global temperatures by 0.29 ± 0.21 °C or 7.8 ± 5.7%. For RCP4.5, the scenario closest to the 2 °C warming target for the climate change treaty, the range of cumulative emissions in 2100 from thawing permafrost decreases to between 27 and 100 Gt C with temperature increases between 0.05 and 0.15 °C, but the relative fraction of permafrost to total emissions increases to between 3% and 11%. Any substantial warming results in a committed, long-term carbon release from thawing permafrost with 60% of emissions occurring after 2100, indicating that not accounting for permafrost emissions risks overshooting the 2 °C warming target. Climate projections in the IPCC Fifth Assessment Report (AR5), and any emissions targets based on those projections, do not adequately account for emissions from thawing permafrost and the effects of the PCF on global climate. We recommend the IPCC commission a special assessment focusing on the PCF and its impact on global climate to supplement the AR5 in support of treaty negotiation.
Highlights
IntroductionThe release of CO2 and CH4 from thawing permafrost will amplify global warming due to anthropogenic greenhouse gas emissions and further accelerate permafrost degradation
We evaluate how the permafrost carbon feedback (PCF) influences the negotiations of anthropogenic emissions targets (Schaefer et al 2012)
The Global Terrestrial Network for Permafrost (GTN-P) consists of two global networks to monitor permafrost: the thermal state of permafrost (TSP) and the Circumpolar Active Layer Monitoring (CALM) networks
Summary
The release of CO2 and CH4 from thawing permafrost will amplify global warming due to anthropogenic greenhouse gas emissions and further accelerate permafrost degradation. The PCF is irreversible on human time scales because in a warming climate, the burial mechanisms described above slow down or stop, so there is no way to convert CO2 into organic matter and freeze it back into the permafrost. There are few published estimates that quantify CO2 and CH4 emissions from thawing permafrost, making it difficult to evaluate the effects of the PCF on global climate. We perform a detailed meta-analysis of currently published projections of future permafrost degradation and associated emissions of CO2 and CH4 to better quantify how the PCF influences global climate. We evaluate how the PCF influences the negotiations of anthropogenic emissions targets (Schaefer et al 2012)
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