June global sea surface temperatures have climbed to record highs, prompting concerns over extreme weather, flooding, sea level rise and stress to global ocean ecosystems.

The record, announced by the European Union's Copernicus Earth observation program on July 1, surpassed the previous record set in June 2024, with experts warning that more temperature records will likely be set over the coming months.

"Current conditions could indicate the beginning of a new phase, leading, once more, to uncharted territory," Carlo Buontempo, director of the Copernicus Climate Change Service at the European Centre for Medium-Range Weather Forecasts (ECMWF), said in a statement. "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.”

The record temperature was set on June 21, when the Copernicus Climate Change Service recorded global ocean surface temperatures of 20.86 degrees Celsius (69.55 degrees Fahrenheit), beating the record temperature of 20.83 C (69.49 F) set in 2023 and 2024. This measurement was corroborated by the Copernicus Marine Service, an independent dataset that reported temperatures of 21.0 C (69.8 F).

The recent sea surface heating did not occur evenly across the globe. In some areas, such as the Mediterranean, temperatures in June were up to 8 C (14.4 F) higher than average for the period from 1990 to 2020, as per data recorded on June 29, according to the European Space Agency.

The most significant rises in temperature were set in the Mediterranean, the Baltic Sea, bands across the Pacific and off the coasts of Northern Canada.

Warmer ocean temperatures have wide-ranging impacts. "Higher ocean temperatures keep the atmosphere warm for longer, provide extra energy to storms and increase evaporation, thus enhancing the potential for extreme precipitation and flooding," Copernicus Climate Change Service representatives said in the statement. "Ocean warming also contributes to sea level rise and ice melt, and stresses marine ecosystems."

According to data from the Copernicus Climate Change Service, the newly declared El Niño in the Pacific Ocean — the warm phase of a natural climate cycle. This El Niño is likely to reach levels that have not been seen in decades, with more temperature records expected to be set over the coming months as this Pacific heat is injected into an already warming world.

The service added that it remains to be seen whether these temperature spikes are temporary or indicative of longer term trends.