A new warning from the ocean
Global oceans have just recorded their hottest June ever observed, the European Copernicus Marine observatory announced on Wednesday, July 1. Average sea surface temperature reached 20.98°C in June, beating the previous June record of 20.89°C set in 2024.
This new ocean heat record confirms the rapid rise of marine heatwaves, at a time when the sea is absorbing around 90% of the excess heat caused by human-driven climate change.
Marine ecosystems under pressure
Marine heatwaves are periods of unusually high sea surface temperatures that can last for weeks, months or even years. They are now becoming more frequent, longer and more intense. In June 2026, large parts of the global ocean were warmer than average, with strong anomalies in the Mediterranean Sea, the Pacific Ocean and several coastal regions. In the Mediterranean, waters between Corsica and the Côte d’Azur have already reached levels close to 29–30°C during recent heat episodes.
Why this matters for maritime security
This overheating is not only an environmental issue. Warmer seas reduce dissolved oxygen, weaken coral reefs, damage seagrass meadows and kelp forests, and can trigger mass mortality events among fish, sponges and gorgonians. They also disturb food chains and help invasive species move into new waters, including in the Mediterranean through the Suez Canal. For coastal communities, fisheries and maritime economies, the key message is clear: ocean warming is becoming a direct pressure on marine stability, biodiversity and long-term security.
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