Zicheng Yu , Fortunat Joos, Thomas K. Bauska, Benjamin D. Stocker, Hubertus Fischer, Julie Loisel, Victor Brovkin, Gustaf Hugelius, Christoph Nehrbass-Ahles, Thomas Kleinen

Northern peatlands store large amounts of carbon (C) and have played an important role in the global carbon cycle since the Last Glacial Maximum. Most northern peatlands have established since the end of the deglaciation and accumulated C over the Holocene, leading to a total present-day stock of 500 ± 100 GtC. This is a consolidated estimate, emerging from a diversity of methods. Recently, Nichols and Peteet (2019 Nature Geoscience 12: 917-921) presented an estimate of the northern peat C stock of 1055 GtC—exceeding previous estimates by a factor of two. Here, we argue that this is an overestimate, caused by systematic bias introduced by their inclusion of data that is not representative for the major peatland regions and of records that lack direct measurements of C density. Furthermore, we argue that their estimate cannot be reconciled within the constraints offered by ice-core and marine records of stable C isotopes and estimated contributions from other processes that affected the terrestrial C storage during the Holocene.