Abstract Climate change driven increases in temperature, vapour pressure deficit, and drought frequency threaten to enhance peatland wildfire activity and combustion burn severity, potentially emitting vast stores of ancient carbon. Here, we quantify the sensitivity of northern peatland wildfire combustion to projected climate change using an integrated modelling framework. We used the Global Fire Emissions Database burned area product (v5.1) to train random forest models of North America and Eurasia to predict landscape burn frequency as a function of land cover and climatological variables. Future changes in area burned were estimated from multiple general circulation models and across several climate scenarios. Peat burn severity was estimated from simulated peat moisture profiles modelled with Hydrus-1D, which varied initial water table position, potential evapotranspiration rate, drying time, and peat hydrophysical properties. Ensemble results project a moderate increase in northern peatland area burned by the end of the century (3.2 to 3.6 Mha yr -1 across climate scenarios) compared to our contemporary estimate of 2.75 Mha yr -1 . The combined effects of increased area burned and depth of burn result in projected range of peatland smouldering carbon emissions of 47.5–55.3 Mt C yr -1 by the end of the century, compared to our contemporary ensemble estimate of 35.8 Mt C yr -1 . While modelled burn severity was comparable between North America and Eurasia, Eurasia is estimated to contribute approximately 70% of northern peatland smouldering carbon emissions due to a higher average burn rate and larger peatland area. As a result of increased peatland smouldering carbon emissions, our end-of-century peatland combustion findings suggest that, regionally, peatlands have the potential to flip from a net carbon sink to a net carbon source under a high emission scenario As such, incorporating mechanistic peatland combustion processes into Earth system models is essential to reduce uncertainty in future climate projections and to inform mitigation strategies aimed at preserving the global peatland carbon stock and carbon sequestration function.
