Fig. 5: Effect of greenhouse warming on the North American GPP.

The evolution of North American GPP (gC m−2 month−1) in the model experiments includes several scenarios: quadrupling of CO2 (4×CO2), quadrupling of CO2 with preindustrial mean TIO SST (4×CO2+TIOclim), present-day CO2 levels (PD), and present-day CO2 with preindustrial mean TIO SST (PD+TIOclim). Perturbations are introduced at time zero and maintained throughout the experiments. A 5-year running mean is applied to all the curves. The thick line indicates average values, while shading represents the ensemble spread over 50 years.