The next generation of climate model should account for the evolution of mineral-organic interactions with permafrost thaw

The Earth’s high latitude regions are warming twice as fast as the global average which enhances the thawing of permafrost, i.e. the perennially frozen ground which underlies about 25% of the exposed land surface in the Northern Hemisphere (Brown et al 1998). Permafrost thaw exposes previously frozen organic carbon (OC) to microbial decomposition with subsequent emission of the greenhouse gases carbon dioxide (CO2) and methane (CH4) into the atmosphere, creating positive feedback on global warming, i.e. the permafrost carbon feedback (Schuur et al 2015). Permafrost contains 1460–1600 GtC, almost twice the C in the atmosphere (IPCC 2019), and 15 ± 3% of that OC stock could be emitted as greenhouse gases by 2100 (Schuur et al 2015). On an annual basis, this would represent 22%–31% of the current anthropogenic C emissions (considering anthropogenic C emissions from IPCC 2019). Most of that C would be emitted as CO2 but it is estimated that 2.3% of the permafrost C emissions will be released as CH4 (Schuur et al 2015). This has implications for the Earth’s radiative balance, given the larger global warming potential of CH4 at the century time scale. Therefore, evidence is mounting that permafrost thaw represents a tipping element in the Earth climate system (Lenton et al 2019). Yet uncertainties are associated with how this will unfold