Ocean temperatures set June record as El Niño and climate change push seas into uncharted territory

Record-setting June

On 21 June, the EU’s Copernicus climate service and its marine service measured global sea surface temperatures of 20.86 °C and 21.0 °C respectively, surpassing previous records for that date from 2023 and 2024. Those earlier records stood at 20.83 °C (climate service) and 20.9 °C (marine service). Separate data from the University of Maine’s Climate Reanalyzer showed a reading of 20.97 °C for the same day, holding steady through 28 June.

El Niño’s amplifying role

The jump is driven by a mix of man-made climate change and the natural climate phenomenon El Niño, which weakens trade winds in the tropical Pacific every two to seven years. The current El Niño is still in its early phase, whereas the 2024 record occurred just as the previous El Niño was fading. Copernicus director Carlo Buontempo said the conditions suggest a new phase that could lead to further records.

“The current conditions may indicate the start of a new phase that will once again bring us into unknown territory. Given the present sea temperatures and the emerging El Niño, further temperature records are likely to be broken in the coming months.”

Consequences: floods, storms, coral stress

Warmer oceans keep the atmosphere warm longer, add energy to storms, and increase evaporation, raising the risk of extreme precipitation and flooding. They also accelerate sea-level rise, ice melt, and coral bleaching. Marine heatwaves stress fisheries and can intensify heat extremes on nearby land. Over the past three years, global sea temperatures outside polar regions ran 0.35 °C to 0.73 °C above the long-term average.

Measuring a warming planet

Copernicus draws on local measurements and satellite data from ESA, while the University of Maine uses similar satellite inputs. Oceans absorb most of the extra heat from human greenhouse gas emissions; reducing fossil fuels, expanding wind and solar, and upgrading grids and storage are essential to limit further warming.

Copernicus Climate Service20.86

Copernicus Marine Service21

University of Maine20.97

Copernicus Climate Service

20.86 °C

Copernicus Marine Service

21 °C

University of Maine

20.97 °C

Data from the article text