Global ocean change in the era of the triple planetary crisis

Abstract. This ocean narrative is grounded in global ocean indicators and framed around climate, biodiversity, and sustainable development. In 2024, global ocean heat content (OHC) reached record levels, with continued heat uptake of 0.35 ± 0.1 W m−2 and steady acceleration of 0.14 ± 0.1 W m−2 per decade since the 1960s. Sea surface temperatures (SSTs) exceeded 21 °C globally in both 2023 and 2024, while global mean sea level rise reached its highest recorded rate of 4.1 ± 0.1 mm yr−1 (2016–2024). No part of the ocean is untouched by the so-called triple planetary crisis as proclaimed by the United Nations, where pollution, biodiversity loss, and climate change are putting pressure on marine systems worldwide. Over 8 % (10 %) of marine biodiversity hotspots, 8 % (11 %) of large marine ecosystems (LMEs), and 14 % (32 %) of Areas Beyond National Jurisdiction (ABNJ) are exposed to warming (acidification) beyond global rates. The triple planetary crisis converges across all ocean basins, with 16 % (30 %) of endangered (critically endangered) corals exposed to rapid ocean warming or acidification (rapid pH loss), and 75 % of countries emitting > 10 000 t plastic waste are near critically endangered and endangered corals. These overlapping pressures threaten key species, ecosystems, and the ocean's role in climate stability. These findings underscore the need for enhanced and sustained ocean observing systems, improved information on uncertainties in indicator design, and robust science-based information to guide policy, planning, and action for protecting the ocean. The ocean is our sentinel, reflecting the health of the planet and the trajectory of future environmental changes. Protecting the ocean through concerted global cooperation informed by integrated evidence-based and strategic ocean knowledge is essential to ensure the ocean can continue to play its crucial role in sustaining life and regulating Earth's climate.