New observations obtained in 2021 and 2022 are presented and used to investigate the trend of the carbonate system (including pH and aragonite saturation state, Ω_ar) in the southern sector of the Mozambique Channel. Using historical and new data in April–May we observed an acceleration of the acidification ranging from -0.012 TS.decade^-1 in 1963–1995 to -0.027 (±0.003) TS.decade^-1 in 1995–2022. Result from a neural network (FFNN) model for all seasons also suggests faster pH trend in recent decades, -0.011 TS.decade^-1 over 1985–1995 and -0.018 TS.decade^-1 over 1995–2022. In May 2022 we estimated Ω_ar of 3.49, about 0.3 lower than observed in May 1963 (Ω_ar = 3.86). The lowest Ω_ar value of 3.23 was evaluated from the FFNN model in September 2023 that corresponds to the hypothetical critical threshold value (3.25) for coral reefs. In 2025 a marine heat wave was observed in this region (sea surface temperature up to 30 °C) and data from a BGC-Argo float indicate that sea surface pH was low in January 2025 (pH = 7.95) whereas War was low in Mach 2025 (Ω_ar = 3.2). A projection of the C_T concentrations based on observed anthropogenic CO₂ in subsurface water and emissions scenario, suggests that a risky level for corals (Ω_ar < 3) could be reached as soon as year 2034.