Fig. 4

Inter-annual variations in the global mean availability of light (a), water (b), and nitrogen (c), and leaf area index (LAI, d) in the control simulation (right vertical axis and the red line). Differences in the four variables between the control simulation, and the fixed CO₂ (CO₂_fixed), fixed precipitation (Prec_fixed), fixed temperature (Tair_fixed), and fixed shortwave radiation (Swd_fixed) simulations (left vertical axis). For example, “Light_Control–Light_CO₂_fixed” refers to the difference in light availability between the control and the CO₂_fixed simulations, and negative values indicate that changes in CO₂ led to a decrease in light availability