Fig. 2: Acidification potential of cumulative carbon uptake.

Results are for GFDL-CM4 (a, d), the concentration-driven version of GFDL-ESM4 (b, e), and the emission-driven version of GFDL-ESM4 (c). Results are shown for the higher emissions ssp585 scenario (a–c) and lower emissions ssp245 scenario (d, e). The acidification potential metric reflects how efficient global anthropogenic carbon emissions are at driving surface ocean acidification at each grid point. The metric is defined as the change in surface hydrogen ion concentration (mol [H⁺] m⁻²) averaged over years 2081–2100 normalized by the time-integrated air-sea CO₂ flux ( μmol CO2 m⁻²). Although the increase in [H⁺] is positive at all locations, the cumulative carbon uptake at a grid point may be negative, especially in the tropics. Only positive values of this acidification potential metric are shown.