June ocean surface temperatures set new record outside polar regions

On 21 June, ocean surface temperatures outside the polar regions exceeded the previous highs recorded at the same time in 2023 and 2024, according to the Guardian’s reporting on data from the Copernicus Climate Change Service. Copernicus announced the new peak on Wednesday and warned it would likely affect weather patterns, the global climate and marine ecosystems. The timing coincides with the early phase of an El Niño event that forecasters expect to be among the strongest in decades.

The immediate significance of a June record is that it arrives before the usual seasonal peak, which typically occurs in July and August, Copernicus director Carlo Buontempo told the Guardian. If the baseline is already elevated at the start of summer, the threshold for marine heatwaves and extreme weather shifts lower: storms draw energy from warm surface waters, and heat stored in the ocean can sustain anomalies for months. Copernicus cautioned that it is still too early to know whether the current spike will prove temporary or persist.

The story also underlines how much of the climate system is now being measured in the ocean rather than in the air. Oceans absorb more than 90% of the excess energy in the Earth system, driven primarily by burning fossil fuels, the Guardian reports. Copernicus estimates Earth’s energy imbalance reached a record 23 zettajoules last year, more than double the average of the previous two decades. The same reporting compares the implied heating rate to “Hiroshima bombs per second,” rising from about five in 2020 to closer to 11 last year.

El Niño adds a second layer: it can temporarily redistribute heat between ocean and atmosphere, amplifying global temperatures and shifting rainfall patterns. The Guardian notes that the 2023 June record preceded an El Niño and a period of damaging heatwaves, floods and storms. This year’s early record arrives with Copernicus warning that more temperature records may fall in the coming months.

For Europe, the institutional angle is that Copernicus—part of the EU space programme—has become a key supplier of climate signals that governments and insurers increasingly treat as operational data. Yet the consequences Copernicus flags, from ecosystem stress to extreme-weather risk, land in budgets that are often built around historical averages.

Copernicus’ announcement was tied to a single date: 21 June. The next test will be whether the summer peak arrives on top of it.