Ocean Acidification: Atmospheric CO2 and Surface Ocean pH Observations

Annual Mauna Loa CO2 (right axis) with multiple open-ocean pH station observations (left axis). Lower pH means higher acidity. Dashed horizontal lines mark a preindustrial benchmark (~8.20) and a modern global reference (~8.10).

Interpretation: Surface ocean pH is logarithmic, so a drop of 0.10 pH units corresponds to about ~25.9% higher hydrogen ion concentration (more acidic conditions). The station lines are annual means from measured pH observations (NOAA PMEL moorings), shown as representative open-ocean records rather than a single global annual pH mean. Use Data: Monthly / Annual for finer or smoother detail. Use pH scale: Raw / Normalized to compare absolute pH versus relative change. Use Emphasis to make the pH slope look steeper or flatten pH so the CO2 slope dominates.

NOAA GML Mauna Loa monthly CO2 (annualized in this script) • NOAA PMEL moored Surface Ocean CO2 and Ocean Acidification time-series (pH_sw, annualized in this script) • Generated by generate_ocean_acidification_chart.py