The figure surpasses the previous record of 20.89 degrees Celsius, set in June 2024, and reflects the combined effects of the El Niño weather phenomenon and long-term climate warming, Copernicus said.
The observatory noted the current situation is especially concerning because, two years ago, El Niño was already weakening by this point. This year, by contrast, only the early stages of the cycle have been declared, meaning its full intensity is expected to hit in the coming months.
Data from the past three years show global sea temperatures outside polar regions have consistently remained 0.35 to 0.73 degrees Celsius above the long-term average, according to Copernicus.
El Niño occurs every few years when trade winds weaken, allowing warm surface waters in the western Pacific to shift eastward. The shift alters wind patterns and atmospheric circulation, triggering a cascade of extreme weather events — including droughts, floods and unprecedented heat — that affect weather worldwide.
Copernicus researchers said the tropical Pacific recorded its hottest first half of the year on record, with an average temperature of 26.91 degrees Celsius, matching the historic high set in 2016.
The Mediterranean Sea faces particularly severe conditions. June measurements showed an average temperature there of 24.34 degrees Celsius, with marine heat waves covering 98% of the sea. Copernicus said the significant heat anomalies pose a serious threat to marine organisms such as corals, mollusks and sea urchins, while the thermal expansion of warming waters is driving dangerous global sea level rise.
Oceans play a key role in regulating climate, absorbing nearly 90% of the excess heat generated by human industrial activity, primarily from the burning of fossil fuels, according to Copernicus. Since the start of the year, intense heat waves have affected 82% of the world's total ocean surface.
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Source: PAP