Ocean heat records broken, fueling sea level rise and extreme weather

Key facts

• Global sea surface temperatures have broken records for the time of year, reaching 21.0°C on June 21.
• This marks a new high, exceeding previous records set in 2023 and 2024.
• The warming trend is attributed to climate change, with El Niño conditions contributing.
• Warmer oceans can lead to sea level rise, ice melt, and increased energy for storms.
• Scientists warn of potential for further temperature records and more frequent extreme weather events.

New data from the Copernicus Climate Change Service and Copernicus Marine Service reveals that global sea surface temperatures have reached record highs for this time of year, signaling a concerning long-term trend driven by climate change. On June 21, the global average sea surface temperature hit 21.0°C, surpassing previous records from 2023 and 2024. Scientists describe these conditions as entering "uncharted territory."

While the onset of El Niño conditions in the Equatorial Pacific has contributed to the record-breaking reading, it is part of a broader pattern. Over the last three years, ocean temperatures outside polar regions have been between 0.35°C and 0.73°C higher than the long-term average. Carlo Buontempo, Director of the Copernicus Climate Change Service, warned that these elevated temperatures, combined with El Niño, suggest more temperature records are likely to fall.

The impact of warmer oceans extends beyond marine ecosystems. They provide extra energy to storms, increase evaporation leading to heavy rainfall and flooding, and contribute to sea level rise and ice melt. More frequent and intense marine heatwaves can disrupt fisheries and affect coastal economies, while also intensifying extreme heat on land. Climate scientist Friederike Otto cautioned that extended periods above the 1.5°C warming threshold, as warned by the Paris Agreement, threaten a "whole range of extreme weather events" for which many cities are unprepared. Otto also emphasized that while El Niño is a cyclical phenomenon, climate change will worsen unless fossil fuel burning ceases.