Ocean surface temperatures reached a record high on 21 June, exceeding the extraordinary levels observed at the same time in 2023 and 2024, according to the Copernicus Climate Change Service. Scientists warn this could trigger another burst of extreme heat this summer, with significant consequences for weather patterns, the global climate, and marine ecosystems.
Record-Breaking Ocean Heat
On 21 June, temperatures outside the polar regions broke the previous June records set in 2023 and 2024. The Copernicus Climate Change Service, part of the EU's space programme, reported the new peak on Wednesday. It cautioned that this record would likely bring severe repercussions, especially as it coincides with the early phases of an El Niño event forecast to be the strongest in decades.
When the previous ocean record for June was set in 2023, scientists described the trends as "worrying," "terrifying," and "bonkers" because they far exceeded expectations. That record preceded an El Niño and a period of devastating global heatwaves, floods, and storms.
Wider Climate Implications
Although attention often focuses on land temperatures, oceans provide a more comprehensive picture of climate imbalance. Oceans absorb over 90% of the excess energy in the Earth system, primarily from burning fossil fuels like oil, coal, and gas. This energy imbalance hit a record 23 zettajoules last year, more than double the average of the previous two decades.
As a result, ocean warming is accelerating. In 2020, the heat added to oceans was equivalent to about five Hiroshima bombs per second; last year, it rose to nearly 11 Hiroshima explosions per second. UN Secretary-General António Guterres has warned that "Earth is being pushed beyond its limits."
Future Outlook
Scientists said it is too early to determine whether the sea surface heating will be temporary or worsen, as annual peaks typically occur in July and August. However, Carlo Buontempo, Copernicus director at the European Centre for Medium-Range Weather Forecasts, warned it could signal a new phase leading to uncharted territory: "With ocean temperatures at these levels and El Niño on the horizon, we are likely to see more temperature records fall in the coming months."
Last month, the UK and many European countries experienced new heat records, while Antarctica saw unusually warm winter conditions. The record ocean temperatures raise fears of further extreme weather events globally.
