Overview

• The Potsdam Institute for Climate Impact Research unveiled its 2025 assessment at the UN General Assembly in New York, confirming the ocean acidification boundary is now exceeded and noting that improved data and revised calculations contributed to the update.
• The threshold is defined by aragonite at 80% of its pre‑industrial concentration, and observations show the oceans have fallen below that level as surface pH has dropped by about 0.1, equivalent to a 30–40% rise in acidity.
• Researchers identify the primary driver as the oceans’ absorption of carbon dioxide from burning fossil fuels, with estimates that the seas have taken up roughly 30% of the excess CO2 released by oil, gas and coal.
• Rising acidity threatens organisms that build calcium‑carbonate shells or skeletons—such as corals, molluscs and key plankton—raising the risk of cascading disruptions to marine food webs.
• Six other planetary boundaries were already exceeded, leaving only atmospheric aerosols and stratospheric ozone within set limits, as speakers at the briefing urged governments to listen to the science.