The impact of the permafrost carbon feedback on global climate

Degrading permafrost can alter ecosystems, damage infrastructure, and release enough carbon
\ndioxide (CO2) and methane (CH4) to influence global climate. The permafrost carbon feedback
\n(PCF) is the amplification of surface warming due to CO2 and CH4 emissions from thawing
\npermafrost. An analysis of available estimates PCF strength and timing indicate 120 ± 85 Gt of
\ncarbon emissions from thawing permafrost by 2100. This is equivalent to 5.7 ± 4.0% of total
\nanthropogenic emissions for the Intergovernmental Panel on Climate Change (IPCC)
\nrepresentative concentration pathway (RCP) 8.5 scenario and would increase global
\ntemperatures by 0.29 ± 0.21 °C or 7.8 ± 5.7%. For RCP4.5, the scenario closest to the 2 °C
\nwarming target for the climate change treaty, the range of cumulative emissions in 2100 from
\nthawing permafrost decreases to between 27 and 100 Gt C with temperature increases between
\n0.05 and 0.15 °C, but the relative fraction of permafrost to total emissions increases to between
\n3% and 11%. Any substantial warming results in a committed, long-term carbon release from
\nthawing permafrost with 60% of emissions occurring after 2100, indicating that not accounting
\nfor permafrost emissions risks overshooting the 2 °C warming target. Climate projections in the
\nIPCC Fifth Assessment Report (AR5), and any emissions targets based on those projections, do
\nnot adequately account for emissions from thawing permafrost and the effects of the PCF on
\nglobal climate. We recommend the IPCC commission a special assessment focusing on the PCF
\nand its impact on global climate to supplement the AR5 in support of treaty negotiation.