Effects of regional variation in climate and SOC decay on global warming potential and eutrophication attributable to cereal production in Norway

•We examined cereal production under contrasting climatic conditions in Norway.•Focus was on the role of SOC decay in the life cycle context; cradle to farm-gate.•SOC-related CO2-eq. emissions may exceed the sum of all other sources of emission.•Our wide system boundaries resulted in 0.5–0.9kgCO2-eq. per kg grain.•Main effort should be to improve the management of soil and crops at the farm.