Ocean surface temperatures hit a record high on 21 June, exceeding the extraordinary highs observed at the same time in 2023 and 2024, according to the Copernicus Climate Change Service. The new peak raises fears of another burst of extreme heat this summer, with potential consequences for weather patterns, the global climate, and marine ecosystems.
Record-Breaking Ocean Heat
On 21 June, temperatures outside the polar regions surpassed previous records set in 2023 and 2024, the Copernicus Climate Change Service reported on Wednesday. The agency warned that this new peak would likely bring “consequences for weather patterns, global climate and marine ecosystems,” particularly as it coincides with the earliest 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 were so far outside expectations. That presaged an El Niño and a period of devastating global heatwaves, floods, and storms. The 2023 record has now been surpassed, and much of the world is once again seeing an alarming rise in temperatures. Last month, the UK and many other European countries sweltered amid new heat records, while Antarctica experienced unprecedentedly balmy winter conditions.
Oceans as Climate Indicators
Although the focus is usually on land temperatures, oceans provide a fuller picture of how much the climate is being pushed out of balance by human-caused warming. Surface temperatures are affected by solar radiation, water currents, and the buildup of heat in the depths. Oceans absorb more than 90% of the excess energy in the Earth system, primarily caused by burning fossil fuels such as oil, coal, and gas. That imbalance hit a record 23 zettajoules last year, more than double the average of the previous two decades.
As a result, the oceans are warming at an accelerating rate. In 2020, the amount of heat being added to the oceans was equivalent to about five Hiroshima bombs a second. Last year, it was closer to 11 Hiroshima explosions a second. The UN Secretary-General, António Guterres, has warned that “Earth is being pushed beyond its limits.”
Future Projections and Warnings
Scientists said it was too early to say whether the sea surface heating would prove temporary or even worsen, because annual peaks are usually registered in July and August. However, Carlo Buontempo, Copernicus director at the European Centre for Medium-Range Weather Forecasts, warned it could indicate the beginning of a new phase, leading once more 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.”
Copernicus is part of the EU’s space programme.
