Abstract. The capacity of the terrestrial biosphere to sequester carbon and mitigate climate change is governed by the ability of vegetation to remove emissions of CO₂ through photosynthesis. Tropospheric O₃, a globally abundant and potent greenhouse gas, is, however, known to damage plants, causing reductions in primary productivity. Despite emission control policies across Europe, background concentrations of tropospheric O₃ have risen significantly over the last decades due to hemispheric-scale increases in O₃ and its precursors. Therefore, plants are exposed to increasing background concentrations, at levels currently causing chronic damage. Studying the impact of O₃ on European vegetation at the regional scale is important for gaining greater understanding of the impact of O₃ on the land carbon sink at large spatial scales. In this work we take a regional approach and update the JULES land surface model using new measurements specifically for European vegetation. Given the importance of stomatal conductance in determining the flux of O₃ into plants, we implement an alternative stomatal closure parameterisation and account for diurnal variations in O₃ concentration in our simulations. We conduct our analysis specifically for the European region to quantify the impact of the interactive effects of tropospheric O₃ and CO₂ on gross primary productivity (GPP) and land carbon storage across Europe. A factorial set of model experiments showed that tropospheric O₃ can suppress terrestrial carbon uptake across Europe over the period 1901 to 2050. By 2050, simulated GPP was reduced by 4 to 9 % due to plant O₃ damage and land carbon storage was reduced by 3 to 7 %. The combined physiological effects of elevated future CO₂ (acting to reduce stomatal opening) and reductions in O₃ concentrations resulted in reduced O₃ damage in the future. This alleviation of O₃ damage by CO₂-induced stomatal closure was around 1 to 2 % for both land carbon and GPP, depending on plant sensitivity to O₃. Reduced land carbon storage resulted from diminished soil carbon stocks consistent with the reduction in GPP. Regional variations are identified with larger impacts shown for temperate Europe (GPP reduced by 10 to 20 %) compared to boreal regions (GPP reduced by 2 to 8 %). These results highlight that O₃ damage needs to be considered when predicting GPP and land carbon, and that the effects of O₃ on plant physiology need to be considered in regional land carbon cycle assessments.