The report, which was created by over 100 scientists and subjected to peer review, was released in late September 2025. It was based on decades of in-situ ocean measurements, satellite data, and deep-sea instruments. It was painstakingly created, comprehensive, and detailed. Additionally, it landed in a news cycle full of other stories, and the majority of what it contained—nine distinct warnings about the current state of the ocean—barely made an impression outside of specialized circles. Correcting that seems worthwhile.
Every year, the Copernicus Marine Service and Mercator Ocean International publish the ninth edition of the Copernicus Ocean State Report, which focuses on the extreme events of 2023 and 2024 and includes data going back to the 1970s. Over the course of those years, it discovered that the ocean was acting in ways that no prior decade had anticipated. In the spring of 2024, the average sea surface temperature worldwide hit 21°C. That figure broke earlier records from 2015 and 2016 by 0.25°C, which may seem insignificant, but when you consider that 0.25°C across the entire surface of the world’s oceans represents a massive amount of accumulated energy. Since 1982, the northeastern Atlantic and surrounding seas have warmed by 0.27°C every ten years, which is twice the rate of global warming. Ocean heat gain between 2005 and 2025 is more than twice as fast as it was between 1960 and 2005. There is no slowdown in the acceleration.
Marine heatwaves fall in between the concerning and the hard to fully envision. The Tropical North Atlantic experienced a heatwave in 2023 that just wouldn’t go away. More than 99 percent of the area was impacted, and some places experienced heatwave conditions for more than 300 days in a row, shattering all prior records for intensity, duration, and extent at the surface and below. The Mediterranean experienced its own protracted crisis: from May 2022 to early 2023, the longest-lasting marine heatwave ever recorded caused surface temperatures to rise by 4.3°C. You can read those numbers without experiencing their full weight. However, the ecological effects were distinct and noticeable. Arriving in warmer water, invasive Atlantic Blue Crabs destroyed between 75 and 100 percent of the local clam production in the Po River delta in northeastern Italy, a region of flat, fertile coastline that has supported clam farming for generations. Bearded fireworms are a threat to biodiversity, the tourism industry, and human safety in Sicily’s coastal waters. These are not forecasts. They took place.
| Field | Details |
|---|---|
| Report Name | Copernicus Ocean State Report, 9th Edition (OSR 9) |
| Published | September 23–30, 2025 |
| Published By | Copernicus Marine Service & Mercator Ocean International (on behalf of the European Commission) |
| Contributors | Over 100 experts from Europe and around the world; peer-reviewed in collaboration with the journal State of the Planet |
| Data Range | 1970s to present; focus on 2023 and 2024 extreme events |
| Record Sea Surface Temp | 21°C global average in spring 2024 — 0.25°C above previous records (2015–2016) |
| Ocean Heat Gain Rate | 2005–2025 rate more than double that of 1960–2005; +0.14 W/m² per decade |
| Sea Level Rise Since 1901 | 228mm total; rate of rise 30% faster in 2010s vs. 1990s |
| Arctic Ice Loss (Feb 2025) | 1.6 million km² below long-term average — roughly 3x the size of France |
| Mediterranean Warming Rate | +0.41°C per decade; 2022–2023 heatwave pushed surface temps 4.3°C above normal |
| Po River Delta Impact | Invasive Atlantic Blue Crabs caused 75–100% collapse in clam production |
| Plastic Pollution Overlap | 75%+ of countries emitting over 10,000 tonnes of plastic waste annually are located near endangered coral reefs |
| Acidification Rate | Over 10% of marine biodiversity hotspots acidifying faster than global average |
| New Monitoring Tool | “Starfish Barometer” — launched June 2025; visualizes human activity vs. ocean health across five dimensions |
| Copernicus Programme | European Union’s Earth Observation Programme — satellite observations, in-situ data, and numerical modelling |
Since the beginning of the 20th century, sea levels have increased by 228 millimeters, reaching all-time highs in 2024. Between the 1990s and the 2010s, the rate of increase rose by thirty percent. According to the report, European nations with high coastal population densities—more than 200 people per square kilometer—are disproportionately found close to ocean regions where sea level rise is occurring at the fastest rate. The coasts of Europe are home to about 200 million people. In the upcoming centuries, a number of low-lying coastal UNESCO World Heritage sites may experience partial or complete flooding. Most policy rooms don’t feel a sense of urgency because the timeline is long enough. However, the trend line is clear.
In 2024 and the first part of 2025, sea ice in the Arctic and Antarctic reached record lows. In comparison to the long-term average, the Arctic had lost about 1.6 million square kilometers of ice by February 2025. This area was almost three times larger than France. More than 10% of marine biodiversity hotspots are experiencing faster-than-average ocean acidification, endangering the reef structures, plankton, and shellfish that serve as the foundation of marine food chains. Near endangered or critically endangered coral reefs are 75% of the nations that produce more than 10,000 tonnes of plastic waste per year. At the same time, rapid warming and acidification are affecting 30% of critically endangered corals.
When you see all of this come together in one document, you are more struck by what Karina von Schuckmann, director of Copernicus Marine Ocean State Reporting, stated clearly in her statement that went with the report: the science is clear. Record extremes are increasing, the ocean is changing quickly, and the causes are known. This year, the report unveiled the Starfish Barometer, a new monitoring tool that was introduced on World Ocean Day in June. It is a visual framework that links the state of the ocean, human pressures, societal harms, protection efforts, and opportunities. It’s a well-thought-out effort to make something incredibly complicated understandable to decision-makers. For now, it remains to be seen if those individuals are reading it.
The OSR 9 findings give the impression that the discrepancy between the data and the institutional response is growing in ways that will be difficult to close. The report is neither a model nor a projection. It is an account of past events. The delta is already home to the crabs. Already, the ice is gone. It’s already 21°C. There were no forecasts in the Copernicus Ocean State Report’s ninth edition. It provided receipts.
